Datopotamab Deruxtecan in Advanced or Metastatic HR+/HER2- and Triple-Negative Breast Cancer: Results From the Phase I TROPION-PanTumor01 Study

PURPOSE

Datopotamab deruxtecan (Dato-DXd) is an antibody-drug conjugate consisting of a humanized antitrophoblast cell-surface antigen 2 (TROP2) monoclonal antibody linked to a potent, exatecan-derived topoisomerase I inhibitor payload via a plasma-stable, selectively cleavable linker.

PATIENTS AND METHODS

TROPION-PanTumor01 (ClinicalTrials.gov identifier: NCT03401385) is a phase I, dose-escalation, and dose-expansion study evaluating Dato-DXd in patients with previously treated solid tumors. The primary study objective was to assess the safety and tolerability of Dato-DXd. Secondary objectives included evaluation of antitumor activity and pharmacokinetics. Results from patients with advanced/metastatic hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) breast cancer (BC) or triple-negative BC (TNBC) are reported.

RESULTS

At data cutoff (July 22, 2022), 85 patients (HR+/HER2- BC = 41, and TNBC = 44) had received Dato-DXd. The objective response rate by blinded independent central review was 26.8% (95% CI, 14.2 to 42.9) and 31.8% (95% CI, 18.6 to 47.6) for patients with HR+/HER2- BC and TNBC, respectively. The median duration of response was not evaluable in the HR+/HER2- BC cohort and 16.8 months in the TNBC cohort. The median progression-free survival in patients with HR+/HER2- BC and TNBC was 8.3 and 4.4 months, respectively. All-cause treatment-emergent adverse events (TEAEs; any grade, grade ≥3) were observed in 100% and 41.5% of patients with HR+/HER2- BC and 100% and 52.3% of patients with TNBC. Stomatitis was the most common TEAE (any grade, grade ≥3) in both HR+/HER2- BC (82.9%, 9.8%) and TNBC (72.7%, 11.4%) cohorts.

CONCLUSION

In patients with heavily pretreated advanced HR+/HER2- BC and TNBC, Dato-DXd demonstrated promising clinical activity and a manageable safety profile. Dato-DXd is currently being evaluated in phase III studies.

The Right Dose: Results of a Patient Advocate-Led Survey of Individuals With Metastatic Breast Cancer Regarding Treatment-Related Side Effects and Views About Dosage Assessment to Optimize Quality of Life

PURPOSE

Although patients with metastatic breast cancer (MBC) have been living longer with the advent of more effective treatments such as targeted therapy and immunotherapy, the disease remains incurable, and most patients will undergo therapy indefinitely. When beginning therapy, patients are typically prescribed dose often based upon the maximum tolerated dose identified in phase I clinical trials. However, patients' perspectives about tolerability and willingness to discuss individualized dosing of drugs upon initiation of a new regimen and throughout the course of treatment have not been comprehensively evaluated.

METHODS

Patient advocates and medical oncologists from the Patient-Centered Dosing Initiative (PCDI) developed a survey to ascertain the prevalence and severity of MBC patients' treatment-related side effects, the level of patient-physician communication, mitigation strategies, perception about the relative efficacy of higher versus lower doses, and willingness to discuss alternative dosing. The PCDI distributed the anonymous confidential online survey in August 2020 to individuals with self-reported MBC.

RESULTS

One thousand and two hundred twenty-one patients with MBC completed the survey. 86.1% (n = 1,051) reported experiencing at least one significant treatment-related side effect, and of these, 20.3% (n = 213) visited the emergency room/hospital and 43.2% (n = 454) missed at least one treatment. Nearly all patients with side effects (97.6%, n = 1,026) informed their doctor and 81.7% (n = 838) received assistance. Of the 556 patients given a dose reduction for side-effect mitigation, 82.6% (n = 459) reported relief. Notably, majority of patients (53.3%, n = 651) do not believe that higher dose is always more effective than lower dose, and 92.3% (n = 1,127) would be willing to discuss flexible dosing options with their physicians based upon personal characteristics to optimize quality of life.

CONCLUSION

Given that the majority of patients with MBC experienced at least one substantial treatment-related side effect and most patients given a dose reduction reported improvement, innovative dosage-related strategies are warranted to sustain and improve patients' well-being. Patient-physician discussions in which the patient's unique attributes and circumstances are assessed upon initiation of new treatment and throughout the course of therapy may facilitate the identification of the most favorable dose for each patient, and the majority of patients would be receptive to this approach.

Phase 1/2 study of combined BCL-xL and MEK inhibition with navitoclax and trametinib in KRAS or NRAS mutant advanced solid tumors

PURPOSE

MEK inhibitors (MEKi) lack monotherapy efficacy in most RAS-mutant cancers. BCL-xL is an anti-apoptotic protein identified by a synthetic lethal shRNA screen as a key suppressor of apoptotic response to MEKi.

PATIENTS AND METHODS

We conducted a dose escalation study (NCT02079740) of the BCL-xL inhibitor navitoclax and MEKi trametinib in patients with RAS-mutant tumors with expansion cohorts for: pancreatic, gynecologic (GYN), non-small cell lung cancer (NSCLC), and other cancers harboring KRAS/NRAS mutations. Paired pre-treatment and day 15 tumor biopsies and serial cell-free (cf)DNA were analyzed.

RESULTS

91 patients initiated treatment, 38 in dose escalation. 58% had ³3 prior therapies. 15 patients (17%) had colorectal cancer (CRC), 19 (11%) pancreatic, 15 (167%) NSCLC, and 32 (35%) GYN cancers. The recommended phase 2 dose (RP2D) was established as trametinib 2mg daily days 1-14 and navitoclax 250mg daily days 1-28 of each cycle. Most common adverse events included diarrhea, thrombocytopenia, increased AST/ALT, and acneiform rash. At RP2D, 8/49 (16.3%) evaluable patients achieved partial response (PR). Disease-specific differences in efficacy were noted. In GYN patients at the RP2D, 7/21 (33.3%) achieved a PR and median duration of response 8.2 months. No PRs occurred in CRC, NSCLC, or pancreatic patients. MAPK pathway inhibition was observed in on-treatment tumor biopsies. Reductions in KRAS/NRAS mutation levels in cfDNA correlated with clinical benefit.

CONCLUSIONS

Navitoclax in combination with trametinib was tolerable. Durable clinical responses were observed in patients with RAS-mutant GYN cancers, warranting further evaluation in this population.

A risk analysis of alpelisib-induced hyperglycemia in patients with advanced solid tumors and breast cancer

BACKGROUND

Hyperglycemia is an on-target effect of PI3Kα inhibitors. Early identification and intervention of treatment-induced hyperglycemia is important for improving management of patients receiving a PI3Kα inhibitor like alpelisib. Here, we characterize incidence of grade 3/4 alpelisib-related hyperglycemia, along with time to event, management, and outcomes using a machine learning model.

METHODS

Data for the risk model were pooled from patients receiving alpelisib ± fulvestrant in the open-label, phase 1 X2101 trial and the randomized, double-blind, phase 3 SOLAR-1 trial. The pooled population (n = 505) included patients with advanced solid tumors (X2101, n = 221) or HR+/HER2- advanced breast cancer (SOLAR-1, n = 284). External validation was performed using BYLieve trial patient data (n = 340). Hyperglycemia incidence and management were analyzed for SOLAR-1.

RESULTS

A random forest model identified 5 baseline characteristics most associated with risk of developing grade 3/4 hyperglycemia (fasting plasma glucose, body mass index, HbA1c, monocytes, age). This model was used to derive a score to classify patients as high or low risk for developing grade 3/4 hyperglycemia. Applying the model to patients treated with alpelisib and fulvestrant in SOLAR-1 showed higher incidence of hyperglycemia (all grade and grade 3/4), increased use of antihyperglycemic medications, and more discontinuations due to hyperglycemia (16.7% vs. 2.6% of discontinuations) in the high- versus low-risk group. Among patients in SOLAR-1 (alpelisib + fulvestrant arm) with PIK3CA mutations, median progression-free survival was similar between the high- and low-risk groups (11.0 vs. 10.9 months). For external validation, the model was applied to the BYLieve trial, for which successful classification into high- and low-risk groups with shorter time to grade 3/4 hyperglycemia in the high-risk group was observed.

CONCLUSIONS

A risk model using 5 clinically relevant baseline characteristics was able to identify patients at higher or lower probability for developing alpelisib-induced hyperglycemia. Early identification of patients who may be at higher risk for hyperglycemia may improve management (including monitoring and early intervention) and potentially lead to improved outcomes.

REGISTRATION

ClinicalTrials.gov: NCT01219699 (registration date: October 13, 2010; retrospectively registered), ClinicalTrials.gov: NCT02437318 (registration date: May 7, 2015); ClinicalTrials.gov: NCT03056755 (registration date: February 17, 2017).

A phase Ib study evaluating the recommended phase II dose, safety, tolerability, and efficacy of mivavotinib in combination with nivolumab in advanced solid tumors

Mivavotinib (TAK-659/CB-659), a dual SYK/FLT3 inhibitor, reduced immunosuppressive immune cell populations and suppressed tumor growth in combination with anti-PD-1 therapy in cancer models. This dose-escalation/expansion study investigated the safety, pharmacokinetics, pharmacodynamics, and preliminary efficacy of mivavotinib plus nivolumab in patients with advanced solid tumors. Patients received oral mivavotinib 60-100 mg once-daily plus intravenous nivolumab 3 mg/kg on days 1 and 15 in 28-day cycles until disease progression or unacceptable toxicity. The dose-escalation phase evaluated the recommended phase II dose (RP2D; primary endpoint). The expansion phase evaluated overall response rate (primary end point) at the RP2D in patients with triple-negative breast cancer (TNBC). During dose-escalation (n = 24), two dose-limiting toxicities (grade 4 lipase increased and grade 3 pyrexia) occurred in patients who received mivavotinib 80 mg and 100 mg, respectively. The determined RP2D was once-daily mivavotinib 80 mg plus nivolumab 3 mg/kg. The expansion phase was terminated at ~50% enrollment (n = 17) after failing to meet an ad hoc efficacy futility threshold. Among all 41 patients, common treatment-emergent adverse events (TEAEs) included dyspnea (48.8%), aspartate aminotransferase increased, and pyrexia (46.3% each). Common grade ≥3 TEAEs were hypophosphatemia and anemia (26.8% each). Mivavotinib plasma exposure was generally dose-proportional (60-100 mg). One patient had a partial response. Mivavotinib 80 mg plus nivolumab 3 mg/kg was well tolerated with no new safety signals beyond those of single-agent mivavotinib or nivolumab. Low response rates highlight the challenges of treating unresponsive tumor types, such as TNBC, with this combination and immunotherapies in general. TRIAL REGISTRATION ID: NCT02834247.

Allosteric PI3Kα Inhibition Overcomes On-target Resistance to Orthosteric Inhibitors Mediated by Secondary PIK3CA Mutations

PIK3CA mutations occur in ∼8% of cancers, including ∼40% of HR-positive breast cancers, where the PI3K-alpha (PI3Kα)-selective inhibitor alpelisib is FDA approved in combination with fulvestrant. Although prior studies have identified resistance mechanisms, such as PTEN loss, clinically acquired resistance to PI3Kα inhibitors remains poorly understood. Through serial liquid biopsies and rapid autopsies in 39 patients with advanced breast cancer developing acquired resistance to PI3Kα inhibitors, we observe that 50% of patients acquire genomic alterations within the PI3K pathway, including PTEN loss and activating AKT1 mutations. Notably, although secondary PIK3CA mutations were previously reported to increase sensitivity to PI3Kα inhibitors, we identified emergent secondary resistance mutations in PIK3CA that alter the inhibitor binding pocket. Some mutations had differential effects on PI3Kα-selective versus pan-PI3K inhibitors, but resistance induced by all mutations could be overcome by the novel allosteric pan-mutant-selective PI3Kα-inhibitor RLY-2608. Together, these findings provide insights to guide strategies to overcome resistance in PIK3CA-mutated cancers.

SIGNIFICANCE

In one of the largest patient cohorts analyzed to date, this study defines the clinical landscape of acquired resistance to PI3Kα inhibitors. Genomic alterations within the PI3K pathway represent a major mode of resistance and identify a novel class of secondary PIK3CA resistance mutations that can be overcome by an allosteric PI3Kα inhibitor. See related commentary by Gong and Vanhaesebroeck, p. 204 . See related article by Varkaris et al., p. 240 . This article is featured in Selected Articles from This Issue, p. 201.

Managing hyperglycemia and rash associated with alpelisib: expert consensus recommendations using the Delphi technique

Hyperglycemia and rash are expected but challenging adverse events of phosphatidylinositol-3-kinase inhibition (such as with alpelisib). Two modified Delphi panels were conducted to provide consensus recommendations for managing hyperglycemia and rash in patients taking alpelisib. Experts rated the appropriateness of interventions on a 1-to-9 scale; median scores and dispersion were used to classify the levels of agreement. Per the hyperglycemia panel, it is appropriate to start alpelisib in patients with HbA1c 6.5% (diabetes) to <8%, or at highest risk for developing hyperglycemia, if they have a pre-treatment endocrinology consult. Recommend prophylactic metformin in patients with baseline HbA1c 5.7% to 6.4%. Metformin is the preferred first-line anti-hyperglycemic agent. Per the rash panel, initiate prophylactic nonsedating H1 antihistamines in patients starting alpelisib. Nonsedating H1 antihistamines and topical steroids are the preferred initial management for rash. In addition to clinical trial evidence, these recommendations will help address gaps encountered in clinical practice.

Virtual Molecular and Precision Medicine Clinic to Improve Access to Clinical Trials for Patients With Metastatic Breast Cancer: An Academic/Community Collaboration

PURPOSE

There is a demand for improved care delivery surrounding genomic testing and clinical trial enrollment among patients with metastatic breast cancer (MBC). We sought to improve the current process via real-time informal consultation and prescreening assessment for patients with MBC treated by community and academic medical oncologists by implementing a virtual molecular and precision medicine (vMAP) clinic.

METHODS

The vMAP program used a virtual referral system directed to a multidisciplinary team with precision medicine expertise. Providers contacted vMAP regarding patients with MBC, and on receipt of referral, the vMAP team engaged in discussion to identify if further diagnostics were needed (including genomic testing) and to identify potential clinical trials or standard treatment options. Recommendations were then sent to the referring provider within 72 hours. Pre-/postsurveys were issued to network physicians to assess for barriers, clinical trial access, and vMAP referral experience. Program implementation was evaluated with the Squire 2.0 reporting guidelines for quality improvement in health care as a framework.

RESULTS

Eighty-one cases from 22 providers were referred to vMAP over a 26-month period. The average response time to the referring provider with a finalized recommendation was 1.90 ± 1.82 days. A total of 86.4% of cases had clinical trial options on vMAP prescreen, with 40.7% initiating formal screening assessments and 27 patients (33.3%) ultimately enrolling on trials. On resurvey, 92% of survey responses across community oncology referring providers said that they were very likely to use vMAP again.

