Clinical Outcomes for Patients With Metastatic Breast Cancer Treated With Immunotherapy Agents in Phase I Clinical Trials.

Background: Immuno-oncology (IO) agents have demonstrated exceptional clinical benefit in patients with many tumor types, including melanoma and lung cancer. The PD-L1 inhibitor, atezolizumab, was recently FDA approved in combination with nab-paclitaxel for patients with PD-L1 positive triple-negative breast cancer (TNBC); however, single-agent PD-1/PD-L1 inhibitors demonstrate modest efficacy in breast cancer. The purpose of this study was to investigate the efficacy of IO agents in patients with metastatic breast cancer treated in phase I clinical trials. Methods: We performed a retrospective analysis using a database of patients with metastatic breast cancer who received treatment with IO agents in phase I/Ib clinical trials at the University of Colorado Anschutz Medical Campus from January 1, 2012 to July 1, 2018. Abstracted data included patient demographics, baseline characteristics, and clinical outcomes. Results: 208 patients with metastatic breast cancer were treated in phase I/Ib clinical trials; 43 were treated with an IO agent. The average age was 53 years old and 55.8% had hormone receptor-positive/HER2-negative breast cancer, 39.5% TNBC, and 4.6% HER2-positive disease. On average, patients received two prior lines of chemotherapy (range 0-7) in the metastatic setting. 31/43 patients (72.1%) received single agent or combination IO, and 12/43 (27.9%) received IO + chemotherapy. Median progression-free survival (PFS) was 2.3 months and median overall survival (OS) was 12.1 months in all patients. 9/43 (21%) of patients remained on study > 6 months and had a median PFS of 8.6 months. Patients remaining on study > 6 months were more likely to be treated with IO + chemotherapy compared to patients with a PFS < 6 months (77.8% v. 14.7%, p=0.0007). There was no difference in sites of metastasis, prior lines of chemotherapy, breast cancer subtype, absolute lymphocyte count, or LDH between patients with a PFS > 6 months compared to < 6 months. Conclusions: A subset of patients with metastatic breast cancer treated in phase I clinical trials at our center with an IO agent had derived prolonged clinical benefit. The benefit was not limited to patients with TNBC and was associated with receipt of chemotherapy in combination with IO. Predictors of response to immunotherapy in breast cancer beyond PD-L1 expression remain uncharacterized, and further research is needed to identify these factors. Citation Format: Jodi A. Kagihara, Jennifer A. Weiss, Andrew Nicklawsky, Dexiang Gao, Virginia F. Borges, Peter Kabos, Antonio Jimeno, Jennifer R. Diamond. Efficacy of immunotherapy agents in patients with metastatic breast cancer treated in phase I clinical trials [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr A76.

