Ribociclib plus Endocrine Therapy in Early Breast Cancer

BACKGROUND

Ribociclib has been shown to have a significant overall survival benefit in patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer. Whether this benefit in advanced breast cancer extends to early breast cancer is unclear.

METHODS

In this international, open-label, randomized, phase 3 trial, we randomly assigned patients with HR-positive, HER2-negative early breast cancer in a 1:1 ratio to receive ribociclib (at a dose of 400 mg per day for 3 weeks, followed by 1 week off, for 3 years) plus a nonsteroidal aromatase inhibitor (NSAI; letrozole at a dose of 2.5 mg per day or anastrozole at a dose of 1 mg per day for ≥5 years) or an NSAI alone. Premenopausal women and men also received goserelin every 28 days. Eligible patients had anatomical stage II or III breast cancer. Here we report the results of a prespecified interim analysis of invasive disease-free survival, the primary end point; other efficacy and safety results are also reported. Invasive disease-free survival was evaluated with the use of the Kaplan-Meier method. The statistical comparison was made with the use of a stratified log-rank test, with a protocol-specified stopping boundary of a one-sided P-value threshold of 0.0128 for superior efficacy.

RESULTS

As of the data-cutoff date for this prespecified interim analysis (January 11, 2023), a total of 426 patients had had invasive disease, recurrence, or death. A significant invasive disease-free survival benefit was seen with ribociclib plus an NSAI as compared with an NSAI alone. At 3 years, invasive disease-free survival was 90.4% with ribociclib plus an NSAI and 87.1% with an NSAI alone (hazard ratio for invasive disease, recurrence, or death, 0.75; 95% confidence interval, 0.62 to 0.91; P = 0.003). Secondary end points - distant disease-free survival and recurrence-free survival - also favored ribociclib plus an NSAI. The 3-year regimen of ribociclib at a 400-mg starting dose plus an NSAI was not associated with any new safety signals.

CONCLUSIONS

Ribociclib plus an NSAI significantly improved invasive disease-free survival among patients with HR-positive, HER2-negative stage II or III early breast cancer. (Funded by Novartis; NATALEE ClinicalTrials.gov number, NCT03701334.).

Rationale and trial design of NATALEE: a Phase III trial of adjuvant ribociclib + endocrine therapy versus endocrine therapy alone in patients with HR+/HER2- early breast cancer

Background

Ribociclib has demonstrated a statistically significant overall survival benefit in pre- and postmenopausal patients with hormone receptor positive/human epidermal growth factor receptor 2 negative (HR+/HER2-) advanced breast cancer. New Adjuvant Trial with Ribociclib [LEE011] (NATALEE) is a trial evaluating the efficacy and safety of adjuvant ribociclib plus endocrine therapy (ET) versus ET alone in patients with HR+/HER2- early nonmetastatic breast cancer (EBC).

Methods/design

NATALEE is a multicenter, randomized, open-label, Phase III trial in patients with HR+/HER2- EBC. Eligible patients include women, regardless of menopausal status, and men aged ⩾18 years. Select patients with stage IIA, stage IIB, or stage III disease (per the anatomic classification in the AJCC Cancer Staging Manual, 8th edition) with an initial diagnosis ⩽18 months prior to randomization are eligible. Patients receiving standard (neo)adjuvant ET are eligible if treatment was initiated ⩽12 months before randomization. Patients undergo 1:1 randomization to ribociclib 400 mg/day (3 weeks on/1 week off) +ET (letrozole 2.5 mg/day or anastrozole 1 mg/day [investigator's discretion] plus goserelin [men or premenopausal women]) or ET alone. Ribociclib treatment duration is 36 months; ET treatment duration is ⩾60 months. The primary end point is invasive disease-free survival.

Discussion

The 36-month treatment duration of ribociclib in NATALEE is extended compared with that in other adjuvant cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitor trials and is intended to maximize efficacy due to longer duration of CDK4/6 inhibition. Compared with the 600-mg/day dose used in advanced breast cancer, the reduced ribociclib dose used in NATALEE may improve tolerability while maintaining efficacy. NATALEE includes the broadest population of patients with HR+/HER2- EBC of any Phase III trial currently evaluating adjuvant CDK4/6 inhibitor treatment.

Trial registration

ClinicalTrials.gov identifier: NCT03701334 (https://clinicaltrials.gov/ct2/show/NCT03701334).

Abstract OT2-03-02: lidERA Breast Cancer: A phase III adjuvant study of giredestrant (GDC-9545) vs physician’s choice of endocrine therapy in patients with estrogen receptor+, HER2– early breast cancer

BACKGROUND Endocrine therapies (ETs) that target estrogen receptor (ER) activity and/or estrogen synthesis are the mainstay of ER+ breast cancer (BC) treatment. Despite best management, ≤20% of patients (pts) with ER+/HER2– early BC (eBC) develop resistance (in some cases due to acquisition of tumor mutations in ESR1 that can drive estrogen-independent transcription and proliferation) and still have high recurrence rates on standard ETs. New treatment alternatives for ER+/HER2– eBC are needed to reduce risk of recurrence and improve survival, tolerability, quality of life, and adherence. Giredestrant, a highly potent, nonsteroidal oral selective ER antagonist and degrader (SERD), achieves robust ER occupancy and is active against tumors that retain ER-sensitivity or have ESR1 mutation(s). It has been demonstrated to be more potent in vitro and achieves higher ER occupancy in vivo than fulvestrant, the only currently approved SERD. Early-phase clinical studies have demonstrated that single-agent giredestrant (30 mg daily) has promising clinical and pharmacodynamic activity and is well tolerated in the ER+/HER2– eBC and metastatic BC settings. TRIAL DESIGN This is a phase III, global, randomized, open-label, multicenter study evaluating efficacy and safety of adjuvant giredestrant vs physician’s choice of adjuvant ET (PCET) in pts with medium- and high-risk stage I–III histologically confirmed ER+/HER2– eBC. Pts are randomized 1:1 to oral 30 mg daily giredestrant or PCET (tamoxifen, anastrozole, letrozole, or exemestane, given according to prescribing information). Stratification factors are risk (medium vs high, based on anatomic [tumor size, nodal status] and biologic features [grade, Ki67, gene signatures if available]); geographic region (US/Canada/Western Europe vs Asia-Pacific vs rest of the world); prior chemotherapy (no vs yes); and menopausal status (pre-/perimenopausal vs postmenopausal). Beginning on Day 1 of Cycle 1, pts will be treated with giredestrant or PCET for ≥5 years. Continuing PCET after 5 years is at discretion of the investigator and per local standard of care. ELIGIBILITY Female/male pts with medium-/high-risk stage I–III ER+/HER2– eBC; prior curative surgery; completion of (neo)adjuvant chemotherapy (if administered) and/or surgery < 12 months prior to enrollment; no prior ET (≤4 weeks of [neo]adjuvant ET is allowed). For men and pre-/perimenopausal women, a luteinizing hormone-releasing hormone agonist will be given per local prescribing information (mandatory for pts in the giredestrant arm). AIMS Primary endpoint: Invasive disease-free survival (IDFS). Secondary endpoints: Overall survival; IDFS (STEEP definition, including second non-primary BC); disease-free survival; distant recurrence-free survival; locoregional recurrence-free interval; safety; pharmacokinetics; pt-reported outcomes. In addition, this study aims to improve health equity in research and expand clinical trial access. The study will also use/develop digital healthcare solutions, which will enable better understanding of pts’ needs and their adherence to ET. STATISTICAL METHODS The primary endpoint analysis will use a stratified log-rank test at an overall 0.05 significance level (two-sided). An interim analysis and a futility analysis are planned, and an independent data monitoring committee will be in place. ACCRUAL 1018/4100 pts have been recruited globally. CONTACT INFORMATION For more information or to refer a patient, email global.rochegenentechtrials@roche.com or call 1-888-662-6728 (USA only). Clinicaltrials.gov number NCT04961996. AB, PS and CG contributed equally. This abstract was originally presented at SABCS 2021 (OT2-11-09).

a>Disclosure(s):

Peter Schmid, MD, PhD: Astellas Pharma: Contracted Research (Ongoing); AstraZeneca: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Honoraria (Ongoing); Bayer: Consulting Fees (e.g., advisory boards) (Ongoing), Honoraria (Ongoing); Boehringer Ingelheim: Consulting Fees (e.g., advisory boards) (Ongoing), Honoraria (Ongoing); Celgene: Consulting Fees (e.g., advisory boards) (Ongoing); Eisai: Consulting Fees (e.g., advisory boards) (Ongoing); F. Hoffmann-La Roche Ltd.: Third-party writing assistance for this abstract, furnished by Sunaina Indermun, BPharm, PhD, of Health Interactions, was provided by Roche (Ongoing); Genentech: Contracted Research (Ongoing); Medivation Inc.: Contracted Research (Ongoing); Merck: Consulting Fees (e.g., advisory boards) (Ongoing), Honoraria (Ongoing); Novartis: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Honoraria (Ongoing); OncoGenex: Contracted Research (Ongoing); Pfizer: Consulting Fees (e.g., advisory boards) (Ongoing), Honoraria (Ongoing); Puma Biotechnology: Consulting Fees (e.g., advisory boards) (Ongoing), Honoraria (Ongoing); Roche: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Honoraria (Ongoing)

Charles E. Geyer Jr, MD, FACP: Abbvie: Contracted Research (Terminated, July 1, 2022), Writing assistance (Terminated, July 1, 2022); AstraZeneca: Contracted Research (Ongoing), Writing assistance (Ongoing); Daiichi/Sankyo: Contracted Research (Ongoing); Exact Sciences: Consulting Fees (e.g., advisory boards) (Ongoing); F. Hoffman-La Roche Ltd: Contracted Research (Ongoing), Third-party writing assistance for this abstract, furnished by Sunaina Indermun, BPharm, PhD, of Health Interactions, was provided by Roche) (Ongoing); Genentech: Contracted Research (Ongoing), Writing assistance (Ongoing)

Nadia Harbeck, MD, PhD: Amgen: Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); AstraZeneca: Consulting Fees (e.g., advisory boards) (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Daiichi Sankyo: Consulting Fees (e.g., advisory boards) (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Eli Lilly: Consulting Fees (e.g., advisory boards) (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Exact Sciences: Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); MSD: Consulting Fees (e.g., advisory boards) (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Novartis: Consulting Fees (e.g., advisory boards) (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Pfizer: Consulting Fees (e.g., advisory boards) (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Pierre Fabre: Consulting Fees (e.g., advisory boards) (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Roche: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing), Third-party writing assistance for this abstract, furnished by Sunaina Indermun, BPharm, PhD, of Health Interactions, was provided by Roche (Ongoing); Sandoz: Consulting Fees (e.g., advisory boards) (Ongoing); Seagen: Consulting Fees (e.g., advisory boards) (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); WSG: Ownership Interest (stocks, stock options, patent or other intellectual property or other ownership interest excluding diversified mutual funds) (Ongoing)

Mothaffar Rimawi, MD: Daiichi Sankyo: Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); F. Hoffmann-La Roche Ltd.: Contracted Research (Ongoing), Third-party writing assistance for this abstract, furnished by Sunaina Indermun, BPharm, PhD, of Health Interactions, was provided by Roche (Ongoing); Genentech: Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Macrogenics: Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Pfizer: Contracted Research (Ongoing); Seattle Genetics: Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing)

Sara Hurvitz, MD, FACP: Ambrx: Contracted Research (Ongoing); Amgen: Contracted Research (Ongoing); Arvinas: Contracted Research (Ongoing); Astra Zeneca: Contracted Research (Ongoing); Bayer: Contracted Research (Ongoing); Cytomx: Contracted Research (Ongoing); Daiichi-Sankyo: Contracted Research (Ongoing); Dignitana: Contracted Research (Ongoing); Eli Lilly: Contracted Research (Ongoing); Genentech/Roche: Contracted Research (Ongoing); Gilead: Contracted Research (Ongoing); GSK: Contracted Research (Ongoing); Ideal Implant: Ownership Interest (stocks, stock options, patent or other intellectual property or other ownership interest excluding diversified mutual funds) (Ongoing); Immunomedics: Contracted Research (Ongoing); Macrogenics: Contracted Research (Ongoing); Novartis: Contracted Research (Ongoing); OBI Pharma: Contracted Research (Ongoing); Orinove: Contracted Research (Ongoing); Pfizer: Contracted Research (Ongoing); Phoenix Molecular Designs, Ltd.: Contracted Research (Ongoing); Pieris: Contracted Research (Ongoing); PUMA: Contracted Research (Ongoing); Radius: Contracted Research (Ongoing); Sanofi: Contracted Research (Ongoing); Seattle Genetics/Seagen: Contracted Research (Ongoing); Zymeworks: Contracted Research (Ongoing)

Miguel Martín, MD, PhD: AstraZeneca: Consulting Fees (e.g., advisory boards) (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Daiichi Sankyo: Consulting Fees (e.g., advisory boards) (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); F. Hoffmann-La Roche: Third-party writing assistance for this abstract, furnished by Eleanor Porteous, MSc, of Health Interactions, was provided by Roche (Ongoing); Genentech/Roche: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing), Third-party writing assistance for this abstract, furnished by Sunaina Indermun, BPharm, PhD, of Health Interactions, was provided by Roche (Ongoing); Gilead: Consulting Fees (e.g., advisory boards) (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Lilly/ImClone: Consulting Fees (e.g., advisory boards) (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing), Honoraria (Ongoing); Novartis: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing), Honoraria (Ongoing); Pfizer: Consulting Fees (e.g., advisory boards) (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing), Honoraria (Ongoing); Pierre Fabre: Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing), Honoraria (Ongoing); Seagen: Consulting Fees (e.g., advisory boards) (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing), Honoraria (Ongoing)

Sherene Loi, MBBS (Hons), PhD, FRACP, FAHMS, GAICD: Aduro Biotech, Inc.: Consulting Fees (e.g., advisory boards) (Ongoing); Akamara Therapeutics: Uncompensated scientific advisory board member (Ongoing); AstraZeneca: Consulting Fees (e.g., advisory boards) (Ongoing), Uncompensated consultant (Ongoing); BMS: Uncompensated consultant (Ongoing); Breast Cancer Research Foundation, New York: Supported by the Breast Cancer Research Foundation, New York (Ongoing); G1 Therapeutics: Consulting Fees (e.g., advisory boards) (Ongoing); GlaxoSmithKline: Consulting Fees (e.g., advisory boards) (Ongoing); Merck: Uncompensated consultant (Ongoing); National Breast Cancer Foundation of Australia Endowed Chair: Supported by the National Breast Cancer Foundation of Australia Endowed Chair (Ongoing); Novartis: Consulting Fees (e.g., advisory boards) (Ongoing), Uncompensated consultant (Ongoing); Roche-Genentech: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Third-party writing assistance for this abstract, furnished by Sunaina Indermun, BPharm, PhD, of Health Interactions, was provided by Roche (Ongoing), Uncompensated consultant (Ongoing); Seattle Genetics: Uncompensated consultant (Ongoing); Silverback Therapeutics: Consulting Fees (e.g., advisory boards) (Ongoing)

Shigehira Saji, MD, PhD: Astra Zeneca: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Bayer: Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Boerhringer-ingelheim: Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Breast International Group: Executive board member (Ongoing); Chugai: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Daiichi Sankyo: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Eisai: Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Eli Lilly: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); F. Hoffmann-La Roche Ltd.: Contracted Research (Ongoing), Third-party writing assistance for this abstract, furnished by Sunaina Indermun, BPharm, PhD, of Health Interactions, was provided by Roche (Ongoing); Japan Breast Cancer Research Group: Executive board member (Ongoing); Japanese Breast Cancer Society: Executive board member (Ongoing); Japanese Society of Medical Oncology: Executive board member (Ongoing); Kyowa Kirin: Consulting Fees (e.g., advisory boards) (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); MSD: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Nihonkayaku: Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Novartis: Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Ono: Consulting Fees (e.g., advisory boards) (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Pfizer: Consulting Fees (e.g., advisory boards) (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Taiho: Contracted Research (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); Takeda: Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing)

Kyung Hae Jung, MD, MS, PhD: AstraZeneca: Consulting Fees (e.g., advisory boards) (Ongoing); Celgene: Consulting Fees (e.g., advisory boards) (Ongoing); Daiichi-Sankyo: Consulting Fees (e.g., advisory boards) (Ongoing); Eisai: Consulting Fees (e.g., advisory boards) (Ongoing); Everest Medicine: Consulting Fees (e.g., advisory boards) (Ongoing); Merck: Consulting Fees (e.g., advisory boards) (Ongoing); MSD: Consulting Fees (e.g., advisory boards) (Ongoing); Novartis: Consulting Fees (e.g., advisory boards) (Ongoing); Pfizer: Consulting Fees (e.g., advisory boards) (Ongoing); Roche: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Third-party writing assistance for this abstract, furnished by Sunaina Indermun, BPharm, PhD, of Health Interactions, was provided by Roche (Ongoing); Takeda: Consulting Fees (e.g., advisory boards) (Ongoing)

Gustavo Werutsky, MD, PhD: AstraZeneca: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Honoraria (Ongoing); Bayer: Contracted Research (Ongoing); Beigene: Contracted Research (Ongoing); Daiichi Sankyo: Consulting Fees (e.g., advisory boards) (Ongoing); Genentech/Roche: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Fees for Non-CME Services Received Directly from Commercial Interest or their Agents (e.g., speakers’ bureaus) (Ongoing); GSK: Contracted Research (Ongoing); Lilly: Contracted Research (Ongoing), Honoraria (Ongoing); MSD: Honoraria (Ongoing); Novartis: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Honoraria (Ongoing); Pfizer: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Honoraria (Ongoing); Sanofi: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing); Seattle Genetics: Contracted Research (Ongoing)

Daniil L. Stroyakovsky, MD: Roche: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing), Third-party writing assistance for this abstract, furnished by Sunaina Indermun, BPharm, PhD, of Health Interactions, was provided by Roche (Ongoing)

Vanesa López-Valverde, PharmD, PhD: F. Hoffmann-La Roche Ltd.: Ownership Interest (stocks, stock options, patent or other intellectual property or other ownership interest excluding diversified mutual funds) (Ongoing), Salary (Ongoing), Third-party writing assistance for this abstract, furnished by Sunaina Indermun, BPharm, PhD, of Health Interactions, was provided by Roche (Ongoing)

Michael Davis, PsyD: F. Hoffmann-La Roche Ltd.: Ownership Interest (stocks, stock options, patent or other intellectual property or other ownership interest excluding diversified mutual funds) (Ongoing), Third-party writing assistance for this abstract, furnished by Sunaina Indermun, BPharm, PhD, of Health Interactions, was provided by Roche (Ongoing); Genentech, Inc.: Salary (Ongoing)

Tanja Badovinac Crnjevic, MD, PhD: F. Hoffmann-La Roche Ltd.: Ownership Interest (stocks, stock options, patent or other intellectual property or other ownership interest excluding diversified mutual funds) (Ongoing), Salary (Ongoing), Third-party writing assistance for this abstract, furnished by Sunaina Indermun, BPharm, PhD, of Health Interactions, was provided by Roche (Ongoing)

Pablo D. Perez-Moreno, MD: F. Hoffmann-La Roche Ltd.: Ownership Interest (stocks, stock options, patent or other intellectual property or other ownership interest excluding diversified mutual funds) (Ongoing), Third-party writing assistance for this abstract, furnished by Sunaina Indermun, BPharm, PhD, of Health Interactions, was provided by Roche (Ongoing); Genentech, Inc.: Salary (Ongoing)

Aditya Bardia, MD, MPH: AstraZeneca: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing); BioTheranostics: Consulting Fees (e.g., advisory boards) (Ongoing); Daiichi Sankyo: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing); Eli Lilly: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing); Foundation Medicine: Consulting Fees (e.g., advisory boards) (Ongoing); Genentech/Roche: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing); Immunomedics/Gilead: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing); Merck: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing); Novartis: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing); Pfizer: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing); Phillips: Consulting Fees (e.g., advisory boards) (Ongoing); Radius Health: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing); Sanofi: Consulting Fees (e.g., advisory boards) (Ongoing), Contracted Research (Ongoing)

</a>

Citation Format: Peter Schmid, Charles E. Geyer Jr, Nadia Harbeck, Mothaffar Rimawi, Sara Hurvitz, Miguel Martín, Sherene Loi, Shigehira Saji, Kyung Hae Jung, Gustavo Werutsky, Daniil L. Stroyakovsky, Vanesa López-Valverde, Michael Davis, Tanja Badovinac Crnjevic, Pablo D. Perez-Moreno, Aditya Bardia. lidERA Breast Cancer: A phase III adjuvant study of giredestrant (GDC-9545) vs physician’s choice of endocrine therapy in patients with estrogen receptor+, HER2– early breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT2-03-02.