CONCLUSION

In the initial 2-year period, vMAP demonstrated an efficient means to offer real-time interpretation of genomic testing and identification of clinical trials for patients with MBC, with effective clinical trial enrollment and high rates of referring provider satisfaction.

A Rare Presentation of Aggressive Renal Cell Carcinoma and the Utility of Early Molecular Testing in Rapidly Progressing Malignancies: A Case Report

In rapidly progressing cancers, appropriate selection of first-line therapy is essential in prolonging survival. Alongside immunohistochemistry (IHC), comprehensive genomics, including whole exome and transcriptome sequencing (WES/WTS), can improve diagnostic accuracy and guide therapeutic management. Here, we report a young patient with rapidly progressing malignancy and unexpected post-mortem results, a scenario that may have been altered by early, comprehensive genomic sequencing. A 43-year-old man with no relevant medical history presented to the emergency department with progressive cough and dyspnea despite treatment for pneumonia. Radiology revealed enlarged subcarinal, hilar, retroperitoneal, and mesenteric lymph nodes, suspicious for metastasis, and a right kidney mass. Pathologic analysis of a retroperitoneal lymph node was felt to be most consistent with metastatic epithelioid angiomyolipoma (mEAML). Three weeks later, he was urgently treated with an mTOR inhibitor for presumed mEAML due to rapid clinical decline, and a subsequent 4R lymph node biopsy was performed to confirm the diagnosis and identify genomic targets via IHC and WES/WTS. Unfortunately, he developed hypoxic respiratory failure, and only posthumously did WES/WTS reveal pathogenic variants in BAP1 and VHL, consistent with clear cell renal cell carcinoma (ccRCC). With an earlier ccRCC diagnosis, he would have received combination immunotherapy/tyrosine kinase inhibition, which has significantly greater activity than mTOR inhibition in ccRCC. He could have received systemic treatment earlier, with optimal therapy, while potentially carrying lower tumor burden and greater clinical stability. In cases of rapidly progressing malignancies with complex histopathological presentations, early comprehensive molecular-based testing can aid in diagnosis and critical therapeutic decision-making.

Immune Responses in Checkpoint Myocarditis Across Heart, Blood, and Tumor

Immune checkpoint inhibitors (ICIs) are widely used anti-cancer therapies that can cause morbid and potentially fatal immune-related adverse events (irAEs). ICI-related myocarditis (irMyocarditis) is uncommon but has the highest mortality of any irAE. The pathogenesis of irMyocarditis and its relationship to anti-tumor immunity remain poorly understood. We sought to define immune responses in heart, tumor, and blood during irMyocarditis and identify biomarkers of clinical severity by leveraging single-cell (sc)RNA-seq coupled with T cell receptor (TCR) sequencing, microscopy, and proteomics analysis of 28 irMyocarditis patients and 23 controls. Our analysis of 284,360 cells from heart and blood specimens identified cytotoxic T cells, inflammatory macrophages, conventional dendritic cells (cDCs), and fibroblasts enriched in irMyocarditis heart tissue. Additionally, potentially targetable, pro-inflammatory transcriptional programs were upregulated across multiple cell types. TCR clones enriched in heart and paired tumor tissue were largely non-overlapping, suggesting distinct T cell responses within these tissues. We also identify the presence of cardiac-expanded TCRs in a circulating, cycling CD8 T cell population as a novel peripheral biomarker of fatality. Collectively, these findings highlight critical biology driving irMyocarditis and putative biomarkers for therapeutic intervention.

A Gene Panel Associated With Abemaciclib Utility in ESR1-Mutated Breast Cancer After Prior Cyclin-Dependent Kinase 4/6-Inhibitor Progression

PURPOSE

For patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC), first-line treatment is endocrine therapy (ET) plus cyclin-dependent kinase 4/6 inhibition (CDK4/6i). After disease progression, which often comes with ESR1 resistance mutations (ESR1-MUT), which therapies to use next and for which patients are open questions. An active area of exploration is treatment with further CDK4/6i, particularly abemaciclib, which has distinct pharmacokinetic and pharmacodynamic properties compared with the other approved CDK4/6 inhibitors, palbociclib and ribociclib. We investigated a gene panel to prognosticate abemaciclib susceptibility in patients with ESR1-MUT MBC after palbociclib progression.

METHODS

We examined a multicenter retrospective cohort of patients with ESR1-MUT MBC who received abemaciclib after disease progression on ET plus palbociclib. We generated a panel of CDK4/6i resistance genes and compared abemaciclib progression-free survival (PFS) in patients without versus with mutations in this panel (CDKi-R[-] v CDKi-R[+]). We studied how ESR1-MUT and CDKi-R mutations affect abemaciclib sensitivity of immortalized breast cancer cells and patient-derived circulating tumor cell lines in culture.

RESULTS

In ESR1-MUT MBC with disease progression on ET plus palbociclib, the median PFS was 7.0 months for CDKi-R(-) (n = 17) versus 3.5 months for CDKi-R(+) (n = 11), with a hazard ratio of 2.8 (P = .03). In vitro, CDKi-R alterations but not ESR1-MUT induced abemaciclib resistance in immortalized breast cancer cells and were associated with resistance in circulating tumor cells.

CONCLUSION

For ESR1-MUT MBC with resistance to ET and palbociclib, PFS on abemaciclib is longer for patients with CDKi-R(-) than CDKi-R(+). Although a small and retrospective data set, this is the first demonstration of a genomic panel associated with abemaciclib sensitivity in the postpalbociclib setting. Future directions include testing and improving this panel in additional data sets, to guide therapy selection for patients with HR+/HER2- MBC.

Role of Kidney Stones in Renal Pelvis Flow

Ureteroscopy is a commonly performed medical procedure to treat stones in the kidney and ureter using a ureteroscope. Throughout the procedure, saline is irrigated through the scope to aid visibility and wash-out debris from stone fragmentation. The key challenge that this research addresses is to build a fundamental understanding of the interaction between the kidney stones/stone fragments and the flow dynamics in the renal pelvis flow. We examine the time-dependent flow dynamics inside an idealized renal pelvis in the context of a surgical procedure for kidney stone removal. Here, we examine the time-dependent evolution of these vortical flow structures in three dimensions, and incorporate the presence of rigid kidney stones. We perform direct numerical simulations, solving the transient Navier-Stokes equations in a spherical domain. Our numerical predictions for the flow dynamics in the absence of stones are validated with available experimental and numerical data, and the governing parameters and flow regimes are chosen carefully in order to satisfy several clinical constraints. The results shed light on the crucial role of flow circulation in the renal cavity and its effect on the trajectories of rigid stones. We demonstrate that stones can either be washed out of the cavity along with the fluid, or be trapped in the cavity via their interaction with vortical flow structures. Additionally, we study the effect of multiple stones in the flow field within the cavity in terms of the kinetic energy, entrapped fluid volume, and the clearance rate of a passive tracer modeled via an advection-diffusion equation. We demonstrate that the flow in the presence of stones features a higher vorticity production within the cavity compared with the stone-free cases.

Utilizing cell-free DNA to predict risk of developing brain metastases in patients with metastatic breast cancer

We compared cell-free DNA (cfDNA) results at MBC diagnosis in patients who developed brain metastases (BM) vs those without (non-BM) to understand genomic predictors of BM. Patients with cfDNA testing at MBC diagnosis (Guardant360®, 73 gene next generation sequencing) were identified. Clinical and genomic features of BM and non-BM were compared (Pearson's/Wilcoxon rank sum tests). Eighteen of 86 patients (21%) with cfDNA at MBC diagnosis developed BM. Comparing BM vs non-BM, a higher prevalence of BRCA2 (22% vs 4.4%, p = 0.01), APC (11% vs 0%, p = 0.005), CDKN2A (11% vs 1.5%, p = 0.05), and SMAD4 (11% vs 1.5%, p = 0.05) was observed. Seven of 18 BM had ≥1 of the following 4 mutations in baseline cfDNA: APC, BRCA2, CDKN2A or SMAD4 vs 5/68 non-BM (p = 0.001). Absence of this genomic pattern had a high negative predictive value (85%) and specificity (93%) in excluding BM development. Baseline genomic profile varies in MBC that develops BM.

The Genetic Determinants of Aortic Distention

BACKGROUND

As the largest conduit vessel, the aorta is responsible for the conversion of phasic systolic inflow from ventricular ejection into more continuous peripheral blood delivery. Systolic distention and diastolic recoil conserve energy and are enabled by the specialized composition of the aortic extracellular matrix. Aortic distensibility decreases with age and vascular disease.

OBJECTIVES

In this study, we sought to discover epidemiologic correlates and genetic determinants of aortic distensibility and strain.

METHODS

We trained a deep learning model to quantify thoracic aortic area throughout the cardiac cycle from cardiac magnetic resonance images and calculated aortic distensibility and strain in 42,342 UK Biobank participants.

RESULTS

Descending aortic distensibility was inversely associated with future incidence of cardiovascular diseases, such as stroke (HR: 0.59 per SD; P = 0.00031). The heritabilities of aortic distensibility and strain were 22% to 25% and 30% to 33%, respectively. Common variant analyses identified 12 and 26 loci for ascending and 11 and 21 loci for descending aortic distensibility and strain, respectively. Of the newly identified loci, 22 were not significantly associated with thoracic aortic diameter. Nearby genes were involved in elastogenesis and atherosclerosis. Aortic strain and distensibility polygenic scores had modest effect sizes for predicting cardiovascular outcomes (delaying or accelerating disease onset by 2%-18% per SD change in scores) and remained statistically significant predictors after accounting for aortic diameter polygenic scores.

CONCLUSIONS

Genetic determinants of aortic function influence risk for stroke and coronary artery disease and may lead to novel targets for medical intervention.

Abstract 957: Prediction of patient response to targeted and immunotherapies from the tumor transcriptome in a wide set of indications and clinical trials

Background: Precision oncology is gradually advancing into mainstream clinical practice, demonstrating significant survival benefits. However, eligibility and response rates remain limited in many cases, calling for better predictive biomarkers.

Methods: We present ENLIGHT, a transcriptomics-based computational approach that identifies clinically relevant genetic interactions and uses them to predict a patient’s response to a variety of therapies in multiple cancer types, importantly, without training on previous treatment response data. Consequently, in addition to its ability to predict patients' response to approved and well-studied therapies, ENLIGHT can predict the response to new treatments in early development, even before clinical data has accumulated. Accordingly, we study ENLIGHT in two translationally relevant scenarios: Personalized Oncology (PO), aimed at prioritizing approved treatments to a given patient, and Clinical Trial Design (CTD), selecting the subset of most likely responders in a patient cohort.

Results: Evaluating ENLIGHT’s performance on 21 blinded clinical trial datasets spanning 11 indications and 15 different drugs in the PO setting, we show that it can effectively predict a patient’s treatment response across multiple therapies and cancer types, with an overall odds ratio of 2.59 (p=3.41e-8), and a 36% increase in response rate over the baseline (p=3.30e-13). Its prediction accuracy is better than other state-of-the-art transcriptomics-based signatures. Unlike most signatures that are prognostic or provide insights for only very few, specific treatments, ENLIGHT provides matching scores to a broad range of treatments. Quite strikingly, its performance is comparable to that of supervised predictors developed for specific indications and drugs. In combination with the IFN-γ signature, ENLIGHT achieves an odds ratio larger than 4 in predicting response to immune checkpoint therapy. In the CTD scenario, our results show that by excluding non-responders ENLIGHT can enhance clinical trial success for immunotherapies and other monoclonal antibodies, achieving &gt; 90% of the response rate attainable under an optimal exclusion strategy.

Conclusion: ENLIGHT is a powerful transcriptomics-based precision oncology pipeline developed by Pangea Biomed that broadly predicts response to both extant and novel targeted and immune therapies, going beyond context-specific biomarkers.

Citation Format: Gal Dinstag, Eldad D. Shulman, Efrat Elis, Doreen S. Ben-Zvi, Omer Tirosh, Eden Maimon, Isaac Meilijson, Emmanuel Elalouf, Boris Temkin, Philipp Vitkovsky, Eyal Schiff, Danh-Tai Hoang, Sanju Sinha, Nishanth Ulhas Nair, Joo Sang-Lee, Alejandro A. Schäffer, Ze'ev Ronai, Dejan Juric, Andrea B. Apolo, William L. Dahut, Stanley Lipkowitz, Raanan Berger, Razelle Kurzrock, Antonios Papanicolau-Sengos, Fatima Karzai, Mark R. Gilbert, Kenneth Aldape, Padma S. Rajagopal, Tuvik Beker, Eytan Ruppin, Ranit Aharonov. Prediction of patient response to targeted and immunotherapies from the tumor transcriptome in a wide set of indications and clinical trials [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 957.

Abstract PD1-10: Impact of Race on Clinical, Socioeconomic, and Genomic Characteristics, Clinical Trial Participation, and Receipt of Genotype-matched Therapy Among Patients with Metastatic Breast Cancer

Background: Clinical outcomes in breast cancer differ across racial and ethnic populations. We have previously demonstrated that receipt of genotype-matched therapy targeted to an actionable mutation may potentially improve patient outcomes (Vidula, CCR, 2021). We evaluated the impact of race on clinical, socioeconomic, and genomic characteristics, clinical trial participation, and receipt of genotype-matched therapy among patients with metastatic breast cancer (MBC). Methods: We conducted a retrospective study of patients with MBC at an academic institution who underwent cell-free DNA testing (cfDNA, Guardant360, 74 gene panel) as part of routine clinical care from 11/29/2016-11/2/2020. Patient demographics (including self-reported race and ethnicity) and clinical trial enrollment (at same institution) were determined by retrospective data collection. Mutations identified in cfDNA were characterized as actionable based on the variant interpretation performed by Guardant360 using vetted genomic databases, and receipt of genotype-matched therapy targeted to an actionable mutation was determined as previously described (Vidula, CCR, 2021). Pearson’s chi-squared and Wilcoxon rank-sum tests were used to compare categorical and continuous variables between groups, with p&lt; 0.05 indicating statistical significance. Results: Four hundred and twenty-five patients with MBC and cfDNA results were identified, of which 369 were White (87%), 27 Black (6.4%), 15 Hispanic (3.5%), and 14 Asian (3.3%). There were no significant differences in median age at MBC diagnosis (p=0.064), disease subtype distribution (p=0.74), proportions of de-novo/recurrent MBC (p=0.95), presence of visceral metastases (p=0.84), Charleston comorbidity index (p=0.93), menopausal status (p=0.3), and level of education (p=0.44) across racial groups. Higher proportions of non-primary English speakers were seen in Hispanic (80%) and Asian (29%) races (p&lt; 0.001). Median distance traveled to the institution also varied based on race, with White patients traveling further (White: 39.1 miles, Black: 21.8 miles, Hispanic 9.4 miles, Asian 9.1 miles, p&lt; 0.001). In addition, type of insurance varied based on race, with White patients having the highest rates of commercial insurance and Medicare, Black patients having the highest rate of state-supported insurance, and Asian patients having the highest uninsured rates (p&lt; 0.001). Clinical trial enrollment rates did not significantly differ by race (White: 44%, Black: 37%, Hispanic: 47%, and Asian 21%, p=0.34), but patients without insurance were significantly less likely to be enrolled on a trial than those with commercial insurance (p=0.03). The proportion of patients with ≥1 actionable mutation in cfDNA did not vary significantly by race (White: 78%, Black: 56%, Hispanic: 73%, Asian 86%, p=0.18) and the median number of actionable mutations found in cfDNA was similar across races (p=0.31). However, receipt of genotype-matched therapy targeted to an actionable mutation varied by race, with the highest rates of matched therapy in White patients (White: 28%, Black: 11%, Hispanic 13%, Asian 14%, p&lt; 0.001). After multivariable logistic regression adjusting for subtype, commercial insurance versus other insurance types, and proximity to the center, White patients remained significantly more likely to receive matched therapy (p=0.029). Conclusions: We observed significant race-based differences in non-English speaking status, insurance type, and median distance traveled to the institution. Racial/ethnic minority patients were less likely to receive genotype-matched therapy than White patients. Further research is needed to identify barriers and reduce disparities in access to precision medicine.