Recent and emerging data have generated great excitement about manipulating the patient’s own immune system to attack and eliminate malignant tumors. Although the majority of success has not been in breast cancer, recent studies have increased enthusiasm about this therapeutic modality. The immune system plays a complex role in cancer biology involving both in promotion and eradication of disease. A series of immune checkpoints are hardwired into the immune system in order to modulate the duration and amplitude of the immune response, reducing collateral normal tissue damage. These immune checkpoint pathways serve as a mechanism for tumor immune invasion, particularly against T-cells generated against tumor antigens. Recently several monoclonal antibodies specifically targeted at blocking immune checkpoint receptor-ligand interactions have demonstrated unprecedented anti-tumor responses in a wide variety of immunogenic tumors that has led to U.S. FDA approval of a variety of agents, including those blocking the programmed cell death protein 1 (PD1) receptor and its ligand programmed cell death-ligand 1 (PD-L1). Unlike many solid tumors, breast cancer has not typically been responsive to modulation of the immune system. The success of checkpoint inhibitors to date has generally relied on the immunogenicity and high mutational burden which is thought to be important in generating an antitumor immune response to neoantigens that can then be reactivated by immune checkpoint inhibitors. In breast cancer, proliferative subsets such as TNBC and HER2+ disease have a higher mutational burden, and could be more amenable to immunotherapy. Higher levels of tumor infiltrating lymphocytes (TILs) are found in TNBC and HER2 positive breast cancer and have been associated with improved outcome in both early and late stage disease settings. Expression of PD-L1 has been shown to be associated with lack of ER expression, higher TIL counts and the triple negative phenotype. Chemotherapy may increase mutational burden or expression of neoantigens through cell death, potentially increasing tumor immunogenicity and making combination studies very appealing. Four phase I monotherapy expansion trials in patients with metastatic breast cancer have demonstrated low but durable single agent responses to PD-1 and PD-L1 inhibitors, ranging from 4.8 to 19%. Two trials included patients with TNBC, one trial included patients with any breast cancer subtype, and one trial included only patients with HR+ disease. Higher response rates are seen in TNBC, compared to hormone receptor positive disease. Variability in requirements for tumor PD-L1 expression, and variations in testing complicate cross trial comparisons. Two large single agent trials enrolling over 100 patients have recently been presented evaluating either atezolizumab or pembrolizumab as single agent therapy for TNBC. Response rates ranged from 5 to 10%, but in both trials the response rate was much higher in patients treated in the first line setting at 23-26%, potentially due to multiple mechanisms of resistance in the second or greater line setting and bringing up the question of clinical trial design. Although rare durable responses have been seen, it is clear that combination therapy is a critical next step in the study of immunotherapy for breast cancer. Both pre-clinical and clinical data suggest that chemotherapy can enhance the host immune response, acting as an ‘immune agonist.’ A 5th phase Ib trial reported a 38% response rate in metastatic TNBC treated with atezolizumab and nab-paclitaxel in combination. Several phase III trials combining immune checkpoint inhibitors with chemotherapy as first line therapy for metastatic TNBC are ongoing, as well as a number of adjuvant and post-neoadjuvant trials. One small trial suggested that response to checkpoint inhibition might be improved with induction therapy with either a short course of radiation or chemotherapy. Additional studies are evaluating combinations with immune agonists. Given data suggesting improved response in less heavily pretreated disease, there has been great interest in combining immune check-point inhibition with chemotherapy as neoadjuvant therapy for high risk breast cancer. Recent data from the multi-arm I-SPY2 phase II neoadjuvant trial demonstrated a marked and significant improvement in estimated pathologic complete remission when pembrolizumab was added to weekly paclitaxel before anthracyclines in both triple negative and hormone receptor positive disease. Longer exposure to pembrolizumab is currently being evaluated. Several randomized trials in the neoadjuvant setting are planned or ongoing as well. Treatment with checkpoint inhibitors is generally well tolerated, with low rates of immune toxicity including hypothyroidism, pneumonitis, hepatitis, colitis, and hypophysitis, occurring even months after the end of therapy. In the neoadjuvant I-SPY2 trial, higher rates of adrenal insufficiency were noted, although these responded quickly to treatment. Further evaluation is needed to understand this difference. Ongoing studies are evaluating combinations with chemotherapy, as well as a number of other targeted agents such as immune agonists, MEK inhibitors, HDAC inhibitors, HER2 targeted therapy and cyclin dependent kinase 4/6 inhibitors. 1.Mittendorf EA, Philips AV, Meric-Bernstam F, et al. PD-L1 Expression in Triple-Negative Breast Cancer. Cancer Immunol Res. 2014;2;361. 2.Chen G, Emens LA. Chemoimmunotherapy: reengineering tumor immunity. Cancer Immunol Immunother. 2013;62(2):203-216. 3.Nanda R, Chow LQ, Dees EC, et al. Pembrolizumab in Patients With Advanced Triple-Negative Breast Cancer: Phase Ib KEYNOTE-012 Study. J Clin Oncol. 2016;34(21):2460-2467. 4.Dirix LY, Takacs I, Nikolinakos P, et al. Avelumab (MSB0010718C), an anti-PD-L1 antibody, in patients with locally advanced or metastatic breast cancer: A phase Ib JAVELIN solid tumor trial. SABCS. 2015. 5.Rugo HS, Delord JP, Im SA, et al. Preliminary efficacy and safety of pembrolizumab (MK-3475) in patients with PD-L1–positive, estrogen receptor-positive (ER+)/HER2-negative advanced breast cancer enrolled in KEYNOTE-028. Cancer Res 2016;76 (4 suppl):abstr S5-07. 6.Emens LA, Braiteh FS, Cassier P, et al. Inhibition of PD-L1 by MPDL3280A leads to clinical activity in patients with metastatic triple-negative breast cancer. SABCS. 2014:PD1-6. 7.Schmid P, Cruz C, Braiteh FS, et al. Atezolizumab in metastatic TNBC (mTNBC): Long-term clinical outcomes and biomarker analyses. Proc AACR 2017:Abst. 2. 8.Adams S, Schmid P, Rugo HS, et al. Phase 2 study of pembrolizumab (pembro) monotherapy for previously treated metastatic triple-negative breast cancer (mTNBC): KEYNOTE-086 cohort A. JCO. 2017;35, (no. 15_suppl):1008. 9.Adams S, Diamond JR, Hamilton EP, et al. Phase Ib trial of atezolizumab in combination with nab-paclitaxel in patients with metastatic triple-negative breast cancer (mTNBC). JCO. 2016;34, (no. 15_suppl):1009. 10.Nanda R, Liu MC, Yau C, et al. Pembrolizumab plus standard neoadjuvant therapy for high-risk breast cancer (BC): Results from I-SPY 2. J Clin Oncol 2017;35: abstr 506. Citation Format: Hope S. Rugo. Setting the stage for immunotherapy in breast cancer: where are we and where are we going in the clinic? [abstract]. In: Proceedings of the AACR Special Conference: Advances in Breast Cancer Research; 2017 Oct 7-10; Hollywood, CA. Philadelphia (PA): AACR; Mol Cancer Res 2018;16(8_Suppl):Abstract nr IA24.

Background: Triple-negative breast cancer (TNBC) comprises a heterogeneous group of diseases which are generally associated with poor prognosis. In recent years, major progress has been made in the treatment of metastatic breast cancer (MBC), especially for hormone receptor (HR) positive and HER2 positive MBC. In contrast, for most TNBC patients no targeted treatment options are available. Population-based data on overall survival (OS) of triple negative MBC are scarce and were totally missing for the Austrian population. Here, we present the overall survival (OS) results of triple-negative breast cancer patients included the MBC registry of the Austrian Study Group for Medical Tumor Therapy (AGMT). Patients and methods: The AGMT_MBC-Registry is a multicenter nationwide ongoing retrospective and prospective registry for MBC patients in Austria. Unadjusted, univariate survival probabilities of OS were calculated by the Kaplan-Meier method and multivariate hazard ratios (HR) were estimated by Cox regression models. In this analysis only patients with triple-negative MBC with available survival data were included. Results: As of 31/01/2019, 1,253 patients were included in the AGMT-MBC-Registry. Out of 1,219 evaluable patients with available survival data, 192 (17.8%) were triple-negative. Mean age at diagnosis of MBC was 59 (range 27-89), 44 patients (22.9%) were diagnosed with de novometastatic disease, 89 patients (46.4%) with metachronous MBC had a disease free survival (DFS) < 24 months, 134 (69.8%) were treated with (neo)adjuvant therapy, 114 (59.4%) had visceral disease at diagnosis of MBC, and number of involved metastatic sites at diagnosis was 1 in 102 (53.1%), 2 in 49 (25.5%), 3 in 24 (12.5%) and > 3 sites in 17 (8.9%) patients. Fifty-nine patients (49.5%) received at least one treatment-line which included bevacizumab. Bevacizuamb was combined with capecitabine, paclitaxel and gemcitabine in 38, 68 and 5 patients, respectively. Median OS of TNBC was 15.2 months (95% CI 11.4-18.9), compared to 32.9 months (95% CI 29.7-35.7) in the overall cohort. In multivariate analysis including established risk factors and clinically relevant variables, only three variables were significantly associated with OS in TNBC patients: disease free survival (<24 months vs ≥ 24 months or de novo MBC: HR 1.80 [95% CI 1.29-2.51]), visceral disease (yes vs no: HR 1.75 [95% CI 1.22-2.52]), and number of metastatic sites at initial diagnosis (2-3 vs 1: HR 1.81 [95% CI 1.26-2.60], > 3 vs 1: HR 3.05 [95% CI 1.66-5.61]). Conclusion: The poor prognosis of TNBC was confirmed in this population-based analysis. Besides known prognostic factors like de novo metastatic disease, DFS and visceral disease, the number of metastatic sites at initial diagnosis was identified as a novel independent prognostic factor in TNBC. Citation Format: Gabriel Rinnerthaler, Simon P Gampenrieder, Andreas Petzer, Christoph Tinchon, David Fuchs, Marija Balic, Sonja Heibl, Holger Rumpold, Daniel Egle, August F Zabernigg, Christian F Singer, Johannes Andel, Michael Hubalek, Michael Knauer, Richard Greil. Prognosis of triple negative metastatic breast cancer (MBC): Results from the AGMT_MBC-Registry [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-06-29.