Abstract P3-06-03: Trilaciclib induces immune changes within the tumor microenvironment in early-stage triple-negative breast cancer

Background: In early-stage triple-negative breast cancer (TNBC), there is accumulating evidence of a correlation between tumor-infiltrating lymphocytes in tumor tissue and favorable clinical outcomes, with a high CD8+/regulatory T-cell (Treg) ratio after neoadjuvant chemotherapy being predictive of overall survival and associated with pathologic complete response (Ladoire S, et al. Br J Cancer. 2011; Park YH, et al. Nat Commun. 2020). Trilaciclib is a transient inhibitor of cyclin-dependent kinase 4/6 that is administered intravenously prior to chemotherapy. In preclinical studies, trilaciclib has been shown to have immune-enhancing effects by differentially arresting CD8+ T-cell and Treg subsets, which is followed by the faster recovery of CD8+ T cells than Tregs in the tumor microenvironment. Methods: This phase 2, single-arm, open-label study aims to evaluate neoadjuvant, single-dose trilaciclib followed by trilaciclib plus dose-dense anthracycline/cyclophosphamide and taxane in patients with early-stage TNBC (NCT05112536). Patients with previously untreated, non-metastatic, confirmed TNBC and a primary tumor ≥ 1.5 cm of any nodal status receive a single dose of trilaciclib 240 mg/m2 during the lead-in phase, followed by 4 cycles of doxorubicin 60 mg/m2 plus cyclophosphamide 600 mg/m2, and 12 weekly cycles of paclitaxel 80 mg/m2. Trilaciclib 240 mg/m2 is administered prior to the first chemotherapy dose of each cycle. Pembrolizumab 400 mg every 6 weeks starting on day 1, cycle 1, and/or carboplatin AUC 1.5 every week starting on day 1, cycle 5, is allowed per investigator discretion. Tumor biopsies and peripheral blood samples are collected prior to any treatment, 7 days ± 1 day post administration of trilaciclib, and during surgery, with an additional blood sample collection on day 1, cycle 2. The primary objective is to evaluate the immune-based mechanism of action of trilaciclib after a single dose of trilaciclib, as measured by changes in the CD8+/Treg ratio in tumor tissue. Pathologic complete response, safety and tolerability, and additional exploratory immune biomarker endpoints will also be assessed. Results: As of June 3, 2022, 9 patients with early-stage TNBC had been enrolled and 8 patients had received the trilaciclib lead-in dose and initiated doxorubicin/cyclophosphamide. Patients had a median age of 53.0 years, and all had stage II tumors at diagnosis, with 7 having ductal carcinoma. The median number of chemotherapy cycles received was 3 (range 1–6), and all 8 patients received pembrolizumab. Seven patients continue study treatment; 1 patient discontinued due to disease progression. Five patients had an adverse event (AE) related to any study treatment, including 4 patients with ≥ 1 trilaciclib-related AE. There were no grade ≥ 3 treatment-related AEs or serious AEs. On-treatment, post-trilaciclib monotherapy biopsies were available for 4 patients. Following neoadjuvant trilaciclib treatment, the median density of stromal CD8+ T cells increased from 103.1/mm2 at baseline to 229.8/mm2 at day 7. The median CD8+/Treg ratio increased in 2 patients from 1.85 at baseline to 1.90 at day 7. Conclusions: Preliminary analysis of on-treatment tumor biopsies from 4 patients suggests that a single dose of trilaciclib may modulate the immune cell composition in the tumor microenvironment to support antitumor immune responses. The increase in CD8+ T cells following 7-day neoadjuvant treatment with trilaciclib supports previous data suggesting a role in T-cell infiltration. The complete dataset from all patients (estimated enrollment: N ≈ 24) and additional biomarker analyses will be presented.

Citation Format: Michael Danso, Joyce O’Shaughnessy, Lisa S. Wang, Kailash Mosalpuria, Sara Hurvitz, Shom Goel, Sarah Ahn, Subing Cao, John S. Yi, Taofik Oyekunle, Amanda Jacobson, Andrew Beelen, Jeremy Force. Trilaciclib induces immune changes within the tumor microenvironment in early-stage triple-negative breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-06-03.

Abstract GS2-03: GS2-03 TRIO-US B-12 TALENT: Neoadjuvant trastuzumab deruxtecan with or without anastrozole for HER2-low, HR+ early stage breast cancer

Background: Although patients (pts) with hormone receptor-positive (HR+)/HER2-negative breast cancer (BC) frequently experience disease response to neoadjuvant therapy, fewer than 10% achieve a pathologic complete response (pCR) with standard chemotherapy or endocrine therapy, even in combination with CDK4/6 inhibitors. Thus, finding more effective therapies for this disease remains an unmet need. HER2 is expressed at a low level (IHC 1+ or 2+) in approximately 60-70% of HR+ BC. Trastuzumab deruxtecan (DS-8201a, T-DXd) is a novel HER2-targeting antibody drug conjugate (ADC) that is FDA approved in the US for HER2-positive and HER2-low metastatic BC (with boxed warnings for interstitial lung disease). However, the efficacy of T-DXd in the neoadjuvant setting is not known. The primary objective of TALENT (TRIO-US B-12, NCT04553770) is to evaluate the clinical activity and safety of neoadjuvant T-DXd alone or in combination with endocrine therapy in pts with HR+/HER2-low early BC.

Methods: Men and women with previously untreated, operable invasive early stage, non-recurrent, HR+, HER2-low (IHC 1+ or 2+/ISH- by local or central review) BC measuring > 2 cm were eligible. In stage 1 of clinical trial, participants were randomized 1:1 to receive T-DXd (5.4 mg/kg IV q21 days) alone, Arm A, or in combination with anastrozole AI (1 mg PO QD), Arm B. Originally 6 cycles (cy) were given but in 02/2022, an amendment increased the number of treatment cy from 6 to 8 for newly enrolled pts, or those who had not yet had surgery. Men and pre/peri-menopausal women randomized to Arm B also received a GnRH agonist. Stratification factors were HER2 expression (1+ vs. 2+) and menopausal status (men as postmenopausal). Tumor tissue collected at baseline, cy 1 day 17-21, and at surgery. Breast imaging performed at baseline, cy 2 and pre-surgery/EOT. Primary endpoint is pCR rate (ypT0/is ypN0) at surgery. In stage 1, intent was to randomize 58 pts (if at least 2 pCR occurred in an arm, arm progresses to Stage 2 and an additional 15 pts to be enrolled). Other endpoints include safety, objective response rate (ORR), changes in Ki67 expression, Residual Cancer Burden index, exploratory biomarker analysis, and health-related quality of life. Here we present results from stage 1 of the trial.

Results: From 09/21/2020 to 10/13/2022, 58 pts were enrolled and treated (29 Arm A, 29 Arm B) in stage 1 of trial. Five pts came off study before completing study therapy (2 after cy 1, 2 after cy 2, 1 after cy 3). As of data cut-off (10/05/2022), 33 pts completed study treatment and have had surgery (17 Arm A, 16 Arm B), 13 are on treatment and 7 are pending surgery; 27 pts completed 6 cy and 13 completed 8 cy. Baseline characteristics were balanced between arms. 19/58 pts were Stage IIA, 26/58 Stage IIB, 12/58 Stage IIIA, and 1/58 Stage IIIB at baseline. 46/58 pts had baseline HER2 expression (from central review) of 1+, 4/58 were 0, 6/58 were 2+, 1/58 had multicentric lesion 1+ and 2+, and 1/58 had a single lesion with 1+ and 2+. In Arm A, 1/17 pt had pCR after 8 cy, 2/17 pts had RCB-I after 6 cy (17.6% RCB 0/1). In Arm B, 1/16 pt had RCB-I after 8 cy (6.3%). The ORR for response-evaluable pts in Arm A was 75% (12/16, 1 CR, 11 PR) and in Arm B was 63.2% (12/19, 2 CR, 10 PR); 1 patient (Arm B) had PD. ILD occurred in 1 pt (1.7%), Gr 2 and resolved 11 days after stopping therapy. Most common treatment-related Grade ≥ 3 AEs in Arms A and B, respectively, include hypokalemia (1.7%, 5.2%), diarrhea (3.4%, 3.4%), neutropenia (3.4%, 1.7%), fatigue (1.7%, 3.4%), headache (3.4%, 1.7%), vomiting (3.4%, 1.7%), dehydration (1.7%, 1.7%) and nausea (3.4%, 0%).

Conclusions: This is the first report of a trial evaluating neoadjuvant T-DXd in HER2 low breast cancer. T-DXd +/- endocrine therapy demonstrates promising clinical activity for pts with HR+ BC. Updated study results will be provided at the time of presentation.

Citation Format: Aditya Bardia, Sara Hurvitz, Michael F. Press, Lisa S. Wang, Nicholas P. McAndrew, David Chan, Vu Phan, Deborah Villa, Merry L. Tetef, Erin Chamberlain, Nihal Abdulla, Thomas Lomis, Laura M. Spring, Steven Applebaum, Shaker Dakhil, Brian DiCarlo, David D. Kim, Evangelia Kirimis, William E. Lawler, Aashini K. Master, Kelly McCann, Edwin Hayashi, Christine Kivork, James Chauv. GS2-03 TRIO-US B-12 TALENT: Neoadjuvant trastuzumab deruxtecan with or without anastrozole for HER2-low, HR+ early stage breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr GS2-03.

Abstract GS3-03: GS3-03 ARV-471, a PROTAC® estrogen receptor (ER) degrader in advanced ER-positive/human epidermal growth factor receptor 2 (HER2)-negative breast cancer: phase 2 expansion (VERITAC) of a phase 1/2 study

Background: ARV-471 is a selective, orally administered PROteolysis TArgeting Chimera (PROTAC®) protein degrader that targets wild-type and mutant ER. ARV-471 is being evaluated in patients with ER+/HER2- locally advanced or metastatic breast cancer in a first-in-human phase 1/2 study (NCT04072952). In the phase 1 dose escalation, ARV-471 monotherapy (dose range: 30–700 mg total daily dose) showed a manageable safety profile in patients who had previously received endocrine therapy and a cyclin-dependent kinase (CDK) 4/6 inhibitor. The clinical benefit rate (CBR; rate of confirmed complete or partial response or stable disease ≥24 weeks) was 40% (95% CI: 26–56) in 47 evaluable patients. The phase 2 expansion portion of the study (VERITAC) evaluated 2 doses of ARV-471.Methods: In VERITAC, ARV-471 monotherapy was administered at doses of 200 mg once daily (QD) or 500 mg QD to patients with ER+/HER2- locally advanced/metastatic breast cancer who had received ≥1 prior endocrine therapy for ≥6 months, ≥1 CDK4/6 inhibitor, and ≤1 chemotherapy regimen. The primary endpoint of CBR was evaluated in patients enrolled ≥24 weeks prior to the data cutoff. Results: As of June 6, 2022, 71 patients received ARV-471 (200 mg QD [n=35]; 500 mg QD [n=36]) in VERITAC. Across all treated patients, 69 (97.2%) were female and median age was 60 y (range: 41–86). Patients had received a median of 4 prior regimens in all settings (range: 1–10); 100% had prior CDK4/6 inhibitors, 78.9% had prior fulvestrant, and 73.2% had prior chemotherapy. ARV-471 was well tolerated at both doses, with most treatment-related adverse events (TRAEs) grade 1/2; the most common TRAEs were fatigue and nausea (Table). In all, 3 patients (1 in the 200 mg QD cohort and 2 in the 500 mg QD cohort) discontinued ARV-471 due to treatment-emergent adverse events (TEAEs); 3 patients had ARV-471 dose reductions due to TEAEs (all from 500 mg QD to 400 mg QD). CBR was 37.1% (95% CI: 21–55) in 35 evaluable patients treated at 200 mg QD and 38.9% (95% CI: 23–57) in 36 evaluable patients treated at 500 mg QD. CBR in evaluable patients with mutant ESR1 in the 200 mg QD (n=19) and 500 mg QD (n=22) cohorts was 47.4% (95% CI: 24–71) and 54.5% (95% CI: 32–76), respectively. Conclusions: In the phase 2 VERITAC expansion cohorts of patients with ER+/HER2- locally advanced/metastatic breast cancer and prior CDK4/6 inhibitor treatment, ARV-471 monotherapy showed evidence of clinical activity based on CBR, which was further enhanced in the subgroup with ESR1 mutations. The manageable AE profile observed in the phase 1 portion of the study was maintained during cohort expansion at doses of 200 mg QD and 500 mg QD. Additional analyses are ongoing.Table. TRAEs reported in ≥10% of patients overall aNo grade 3/4 TRAE occurred in >1 patient. AST=aspartate aminotransferase

Citation Format: Anne F. Schott, Sara Hurvitz, Cynthia Ma, Erika Hamilton, Rita Nanda, George Zahrah, Natasha Hunter, Antoinette R. Tan, Melinda Telli, Jesus Anampa Mesias, Rinath Jeselsohn, Pamela Munster, Haolan Lu, Richard Gedrich, Cecile Mather, Janaki Parameswaran, Hyo S. Han. GS3-03 ARV-471, a PROTAC® estrogen receptor (ER) degrader in advanced ER-positive/human epidermal growth factor receptor 2 (HER2)-negative breast cancer: phase 2 expansion (VERITAC) of a phase 1/2 study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr GS3-03.

Abstract P4-01-16: High levels of RSK2 in breast cancer patients is associated with longer PFS in patients treated with PMD-026, a first in class RSK inhibitor

Background: Breast cancer (BC) is the most common malignancy in women and metastatic triple negative breast cancer (mTNBC) remains one of the most difficult to treat cancers with few targeted treatment options. RSK is recognized as a critical signaling component in the MAPK/PDK-1 pathways, is an important driver for BC and a signature of poor prognosis. PMD-026 is the first RSK inhibitor to enter clinical trials and is being developed alongside an immunohistochemistry (IHC) companion diagnostic to select patients with increased activated RSK2 in tumor tissue. A Phase 1/1b trial of PMD-026 in patients with metastatic breast cancer (mBC) or metastatic triple negative breast cancer (mTNBC) established safety at a dose of 200 mg Q12h. Efficacy signals in patients with heavily pretreated mBC/mTNBC are explored in this analysis along with evaluation of the effect of food (FE) on systemic exposure to treatment. Methods: PMD-026 was administered to 41 patients as a single agent in this phase 1/1b open-label study, with 30 patients evaluable for efficacy. Exploratory objectives were to identify subgroups of patients who may optimally benefit from PMD-026. Subgroup analysis of patients included 1) comparing BC patients who received ≤5 vs >5 prior therapies; 2) comparing TNBC patients (de novo vs secondary subtypes)1, and 3) comparing patients with low RSK2 H-scores (< 180) vs high (≥180). In addition, PMD 026 PK was evaluated at the 200 mg Q12h dose and a FE sub-study enrolled 12 patients administered a single 200 mg dose. Results: PMD-026 monotherapy was generally well-tolerated in the 41 mBC patients who were enrolled and treated. Kaplan-Meier PFS analysis of 30 evaluable BC patients who were dosed with PMD-026 showed that patients with less prior therapy (≤5) did significantly better (HR, 0.19; 95% CI [0.06–0.52], p=0.0014) than those with > 5 prior therapies. Subgroup analysis of PFS in those with TNBC demonstrated that de novo TNBC (n=17) had longer time on treatment with PMD-026 compared with secondary TNBC (n=9) (HR, 0.31; 95% CI [0.10-0.99], p=0.0476). In those with de novo TNBC with ≤5 prior therapies, a high RSK2 H-score was associated with significantly longer PFS at the RP2D (4.2 vs 1.3 months, HR, 0.17; 95% CI [0.03-0.80], p=0.0254) than patients with a low RSK2 H-score. In patients with CDK4/6 resistant HR+ BC (n=3), PFS was 5.2 (RSK2 high) vs 1.3 months (RSK2 low). Stable disease was observed in 53% (9/17) of patients with de novo TNBC and in 67% (6/9) of de novo TNBC patients with high RSK2. Tumor necrosis or target lesion reduction (< 30%) was observed in 17% of patients (5/30), all of whom had high RSK2 expression. In the FE sub-study, increased interpatient variability in PMD-026 Cmax and Tmax but not AUC, was observed when administered with food, favored dosing in a fasted state, which is consistent with the pH dependent solubility of PMD-026. Notably, all FE patients (12/12) achieved the target concentration of 1µM (IC90 in preclinical studies) within 4 hours when PMD-026 was taken without food. At the RP2D, PMD-026 taken without food showed relatively consistent exposure among patients over 24 hr timeframe. Conclusions: These findings demonstrate that in patients treated with PMD-026 who had received < 5 prior treatment regimens, had de novo TNBC or CDK4/6 refractory HR+ disease and had high RSK2 scores had longer PFS. Overall, PMD-026 is a well-tolerated, orally available RSK2 inhibitor that will be evaluated further for efficacy in TNBC and CDK4/6i refractory HR+ mBC, in a trial that will prospectively enroll patients based on RSK2 activation as defined by the RSK2 IHC H-scores. Clinical trial information: NCT04115306. 1 Patients diagnosed and treated for TNBC from their initial diagnosis (de novo TNBC) vs patients previously treated for hormone receptor positive (HR+) or human epidermal growth factor 2 receptor positive (HER2+) BC, but became HR or HER2 negative (secondary TNBC)

Citation Format: Judy S. Wang, Muralidhar Beeram, Pavani Chalasani, Lida Mina, Rebecca A. Shatsky, Sara Hurvitz, Meghna S. Trivedi, Robert Wesolowski, Hyo S. Han, Amita Patnaik, Shakeela Bahadur, My-my Huynh, Aarthi Jayanthan, Gerrit Los, Sandra E. Dunn, Andrew Dorr. High levels of RSK2 in breast cancer patients is associated with longer PFS in patients treated with PMD-026, a first in class RSK inhibitor [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-01-16.

Abstract OT2-01-04: ELONA: An open-label, phase 1b-2 study of elacestrant, in combination with onapristone in patients with estrogen receptor-positive, progesterone receptor-positive, HER2-negative advanced or metastatic breast cancer

Objectives: The addition of a CDK 4/6 inhibitors to endocrine therapy, in the first or second line setting, provides a significant improvement in progression free survival (PFS), and in some cases in overall survival (OS), with a tolerable toxicity profile. Regardless, most patients experience disease progression on these agents and ultimately develop endocrine resistance, thus, emphasizing the critical need for novel treatments. Elacestrant showed a statistically significant improvement in PFS when compared to standard of care endocrine therapy after progression on CDK4/6 inhibitors in combination with endocrine therapy (Bidard et al, 2022). Onapristone is a type I antiprogestin which prevents the progesterone receptor (PgR) from dimerizing and blocks ligand-induced protein kinase-mediated phosphorylation of the PgR. The clinical anticancer activity of onapristone, in immediate release formulation, has been previously documented in patients with hormone therapy-naïve (Robertson et al, 1999) or tamoxifen-resistant (Jonat et al, 2002) breast cancer (BC). More recently, onapristone, in extended release formulation, was evaluated in doses up to 50 mg BID in a phase 1 trial that enrolled 52 heavily pretreated patients with metastatic solid tumors, with no dose limiting toxicity observed. Among the 20 breast cancer patients enrolled, 7 (35%) had stable disease (Cottou et al, 2018). Methods: ELONA is a phase 1b/2, open-label, multicenter study. The phase 1b portion of the study will assess the safety, pharmacokinetics (PK), pharmacodynamics, and preliminary efficacy of elacestrant plus onapristone to determine the combinations’ recommended phase 2 dose. The primary endpoint of the phase 2 part of the trial is objective response rate and secondary endpoints will include safety, duration of response, clinical benefit rate, PFS, and OS, in addition to pharmacodynamics markers using ctDNA. Eligible patients are pre-, peri- and post-menopausal women and men aged ≥18 years with ER+/PgR+,HER2- tumors and an Eastern Cooperative Oncology Group performance status ≤2 with at least one measurable lesion at baseline, as per RECIST version 1.1. Prior therapy in the metastatic setting includes at least one anti-hormonal therapy in combination with a CDK4/6i. No prior chemotherapy regimen in the metastatic setting is allowed. The phase 1b dose-escalation portion of the study will evaluate dose-limiting toxicities (DLTs) of the combination in up to 4 cohorts of 6 patients each.

Citation Format: Erika Hamilton, Lajos Pusztai, Hatem H. Soliman, Sara Hurvitz, Krzysztof Grzegorzewski, Nassir Habboubi, Priya Marreddy, Tarek Sahmoud, Nuhad Ibrahim. ELONA: An open-label, phase 1b-2 study of elacestrant, in combination with onapristone in patients with estrogen receptor-positive, progesterone receptor-positive, HER2-negative advanced or metastatic breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT2-01-04.

Abstract P4-01-15: Preliminary results from a phase 2 study of praluzatamab ravtansine (CX-2009) in patients with advanced breast cancer (ABC)

Background: CD166 is broadly expressed in normal epithelium and overexpressed in many types of malignancies, including breast cancer. Probody® therapeutic candidates are masked antibodies, conditionally activated by tumor-associated proteases, which restricts their activity to the tumor microenvironment and minimizes ‘off-tumor’ toxicity. CX-2009 is a conditionally activated humanized anti-CD166 monoclonal antibody conjugated to DM4 that showed clinical activity in ABC patients in a phase 1 study (Boni et al. Clin Cancer Res. 2022). This phase 2 study (NCT04596150) evaluates CX-2009 as monotherapy in patients with advanced HR+/HER2− BC (Arm A) and TNBC (Arm B), and in combination with pacmilimab (a conditionally activated PD-L1) in TNBC (Arm C). Methods: Key eligibility criteria for all cohorts include: ECOG 0-1, acceptable end-organ function, measurable disease, willingness to receive ocular prophylaxis for DM-4 related toxicity, and available tumor tissue for CD166 evaluation. Eligibility criteria for HR+ BC include: 2-4 prior regimens (excluding single-agent hormonal therapy with up to 2 prior cytotoxic regimens) and a prior CDK 4/6 inhibitor in the metastatic setting; eligibility criteria for TNBC include CD166 by IHC >1% by central assessment, 1-3 prior regimens in the metastatic setting and prior taxane. All patients initially received 7 mg/kg Q3W; the protocol was subsequently amended to enroll patients at 6 mg/kg Q3W. The primary endpoint was overall response rate (ORR) using RECIST v1.1 assessed by central review. Other key endpoints include ORR by investigator assessment, clinical benefit rate at 24 weeks (CBR24; defined as any response, confirmed or unconfirmed, or SD for 24 weeks), duration of response, and progression-free survival by investigator. Archival tumor specimens and blood samples were collected for correlative research including genomic analyses. Results: As of 13 May 2022, 60 patients were enrolled in Arm A (all patients started at 7 mg/kg); 52 were evaluable for efficacy by investigator. Median duration of follow-up was 29.1 weeks (range: 3.6-60.7). Median age was 60.5 years (36, 83); pts received a median of 3.5 (1, 6) prior treatments for ABC. CD166 H-Score > 200 was reported in 53.3% of patients. Arm A met the primary efficacy endpoint with a confirmed ORR by central radiology of 14.9% (n=47); by investigator, ORR was similar at 15.4% (n=52); an additional 9 patients (17.3%) had an unconfirmed response. CBR24 was 40.4%; using only confirmed responses, CBR24 was 23.1%. Median PFS was 11.4 weeks (95% CI 9.0, 13.9). Common treatment-related all-grade adverse events (TRAEs) included blurred vision (42%), nausea (35%), fatigue (35%), diarrhea (25%), peripheral neuropathy (27%), infusion-related reaction (23%) and decreased appetite (20%). Grade ≥3 ocular and neuropathic TRAEs were 15% and 10%, respectively. AEs resulting in treatment discontinuation (AEDC) were 25%. For Arm B and C, 55 and 10 patients were enrolled (the majority received a starting dose of 6 mg/kg). For Arm B, the futility boundary was crossed (ORR < 10%). Grade ≥3 ocular and neuropathic TRAEs and AEDC at 7 mg/kg in Arm B were similar to Arm A (11%, 11% and 21% respectively); whereas at 6 mg/kg, they were reduced at 3%, 0% and 0%, respectively. Biomarker data and correlation with outcomes will be presented. Conclusions: Praluzatamab ravtansine demonstrated single-agent activity in unselected heavily pretreated patients with HR+/HER2- ABC. Time to event analyses, such as PFS, were confounded by higher-than-expected toxicity at a starting dose of 7 mg/kg. The toxicity profile was generally consistent with a DM4 payload. The lower dose of 6 mg/kg appears to be better tolerated. Additional clinical studies in HR+ABC, incorporating a starting dose of 6 mg/kg and potentially including a biomarker strategy, are warranted.