Citation Format: Rupali Sood, Lianne Ryan, Andrzej Niemierko, Laura M. Spring, Dejan Juric, Steven J. Isakoff, Seth A. Wander, Jennifer Shin, Naomi Ko, Leif Ellisen, Beverly Moy, Aditya Bardia, Neelima Vidula. Impact of Race on Clinical, Socioeconomic, and Genomic Characteristics, Clinical Trial Participation, and Receipt of Genotype-matched Therapy Among Patients with 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 PD1-10.

Abstract PD13-07: PD13-07 Combination therapy with the AKT inhibitor, ipatasertib, endocrine therapy, and a CDK4/6 inhibitor for hormone receptor positive (HR+)/HER2 negative metastatic breast cancer (MBC): results from the phase I TAKTIC trial

Background: Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) in combination with endocrine therapy (ET) provide significant clinical benefit in patients with HR+/HER2- metastatic breast cancer (MBC) and have become a standard of care treatment. Prior insights from tumor profiling and preclinical analyses suggest that AKT1 activation can induce CDK4/6i resistance. We hypothesized that targeting AKT1 following CDK4/6i progression may be an effective therapeutic strategy and conducted a clinical trial to evaluate both doublet (ET+AKTi) and triplet (ET+AKTIi+CDK 4/6i) therapy in the ≥ 2nd line MBC setting. Methods: TAKTIC is an open-label phase Ib clinical trial (clinicaltrials.gov NCT03959891) evaluating the combination of the AKT inhibitor ipatasertib (ipat) with fulvestrant (Arm A), an aromatase inhibitor (Arm B), or the triplet combination (Arm C) with fulvestrant + palbociclib (palbo). The primary objective is to evaluate the safety (NCI CTCAE 5.0) and tolerability of ipat in combination with endocrine therapy +/- CDK4/6i. Secondary objectives include clinical efficacy, as determined by objective response rate (RECIST v1.1), clinical benefit rate (CBR), progression-free survival (PFS), and overall survival (OS). Key inclusion criteria include unresectable HR+/HER2- MBC; at least 1 prior therapy for MBC including any CDK4/6i; up to 2 prior lines of chemotherapy for MBC (no limit on prior endocrine therapy). Here, we present an updated interim analysis from all study arms. Results: The trial completed accrual with 77 pts enrolled from June 2019 – February 2022, including 19 on Arm A, 16 on Arm B, and 42 on Arm C. Median age was 62 (range 32-88) and 65/77 pts (84%) received prior CDK4/6i (median no. of prior lines = 3, range 1-13). 56/77 pts (73%) had measurable disease at baseline and 50/77 pts (65%) had visceral metastases in the liver/lung (68% Arm A, 44% Arm B, 71% Arm C). Pts enrolled on Arms A and B received ipat at 400mg in combination with fulvestrant or an aromatase inhibitor, respectively. In Arm C, 27/42 pts enrolled into the dose escalation phase and received ipat + palbo at varying doses in combination with fulvestrant. Two DLTs were observed in the 300mg ipat + 125mg palbo cohort (grade 4 neutropenia ≥ 7 days). ET+400mg ipat + 100mg palbo was determined to be the recommended phase 2 dose (R2PD), and the remaining 15/42 pts on Arm C were treated at this dose level in the expansion phase. Treatment was well tolerated in all arms. Grade 3 and 4 toxicities included neutropenia (39/77, 50.6%), leukopenia (15/77, 19.5%), diarrhea (11/77, 14/3%), transaminitis (7/77, 9.1%), lymphopenia (6/77, 7.8%), rash (6/77, 7.8%), and thrombocytopenia (3/77, 3.9%). As of 6/28/2022, 16/77 pts remain on treatment. The median treatment duration for all pts is estimated at 6 months (range 0.5-39). Among the 56 pts with measurable disease, 11 had partial response (PR) and 32 had stable disease (SD) as the best response. CBR, defined as percentage of pts who achieved PR or SD &gt; 6 months, was 48% across the study (53% Arm A, 31% Arm B, 57% Arm C). The median PFS was 5.5 months (95% confidence interval [CI]: 3.8 – 7.4) and the median OS was 24.5 months (95% CI: 17.1 – 33.9). Conclusions: The combination of ipat with endocrine therapy +/- palbo is well tolerated in heavily pre-treated pts, with preliminary evidence of clinical activity. This trial demonstrates how molecular insights related to CDK4/6i resistance inform potential therapy combinations. Further studies are needed to evaluate AKTi-based combinations in pts with HR+ MBC.

Citation Format: Seth A. Wander, Jennifer C. Keenan, Andrzej Niemierko, Dejan Juric, Laura M. Spring, Jeffrey Supko, Neelima Vidula, Steven J. Isakoff, Lianne Ryan, Sarah Padden, Elizabeth Fisher, Amber Newton, Beverly Moy, Leif Ellisen, Douglas S. Micalizzi, Aditya Bardia. PD13-07 Combination therapy with the AKT inhibitor, ipatasertib, endocrine therapy, and a CDK4/6 inhibitor for hormone receptor positive (HR+)/HER2 negative metastatic breast cancer (MBC): results from the phase I TAKTIC trial [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 PD13-07.

Targeting TBK1 to overcome resistance to cancer immunotherapy

Despite the success of PD-1 blockade in melanoma and other cancers, effective treatment strategies to overcome resistance to cancer immunotherapy are lacking1,2. Here we identify the innate immune kinase TANK-binding kinase 1 (TBK1)3 as a candidate immune-evasion gene in a pooled genetic screen4. Using a suite of genetic and pharmacological tools across multiple experimental model systems, we confirm a role for TBK1 as an immune-evasion gene. Targeting TBK1 enhances responses to PD-1 blockade by decreasing the cytotoxicity threshold to effector cytokines (TNF and IFNγ). TBK1 inhibition in combination with PD-1 blockade also demonstrated efficacy using patient-derived tumour models, with concordant findings in matched patient-derived organotypic tumour spheroids and matched patient-derived organoids. Tumour cells lacking TBK1 are primed to undergo RIPK- and caspase-dependent cell death in response to TNF and IFNγ in a JAK-STAT-dependent manner. Taken together, our results demonstrate that targeting TBK1 is an effective strategy to overcome resistance to cancer immunotherapy.

Abstract P4-01-42: Pooled analysis of post-progression treatments after first-line ribociclib + endocrine therapy in patients with HR+/HER2− advanced breast cancer in the MONALEESA-2, -3, and -7 studies

Background: The MONALEESA (ML) studies showed significant PFS & OS benefits for 1L ribociclib (RIB) + endocrine therapy (ET) in patients (pts) with pre/peri & postmenopausal advanced breast cancer. The benefit of RIB beyond study treatment (tx) was also observed, with improvements in PFS2 & delays in time to 1st subsequent chemotherapy (CT). While there is currently no preferred tx for the next line post-progression on a CDK4/6 inhibitor (CDK4/6i), except alpelisib in pts with a PIK3CA mutation, guidelines encourage multiple lines of ET or ET-based therapies before switching to CT (except for visceral crisis). This pooled exploratory analysis of the ML studies examined outcomes of various tx strategies post progression on RIB + ET.

Methods: Data from pts receiving 1L therapy in ML-2, -3, & -7 (NSAI cohort only & excluding pts with early relapse [≤ 12 mo after end of (neo)adjuvant ET] whose prognosis is closer to that of 2L pts) were pooled & pts receiving 1st subsequent therapies after progression were analyzed. Three groups of subsequent therapies were assessed: ET only, CT, & targeted therapy. Subsequent CT comprises CT +/- any other therapy; targeted therapy includes CDK4/6i, mTORi, PI3Ki, AKTi, etc, +/- ET. Subsequent CT & targeted therapy groups are mutually exclusive. Median duration of study tx, 1st subsequent therapy, & OS (from randomization to death) were analyzed by KM methods. Weighted Cox regressions were performed using inversed propensity scoring matching method (inverse probability tx weighting [IPTW]) to ensure compatible pt characteristics between tx arms. These are not randomized comparisons; only baseline characteristics were used for the estimation of propensity scores in the IPTW, imbalance of prognostic factors at progression may exist.

Results: Median follow-up time was 74 mo. 461 pts treated with RIB (81%) & 440 (86%) with PBO discontinued study tx & received a subsequent therapy. In the RIB arms, the most common 1st subsequent therapies were ET only (40%), CT (29%), combination with targeted therapy (28%), & other (4%); for the PBO arms, 34% received CT as a 1st subsequent therapy & 31% each received ET only or combination with targeted therapy (5% received other). In 14% & 20% of pts in the RIB & PBO arms, the 1st subsequent therapy was a CDK4/6i, of these 31% & 12% were RIB. In general, regardless of type of 1st subsequent therapy, the duration of both the study tx & the 1st subsequent therapy was longer for pts treated with RIB vs PBO (Table). In both RIB & PBO arms, pts who received subsequent CT had the shortest duration on study tx, whereas those who received subsequent targeted therapy combination had the longest. Among pts on 1L RIB + ET, after matching pre-randomization baseline characteristics, subsequent CDK4/6i use was associated with the longest mOS (84 [84-NE] mo), followed by ET only (60 [51-68] mo), then a non-CDK4/6i targeted therapy (52 [43-72] mo); post-progression CT was associated with the shortest mOS (37 [32-48] mo).

Conclusions: This large, pooled analysis of the ML studies shows that, in general, duration of any subsequent therapy was numerically longer post-1L RIB + ET vs PBO + ET, & subsequent CT was used less frequently for pts on RIB vs PBO. Both findings confirm that upfront tx with RIB does not worsen pt outcomes. This trend in enhancement of outcomes of subsequent therapies seen with 1L RIB suggests a post-tx effect that merits further exploration.

Abstract P5-02-32: Differential Gene Mutation Landscape in Patients With PIK3CA-altered and Non-altered Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-negative Advanced Breast Cancer in the SOLAR-1 Clinical Study

Introduction: The phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) is found mutated (mut) in ~40% of patients (pts) with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2−) advanced breast cancer (ABC); some of these alterations can lead to PI3K pathway hyperactivation and are associated with endocrine resistance and poor prognosis in advanced disease. Alpelisib (ALP), an α-selective PI3K inhibitor and degrader, demonstrated clinical benefit in combination with fulvestrant (FUL) in the SOLAR-1 study in pts with PIK3CA-mut HR+, HER2− ABC. SOLAR-1 (NCT02437318) was a double-blind, placebo (PBO)-controlled, stratified, randomized (per PIK3CA-alt status as determined by QIAGEN PIK3CA RGQ PCR test), Phase III study of ALP in combination with FUL in pts with HR+, HER2− ABC who progressed on/after aromatase inhibitor therapy. Here, we compare the gene alteration landscape in pts with altered (alt) and non-alt PIK3CA and the efficacy of ALP + FUL in pts whose tumors have alterations in both selected genes or cell signaling pathways as well as PIK3CA-alt or non-alt status as determined by next-generation sequencing (NGS).

Methods: In this analysis, retrospective NGS analysis using the FoundationOne CDx 324-gene panel was performed on available FFPE tissue samples. In all, 398 pts were categorized into 2 cohorts based on NGS-tested PIK3CA status. The PIK3CA-alt cohort comprised 237 patients (ALP, n=120; PBO, n=117); the PIK3CA-non-alt cohort 161 patients (ALP, n=81; PBO, n=80). Selected genes altered in &gt;20 SOLAR-1 pts were investigated further. Clinical benefit was assessed by progression-free survival (PFS) based on gene alt status in the PIK3CA-alt and -non-alt cohorts. Hazard ratios (HR) for PFS were estimated using a multivariate Cox PH model by adjusting multiple clinical covariates including age, ECOG performance status, bone lesion, prior CDK4/6 inhibitor treatment, and lung/liver metastasis.

Results: PIK3CA-alt and -non-alt cohorts had differential genomic landscapes; differential PFS benefit was observed among the genes analyzed, including ARID1A, EMSY, FGFR2, MAP3K1, MYC, RAD21, RAD51C, TP53, and a gene set associated with the MAPK pathway. In most pts with analyzed gene alterations, numerically longer PFS was observed with ALP vs PBO in the PIK3CA-alt cohort than the -non-alt cohort, particularly pts with alterations in ARID1A (median [m] PFS for ALP vs PBO in PIK3CA-alt cohort: 22.11 vs 12.42 mo, HR 0.48; vs mPFS in PIK3CA-non-alt cohort: 6.21 vs 22.31 mo, HR 1.33) and MAP3K1 (PIK3CA-alt cohort: 17.25 vs 7.70 mo, HR 0.50; vs PIK3CA-non-alt cohort: 9.17 vs 5.26 mo, HR 1.32). Full results are found in the Table. Results should be interpreted with caution, as analyses used small sample sizes and were not adjusted for multiple testing.

Conclusions: A differential genomic landscape was observed in PIK3CA-alt and PIK3CA-non-alt populations. Clinical benefit of ALP vs PBO was observed in pts with PIK3CA-alt disease who also had alterations in analyzed genes and/or genes associated with the MAPK pathway. The data from this analysis suggest that, of the genes analyzed, only PIK3CA mutations can predict pt sensitivity to ALP.

Table. PFS in PIK3CA-altered PIK3CA-non-altered populations by gene alteration

Citation Format: Dejan Juric, Hope Rugo, Albert Reising, Chong Ma, Eva Ciruelos, Sibylle Loibl, Christian F. Singer, Joo Hyuk Sohn, Mario Campone, PierFranco Conte, Hiroji Iwata, Farhat Ghaznawi, Michelle Miller, Tetiana Taran, Faye Su, Fabrice Andre. Differential Gene Mutation Landscape in Patients With PIK3CA-altered and Non-altered Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-negative Advanced Breast Cancer in the SOLAR-1 Clinical 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 P5-02-32.