Introduction: Sacituzumab govitecan (SG) is FDA-approved for the treatment of both metastatic triple negative breast cancer (mTNBC) and hormone receptor positive (HR+)/HER2- metastatic breast cancer (MBC). In phase III clinical trials, SG caused grade 3 neutropenia in ∼50% of patients. However, the real-world incidence of SG-induced neutropenia and the practice patterns regarding the use of adjuvant growth factor use are not well characterized. Methods: In this single retrospective cohort study, we identified patients with HR+/HER2- or TNBC MBC who received SG between 2020-2024 per standard of care. We used manual review of electronic health records to identify key clinical characteristics, treatment history, safety parameters, and documented use of growth factor support via granulocyte colony stimulating factor (GCSF, either filgrastim or pegfilgrastim) while on treatment with SG. Results: We identified 74 patients with MBC who were treated with SG, including 45 patients with mTNBC (60.8%), 27 patients with HR+/HER2- MBC (36.5%), and 2 patients with heterogenous expression who were categorized as HR+/HER2+ MBC (2.7%). Median age was 56.5 years (range 28.4 - 81.1 years). Patients with mTNBC received a median of 2 prior lines of chemotherapy (range 0-5) and patients with HR+/HER2- disease received a median of 8 lines of prior therapy including 4 prior lines of chemotherapy (range 2-14 total lines, 0-8 lines of chemotherapy). Median time on SG was 4.4 months (range 0.26-39.8 months) for patients with mTNBC and 1.9 months (range 0.26-15.6 months) for patients with HR+/HER2- MBC. Most patients experienced any grade neutropenia while on SG (n=60, 81.1%), including most patients with mTNBC (n=37, 82.2%) and HR+/HER2- MBC (n=21, 77.8%). Grade 3 neutropenia was common during SG (n=39, 52.7%), with similar rates among patients with mTNBC (n=25, 55.6%) and HR+/HER2- MBC (n=12, 44.4%). Rates of neutropenic fever were low: in total 5/74 (6.8%), of whom 4/45 (8.9%) were mTNBC. A total of 8/74 (10.8%) patients were hospitalized for SG-related neutropenia with median length of stay 3.5 (range 1-10) days. Dose delays for any reason occurred in patients with mTNBC (n=18, 40.0%) and HR+/HER2- MBC (n=8, 29.6%), about half of which were due to neutropenia (for mTNBC n=7, 15.6%, HR+/HER2- MBC n=4, 14.8%). Dose reductions for any reason were also common among patients with mTNBC (n=21, 46.7%) and HR+/HER2- MBC (n=18, 66.7%), including some due to neutropenia (for mTNBC n=7, 15.6%, for HR+/HER2- n=4, 14.8%). Most patients discontinued SG due to disease progression for both mTNBC (n=43, 95.6%) and HR+/HER2- MBC (n=24, 88.9%). Two patients with HR+/HER2- MBC (7.4%) discontinued therapy due to toxicity. The remaining patients are still on therapy or discontinued for unrelated reasons. Most patients received GCSF during treatment with SG (n=64, 86.5%), most of whom received filgrastim (n=62, 83.8%) and a minority of whom received peg-filgrastim (n=7, 9.5%). In total 34/74 (45.9%) patients received primary GCSF prophylaxis and 24/74 (32.4%) patients received secondary GCSF prophylaxis. Rates of primary and secondary prophylaxis varied by subtype for mTNBC and HR+/HER2- respectively (primary: 37.8% and 55.6%; secondary: 40.0% and 22.2% respectively). Conclusion: In this single center retrospective study, >80% patients with mTNBC and HR+/HER2- MBC on SG experienced any grade neutropenia. Similar to published trials, nearly half of patients in both subgroups experienced grade 3 neutropenia but rates of hospitalizations and neutropenic fever were <10% in this heavily pre-treated, real-world cohort. Rates of SG dose reduction occurred in ∼50% of patients, but rates of discontinuation due to toxicity were low. GCSF prophylaxis, either primary or secondary, was used in ∼80% of patients. Additional studies are needed to clarify which patients may be at highest risk for SG-induced neutropenia and the optimal growth factor regimens to improve outcomes. Citation Format: Samantha Fisch, Joshua Chin, Laura Quintal, Melanie Majure, Michelle Melisko, Jo Chien, Hope S. Rugo, Laura A. Huppert. Single-center retrospective cohort study evaluating neutropenia and growth factor use with sacituzumab govitecan in patients with HR+/HER2- and triple negative metastatic breast cancer [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P5-12-25.