Citation Format: Kathy Miller, Sara Tolaney, Leisha A. Emens, Sung-Bae Kim, Erika Hamilton, Cristina Saura, Lucia Sanz, Valentina Boni, Filipa Lynce, Juan Miguel Cejalvo, Jennifer Crozier, Shirley Wang, Hirdesh Uppal, Alison L. Hannah, Sara Hurvitz. Preliminary results from a phase 2 study of praluzatamab ravtansine (CX-2009) in patients with advanced breast cancer (ABC) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-01-15.

Abstract OT2-01-03: ELEVATE: A phase 1b/2, open-label, umbrella study evaluating elacestrant in various combinations in women and men with metastatic breast cancer (mBC)

Background: Elacestrant demonstrated significantly prolonged progression-free survival (PFS) and a manageable safety profile compared with standard of care endocrine therapy in the phase 3 EMERALD trial that enrolled patients with estrogen-receptor positive (ER+)/HER2− mBC following disease progression on prior endocrine and cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) therapy. Benefit was observed in the overall population and in patients with ESR1 mutations. Combining elacestrant with targeted agents utilized in combination with endocrine therapy in mBC is of therapeutic interest. Methods: ELEVATE is a phase 1b/2 trial designed to evaluate the combination of elacestrant with alpelisib, everolimus, palbociclib, abemaciclib, or ribociclib. Eligible patients (pts) are women or men with ER+/HER2− locally advanced or mBC, measurable disease per RECIST v1.1 or ≥1 lytic or mainly lytic bone lesion, ECOG PS ≤1, no inflammatory breast cancer or uncontrolled central nervous system metastases, in addition to treatment-arm specific eligibility criteria as detailed below. In the phase 1b portion, pts who have received prior aromatase inhibitor (AI) and CDK4/6i will be enrolled in three 6-patient cohorts for each combination except abemaciclib (under study in a separate trial). Patients will receive elacestrant with the targeted agent at reduced or full doses. The primary endpoint of phase 1b is to determine the recommended phase 2 dose for each combination. Secondary endpoints are safety, pharmacokinetics, pharmacodynamics, and efficacy (objective response rate [ORR], duration of response [DoR], clinical benefit rate [CBR], PFS, and overall survival [OS]). The phase 2 portion will enroll 5 separate arms: A) pts with PIK3CA mutation(s) and prior AI + CDK4/6i: alpelisib + elacestrant, n=50; B) pts with prior AI + CDK4/6i: everolimus + elacestrant, n=50; C) pts with prior AI + CDK4/6i: abemaciclib or ribociclib (investigator’s [inv] choice) + elacestrant, n=60 (30 per combination); D) pts with prior AI only (no CDK4/6i): palbociclib, abemaciclib or ribociclib (inv choice) + elacestrant, n=90 (n=30 per combination); E) pts with no prior systemic therapy: palbociclib or ribociclib (inv choice) + elacestrant, n=90 (n=45 per combination). No prior fulvestrant or chemotherapy is allowed in any arm and no more than 2 prior hormonal therapies are permitted in arms A-D. Prior therapy restrictions apply to the mBC setting or within 12 months of adjuvant therapy. The primary endpoint for the phase 2 portion is the estimation of PFS at 6 months in arms A, B, and C and at 12 months in arms D and E. Secondary endpoints will include ORR, DoR, CBR, PFS, OS, and safety. The Kaplan-Meier method will be used to estimate PFS. Descriptive statistics will be used to evaluate response and safety.

Citation Format: Hope Rugo, Aditya Bardia, Javier Cortés, Giuseppe Curigliano, Erika Hamilton, Sara Hurvitz, Sibylle Loibl, Simona Scartoni, Tarek Sahmoud, Krzysztof Grzegorzewski, Nassir Habboubi, Joyce O’Shaughnessy. ELEVATE: A phase 1b/2, open-label, umbrella study evaluating elacestrant in various combinations in women and men with metastatic breast cancer (mBC). [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT2-01-03.

Abstract PD18-10: Treatment of HER2-positive (HER2+) hormone-receptor positive (HR+) metastatic breast cancer (mBC) with the novel combination of zanidatamab, palbociclib, and fulvestrant

Background: HER2+ mBC remains incurable, with a need for new HER2-directed therapies and regimens, including chemotherapy-free options. Zanidatamab (zani) is a novel HER2-targeted bispecific antibody that binds HER2 in a unique trans configuration, driving multiple mechanisms of antitumor activity, including complement-dependent cytotoxicity. A CDK4/6 inhibitor combined with endocrine therapy is an approved treatment for HER2-negative/HR+ mBC and this combination has also demonstrated encouraging antitumor activity when paired with HER2-targeted therapy(ies) in HER2+/HR+ mBC. Here, we report results from ZWI-ZW25-202 (NCT04224272), an ongoing single-arm phase 2 study of zani combined with palbociclib (palbo) and fulvestrant (fulv) in pts with HER2+/HR+ mBC. Methods: Eligibility requirements include: HER2+/HR+ unresectable, locally advanced BC or mBC; ECOG PS of 0 or 1; prior treatment with trastuzumab, pertuzumab and T DM1 (additional prior HER2-targeting agents are permitted); and no prior treatment with CDK4/6 inhibitors. Part 1 of the study evaluated the safety and tolerability of the zani/palbo/fulv combination and determined the recommended doses for use in Part 2, where the antitumor activity of the combination is being evaluated. Endpoints include safety outcomes, progression-free survival at 6 months (PFS6), confirmed objective response rate (cORR) per RECIST v1.1; disease control rate (DCR=complete response [CR] plus partial response [PR] plus stable disease [SD]); duration of response (DOR); PFS; and overall survival. Results: As of 24 Feb 2022, 34 pts (33 HER2+/HR+ per central analysis) with a median age of 52 (range 36-77) have been treated. In the metastatic setting, pts had received a median (range) of 4 (1-10) prior systemic regimens, including 3 (1-8) different prior HER2 targeted therapies, and 1 (0-4) endocrine therapy. Seven pts (20%) had prior T DXd treatment and 7 pts had prior fulv treatment. All pts received zani (20 mg/kg Q2W) and standard doses of palbo and fulv. Eighteen pts (53%) remained on treatment; median duration of zani treatment was 6.9 mo (range 0.5-16.3). A dose-limiting toxicity (DLT) of neutropenia occurred in 1 of 7 DLT-evaluable pts in Part 1. Among all pts (n=34), the most common (>20%) treatment (zani, palbo and/or fulv)-related adverse events (TRAEs) were diarrhea (74%), neutrophil count decreased/neutropenia (62%), stomatitis (41%), asthenia (26%), nausea (24%), and anemia (21%). Grade (Gr) ≥3 TRAEs in 2 or more pts included neutrophil count decreased/neutropenia (50%), anemia (6%), diarrhea (6%), and thrombocytopenia (6%). AEs of special interest were all Gr ≤2 and included 4 pts with cardiac events (LVEF decrease of ≥10% from baseline) and 1 pt with infusion-related reaction. There were no treatment-related serious AEs. Palbo was discontinued for 1 pt due to an AE (AST increase); no pt discontinued zani treatment as a result of AEs. Two deaths occurred: 1 due to disease progression and 1 due to an unrelated AE of pneumonia caused by COVID-19. In 29 pts with measurable disease, the cORR was 34.5% (95% CI: 17.9, 54.3), all responses were cPRs, of which 1 is pending CR confirmation. DOR ranged from 2.3 to 14.9+ mo, with 8 confirmed responses ongoing, and the DCR was 93.1% (95% CI: 77.2, 99.2). Interim median PFS was 11.3 mo (range 0.03-16.7; 95% CI: 5.6, not estimable). PFS6 analysis is planned following the completion of enrollment. Conclusions: Zani in combination with palbo and fulv shows encouraging antitumor activity with durable responses in heavily pretreated pts and a manageable safety profile. This regimen has the potential to be a chemotherapy-free treatment option in pts with HER2+/HR+ mBC. Enrollment in the study is continuing.

Citation Format: Santiago Escrivá-de-Romani, Emilio Alba, Álvaro Rodríguez-Lescure, Sara Hurvitz, Juan Miguel Cejalvo, Maria Gión, Cristiano Ferrario, Manuel Ruiz Borrego, Rossanna C. Pezo, Erika Hamilton, Marc Webster, Timothy Pluard, Muralidhar Beeram, Begoña Jiménez Rodríguez, Hannah Linden, Cristina Saura, Adam Omidpanah, Phoebe Harvey, Marie-France Savard. Treatment of HER2-positive (HER2+) hormone-receptor positive (HR+) metastatic breast cancer (mBC) with the novel combination of zanidatamab, palbociclib, and fulvestrant [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD18-10.

Abstract GS2-02: GS2-02 Trastuzumab deruxtecan versus trastuzumab emtansine in patients with HER2-positive metastatic breast cancer: Updated survival results of the randomized, phase 3 study DESTINY-Breast03

Background: Trastuzumab deruxtecan (T-DXd) is approved in the United States and European Union for use in patients (pts) with HER2+ unresectable/metastatic breast cancer (mBC) after ≥1 prior anti–HER2 regimen(s). Approval was based on the randomized, multicenter, open-label, phase 3 DESTINY-Breast03 study (NCT03529110), in which T-DXd demonstrated statistically significant and clinically meaningful improvement in progression-free survival (PFS) compared with trastuzumab emtansine (T-DM1). At the primary interim analysis (data cutoff May 21, 2021), the risk of disease progression or death was reduced by 72% with T-DXd (P < 0.001; Cortes et al. N Engl J Med 2022). Overall survival (OS) data were immature for both treatment groups; although the prespecified cutoff for significance was not reached (NR), a trend toward benefit with T-DXd was observed. With further follow-up, we report results from the prespecified OS analysis of DESTINY-Breast03 (data cutoff July 25, 2022), including updated efficacy and safety.

Methods: Pts with HER2+ mBC previously treated with trastuzumab and a taxane in either the metastatic setting or (neo)adjuvant setting with progression within 6 mo of therapy, who could have received pertuzumab, were randomly assigned 1:1 to receive T-DXd 5.4 mg/kg every 3 weeks (Q3W) or T-DM1 3.6 mg/kg Q3W until disease progression. The primary endpoint was PFS by blinded independent central review (BICR). The key secondary endpoint was OS (80% powered at 2-sided significance level of 5%); other secondary endpoints included objective response rate (ORR), duration of response (DoR), PFS based on investigator assessment, and safety.

Results: 524 pts received either T-DXd (n = 261) or T-DM1 (n = 263). As of the updated data cutoff, median duration of study follow-up was 28.4 mo (range, 0.0-46.9 mo) for T-DXd and 26.5 mo (range, 0.0-45.0 mo) for T-DM1. Median treatment duration was 18.2 mo (range, 0.7-44.0 mo) for T DXd and 6.9 mo (range, 0.7-39.3 mo) for T-DM1. The risk of death was reduced by 36% (HR, 0.64; P = 0.0037) with T-DXd; median OS (mOS) was NR (95% CI, 40.5 mo-not evaluable [NE]), with 72 (27.6%) OS events, for T-DXd vs NR (95% CI, 34.0 mo-NE), with 97 (36.9%) OS events, for T-DM1. Landmark 12-mo OS rate was 94.1% (95% CI, 90.4-96.4) for T-DXd vs 86.0% (95% CI, 81.1-89.8) for T-DM1; 24-mo OS rate was 77.4% (95% CI, 71.7-82.1) for T-DXd vs 69.9% (95% CI, 63.7-75.2) for T-DM1. The P value for OS crossed the prespecified boundary (P = 0.013) and was statistically significant. mPFS by BICR was 28.8 mo (95% CI, 22.4-37.9 mo) with T-DXd, compared with 6.8 mo (95% CI, 5.6-8.2 mo) with T-DM1; HR, 0.33; nominal P < 0.000001. Key efficacy and safety results are shown in the table. Grade ≥3 treatment-emergent adverse events were experienced by 56.4% of T-DXd-treated pts and 51.7% of T DM1-treated pts. Drug-related interstitial lung disease/pneumonitis, as evaluated by an independent adjudication committee, was experienced by 39 pts (15.2%) in the T-DXd arm and 8 pts (3.1%) in the T DM1 arm; no adjudicated drug-related grade 4 or 5 events were observed in pts who received T-DXd.

Conclusions: Updated results confirm the superiority of T-DXd compared with T-DM1 for pts with HER2+ mBC previously treated with an anti-HER2 therapy, with highly clinically meaningful and statistically significant benefit in OS and PFS and a manageable safety profile with longer treatment duration.

Editorial Acknowledgment

Under the guidance of authors, assistance in medical writing and editorial support was provided by Laura Halvorson, PhD, and Rachel Hood, PhD, of ApotheCom, and was funded by Daiichi Sankyo.

Funding

This study was funded by Daiichi Sankyo and AstraZeneca.

Table. Summary of Efficacy Results for T-DXd and T-DM1

Citation Format: Sara Hurvitz, Roberto Hegg, Wei-Pang Chung, Seock-Ah Im, William Jacot, Vinod Ganju, Joanne Win Yang Chiu, Binghe Xu, Erika Hamilton, Srinivasan Madhusudan, Hiroji Iwata, Sevilay Altintas, Jan-Willem Henning, Giuseppe Curigliano, José Manuel Pérez-García, Anton Egorov, Yali Liu, Jillian Cathcart, Shahid Ashfaque, Javier Cortés. GS2-02 Trastuzumab deruxtecan versus trastuzumab emtansine in patients with HER2-positive metastatic breast cancer: Updated survival results of the randomized, phase 3 study DESTINY-Breast03 [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr GS2-02.

Abstract OT3-26-02: A Phase 3 study of gedatolisib plus fulvestrant with and without palbociclib in patients with HR+/HER2- advanced breast cancer previously treated with a CDK4/6 inhibitor plus a non-steroidal aromatase inhibitor (VIKTORIA-1)

Background: Gedatolisib is a potent reversible dual inhibitor that selectively targets all Class I isoforms of phosphoinositide 3-kinase (PI3K) and mechanistic target of rapamycin (mTOR). Two separate pivotal clinical trials demonstrated that PI3K and mTOR inhibitors are active in combination with endocrine therapy and prolong progression-free survival (PFS) among patients with hormone receptor positive (HR+)/HER2-negative (HER2-) advanced breast cancer (ABC) who had previously received endocrine therapy (SOLAR-1, BOLERO-2). CDK4/6 inhibitor (CDK4/6i) therapy has been approved in the front-line setting. However, patients eventually experience disease progression on CDK4/6i based therapy. Available data indicates that resistance to CDK4/6i is a transient adaptive mechanism that may be reversed by adding inhibitors of the PI3K/mTOR pathway (PI3K/mTORi). Thus, combination of PI3K/mTORi and CDK4/6i in patients whose disease progressed on prior CDK4/6i could potentially both restore sensitivity to CDK4/6i and prevent adaptive activation of the PI3K/mTOR pathway. This hypothesis was evaluated in a Phase 1b study (Layman SABCS 2021). Subjects with HR+/HER2- ABC who were CDK4/6i pretreated received gedatolisib (180 mg IV weekly for 3 weeks, then one week off) in combination with standard doses of palbociclib and fulvestrant. Median PFS was 12.9 months, and overall response rate was 63%. Grade 3-4 adverse events (AE) were observed at a low rate, and toxicity was overall easily managed with available standards of care, and few patients discontinued treatment due to treatment-related adverse events (4%). The most common AE was stomatitis; hyperglycemia of any grade occurred in 26% of patients. This preliminary data, dosing schedule, and study population characteristics form the basis for the Phase 3 trial, VIKTORIA-1. Trial design: This Phase 3, open-label, randomized, multinational two-part clinical trial will evaluate the efficacy and safety of gedatolisib and fulvestrant with or without palbociclib in patients with HR+/HER2- ABC previously treated with any CDK4/6i in combination with non-steroidal aromatase inhibitor therapy. Those without tumor PIK3CA mutations will be assigned to Study 1 and those with PIK3CA mutations will be assigned to Study 2. Study 1 will include up to 351 subjects randomized in a 1:1:1 ratio to Arm A (gedatolisib, palbociclib, and fulvestrant), Arm B (gedatolisib plus fulvestrant), or Arm C (fulvestrant). For subjects in Arm C whose disease progresses, crossover to Arm A or B is allowed. Study 2 will include up to 350 subjects randomized in a 3:3:1 ratio to Arm D (gedatolisib, palbociclib, and fulvestrant), Arm E (alpelisib plus fulvestrant), or Arm F (gedatolisib plus fulvestrant). Key eligibility criteria include adults with confirmed metastatic or locally advanced breast cancer, any menopausal status for females, radiologically evaluable disease, and prior CDK4/6i treatment with non-steroidal AI. Prior therapy with SERD, including fulvestrant is allowed. Key exclusion criteria include prior treatment with a PI3K, protein kinase B (Akt), or mTOR inhibitor, prior treatment with chemotherapy for advanced disease, more than two lines of prior endocrine therapy, bone only disease with no soft tissue components, active CNS metastases, and type 1 diabetes or uncontrolled type 2 diabetes. The primary endpoint is PFS assessed by blinded independent central review (BICR) per RECIST v1.1. Secondary endpoints included overall survival (OS), safety and tolerability, ORR, duration of response, time to response, CBR, quality of life, and pharmacokinetics. This trial is open for enrollment.

Citation Format: Sara Hurvitz, Fabrice Andre, Massimo Cristofanilli, Giuseppe Curigliano, Antonio Giordano, Hyo S. Han, Miguel Martín, Barbara Pistilli, Hope Rugo, Robert Wesolowski, Samuel Suzuki, Sarah C. Mutka, Igor Gorbatchevsky, Sibylle Loibl. A Phase 3 study of gedatolisib plus fulvestrant with and without palbociclib in patients with HR+/HER2- advanced breast cancer previously treated with a CDK4/6 inhibitor plus a non-steroidal aromatase inhibitor (VIKTORIA-1) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr OT3-26-02.

Updated Overall Survival of Ribociclib plus Endocrine Therapy versus Endocrine Therapy Alone in Pre- and Perimenopausal Patients with HR+/HER2- Advanced Breast Cancer in MONALEESA-7: A Phase III Randomized Clinical Trial

PURPOSE

Ribociclib plus endocrine therapy (ET) demonstrated a statistically significant progression-free survival and overall survival (OS) benefit in the phase III MONALEESA-7 trial of pre-/perimenopausal patients with hormone receptor (HR)-positive (HR+), HER2-negative (HER2-) advanced breast cancer (ABC). The median OS was not reached in the ribociclib arm in the protocol-specified final analysis; we hence performed an exploratory OS and additional outcomes analysis with an extended follow-up (median, 53.5 months).

PATIENTS AND METHODS

Patients were randomized to receive ET [goserelin plus nonsteroidal aromatase inhibitor (NSAI) or tamoxifen] with ribociclib or placebo. OS was evaluated with a stratified Cox proportional hazard model and summarized with Kaplan-Meier methods.

RESULTS

The intent-to-treat population included 672 patients. Median OS was 58.7 months with ribociclib versus 48.0 months with placebo [hazard ratio = 0.76; 95% confidence interval (CI), 0.61-0.96]. Kaplan-Meier estimated OS at 48 months was 60% and 50% with ribociclib and placebo, respectively. Subgroup analyses were generally consistent with the OS benefit, including patients who received NSAI and patients aged less than 40 years. Subsequent antineoplastic therapies following discontinuation were balanced between the ribociclib (77%) and placebo (78%) groups. Use of cyclin-dependent kinase 4/6 inhibitors after discontinuation was higher with placebo (26%) versus ribociclib (13%). Time to first chemotherapy was significantly delayed with ribociclib versus placebo. No drug-drug interactions were observed between ribociclib and either NSAI.

CONCLUSIONS

Ribociclib plus ET continued to show significantly longer OS than ET alone in pre-/perimenopausal patients, including patients aged less than 40 years, with HR+/HER2- ABC with 53.5 months of median follow-up (ClinicalTrials.gov, NCT02278120).

Correlation between work productivity loss and EORTC QLQ-C30 and -BR23 domains from the MONALEESA-7 trial of premenopausal women with HR+/HER2− advanced breast cancer

Background:

The phase III MONALEESA-7 trial (NCT02278120) assessed ribociclib + endocrine therapy (ET) versus ET in premenopausal women with HR+/HER2− advanced breast cancer (ABC). The relationship between work productivity loss (WPL) and domains of European Organisation for Research and Treatment of Cancer Quality of Life (EORTC QLQ-C30) and the breast cancer (BC)-specific module (QLQ-BR23) has not been explored in ABC. In this post hoc analysis (data cutoff, November 30, 2018), we assessed the correlation between the WPL component of the Work Productivity and Activity Impairment: General Health (WPAI:GH) questionnaire and EORTC QLQ-C30/BR23 domains.

Methods:

We analyzed EORTC and WPAI:GH data from 329 patients in both treatment arms of MONALEESA-7 who were employed during the trial. Separate univariable mixed-model repeated measures (MMRM) regression models were fitted for each domain, with WPL as dependent variable and each EORTC domain score as a single fixed-effect covariate. Linear and quadratic relationships were considered based on the Akaike information criterion. Next, two separate multivariable MMRM regression models were fitted with WPL a dependent variable and all QLQ-C30/BR23 domain scores as fixed-effect covariates. The strength of correlation between WPL and EORTC domains was assessed in terms of minimally important differences for the QLQ-C30/BR23 modules.

Results:

Our univariable analysis showed that greater WPL was statistically significantly associated with lower levels of overall quality of life (QoL) and other functional domains and with higher levels of all symptomatic domains of the QLQ-C30/BR23 modules. Our multivariable analysis determined that this correlation was primarily driven by changes in QoL; physical, role, social, and future perspective domains; and BC-specific symptomatic domains.