Abstract OT3-23-01: VELA: A first-in-human phase 1/2 study of BLU-222, a potent, selective cyclin-dependent kinase (CDK) 2 inhibitor in patients with cyclin E1 gene (CCNE1)-amplified or CDK4/6 inhibitor-resistant advanced solid tumors

Background The regulation of cell growth and proliferation is dependent on cyclins and CDKs. The formation of the cyclin D-CDK4/6 complex increases the expression of cyclin E1 and E2. Cyclin E1 and E2 bind to and activate CDK2; this results in a cyclin E/CDK2 complex that assists with downstream expression of DNA synthesis machinery. The use of CDK4/6 inhibitors such as palbociclib or ribociclib is an effective treatment in patients with hormone receptor-positive (HR+), human epithelial growth factor receptor-2 negative (HER2-) breast cancer; however, resistance to treatment eventually occurs. Aberrant cyclin E/CDK2 activity has been identified as a potential resistance mechanism by which tumors can evade CDK4/6 inhibitors. BLU-222 is an oral, investigational, potent, and selective CDK2 inhibitor. In preclinical studies, BLU-222 treatment in combination with ribociclib led to durable tumor regression in both CDK4/6-resistant and sensitive models of HR+HER2- breast cancer. Trial design VELA (NCT05252416) is an international, open-label, first-in-human phase 1/2 study evaluating the safety, tolerability, pharmacokinetics, pharmacodynamics, and efficacy of BLU-222 in adult patients with CCNE1-amplified tumors or with HR+HER2- breast cancer with disease progression on CDK4/6 inhibitors. In phase 1 and 2, patients aged ≥18 years with an Eastern Cooperative Oncology Group performance status 0–2 are eligible. In phase 2, all patients must have ≥1 measurable target lesion per Response Evaluation Criteria in Solid Tumors version 1.1. Primary endpoints include assessing the safety of BLU-222 as a single agent or BLU-222 in combination with either carboplatin or ribociclib and/or fulvestrant (phase 1 and 2), identifying the maximum tolerated dose and/or recommended phase 2 dose (phase 1), and determining the objective response rate (phase 2). In the phase 1 dose-escalation part, patients with any advanced solid tumor with progression on standard of care (SOC) will receive BLU-222; patients with gastric or endometrial cancer (EC) with progression on ≥2 prior therapies (including ≥1 platinum-based therapy) or with CCNE1-amplified platinum-resistant/refractory ovarian cancer (OC) will receive BLU-222 and carboplatin; patients with HR+HER- breast cancer with progression on CDK4/6 inhibitors will receive BLU-222, ribociclib, and fulvestrant. In the phase 2 dose-expansion part, patients with CCNE1-amplified tumors including EC (progression on ≥2 prior therapies), platinum-resistant/refractory OC, or other advanced solid tumors (progression after SOC) will receive BLU-222 monotherapy; patients with CCNE1-amplified platinum-resistant/refractory OC will receive BLU-222 and carboplatin; and patients with CDK4/6 inhibitor-resistant HR+HER2- breast cancer will receive BLU-222 and fulvestrant with/without ribociclib. Pharmacokinetic parameters will be calculated using standard non-compartmental methods from the plasma concentration–time data. Tissue biopsies will be collected during cycle 1 to assess the phosphorylation of retinoblastoma 1 (Rb1) protein which will be used as a pharmacodynamic marker to assess target inhibition. Dose escalation is ongoing and approximately 50 sites are anticipated to enroll patients across North America, Europe, and the Asia/Pacific region.

Citation Format: Manish R Patel, Dejan Juric, Brian S Henick, Kathleen N Moore, Doreen Do, Joshua Chapman, Hui Zhang, Maria Roche, Kate J Newberry, Mikael Rinne, Timothy A Yap. VELA: A first-in-human phase 1/2 study of BLU-222, a potent, selective cyclin-dependent kinase (CDK) 2 inhibitor in patients with cyclin E1 gene (CCNE1)-amplified or CDK4/6 inhibitor-resistant advanced solid tumors [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 OT3-23-01.

Abstract P1-13-07: Investigating NF1 Mutations in Circulating Tumor DNA of Patients with Hormone-receptor Positive (HR+) Breast Tumors Resistant to CDK4/6 Inhibition (CDK4/6i): A Retrospective Clinical Analysis

Background: CDK4/6 inhibitors (CDK4/6i) are standard of care for the management of HR+/HER2- metastatic breast cancer (MBC). Genomic alterations that drive resistance to CDK4/6i are diverse, and while the molecular landscape is heterogeneous, several mechanisms of CDK4/6i resistance converge on the RAS/MAPK and PI3K/AKT/mTOR signaling pathways. NF1 downregulates RAS and dampens cellular proliferation. Laboratory-based models demonstrate that loss of NF1 is associated with resistance to endocrine therapy (ET), and emergence of NF1 mutations (NF1m) are correlated with progressive disease (PD) in circulating tumor DNA (ctDNA). While NF1m may diminish CDK4/6i susceptibility, a clear relationship has not been elucidated. The primary objective of this study was to characterize patient (pt) response to CDK4/6i in NF1m HR+/HER2- MBC. Methods: We identified 47 pts with NF1m via a database with one or more ctDNA samples sequenced at variable time-points as part of routine care for MBC. NF1m were categorized as pathogenic (p)NF1m or variants of uncertain significance (VUS) based on their associated Guardant report. We identified 27 pts with HR+/HER2- MBC and NF1m that received at least 1 line of CDK4/6i in the metastatic setting. Intrinsic resistance was defined as PD &lt; 6 months on a CDK4/6i regimen, and acquired resistance was defined as PD &gt;6 months. Pts with intrinsic resistance or acquired resistance and NF1m detected post-PD were categorized as having a resistance phenotype potentially driven by NF1m. Pts with NF1m detected prior to therapy and &gt;6 months clinical response on a CDK4/6i were categorized as having NF1m tumors sensitive to CDK4/6i. Results: The NF1m cohort (n = 27) had 9 pts with pNF1m, while 18 pts expressed VUS. The median age at MBC diagnosis was 54 years, and 67% had visceral metastasis at ctDNA collection. Pts received a median of 1 prior line (range: 0 - 6) of ET or chemotherapy in the metastatic setting before CDK4/6i. Amongst pts with pathogenic variants (n = 9), we found 3 pts with pNF1m were intrinsically resistant to CDK4/6i. Acquired resistance was seen in 1 pt with pNF1m detected post-PD, and 2 pts had evidence of both acquired and subsequent intrinsic resistance to a later line of CDK4/6i. Overall, 67% (6/9) of pNF1m pts demonstrated a CDK4/6i resistance phenotype; mutant allele fraction (AF) ranged from 0.2% - 29.9%, and the mean maximum allele fraction (MAF) was 6.0%. Pre- and post-treatment samples were available on 3 pts with pNF1m, and 1 of these pts had an AF rise from 2.7% to 12.3% when comparing ctDNA pre- and post-CDK4/6i. ctDNA from 4 of 6 resistant tumors harbored other putative drivers including alterations in FGFR, KRAS, PTEN, and RB. We identified 2 counter-examples of pNF1m tumors sensitive to CDK4/6i. These pts expressed relatively low NF1m AF, ranging 0.1% - 0.5% with a mean MAF 0.3%. Another pNF1m pt had intrinsic resistance to initial CDK4/6i but was sensitive to later-line CDK4/6i. In the subgroup of pts with VUS-NF1m (n = 18), a more mixed picture of resistance and sensitivity was seen. 8 pts had intrinsic or acquired resistance, 8 pts had NF1m tumors sensitive to CDK4/6i, and 1 pt had evidence of both; 61% (n = 11) of pts expressed alterations in other resistance mediating genes. 1 pt stopped therapy due to toxicity rather than PD. Conclusions: Our work demonstrates that tumor expression of pNF1m may be associated with CDK4/6i resistance in pts with HR+/HER2- MBC, and allele fraction could be predictive of drug susceptibility. Tumors harboring VUS had varied sensitivity, suggesting that some of these mutations may not be pathogenic, and counter-examples of pNF1m MBC benefiting from CDK4/6i plus ET highlight the complexities in predicting drug response based on single gene alteration. Future effort is warranted to explore the potential impact of NF1 on CDK4/6i resistance, as well as the potential role for therapies targeting the MAPK pathway in this patient population.

Citation Format: Maxwell R. Lloyd, Lianne Ryan, Arielle J. Medford, Jennifer C. Keenan, Laura M. Spring, Neelima Vidula, Beverly Moy, Dejan Juric, Leif Ellisen, Aditya Bardia, Seth A. Wander. Investigating NF1 Mutations in Circulating Tumor DNA of Patients with Hormone-receptor Positive (HR+) Breast Tumors Resistant to CDK4/6 Inhibition (CDK4/6i): A Retrospective Clinical Analysis [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 P1-13-07.

Discovery of Targets for Immune-Metabolic Antitumor Drugs Identifies Estrogen-Related Receptor Alpha

Drugs that kill tumors through multiple mechanisms have the potential for broad clinical benefits. Here, we first developed an in silico multiomics approach (BipotentR) to find cancer cell-specific regulators that simultaneously modulate tumor immunity and another oncogenic pathway and then used it to identify 38 candidate immune-metabolic regulators. We show the tumor activities of these regulators stratify patients with melanoma by their response to anti-PD-1 using machine learning and deep neural approaches, which improve the predictive power of current biomarkers. The topmost identified regulator, ESRRA, is activated in immunotherapy-resistant tumors. Its inhibition killed tumors by suppressing energy metabolism and activating two immune mechanisms: (i) cytokine induction, causing proinflammatory macrophage polarization, and (ii) antigen-presentation stimulation, recruiting CD8+ T cells into tumors. We also demonstrate a wide utility of BipotentR by applying it to angiogenesis and growth suppressor evasion pathways. BipotentR (http://bipotentr.dfci.harvard.edu/) provides a resource for evaluating patient response and discovering drug targets that act simultaneously through multiple mechanisms.

SIGNIFICANCE

BipotentR presents resources for evaluating patient response and identifying targets for drugs that can kill tumors through multiple mechanisms concurrently. Inhibition of the topmost candidate target killed tumors by suppressing energy metabolism and effects on two immune mechanisms. This article is highlighted in the In This Issue feature, p. 517.

Abstract PD13-08: PD13-08 Phase 1 TROPION-PanTumor01 Study Evaluating Datopotamab Deruxtecan (Dato-DXd) in Unresectable or Metastatic Hormone Receptor–Positive/HER2–Negative Breast Cancer (BC)

Background: Datopotamab deruxtecan (Dato-DXd) is an antibody-drug conjugate (ADC) consisting of a humanized anti-TROP2 IgG1 monoclonal antibody covalently linked to a highly potent topoisomerase I (Topo I) inhibitor payload via a stable, tumor-selective, tetrapeptide-based cleavable linker. Dato-DXd demonstrated compelling single-agent antitumor activity in heavily pretreated patients (pts) with metastatic triple-negative BC (Krop, SABCS 2021). This is the first report of results from the TROPION-PanTumor01 study in pts with unresectable or metastatic hormone receptor–positive (HR+)/human epidermal growth factor receptor 2–negative (HER2−; including HER2-low and HER2-zero) BC.

Methods: TROPION-PanTumor01 (NCT03401385) is a phase 1, multicenter, open-label, 2-part dose-escalation/expansion study evaluating Dato-DXd in previously treated pts with solid tumors. Based on previous clinical findings and exposure-response results from pts with NSCLC, Dato-DXd 6 mg/kg IV Q3W is being evaluated in pts with unresectable or metastatic HR+/HER2− BC that progressed on standard therapies. The primary objectives were safety and tolerability. Tumor responses, including ORR (complete response [CR] + partial response [PR]) and DCR (CR + PR + stable disease [SD]), were assessed per RECIST version 1.1 by blinded independent central review.

Results: As of the April 29, 2022, data cutoff, 41 pts had received Dato-DXd (median follow-up, 10.9 mo [range, 7-13]); 9 pts were ongoing. The primary cause of treatment discontinuation was disease progression (63%; progressive disease [PD] or clinical progression). Median age was 57 y (range, 33-75); 54% had de novo metastatic disease. Pts were heavily pretreated (Table) with a median of 5 (range, 3-10) prior regimens in the advanced setting; 95% had prior CDK4/6i (adjuvant/metastatic). Median time from initial treatment for metastatic disease to the first dose of Dato-DXd was 42.7 mo (range, 10.2-131.1). Treatment-emergent adverse events (TEAEs; all cause) were observed in 98% (any grade) and 41% (grade ≥3) of pts. Most common TEAEs (any grade, grade ≥3) were stomatitis (80%, 10%), nausea (56%, 0%), fatigue (46%, 2%), and alopecia (37%, 0%). Serious TEAEs were observed in 6 pts (15%); 1 pt died due to dyspnea, which was not considered to be treatment related. Dose reductions occurred in 5 pts due to stomatitis (n=3), fatigue (n=2), keratitis (n=1), and decreased appetite (n=1) (&gt;1 AE per pt); 14 pts had treatment delayed due to stomatitis (n=8), retinopathy (n=1), dysphagia (n=1), fatigue (n=1), malaise (n=1), COVID-19 (n=1), cellulitis (n=1), urinary tract infection (n=1), decreased lymphocyte count (n=1), and nasal congestion (n=1; &gt;1 AE per pt). Three pts discontinued treatment due to keratitis (n=1) and pneumonitis (n=2); 1 case of pneumonitis was adjudicated as grade 2 drug-related interstitial lung disease. The ORR was 29% (11 confirmed PRs; 1 pending confirmation), the DCR was 85% (35/41), and the clinical benefit rate (CR + PR + SD ≥6 mo) was 41% (17/41).

Conclusions: Dato-DXd demonstrated a manageable safety profile and encouraging antitumor activity, with high disease control in heavily pretreated pts, the majority having received prior CDK4/6i. Based on these findings, the TROPION-Breast01 (NCT05104866) randomized phase 3 study comparing 2L+ Dato-DXd vs investigator’s choice chemotherapy is currently enrolling pts with HR+/HER2− BC.

Prior Therapies in the Adjuvant or Metastatic Setting

Citation Format: Funda Meric-Bernstam, Ian Krop, Dejan Juric, Takahiro Kogawa, Erika Hamilton, Alexander I. Spira, Toru Mukohara, Takuya Tsunoda, Senthil Damodaran, Jonathan Greenberg, Wen Gu, Fumiaki Kobayashi, Hong Zebger-Gong, Yui Kawasaki, Rie Wong, Aditya Bardia. PD13-08 Phase 1 TROPION-PanTumor01 Study Evaluating Datopotamab Deruxtecan (Dato-DXd) in Unresectable or Metastatic Hormone Receptor–Positive/HER2–Negative Breast Cancer (BC) [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 PD13-08.