: Triple negative breast cancer is an aggressive subtype of breast cancer that lacks expression of estrogen and progesterone receptors, and does not overexpress the human epithelial growth factor 2 receptor. Triple negative breast cancer occurs in approximately 20% of breast cancer cases, and patients are more likely to present with an advanced stage, have higher relapse rates, and have a worse prognosis than other breast cancer types. There are no targeted therapies for the majority of patients with triple negative breast cancer. The mainstay of treatment remains chemotherapy and the historical median overall survival for metastatic patients is around one year. Immunotherapy has dramatically improved outcomes in other malignancies by harnessing the body’s immune system to attack cancer cells. Triple negative breast cancer is the most immunogenic type of breast cancer, with a large genetic mutational burden and a relatively high number of immune cells found in the cancer microenvironment compared to other breast cancer subtypes. While initial studies of single agent immunotherapy in metastatic triple negative breast cancer were promising, the survival outcomes have been disappointing. Combining systemic therapy with immunotherapy has become a recent focus of clinical trials, and is now the current standard of care for treatment naive metastatic triple negative patients that are programmed death-ligand 1 positive. The efficacy of combined chemoimmunotherapy for first-line treatment has yet to be replicated, and recent clinical data questions the true benefit. This review summarizes the clinical trials of single agent and combination strategies for immunotherapy in metastatic triple negative breast cancer. We also examine the potential role for biomarkers, and future direction of treatment.

Background: Circulating Tumor cells (CTCs) are prognostic at baseline and first follow-up in patients with metastatic breast cancer (MBC). Using the most commonly used assay (CellSearch®), we have previously reported the ability to detect apoptotic vs. non-apoptotic CTCs in patients with MBC. However, there has been concern regarding the performance of the CellSearch® assay in patients with triple negative (TN) MBC. We hypothesized that CellSearch® is an effective assay in patients with TN MBC, and that CTC-apoptosis might further separate prognosis. Therefore, we studied CTCs in patients with TN MBC who participated in a prospective randomized phase II trial testing for activity of tigatuzumab (TIG) in combination with nanoparticle albumin-bound paclitaxel (nab-PAC) conducted by the Translational Breast Cancer Research Consortium (overall results reported by Forero A., et al, ASCO 2013). Methods: Whole blood (WB) was drawn into a CellSave tube at baseline, day 15, and day 29 and CTC counts were determined using the CXC CellSearch® kit. Apoptosis was characterized by staining with a monoclonal antibody that detects a neo-epitope on fragmented cytokeratin (M-30) and independently by visual inspection (nucleic condensation and/or fragmentation, as well as granular cytokeratin). Association between levels of CTCs and CTC-apoptosis with the overall response rate (ORR) and progression free survival (PFS) at baseline, day 15, and day 29 was assessed using logistic regression, Kaplan Meier curves, and Cox proportional hazards modeling. Results: Of the 60 patients entered into the trial, 52 were evaluable for CTCs. Of these, 19/52 (36.5%), 14/52 (26.9%), and 13/49 (26.5%) had elevated CTCs (≥5CTC/7.5 ml WB) at baseline, day 15, and day 29, respectively. Patients with elevated CTCs at each time point had worse PFS than patients with low or no CTCs. Hazard rates (HR) at baseline, day 15, and day 29 were 2.38 (95% CI: 1.27-4.45, p = 0.007), 2.87 (95% CI: 1.46-5.66, p = 0.002), and 3.40 (95% CI: 1.68-6.89, p = 0.001), respectively. The odds of overall response for those who had elevated CTCs compared to those who did not at baseline, day 15, and day 29, were 0.25 (95% CI: 0.073-0.81, p = 0.024), 0.18 (95% CI: 0.04-0.67, p = 0.014), and 0.06 (95% CI: 0.01-0.28, p = 0.001), respectively. There was no apparent prognostic effect comparing the degree of CTC-apoptosis vs. non-apoptosis. Conclusions: Similar to observations in other intrinsic subgroups, CTCs were detected in a large fraction of TN MBC patients at baseline using CellSearch® assay, and reductions in CTC levels reflected response. In these homogenously prospectively enrolled TN MBC patients, regardless of treatment, CTCs are prognostic at baseline, day 15, and day 29. It does not appear that analysis of CTC-apoptosis is prognostic. Supported by Susan G. Komen for the Cure, Veridex, LLC, Fashion Footwear Charitable Foundation of New York/QVC Presents Shoes on Sale™ (DFH), Associazione Sandro Pitigliani and by a studentship from FIRC (CP), Triple Negative Breast Cancer Foundation, The AVON Foundation, and The Breast Cancer Research Foundation. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-04-01.

