Refractory Metastatic Breast Cancer Research Articles

A phase II trial to assess the impact of β2 adrenergic blockade in immune checkpoint inhibitor (ICI)– refractory metastatic triple negative breast cancer (mTNBC).

TPS1141 Background: In PD-L1+ mTNBC patients (pts), the standard of care treatment is chemotherapy and pembrolizumab (P) in the first-line setting. It has been shown that acquired resistance to P occurs as a result of immune exhaustion. Further, our group and others have demonstrated that chronic β2-adrenergic receptor (β-AR) signaling suppresses CD8+ cytotoxic T lymphocytes (CTL) function, drives their exhaustion, and increases the numbers of immunosuppressive myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs) in the tumor microenvironment (TME), thus supporting tumor proliferation. Consequently, abrogation of β-AR signaling using the pan β-blocker propranolol or β-AR-/- knockout mice increased the intratumoral frequency of CTLs and elevated the CTL:Treg ratio (Bucsek et al. Cancer Res. 2017; PMID: 28819022). Similarly, mouse tumor models also demonstrated decreased exhaustion markers (PD1, TIM3, LAG3) on CTLs when β-AR was blocked, via propranolol (Qiao G et al. Cancer Immunol Res. 2021, PMID: 33762351). Confirming this phenomenon, we have shown, in a prospective clinical trial in metastatic melanoma, that β-AR blockade with propranolol significantly increased response to P with an objective response rate (ORR) of 78%, as opposed to 30-40% with P monotherapy (Gandhi et al, Clin Cancer Res 2021, PMID: 33127652). Therefore, we hypothesize that using propranolol in an ICI refractory population should improve responses to ICIs. Methods: This is a phase II single-arm, non-randomized single-center study for mTNBC pts. Participants will bewomen >=18 yrs with PD-L1+ mTNBC, who have progressed on treatment with chemotherapy and P in the upfront setting. They will continue P every 3 weeks in addition to 30 mg propranolol twice a day, based on our ongoing clinical trial in metastatic melanoma (NCT03384836) which has demonstrated safety with this combination. Treatment will continue until disease progression per irRECIST. The primary endpoint is ORR, defined as complete or partial response to treatment. The secondary endpoint is safety, 6-month progression-free survival and overall survival. As an exploratory endpoint, changes in tumor and blood immune markers will be assessed. In stage 1, n1=12 evaluable pts will be enrolled. If ≥ 1/12 response is observed, then the study will continue to enroll another n2=9 pts for a total of n=21, otherwise it will be suspended for futility. If ≥ 3/21 responses are observed, then the proposed therapy will be considered promising. Pre- and post-treatment tumor biopsies and sequential blood samples will be analyzed for changes in stress-induced biomarkers (epinephrine, norepinephrine, and frequency of CTL, MDSC, Treg) and expression of exhaustion markers (PD1, TIM3, LAG3). The study is currently open. Clinical trial information: NCT05741164 .

Cost-utility analysis of sacituzumab govitecan versus chemotherapy for the treatment of metastatic triple-negative breast cancer in Singapore

ABSTRACT Objective To assess the cost-effectiveness of sacituzumab govitecan for treating relapsed or refractory metastatic triple-negative breast cancer (TNBC) in Singapore. Methods A three-state partitioned survival model was developed to evaluate the cost-effectiveness of sacituzumab govitecan from a healthcare system perspective over 5 years. Clinical inputs were obtained from the ASCENT trial. Health state utilities were retrieved from the literature and direct costs were sourced from public healthcare institutions in Singapore. Sensitivity and scenario analyses were conducted to explore the impact of uncertainties and assumptions on cost-effectiveness results. Results Compared with single-agent chemotherapy, sacituzumab govitecan was associated with a base-case incremental cost-effectiveness ratio (ICER) of S$328,000 (US$237,816) per quality-adjusted life year (QALY) gained. One-way sensitivity analyses showed that the ICER was most sensitive to the cost of sacituzumab govitecan and progression-free utility values. Regardless of variation in these parameters, the ICER remained high, and a substantial price reduction was required to reduce the ICER. Conclusion At its current price, sacituzumab govitecan does not represent a cost-effective treatment for relapsed or refractory metastatic TNBC in Singapore. Our findings will be useful to inform funding decisions alongside other factors including clinical effectiveness, safety, and budget impact considerations.