Abstract P4-09-12: Baseline and End-of-Treatment Biomarkers in Patients With PIK3CA-Mutated, Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Advanced Breast Cancer From BYLieve Study Cohorts A and B

Introduction: Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) is mutated in ~40% of patients (pts) with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2−) advanced breast cancer (ABC). PIK3CA mutations are associated with resistance to endocrine therapy (ET) and worse overall survival. Alpelisib (ALP), an α-selective PI3K inhibitor and degrader, is indicated in combination with fulvestrant (FUL) for pts with PIK3CA-mutated (mut) HR+, HER2− ABC following progression on/after ET-based treatments. In the Phase 2, open-label, 3-cohort, noncomparative BYLieve study, clinical benefit of ALP in combination with ET was observed in the post-cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) setting in pts with PIK3CA-mut, HR+, HER2− ABC. Here we report the results of a biomarker analysis using paired baseline (Cycle 1 Day 1) and end-of-treatment (EOT) circulating tumor DNA (ctDNA) samples from pts in BYLieve Cohorts A and B.

Methods: In the BYLieve study, pts with PIK3CA-mut, HR+, HER2− ABC had CDK4/6i + aromatase inhibitor (Cohort A; N=127) or CDK4/6i + FUL (Cohort B; N=126) as treatment immediately prior to receiving ALP + FUL and ALP + letrozole, respectively. In this biomarker analysis, gene alterations were detected in ctDNA at baseline and EOT using next-generation sequencing (PanCancer V2 panel). Pts included in this interim analysis had confirmed PIK3CA mutations and matched baseline/EOT samples with enough sequencing coverage and ctDNA fraction to detect mutations at both time points. ctDNA fractions, tumor mutation burden (TMB) distributions, genomic landscapes, gain/loss of PIK3CA and estrogen receptor 1 (ESR1), chromosome 8/11 amplification profiles, and alterations in PI3K pathway and potential CDK4/6i resistance markers were assessed across time points. Sample sizes were small; results should thus be interpreted with caution.

Results: Forty-three pts were included in the Cohort A biomarker population and 40 pts were included in Cohort B. ctDNA fraction was numerically higher at EOT compared with baseline in both cohorts; further analyses will be presented. In Cohort A, no significant differences were observed in TMB at EOT compared with baseline (P=0.21). In Cohort B, TMB was higher at EOT compared with baseline (P=0.053). Chromosome 8/11 amplifications were consistent between baseline and EOT for both cohorts. Small variations were observed in ESR1/PIK3CA mutations between baseline and EOT on both cohorts (Table). The status of potential CDK4/6i resistance markers was relatively unchanged at EOT (Table). Loss-of-function mutations in PTEN, a known PI3K inhibitor resistance marker, increased from 9% at baseline to 14% at EOT in Cohort A and from 12% at baseline to 22% at EOT in Cohort B.

Conclusions: Between baseline and EOT, only small variations in gene alterations in PIK3CA-mutated HR+, HER2– ABC were observed in the post-CDK4/6i setting. As the disease progressed, increases in loss-of-function mutations in PTEN at EOT in both Cohorts A and B suggested loss of PTEN in PI3K pathway may drive resistance to ALP. Early intervention with ALP, when the tumor is particularly driven by PIK3CA oncogenic mutations and before it develops more genomic complexity, may potentially provide better clinical outcomes.

Table. Gene Alteration Gain/Loss at Baseline/EOT Across Cohorts A and B

Citation Format: Dejan Juric, Nicholas Turner, Sherene Loi, Fabrice Andre, Stephen K. Chia, Komal Jhaveri, Patrick Neven, Rebecca Dent, Eva Ciruelos, Mukta Joshi, Estelle Roux, Heather Patino, Murat Akdere, Hope Rugo. Baseline and End-of-Treatment Biomarkers in Patients With PIK3CA-Mutated, Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative Advanced Breast Cancer From BYLieve Study Cohorts A and B [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 P4-09-12.

Identifying Early-Phase Clinical Trial Participants at Risk for Experiencing Worse Clinical Outcomes

PURPOSE

To identify early-phase clinical trial (EP-CT) participants at risk for experiencing worse clinical outcomes and describe receipt of supportive care services.

METHODS

A retrospective review of the electronic health records of consecutive patients enrolled in EP-CTs from 2017 to 2019 examined baseline characteristics, clinical outcomes, and receipt of supportive care services. The validated Royal Marsden Hospital (RMH) prognosis score was calculated using data at the time of EP-CT enrollment (scores range from 0 to 3; scores ≥ 2 indicate poor prognosis). Differences in patient characteristics, clinical outcomes, and receipt of supportive care services were compared on the basis of RMH scores.

RESULTS

Among 350 patients (median age = 63.2 years [range, 23.0-84.3 years], 57.1% female, 98.0% metastatic cancer), 31.7% had an RMH score indicating a poor prognosis. Those with poor prognosis RMH scores had worse overall survival (hazard ratio [HR], 2.00; P < .001), shorter time on trial (HR, 1.53; P < .001), and lower likelihood of completing the dose-limiting toxicity period (odds ratio, 0.42; P = .006) versus those with good prognosis scores. Patients with poor prognosis scores had greater risk of emergency room visits (HR, 1.66; P = .037) and hospitalizations (HR, 1.69; P = .016) while on trial, and earlier hospice enrollment (HR, 2.22; P = .006). Patients with poor prognosis scores were significantly more likely to receive palliative care consultation (46.8% v 27.6%; P < .001), but not other supportive care services.

CONCLUSION

This study found that RMH prognosis score could identify patients at risk for decreased survival, shorter time on trial, and greater use of health care services. The findings underscore the need to develop supportive care interventions targeting EP-CT participants' distinct needs.

Therapeutic Role of Tamoxifen for Triple-Negative Breast Cancer: Leveraging the Interaction Between ERβ and Mutant p53

The absence of effective therapeutic targets and aggressive nature of triple-negative breast cancer (TNBC) renders this disease subset difficult to treat. Although estrogen receptor beta (ERβ) is expressed in TNBC, studies on its functional role have yielded inconsistent results. However, recently, our preclinical studies, along with other observations, have shown the potential therapeutic utility of ERβ in the context of mutant p53 expression. The current case study examines the efficacy of the selective estrogen receptor modulator tamoxifen in p53-mutant TNBC with brain metastases. Significant increase in ERβ protein expression and anti-proliferative interaction between mutant p53 and ERβ were observed after cessation of tamoxifen therapy, with significant regression of brain metastases. This case study provides supporting evidence for the use of tamoxifen in p53-mutant, ERβ+TNBC, especially in the setting of brain metastasis.

Clinically oriented prediction of patient response to targeted and immunotherapies from the tumor transcriptome

BACKGROUND

Precision oncology is gradually advancing into mainstream clinical practice, demonstrating significant survival benefits. However, eligibility and response rates remain limited in many cases, calling for better predictive biomarkers.

METHODS

We present ENLIGHT, a transcriptomics-based computational approach that identifies clinically relevant genetic interactions and uses them to predict a patient's response to a variety of therapies in multiple cancer types without training on previous treatment response data. We study ENLIGHT in two translationally oriented scenarios: personalized oncology (PO), aimed at prioritizing treatments for a single patient, and clinical trial design (CTD), selecting the most likely responders in a patient cohort.

FINDINGS

Evaluating ENLIGHT's performance on 21 blinded clinical trial datasets in the PO setting, we show that it can effectively predict a patient's treatment response across multiple therapies and cancer types. Its prediction accuracy is better than previously published transcriptomics-based signatures and is comparable with that of supervised predictors developed for specific indications and drugs. In combination with the interferon-γ signature, ENLIGHT achieves an odds ratio larger than 4 in predicting response to immune checkpoint therapy. In the CTD scenario, ENLIGHT can potentially enhance clinical trial success for immunotherapies and other monoclonal antibodies by excluding non-responders while overall achieving more than 90% of the response rate attainable under an optimal exclusion strategy.

CONCLUSIONS

ENLIGHT demonstrably enhances the ability to predict therapeutic response across multiple cancer types from the bulk tumor transcriptome.

FUNDING

This research was supported in part by the Intramural Research Program, NIH and by the Israeli Innovation Authority.

Sotorasib in KRAS p.G12C-Mutated Advanced Pancreatic Cancer

BACKGROUND

KRAS p.G12C mutation occurs in approximately 1 to 2% of pancreatic cancers. The safety and efficacy of sotorasib, a KRAS G12C inhibitor, in previously treated patients with KRAS p.G12C-mutated pancreatic cancer are unknown.

METHODS

We conducted a single-group, phase 1-2 trial to assess the safety and efficacy of sotorasib treatment in patients with KRAS p.G12C-mutated pancreatic cancer who had received at least one previous systemic therapy. The primary objective of phase 1 was to assess safety and to identify the recommended dose for phase 2. In phase 2, patients received sotorasib at a dose of 960 mg orally once daily. The primary end point for phase 2 was a centrally confirmed objective response (defined as a complete or partial response). Efficacy end points were assessed in the pooled population from both phases and included objective response, duration of response, time to objective response, disease control (defined as an objective response or stable disease), progression-free survival, and overall survival. Safety was also assessed.

RESULTS

The pooled population from phases 1 and 2 consisted of 38 patients, all of whom had metastatic disease at enrollment and had previously received chemotherapy. At baseline, patients had received a median of 2 lines (range, 1 to 8) of therapy previously. All 38 patients received sotorasib in the trial. A total of 8 patients had a centrally confirmed objective response (21%; 95% confidence interval [CI], 10 to 37). The median progression-free survival was 4.0 months (95% CI, 2.8 to 5.6), and the median overall survival was 6.9 months (95% CI, 5.0 to 9.1). Treatment-related adverse events of any grade were reported in 16 patients (42%); 6 patients (16%) had grade 3 adverse events. No treatment-related adverse events were fatal or led to treatment discontinuation.

CONCLUSIONS

Sotorasib showed anticancer activity and had an acceptable safety profile in patients with KRAS p.G12C-mutated advanced pancreatic cancer who had received previous treatment. (Funded by Amgen and others; CodeBreaK 100 ClinicalTrials.gov number, NCT03600883.).

Implementation and Clinical Adoption of Precision Oncology Workflows Across a Healthcare Network

BACKGROUND

Precision oncology relies on molecular diagnostics, and the value-proposition of modern healthcare networks promises a higher standard of care across partner sites. We present the results of a clinical pilot to standardize precision oncology workflows.

METHODS

Workflows are defined as the development, roll-out, and updating of disease-specific molecular order sets. We tracked the timeline, composition, and effort of consensus meetings to define the combination of molecular tests. To assess clinical impact, we examined order set adoption over a two-year period (before and after roll-out) across all gastrointestinal and hepatopancreatobiliary (GI) malignancies, and by provider location within the network.

RESULTS

Development of 12 disease center-specific order sets took ~9 months, and the average number of tests per indication changed from 2.9 to 2.8 (P = .74). After roll-out, we identified significant increases in requests for GI patients (17%; P < .001), compliance with testing recommendations (9%; P < .001), and the fraction of "abnormal" results (6%; P < .001). Of 1088 GI patients, only 3 received targeted agents based on findings derived from non-recommended orders (1 before and 2 after roll-out); indicating that our practice did not negatively affect patient treatments. Preliminary analysis showed 99% compliance by providers in network sites, confirming the adoption of the order sets across the network.

CONCLUSION

Our study details the effort of establishing precision oncology workflows, the adoption pattern, and the absence of harm from the reduction of non-recommended orders. Establishing a modifiable communication tool for molecular testing is an essential component to optimize patient care via precision oncology.

Aortic Cellular Diversity and Quantitative Genome-Wide Association Study Trait Prioritization Through Single-Nuclear RNA Sequencing of the Aneurysmal Human Aorta

BACKGROUND

Mural cells in ascending aortic aneurysms undergo phenotypic changes that promote extracellular matrix destruction and structural weakening. To explore this biology, we analyzed the transcriptional features of thoracic aortic tissue.

METHODS

Single-nuclear RNA sequencing was performed on 13 samples from human donors, 6 with thoracic aortic aneurysm, and 7 without aneurysm. Individual transcriptomes were then clustered based on transcriptional profiles. Clusters were used for between-disease differential gene expression analyses, subcluster analysis, and analyzed for intersection with genetic aortic trait data.

RESULTS

We sequenced 71 689 nuclei from human thoracic aortas and identified 14 clusters, aligning with 11 cell types, predominantly vascular smooth muscle cells (VSMCs) consistent with aortic histology. With unbiased methodology, we found 7 vascular smooth muscle cell and 6 fibroblast subclusters. Differentially expressed genes analysis revealed a vascular smooth muscle cell group accounting for the majority of differential gene expression. Fibroblast populations in aneurysm exhibit distinct behavior with almost complete disappearance of quiescent fibroblasts. Differentially expressed genes were used to prioritize genes at aortic diameter and distensibility genome-wide association study loci highlighting the genes JUN, LTBP4 (latent transforming growth factor beta-binding protein 1), and IL34 (interleukin 34) in fibroblasts, ENTPD1, PDLIM5 (PDZ and LIM domain 5), ACTN4 (alpha-actinin-4), and GLRX in vascular smooth muscle cells, as well as LRP1 in macrophage populations.

CONCLUSIONS

Using nuclear RNA sequencing, we describe the cellular diversity of healthy and aneurysmal human ascending aorta. Sporadic aortic aneurysm is characterized by differential gene expression within known cellular classes rather than by the appearance of novel cellular forms. Single-nuclear RNA sequencing of aortic tissue can be used to prioritize genes at aortic trait loci.