Conclusion:

This analysis determined the QoL domains that correlate with WPL in premenopausal patients with HR+/HER2− ABC. These results may inform prognostic tools to identify and characterize patients with greater risk for WPL and help design interventional strategies to minimize WPL.

Abstract PD13-08: First-in-human safety and activity of ARV-471, a novel PROTAC® estrogen receptor degrader, in ER+/HER2- locally advanced or metastatic breast cancer

Background: Resistance to current endocrine therapies remains a clinical challenge. Fulvestrant has established estrogen receptor (ER) degradation as a critical therapeutic strategy characterized by approximately 50% ER degradation, a clinical benefit rate (CBR) of < 20% in the post CDK 4/6 setting, and a suboptimal intramuscular route of administration. ARV-471 is a selective, orally bioavailable PROteolysis-TArgeting Chimera (PROTAC®) small molecule that induces degradation of wildtype and mutant ER. ARV-471 demonstrates superior ER degradation and antitumor activity compared to fulvestrant in endocrine sensitive and resistant xenograft models. Methods: This is a multi-center, first-in-human, open label study to assess the safety, pharmacokinetics, pharmacodynamics, and preliminary antitumor activity of ARV-471 administered orally in patients with ER+/HER2- advanced/metastatic breast cancer. The phase 1 monotherapy dose escalation used a 3+3 design with backfill to assess ARV-471 in pre-/post-menopausal women. Premenopausal women had to be on ovarian suppression. Patients were required to have received at least one prior CDK 4/6 inhibitor and at least 2 prior endocrine therapies. Up to 3 prior lines of chemotherapy were allowed. Results: As of June 6th, 2021, 50 patients were treated in the monotherapy escalation at total daily doses of 30mg (n=3), 60mg (n=3), 120mg (n=7), 180/200mg (n=11), 360mg (n=15), 500mg (n=8), and maximum administered dose of 700mg (n=3). A maximum tolerated dose was not reached and no dose limiting toxicities (DLTs) were observed. The most common (≥ 10%) treatment related adverse events (TRAEs) were nausea (24%), fatigue (12%), and vomiting (10%) that were predominantly grade 1 in severity. Two patients experienced grade 3 adverse events (AEs) that were potentially related to ARV-471: 1 patient treated at 180mg had a transient headache lasting 1 day, and 1 patient treated at 360mg had a venous thromboembolism (VTE) a few days after a minor procedure. There were no AEs > grade 3 potentially related to ARV-471. All AEs were manageable with only one patient discontinuing ARV-471 due to a TRAE (grade 3 VTE). ARV-471 demonstrated a dose-related increase in plasma exposure up to 500mg, with doses of 60mg daily and above resulting in steady-state Cmax and AUC24 that exceeded the exposure associated with tumor regression in preclinical models. Analysis of 12 paired biopsies from patients treated at 30 to 360mg daily demonstrated up to 90% ER degradation in tumors expressing WT or mutant ER. Of 34 patients who were evaluable for clinical benefit (confirmed complete response, partial response, or stable disease ≥ 24 weeks) the CBR was 41%. As of the data cutoff date, 6 of the 34 patients were continuing to receive study treatment, including 2 patients who had been on treatment for over 16 months. Two confirmed partial responses were observed among the 28 patients with baseline measurable disease and at least 1 on-treatment tumor assessment. Conclusion: ARV-471 was well tolerated with no DLTs at total daily doses up to 700mg. ARV-471 demonstrated robust ER degradation in paired biopsy samples and encouraging clinical activity (41% CBR) in patients who received prior CDK 4/6 inhibitors. ARV-471 is now being evaluated in the VERITAC Phase 2 monotherapy expansion at 200 mg and 500 mg once daily.

Citation Format: Erika Hamilton, Linda Vahdat, Hyo S Han, Jennifer Ranciato, Richard Gedrich, Chi F Keung, Deborah Chirnomas, Sara Hurvitz. First-in-human safety and activity of ARV-471, a novel PROTAC® estrogen receptor degrader, in ER+/HER2- locally advanced or metastatic breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD13-08.

Abstract P3-17-03: Raising the level of cancer care around the world: The feasibility and perceived benefit of a virtual breast tumor board

Introduction: It is well established that multidisciplinary tumor boards improve the decision-making process for cancer patients. Tumor boards have been shown to improve the accuracy of diagnosis and staging, optimize patient outcomes, increase adherence to guidelines, and educate our peers and trainees. However, over 80% of patients in the United States receive their cancer care in the community setting, where access to multi-disciplinary tumor boards may not be readily available. This may particularly impact underserved populations who often lack the resources to travel to an academic center for second opinions or treatment. The problem is worse in low-resource countries. Virtual expert tumor boards could provide an effective solution. Methods: Preeminent breast oncology faculty from around the Unites States were assembled into virtual tumor board panels via an online platform to discuss challenging cases submitted by community providers and trainees. These tumor boards consisted of a moderator, a breast radiologist, a breast medical oncologist, a breast surgeon, and a breast radiation oncologist. The purpose of this ongoing endeavor is to educate community oncologists on how to best manage challenging cases. Following tumor board discussions, written recommendations were shared with submitting providers within 48 hours and recordings of the discussions were also later provided. After submitting providers watched the recording of their case discussion, we conducted a survey to determine their perceived benefit of the expert panel discussion. Results: From Sept 2020 to June 2021, ten breast cancer panels were virtually convened with 17 expert faculty panelists. During that time, 21 providers submitted 94 cases from the U.S. and around the world to be discussed by the expert panel. Thirty-three percent of the providers who submitted a case to be discussed have subsequently submitted an additional case to a later panel. Surveys were sent to all submitting providers and responses were recorded from 16/21 submitters (76.2%).

Conclusion: With more than three out of four submitters responding, we learned that not only is it feasible to convene virtual expert breast tumor boards to discuss challenging cases, but the vast majority of respondents learned new information, changed management of their patients, and wanted to submit additional cases. This effort could raise the level of breast cancer care around the world. Ongoing assessment of educational and patient care impacts will be necessary.

QuestionNumber answered (n)Number who answered yes (%)Number who answered no (%)Did you learn something new from the PrecisCa discussion of your case scenario?1614 (87.5)2 (12.5)Will anything you learned from the PrecisCa discussion of your case scenario change the management of this or future patients?1615 (93.8)1 (6.2)Are you likely to submit a future challenging case scenario to PrecisCa?1616 (100)0 (0)

Citation Format: Naomi Dempsey, Lauren Chiec, Mikala Lodder, Erin Shonkwiler, Kayla Haines, Reshma Mahtani, William Gradishar, Thomas Buchholz, Anne O'Dea, Norman Wolmark, Sara Hurvitz, Joyce O'Shaughnessy, Maxine Jochelson, Reni Butler, Eleftherios Mamounas, Frank Vicini, Mark Pegram, Chirag Shah, Tari King, Ruth O'Regan, Monica Morrow, Mohammad Jahanzeb. Raising the level of cancer care around the world: The feasibility and perceived benefit of a virtual breast tumor board [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-17-03.

Abstract OT1-12-05: Phase II neoadjuvant trial evaluating trastuzumab deruxtecan with or without anastrozole for HER2-low, HR+ early stage breast cancer

Background Although patients with clinical response of hormone receptor-positive (HR+)/HER2-negative breast cancer (BC) frequently respond to neoadjuvant therapy, fewer than 10% of patients achieve a pathologic complete response (pCR) with standard chemotherapy or endocrine therapy, even in combination with targeted agents such as CDK4/6 inhibitors. Thus, finding more effective therapies for this disease remains an area of unmet need. HER2 amplification is a known driver of endocrine resistance and HER2 may be expressed at a low level (IHC 1+ or 2+) in up to 60% of HR+ BC. Trastuzumab deruxtecan (DS-8201a, T-DXd) is a novel HER2-targeting antibody drug conjugate (ADC) that is FDA approved for HER2-positive metastatic BC and has demonstrated promising clinical efficacy in HER2-low BC with an objective response rate of ~37%. The aim of TALENT (TRIO-US B-12) is to evaluate the clinical activity and toxicity of neoadjuvant T-DXd either alone or in combination with endocrine therapy in patients with HR+/HER2-low early BC. Methods TRIO-US B-12 TALENT (NCT04553770) is an ongoing randomized, multicenter, open-label, two-stage, phase II neoadjuvant trial for participants with early stage, HR+, HER2-low expressing (1+ or 2+ by IHC) BC. Eligible participants include men and women with previously untreated, operable invasive BC greater than 2.0 cm (cT2) in size. Pts with recurrent or metastatic BC, or inflammatory BC are excluded. Pts are randomized 1:1 to receive six cycles of T-DXd (5.4 mg/kg IV q21 days) either alone or in combination with anastrozole AI (1 mg PO QD). Men and pre/peri menopausal women randomized to the AI arm also receive standard of care GnRH agonist. Stratification factors include HER2 expression (1+ or 2+) and menopausal status (men stratified as post-menopausal). Tumor tissue is taken at baseline, cycle 1 day 17-21, and at surgery. Blood samples are taken at four time points for biomarker analysis. The primary endpoint is pCR rate (breast and lymph node) at definitive surgery. In stage I, 58 participants will be randomized (29/arm). If ≥2 participants in an arm achieve pCR, that arm will expand (stage II) to enroll an additional 15 participants (total of 44/arm). A pCR rate of >10% (5/44) would be considered favorable, warranting further evaluation of the treatment in a larger trial. Other endpoints include safety, changes in Ki67 expression, Residual Cancer Burden index, biomarker analysis (including serial cfDNA analysis), and health-related quality of life. As of June 2021, sixteen participants have enrolled. Conclusions To our knowledge this is the first and only ongoing study evaluating T-DXd with or without endocrine therapy for HR+, HER2-low breast cancer in the neoadjuvant setting. The study will shed light on clinical activity and biomarkers, which may guide larger confirmatory studies for patients with HR+, HER2-low early breast cancer.

Citation Format: Sara Hurvitz, Aditya Bardia, Merry L. Tetef, Nicholas P. McAndrew, Steven Applebaum, Aashini K. Master, Maggie L. DiNome, Minna K. Lee, Evangelia Kirimis, David D. Kim, Lisa S. Wang, Kyle Greene, Vu Phan, Nihal Abdulla, David Chan, Laura M. Spring, Christine Kivork, James Chauv. Phase II neoadjuvant trial evaluating trastuzumab deruxtecan with or without anastrozole for HER2-low, HR+ early stage breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT1-12-05.

Abstract GS3-01: Trastuzumab deruxtecan (T-DXd; DS-8201a) vs. trastuzumab emtansine (T-DM1) in patients (pts) with HER2+ metastatic breast cancer (mBC): subgroup analyses from the randomized phase 3 study DESTINY-Breast03

Background: T-DXd is a HER2-targeting antibody-drug conjugate approved for the treatment of pts with advanced HER2+ mBC based on the DESTINY-Breast01 study (NCT03248492). DESTINY-Breast03 (NCT03529110) isa randomized, multicenter, open-label, phase 3 study assessing the efficacy and safety of T-DXd vs. T-DM1 in pts with HER2+ mBC previously treated with trastuzumab and taxane. In the primary analysis, T-DXd demonstrated a clinically meaningful and statistically significant improvement in PFS vs. T-DM1 (Corteset al, ESMO 2021). In this exploratory analysis, we provide additional efficacy and safety data in subgroups, including in pts with brain metastases (BMs). Methods: Pts were randomly assigned 1:1 to receive 5.4 mg/kg T-DXd or 3.6 mg/kg T-DM1 Q3W. Pts with clinically stable BMs were eligible. Lesions were measured per modified Response Evaluation Criteria in Solid Tumors version 1.1. The primary endpoint was progression-free survival (PFS) determined by blinded independent central review (BICR). PFS and overall response rate (ORR) were analyzed for subgroups.Sites of progression and post-end-of-study therapies were also investigated. Results: At data cutoff (May 21, 2021), 524 pts were randomly assigned to T-DXd (n=261) orT-DM1 (n=263). T-DXd demonstrated superior PFS by BICR vs. T-DM1 (HR, 0.28 [95%CI, 0.22-0.37]; P=7.8 x 10-22); median (m) PFS by BICR was not reached (95% CI, 18.5-NE) for T-DXd compared with 6.8 mo (95% CI, 5.6-8.2) forT-DM1. For pts with stable BMs at baseline (n=82), mPFS was 15.0 mo (95% CI,12.5-22.2) for T-DXd vs. 3.0 mo (95% CI, 2.8-5.8) for T-DM1 (HR, 0.25 [95% CI,0.31-0.45)]. Overall, confirmed ORR for T-DXd was 79.7% vs. 34.2% for T-DM1.For patients with stable BMs at baseline, ORR was 67.4% for T-DXd vs. 20.5% forT-DM1. Consistent PFS and ORR benefit was also observed across other subgroups(Table 1). At data cutoff, 84 (32.2%) pts treated with T-DXd had progressive disease (PD) versus 155 (58.9%) with T-DM1. In pts with stable BMs in the T-DXd arm, 48.8% of pts (21/43) had PD. In pts with stable BMs in the T-DM1 arm, 69.2%of pts (27/39) had PD. Data on sites of progression will be presented. Further analyses are underway and will be presented. Overall, the safety profile of T-DXd was manageable and comparable with its known safety profile. Adjudicated drug-related interstitial lung disease/pneumonitis was reported in 27 (10.5%) pts treated with T-DXd and 5 (1.9%) pts treated with T-DM1 overall, with no grade 4 or 5 events. Additional new safety data will be presented. Conclusion: DESTINY-Breast03,the first-reported randomized phase 3 trial comparing T-DXd to standard of care, met the primary endpoint with T-DXd demonstrating superior PFS vs. T-DM1and T-DXd had a manageable safety profile. In this exploratory analysis, consistent PFS and ORR benefit with T-DXd vs. T-DM1 was observed across subgroups in pts with HER2+ mBC previously treated with trastuzumab and taxane, including in pts with BMs.

Table 1.Subgroup Analyses forPFS and ORR of T-DXd versus T-DM1PFS by BICR HR (95% CI)Absolute ORR Difference (T-DXd-T-DM1) (95% CI)All patients (N=524)0.28 (0.22-0.37)45.5 (37.6-53.4)Hormone receptorPositive (n=272)0.32 (0.22-0.46)47.3 (36.1-58.4)Negative (n=248)0.30 (0.20-0.44)43.2 (31.5-55.0)Prior pertuzumabYes (n=320)0.31 (0.22-0.43)46.7 (36.5-56.9)No (n=204)0.30 (0.19-0.47)43.6 (30.5-56.7)Prior lines of therapya0-1 (n=258)0.33 (0.23-0.48)39.3 (27.3-51.2)≥2 (n=266)0.28 (0.19-0.41)51.6 (40.9-62.4)Visceral disease Yes (n=384)0.28 (0.21-0.38)48.3 (39.1-57.6)No (n=140)0.32 (0.17-0.58)39.1 (23.6-54.6)Brain metastases at baseline Yes (n=82)0.25 (0.13-0.45)46.9 (25.6-68.3)No (n=442)0.30 (0.22-0.40)45.5 (36.9-54.1)

Citation Format: Sara Hurvitz, Sung-Bae Kim, Wei-Pang Chung, Seock-Ah Im, Yeon Hee Park, Roberto Hegg, Min-Hwan Kim, Ling-Ming Tseng, Vanessa Petry, Chi-Feng Chung, Hiroji Iwata, Erika Hamilton, Giuseppe Curigliano, Binghe Xu, Caleb Lee, Yali Liu, Jillian Cathcart, Emarjola Bako, Sunil Verma, Javier Cortés. Trastuzumab deruxtecan (T-DXd; DS-8201a) vs. trastuzumab emtansine (T-DM1) in patients (pts) with HER2+ metastatic breast cancer (mBC): subgroup analyses from the randomized phase 3 study DESTINY-Breast03 [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr GS3-01.

Abstract ES1-3: The ideal partner to HER2 directed therapies

Approximately ten percent of breast cancers are characterized by amplification/overexpression of HER2 with expression of one or both hormone receptors, deemed “double positive” or “triple positive” breast cancer. Though this cancer subtype has a lower chance of pathologic complete response with neoadjuvant therapy, it benefits as much from HER2-targeted therapies and has a long-term outcome that is as good or better than outcomes associated with the hormone receptor negative, HER2-positive subtype. Importantly, hormone receptor expression provides another opportunity to target additional signaling pathways implicated in tumor cell growth and survival, thus potentially expanding the armamentarium of effective therapeutics for this cancer subtype. In this presentation, clinical trial evidence evaluating the use of HER2-targeted agents plus endocrine therapy in the curative and advanced stage settings will be considered, including recent data directly comparing an endocrine-based versus chemotherapy-based approach. Results from studies evaluating whether the addition of endocrine therapy to chemotherapy plus HER2-directed treatment leads to antagonistic, null, or additive effects will be presented. The benefit of HER1/HER2-directed tyrosine kinase inhibitors such as lapatinib and neratinib based on tumor hormone receptor expression will be assessed. Finally, data from preclinical and clinical studies evaluating novel therapeutic strategies including the use of CDK4/6- or PI3K-pathway inhibitors will be considered and ongoing clinical trials addressing the optimal management of this disease subtype will be reviewed.

Citation Format: S Hurvitz. The ideal partner to HER2 directed therapies [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr ES1-3.

Abstract OT2-11-08: AMEERA-5 : A randomized, double-blind phase 3 study of amcenestrant (SAR439859) + palbociclib versus letrozole + palbociclib for previously untreated ER+/HER2- advanced breast cancer

Background Selective estrogen receptor degraders (SERDs) block estrogen receptor (ER) associated signaling and have created interest for treating patients (pts) with advanced ER+ breast cancer (BC). Fulvestrant is currently the only SERD available for advanced BC but requires intramuscular administration, limiting the applied dose, exposure and receptor engagement. Amcenestrant (SAR439859) is an oral SERD that binds with high affinity to both wild-type and mutant ER, blocking estradiol binding and promoting up to 98% ER degradation in preclinical studies. In the phase I AMEERA-1 study of pretreated pts with ER+/HER2- advanced BC, amcenestrant 150-600 mg once daily (QD) showed a mean ER occupancy of 94% with plasma concentrations > 100 ng/mL and a favorable safety profile (Bardia, 2019; data on file). Combination therapy with amcenestrant + palbociclib (palbo) was also evaluated as part of this ongoing phase I study. CDK 4/6 inhibitors (CDK4/6i) combined with an aromatase inhibitor (AI), the gold standard for first line treatment for advanced breast cancer, prolong progression free survival (PFS) in pts with no prior treatment for ER+/HER2- advanced BC, but OS benefit has not been shown yet in postmenopausal pts. There remains a clinical need for more effective treatments in this setting. Methods AMEERA-5 (NCT04478266) is an ongoing, prospective, randomized, double-blind phase III study comparing the efficacy and safety of amcenestrant + palbo with that of letrozole + palbo in pts with advanced, locoregional recurrent or metastatic ER+/HER2- BC who have not received prior systemic therapy for advanced disease. The study includes men, pre/peri-menopausal (with goserelin) and post-menopausal women. Pts with progression during or within 12 months of (neo)adjuvant endocrine therapy using any of the following agents are excluded: AI, selective estrogen receptor modulators, CDK4/6i. Pts are randomized 1:1 to either continuous amcenestrant 200 mg or letrozole 2.5 mg QD orally with matching placebos; both combined with palbo 125 mg QD orally (d1-21 every 28-d cycle). Randomization is stratified according to disease type (de novo metastatic vs recurrent disease), the presence of visceral metastasis, and menopausal status. The primary endpoint is investigator assessed progression free survival (PFS) (RECIST v1.1). Secondary endpoints are overall survival, PFS2, objective response rate, duration of response, clinical benefit rate, pharmacokinetics of amcenestrant and palbo, health-related quality of life, time to chemotherapy, and safety. Biomarkers will be measured in paired tumor biopsies and cell free deoxyribonucleic acid (cfDNA) over time. Target enrolment = 1066 pts; enrolment as of 6/2021 = 415 pts. Bardia A, et al., J Clin Oncol. 2019; 37 (15 suppl):1054. Funding: Sanofi. This abstract was accepted and previously presented at the 2021 American Society of Clinical Oncology Annual Meeting. All rights reserved.

Citation Format: Aditya Bardia, Javier Cortes, Sara Hurvitz, Suzette Delaloge, Hiroji Iwata, Zhi-Ming Shao, Dheepak Kanagavel, Patrick Cohen, Qianying Liu, Sylvaine Cartot-Cotton, Vasiliki Pelekanou, Joyce O’Shaughnessy. AMEERA-5 : A randomized, double-blind phase 3 study of amcenestrant (SAR439859) + palbociclib versus letrozole + palbociclib for previously untreated ER+/HER2- advanced breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT2-11-08.