Background: Advanced triple negative breast cancer (TNBC) has a poor prognosis, with a median survival of approximately 12 months. Due to a lack of receptor targets, chemotherapy remains the mainstay of treatment. A subset of TNBC has defects in homologous recombination (HR) DNA repair due to germline BRCA mutations. Poly(ADP-ribose) polymerase (PARP) inhibitors have been shown to be an effective therapy in this subgroup. The phosphoinositide-3-kinase (PI3K) pathway inhibitors are also active in some breast cancers, lowering nucleotide pools required for DNA synthesis and S-phase progression. Preclinical studies suggest that PI3K stabilizes and preserves double strand break repair by interacting with the HR complex. Inhibition of PI3K/mTOR could impede PI3K interaction with the HR complex, thereby increasing dependency on PARP enzymes for DNA repair, and making this dual inhibition a rational combination. This trial is studying the safety and efficacy of combining the PI3K/mTOR inhibitor, gedatolisib, and the PARP inhibitor, talazoparib. Single-agent talazoparib is currently approved in advanced HER2 negative breast cancer with a germline BRCA 1/2 mutation. Trial design: This trial is designed with a safety run-in to determine the recommended phase 2 doses (RP2D) of the talazoparib and gedatolisib combination. The safety run-in will be followed by a phase II single-arm study of the combination, with 2 patient cohorts. Cohort A will be comprised of patients with advanced TNBC with negative or unknown germline BRCA1/2 status. Cohort B will be used for an exploratory analysis, comprised of patients with advanced HER2 negative breast cancer and a germline BRCA1/2 mutation. Eligibility Criteria: For the safety run-in phase, patients ≥18 of age with advanced breast cancer (defined as metastatic or unresectable) are eligible if they meet criteria for either cohort A or cohort B. For cohort A, all patients are required to have at least one line of prior systemic therapy for advanced breast cancer but no more than 2 lines of prior chemotherapy are allowed. For cohort B, no more than 2 lines of prior chemotherapy are allowed, with no limit on prior endocrine or targeted therapies. Patients with type I or poorly controlled diabetes are excluded due to the common side effect of hyperglycemia with gedatolisib. Specific aims: Primary objective of the safety run-in: Determine the RP2D of talazoparib in combination with gedatolisib in patients with advanced HER2 negative (triple negative or BRCA1/2 deficient) breast cancer. Primary objective of the phase II study: Estimate the objective response rate (ORR) in patients with BRCA1/2 negative, or unknown, advanced TNBC - Cohort A. Correlative analysis will include correlating the HR deficiency (HRD) score with clinical response in patients with TNBC. Statistical Methods: In the safety run-in, a 3+3 design will be used for dose escalation. Maximum tolerated dose (MTD) is decided when 6 patients are treated at a dose level with < 2 DLTs. The MTD will be the RP2D. The safety run-in (dose escalation) component will require 9-18 subjects. In the Phase II study, the primary endpoint for sample size justification is ORR for cohort A (TNBC). The null response rate of 5% will be compared to the alternative hypothesis of 20% ORR with a 1-sided alpha level of 0.1. Based on the exact binomial test, we propose 21 subjects to target a power level of 80%. ORR in cohort B is a secondary endpoint. Target Accrual: Our target accrual for the safety run-in is 9-18 participants. Assuming 10% of subjects will be not be evaluable for the primary outcomes, then the number of patients accrued to cohort A will be 24. Cohort B will remain at 12 since it is exploratory. Contact information: The study is being administered through the Big Ten Cancer Research Consortium and can be identified as BTCRC-BRE18-337. Citation Format: Sneha Phadke, Menggang Yu, Kathy Miller, Ami Shah, Oana Danciu, Kari Wisinski. Phase 2 trial with safety-run in of gedatolisib plus talazoparib in advanced triple negative or BRCA1/2 positive HER2 negative breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr OT2-06-02.

Background 20-30% of breast cancer (BC) patients will develop distant metastases. Despite important improvement achieved in the management of metastatic BC (MBC), median overall survival (OS) still ranges from 14 to 50 months, depending on tumor subtypes. Patients often receive many successive lines of therapy over the course of their disease. Few data on efficacy of 3rd and subsequent lines of chemotherapy are available. Although oral etoposide has been used for years in heavily pre-treated MBC patients, real-life data supporting its efficacy are lacking. Methods The primary objective was to assess progression free survival (PFS) in MBC patients having started oral etoposide as 3rd line chemotherapy or more, using the French Epidemiological Strategy and Medical Economics (ESME) database, established in 2014 by Unicancer. Secondary objectives were overall survival (OS) and descriptive and prognostic analyses. Results Of 16703 MBC patients included in the ESME program and covering the 2008-2014 period, 323 received at least 14 days of oral etoposide. Amongst them, 5 were men, 46 received etoposide as 1st or 2nd line chemotherapy, and 7 had no information available regarding line of treatment, leaving 265 for analysis. All received oral etoposide, 255 as monotherapy while 10 pts combined with trastuzumab for HER2+ MBC. Patients' and tumour characteristics are shown in table 1. The mean line of chemotherapy with oral etoposide was 5 (range 3-12). With a median follow-up of 32.2 months [CI95%: 22.0-42.1], median PFS and OS (from initiation of oral etoposide) were 3.1 months [95% CI 2.8-3.7] and 7.4 months [95% CI 6.0-9.9], respectively. No predictive factor for PFS could be identified (age at MBC diagnosis, BC subtype, number of metastatic sites, presence of visceral metastases, disease-free interval, line of treatment). Only a trend for longer PFS was seen in patients > 50 years old, with longer disease-free interval and receiving etoposide earlier. Triple-negative MBC had shorter OS compared to other subtypes (p=0.03). Of note, OS was stable around 7 months for subsequent lines following a 3rd line of chemotherapy. n%Age at MBC diagnosis< 50 yo8331.3≥ 50 yo18268.7Primary BC subtypeER+ HER2-16662.6HER2+3814.3Triple negative5621.1ND51.9Number of metastatic sites115458.1≥ 211141.9Visceral metastasisNo13249.8Yes13350.2Disease-free intervalde novo4015.16-24 months4115.524-60 months7427.9> 60 months11041.5Chemotherapy line36323.846524.554717.764316.3≥ 74717.7 Conclusions Oral etoposide may achieve significant disease control in heavily pre-treated MBC, with a 3.1-month median PFS and independently from prognostic factors. Moreover, etoposide has the major advantage of an oral drug administered at home with a low cost. A case-control study is ongoing. Citation Format: Lerebours F, Carton M, Bacrie J, Pierga J-Y, Rouzier R, Saghatchian M, Dalenc F, Mailliez A, Levy C, Firmin N, Debled M, Leheurteur M, Desmoulins I, Lefeuvre C, Goncalves A, Uwer L, Ferrero J-M, Eymard J-C, Petit T, Mouret-Reynier M-A, Piot I, Perrocheau G, Caillot C, Perol D. Oral etoposide (VP-16) in heavily pre-treated metastatic breast cancer: A multicenter national observational study [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-14-06.