Time toxicity in early phase clinical trials (EP-CTs)

236

Background: EP-CTs are an increasingly important treatment option for patients with cancer, yet often require intensive monitoring. Little is known about the time that EP-CT participants spend in-hospital, and how that time compares to study requirements. Methods: We retrospectively reviewed the electronic health record (EHR) of consecutive patients enrolled in EP-CTs at Massachusetts General Hospital from 2017-2019 to obtain patient characteristics (demographics and clinical factors) and EP-CT investigational agent (immunomodulatory therapy [IM], targeted inhibitor [TI], antibody drug conjugate [ADC]/chemotherapy prodrug). We identified protocol requirements by reviewing the study calendar for in-hospital days for any reason, including clinician visits and diagnostic tests. We identified the real-world number of days spent at the hospital by reviewing the EHR for in-hospital days. We used descriptive statistics to compare patient characteristics and outcomes for those with higher time toxicity, defined as 5+ real-world visits during the first 28 days on trial, versus lower time toxicity. Results: Among 421 patients (median age = 63.0 years, 56.9% female, 97.6% metastatic disease), 43.2% participated in IM trials, 43.0% TI, and 13.8% ADC. Most common tumor types were gastrointestinal (GI) (22.3%) and lung (20.0%). Over the first 28 days on trial, protocol requirements listed an average of 5.2 in-hospital days, yet real-world data demonstrated that patients had an average of 6.6 in-hospital days (p < 0.001). TI trial participants had the highest average number of anticipated protocol visits compared with those on other trials (5.5 [TI] vs 5.3 [ADC] vs 5.0 [IM], p = 0.027). In real-world data, those on ADC trials had the highest average number of visits (7.5 [ADC] vs 7.1 [TI] vs 5.7 [IM], p < 0.001). Those with 5+ real-world visits during the first 28 days were more likely to have GI cancer (25.8% vs 13.9%, p = 0.011) and less likely to have lung cancer (16.7% vs 27.9%, p = 0.011). Patients with more visits were also less likely to have traveled 50+ miles to the hospital (48.8% vs 59.8%, p = 0.04). Notably, 19.5% of patients (N = 82) were hospitalized during the first 28 days on trial, with an average length of stay of 4.9 days. Those with 5+ visits had fewer days, on average, from trial start to admission (371.9 vs 650.8, p < 0.001) and fewer days on trial (mean 156.0 vs 235.0, p = 0.001). There was no significant difference in days from trial start to death for those with higher versus lower time toxicity (mean 464.6 vs 526.4, p = 0.177). Conclusions: EP-CTs represent a potentially time-intensive treatment option, as we found that patients spend over one-fifth of their first 28 days on trial at the hospital for various visits. Our findings indicate that patients may often experience more in-hospital days than what the protocol states. These data could help inform patient-clinician discussions regarding EP-CT participation and the potential time toxicity involved.

Expert consensus recommendations for managing hyperglycemia and rash in patients with PIK3CA-mutated, hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2–) advanced breast cancer (ABC) treated with alpelisib (ALP)

422

Background: ALP is a PI3Kα inhibitor and degrader approved with fulvestrant for the treatment (tx) of patients (pts) with PIK3CA-mutated, HR+, HER2– ABC. Hyperglycemia (HG) and rash are expected adverse events with ALP tx and remain a challenge for physicians and pts. Management guidance is primarily based on clinical trial experience, which is not necessarily reflective of real-world pts. Here we report guidance for optimizing prevention and management of HG and rash in pts taking ALP based on an integrated Delphi panel, a systematic, validated approach to organize consensus from experts in the absence of definitive evidence. Methods: Two modified Delphi panels were conducted, focusing on HG and rash, respectively. Each panel included 4 oncologists, 4 endocrinologists or dermatologists, 1 clinical pharmacist, and 1 pt advocate. Experts were asked to rate appropriateness of 908 interventions for HG and 348 for rash on hypothetical pt scenarios on a 1 (highly inappropriate) to 9 (highly appropriate) scale. Results were reviewed at virtual meetings, after which experts repeated the rating. The level of agreement or disagreement was determined using the median scores and dispersion from the final rating, and this level of agreement was used to develop consensus statements and tx algorithms. Results: Per the HG panel, (a) ALP tx is appropriate in individuals with HbA1c 6.5% to < 8% with a pre-tx endocrinology consult; (b) low carbohydrate diet is appropriate in all pts starting ALP; (c) prophylactic metformin is appropriate in pts with baseline HbA1c 5.7%-6.4%; may also be appropriate in pts with HbA1c < 5.7%; (d) after metformin, an SGLT2 inhibitor or a thiazolidinedione is an appropriate second-/third-line anti-HG agent (or first-line in metformin-intolerant pts), while insulin is not. Per the rash panel, (a) prophylactic nonsedating (NS) H1 antihistamines (standard dose) are appropriate for all pts; (b) starting/escalating NS H1 antihistamines and topical steroids (TS) is the preferred first step for managing rash; (c) it is appropriate to add, but not replace with, a sedating H1 antihistamine, if response to high-dose, NS option is inadequate, and to add an H2 antihistamine if response is still inadequate; (d) it is appropriate to hold ALP and start oral corticosteroids (OCS) if rash affects > 30% body surface area and is recurrent or has moderate/severe symptoms; (e) if angioedema is present, it is appropriate to either hold ALP and start OCS, or permanently discontinue ALP tx. Conclusions: Until further evidence is available, these expert recommendations provide guidance on prevention and management of HG and rash related to ALP tx in routine clinical practice.

Patient-reported hope, quality of life, symptom burden, coping, and financial toxicity in early-phase clinical trial participants

275

Background: Early phase clinical trials (EP-CTs) investigate novel treatment options in oncology, with recent advances in personalized therapy leading to improved outcomes and offering hope to patients with cancer. However, little research has sought to understand associations of patient-reported hope with quality of life (QOL), symptom burden, coping, and financial toxicity in EP-CT participants. Methods: We prospectively enrolled consecutive adults with cancer participating in EP-CTs at Massachusetts General Hospital from 04/2021-05/2022. Participants completed baseline surveys prior to treatment initiation that assessed hope (Herth Hope Index [HHI], higher scores indicate greater hope), QOL (Functional Assessment of Cancer Therapy-General), symptom burden (physical: Edmonton Symptom Assessment System [ESAS]; psychological: Patient Health Questionaire-4 [PHQ4]), coping (Brief COPE: self-blame, acceptance, denial, emotional support, active, behavioral disengagement), and financial toxicity (COST tool, higher scores indicate greater financial wellbeing). We used regression models to determine associations of hope scores with patient-reported QOL, symptom burden, coping, and financial toxicity. Results: Of 157 eligible patients, we enrolled 129 (enrollment rate 82.2%, median age = 62.5 years [range 33.0-83.0], 53.9% female, and 96.0% metastatic cancer). Most common cancer types were gastrointestinal (37.5%), breast (20.3%), lung (8.6%), and head and neck (7.8%). Patients had an average HHI score of 27.5 (range 15.3 – 36.0), with 30.5% reporting high levels of hope. We found associations of higher hope scores with better QOL (B = 0.24, p < 0.001) and lower symptom burden (ESAS-physical: B = -0.14, p < 0.001; PHQ4-depression: B = -2.07, p < 0.001; PHQ4-anxiety: B = -0.93, p = 0.001). We also found that hope scores were associated with patients’ coping (self-blame [B = -1.44, p < 0.001]; acceptance [B = 1.40, p < 0.001], denial [B = -1.12, p = 0.004], emotional support [B = 0.99, p < 0.001], active [B = 1.02. p = 0.001], behavioral disengagement [B = -2.52, p < 0.001]). Lastly, we found that higher hope scores were associated with greater financial wellbeing (B = 0.11, p = 0.026). Conclusions: In this prospective cohort study, we demonstrated a substantial proportion of EP-CT participants had high baseline hope and identified associations of hope scores with other important patient-reported outcomes. Specifically, we found novel associations of higher hope scores with better QOL, lower symptom burden, more adaptive coping mechanisms, and greater financial wellbeing, underscoring the importance of targeting these patient-reported outcomes when seeking to enhance the care experience of EP-CT participants.

The Clinical Landscape of Cell-Free DNA Alterations in 1,671 Patients with Advanced Biliary Tract Cancer

BACKGROUND

Targeted therapies have transformed clinical management of advanced biliary tract cancer (BTC). Cell-free DNA (cfDNA) analysis is an attractive approach for cancer genomic profiling that overcomes many limitations of traditional tissue-based analysis. We examined cfDNA as a tool to inform clinical management of patients with advanced BTC and generate novel insights into BTC tumor biology.

PATIENTS AND METHODS

We analyzed next-generation sequencing data of 2,068 cfDNA samples from 1,671 patients with advanced BTC generated with Guardant360. We performed clinical annotation on a multi-institutional subset (n=225) to assess intra-patient cfDNA-tumor concordance and the association of cfDNA variant allele fraction (VAF) with clinical outcomes.

RESULTS

Genetic alterations were detected in cfDNA in 84% of patients, with targetable alterations detected in 44% of patients. FGFR2 fusions, IDH1 mutations, and BRAF V600E were clonal in majority of cases, affirming these targetable alterations as early driver events in BTC. Concordance between cfDNA and tissue for mutation detection was high for IDH1 mutations (87%) and BRAF V600E (100%), and low for FGFR2 fusions (18%). cfDNA analysis uncovered novel putative mechanisms of resistance to targeted therapies, including mutation of the cysteine residue (FGFR2 C492F) to which covalent FGFR inhibitors bind. High pre-treatment cfDNA VAF associated with poor prognosis and shorter response to chemotherapy and targeted therapy. Finally, we report the frequency of promising targets in advanced BTC currently under investigation in other advanced solid tumors, including KRAS G12C (1.0%), KRAS G12D (5.1%), PIK3CA mutations (6.8%), and ERBB2 amplifications (4.9%).

CONCLUSIONS

These findings from the largest and most comprehensive study to date of cfDNA from patients with advanced BTC highlight the utility of cfDNA analysis in current management of this disease. Characterization of oncogenic drivers and mechanisms of therapeutic resistance in this study will inform drug development efforts to reduce mortality for patients with BTC.

Immunogenicity of SARS-CoV-2 vaccines in patients with breast cancer

Purpose

To explore the immunogenicity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines in patients with breast cancer based on type of anticancer treatment.

Methods

Patients with breast cancer had anti-spike antibody concentrations measured ⩾14 days after receiving a full SARS-CoV-2 vaccination series. The primary endpoint was IgA/G/M anti-spike antibody concentration. Multiple regression analysis was used to analyze log₁₀-transformed antibody titer concentrations.

Results

Between 29 April and 20 July 2021, 233 patients with breast cancer were enrolled, of whom 212 were eligible for the current analysis. Patients who received mRNA-1273 (Moderna) had the highest antibody concentrations [geometric mean concentration (GMC) in log₁₀: 3.0 U/mL], compared to patients who received BNT162b2 (Pfizer) (GMC: 2.6 U/mL) (multiple regression adjusted p = 0.013) and Ad26.COV2.S (Johnson & Johnson/Janssen) (GMC: 2.6 U/mL) (p = 0.071). Patients receiving cytotoxic therapy had a significantly lower antibody titer GMC (2.5 U/mL) compared to patients on no therapy or endocrine therapy alone (3.0 U/mL) (p = 0.005). Patients on targeted therapies (GMC: 2.7 U/mL) also had a numerically lower GMC compared to patients not receiving therapy/on endocrine therapy alone, although this result was not significant (p = 0.364). Among patients who received an additional dose of vaccine (n = 31), 28 demonstrated an increased antibody response that ranged from 0.2 to >4.4 U/ mL.

Conclusion

Most patients with breast cancer generate detectable anti-spike antibodies following SARS-CoV-2 vaccination, though systemic treatments and vaccine type impact level of response. Further studies are needed to better understand the clinical implications of different antibody levels, the effectiveness of additional SARS-CoV-2 vaccine doses, and the risk of breakthrough infections among patients with breast cancer.

Abstract 5162: TuFEst: a sensitive and cost-effective pan-cancer detection approach with accurate tumor fraction estimation

Detecting cancer at early stages or upon recurrence is critical to decreasing cancer morbidity and mortality. We developed TuFEst (Tumor Fraction Estimator), a cost-effective computational approach for pan-cancer detection and tumor burden estimation from ultra-low coverage whole genome sequencing (~0.1x, ULP-WGS) of minimally invasive cell-free DNA (cfDNA). Current state-of-the-art methods estimate tumor fraction (TF) from ULP-WGS depending exclusively on total copy number variation, which loses tumor signal in either copy number-quiet tumors or tumors with copy-neutral loss-of-heterozygosity. Additionally, it is difficult in many cases to distinguish clonal from sub-clonal copy-number events, therefore complicating the ability to estimate tumor fraction. On the other hand, fragments shed into the blood from cancer cells, i.e., circulating tumor DNA (ctDNA), of various cancer types show significantly different length distribution than that from normal cells in healthy donors. By synergistically integrating both (i) copy number variation and (ii) altered fragment length signals, TuFEst successfully achieved higher sensitivity and more accurate TF estimation than current methods in &gt;200 cfDNA samples across different cancer types, even in low tumor-fraction cases (TF &lt; 0.1%). Application of TuFEst to serial cfDNA samples from blood biopsies demonstrate its utility in accurately estimating TF in ~100 cfDNAs, suggesting that TuFEst can be used to detect early cancer recurrence during different treatments. In one breast cancer patient receiving CDK4/6 therapy, TuFEst indicated disease progression 262 days earlier than routine imaging. Altogether, our work suggests that accurate TF estimation from cfDNA can not only aid in detecting cancer at early stages but also provide evidence of disease progression during treatment. We believe that such a non-invasive, cost-effective, pan-cancer detection method will benefit both initial cancer screening and monitoring of resistance to therapy in clinical applications.

Citation Format: Ziao Lin, Chip Stewart, Elizabeth E. Martin, Brian P. Danysh, Raquel A. Jacobs, Kara Slowik, Lee Lawton, Elizabeth Lightbody, Kahn Rhrissorrakrai, Filippo Utro, Chaya Levovitz, Carrie Cibulskis, Irene M. Ghobrial, Margaret Shipp, Ryan B. Corcoran, Dejan Juric, Laxmi Parida, Heather A. Parsons, Gad Getz. TuFEst: a sensitive and cost-effective pan-cancer detection approach with accurate tumor fraction estimation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5162.

Abstract 2638: Sacituzumab Govitecan, combination with PARP inhibitor, Talazoparib, in metastatic triple-negative breast cancer (TNBC): Translational investigation

Background: Sacituzumab Govitecan (SG), the first antibody-drug conjugate approved for metastatic TNBC (mTNBC), is comprised of SN-38 (active metabolite of irinotecan), a topoisomerase I (TOP1) inhibitor, coupled via a hydrolyzable linker to monoclonal antibody targeting trophoblast cell surface antigen 2 (Trop-2), an antigen overexpressed in mTNBC. Poly (ADP-ribose) polymerase inhibitors (PARPi) block resolution of TOP1 cleavage complexes (TOP1CCs) induced by TOP1 inhibitors, thus unmasking the inability of remaining pathways to repair DNA damage. However, previous clinical trials combining PARPi with standard TOP1 inhibitors (irinotecan, topotecan) were terminated early due to dose-limiting myelosuppression. We evaluated the combination of SG with PARP inhibitor in both pre-clinical models and phase 1b clinical trial.