ANTITUMOR DRUG BASED ON THE GENE-MODIFIED VACCINIA VIRUS VV-GMCSF-Lact

Virotherapy, or therapy with oncolytic viruses, is one of the most rapidly developing approaches to the treatment of a wide range of solid tumors. The article is devoted to the development and study of the properties of the first domestic drug based on recombinant vaccinia virus. The recombinant virus VV-GMCSF-Lact was engineered from Lister strain (L-IVP) vaccinia virus. The cytotoxic activity and antitumor efficacy of the virus against human tumor cells of various tissue origins were shown on cell cultures and tumor models. The drug has successfully passed preclinical studies as a drug against human breast cancer, including a triple negative phenotype. The drug was proven to be safe, well tolerated and pharmacologically effective. It is currently in Phase I clinical trials to study safety, tolerability and pharmacokinetics in patients with relapsed and/or refractory metastatic breast cancer. VV-GMCSF-Lact is the first Russian antitumor oncolytic virus which received the permission from the Russian Ministry of Health to conduct clinical trials.

An integrated analysis of Sacituzumab govitecan in relapsed or refractory metastatic triple-negative breast cancer.

Sacituzumab govitecan (SG) is an antibody-drug conjugate that targets the human trophoblast cell-surface antigen 2 to deliver SN-38 to cancer cells. In this study, we assessed the efficacy and safety of SG in patients with relapsed or refractory metastatic triple-negative breast cancer (RM-TNBC). For this integrated analysis, from inception to January 2, 2023, we searched PubMed, Web of Science, Embase, and Cochrane library databases for prospective studies that evaluated SC in RM-TNBC patients. Primary endpoints were survival outcomes and responses. Secondary endpoints were all grade and grade ≥ 3 toxicities. Six hundred potentially relevant records were screened. Our analysis included 3 trials (412 patients). Median overall survival was 12.9 months (95% confidence interval [CI], 11.5-14.4), progression-free survival was 5.7 months (5% CI, 5.1-6.3), and duration of objective response was 7.4 months (5% CI, 5.8-9.0). The objective response rate was 34%, and the disease control rate was 71%. Key grade ≥ 3 toxicities (in over 10% of the patients) included neutropenia (46%), leukopenia (12%), febrile neutropenia (11%), diarrhea (11%), and anemia (10%). Four treatment-related deaths were reported. SG was associated with effectiveness in patients with RM-TNBC. Myelosuppression and diarrhea were the primary treatment-related adverse events.

Cost-effectiveness of sacituzumab govitecan versus chemotherapy in patients with relapsed or refractory metastatic triple-negative breast cancer

BackgroundThe effectiveness of sacituzumab govitecan for metastatic triple-negative breast cancer (TNBC) has been reported in recent research, however, the value of the effectiveness and cost of sacituzumab govitecan is still unclear.MethodsA microsimulation model was developed using data from the ASCENT trial to assess the cost-effectiveness of sacituzumab govitecan for patients with relapsed or refractory metastatic TNBC over a lifetime. Model inputs, including clinical data, patient characteristics, and direct medical costs, were based on the ASCENT trial, public databases, and published literature. The primary outcomes of the model were the incremental cost-effectiveness ratio (ICER) and quality-adjusted life-years (QALYs). Univariate and probabilistic sensitivity analysis (PSA) and multiple scenario analyses were performed to address the uncertainty of the model.ResultsOur results revealed that sacituzumab govitecan versus chemotherapy costs $293,037 and yielded an additional 0.2340 of QALYs in the whole population with metastatic TNBC, leading to an ICER of $1,252,295 gained. And in the population with metastatic TNBC without brain metastasis, the sacituzumab govitecan versus chemotherapy costs $309,949 and obtained an extra 0.2633 of QALYs, which resulted in an ICER of $1,177,171/QALYs. Univariate analyses indicated that the model outcomes were most sensitive to the drug cost of sacituzumab govitecan, the utility of progression-free disease, and the utility of progressed disease.ConclusionFrom the US payer perspective, sacituzumab govitecan is unlikely to be a cost-effective option for patients with relapsed or refractory metastatic TNBC compared with chemotherapy. Based on the value standpoint, a price decrease of sacituzumab govitecan is expected to increase the cost-effectiveness of sacituzumab govitecan in patients with metastatic TNBC.

The overall survival analysis of FUTURE-C-PLUS: Combination of famitinib with camrelizumab plus nab-paclitaxel as first-line treatment for advanced, immunomodulatory triple-negative breast cancer—An open-label, single-arm, phase 2 trial.

