Abstract OT1-05-01: A phase I/II, single arm, non-randomized study of ribociclib (LEE011), a CDK 4/6 inhibitor, in combination with bicalutamide, an androgen receptor (AR) inhibitor, in advanced AR+ triple-negative breast cancer

Background: Triple negative breast cancer (TNBC) is a heterogeneous disease encompassing distinct intrinsic molecular subtypes, including a luminal androgen receptor (AR) subtype, characteristically dependent on AR signaling. The AR is expressed in more than 50% of TNBCs. Bicalutamide is an oral, non-steroidal, AR antagonist, which has been studied in metastatic TNBC with a clinical benefit rate of 19% at 24 weeks. In preclinical models, cyclin dependant kinase (CDK) 4/6 inhibition has been shown to restore sensitivity to AR inhibition, and may thus be an important resistance mechanism. Ribociclib is an orally bioavailable, highly specific CDK4/6 inhibitor that induces cell cycle arrest, already approved in endocrine receptor positive breast cancers. We hypothesize that inhibition of CDK inhibition can enhance the activity of anti-androgen therapy in TNBC that express AR.

Methods: We designed a phase I/II, single arm, non-randomized, open label study of the combination of bicalutamide with ribociclib in women with advanced AR-positive TNBC. The primary objective of the phase I component is to determine the maximum tolerated dose of the combination, and of the phase II component to assess the clinical benefit rate at 16 weeks. Secondary objectives include progression free and overall survival, objective response rates, and safety and tolerability. Exploratory objectives will be to assess AR quantification, localization and splice variants in circulating tumor cells, as well as quantification of pan and phospho proteins of Rb. Eligible patients must have measurable metastatic or unresectable AR-positive TNBC and have had no more than 1 line of systemic therapy for metastatic disease. The phase I study will be conducted using a 3+3 dose escalation schema, 12 to 18 patients are expected to enroll. The phase II component will utilize a Simon's two stage design, enrolling 24 patients for the first stage. At least 5 subjects must have clinical benefit by 16 weeks to proceed onto the second stage, which would enroll an additional 22 subjects for a total of 46 patients. The study will be powered to detect a clinical benefit rate of 40% with a power of 80% and a type I error rate of 10%. Contact dmusapatika@hoosiercancer.org for more information about the study.

Citation Format: Santa-Maria CA, Rampurwala M, Wisinski K, Toppmeyer D, O'Regan R. A phase I/II, single arm, non-randomized study of ribociclib (LEE011), a CDK 4/6 inhibitor, in combination with bicalutamide, an androgen receptor (AR) inhibitor, in advanced AR+ triple-negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT1-05-01.

Abstract OT3-05-10: A single arm phase II study of palbociclib in combination with tamoxifen as first line therapy for metastatic hormone receptor positive breast cancer

Background: Hormone receptor positive breast cancer is the most commonly diagnosed subset of breast cancer (60-65%). Endocrine therapy is effective for this subset of breast cancer, in both the adjuvant and metastatic settings. Despite advances in endocrine therapy, many patients relapse during or after completing adjuvant therapy and metastatic breast cancer remains incurable. Palbociclib is a reversible, oral, small molecule inhibitor of cyclin dependent kinases 4 and 6 (CDK4/6). CDK4 and CDK6 together with cyclin D have important roles in regulation of the G1/S transition via regulation of the phosphorylation state of retinoblastomaprotein (Rb). Palbociclib showed significantly improved progression-free survival taken together with endocrine agents in treatment of metastatic breast cancer. Preclinical data showed that in combination with tamoxifen, palbociclib had synergistic growth inhibitory activity as well as efficacy in a model of acquired tamoxifen resistance. Combining palbociclib with tamoxifen in first line treatment of metastatic hormone receptor positive breast cancer may offers an appealing alternative to other endocrine combinations. Methods: This is a non-randomized, open-label, single-arm, multicenter, phase II study of palbociclib in combination with tamoxifen in patients with hormone receptor positive/HER2 negative advanced breast cancer. The primary objective is to determine the objective response rate (complete or partial response) based on RECIST 1.1 or MDA Criteria (for patients with bone only disease). Secondary objectives are: safety and tolerability, progression-free survival, clinical benefit rate, 2-year overall survival. Correlative objectives will explore alterations in circulating tumor DNA and changes in gene expression pattern at the time of progression. Eligibility criteria: women or men with diagnosis of hormone receptor positive/ HER2 negative locally advanced or metastatic breast cancer, not amenable to curative surgery; no prior systemic anti-cancer therapy for advanced hormone receptor positive breast cancer; adequate organ function; pre and post menopausal women are allowed. Drug administration: palbociclib dose will be 125 mg orally once daily on days 1-21 of each 28-day cycle; tamoxifen dose will be 20 mg orally once daily for every day of the 28-day cycle. As of June 2017, the study enrolled 10/71 patients and it is still open to enrollment. NCT 02668666; ocdanciu@uic.edu