Cisplatin with veliparib or placebo in metastatic triple-negative breast cancer and BRCA mutation-associated breast cancer (S1416): a randomised, double-blind, placebo-controlled, phase 2 trial.

Discovery and development of novel therapies in advanced breast cancer: rapid development of ribociclib

Background: Triple negative (TN) breast cancers account for 15% of all breast cancers, are two-fold higher in African American women, have high histological grade, a poor prognosis and until recently no viable therapeutic targets. Epidermal growth factor receptor (EGFR) is over-expressed in more than 50% of triple negative breast cancers, but the use of agents blocking EGFR has produced disappointing results in metastatic breast cancer. Inhibitors of Mammalian Target of Rapamycin (mTOR) have demonstrated moderate activity as single agents in metastatic breast cancer. mTOR inhibitors have been demonstrated to activate the Akt pathway by a possible feedback mechanism, which could potentially sensitize TN breast cancer cells to upstream inhibitors. We have previously demonstrated synergistic antitumor effects with combined mTOR and EGFR inhibition in TN breast cancers. Eukaryotic translation initiation factor (eIF4E) is a protein downstream of mTOR and a target of PI3K/Akt and Erk signaling, and is important in mRNA translation, cell proliferation and apoptotic resistance. We evaluated the effects of EGFR and mTOR inhibition on apoptotic markers, and correlated these effects with eIF4E protein expression.Methods: Apoptotic assay and colony formation analysis were performed following mTOR inhibition with rapamycin and EGFR inhibition with lapatinib or erlotinib in TN breast cancer cells (MDA-MB-231, MDA-MB-468, HCC1806). Effects of EGFR and mTOR inhibition on downstream proteins in TN breast cancer in vitro and in vivo were examined through western blotting analysis with p-EGFR, pAkt, p-Erk, p-S6, and p-eIF4E.Results: We observed differential apoptotic effects of EGFR and mTOR inhibition in TN breast cancers cells. The combination resulted in a significant increase in apoptosis in MDA-MB-468 cells in vitro, but no increase in apoptosis was seen in MDA-MB-231 or HCC1806 cells. As expected, correlating with the apoptotic effects, expression of p-eIF4E was decreased in MDA-MB-468 cells treated with the combination of mTOR and EGFR inhibition in vitro. In contrast, both MDA-MB-231 and HCC1806 cells had high baseline levels of eIF4E, which increased in response to treatment with EGFR and mTOR inhibitors. Using a colony forming assay, we demonstrated that the combination of EGFR and mTOR inhibition resulted in cytostatic effects in HCC1806 cells. The combination of EGFR and mTOR inhibition did not result in apoptosis in MDA-MB-231 cancers in vivo, and these xenograft tumors had high level of eIF4E at baseline.We are currently evaluating the effects of lapatinib and rapamycin on apoptotic pathways in MDA-MB-468 cancers in vivo.Conclusion: Based on our previous findings, we are developing a clinical trial in which patients with metastatic TN breast cancers are treated with lapatinib and everolimus. These results suggest that this combination may be more effective in TN breast cancers with low levels of eIF4E, and this will be explored using metastatic research biopsies. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5078.

Background: LIV-1 is a highly prevalent transmembrane protein in breast cancer cells. Ladiratuzumab vedotin (LV), SGN-LIV1A, is an investigational antibody-drug conjugate (ADC) that targets LIV-1 via a humanized IgG1 monoclonal antibody conjugated to monomethyl auristatin E (MMAE) by a protease-cleavable linker. LV is internalized when it binds LIV-1 on cell surfaces and MMAE is released, which binds tubulin and induces apoptosis. LV has been shown to be active and tolerable in metastatic breast cancer (mBC) at a recommended dose of 2.5 mg/kg every 21 days (Modi 2017). More frequent, fractionated dosing has improved the activity and/or safety of other ADCs. Thus, this study is actively accruing subjects with metastatic triple negative breast cancer (mTNBC; estrogen receptor (ER)/progesterone receptor (PR)/human epidermal growth factor receptor 2 (HER2) receptor-negative) and endocrine-resistant ER+ or PR+ (hormone receptor [HR+])/HER2-negative mBC to test weekly dosing of LV (Days 1, 8, and 15 of every 3-week cycle). Methods: This study is enrolling up to 82 subjects (42 HR+/HER2-negative and 40 mTNBC) into dose escalation and dose expansion cohorts (NCT01969643). Eligible subjects are females ≥18 years old with pathologically and radiologically confirmed metastatic HR+/HER2-negative or mTNBC with at least 1 measurable lesion per RECIST v1.1. Subjects with HR+/HER2-negative disease must have received no more than 1 prior line of cytotoxic chemotherapy in the locally advanced (LA)/mBC setting, either as single agent or combination therapy. Subjects with mTNBC must have received 1 prior line of cytotoxic chemotherapy in the LA/mBC setting. Progression within 6 months of completion of neoadjuvant or adjuvant therapy is considered an LA/mBC regimen. Subjects must have adequate organ function, ECOG status of ≤1, and no ≥ Grade 2 peripheral neuropathy. Subjects with brain lesions must have received definitive treatment of the lesions. Prior therapy with MMAE-containing agents is not allowed. Dose escalation follows the modified toxicity probability interval method (Ji 2010). Dose expansion cohorts will provide data about activity and tolerability. Tumor assessments will be conducted every 2 cycles per RECIST v1.1 and all subjects will be followed for safety. Pharmacokinetics and markers of pharmacodynamics will be assessed. Primary safety endpoint is the incidence of adverse events and dose-limiting toxicities. Key efficacy endpoints include confirmed overall response rate, duration of response, and progression-free survival. Citation Format: Heather C Beckwith, Diana C Medgyesy, Jame Abraham, Rita Nanda, Katherine HR Tkaczuk, Ian E Krop, Lajos Pusztai, Shanu Modi, Monica M Mita, Jennifer M Specht, Sara A Hurvitz, Hyo S Han, Kevin Kalinsky, Sharon Wilks, Joyce O’Shaughnessy, Lowell L Hart, Hope S Rugo, Zahi I Mitri, Phillip M Garfin, Howard A Burris III. SGNLVA-001: A phase 1 open-label dose escalation and expansion study of SGN-LIV1A administered weekly in breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr OT-03-03.