Abstract PD4-04: Updated results of tucatinib vs placebo added to trastuzumab and capecitabine for patients with previously treated HER2-positive metastatic breast cancer with brain metastases (HER2CLIMB)

Background: Tucatinib is an oral tyrosine kinase inhibitor highly specific for HER2 that is approved for use in combination with trastuzumab and capecitabine in adults with advanced or metastatic HER2+ breast cancer, including patients with brain metastases, who have received one or more prior anti-HER2-based regimens in the metastatic setting. In the HER2CLIMB trial, the tucatinib regimen significantly prolonged progression-free survival (PFS) and overall survival (OS) in patients with HER2+ metastatic breast cancer (Murthy, NEJM 2020), including in patients with untreated, treated stable, and treated progressing brain metastases (Lin, J Clin Oncol, 2020). With an additional 15.6 months of follow-up, addition of tucatinib continued to show clinically meaningful prolongation of PFS and OS in the total study population (Curigliano, ASCO Meeting, 2021). We report updated results of exploratory efficacy analyses in patients with brain metastases. Methods: All patients in HER2CLIMB had a baseline brain MRI. Patients with brain metastases were eligible and classified as untreated, treated stable, or treated progressing. Patients were randomized 2:1 to receive tucatinib 300 mg twice daily or placebo, in combination with trastuzumab and capecitabine. Following the primary analysis, the protocol was amended to unblind sites to treatment assignment and allowed crossover from the placebo regimen to the tucatinib regimen. Efficacy analyses in patients with brain metastases at baseline were performed at approximately 2 years from the last patient randomized by applying RECIST 1.1 to the brain based on investigator evaluation. OS and CNS-PFS (progression in the brain or death) were evaluated in all patients with brain metastases. Patients without CNS-PFS events were censored at the last brain MRI. Confirmed intracranial (IC) objective response rate (ORR-IC) was evaluated in patients with measurable IC disease. Results: At a median follow-up of 29.6 months, median OS was 21.6 months vs 12.5 months in all patients with brain metastases (HR: 0.60; 95% CI: 0.44, 0.81), 21.4 months vs 11.8 months in patients with untreated/treated progressing brain metastases (HR: 0.52; 95% CI: 0.36, 0.77), and 21.6 months vs 16.4 months in patients with treated stable brain metastases (HR: 0.70; 95% CI: 0.42, 1.16). Median CNS-PFS was 9.9 months vs 4.2 months in all patients with brain metastases (HR: 0.39; 95% CI: 0.27, 0.56), 9.6 months vs 4.0 months in patients with untreated/treated progressing brain metastases (HR: 0.34; 95% CI: 0.22, 0.54), and 13.9 months vs 5.6 months in patients with treated stable brain metastases (HR: 0.41; 95% CI: 0.19, 0.85). ORR-IC was higher in the tucatinib arm (47.3%; 95% CI: 33.7, 61.2) vs the placebo arm (20.0%; 95% CI: 5.7, 43.7) for patients with brain metastases, and median duration of response (DOR) was 8.6 months (95% CI: 5.5, 10.3) vs 3.0 months (95% CI: 3.0, 10.3). Conclusions: With 15.6 months of additional follow-up, the tucatinib-trastuzumab-capecitabine regimen resulted in a robust and durable prolongation of OS for all patients with HER2+ metastatic breast cancer and brain metastases. Additionally, this benefit was maintained in patients with untreated/treated progressing and treated stable brain metastases. Treatment with tucatinib continued to show clinically meaningful benefit in CNS-PFS consistent with the primary analysis.

Citation Format: Nancy U Lin, Rashmi K Murthy, Vandana Abramson, Carey Anders, Thomas Bachelot, Philippe Bedard, Virginia Borges, David Cameron, David Cameron, Lisa Carey, A Jo Chien, Giuseppe Curigliano, Michael DiGiovanna, Karen Gelmon, Gabriel Hortobagyi, Sara Hurvitz, Ian Krop, Sherene Loi, Sibylle Loibl, Volkmar Mueller, Mafalda Oliveira, Elisavet Paplomata, Mark Pegram, Dennis Slamon, Amelia Zelnak, Jorge Ramos, Wentao Feng, Eric Winer. Updated results of tucatinib vs placebo added to trastuzumab and capecitabine for patients with previously treated HER2-positive metastatic breast cancer with brain metastases (HER2CLIMB) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD4-04.

Abstract OT1-02-02: A global, phase 2 study of ARX788 in patients with HER2-positive metastatic breast cancer whose disease is resistant or refractory to T-DM1, and/or T-DXd, and/or tucatinib-containing regimens

Background: The HER2 receptor is a cancer driver which is overexpressed on 15-20% of breast cancers. Though historically survival is poor with this disease subtype, HER2+ targeted therapy has improved survival in both early and advanced disease. In spite of this, most patients in the metastatic setting will eventually experience disease progression and death. Therefore, new therapeutic options and innovative treatments are needed for patients with recurrent or refractory disease. ARX788 is a next-generation antibody–drug conjugates (ADC) using a technology platform whereby a HER2 specific monoclonal antibody is conjugated with Amberstatin269, a potent cytotoxic tubulin inhibitor. Site-specific, high homogenous, and stable covalent conjugation in ARX788 leads to slow release and prolonged peak of serum pAF-AS269, which may contribute to the lower systemic toxicity, increased targeted delivery of payload to tumor cells, and lower effective dose compared to other HER2 ADCs.Methods: ACE-Breast-03 (NCT04829604) is a global, single arm, phase 2 study designed to assess anticancer activity and safety of ARX788 in patients with metastatic HER2 positive breast cancer. Patients whose disease is resistant or refractory to T-DM1, and/or T-DXd, and/or tucatinib-containing regimens are eligible. Patients must have adequate organ function and any brain metastasis must demonstrate radiographic stability and lack of steroid dependence. Approximately 200 subjects with advanced HER2-positive breast cancer will be enrolled. ARX788 will be administered as an intravenous (IV) infusion at 1.5 mg/kg as the initial dose on Day 1 of the first 4-week cycle and followed by 1.3 mg/kg at every subsequent 4-week cycle. Efficacy will be assessed using Response Evaluation Criteria in Solid Tumors (RECIST) v 1.1 via imaging every 8 weeks (±7 days) on study and endpoints include objective response rate (ORR), duration of response (DOR), time to response (TTR), best overall response (BOR), disease control rate (DCR), progression-free survival (PFS), and overall survival (OS). The safety and tolerability profile will be assessed. Blood samples will be collected at specified time points to determine serum concentrations of ARX788 (intact ADC), total antibody, and metabolite pAF-AS269. Biomarkers (e.g., cell-free DNA, serum HER2 extracellular domain, and circulating tumor cells) at baseline and on-treatment will be analyzed for exploratory research. Descriptive statistics will be used to evaluate anticancer activity, safety, and tolerability. The study is currently recruiting patients. Please contact breast03trialinquiry@ambrx.com for additional information.

Citation Format: Janice Lu, Kevin M Kalinsky, Debu Tripathy, George W Sledge, William Gradishar, Ruth O’Regan, Joyce O’Shaughnessy, Shanu Modi, Joshua Drago, Haeseong Park, Amelia McCartney, Sophia Frentzas, Catherine Shannon, Katharine Cuff, Richard Eek, Miguel Idzwan Martin, Giuseppe Curigliano, Guy Jerusalem, Chiun-Sheng Huang, Michael Press, Matt Li, Dong Xu, Cynthia Song, Richard Huhn, Jinchun Yan, Sara Hurvitz. A global, phase 2 study of ARX788 in patients with HER2-positive metastatic breast cancer whose disease is resistant or refractory to T-DM1, and/or T-DXd, and/or tucatinib-containing regimens [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT1-02-02.

Abstract P1-18-11: Analysis of first-line (1L) patients (pts) with de novo disease vs late relapse and all pts with vs without prior chemotherapy (CT) in the MONALEESA-3 (ML-3) trial

Background: The phase 3 ML-3 trial demonstrated significant OS benefit for ribociclib (RIB) + fulvestrant (FUL) over placebo (PBO) + FUL as first- or second- line therapy in postmenopausal pts with HR+/HER2- advanced breast cancer (ABC). Prior treatment ([neo]adjuvant or advanced setting) may impact subsequent therapy outcomes, including OS; therefore, understanding the potential effect of prior treatment is of high clinical interest. Here, we present PFS and OS data from 2 subgroup analyses in ML-3: 1L pts with de novo disease vs late relapse and all pts with vs without prior CT. Methods: ML-3 (NCT02422615) enrolled postmenopausal pts who were randomized 2:1 to receive RIB + FUL or PBO + FUL. Pts with prior ET ([neo]adjuvant or ≤1 prior ET for ABC) and no CT for ABC were included. Pts with de novo disease were defined as initially diagnosed as ABC with no prior treatment for ABC. Pts with late relapse were defined as those who relapsed >12 months from completion of (neo)adjuvant ET with no prior treatment for ABC. Since prior CT for ABC was not allowed in ML-3, the prior CT analysis compares pts with prior (neo)adjuvant CT vs those without prior (neo)adjuvant CT. Results: The data cutoff was October 30, 2020. Within the 1L population, in the de novo vs late relapse analysis, 132 pts (RIB: n = 91; PBO: n = 41) had de novo disease, and 153 had late relapse (RIB: n = 98; PBO: n = 55). Baseline characteristics were generally balanced between the de novo and late relapse groups, with some notable exceptions: a higher proportion of pts with de novo disease were aged <65 years (52.3% vs 41.8%) and a lower proportion had visceral disease (53.0% vs 63.4%). In the late relapse group, 70.6% had prior (neo)adjuvant CT. De novo disease or late relapse did not appear to be prognostic as both PFS and OS were generally comparable between those 2 groups among pts treated with RIB or those treated with PBO (Table). Treatment with RIB + FUL demonstrated consistent PFS and OS benefits over PBO + FUL in both pts with de novo disease and those with late relapse. In the prior CT analysis, 391 pts (RIB: n = 265; PBO: n = 126) had prior CT (41.4% in 1L and 55.5% in 2L/early relapse [3.1% data missing]) and 334 (RIB: n = 219; PBO: n = 115) had no prior CT (60.8% in 1L, 38.9% in 2L/early relapse [0.3% data missing]). Baseline characteristics were generally balanced between pts with and without prior CT, with some exceptions: a higher proportion of pts with prior CT were aged <65 years (62.1% vs 42.8%) and had prior ET in any setting (86.4% vs 53.0%). Pts without prior CT had longer median PFS and OS compared with those who had prior CT in both the RIB and PBO arms (OS without vs with prior CT treated with RIB: HR, 0.68 [95% CI, 0.52-0.89]; PBO: HR, 0.72 [95% CI, 0.52-1.00]). Treatment with RIB + FUL demonstrated consistent PFS and OS benefits over PBO + FUL in both pts with prior CT and those without (OS for RIB vs PBO with prior CT: HR, 0.76 [95% CI, 0.58-1.01]; without prior CT: HR, 0.70 [95% CI, 0.50-0.97]). Conclusions: This exploratory analysis demonstrated that metastatic presentation (de novo vs late relapse) was not prognostic for disease outcomes; however, prior CT exposure, even in (neo)adjuvant, was associated with poorer PFS and OS. The addition of RIB showed consistent PFS and OS benefit across all subgroups in this analysis. Particularly, the addition of RIB resulted in a consistent and clinically meaningful PFS and OS benefit with a decrease in relative risk of death by 24% in pts with prior exposure to CT.

RIB + FULPBO + FULHR (RIB vs PBO)De novo/late relapseMedian PFS (95% CI), monthsDe novo35.6. (27.1-42.0)22.1. (14.6-33.1)0.55. (0.35-0.86)Late relapse35.8. (20.0-44.4)22.0. (16.5-27.7)0.60. (0.40-0.89)HR (de novo vs late elapse)0.93. (0.64-1.36)0.996. (0.63-1.57)Median OS (95% CI), monthsDe novo59.9. (52.7-NE)52.9. (39.6-NE)0.67. (0.38-1.19)Late relapseNE. (54.9-NE)52.3. (40.4-NE)0.69. (0.42-1.13)HR (de novo vs late relapse)0.899. (0.552-1.465)0.91. (0.51-1.62)Prior (neo)adjuvant CTMedian PFS (95% CI), monthsWithout prior CT28.3. (23.3-35.6)17.5. (13.6-21.9)0.60. (0.46-0.78)With prior CTa17.9. (14.3-19.9)10.8. (7.2-12.3)0.61. (0.48-0.78)HR (without vs with prior CT)0.76. (0.60-0.94)0.72. (0.55-0.95)Median OS (95% CI), monthsWithout prior CTNE (54.9-NE)44.9 (38.5-58.1)0.70. (0.50-0.97)With prior CTa43.0 (39.1-51.2)40.1 (30.3-48.6)0.76. (0.58-1.01)HR (without vs with prior CT)0.68 (0.52-0.89)0.72 (0.52-1.00)NE, not estimable a Includes 4 patients who received prior CT for ABC (protocol violation).

Citation Format: Michelino De Laurentiis, Matteo Lambertini, Stephen Chia, Hope S Rugo, Katarina Petrakova, Cristian Villanueva, Sara Hurvitz, J. Thaddeus Beck, Agnes Lteif, Sina Haftchenary, Uday Deore, Jiwen Wu, Nagi El-Saghir. Analysis of first-line (1L) patients (pts) with de novo disease vs late relapse and all pts with vs without prior chemotherapy (CT) in the MONALEESA-3 (ML-3) trial [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-18-11.

Genomic Profiling of Premenopausal HR+ and HER2- Metastatic Breast Cancer by Circulating Tumor DNA and Association of Genetic Alterations With Therapeutic Response to Endocrine Therapy and Ribociclib

PURPOSE

This analysis evaluated the genomic landscape of premenopausal patients with hormone receptor–positive and human epidermal growth factor receptor 2–negative advanced breast cancer and the association of genetic alterations with response to ribociclib in the phase III MONALEESA-7 trial.

METHODS

Premenopausal patients were randomly assigned 1:1 to receive endocrine therapy plus ribociclib or placebo. Plasma collected at baseline was sequenced using targeted next-generation sequencing for approximately 600 relevant cancer genes. The association of circulating tumor DNA alterations with progression-free survival (PFS) was evaluated to identify biomarkers of response and resistance to ribociclib.

RESULTS

Baseline circulating tumor DNA was sequenced in 565 patients; 489 had evidence of ≥ 1 alteration. The most frequent alterations included PIK3CA (28%), TP53 (19%), CCND1 (10%), MYC (8%), GATA3 (8%), receptor tyrosine kinases (17%), and the Chr8p11.23 locus (12%). A treatment benefit of ribociclib was seen with wild-type (hazard ratio [HR] 0.45 [95% CI, 0.33 to 0.62]) and altered (HR 0.57 [95% CI, 0.36 to 0.9]) PIK3CA. Overall, patients with altered CCND1 had shorter PFS regardless of treatment, suggesting CCND1 as a potential prognostic biomarker. Benefit with ribociclib was seen in patients with altered (HR 0.21 [95% CI, 0.08 to 0.54]) or wild-type (HR 0.52 [95% CI, 0.39 to 0.68]) CCND1, but greater benefit was observed with altered, suggesting predictive potential of CCND1. Alterations in TP53, MYC, Chr8p11.23 locus, and receptor tyrosine kinases were associated with worse PFS, but ribociclib benefit was independent of alteration status.

CONCLUSION

In this study—to our knowledge, the first large study of premenopausal patients with hormone receptor–positive and human epidermal growth factor receptor 2–negative advanced breast cancer—multiple genomic alterations were associated with poor outcome. A PFS benefit of ribociclib was observed regardless of gene alteration status, although in this exploratory analysis, a magnitude of benefits varied by alteration.

Abstract PD2-04: Updated overall survival (OS) results from the phase III MONALEESA-7 trial of pre- or perimenopausal patients with hormone receptor positive/human epidermal growth factor receptor 2 negative (HR+/HER2−) advanced breast cancer (ABC) treated with endocrine therapy (ET) ± ribociclib

Background: MONALEESA-7 (NCT02278120), the first large randomized phase III clinical trial dedicated to investigating a cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) plus ET vs ET + placebo (PBO) in pre- or perimenopausal patients with HR+/HER2− ABC, previously demonstrated a statistically significant improvement in OS with the addition of ribociclib (RIB) to ET vs PBO + ET (median, not reached vs 40.9 months; HR, 0.71 [95% CI, 0.54-0.95]; P = .00973; Im SA, et al. N Engl J Med. 2019). This concluded the protocol-defined final analysis of OS and the patients and investigators were unblinded to their treatment assignment allowing patients on the PBO arm to cross-over to RIB treatment. Longer follow-up allows for more events to further characterize the long-term survival benefits. Here we report an exploratory update of OS after a minimum of ~ four years of follow-up, an additional 20 months since the last report. Methods: Pre- or perimenopausal patients with HR+/HER2− ABC were randomized 1:1 to receive RIB or PBO plus goserelin with either a nonsteroidal aromatase inhibitor (NSAI; letrozole or anastrozole) or tamoxifen. RIB is approved in combination with an NSAI in pre- or perimenopausal patients. Patients who had received a prior CDK4/6i or ET in the advanced setting were excluded. Patients who received ET in the (neo)adjuvant setting or ≤ 1 prior line of chemotherapy for advanced disease were eligible to enroll. Updated OS were evaluated by Cox proportional hazards model and summarized using Kaplan-Meier methods. Additional post-progression endpoints such as progression-free survival 2 (PFS2), time to chemotherapy (CT) and CT-free survival were also evaluated and summarized. Results: The data cutoff for this updated OS analysis was 29 June 2020, and the median follow-up was 53.5 mo (min, 46.9 mo). These updated results with extended follow-up demonstrated an OS benefit with RIB + ET vs PBO + ET (median, 58.7 vs 48.0 mo; HR, 0.76 [95% CI, 0.61-0.96]). In patients receiving an NSAI, a similar OS benefit was observed with RIB + NSAI vs PBO + NSAI (median, 58.7 vs 47.7 mo; HR, 0.80 [95% CI, 0.62-1.04]). The survival benefit shown in subgroup analyses was consistent with the intent-to-treat (ITT) population. PFS2, time to chemotherapy (CT), and CT-free survival for the ITT and NSAI populations are in the Table. Among the patients who discontinued study treatment, 77.3% and 78.1% in the RIB + ET vs PBO + ET arms received a subsequent antineoplastic therapy, respectively, and 12.9% and 26.1% received a subsequent line of CDK4/6i. Additionally there were 15 patients in the PBO arm that crossed over to the RIB arm following unblinding and prior to disease progression. Conclusions: With an extended follow-up of more than 4 years, RIB + ET continued to demonstrate a clinically relevant OS benefit compared with ET alone in pre- or perimenopausal patients with a median OS ~5 years with RIB +ET in HR+/HER2− ABC. A similar benefit with RIB was observed for PFS2, time to CT, and CT-free survival.

ITTNSAI cohortRIB + ETn=335PBO + ETn=337RIB + NSAIn=248PBO + NSAIn=247PFS2Events, n (%)177 (52.8)221 (65.6)131 (52.8)159 (64.4)Median, mo44.231.043.630.4HR (95% CI)0.68 (0.56-0.83)0.69 (0.55-0.87)Time to first CTEvents, n (%)144 (43.0)173 (51.3)107 (43.1)129 (52.2)Median, mo50.936.850.936.0ITT HR(95% CI)0.69 (0.56-0.87)0.66 (0.51-0.85)CT-free survivalEvents, n (%)190 (56.7)236 (70.0)139 (56.0)169 (68.4)Median, mo42.426.442.525.9HR (95% CI)0.67 (0.55-0.81)0.64 (0.51-0.81)

Citation Format: Debu Tripathy, Seock-Ah Im, Marco Colleoni, Fabio Franke, Aditya Bardia, Nadia Harbeck, Sara Hurvitz, Louis Chow, Joohyuk Sohn, Keun Seok Lee, Saul Campos-Gomez, Rafael Villanueva Vazquez, Kyung Hae Jung, K Govind Babu, Paul Wheatley-Price, Michelino De Laurentiis, Young-Hyuck Im, Sherko Kümmel, Nagi El-Saghir, Mei-Ching Liu, Sharonjeet Kaur, Claudia Gasch, Craig Wang, Yongyu Wang, Arunava Chakravartty, Yen-Shen Lu. Updated overall survival (OS) results from the phase III MONALEESA-7 trial of pre- or perimenopausal patients with hormone receptor positive/human epidermal growth factor receptor 2 negative (HR+/HER2−) advanced breast cancer (ABC) treated with endocrine therapy (ET) ± ribociclib [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD2-04.

Abstract OT-28-01: HER2CLIMB-02: A randomized, double-blind, phase 3 study of tucatinib or placebo with T-DM1 for unresectable locally-advanced or metastatic HER2+ breast cancer

Background - Tucatinib (TUC), an oral tyrosine kinase inhibitor (TKI) highly selective for HER2 with minimal inhibition of EGFR, is approved in the US for use in combination with trastuzumab (Tras) and capecitabine for treatment (tx) of adult patients (pts) with metastatic HER2+ breast cancer (MBC), including pts with brain metastases (BM), who have received 1 or more prior anti-HER2-based regimens in the metastatic setting. Ado-trastuzumab emtansine (T-DM1), approved for tx of pts with HER2+ MBC after Tras and a taxane, has led to significant improvements in progression-free survival (PFS) and overall survival (OS). Still, further improvements are needed, including pts with active BM. A phase 1b trial evaluated TUC (300 mg PO BID) with T-DM1 in 50 pts with HER2+ MBC who received prior tx with Tras and a taxane (Borges 2018). Common AEs included nausea (72%), diarrhea (60%), and fatigue (56%); mostly grade 1/2. Median PFS was 8.2 months and the objective response rate (ORR) in pts with measurable disease (n=34) was 47%. Sixty percent of pts treated with TUC + T-DM1 had BM at baseline and showed a brain specific response rate (RECISTv1.1) of 36% in pts with measurable BM. This encouraging clinical activity, including in pts with BM, provides rationale for a randomized trial to further evaluate this combination.

Trial design - HER2CLIMB-02 is a randomized, double-blind, placebo-controlled phase 3 study to evaluate efficacy and safety of TUC + T-DM1 in pts with unresectable locally advanced or metastatic HER2+ breast cancer; ~460 pts will be randomized 1:1 to receive 21-day cycles of TUC (300 mg PO BID) or placebo with T-DM1 (3.6 mg/kg IV). Pts must have had prior tx with Tras and a taxane in any setting, be ≥18 yrs, with an ECOG ≤1 and histologically confirmed HER2+ MBC. Prior tx with any investigational antiHER2 or anti-EGFR agent or HER2 TKI is not permitted. Prior pertuzumab tx is allowed, but not required. Baseline brain MRIs are required for all pts; pts with stable, progressing, or untreated BM not requiring immediate local therapy are eligible. While on tx, radiographic disease evaluations (RECISTv1.1) will occur every 6 weeks for the first 24 weeks, and then every 9 weeks. The primary endpoint is PFS per investigator, with OS and ORR as key secondary endpoints. Enrollment is ongoing in the US (NCT03975647) and planned for Canada, the EU, and the Asia/Pacific region.

Citation Format: Sara Hurvitz, Linda Vahdat, Nadia Harbeck, Antonio C. Wolff, Sara M. Tolaney, Sherene Loi, Norikazu Masuda, Joyce O’Shaughnessy, Cassie Dong, Luke Walker, Evelyn Rustia, Virginia F. Borges. HER2CLIMB-02: A randomized, double-blind, phase 3 study of tucatinib or placebo with T-DM1 for unresectable locally-advanced or metastatic HER2+ breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr OT-28-01.

Abstract PD13-09: Impact of neratinib on outcomes in HER2-positive metastatic breast cancer patients with central nervous system disease at baseline: Findings from the phase 3 NALA trial

Background: The development of central nervous system (CNS) metastases presents a considerable challenge in metastatic breast cancer (MBC) due to the limited availability of evidence-based treatments. Up to 50% of patients with HER2-positive (HER2+) MBC develop CNS metastases during the course of their disease. Neratinib, an irreversible pan-HER tyrosine kinase inhibitor, has demonstrated activity against CNS metastases in HER2+ MBC in two phase 2 studies (NEfERT-T, TBCRC 022) and one phase 3 study (NALA); significant benefits for predefined CNS endpoints were reported in NEfERT-T and confirmed in NALA. Here we present an exploratory analysis of patients from NALA with CNS involvement at enrollment.