Citation Format: Danciu OC, Hoskins K, Tamkus D, Truica C, Blaes A, Green L, Liu L, Toppmeyer D, Wisinski K. A single arm phase II study of palbociclib in combination with tamoxifen as first line therapy for metastatic hormone receptor positive breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT3-05-10.

Abstract P4-22-21: NCI9782: A phase 1 study of talazoparib in combination with carboplatin and paclitaxel in patients with advanced solid tumors

Background: Poly(ADP-ribose) polymerase (PARP) enzymes are involved in DNA repair and activated by DNA strand breaks. DNA damage from carboplatin is associated with activation of PARP. Preclinical data indicate that PARP inhibition potentiates the anti-tumor effect of platinum chemotherapy. Talazoparib (T) is an oral, selective PARP inhibitor with a single agent maximum tolerated dose (MTD) of 1mg orally qd. Primary dose-limiting toxicity (DLT) was thrombocytopenia. This phase I study combines T with the commonly used chemotherapy regimen of carboplatin (C) and paclitaxel (P).

Methods: Two dosing schedules are being investigated. In both schedules, C is administered on day 1 and P on days 1, 8, and 15 of a 21-day cycle. T (100-1000mcg) is dosed once daily for days 1-7 (schedule A) or days 1-3 (schedule B) starting on day 1. A 3+3 design is used for dose escalation. Key eligibility criteria include age 318 with a measurable or evaluable solid incurable malignancy. Patients (pts) must have tumor type that is expected to respond to C + P or have BRCA germline or somatic mutation. Stable, treated brain metastases are allowed. No prior C for metastatic disease is allowed. Pts must have platelets>150 and no need for anticoagulation. After 4-6 cycles of combination therapy, pts may continue the combination, change to C and intermittent T without P or change to T alone with continuous daily dosing. Each schedule will have a 6 subject dose expansion at the MTD. The starting dose level for schedule B will be the MTD from schedule A.

Results: Schedule A cohort results are reported: 11 pts (median age 59 [range 39-68]; 8 female; 3 male) have been enrolled. Pts had breast (6), ovarian (2), pancreatic (1), and SCC of oropharynx (1) and concurrent ovarian and pancreatic (1). Five pts are BRCA2+ and 3 pts are BRCA1+. Dose level 3 on schedule A (T 350mcg with C AUC 6 and P 80mg/m2) exceeded the MTD with 2 of 3 pts experiencing hematologic dose limiting toxicities (DLTs) including 1 pt with grade (gr) 3 neutropenic fever and gr 4 thrombocytopenia and another pt with grade 3/4 neutropenia lasting > 7 days. Most common AEs include neutropenia (grade 3-4: 7), anemia (grade 3-4: 3), and thrombocytopenia (grade 3-4: 4). Results from expansion of dose level 2 (T 250mcg with C AUC 6 and T 80mg/m2) will be presented. The 11 pts were on study a median of 9 weeks (range 9-36+). Four pts have discontinued study therapy: 1 due to need for anticoagulation for PE, 1 for prolonged cytopenias, and 2 for disease progression. Of the 8 pts with measurable disease evaluated for response to date, 4 had SD, 1 had a cPR, 1 had radiographic CR, and 2 with PD. A pt with BRCA 1+ triple negative breast cancer has maintained a prolonged PR (36+ weeks) even after dose reductions to T 100mcg with C AUC 3. One pt with ovarian cancer (BRCA WT) has radiographic CR (CA 125 remains mildly elevated) after 15+ weeks of therapy.