Methods and Results: In pre-clinical models we demonstrated that the targeted antibody-based delivery of SN-38 increased the ratio of tumor-to-normal cell SN-38, resulting in stabilized TOP1CCs, enhanced DNA damage and increased cytotoxicity with the combination, selectively in tumor cells but not normal cells, despite temporal separation of SG and PARPi exposure. To validate the hypothesis, we conducted a phase 1b investigator-initiated clinical trial combining SG with PARPi (talazoparib) in patients with mTNBC (NCT04039230). Inclusion criteria included female patients ≥ 18 years of age with mTNBC (per ASCO/CAP guidelines) and previous treatment with at least one prior therapeutic regimen for mTNBC. Clinical outcomes were assessed by Objective Response Rate per RECIST v1.1. In the phase 1b clinical trial (SG day 18, every 21 days with talazoparib), the staggered schedule with supportive therapy was relatively well-tolerated without DLTs, as predicted by the pre-clinical models. Furthermore, the staggered schedule demonstrated promising clinical activity. Molecular analysis of paired pre-treatment and on-treatment specimens demonstrated γ-H2AX accumulation, confirming pharmacodynamic inhibition with combination therapy. The dose-escalation portion of clinical trial successfully completed enrollment with a recommended phase-2 dose (R2PD) of sequential SG (10 mg/kg on days 1,8) with talazoparib (1 mg on days 15-21), every 21 days.

Conclusion: Staggered dosing of SG and PARPi, leveraging the selective drug delivery mechanism of SG to minimize toxicity while maintaining efficacy, was feasible and demonstrated encouraging evidence of clinical activity with objective responses among patients with mTNBC. The translational study highlights how mechanistic insights and innovative scheduling could be utilized to develop promising drug combinations, including previously rejected combinations, for patients with mTNBC.

Citation Format: Aditya Bardia, James T. Coates, Laura Spring, Sheng Sun, Dejan Juric, Nayana Thimmiah, Andrzej Niemierko, Phoebe Ryan, Ann Partridge, Jeffrey Peppercorn, Heather Parsons, Seth Wander, Kelsey Pierce, Victoria Attaya, Donna Fitzgerald, Brenda Lormil, Maria Shellock, Aiko Nagayama, Veerle Bossuyt, Bev Moy, Sara Tolaney, Leif Ellisen. Sacituzumab Govitecan, combination with PARP inhibitor, Talazoparib, in metastatic triple-negative breast cancer (TNBC): Translational investigation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2638.

Abstract 1789: Chromatin modifier alterations confer resistance to endocrine deprivation and CDK4/6 inhibitors in ER+ breast cancer and drive convergent evolution in patient autopsy lesions

We studied resistance mechanisms to hormone therapy and CDK4/6 cell cycle inhibitors in ER+ breast cancer by analyzing whole-exome, whole-genome, single-cell, and bulk transcriptomes in 120 autopsy samples from 13 patients obtained by the Massachusetts General Hospital Rapid Autopsy program. For each patient, we inferred the clonal structure of the samples and tracked the metastatic spread of different clones throughout the body. For 7 patients, we also analyzed serial cfDNA samples to identify clones that were selected for during treatment. We identified significantly recurrent and convergent (arising independently in distinct clones) acquired mutations in ESR1, KRAS, and chromatin modifier genes, in particular, mutations in KMT2C, which may represent mechanisms of drug resistance in this clinical setting. To experimentally study the role of KMT2C mutations, we used CRISPR/Cas9 to knock out KMT2C in the ER+ CAMA1 breast cancer cell line that is sensitive to both ER and CDK4/6 inhibition. KMT2C knock-out cells demonstrated significantly increased viability under treatment with fulvestrant (ERi), palbociclib (CDK4/6i), or their combination compared to the control cell lines. We show that this increased drug resistance is driven by downregulation of the ESR1 pathway, suggesting a decreased dependency on ER signaling for cell cycle progression. In addition to the early survival benefit, KMT2C knock-out resulted in a dramatic outgrowth of cells under long-term fulvestrant treatment. The KMT2C KO fulvestrant-resistant outgrown cells were highly resistant to the CDK4/6 inhibitors palbociclib, ribociclib, and abemaciclib compared to control cells, as well as to novel ERalpha inhibitors and a range of targeted therapies currently in clinical trials. By testing a panel of compounds on KMT2C KO and control cell lines, we propose potential novel therapeutic strategies that may help overcome the development of resistance in KMT2C-mutant cells. These findings suggest that KMT2C mutations may be a mechanism of acquired resistance to CDK4/6 inhibitor combinations, and subsequent treatment with therapies directed towards ER or CDK4/6 pathways may be ineffective and other treatment avenues need to be developed.

Citation Format: Elizaveta Leshchiner, Ignaty Leshchiner, Elizabeth E. Martin, Christopher T. Chen, Thomas Zhang, Christopher Pinto, Kahn Rhrissorrakrai, Filippo Utro, Chaya Levovitz, Raquel A. Jacobs, Brian P. Danysh, Kara Slowik, Maida Broudo, Laxmi Parida, Dejan Juric, Gad Getz. Chromatin modifier alterations confer resistance to endocrine deprivation and CDK4/6 inhibitors in ER+ breast cancer and drive convergent evolution in patient autopsy lesions [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1789.

Long-term safety of inavolisib (GDC-0077) in an ongoing phase 1/1b study evaluating monotherapy and in combination (combo) with palbociclib and/or endocrine therapy in patients (pts) with PIK3CA-mutated, hormone receptor-positive/HER2-negative (HR+/HER2-) metastatic breast cancer (BC)

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Background: Dysregulating mutations in PIK3CA, encoding the PI3K p110α subunit, occur in ̃40% of HR+/HER2– BCs. Inavolisib is a PI3Kα-specific inhibitor that also promotes degradation of mutant p110α. It has demonstrated encouraging preliminary antitumor activity in pts with PIK3CA-mutated HR+ BC as a monotherapy, and in combo with other anticancer agents. Methods: We included pts from NCT03006172 on treatment ≥1 year with inavolisib alone (Arm A), or in combo with palbo + letrozole (letro) (B), letro (C), fulvestrant (fulv) (D), or palbo + fulv (E; + metformin in Arm F for pts with body mass index ≥30 and/or HbA1c ≥5.7%). Inavolisib was administered orally daily (PO QD) at 3, 6, 9, or 12 mg (3+3 dose-escalation design); letro at 2.5 mg PO QD; palbo at 125 mg PO QD for 21/28 days; and fulv at 500 mg intramuscularly every 4 weeks, in 28-day cycles until intolerable toxicity/disease progression. Safety was assessed by NCI-CTCAE v4. Results: 57 female pts were included (cutoff 07/26/21; N = 1, 18, 6, 12, 15, 5 in Arms A–F); median age: 57 years (range 33–80); median lines of prior therapy: 2 (1–7). All but 2 pts, both in Arm B (3 mg), were assigned the 9 mg inavolisib recommended phase 3 dose. Overall median treatment duration: 19 months (range 12–45); median inavolisib cumulative dose intensity, 95%. The most frequent treatment-related adverse events (AEs; in ≥20 pts/35%) were hyperglycemia (68%), stomatitis (68%; grouped terms), neutropenia (58%), diarrhea (51%), nausea (39%), alopecia (35%), and rash (35%; grouped terms). The most frequent treatment-related Grade (G) 3–4 AEs (≥2 pts/4%) were neutropenia (47%), hyperglycemia (16%), leukopenia (9%), thrombocytopenia (9%), lymphopenia (7%), weight decreased, and hypokalemia (4% each). G3–4 neutropenia, leukopenia, thrombocytopenia, and lymphopenia were all reported in palbo arms. One G5 AE of pleural effusion was reported (disease progression-related). 39 pts (68%) had ≥1 AE resulting in study treatment modification (drug interruption/dose reduction/treatment withdrawal); 11 (19%) had an inavolisib dose reduction and 2 (4%) discontinued treatment due to an AE (1 related G2 diarrhea, 1 unrelated G3 cerebrovascular disorder). AEs typically occurred during the first 6 months and tended to be less frequent in later cycles. No new safety signals were observed with long-term inavolisib use. Conclusions: These data indicate acceptable long-term tolerability. The safety profile of pts on study treatment with inavolisib alone or in combo with endocrine-based anticancer therapies for ≥1 year was similar to that reported for the overall study population. Updated data will be presented. A phase 3 study of inavolisib + palbo + fulv is enrolling (NCT04191499; INAVO120). Clinical trial information: NCT03006172.

Single-cell profiling of human heart and blood in immune checkpoint inhibitor-associated myocarditis

2507

Background: Myocarditis due to immune checkpoint inhibitors (ICIs) is uncommon; however, myocarditis due to ICIs leads to severe morbidity and even death in 20-40% of cases. The molecular underpinnings of ICI-associated myocarditis are poorly understood, and there is an unmet clinical need to identify therapeutic targets and biomarkers that can aid in disease management. Methods: Heart tissue was obtained through endomyocardial biopsy or autopsy of patients receiving ICIs and was profiled with paired single-cell RNA sequencing (scRNA-seq) and T cell receptor sequencing (TCR) using the 10x Genomics Chromium system. A control dataset was constructed using scRNAseq data of heart tissue from patients receiving ICIs but without myocarditis and a published dataset from healthy patients not receiving ICIs. Peripheral blood mononuclear cells (PBMCs) were collected at the time of myocarditis diagnosis in a larger cohort of patients and analyzed with ICI-treated controls. The CITE-Seq protocol was used to measure paired scRNA-seq, TCR, and surface proteomics in PBMCs, using serial timepoints where available. Results: Heart tissue from 13 patients with myocarditis, including three fatal cases, and seven controls yielded 77,712 single cells. Blood profiling from 27 patients with ICI myocarditis and ICI-treated controls across 54 samples yielded over 230,000 cells. ICI myocarditis tissue demonstrated an increased T cell infiltrate (OR 8.94, FDR = 0.0021). Expression of multiple inflammatory pathways, most notably interferon responses, was up-regulated across multiple immune and non-immune cell types in the setting of myocarditis, providing important pathophysiological insights. T cell clones were also found to be shared between blood and heart, enabling the identification of putative pathogenic T cell subsets. Conclusions: Increased intramyocardial T cells and the activation of interferon response gene networks were seen in the setting of ICI myocarditis. These preliminary findings highlight potential pathological pathways in ICI myocarditis that could serve as biomarkers or therapeutic targets.

Phase 1 results of a phase 1/2 trial of CYT-0851, a first-in-class inhibitor of RAD51-mediated homologous recombination, in patients with advanced solid and hematologic cancers

3084

Background: Homologous recombination (HR) is an essential, high-fidelity mechanism to repair DNA double strand breaks (DSBs) in cancer cells. CYT-0851 inhibits HR leading to an accumulation of unrepaired DSBs and tumor cell death. We are reporting the completed Phase 1 dose-escalation results and RP2D selection to support ongoing development of CYT-0851. Methods: Patients (pts) with advanced hematologic and solid tumors were treated with continuous 28-day cycles of increasing doses of CYT-0851 following a 3+3 design. The primary objective was determining the maximum tolerated dose. Secondary objectives included safety, pharmacokinetics, and anti-tumor activity. Results: As of a 15 Nov 2021 data cutoff (DCO), 73 pts with advanced cancers (NHL n = 18; Sarcoma n = 16; Pancreas n = 11; Breast n = 8; HNSCC n = 6; Ovarian n = 4; SCLC n = 4; Other n = 4; Myeloma n = 2) were treated in 12 cohorts (total daily doses: 30 mg to 1200 mg). One pt experienced a dose-limiting toxicity (DLT) of reversible metabolic acidosis at 1200 mg. Two of 3 pts at 800 mg experienced reversible DLT-like events in Cycle 2 of Gr3 dry skin and Gr3 myalgia and polyarthritis, respectively. Three of 10 pts treated at 600 mg experienced DLT-like events in Cycle 1: 1 pt experienced an SAE of Gr3 anorexia with Gr3 stomatitis, vomiting, and dehydration and 2 pts had Gr3 fatigue. No DLTs occurred at 400 mg daily which was selected as the RP2D. 42 pts (57.5%) experienced a CYT-0851-related adverse event (AE), including 12 (16.4%) with a Gr3/4 AE. There were no treatment-related deaths. AE leading to CYT-0851 withdrawal were reported in 2 pts (2.7%) treated with 600 and 800 mg. The most common CYT-0851-related AEs were primarily Gr1/2 and included fatigue (20.5%), hyperuricemia (11%), nausea (11%), alopecia (9.6%), constipation (8.2%) and headache (8.2%). CYT-0851 exposure was approximately dose-proportional across the evaluated doses with an effective half-life of ̃3 days. Exposure at 400 mg daily was consistent with efficacy in preclinical models. 46 pts were evaluable for response at the DCO. 12 pts with NHL were evaluable by Lugano and included 1 CR in FL and 1 PR in DLBCL treated for 393+ and 244 days respectively. 34 pts with solid tumors were evaluable by RECIST v1.1 with 1 PR in a pt with myxofibrosarcoma treated for 313 days and 16 pts with stable disease. Fifteen pts were treated for 100+ days and 5 for 180+ days. Conclusions: CYT-0851 has demonstrated promising and broad clinical activity in a Ph 1 population of pts with advanced cancers. The safety profile is favorable as characterized by events that were infrequent, primarily Gr1/2, and reversible. Six expansion cohorts (DLBCL, Follicular Lymphoma, Myeloma, Pancreatic, Ovarian and Sarcoma) are enrolling to characterize activity at the RP2D. Ph 1 evaluation of CYT-0851 in combination with 3 chemotherapy backbones is also ongoing. Clinical trial information: NCT03997968.