1086 Background: Camrelizumab and nab-paclitaxel demonstrated promising anti-tumour activity in refractory metastatic immunomodulatory triple-negative breast cancer (TNBC) in FUTURE trial. Anti-angiogenic agents have been reported to facilitate immune infiltration. Famitinib is a tyrosine kinase inhibitor targeting VEGFR-2, PDGFR and c-kit. The FUTURE-C-PLUS trial (NCT04129996) which added famitinib to camrelizumab and nab-paclitaxel is a single-arm, phase 2 trial evaluating this novel triplet combinatorial strategy in patients with advanced immunomodulatory TNBC. Study design and the primary endpoint ORR has been reported previously (Zhi-ming Shao, et al. ASCO 2021, Abstract 1007). The final PFS data had been published in Clinical Cancer Research (Clin Cancer Res 2022;28:2807–17). Here, we reported the final overall survival of this trial. Methods: Briefly, this study enrolled women aged 18-70 years, with previously untreated, histologically confirmed, unresectable, locally advanced, recurrent or metastatic immunomodulatory TNBC. Immunomodulatory TNBC was defined as CD8 expression on at least 10% of cells using immunohistochemistry analysis. Eligible patients received the triple therapy. Results: Forty-eight patients were enrolled and treated between Oct 2019 and Oct 2020. The median follow-up was 33.1 months (range, 31.8–34.4). 39 (81.3%, 95% CI 70.2-92.3) patients had a confirmed objective response which has been reported in ASCO 2021. At this updating data cutoff (Feb 1, 2023), the median progression-free survival was 13.6 months (95% CI, 8.4-18.8). While overall survival was 29.4 months (95% CI, 23.3-35.5). The disease control rate was 95.8% (46/48). The most common treatment-related grade 3 or 4 adverse events were neutropenia (16 [33.3%]), anemia (5 [10.4%]), febrile neutropenia (5 [10.4%]), and thrombocytopenia (4 [8.3%]). No new safety concerns were detected. No treatment-related deaths were reported. Conclusions: These data, combined with those from our previous reports, provide further evidence for the triplet combination of famitinib, camrelizumab and nab-paclitaxel as an active therapy in advanced Immunomodulatory TNBC. To our knowledge, this is the best overall survival reached in first-line treatment of advanced TNBC. A randomized controlled FUTURE-Super trial is ongoing to further validate these findings. Clinical trial information: NCT04129996 .

Abstract P3-07-12: Allogeneic, Antigen-Presenting, GM-CSF-secreting, SV-BR-1-GM Whole Cell Therapeutic Vaccine in Advanced Metastatic Breast Cancer