Conclusion: PARP inhibition with talazoparib days 1-7 in combination with carboplatin and paclitaxel leads to DLT of myelosuppression. However, clinical responses are seen even with lower dose combinations.

Citation Format: Turk A, Chan N, Leal T, O'Regan R, Tevaarwerk A, Rice L, Campbell T, Barroilhet L, Mehnert J, Eickhoff J, Kolesar J, Liu G, Wisinski K. NCI9782: A phase 1 study of talazoparib in combination with carboplatin and paclitaxel in patients with advanced solid tumors [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-22-21.

Abstract OT3-02-06: Femara plus ribociclib or placebo as neo-adjuvant endocrine therapy for women with ER+, HER2-negative early breast cancer - The Feline trial

Background:

In early ER+ breast cancer, neo-adjuvant (NA) endocrine therapy (ET) may identify a subset of patients with endocrine sensitive disease with excellent outcomes without chemotherapy. In patients receiving a NA aromatase inhibitor, on- therapy, short term (day 14) Ki-67 of <10% and post NA pre-operative endocrine prognostic index (PEPI) 0 at surgery are associated with low relapse rates without chemotherapy. Ribociclib, a novel CDK4/6 inhibitor is active in ER+ metastatic breast cancer. We hypothesize that ribociclib+letrozole as NA ET for stage II-III breast cancer will increase the number of women with a PEPI 0 at surgery.

Trial Design:

Randomized, placebo-controlled, multi-center, phase II, investigator initiated trial of NA letrozole +/- ribociclib in postmenopausal women with ER+, HER2-, breast cancer. Subjects will be randomized 1:1:1 to letrozole 2.5 mg daily + placebo, letrozole 2.5mg daily + ribociclib 600mg daily on D1-21 of a 28 day cycle (intermittent dosing), or letrozole 2.5mg daily + ribociclib 400mg daily (continuous dosing). Treatment will be continued for 6 months followed by surgery. Research core biopsies and blood will be collected at baseline, at day 14, and at surgery. A Ki67 >10% at day 14 will result in discontinuation of the subject from the protocol as this may be an early indicator of resistance to endocrine therapy. An MRI will be done after 2 months of therapy to assess response/progression. Primary endpoint is a PEPI score of 0 at surgery.

Key Eligibility Criteria:

Postmenopausal (natural or surgical) women with stage II/III ER+, HER2- breast cancer. Must have a palpable breast mass of at least 2 cm. Multicentric/contralateral invasive disease not allowed. Ipsilateral/contralateral DCIS is allowed. Inflammatory breast cancer is excluded.

Specific Aims:

Primary objective: To determine if ribociclib+letrozole as a 24 week NA ET increases rate of PEPI score of 0 at surgery compared to letrozole. Secondary objectives: To determine if ribociclib+letrozole as a 24 week NA ET increases the proportion of tumors with complete cell cycle arrest compared to letrozole; to determine if ribociclib in combination with letrozole for 24 weeks results in improved 5 year RFS compared to letrozole; to examine differences in response rates between the two ribociclib containing arms vs letrozole.

Statistical Methods:

The two ribocilib containing arms (n=80) will be combined for analysis against placebo + letrozole (n=40). Assuming that addition of ribociclib will increase the rate of PEPI 0 by 20%, and setting Type I error rate at 10% and Type II error rates at 20% in the final analysis, a sample size of 80 women in the treatment arms (40 in each arm) and 40 women in the control arm are needed to show significance.

Patient accrual and target accrual:

Participating sites include The Univ of Kansas Med Ctr, City of Hope National Med Ctr, Massachusetts General Hospital, University of Miami Sylvester Comprehensive Cancer Ctr, University of Arkansas for Medical Sciences, and University of Wisconsin. The trial has accrued 16 patients with a target accrual of 120 patients. Accrual should be complete in 2/2017.

Contact information: Qamar Khan, MD (qkhan@kumc.edu).

Citation Format: Khan QJ, Prochaska LH, Mohammad J, Yuan Y, O'Dea A, Bardia A, Wisinski K, Hard M, Baccaray S, Makhoul I, Wagner J, Laura S, Ma C, Sharma P. Femara plus ribociclib or placebo as neo-adjuvant endocrine therapy for women with ER+, HER2-negative early breast cancer - The Feline trial [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr OT3-02-06.