Background: Triple-negative (negative for human epidermal growth factor receptor 2 [HER2] and estrogen and progesterone receptors) breast cancer (TNBC) is the breast cancer subtype with the worst prognosis. It represents approximately 15% -20% of all breast cancer cases. BRCA 1 and /or BRAC 2 mutation accounts for about 15% of all TNBC and remains poor outcomes for such patients. TORCHLIGHT trial is a randomized, double-blinded, phase 3 study assesses the efficacy and safety of toripalimab (programmed cell death-1 inhibitor) combined with nab-paclitaxel (nab-P) as a first-line treatment for patients diagnosed with metastatic or recurrent TNBC. The (progression-free survival) PFS and (overall survival) OS analysis, showed a significant improvement in PD-L1 positive (CPS ≥ 1) tumors. Phase III OlympiAD study has established the efficacy of Poly ADP-ribose polymerase inhibitors (PARPi) olaparib in patients with germline BRCA gene mutation (gBRCAm) and human epidermal growth factor receptor 2 (HER2) negative metastatic breast cancer. Mefuparib hydrochloride (CVL218) is a second generation of PARPi with low hematological toxicity and the ability to cross the blood-brain barrier. The major purpose of this study is to explore the RP2D, efficacy and safety of CVL218 combined with PD-1 inhibitors and paclitaxel nanoparticle albumin-bound in patients with TNBC who have failed previous first-line treatment. The second endpoint of this study is to analyze the efficacy of each subgroup according to PD-L1 expression and HRD (Homologous Recombination Deficiency) mutation status. Methods: This open- labeled, phase Ib/II clinical study was conducted in China. In phase Ib, the “3+3” principle is used to explore the RP2D of CVL218. Two dose escalation of CVL218 were preset, which are 500mg twice daily (BID) and 700mg BID. CVL218 administered orally in combination with toripalimab 240 mg on Day 1 of every 21-day cycle and paclitaxel nanoparticle albumin-bound 125 mg/m2 on Day 1 of every 21-day cycle. The first cycle (21 days) after administration was also defined as the DLT (dose-limiting toxicity) observation period. At last, no DLT was observed in the 3 evaluable subjects in the CVL218 500 mg BID dose group, and DLT was observed in 2 evaluable subjects in the 700 mg BID dose group, including creatinine increased and aspartate aminotransferase, Alanine aminotransferase increased. Therefore, the RP2D was determined as 500 mg BID. Patients in phase II cohort A were advanced TNBC with either CPS ≥ 1 or HRD gene pathogenic variants. All these patients received CVL218 (500mg BID) + toripalimab (240 mg) + paclitaxel nanoparticle albumin-bound (125 mg/m2, ). Results: From July 2023 to 15 July 2024 data, a total of 6 subjects were enrolled in Phase Ib and 5 subjects were enrolled in Phase II. The median age of the 11 subjects was 55.2 years. In phase Ib, The RP2D of CVL218 was identified as 500 mg BID. The preliminary efficacy was perfomed every 6 weeks in the first half a year and then once every 12 weeks thereafter in both phase I and II according to RECISTv 1.1. Among 11 patients, ORR (Objective Respond Rate) was 72.7% (8 PR, 2 SD), and DCR (Disease Control Rate) was 90.9%. The most common Grade 3 or higher treatment-related AEs (TRAEs) were hepatic function injury (2.6%), adynamia (1.8%), creatinine increased (0.8%), neutrophils decreased (0.8%), white blood cell decreased (0.8%), exanthema (0.8%), and peripheral sensory nerve disorder (0.8%), No Grade 5 TRAE. A total of 9 treatment-related SAEs in 6 patients (54.5%) were observed, including 2 aspartate aminotransferase increased, 2 alanine aminotransferase increased, 1 creatinine increased, 1 liver function injury, 1 adynamia, 1 neutrophils decreased, 1 fever, and 1 ventricular premature beats. All these SAEs recovered after symptomatic treatment. Conclusion: Mefuparib Hydrochloride(CVL218) combined with PD-1 and chemotherapy appears to be well tolerated and has preliminary efficacy in TNBC patients. In this phase II study, stratified analyses will be conducted for PD-L1 expression and HRD status. In patients with BRCA 1 and /or BRAC 2 mutation TNBC, this CVL218 combination therapy is expected to further break through the clinical treatment effect. Citation Format: Jian Zhang, Rujiao Liu. A phase Ib/II study of PARPi Mefuparib Hydrochloride (CVL218) in combination with PD-1 inhibitor plus chemotherapy in metastatic or recurrent triple-negative breast cancer (TNBC) [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P4-04-31.