Abstract Background: SV-BR-1-GM is an irradiated allogeneic cell line derived from a hormone receptor-negative (HR-) HER2-positive (HER2+) breast cancer (BC), now engineered to express HLA class I and II antigens, secrete GM-CSF and function as an antigen-presenting cell. Here we report post-hoc exploratory data for metastatic BC (MBC) patients treated with the SV-BR-1-GM regimen (SV) alone (NCT03066947) and in combination (CO) with immune checkpoint inhibitors (ICIs) (NCT03328026). Methods: SV includes cyclophosphamide 300 mg/m2 i.v. 48-72 hours prior to SV-BR-1-GM (20 × 106 cells) intradermally followed by interferon-alpha-2b at the SV-BR-1-GM inoculation sites on days 2 and 4. SV was given every 2 weeks for 3 cycles and then monthly in NCT03066947, and every 3 weeks in combination with PD-1 inhibitors in NCT03328026. Treatment was continued until disease progression or unacceptable toxicities. Results: A total of 34 refractory MBC patients (pts) were treated, including 24 with SV, and 14 with CO, including 4 who crossed over from SV to CO plus one who restarted the SV after a protocol specified administrative interruption in treatment. Median prior regimens were 5; 55% of pts had hormone receptor-positive (HR+) BC, 42% had HER2+ BC, and 16% were triple-negative BC (TNBC). Objective response rates (ORR) were 4% for monotherapy and 7% for combination. Clinical benefit rate (CBR) was 21% for monotherapy and 29% for combination. Responses and clinical benefits were seen across most BC subtypes (see table). Notably, CBR among 10 pts with HR+ BC (any HER2) who received the combination was 50% (5/10). The duration of response (DOR) among 4 patients treated with monotherapy was 49-223 days and DOR among 6 patients treated with combination was 72-292 days. Median PFS was 2.8 months for monotherapy and 4.2 months for combination. Median OS was 7.0 months for monotherapy, and 12.0 months for combination. Of 28 pts with available prior treatment data, 12 (43%) had PFS on study treatment exceeded PFS on prior treatment, of these 8/12 had >1 HLA match and 5/8 had ≥ 2 loci HLA-matched with SV-BR-1-GM. PFS ratio improvement was independent of the prior number of lines of therapy or BC subtypes. The SV-BR-1GM regimen was well tolerated with the most common treatment-related adverse events (AEs) being injection site reaction in 67%. There was no dose-limiting toxicity, special interest AEs such as cytokine storm, and no grade 5 observed. There were 2 non-treatment-related grade 4 AEs: worsening pleural effusion and altered mental status. Significant improvement in PFS was observed in patients with matched HLA and in association with the delayed-type hypersensitivity skin test, peripheral blood circulating tumor cells, and cancer-associated macrophages. Conclusions: SV-BR-1-GM demonstrated promising activity in patients with MBC. Treatment was well tolerated with no concerning AEs. The PFS ratio compares favorably with prior penultimate standards of care, more notably in patients with matched HLA. Clinical benefits were observed across multiple subtypes of BC, particularly in patients with HR+ disease receiving combination therapy. Phase II clinical trial is currently ongoing to evaluate the efficacy of SV-BR-1-GM in combination with ICIs. Clinical benefit and PFS on SV-BR-1-GM SV-BR-1-GM Whole Cell Therapeutic Vaccine in Heavily Pre-Treated Metastatic Breast Cancer Results Stratified by HER2 and HLA Matching Citation Format: Saranya Chumsri, William Williams, Mingjin Chang, Miguel Lopez-Lago, Charles Wiseman, Jarrod Holmes, Chaitali Nangia, Karim Mohammed, Minal Barve, Shaker Dakhil, Bonnie Guerin, Giuseppe Del Priore, Carmen Calfa. Allogeneic, Antigen-Presenting, GM-CSF-secreting, SV-BR-1-GM Whole Cell Therapeutic Vaccine in Advanced 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 P3-07-12.

A Phase IIb, single arm, multicenter trial of sacituzumab govitecan in Chinese patients with metastatic triple-negative breast cancer who received at least two prior treatments.

Refractory or relapsing metastatic triple-negative breast cancer (mTNBC) has a poor prognosis. Sacituzumab govitecan (SG) is a novel antibody-drug conjugate, targeting human trophoblast cell-surface antigen 2 (Trop-2). This is the first report of SG's efficacy and safety in Chinese patients with mTNBC. EVER-132-001 (NCT04454437) was a multicenter, single-arm, Phase IIb study in Chinese patients with mTNBC who failed ≥2 prior chemotherapy regimens. Eligible patients received 10mg/kg SG on Days 1 and 8 of each 21-day treatment cycle, until disease progression/unacceptable toxicity. The primary endpoint was objective response rate (ORR) assessed by the Independent Review Committee. Secondary endpoints included: duration of response (DOR), clinical benefit rate (CBR), progression-free survival (PFS), overall survival (OS) and safety. Eighty female Chinese patients (median age 47.6 years; range 24-69.9 years) received ≥1 SG dose with a median of 8 treatment cycles by the cutoff date (August 6, 2021). Median number of prior systemic cancer treatments was 4.0 (range 2.0-8.0). ORR and CBR were reported 38.8% (95% confidence interval [CI]: 28.06-50.30) and 43.8% (95% CI, 32.68-55.30) of patients, respectively. The median PFS was 5.55 months (95% CI, 4.14-N/A). SG-related Grade ≥3 treatment-emergent adverse events (TEAEs) were reported in 71.3%, the most common were neutrophil count decreased (62.5%), white blood cell count decreased (48.8%) and anemia (21.3%); 6.3% discontinued SG because of TEAEs. SG demonstrated substantial clinical activity in heavily pretreated Chinese patients with mTNBC. The observed safety profile was generally manageable.