Alpelisib (ALP) + fulvestrant (FUL) in patients (pts) with hormone receptor–positive (HR+), human epidermal growth factor receptor 2–negative (HER2−) advanced breast cancer (ABC): Biomarker (BM) analyses by next-generation sequencing (NGS) from the SOLAR-1 study

1006

Background: PIK3CA mutations (mut; ~40% of HR+, HER2– ABC) are linked to poor prognosis. In SOLAR-1, ALP (PI3Kα-selective inhibitor and degrader) + FUL improved progression-free survival (PFS) vs placebo (PBO) + FUL in pts with PIK3CA-mutated HR+, HER2– ABC. Here, we focus on efficacy data by gene alterations in SOLAR-1 PIK3CA-altered (alt) cohort. Methods: SOLAR-1 was a phase 3, randomized, double-blind study of ALP (or PBO) + FUL in HR+, HER2– ABC progressing on/after an aromatase inhibitor. Baseline tissue samples with enough quantity/quality (N = 398) were retrospectively tested by NGS (FoundationOne CDx 324-gene panel) and pts grouped by PIK3CA-alteration status. Clinical benefit was assessed using PFS and hazard ratio (HR) based on tumor mutational burden (TMB) and gene alteration status in the PIK3CA-alt cohort. No multiplicity adjustment was made. Results: PIK3CA-alt (ALP, n = 120; PBO, n = 117) and PI3KCA-non-alt (ALP, n = 81; PBO, n = 80) cohorts had differential gene alteration landscapes. In the PIK3CA-alt cohort, ALP + FUL clinical benefit was seen across TMB quartiles (Q1: 0 -<2.52, Q2: 2.52 -<3.78, Q3: 3.78 -<5.04, Q4: ≥ 5.04 mut/megabase). ALP + FUL had greater benefit in pts with alt vs non-alt FGFR1/ 2 (Table). ALP + FUL benefit was independent of alterations in TP53, ESR1, CCND1, MAP3K1, and ARID1A and limited in MYC- and RAD21-alt cohorts . ALP + FUL benefit was seen in pts with alt genes in the MAPK (HR [95% CI] vs PBO: alt 0.43 [0.23 - 0.80]; non-alt 0.56 [0.40 - 0.79]) and PI3K (in addition to PIK3CA; alt 0.68 [0.38 - 1.23]; non-alt 0.48 [0.34 - 0.68]) pathways, and implicated in CDK4/6i resistance (alt 0.52 [0.30 - 0.89]; non-alt 0.53 [0.37 - 0.76]). Conclusions: The unique mut profile of PIK3CA-alt tumors did not affect ALP + FUL benefit in pts with HR+, HER2– ABC. Clinical benefit was maintained regardless of alterations in most BMs, including ESR1 and genes implicated in CDK4/6i resistance, consistent with ALP targeting the PIK3CA driver oncogene. Clinical trial information: NCT#02437318; EUDRA CT#2015-000340-42. [Table: see text]

Relationship of travel distance with patient demographics, advance care planning, and survival in early-phase clinical trials (EP-CTs)

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Background: EP-CTs are often conducted at large academic centers, which may require some patients to travel further for their care. Little is known about either the distance EP-CT participants travel for their care or the association of distance traveled with patient characteristics and outcomes. Methods: We retrospectively reviewed the electronic health records of consecutive patients enrolled in EP-CTs at Massachusetts General Hospital from 2017-2019 to obtain patient characteristics (demographics and clinical factors) and outcomes (including time spent on trial, survival, and presence or absence of an advance care planning [ACP] discussion, defined as documentation of a code status or goals of care conversation in the medical record). We also used patients’ home zip codes to derive the social deprivation index (SDI; a composite demographic measurement from 0-100 quantifying social determinants of health, with higher numbers indicating more disadvantage). To estimate distance traveled, we calculated the miles traveled in one direction driving from home zip code to trial site. We used descriptive statistics to compare patient characteristics and outcomes for those traveling < 50 miles (short distance) versus those traveling 50+ miles (long distance). Results: Among 421 patients (median age = 63.0 years, 56.9% female, 97.6% metastatic disease), median distance traveled was 36.4 miles. Half of patients (n = 217; 51.5%) traveled 50+ miles to receive care on trial. There were no significant differences between those traveling short and long distances in most patient characteristics evaluated, including age (60.9 vs 60.6 years; p = 0.635), sex (53.9% female vs 57.6%; p = 0.447), race (85.3% white vs 84.8%; p = 0.346), marital status (71.8% married vs 69.3%; p = 0.586), insurance (51% private vs 54.4%; p = 0.266), cancer type (22.5% GI vs 21.2%; p = 0.666), prior lines of therapy (52.5% one-two lines vs 51.2%; p = 0.981), and performance status (62.3% ECOG 1 vs 66.8%; p = 0.270. However, those with a higher SDI score were less likely to travel a long distance for trial participation (mean SDI 36.7 for short distance vs 30.5 for long distance; p = 0.026). Patients traveling a long distance were less likely to have a documented ACP discussion (48.8% vs 66.7%; p < 0.001). We found no significant difference in time spent on trial between those traveling short and long distances (mean days: 98 vs 93.5; p = 0.175) or in time from coming off trial to death (mean days: 147.7 vs 153.7; p = 0.099). Conclusions: We found that half of EP-CT participants travel 50+ miles in one direction to their trial site, with disparities in travel distance based on the social deprivation index. Notably, those traveling long distances were less likely to have a documented ACP discussion. Our findings suggest several unmet needs in the EP-CT population and highlight opportunities for future intervention development.

Alpelisib (ALP) + endocrine therapy (ET) in patients (pts) with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2–), PIK3CA-mutated (mut) advanced breast cancer (ABC): Baseline biomarker analysis and progression-free survival (PFS) by duration of prior cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) therapy in the BYLieve study

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Background: ALP (PI3K-α selective inhibitor and degrader) + fulvestrant (FUL) is approved for pts with HR+, HER2– ABC and a tumor mutation in PIK3CA (̃ 40% of these pts). Primary analyses from the Phase 2 BYLieve study demonstrated efficacy and safety of ALP + ET in pts with PIK3CA-mut, HR+, HER2– ABC in the post-CDK4/6i setting. Post hoc analyses, including pts with disease progression within 6 mo of CDK4/6i + ET treatment (Tx), confirmed ALP benefit regardless of duration of prior CDK4/6i. Here we assess baseline biomarkers in circulating tumor DNA (ctDNA) by duration of prior CDK4/6i Tx and PFS in pts from BYLieve Cohorts A and B. Methods: In the BYLieve study, pts with PIK3CA-mut, HR+, HER2– ABC had CDK4/6i + aromatase inhibitor (Cohort A) or + FUL (Cohort B) as immediate prior Tx to receiving ALP + FUL and ALP + letrozole (LET), respectively. At data cutoff dates, pts had ≥ 18-mo follow-up in Cohort A and ≥ 6-mo in Cohort B. In each cohort, pts were grouped based on duration of prior CDK4/6i Tx (≤ 6 mo or >6 mo). Alterations were detected on ctDNA using next-generation sequencing (PanCancer V2 Panel). PFS was assessed in each cohort and by duration of prior CDK4/6i Tx. Results: Of 127 and 126 pts enrolled in Cohorts A and B, respectively, 98 (≤ 6-mo: 24; >6-mo: 74) and 94 (≤ 6-mo: 28; >6-mo: 66) were included in this analysis based on availability of ctDNA samples, data on duration of prior CDK4/6i, and centrally confirmed PIK3CA-mut disease. In this population, median (m) PFS (95% CI) was 8.2 mo (5.6 - 9.5) and 5.6 mo (3.7 - 7.1) in Cohorts A and B, respectively. In Cohort A, mPFS (95% CI) was 12.0 mo (5.5-non estimable) and 6.2 mo (5.4 - 8.5) in the ≤ 6-mo and >6-mo groups, respectively. The OncoPrint genomic profiles showed that pts in the ≤ 6-mo vs >6-mo group had a lower median ctDNA fraction and fewer detected gene alterations, including in genes associated with ET and/or CDK4/6i resistance, and fewer chromosomes 8/11 amplifications (linked to early relapse). In Cohort B, mPFS was 5.9 mo (3.5 - 11.0) and 5.6 mo (3.7 - 7.1) in the ≤ 6-mo and >6-mo groups, respectively. Both groups had high median ctDNA fractions and complex tumor mutation profiles reflecting more extensive treatment history. Conclusions: Lower median ctDNA fraction and lower mutational complexity observed in Cohort A ≤ 6-mo vs >6-mo group was associated with numerically longer mPFS, potentially indicating increased dependence on the mutant PI3K-α. In Cohort B, both ≤ 6-mo and >6-mo groups had high median ctDNA fractions and similar tumor mutation profiles. Additional ctDNA and tissue analyses are needed to elucidate the correlation between ALP + ET efficacy and treatment timing and baseline genomic complexity.

Protocol requirements and logistical intensity of early-phase clinical trials (EP-CTs)

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Background: EP-CTs are increasingly important options for patients with cancer and often involve intensive monitoring. Characterizing the time burden and logistical intensity of EP-CT protocols could help patients and clinicians make informed decisions about trial participation. Methods: We retrospectively reviewed the electronic health records of consecutive patients enrolled in EP-CTs at Massachusetts General Hospital from 2017-2019 to obtain baseline characteristics (demographics and clinical factors), EP-CT investigational agent (immunomodulatory [IM], targeted inhibitor [TI], antibody drug conjugate [ADC]/chemotherapy prodrug), and logistical intensity (visit frequency required per protocol and presence of extended visits). We defined visit frequency as the number of visits required per protocol within the first 28 days on trial. We defined an extended visit as six or more hours required in clinic on at least one day during the first 28 days on study. We evaluated associations among patient characteristics, investigational agents, logistical intensity, and time spent on trial. Results: Among 421 patients (median age = 63.0 years, 56.9% female, 97.6% metastatic disease), 43.2% were enrolled in IM EP-CTs, 43.0% TI, and 13.8% ADC/chemotherapy prodrug investigational agents. Patients enrolled on ADC/prodrug trials had the highest burden of metastatic disease (mean sites: 2.8 [ADC] vs 2.4 [TI] vs 2.3 [IM], p = 0.007) and oldest age (mean years: 64.0 [ADC] vs 61.7 [IM] vs 58.5 [TI], p = 0.003). However, those on ADC trials had the most days spent on trial (mean days: 78.3 [TI] vs 102.2 [IM] vs 131.8 [ADC], p = 0.003). Patients enrolled on TI trials had the highest required visit frequency compared with those enrolled on other trials (mean visits: 5.5 [TI] vs 5.3 [ADC] vs 5.0 [IM], p = 0.027). Additionally, those on TI trials were most likely to have an extended visit (82.3% [TI] vs 58.2% [IM] vs 29.3% [ADC], p < 0.001) and least likely to receive first in human therapy (38.1% [TI] vs 74.1% [ADC] vs 74.2% [IM], p < 0.001). Conclusions: In this cohort of patients participating in EP-CTs, we found that those enrolled on TI trials had the highest per protocol visit frequency and greatest likelihood of required extended visits. Those on ADC trials spent the most days on trial despite having the highest average age and burden of metastatic disease. These data highlight the time burden and logistical intensity of EP-CTs, underscoring certain trials as especially time intensive, which may help inform trial selection and participation.

Utilizing Natural Language Processing (NLP) to identify breast cancer associated-lung metastases from pathology reports to delineate characteristics and challenges of this common site of breast cancer recurrence

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Background: NLP (artificial intelligence) can automate the identification of records in large datasets. The purpose of this study was to evaluate the feasibility of NLP to identify breast cancer-associated lung metastases to understand clinical characteristics and challenges posed by this common site of breast cancer recurrence. Methods: Patients with pathologically confirmed breast cancer associated-lung metastases seen at a large academic center between 3/2012-5/2019 were identified using NLP of institutional pathology reports, with an IRB approved protocol. Chart review was performed to confirm breast cancer associated-lung metastases and determine clinical and pathological features. Results: Using NLP, 32 patients with pathology reports denoting breast cancer associated-lung metastases were identified, with pathologic confirmation of lung biopsy tissue in the majority of cases (24), and pleural fluid specimens (8) on the remainder. Ten of 32 (31%) were HR+/HER2-, 3/32 (9.3%) HER2+, and 19/32 (59%) TNBC. The majority were invasive ductal carcinoma (21/26) with the remainder invasive lobular carcinoma (2/26) or mixed histology (3/26). Median age at lung metastasis diagnosis was 62 years (range 31-88). The median time to development of lung metastasis following primary breast cancer was 5.6 years (range 0-24.8 years). Fifty six percent of lung metastases were detected on imaging and 44% by symptoms including dyspnea, cough, or pain. Tumor tissue genotyping results on the lung metastases were available for 8 patients showing PI3KCA (5), TP53 (3), SMARCA4 (2), ERBB2 (1), FGFR3 (1), ATM (1), CDK4 (1), MYC (1), and ESR1 (1). Treatment after diagnosis of lung metastases included hormone therapy (61%), chemotherapy (84%), lung irradiation (26%), and surgical resection of lung metastases (6%). Lung metastases were associated with considerable morbidity including pleural effusion (15%), dyspnea (6%), pneumothorax (3%), hemothorax (3%), and atelectasis (3%). Patients diagnosed with lung metastases had brain (32%), bone (35%), renal (6%), skin (3%) and adrenal (3%) metastases during disease course. Conclusions: NLP can help identify organ specific metastases from pathology reports, such as breast cancer associated-lung metastases, which can then facilitate observational, translational, and clinical research to characterize and address challenges posed by this common site of breast cancer recurrence. This cohort of patients highlights the morbidity of breast cancer associated-lung metastases and potential role of NLP for disease characterization and clinical research. (Support from ASCO Medical Student Rotation for Underrepresented Populations Award.)

Trial in progress: Phase I study of SY-5609, a potent, selective CDK7 inhibitor, with initial expansion in adults with metastatic pancreatic cancer

TPS4180

Background: SY-5609 is an oral, selective, potent CDK7 inhibitor that targets two fundamental processes in cancer: transcription and cell cycle control. Early results from the Phase 1 dose escalation portion in patients (pts) with advanced solid tumors reported improved tolerability of the intermittent 7 days on followed by 7 days off (7/7) schedule with ongoing dose escalation beyond the continuous daily dosing maximum tolerated dose. Single-agent clinical activity was demonstrated with durable stable disease, target lesion regressions, and reduction in tumor markers observed in multiple tumor types, notably in pancreatic cancer with a disease control rate (DCR) of 38.5% (Sharma 2021). Pancreatic ductal adenocarcinoma (PDAC) has a 5-year survival rate of 11% (ACS Cancer Facts and figures, 2022) with limited treatment options and therefore, is a disease in need of novel effective therapies. Oncogenic KRAS mutations are prevalent in PDAC. Mutant KRAS is a potent stimulator of mitogenic MAPK signaling and downstream transcriptional programs for cell proliferation. Preclinical studies have shown that CDK7 inhibition via SY-5609 inhibits tumor growth in KRAS mutant PDAC xenograft models, in many cases leading to regressions. SY-5609 also potentiates gemcitabine (gem) activity in PDAC cells in vitro and in xenografts in vivo (Henry 2021). Therefore, combining SY-5609 with gem +/- nab-paclitaxel (nab-pac) offers a potential new treatment strategy for metastatic PDAC (mPDAC). The expansion portion of this Phase 1 study will evaluate SY-5609 in combination with gem +/- nab-pac in mPDAC pts. Gem +/- nab-pac will be administered on a biweekly schedule as it has shown better tolerability and similar clinical activity compared to the standard of care (SOC) administration schedule (Rehman 2020). Methods: This is an ongoing Phase 1, multi-center study in select solid tumors, amended to open expansion cohorts for mPDAC and expected to enroll approximately 80 mPDAC pts who have progressed on SOC treatments. Objectives of the expansion cohorts include evaluation of safety and efficacy of SY-5609 in combination with gem +/- nab-pac. Key objectives of the two parallel safety lead-in cohorts 1) SY-5609 + gem and 2) SY-5609 + gem + nab-pac are safety and determination of the recommended combination dose of the doublet and triplet for subsequent cohort expansions using a 3+3 escalation design. Key objectives of expansion cohorts are to describe efficacy, defined by progression-free survival, overall response rate, and DCR. Additional objectives include evaluation of pharmacokinetics and pharmacodynamics of SY-5609 in combination with gem +/- nab-pac. SY-5609 will be administered orally once daily on a 7/7 regimen and gem +/- nab-pac will be administered intravenously, in a 4-week cycle. The expansion portion is now open to enrollment. Clinical trial information: NCT04247126.