Methods: NALA was an international, randomized, open-label, active-controlled, phase 3 study in patients with HER2+ MBC who had received ≥2 lines of HER2-directed therapy in the metastatic setting (ClinicalTrials.gov: NCT01808573). Patients with asymptomatic metastatic brain disease managed with stable doses of corticosteroids for ≥14 days prior to randomization were eligible, whereas patients with symptomatic or unstable brain metastases were excluded. Patients were randomized (1:1 ratio) to neratinib (N; 240 mg qd po) + capecitabine (C; 750 mg/m2 bid po) or lapatinib (L; 1250 mg qd po) + C (1000 mg/m2 bid po). Co-primary endpoints were centrally assessed progression-free survival (PFS) and overall survival (OS). Intervention for symptomatic metastatic CNS disease was a secondary endpoint. CNS disease at baseline was defined as patients with treated or untreated disease in the ‘brain’ assessed by investigator at enrollment. CNS imaging was not mandatory at screening.

Results: Of the 621 patients enrolled in NALA, 101 (16%) had documented baseline CNS disease and 520 (74%) had no CNS disease at baseline. Patients with CNS disease had a lower performance status and were more likely to have hormone receptor-negative disease than those with no CNS disease; no major imbalances of baseline characteristics were noted between treatment arms. Overall, 78 (77%) patients had previously received CNS radiation [whole brain, n=59 (58%); stereotactic, n=17 (17%); unknown, n=2 (2%)], and 5 (5%) patients had undergone CNS surgery. Median treatment duration was 5.7 (IQR 2.8-8.5) months for N, and 3.5 (IQR 2.1-6.9) months for L. PFS, OS, and cumulative incidence of interventions for symptomatic CNS disease are summarized in the table. No new safety signals were detected.

Conclusions: Regardless of the status of CNS metastases at baseline, patients appeared to have better outcomes in the N+C arm compared with the L+C arm.

Table. Efficacy outcomes in patients with and without CNS disease at baselineIntention-to-treat (n=621)CNS metastases at baseline – Yes (n=101)CNS metastases at baseline – No (n=520)N+C (n=307)L+C (n=314)N+C (n=51)L+C (n=50)N+C (n=256)L+C (n=264)PFSaHazard ratio (95% CI)0.76 (0.63–0.93)0.66 (0.41–1.05)0.76 (0.62–0.94)P-value0.00590.07410.0099Restricted mean PFSb, months8.86.67.85.59.06.9Difference, months2.22.32.1OSHazard ratio (95% CI)0.88 (0.72–1.07)0.90 (0.59–1.38)0.85 (0.68–1.06)P-value0.20860.63520.1517Restricted mean OSb, months24.022.216.415.425.623.6Difference, months1.71.02.0Incidence of CNS interventionOverall cumulative incidencec, %22.7629.1940.1347.7919.1624.65P-value0.0430.4300.067aCentrally confirmed; bRestriction prespecified as 24 months for PFS, and 48 months for OS; c % requiring intervention for CNS disease (competing risk model)

Citation Format: Cristina Saura, Larisa Ryvo, Sara Hurvitz, William Gradishar, Beverly Moy, Suzette Delaloge, Sung-Bae Kim, Mafalda Oliveira, Maureen Trudeau, Ming-Shen Dai, Barbara Haley, Ron Bose, Luciana Landeiro, Judith Bebchuk, Aimee Frazier, Kiana Keyvanjah, Richard Bryce, Adam Brufsky. Impact of neratinib on outcomes in HER2-positive metastatic breast cancer patients with central nervous system disease at baseline: Findings from the phase 3 NALA trial [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD13-09.

Abstract PS9-02: Neratinib + capecitabine sustains health-related quality of life (HRQoL) while improving progression-free survival (PFS) in patients with HER2+ metastatic breast cancer and ≥2 prior HER2-directed regimens

Background: The FDA approved neratinib (N), an irreversible pan-HER tyrosine kinase inhibitor, in combination with capecitabine (C) for patients with HER2+ advanced or metastatic breast cancer who have received ≥2 prior HER2-directed regimens in the metastatic setting based on the NALA clinical study, where N+C significantly improved PFS vs. lapatinib (L)+C. Characterizing HRQoL associated with this regimen can help inform treatment decision-making for these patients. The objective of this analysis was to characterize HRQoL among patients with HER2+ metastatic breast cancer from the NALA clinical study.

Methods: NALA was a multinational, randomized, open-label, phase III clinical study of N+C vs. L+C in patients with HER2+ metastatic breast cancer and ≥2 prior HER2-directed regimens. From May 2013 to July 2017, patients were randomized 1:1 to N (240 mg qd) + C (750 mg/m2 bid 14d/21d) with loperamide prophylaxis during the first cycle, or to L (1250 mg qd) + C (1000 mg/m2 bid 14d/21d). HRQoL, a prespecified secondary endpoint of the NALA study, was measured using the EORTC QLQ-C30 and the breast cancer-specific QLQ-BR23 at baseline and every 6 weeks (±3 days) until the end of treatment (data collection through treatment cycle 19, 12.5 months). The QLQ-C30 summary and global health status scores range from 0 (worst) to 100 (best) and the systemic therapy side-effects scores range from 0 (best) to 100 (worst). Patients were included in the analysis for a particular scale if they had a baseline assessment and at least 1 follow-up assessment. For these analyses, a change of ≥10 points was considered to be clinically meaningful. Descriptive statistics summarized observed scores and changes from baseline, Kaplan-Meier and log-rank tests were used for time-to-deterioration (TTD) of ≥10 points and mixed models estimated the change over time for 7 prespecified scales: QLQ-C30 summary score, global health status, physical functioning, fatigue, constipation and diarrhea, and the EORTC QLQ-BR23 systemic therapy side effects subscale. No adjustments for multiplicity were performed.

Results: 621 patients from 28 countries were randomized (307 N+C; 314 L+C). The mean completion rate of the QLQ-C30 over the course of the study was 91% for both treatment arms. Discontinuation due to any treatment-emergent adverse event (TEAE) was lower in the N+C vs. L+C arm (14% vs. 18%). At baseline, the mean (SD) QLQ-C30 summary scores were 79.8 (14.1) for N+C and 79.9 (15.7) for L+C. After 19 treatment cycles, the mean (SD) QLQ-C30 summary scores were similar to baseline scores: 81.8 (16.7) for N+C and 81.3 (15.3) for L+C. There were no differences in TTD of ≥10 points for the QLQ-C30 summary score between treatment arms; the HR for N+C vs. L+C was 0.94 (95% CI 0.63-1.40). All prespecified HRQoL subscales had similar statistically non-significant results for TTD with the exception of diarrhea (HR=1.71; 95% CI 1.32-2.23). The mixed models analyzing change in HRQoL from baseline did not demonstrate persistent declines nor meaningful differences between the treatment arms.

Conclusion: In these results from the NALA study, among patients with HER2+ metastatic breast cancer, at study end and throughout most of the study, there were no differences observed between the two treatment arms in HRQoL scores. HRQoL was sustained over the study period despite the early transient presence of diarrhea in some patients. Discontinuation due to any TEAE was lower in the N+C vs. the L+C arm. These results may help guide healthcare providers, patients and carers in selection of optimal treatment for HER2+ metastatic breast cancer.

Citation Format: Beverly Moy, Mafalda Oliveira, Cristina Saura, William Gradishar, Sung-Bae Kim, Adam Brufsky, Sara Hurvitz, Larisa Ryvo, Daniele Fagnani, Nancy Chan, Sujith R Kalmadi, Paula Silverman, Suzette Delaloge, Richard Bryce, Kiana Keyvanjah, Judith Bebchuk, Bo Zhang, Nina Oestreicher, Ron Bose. Neratinib + capecitabine sustains health-related quality of life (HRQoL) while improving progression-free survival (PFS) in patients with HER2+ metastatic breast cancer and ≥2 prior HER2-directed regimens [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS9-02.

Betrayal Trauma: Impact on Health Professionals

"Second victims" are clinicians who are traumatized after an unanticipated adverse patient event, medical error, or patient-related injury. Less recognized is the profound sense of betrayal and trauma that can occur in the context of patient deception. The implicit patient-healthcare provider contract assumes that patients are truthful with providers so they may obtain accurate diagnoses and effective treatments. Betrayal by deception can feel like a traumatic death; not of a person, but of a previously intimate and trusting relationship. Healthcare professionals are no better at detecting lies than the lay public and hold inaccurate beliefs about detectable signs of deception. Thus, healthcare professionals may be more vulnerable to betrayal by deception than they realize. The 2 clinical cases presented here reveal the ease with which healthcare providers can be misled, emotionally manipulated by individuals who superficially appear to be psychologically healthy and traumatized by betrayal by deception.

Intracranial Efficacy and Survival With Tucatinib Plus Trastuzumab and Capecitabine for Previously Treated HER2-Positive Breast Cancer With Brain Metastases in the HER2CLIMB Trial

PURPOSE

In the HER2CLIMB study, patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer with brain metastases (BMs) showed statistically significant improvement in progression-free survival (PFS) with tucatinib. We describe exploratory analyses of intracranial efficacy and survival in participants with BMs.

PATIENTS AND METHODS

Patients were randomly assigned 2:1 to tucatinib or placebo, in combination with trastuzumab and capecitabine. All patients underwent baseline brain magnetic resonance imaging; those with BMs were classified as active or stable. Efficacy analyses were performed by applying RECIST 1.1 criteria to CNS target lesions by investigator assessment. CNS-PFS (intracranial progression or death) and overall survival (OS) were evaluated in all patients with BMs. Confirmed intracranial objective response rate (ORR-IC) was evaluated in patients with measurable intracranial disease.

RESULTS

There were 291 patients with BMs: 198 (48%) in the tucatinib arm and 93 (46%) in the control arm. The risk of intracranial progression or death was reduced by 68% in the tucatinib arm (hazard ratio [HR], 0.32; 95% CI, 0.22 to 0.48; P < .0001). Median CNS-PFS was 9.9 months in the tucatinib arm versus 4.2 months in the control arm. Risk of death was reduced by 42% in the tucatinib arm (OS HR, 0.58; 95% CI, 0.40 to 0.85; P = .005). Median OS was 18.1 versus 12.0 months. ORR-IC was higher in the tucatinib arm (47.3%; 95% CI, 33.7% to 61.2%) versus the control arm (20.0%; 95% CI, 5.7% to 43.7%; P = .03).

CONCLUSION

In patients with HER2-positive breast cancer with BMs, the addition of tucatinib to trastuzumab and capecitabine doubled ORR-IC, reduced risk of intracranial progression or death by two thirds, and reduced risk of death by nearly half. To our knowledge, this is the first regimen to demonstrate improved antitumor activity against BMs in patients with HER2-positive breast cancer in a randomized, controlled trial.

53. TUCATINIB VS PLACEBO ADDED TO TRASTUZUMAB AND CAPECITABINE FOR PATIENTS WITH PREVIOUSLY TREATED HER2+ METASTATIC BREAST CANCER (MBC) WITH BRAIN METASTASES (BM) (HER2CLIMB)

BACKGROUND

HER2CLIMB (NCT02614794) primary results have been reported previously (Murthy, NEJM 2019). We report results of exploratory efficacy analyses in pts with brain metastases (BM).

METHODS

All HER2+ MBC pts enrolled had a baseline brain MRI. Pts with BM were eligible and randomized 2:1 to receive tucatinib (TUC) or placebo, in combination with trastuzumab and capecitabine. Efficacy analyses were performed by applying RECIST 1.1 to the brain based on investigator evaluation. CNS-PFS and OS were evaluated in BM pts overall. Intracranial (IC) confirmed ORR-IC and DOR-IC were evaluated in BM pts with measurable IC disease. After isolated brain progression, pts could continue study therapy until second progression, and time from randomization to second progression or death was evaluated.

RESULTS

Overall, 291 pts (48%) had BM at baseline: 198 (48%) in the TUC arm and 93 (46%) in the control arm. There was a 68% reduction in risk of CNS-PFS in the TUC arm (HR: 0.32; P&lt;0.0001). Median CNS-PFS was 9.9 mo in the TUC arm vs 4.2 mo in the control arm. Risk of overall death was reduced by 42% in the TUC arm (OS HR: 0.58; P=0.005). Median OS was 18.1 mo vs 12.0 mo. ORR-IC was higher in the TUC arm (47.3%) vs the control arm (20.0%). Median DOR-IC was 6.8 mo vs 3.0 mo. In pts with isolated brain progression who continued study therapy after local treatment (n=30), risk of second progression or death was reduced by 71% (HR: 0.29), and median time from randomization to second progression or death was 15.9 mo vs 9.7 mo, favoring the TUC arm.

CONCLUSIONS

In pts with previously treated HER2+ MBC with BM, TUC in combination with trastuzumab and capecitabine doubled the ORR-IC, reduced risk of IC progression or death by two-thirds and reduced risk of death by nearly half.

Abstract OT2-01-01: Randomized, double-blind, phase 3 study of tucatinib or placebo in combination with T-DM1 for subjects with unresectable locally-advanced or metastatic HER2+ breast cancer

Background: Tucatinib is an orally-available, reversible HER2 small molecule tyrosine kinase inhibitor (TKI) being developed as a novel treatment for patients with HER2+ metastatic breast cancer (mBC), including patients with brain metastases. Two key features of tucatinib are its potency and selectivity for HER2, compared to the epidermal growth factor receptor (EGFR). Ado-trastuzumab emtansine (T-DM1) is approved for the treatment of patients with HER2+ mBC after prior treatment with trastuzumab and a taxane. While treatment with T-DM1 has led to significant improvements in progression-free survival (PFS) and overall survival, further improvements in therapy are needed, especially for patients with active brain metastases. Based upon evidence that dual targeting of HER2 may lead to further improvements in efficacy in mBC, a phase 1b trial enrolled subjects with HER2+ mBC, previously treated with trastuzumab and taxane, to receive tucatinib (300 mg orally [PO] twice a day [BID]) with T-DM1 (Borges et al, 2018). Forty-six percent of these subjects had received prior pertuzumab. The combination of tucatinib with T-DM1 demonstrated a median PFS of 8.2 months (95% CI, 4.8-10.3) and an objective response rate of 47% in subjects with measurable disease. Sixty percent of subjects treated with this combination had baseline brain metastases and showed a brain-specific response rate (using modified RECIST v1.1 criteria) of 36% in subjects with measurable central nervous system disease. Tucatinib with T-DM1 was found to have a tolerable safety profile, the most common adverse events were nausea (72%), diarrhea (60%), and fatigue (56%), with the majority of events being grade 1 or 2. This encouraging clinical activity, including in subjects with brain metastases, provides rationale for a randomized trial to further evaluate this combination.

Study Design: This is a randomized, double-blind, placebo-controlled, international, multicenter, phase 3 study designed to evaluate the efficacy and safety of tucatinib in combination with T-DM1 in subjects with unresectable locally-advanced or metastatic HER2+ breast cancer. Subjects must have had prior treatment with a taxane and trastuzumab in any setting (adjuvant, neoadjuvant, or metastatic). The primary objective of the study is to compare PFS between the treatment arms per investigator assessment, with overall survival as a key secondary endpoint. In this study, subjects must be ≥18 years, with an ECOG of ≤1 and have histologically confirmed HER2+ mBC. Prior treatment with any investigational anti-HER2 or anti-EGFR agent or HER2 TKI agent is not permitted. Prior pertuzumab therapy is allowed, but not required. Subjects with stable, progressing, or untreated brain metastases not requiring immediate local therapy, are eligible for inclusion in the trial.

Approximately 460 subjects will be randomized 1:1 to receive 21-day cycles of either tucatinib (300 mg PO BID) or placebo in combination with T-DM1 (3.6 mg/kg intravenously). Disease response and progression will be assessed using RECIST v1.1. While on study treatment, radiographic disease evaluations will be performed every 6 weeks for the first 24 weeks, and every 9 weeks thereafter. A subset of subjects will participate in a pharmacokinetic substudy.

Citation Format: Sara Hurvitz, Linda Vahdat, Nadia Harbeck, Antonio C Wolff, Sara M Tolaney, Sherene Loi, Norikazu Masuda, Cassie Dong, Luke Walker, Evelyn Rustia, Virginia Borges. Randomized, double-blind, phase 3 study of tucatinib or placebo in combination with T-DM1 for subjects with unresectable locally-advanced or metastatic HER2+ breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr OT2-01-01.

Abstract P4-14-07: Treatment patterns for metastatic hormone receptor-positive breast cancer: Comparing expert and community practice

Background Endocrine therapies and CDK4/6 inhibitors have dramatically improved outcomes for patients with hormone receptor-positive (HR+) metastatic breast cancer (MBC). To help inform treatment decisions among healthcare providers (HCPs) caring for patients with MBC, we have developed and regularly updated an online treatment decision support tool that provides recommendations from multiple breast cancer experts for specifically defined patient scenarios. Here we report data for HR+/HER2- MBC cases entered into the tool since 2016, capturing self-reported practice trends from HCPs compared with matched treatment recommendations from experts. Methods For the most recent MBC treatment tool (published October 2018), 5 breast cancer experts provided treatment consultation for 549 unique MBC case scenarios based on a simplified set of variables: disease phenotype, previous systemic therapy, visceral crisis (yes/no), rate of disease progression, and the presence or absence of germline BRCA1/2 mutations. HCPs used selection menus to enter patient and disease factors based on these variables along with their intended treatment plan. When completed, the experts’ treatment recommendations for that specific patient case were shown to the HCPs at which time they were asked to indicate if the expert recommendations changed their planned treatment. Results From October 2018 through June 2019, 603 HCPs entered 1127 patient case scenarios, including 581 HR+/HER2- MBC cases, in the most recent online tool. A comparison of expert and HCP treatment choices for select HR+/HER2- MBC case scenarios from the October 2016 and October 2018 tool is shown in the Table. In the setting of HR+/HER2- MBC, among those HCPs whose planned treatment differed from the consensus expert recommendation, 55% indicated that they would change their original choice of treatment. Conclusions CDK4/6 inhibitors have had a large impact on expert treatment recommendations for patients with HR+/HER2- MBC. However, data from this online treatment decision support tool suggest ongoing differences in practice between experts and community HCPs in this setting. For many cases entered into the tool, the practice of the majority of HCPs differed from expert consensus (Table). Consensus expert recommendations in this online tool changed the intended treatment plan of many using it and, therefore, can help optimize the care of patients with MBC. A detailed analysis of overall community practice trends for HR+/HER2- MBC along with a comparison of expert and HCP practice for different case scenarios will be presented.

HR+/HER2- MBC Case Scenarios (no visceral crisis)Expert Consensus Recommendation (%)Expert Consensus Recommendation (%)HCP Practice Matched Expert Consensus Recommendation, % (n)HCP Practice Matched Expert Consensus Recommendation, % (n)2016201820162018de novoCDK4/6i + AI (100)CDK4/6i + AI (100)23 (111)32 (188)Previous (neo)adjuvant AICDK4/6i + FULV (92)CDK4/6i + FULV (90)22 (54)17 (77)Previous CDK4/6i + AIFULV (82)FULV ± EVE (92)0 (14)18 (40)Previous AI and CDK4/6i + FulvEVE + EXE (87)EVE + EXE (73)63 (19)28 (18)

Citation Format: Timothy Quill, Sara Hurvitz, Kathy D. Miller, Ruth O'Regan, Tiffany A. Traina, Rachael Andrie, Kevin L. Obholz, Mohammad Jahanzeb. Treatment patterns for metastatic hormone receptor-positive breast cancer: Comparing expert and community practice [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-14-07.

Abstract GS1-01: Tucatinib vs placebo, both combined with capecitabine and trastuzumab, for patients with pretreated HER2-positive metastatic breast cancer with and without brain metastases (HER2CLIMB)

Objectives: The primary analysis from the HER2CLIMB study will describe the efficacy and safety of tucatinib, trastuzumab, and capecitabine, a treatment regimen under investigation for patients (pts) with advanced HER2+ metastatic breast cancer (BC) refractory to standard-of-care regimens.

Rationale: Fifteen to 20% of pts diagnosed with BC annually have overexpression or amplification of the HER2 receptor. While significant advances have been made in the treatment of pts with HER2+ BC, treatment of metastatic disease remains a clinical challenge for which no curative options are available. The management of HER2+ CNS metastases (which occur at any time during the disease course in 30-50% of those with HER2+ metastatic BC) remains an area of unmet clinical need. Tucatinib is an investigational, oral tyrosine kinase inhibitor (TKI) that is highly specific to HER2 with minimal inhibition of the EGFR receptor. In a Phase 1b study, tucatinib plus capecitabine and trastuzumab showed an acceptable toxicity profile and encouraging anti-tumour activity, including in pts with active brain metastases.

Methodology: In this double-blind, international, multicenter study (NCT02614794), 612 pts with locally advanced or metastatic HER2+ BC previously treated with trastuzumab, pertuzumab, and T-DM1 were randomized 2:1 to receive tucatinib (300 mg BID) or placebo, in combination with capecitabine (1000 mg/m2 BID, Days 1–14 of each 21-day cycle) and trastuzumab (6 mg/kg once every 21 days). Pts with newly diagnosed, progressing, or stable brain metastases not requiring immediate local therapy were included. The primary endpoint is PFS per RECIST 1.1 by blinded independent central review for the first 480 pts enrolled. Secondary endpoints, including PFS in pts with brain metastases and OS, will be evaluated in all 612 pts. The primary and key secondary endpoints will be compared between treatment arms using a stratified log rank test; the hazard ratio from Cox regression model will also be reported.

Anticipated Results: Baseline demographics and disease characteristics will be presented by treatment arms. PFS, response rates, and duration of response for pts receiving tucatinib vs placebo will be reported for the first 480 pts. Common AEs and SAEs will be reported for both treatment arms in all treated pts. Secondary objectives, including PFS in pts with brain metastases and OS, may be presented if the data are sufficiently mature.