Background: Triple-negative breast cancer (TNBC) is an aggressive cancer with inferior survival outcomes. Although weekly paclitaxel (WP) is effective in the treatment (tx) of metastatic breast cancer (MBC), optimization of therapies for patients (pts) with TNBC is essential. Angiogenesis is a hallmark of advanced cancer, with subset analyses suggesting activity of angiogenesis inhibitors in TNBC. Tivozanib (TIVO) is a potent and selective inhibitor of vascular endothelial growth factor receptors (VEGFR) 1, 2, and 3 with a promising role in metastatic renal cell carcinoma, and established safety in Phase I combination with WP in MBC. Purpose: This Phase II trial will assess the efficacy and safety of TIVO + WP in the first-line setting for pts with advanced or metastatic TNBC and evaluate the performance of candidate angiogenesis biomarkers. Objectives: The primary objective of this study is to compare progression-free survival (PFS) of pts treated with TIVO + WP vs pts treated with placebo (PB) + WP. Secondary objectives include objective response rate (ORR), overall survival (OS), safety and tolerability, quality of life, and correlative candidate biomarker endpoints. The pharmacokinetics of TIVO + WP also will be characterized. Study Design and Methods: This multicenter, randomized, PB-controlled, two-arm study will enroll pts with metastatic or unresectable TNBC (evaluable per RECIST) and no prior systemic therapy. Pts must have confirmed available archival tumor tissue. Pts will be stratified by ECOG performance score and number of metastatic sites, then randomized to receive either oral TIVO 1.5 mg once daily for 3 weeks (wks) on/1 wk off and intravenous WP 90 mg/m2 for 3 wks on/1 wk off, or PB + WP. One cycle will be 4 wks; tx will continue until disease progression or unacceptable toxicity. Archival tumor tissue and blood samples will be evaluated for response biomarkers, including a hypoxia sensitivity gene signature, a myeloid resistance gene signature, and angiogenic ligands. All pts will be followed for survival until death. Adverse events will be monitored throughout the study. Pharmacokinetic samples will be collected during cycles 1 and 2. PAM-50–defined intrinsic molecular subtype populations also will be evaluated retrospectively. Recruitment of 130 patients is planned, with an interim analysis after 80 pts to measure ORR (130 pts with a total of 82 investigator-assessed PFS events provides 80% power to detect statistically significant PFS differences between tx arms). Endpoint analyses will use the intent-to-treat population. The primary efficacy analysis will use investigator assessments of response and a two-sided 95% confidence interval for the hazard ratio produced using Cox proportional hazards regression models. OS will be compared using the log-rank test. Analyses of candidate biomarkers and determination of an optimal predictive cutoff for response also are planned. Trial enrollment will commence in fall 2012. Conclusion: This study will determine whether TIVO, a selective and potent VEGFR inhibitor, combined with WP improves clinical outcomes in pts with TNBC, and whether clinical activity is associated with candidate angiogenesis biomarkers. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr OT2-3-11.

Abstract: Trials in progress Authors: Dr Rachel Dear, A/Prof Christine Chaffer, Dr Beatriz Perez San Juan Title: 4CAST: A Phase 1b dose exploration and dose expansion, open-label study evaluating the safety and efficacy of INO-464 in combination with Chemotherapy in patients with metASTatic breast cancer. Problem statement: Metastatic triple negative breast cancer (mTNBC) has poor outcomes, with rapid progression and a median overall survival of 16 months. Standard treatment includes chemotherapy, with a possible role for immunotherapy. The antibody-drug conjugate sacituzumab govitecan was been granted recent approval. The development of new targeted treatments remains an unmet need. The androgen receptor is a mediator of chemotherapy-resistance in triple-negative breast cancer. Taxane and platinum-based chemotherapy induces cell plasticity and the emergence of chemotherapy-resistance. The androgen receptor (AR) antagonist, INO-464, but not abiraterone or enzalutamide, blocks chemotherapy induced cell plasticity to inhibit and primary and metastatic tumour growth. Three early-phase prospective clinical studies investigating anti-androgen therapy have demonstrated clinical benefit of single-agent AR-targeted agents in women with metastatic AR positive TNBC. The 450 mg daily start dose of INO-464 was well-tolerated and declared the recommended phase 2 dose. Preliminary laboratory data demonstrates an increase in survival and suppression of metastatic TNBC when INO-464 is used in combination with docetaxel. Methods: To determine the feasibility, safety and efficacy of INO-464 in combination with chemotherapy for the treatment of metastatic breast cancer. In Part 1 (dose exploration) of the trial we aim to establish the tolerability and safety and determine the recommended phase 2 dose of INO-464 when used in combination with docetaxel. Part 1 will recruit 6-18 females or males with locally advanced or metastatic breast cancer ie hormone receptor positive, HER2-positive or triple-negative breast cancer. In Part 2 (dose expansion) the clinical activity INO-464 and docetaxel in participants with metastatic triple negative breast cancer will be assessed. Results: Ethics approval for Part 1 of the trial was granted in May 2021. The trial received governance approval from St Vincent’s Hospital governance in June 2022. Recruitment commenced on the 1 July 2022. The trial has received 40 enquiries, of which three patients were eligible and one patient has consented to the trial and will be ready to start in the next two weeks. Conclusion: This investigator-initiated trial is an example of a collaborative effort between the Garvan Institute of Medical Research and the Kinghorn Cancer Centre at St Vincent’s Hospital. If the combination of INO-464 and docetaxel is shown to be safe we look forward to recruiting to the part 2 dose expansion phase across multiple Australian sites. This is study is registered with ClinicalTrials.gov NCT04947189. Disclosure of interests: A/Prof Christine Chaffer is the Managing Director of Kembi Therapeutics that is providing the investigational product for the clinical trial. Citation Format: Rachel F. Dear, Kathleen Batty, Beatriz Perez, Christine Chaffer. 4CAST: A Phase 1b dose exploration and dose expansion, open-label study evaluating the safety and efficacy of INO-464 in combination with Chemotherapy in 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 OT1-02-01.