Citation Format: Rashmi Murthy, Sherene Loi, Alicia Okines, Elisavet Paplomata, Erika Hamilton, Sara Hurvitz, Nancy Lin, Virginia Borges, Vandana Gupta Abramson, Carey Anders, Philippe L Bedard, Mafalda Oliveira, Erik Jakobsen, Thomas Bachelot, Shlomit S Shachar, Volkmar Mueller, Sofia Braga, Francois P Duhoux, Richard Greil, David Cameron, Lisa Carey, Giuseppe Curigliano, Karen Gelmon, Gabriel Hortobagyi, Ian Krop, Sibylle Loibl, Mark Pegram, Dennis Slamon, Maria Corinna Palanca-Wessels, Luke Walker, Wentao Feng, Eric Winer. Tucatinib vs placebo, both combined with capecitabine and trastuzumab, for patients with pretreated HER2-positive metastatic breast cancer with and without brain metastases (HER2CLIMB) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr GS1-01.

Abstract PD2-06: Efficacy of abemaciclib based on genomic alterations detected in baseline circulating tumor DNA from the MONARCH 3 study of abemaciclib plus nonsteroidal aromatase inhibitor

Background: Combination treatments of CDK4 & 6 inhibitors (CDK4 & 6i) with endocrine therapy (ET) have improved outcomes in patients with HR-positive (HR+), HER2-negative (HER2-) advanced breast cancer (ABC). Aside from estrogen receptor positivity (ER+), predictive biomarkers of clinical benefit from CDK4 & 6i in combination with ET remain elusive. We assessed clinical outcomes by genomic alterations detected in baseline circulating tumor DNA (ctDNA) from patients treated with abemaciclib plus a nonsteroidal aromatase inhibitor (NSAI) versus placebo plus NSAI in the Phase 3 study MONARCH 3 (NCT02246621).

Methods: MONARCH 3 randomized 493 postmenopausal women with HR+, HER2- ABC who had no prior systemic therapy in the advanced setting to treatment with abemaciclib plus NSAI or placebo plus NSAI. Biomarker analysis of baseline ctDNA was an exploratory objective; plasma was analyzed by the Guardant360 next-generation sequencing (NGS)-based assay to identify potential tumor-related (i.e., somatic) genomic alterations including point mutations (SNV), indels, amplifications, and fusions in over 70 cancer-related genes. Genomic alterations detected in baseline ctDNA were associated with clinical outcomes including progression-free survival (PFS) and objective response rate (ORR).

Results: Baseline ctDNA results were available for 295 patients (201 abemaciclib; 94 placebo) with 83% of patients harboring one or more detectable genomic alterations. Commonly altered genes of interest (% frequency) detected in baseline ctDNA included: PIK3CA (38%); TP53 (26%); EGFR (15%); FGFR1 (12%); NF1 (12%); MYC (9%); CCND1 (9%); ESR1 (5%).Overall, patients treated with placebo plus NSAI who harbored detectable ctDNA genomic alterations had shorter median PFS compared to patients without detectable genomic alterations, as shown in the Table (14.9 months [95% CI: 11.0-23.1] vs 19.2 months [95% CI 9.4-NR]). Moreover, genomic alterations in EGFR, FGFR1, MYC, and CCND1 were associated with median PFS &lt;12 months with placebo plus NSAI. However, consistent with the intent-to-treat population, the addition of abemaciclib to NSAI benefitted these genomic subgroups, regardless of ctDNA gene alterations. Additional genomic results, including alterations in cell cycle-associated genes, will be presented.

Conclusions: In this exploratory subgroup analysis, the presence of detectable ctDNA genomic alterations was associated with shorter PFS with placebo plus NSAI. Consistently, abemaciclib added to NSAI improved outcomes for genomically identified subgroups. In contrast to prior studies, there was no subgroup (e.g., patients harboring FGFR1 alterations) that did not derive benefit from abemaciclib, supporting the efficacy of abemaciclib, including in difficult to treat tumors. These findings are hypothesis-generating and warrant further investigations in clinical studies of CDK4 & 6i in combination with ET.

TableAbemaciclib + NSAIPlacebo + NSAIEvents, n/NMedian PFS (95% CI)Events, n/NMedian PFS (95% CI)Hazard Ratio (95% CI)OVERALLITT population170 / 32828.2 (23.7 - 33.9)123 / 16514.8 (11.2 - 19.2)0.52 (0.42 - 0.66)TR population93 / 20138.7 (31.1 - NR)71 / 9416.5 (11.7 - 23.1)0.45 (0.33 - 0.61)Any Gene AlterationDetected83 / 16634.1 (27.2 - 40.0)62 / 7914.9 (11.0 - 23.1)0.47 (0.34 - 0.66)Not detected10 / 35NR (36.4 - NR)9 / 1519.2 (9.40 - NR)0.31 (0.13 - 0.78)TP53Detected29 / 5327.0 (14.1 - NR)19 / 2315.4 (5.7 - 30.4)0.53 (0.30 - 0.95)Not detected64 / 14839.9 (34.1 - NR)52 / 7117.5 (11.7 - 24.2)0.42 (0.29 - 0.60)EGFRDetected10 / 26NR (32.4 - NR)16 / 1710.9 (2.1 - 24.7)0.20 (0.09 - 0.47)Not detected83 / 17536.4 (27.7 - NR)55 / 7717.6 (14.6 - 25.5)0.52 (0.37 - 0.73)FGFR1Detected15 / 2532.8 (10.1 - NR)10 / 117.6 (1.9 - 15.4)0.37 (0.16 - 0.85)Not detected78 / 17639.9 (31.1 - NR)61 / 8319.2 (14.6 - 26.5)0.45 (0.32 - 0.63)NF1Detected10 / 2435.9 (27 - NR)8 / 1014.6 (1.6 - 33.4)0.33 (0.13 - 0.84)Not detected83 / 17738.7 (30.8 - NR)63 / 8417.5 (11.7 - 24.2)0.47 (0.33 - 0.65)MYCDetected11 / 1720.1 (5.5 - NR)9 / 106.5 (1.2 - 15.7)0.33 (0.13 - 0.86)Not detected82 / 18438.9 (32.9 - NR)62 / 8419.2 (14.6 - 26.5)0.45 (0.32 - 0.63)CCND1Detected8 / 1632.8 (5.5 - NR)10 / 107.2 (3.6 - 9.0)0.28 (0.10 - 0.77)Not detected85 / 18538.7 (31.1 - NR)61 / 8417.6 (14.6 - 25.5)0.48 (0.34 - 0.67)n = number of patients with events; N = total number of patients in the corresponding population and treatment arm; NR = not reached. TR population consists of patients in the ITT population from whom a valid baseline ctDNA result has been obtained.

Citation Format: Matthew P Goetz, J. Thaddeus Beck, Mario Campone, Sara Hurvitz, Seock-Ah Im, Stephen Johnston, Antonio Llombart-Cussac, Miguel Martin, Joohyuk Sohn, Masakazu Toi, Lacey M Litchfield, Hillary T Graham, Hong Wang, Sameera R Wijayawardana, Valerie M Jansen, Angelo Di Leo. Efficacy of abemaciclib based on genomic alterations detected in baseline circulating tumor DNA from the MONARCH 3 study of abemaciclib plus nonsteroidal aromatase inhibitor [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr PD2-06.

Abstract P1-18-01: Risk of recurrence and death in patients with early HER2-positive breast cancer who achieve a pathological complete response (pCR) after different types of HER2-targeted therapy: A retrospective exploratory analysis

Background: The current standard of care for patients achieving a pCR after HER2-targeted therapy plus chemotherapy in the neoadjuvant setting is to continue HER2-targeted therapy in the adjuvant setting. The aim of this exploratory data analysis is to report the risk of recurrence and death after neoadjuvant systemic therapy in Roche-sponsored neoadjuvant trials in patients with HER2-positive early breast cancer who achieved a pCR.

Methods: Data from the HannaH (NCT00950300), NeoSphere (NCT00545688), TRYPHAENA (NCT00976989), BERENICE (NCT02132949), and KRISTINE (NCT02131064) studies were pooled. Neoadjuvant → adjuvant therapeutic regimens analyzed were trastuzumab → trastuzumab (H→H), pertuzumab plus trastuzumab → trastuzumab (PH→H), and pertuzumab plus trastuzumab → pertuzumab plus trastuzumab (PH→PH). pCR was defined as the absence of residual invasive cancer in the resected breast specimen and in the axillary lymph nodes (ypT0/Tis ypN0) after neoadjuvant systemic therapy. Event-free survival (EFS) was defined as the time from the date of randomization to the date of disease recurrence or progression (local, regional, distant, or contralateral) or death due to any cause. EFS rates were estimated using the Kaplan-Meier method. A Cox regression model was used to explore factors associated with EFS.

Results: 1764 patients were included in the analysis. The median duration of follow up was shorter in the PH→PH group compared to the PH→H and H→H groups (Table). Overall, patients with a pCR had an increased EFS probability compared to those with residual disease (unadjusted hazard ratio=0.33; 95% confidence interval [CI]: 0.25– 0.43]), and this was maintained in patients stratified by hormone receptor status and disease stage. The 3-year EFS rates in patients who achieved a pCR were 87% (95% CI: 82%–90%) in the H→H group, 92% (95% CI: 87%–95%) in the PH→H group, and 95% (95% CI: 90%–97%) in the PH→PH group.

Conclusions: Overall, patients who attained a pCR have a better long-term outcome compared to those with residual disease, regardless of ER status or clinical stage. Some patients who achieved a pCR still had a risk of relapse. A limitation of this exploratory data analysis was the smaller number of patients with stage III disease at baseline and shorter follow-up in the PH→PH group compared to the other groups.

Overall(N=1764)H→H (HannaH; NeoSPHERE)(n=703)PH→H (NeoSPHERE; TRYPHAENA)(n=439)PH→PH (BERENICE; KRISTINE)(n=622)Median Duration of Follow-up (months)42.067.961.122.3Disease StageStage II934 (52.9)285 (40.5)204 (46.5)445 (71.5)Stage III806 (45.7)397 (56.5)235 (53.5)174 (28.0)Hormone Receptor StatusPositive783 (44.4)328 (46.7)223 (50.8)232 (37.3)Negative963 (54.6)372 (52.9)215 (49.0)376 (60.5)Unknown18 (1.0)3 (0.4)1 (0.2)14 (2.3)pCR status773 (43.8)236 (33.6)185 (42.1)352 (56.6)Type of recurrence in patients who achieved a pCRDistant recurrence41 (5.3)26 (11.0)10 (5.4)5 (1.4)Local recurrence17 (2.2)12 (5.1)5 (2.7)0Regional recurrence6 (0.8)3 (1.3)2 (1.1)1 (0.3)New contralateral breast cancer2 (0.3)2 (0.8)00

Citation Format: Sandra M Swain, Harrison Macharia, Javier Cortes, Chau Dang, Luca Gianni, Sara Hurvitz, Christian Jackisch, Andreas Schneeweiss, Dennis Slamon, Pinuccia Valagussa, Yolande du Toit, Dominik Heinzmann, Adam Knott, Chunyan Song, Patricia Cortazar. Risk of recurrence and death in patients with early HER2-positive breast cancer who achieve a pathological complete response (pCR) after different types of HER2-targeted therapy: A retrospective exploratory analysis [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-18-01.

Abstract P1-19-06: Patient-reported outcomes, including work productivity, from the MONALEESA-7 trial of ribociclib plus endocrine therapy in patients with HR+/HER2− advanced breast cancer

Background: MONALEESA-7 is a Phase III study (NCT02278120) and the only dedicated trial of endocrine therapy (ET) ± a cyclin-dependent kinase 4/6 inhibitor in premenopausal patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2−) advanced breast cancer (ABC). The study demonstrated that the addition of ribociclib (RIB) to a nonsteroidal aromatase inhibitor (NSAI) or tamoxifen (TAM) + goserelin (GOS) significantly extended both progression-free survival (PFS; hazard ratio, 0.55; Tripathy D et al. Lancet Oncol. 2018) and overall survival (OS; hazard ratio, 0.71; Im S-A et al. N Engl J Med. 2019). Health-related quality of life (HRQOL) and work productivity are other important aspects of clinical benefit, especially in the premenopausal population. We present analyses of QOL and work productivity from MONALEESA-7. Methods: Premenopausal or perimenopausal patients with HR+/HER2− ABC were treated with RIB or placebo (PBO) + GOS with either an NSAI (letrozole or anastrozole) or TAM. A secondary endpoint was evaluation of patient-reported outcomes (PROs) for HRQOL using the European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life questionnaire core 30 (QLQ-C30). Assessments included global health status as well as social, emotional, and physical functioning. Description of Work Productivity and Activity Impairment (WPAI) was an exploratory endpoint and was measured using the WPAI Questionnaire: General Health (WPAI:GH; V2.0). Results: Time to deterioration (TTD) ≥ 10% in EORTC QLQ-C30 global health status was prolonged with RIB vs PBO (median, 35.8 vs 23.3 months; hazard ratio, 0.665 [95% CI, 0.517-0.855]). TTD ≥ 10% in emotional functioning was also prolonged with RIB vs PBO (hazard ratio, 0.636 [95% CI, 0.488-0.828]), as was TTD ≥ 10% in social functioning (hazard ratio, 0.813 [95% CI, 0.610-1.084]) and TTD ≥ 10% in physical functioning (hazard ratio, 0.715 [95% CI, 0.526-0.972]). Compliance rates with the WPAI:GH were &gt; 99% at baseline and &gt; 98% at the end of treatment. Neither arm had an increase from baseline to the end of treatment in mean percentage of work missed due to overall health. Change in percent activity impairment due to overall health was comparable between treatment arms, as were change in percent impairment while working due to overall health and percent overall work impairment due to overall health. The trends observed with RIB vs PBO in the EORTC QLQ-C30 and WPAI:GH in the overall population were generally similar in the NSAI cohort. Conclusions: WPAI and global health are important considerations in the premenopausal patient population. Analysis of PROs demonstrated that TTD ≥ 10% in global health status and emotional functioning were prolonged with RIB vs PBO. Social and physical functioning were maintained in both treatment arms. Results in various WPAI domains demonstrated that productivity was also maintained in both groups. These QOL and WPAI results, in addition to the significantly longer PFS and OS results with RIB vs PBO, indicate a substantial clinical benefit with RIB treatment in premenopausal patients with HR+/HER2− ABC.

Citation Format: Nadia Harbeck, Sara Hurvitz, Aditya Bardia, Fabio Franke, K. Gonvind Babu, Paul Wheatley-Price, Young-Hyuck Im, Kadri Altundag, Antonia Ridolfi, David Chandiwana, Brad Lanoue, Lakshmi Menon, Debu Tripathy. Patient-reported outcomes, including work productivity, from the MONALEESA-7 trial of ribociclib plus endocrine therapy in patients with HR+/HER2− advanced breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-19-06.

Everolimus Plus Exemestane vs Everolimus or Capecitabine Monotherapy for Estrogen Receptor-Positive, HER2-Negative Advanced Breast Cancer: The BOLERO-6 Randomized Clinical Trial

Importance

Everolimus plus exemestane and capecitabine are approved second-line therapies for advanced breast cancer.

Objective

A postapproval commitment to health authorities to estimate the clinical benefit of everolimus plus exemestane vs everolimus or capecitabine monotherapy for estrogen receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer.

Design

Open-label, randomized, phase 2 trial of treatment effects in postmenopausal women with advanced breast cancer that had progressed during treatment with nonsteroidal aromatase inhibitors.

Interventions

Patients were randomized to 3 treatment regimens: (1) everolimus (10 mg/d) plus exemestane (25 mg/d); (2) everolimus alone (10 mg/d); and (3) capecitabine alone (1250 mg/m2 twice daily).

Main Outcomes and Measures

Estimated hazard ratios (HRs) of progression-free survival (PFS) for everolimus plus exemestane vs everolimus alone (primary objective) or capecitabine alone (key secondary objective). Safety was a secondary objective. No formal statistical comparisons were planned.

Results

A total of 309 postmenopausal women were enrolled, median age, 61 years (range, 32-88 years). Of these, 104 received everolimus plus exemestane; 103, everolimus alone; and 102, capecitabine alone. Median follow-up from randomization to the analysis cutoff (June 1, 2017) was 37.6 months. Estimated HR of PFS was 0.74 (90% CI, 0.57-0.97) for the primary objective of everolimus plus exemestane vs everolimus alone and 1.26 (90% CI, 0.96-1.66) for everolimus plus exemestane vs capecitabine alone. Between treatment arms, potential informative censoring was noted, and a stratified multivariate Cox regression model was used to account for imbalances in baseline characteristics; a consistent HR was observed for everolimus plus exemestane vs everolimus (0.73; 90% CI, 0.56-0.97), but the HR was closer to 1 for everolimus plus exemestane vs capecitabine (1.15; 90% CI, 0.86-1.52). Grade 3 to 4 adverse events were more frequent with capecitabine (74%; n = 75) vs everolimus plus exemestane (70%; n = 73) or everolimus alone (59%; n = 61). Serious adverse events were more frequent with everolimus plus exemestane (36%; n = 37) vs everolimus alone (29%; n = 30) or capecitabine (29%; n = 30).

Conclusions and Relevance

These findings suggest that everolimus plus exemestane combination therapy offers a PFS benefit vs everolimus alone, and they support continued use of this therapy in this setting. A numerical PFS difference with capecitabine vs everolimus plus exemestane should be interpreted cautiously owing to imbalances among baseline characteristics and potential informative censoring.

Trial Registration

ClinicalTrials.gov identifier: NCT01783444.

Overall Survival with Ribociclib plus Endocrine Therapy in Breast Cancer

BACKGROUND

An earlier analysis of this phase 3 trial showed that the addition of a cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor to endocrine therapy provided a greater benefit with regard to progression-free survival than endocrine therapy alone in premenopausal or perimenopausal patients with advanced hormone-receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer. Here we report the results of a protocol-specified interim analysis of the key secondary end point of overall survival.

METHODS

We randomly assigned patients to receive either ribociclib or placebo in addition to endocrine therapy (goserelin and either a nonsteroidal aromatase inhibitor or tamoxifen). Overall survival was evaluated with the use of a stratified log-rank test and summarized with the use of Kaplan-Meier methods.

RESULTS

A total of 672 patients were included in the intention-to-treat population. There were 83 deaths among 335 patients (24.8%) in the ribociclib group and 109 deaths among 337 patients (32.3%) in the placebo group. The addition of ribociclib to endocrine therapy resulted in significantly longer overall survival than endocrine therapy alone. The estimated overall survival at 42 months was 70.2% (95% confidence interval [CI], 63.5 to 76.0) in the ribociclib group and 46.0% (95% CI, 32.0 to 58.9) in the placebo group (hazard ratio for death, 0.71; 95% CI, 0.54 to 0.95; P = 0.00973 by log-rank test). The survival benefit seen in the subgroup of 495 patients who received an aromatase inhibitor was consistent with that in the overall intention-to-treat population (hazard ratio for death, 0.70; 95% CI, 0.50 to 0.98). The percentage of patients who received subsequent antineoplastic therapy was balanced between the groups (68.9% in the ribociclib group and 73.2% in the placebo group). The time from randomization to disease progression during receipt of second-line therapy or to death was also longer in the ribociclib group than in the placebo group (hazard ratio for disease progression or death, 0.69; 95% CI, 0.55 to 0.87).

CONCLUSIONS

This trial showed significantly longer overall survival with a CDK4/6 inhibitor plus endocrine therapy than with endocrine therapy alone among patients with advanced hormone-receptor-positive, HER2-negative breast cancer. No new concerns regarding toxic effects emerged with longer follow-up. (Funded by Novartis; MONALEESA-7 ClinicalTrials.gov number, NCT02278120.).

Abstract CT141: Genetic landscape of premenopausal HR+/HER2- advanced breast cancer (ABC) based on comprehensive circulating tumor DNA analysis and association with clinical outcomes in the Phase III MONALEESA-7 trial

Background: The genetic landscape of premenopausal hormone receptor-positive (HR+) ABC is not well understood. The Phase III MONALEESA-7 study (NCT02278120), the first trial of endocrine therapy ± a cyclin-dependent kinase 4/6 inhibitor for premenopausal patients (pts) with HR+/human epidermal growth factor receptor 2-negative (HER2-) ABC, demonstrated that the addition of ribociclib (RIB) to a nonsteroidal aromatase inhibitor (NSAI) or tamoxifen (TAM) + goserelin (GOS) significantly extended progression-free survival (PFS; Tripathy D, et al. Lancet Oncol. 2018). We conducted a comprehensive ctDNA genomic analysis from MONALEESA-7.

Methods: Premenopausal pts with HR+/HER2- ABC were randomized 1:1 to RIB or placebo (PBO) + NSAI (letrozole [LET] or anastrozole) or TAM + GOS. Plasma samples for ctDNA analysis were collected at baseline and end of treatment. ctDNA was analyzed using next-generation sequencing (targeted panel of 550 genes).

Results: Among the 489 pts with ctDNA analyzed at baseline, the most common alterations were in PIK3CA (28%), TP53 (19%), CCND1 (11%), MYC (8%), and GATA3 (8%). Poorer prognosis in both treatment groups was most evident in patients with TP53 and MYC alterations. A PFS treatment effect in favor of RIB was noted in all subsets, independent of biomarker status (Table). However, based on HR, a trend for more pronounced benefit with RIB + NSAI/TAM + GOS was observed in pts with altered CCND1, GATA3, and genes involved in receptor tyrosine kinase signaling.

Conclusions: RIB + NSAI/TAM + GOS provided PFS benefit irrespective of baseline biomarker alteration status and represents recommended first-line therapy for pts with premenopausal HR+/HER2- ABC. The genetic landscape of premenopausal ABC might modulate the magnitude of therapeutic benefit; these novel findings require confirmation in additional biomarker studies.

RIB + NSAI/TAM + GOSPBO + NSAI/TAM + GOSEvents, n/NPFS, median monthsEvents, n/NPFS, median, monthsHRa (95% CI)PIK3CAWT68/18024.6798/17012.190.45 (0.33-0.62)Alt38/6914.7546/7012.850.57(0.36-0.9)TP53WT78/20324.67109/19412.980.48(0.36-0.65)Alt28/469.2335/467.160.47(0.27-0.82)CCND1WT91/22122.11126/21712.880.52(0.39-0.68)Alt15/2811.2718/235.520.21(0.08-0.54)MYCWT90/22924.67125/22112.880.49(0.37-0.65)Alt16/207.3419/197.160.57(0.25-1.31)GATA3WT96/22622.11131/22212.850.52(0.39-0.68)Alt10/23NA13/185.520.18(0.05-0.62)Receptor tyrosine kinasesbWT76/19827.53114/20614.520.5(0.37-0.67)Alt30/5114.5530/345.650.26(0.14-0.47)8p11.23cWT84/21523.03124/21412.780.47(0.36-0.63)Alt22/3412.5220/269.130.51(0.26-1)8p11.23, chromosome 8, short arm, region 11.23; alt, alteration; CCND1, cyclin D1; CI, confidence interval; GATA3, GATA binding protein 3; GOS, goserelin; NA, not applicable; NSAI, nonsteroidal aromatase inhibitor; MYC, MYC proto-oncogene, bHLH transcription factor; PBO, placebo; PFS, progression-free survival; PIK3CA, phosphatidylinositol 4,5-bisphosphate 3-kinase catalytic subunit α; RIB, ribociclib; TAM, tamoxifen; TP53, tumor protein p53; WT, wild type.a HR for PFS of RIB vs PBO. b Receptor tyrosine kinase genes include EGFR, ERBB2, ERBB3, ERBB4, FGFR1, IGF1, IGF1R, KDR, KIT, PDGFRA, PDGFRB, and VEGFA. c Includes FGFR1, WHSC1L1, and ZNF703.

Citation Format: Aditya Bardia, Faye Su, Nadia Solovieff, Seock-Ah Im, Joohyuk Sohn, Keun Seok Lee, Saul Campos-Gomez, Kyung Hae Jung, Rafael Villanueva Vazquez, Yen-Shen Lu, Fabio Franke, Sara Hurvitz, Nadia Harbeck, Louis Chow, Karen Rodriguez Lorenc, Tetiana Taran, Naveen Babbar, Debu Tripathy. Genetic landscape of premenopausal HR+/HER2- advanced breast cancer (ABC) based on comprehensive circulating tumor DNA analysis and association with clinical outcomes in the Phase III MONALEESA-7 trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT141.

Abstract CT015: Phase I dose-escalation study of the allosteric AKT inhibitor BAY 1125976 in advanced solid cancer

This open-label, phase I first-in-human study (NCT01915576) of BAY 1125976, a highly specific and potent allosteric inhibitor of AKT1/2, was conducted to evaluate the safety, pharmacokinetics, and maximum tolerated dose (MTD) of BAY 1125976 in patients with advanced solid tumors. A dose expansion in hormone receptor (HR) positive metastatic breast cancer (MBC) patients, enriched for patients harboring the AKT1E17K mutation, was included to evaluate the clinical benefit at the recommended Phase II dose (R2D).79 patients (including 39 MBC patients) were enrolled. Mean age was 56.7 years and 61 (77.2%) patients were female. All patients, except one, had received ≥1 prior line of systemic anticancer therapy. Response was measured using RECIST v.1.1.Oral dose escalation was initiated with a continuous once daily (OD) dosing (21 days/cycle), starting with a liquid formulation for the first two dose steps (10 mg and 20 mg OD) and bridging to a tablet formulation for further dose steps (40 mg, 80mg and 120mg OD). Based on toxicity assessment during cycle 1, and additional pharmacokinetic and pharmacodynamic (p-AKT, p-PRAS40 in platelet rich plasma) data, a separate dose escalation using twice daily (BID) dosing tested 40 mg, 60mg and 80mg BID, respectively. The following dose limiting toxicities (DLT) occurred: At 120 mg OD, grade 3 and 4 liver enzyme elevation in two out of 6 patients (2/6) and grade 3 alkaline phosphatase elevation in one patient; at 80mg BID, grade 3 liver enzyme elevation in two out of 4 patients and grade 3 hyperglycemia in one patient. After dose de-escalation according to the continuous reassessment method based study design at 60 mg BID, two out of 6 patients experienced grade 3 liver enzyme elevation. The MTD of BAY 1125976 was determined as 80 mg OD and 60 mg BID, respectively. 28 patients with HR+ MBC were enrolled in the expansion cohort using BAY 1125976 60 mg BID, including nine patients with the AKT1E17K mutation.Pharmacological inhibition of AKT1/2 as shown by inhibition of p-AKT and p-PRAS40 was seen in platelet rich plasma samples. However, among the 78 patients evaluable for response, only 1 (1%) patient with HR+ MBC (AKT1 wild-type) had a partial response (PR), 30 (38%) patients had stable disease (SD) and 38 (49%) patients had progressive disease as best response (data missing from 9 patients). Among 43 patients treated at the R2D, CBR was 27.9%. AKT1E17K mutation status was not associated with tumor response. Molecular characterization of archived tumor samples revealed additional mutations (e.g. PIK3CA, BRCA1/2, KRAS, MYC or FGFR1/2), which may have influenced therapeutic response.In conclusion: Tolerable doses of BAY 1125976 resulted in inhibition of AKT1/2 signaling in platelet rich plasma samples. A notable CBR of 27.9% was achieved at the R2D of BAY 1125976; however PR was seen in only 1 patient with HR+ MBC. Clinical benefit did not correlate with presence of AKT mutations.

Citation Format: Andreas Schneeweiss, Dagmer Hess, Markus Joerger, Andrea Varga, Stacy Moulder, Cynthia Ma, Ian Krop, Sara Hurvitz, Christine Rentzsch, Marion Rudolph, Oliver Boix, Gary Wilkinson, Lars Lindbom, Eleni Lagkadinou, Matthias Ocker. Phase I dose-escalation study of the allosteric AKT inhibitor BAY 1125976 in advanced solid cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT015.

A Phase II Randomized Study of Neoadjuvant Letrozole Plus Alpelisib for Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Breast Cancer (NEO-ORB)

PURPOSE

Addition of alpelisib to fulvestrant significantly extended progression-free survival in PIK3CA-mutant, hormone receptor-positive (HR+) advanced/metastatic breast cancer in the phase III SOLAR-1 study. The combination of alpelisib and letrozole also had promising activity in phase I studies of HR+ advanced/metastatic breast cancer. NEO-ORB aimed to determine whether addition of alpelisib to letrozole could increase response rates in the neoadjuvant setting.Patients and Methods: Postmenopausal women with HR+, human epidermal growth factor receptor 2-negative, T1c-T3 breast cancer were assigned to the PIK3CA-wild-type or PIK3CA-mutant cohort according to their tumor PIK3CA status, and randomized (1:1) to 2.5 mg/day letrozole with 300 mg/day alpelisib or placebo for 24 weeks. Primary endpoints were objective response rate (ORR) and pathologic complete response (pCR) rate for both PIK3CA cohorts.

RESULTS

In total, 257 patients were assigned to letrozole plus alpelisib (131 patients) or placebo (126 patients). Grade ≥3 adverse events (≥5% of patients) in the alpelisib arm were hyperglycemia (27%), rash (12%), and maculo-papular rash (8%). The primary objective was not met; ORR in the alpelisib versus placebo arm was 43% versus 45% and 63% versus 61% in the PIK3CA-mutant and wild-type cohorts, respectively. pCR rates were low in all groups. Decreases in Ki-67 were similar across treatment arms and cohorts. In PIK3CA-mutant tumors, alpelisib plus letrozole treatment induced a greater decrease in phosphorylated AKT versus placebo plus letrozole.

CONCLUSIONS

In contrast to initial results in advanced/metastatic disease, addition of alpelisib to 24-week neoadjuvant letrozole treatment did not improve response in patients with HR+ early breast cancer.

Abstract P6-18-04: Ribociclib with a non-steroidal aromatase inhibitor and goserelin in premenopausal women with hormone receptor-positive, HER2-negative advanced breast cancer: MONALEESA-7 age subgroup analysis

Background: Younger patients (pts) with breast cancer may experience more aggressive disease and are more likely to die from their cancer vs older pts. In the Phase III MONALEESA-7 study (NCT02278120), the addition of ribociclib (RIB; cyclin-dependent kinase 4/6 inhibitor) to a non-steroidal aromatase inhibitor (NSAI) or tamoxifen (TAM) + goserelin significantly prolonged progression-free survival (PFS) in premenopausal women with hormone receptor-positive (HR+), HER2-negative (HER2–) advanced breast cancer (ABC; hazard ratio 0.553; p&lt;0.0001). RIB treatment benefit was observed irrespective of endocrine partner (NSAI or TAM). Here we report results from a MONALEESA-7 subgroup analysis in pts aged &lt;40 yrs and ≥40 yrs who received RIB or placebo (PBO) in combination with an NSAI + goserelin.

Methods: Pre- or perimenopausal women with HR+, HER2– ABC who had received no prior endocrine therapy and ≤1 line of chemotherapy for ABC were enrolled. Of the 672 pts randomized, 495 (74%) received RIB (600 mg/day, 3-weeks-on/1-week-off) or PBO + an NSAI (letrozole [2.5 mg/day] or anastrozole [1 mg/day]) and goserelin (3.6 mg every 28 days). The primary endpoint was locally assessed PFS; secondary endpoints included overall response rate (ORR), clinical benefit rate (CBR), and safety. A prespecified subgroup analysis was performed in pts aged &lt;40 yrs and ≥40 yrs.

Results: A total of 144 pts were aged &lt;40 yrs (RIB vs PBO arm: 78 vs 66) and 351 were aged ≥40 yrs (170 vs 181). As of August 20, 2017, in the RIB vs PBO arms, treatment was ongoing in 50% vs 23% of pts aged &lt;40 yrs and 54% vs 43% of pts aged ≥40 yrs; disease progression was the most common reason for treatment discontinuation (&lt;40 yrs: 37% vs 68%; ≥40 yrs: 35% vs 44%). Median PFS was prolonged in the RIB vs PBO arms both in pts aged &lt;40 yrs (not reached vs 10.8 months; hazard ratio 0.435; 95% confidence interval [CI] 0.276–0.686) and in pts aged ≥40 yrs (27.5 vs 19.1 months; hazard ratio 0.625; 95% CI 0.449–0.870). In pts with measurable disease, the ORR (RIB vs PBO arm) was 49% vs 32% in pts aged &lt;40 yrs and 51% vs 38% in pts aged ≥40 yrs; CBR was 81% vs 61% and 82% vs 65%, respectively. The most common Grade 3 adverse events (AEs; ≥5% of pts in either arm; RIB vs PBO arm) were neutropenia (&lt;40 yrs: 47% vs 5%; ≥40 yrs: 58% vs 3%), leukopenia (&lt;40 yrs: 18% vs 2%; ≥40 yrs: 14% vs 1%), diarrhea (&lt;40 yrs: 5% vs 0; ≥40 yrs: 1% vs 0), and increased alanine aminotransferase (&lt;40 yrs: 4% vs 2%; ≥40 yrs: 5% vs 1%); neutropenia was the only Grade 4 AE occurring in ≥5% of pts in either arm (&lt;40 yrs: 15% vs 0; ≥40 yrs: 8% vs 1%). New post-baseline QTcF &gt;480 ms (RIB vs PBO arm) occurred in 3% vs 2% of pts aged &lt;40 yrs and 7% vs 1% of pts aged ≥40 yrs.

Conclusions: Consistent treatment benefit was observed with RIB + NSAI vs PBO + NSAI in premenopausal women with HR+, HER2– ABC irrespective of age. RIB + NSAI had a manageable safety profile in pts aged &lt;40 yrs and in those aged ≥40 yrs, with a safety profile similar to that observed in the full study population.

Citation Format: Tripathy D, Campos-Gomez S, Lu Y-S, Franke F, Bardia A, Wheatley-Price P, Cruz FM, Hegg R, Cardoso F, Gaur A, Kong O, Diaz-Padilla I, Miller M, Hurvitz S. Ribociclib with a non-steroidal aromatase inhibitor and goserelin in premenopausal women with hormone receptor-positive, HER2-negative advanced breast cancer: MONALEESA-7 age subgroup analysis [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-18-04.

Abstract P6-17-11: The small molecule inhibitor of HER2, tucatinib, has potent and highly selective activity in preclinical modes of HER2-driven cancer

Background: Pharmacologically targeting the HER2 oncoprotein provides clinical benefit for patients with HER2-amplified cancers. However, a significant number of patients do not respond to the currently approved HER2-targeted therapies, despite carrying the HER2-alteration. Small molecule inhibitors of HER2, that target other receptor tyrosine kinases such as EGFR (i.e. lapatinib), are approved and provide some clinical benefit but are often associated with increased toxicity. Tucatinib (ARRY-380) is an orally available, potent, highly selective small molecule inhibitor of the HER2 kinase. In this study, we assessed the in vitroand in vivoactivity of tucatinib, relative to approved HER2-targeting molecules, in a panel of molecularly characterized breast cancer cell lines.

Materials and Methods:The growth inhibitory activity of tucatinib, trastuzumab and lapatinib were evaluated in a panel of 48 breast cancer cell lines molecularly characterized at baselineby genomic (array-CGH) and proteomic (Reverse Phase Protein Array; RPPA) profiling. IC50values for tucatinib and lapatinibwere determined from direct cell counts using a Cellavista Cell Imaging System. Trastuzumab activity was measured as % inhibition of cell growth at fixed concentrations. In vivoefficacy of tucatinib was assessed in cell line xenograft models of HER2+/ER- and HER2+/ER+ breast cancers as a single agent or in combination with targeted therapies for breast cancer.

Results: A broad range of IC50values (3.2nM to &gt;10μM), was seen for tucatinib with a high degree of selectivity for the HER2-amplfied sub-type. High levels of total and phosphorylated HER2 (pHER2) accompanied by high levels of pEGFR and pHER3 enriched for sensitivity to tucatinib, confirming that HER2-driven cancers may be uniquely sensitive to tucatinib. The response profile for lapatinib was less clean, with responses also observed in HER2-low/EGFR-high cell lines. Sensitivity to tucatinib was also observed in HER2-amplified cell lines that were either de novoor acquired resistant to trastuzumab. Single agent tucatinib induced tumor regressions in a xenograft model of HER2+/ER+ breast cancer. Tumor regressions were further enhanced by combination with trastuzumab. The combination of tucatinib plus trastuzumab was as efficacious and better tolerated than trastuzumab plus docetaxel or trastuzumab plus pertuzumab plus docetaxel. The triple combination of tucatinib plus hormonal blockade (fulvestrant) and CDK4/6 inhibition (abemaciclib) also induced robust tumor regressions, without significant body weight loss.

Discussion: These preclinical data highlight the potential of the HER2-selective small molecule inhibitor, tucatinib, to provide benefit to patients with HER2-amplifed cancers. Furthermore, our biomarker analysis of response to tucatinib has identified a HER2-driven signature within the HER2-amplfied sub-type that selects for sensitivity to tucatinib. Selecting patients based on this profile may further enrich for individuals most likely to benefit from tucatinib-based therapies.

Citation Format: O'Brien NA, Conklin D, McDermott M, Luo T, Ayala R, Issakhanian S, Salgar S, Hurvitz S, Slamon DJ. The small molecule inhibitor of HER2, tucatinib, has potent and highly selective activity in preclinical modes of HER2-driven cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-11.

Abstract P6-18-05: First-line ribociclib + endocrine therapy in hormone receptor-positive, HER2-negative advanced breast cancer: A pooled efficacy analysis

Background: In three separate Phase III randomized, placebo-controlled trials, ribociclib (RIB; cyclin-dependent kinase 4/6 inhibitor) + various endocrine therapy (ET) partners prolonged progression-free survival (PFS) vs placebo (PBO) + ET in patients (pts) with hormone receptor-positive (HR+), HER2-negative (HER2–) advanced breast cancer (ABC). Here we further evaluate the efficacy of RIB-based regimens of interest (i.e. with a non-steroidal aromatase inhibitor [NSAI] or fulvestrant [FUL]) in pts who were ET-naïve in the ABC setting, using pooled data from three Phase III trials: MONALEESA (ML)-2 (NCT01958021; all pts), ML-3 (NCT02422615; no prior ET for ABC subgroup only), and ML-7 (NCT02278120; RIB + NSAI subgroup only).

Methods: Postmenopausal pts with no prior ET for ABC received RIB (600 mg/day; 3-weeks-on/1-week-off) or PBO + either letrozole (2.5 mg/day) in ML-2 or FUL (500 mg every 28 days, with an additional dose on Day 15 of Cycle 1) in ML-3. In ML-7, premenopausal pts with no prior ET and ≤1 line of chemotherapy for ABC received RIB or PBO + goserelin (3.6 mg every 28 days) + NSAI (anastrozole [1 mg/day]/letrozole [2.5 mg/day]). The primary endpoint of all three trials was locally assessed PFS. Secondary endpoints included overall response rate (ORR), clinical benefit rate (CBR), and duration of response (DoR; ML-3 and -7). DoR was an exploratory endpoint in ML-2.

Results: Data were pooled for 820 pts treated with RIB + ET (ML-2: n=334; ML-3: n=238; ML-7: n=248) and 710 pts treated with PBO + ET (ML-2: n=334; ML-3: n=129; ML-7: n=247). As of the data cutoffs (ML-2: January 2, 2017; ML-3: November 3, 2017; ML-7: August 20, 2017), in the RIB + ET vs PBO + ET arms, 385 (47%) vs 234 (33%) pts remained on-treatment; the most common reason for discontinuation was disease progression (n=292 [36%] vs n=391 [55%]). In this pooled analysis, median PFS was prolonged for RIB + ET vs PBO + ET, with a hazard ratio of 0.570 (95% confidence interval [CI] 0.491–0.662); median PFS was 25.3 months (95% CI 23.9–29.6) vs 15.6 months (95% CI 14.4–16.9), respectively. Consistent PFS benefit for RIB + ET vs PBO + ET was observed across pt subgroups, including ECOG performance status, age, race, or presence/absence of liver and/or lung metastases or bone-only disease. Among all pts in the pooled analysis, the ORR was 41% for RIB + ET vs 28% for PBO + ET and the CBR was 79% vs 70%, respectively. In pts with measurable disease at baseline (RIB + ET: n=639; PBO + ET: n=542), the ORR was 51% for RIB + ET vs 37% for PBO + ET and the CBR was 79% vs 68%, respectively. In the RIB + ET vs PBO + ET arms, the median DoR was 26.7 months vs 20.0 months. A decrease in best percentage change from baseline in the sum of longest diameters per RECIST was observed in 86% of pts receiving RIB + ET vs 73% of pts receiving PBO + ET.

Conclusions: RIB in combination with various ET partners demonstrates improved clinical outcomes vs PBO + ET across a broad population of pts with HR+, HER2– ABC. These data provide further support for the use of RIB-based combinations in pre- and postmenopausal pts with HR+, HER2– ABC who have received no prior ET for advanced disease.

Citation Format: Tripathy D, Hortobagyi G, Chan A, Im S-A, Chia S, Yardley D, Esteva FJ, Hurvitz S, Kong O, Bao W, Rodriguez Lorenc K, Diaz-Padilla I, Slamon DJ. First-line ribociclib + endocrine therapy in hormone receptor-positive, HER2-negative advanced breast cancer: A pooled efficacy analysis [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-18-05.

Abstract P6-17-36: Consensus and disagreement among experts for treatment of patients with HER2+ early-stage breast cancer suggests unmet need for online decision support tool

Treatment (tx) choices for HER2+ early stage breast cancer (EBC) have become increasingly complex. Clinicians and patients must decide 1) which chemotherapy and HER2-targeted agents to use, 2) the sequence of surgery and chemotherapy: either neoadjuvant (neoadj) or adjuvant (adj) tx, and 3) whether to shorten or extend maintenance HER2-targeted tx.

As tx options expand, so does the need for online decision aids. One online decision support tool was developed in 2015 to provide specific tx recommendations for pts with EBC and showed that community healthcare providers (HCPs) did not consistently align with experts for neoadj or adj tx of many pts with EBC (SABCS 2015 Abs P5-09-04).

This study includes analysis of neoadj and adj tx practice patterns of 5 breast cancer experts based on their tx recommendations for 270 unique HER2+ EBC case scenarios made for development of a 2018 online decision tool. We aim to compare these recommendations with the intended treatment of clinicians using the tool.

Results

Experts agree on neoadj tx approaches: initial surgery, no neoadj tx for pts with cT1a/b N0 tumors; neoadj tx before surgery for pts with ≥cT2 or N+ tumors. There was disparity among experts for pts with cT1c N0 disease: 3 experts recommend neoadj TCH±P and 2 recommend proceeding directly to surgery.

Experts generally recommend adj TCHP for pts with stage II N+ or higher HER2+ EBC who did not receive neoadj tx. In addition, 5/5 experts would consider extended adj tx with neratinib for these pts if HR+ and 2/5 experts would also consider neratinib if HR–.

In pts who received neoadj chemo+HER2 tx, post-surgery management depends on response to neoadj tx. For pts with pCR, 5/5 experts generally agree on continuing H+P if both were given as neoadj tx or H alone if only H given as neoadj tx for a total of 1 yr of anti-HER2 Ab tx and 2/5 experts would consider extended adj tx with neratinib for HR+ disease. For pts with residual disease, experts would recommend continuing H+P if both were given as neoadj tx and most would add P for subsequent adj tx if H alone was given to complete a total of 1 yr of anti-HER2 Ab tx (Table1). All experts would consider extended adj tx with neratinib for HR+ disease and 3/5 experts would also consider neratinib for HR– disease. None of the experts recommended less than 12 mos of adj HER2-targeted tx.

We will present analyses of cases entered into our online tool and detailed comparisons of expert and the intended treatment of clinicians using the tool.

Conclusions

Practice patterns are changing rapidly and are more complex in response to the evolving treatment landscape for HER2+ EBC. This analysis highlights several areas of expert consensus; however, disparities remain for select cases. The current tool addresses an unmet medical need for expert-led evaluation of HER2+ EBC tx choices and warrants further investigation.

Expert Recommendations: Initial Adj HER2 Ab Tx After Neodj Tx With H Alone ExpertsResponse12345pCR (HR-)HHHHHpCR (HR+)HHHHHypT1a-c N0 (HR-)H + PHH + PH + PH + PypT1a-c N0 (HR+)H + PHHH + PHypT2 N0 (HR-)H + PH + PH + PH + PH + PypT2 N0 (HR+)H + PH + PHH + PH + PypTany N+ (HR+ or HR-)H + PH + PH + PH + PH + P

Citation Format: Holmes FA, Rosenthal KM, Hurvitz S, Pegram MD, Yardley DA, Obholz KL, O'Shaughnessy J. Consensus and disagreement among experts for treatment of patients with HER2+ early-stage breast cancer suggests unmet need for online decision support tool [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-36.