An open label phase II study of safety and clinical activity of naltrexone for treatment of hormone refractory metastatic breast cancer

SummaryThe opioid receptor (OR) antagonist naltrexone inhibits estrogen receptor-α (ER) function in model systems. The goal of this study was to determine the clinical activity of naltrexone in patients with ER-positive metastatic breast cancer. Patients with hormone receptor positive metastatic breast cancer were enrolled on a phase II study of naltrexone. An escalating dose scheme was used to reach the planned dose of 50 mg daily. The primary objective of the study was to evaluate response to therapy as measured by stabilization or reduction of the tumor Maximum Standardized Uptake Value (SUVmax) at 4 weeks by PET-CT scan. The secondary objectives included safety assessment and tumor SUVmax at 8 weeks. Out of 13 patients we enrolled, 8 patients had serial PET-CT scans that were evaluable for response. Of these 8 patients, 5 had stable or decreased SUVmax values at 4 weeks and 3 had clinical or imaging progression. Median time to progression was short at 7 weeks. Naltrexone was well tolerated. There were no discontinuations due to toxicity and no grade 3 or 4 toxicities were noted. Naltrexone showed modest activity in this short study suggesting the contribution of opioid receptors in ER-positive breast cancer. Our data do not support further development of naltrexone in hormone refractory breast cancer. It is possible that more potent peripherally acting OR antagonists may have a greater effect. (ClinicalTrials.gov Identifier: NCT00379197 September 21, 2006).

248P Sacituzumab govitecan in Chinese patients with metastatic triple-negative breast cancer who received at least two prior treatments

Refractory or relapsing metastatic triple-negative breast cancer (mTNBC) has a poor prognosis. Sacituzumab govitecan (SG) is a novel antibody-drug conjugate, targeting human trophoblast cell-surface antigen 2. This is the first time to report the efficacy and safety of SG in Chinese mTNBC patients.

The pathological and clinical landscape of refractory metastatic triple negative breast cancer: a narrative review.

Background and ObjectiveTriple negative breast cancer (TNBC) refers to a special subtype of breast cancer that is negative for the estrogen receptor, the progesterone receptors, and human epidermal growth factor receptor 2. As a group of diseases, it has strong heterogeneity. Refractory metastatic triple negative breast cancer (mTNBC) has even greater heterogeneity, more susceptibility to drug resistance, and faster progression, which makes it more difficult to treat effectively and significantly reduces a patient’s overall survival. Therefore, in order to overcome this difficulty in clinical practice, we need to deeply understand the special subgroup by analyzing definition and prognostic factors of refractory mTNBC and describing the therapeutic status and future treatment directions.MethodsRecent domestic and foreign guidelines, as well as clinical studies related to refractory mTNBC on PubMed and the China National Knowledge Infrastructure (CNKI) databases were retrospectively analyzed. The six keywords we selected were used for literature search. Two authors performed database searches independently, and disagreements over the results were mediated by a third reviewer.Key Content and FindingsAccording to the guidelines, refractory mTNBC has not been clearly defined. Related studies indicated that tumor heterogeneity may be one of the main mechanisms of early relapse or drug resistance in refractory mTNBC. The clinical treatment options for refractory mTNBC are very limited. Although chemotherapy is the standard treatment, it is limited by poor efficacy and intolerance in the clinical stage. Therefore, in recent years, many studies have explored novel treatment options. Both immunotherapy and poly(ADP-ribose) polymerase (PARP) inhibitors have been selected as first-line treatment in clinical studies, but gained limited benefits. Indeed, clinical studies have shown good efficacy with novel ADCs, which may be promising in the clinical treatment of refractory mTNBC.ConclusionsCurrently, improving the survival time and quality of life of refractory mTNBC are major challenges for clinicians. Novel therapies including immunosuppressive agents, PARP inhibitors, and ADCs rather than chemotherapy alone have achieved good results in the exploration of first-line treatment for refractory TNBC patients, but this warrants further research and investigation.

Theranostic pairing: ABY-025/251 targeting HER2 with 68Ga and 188Re—Minimized radioligands using Affibody peptide scaffold technology.

3093 Background: HER2 expressing tumors such as subsets of metastatic breast cancer and gastro-esophageal tumors can be targeted using specific antibodies or antibody-drug-conjugates (ADCs). However, some tumors remain refractory to treatment. External radiation therapy is unsuited to advanced metastatic disease. Targeted molecular radiation therapy has proven useful in other tumors such as neuroendocrine tumors or prostate cancer using 177Lu. 188Re is a beta emitting isotope that when chelated to the ABY-251 Affibody molecule has the potential to precisely target HER2 expressing tumors locally. The ABY-251 Affibody molecule is a very small, structured protein scaffold with a molecular weight of only 7 kDa targeting HER2 with high affinity (KD = 100pM). ABY-251 can be manufactured by chemical synthesis. A diagnostic analog molecule ABY-025 was also developed with chelation to 68Ga ideal for PET visualization. Methods: A pre-clinical study in mice was conducted to investigate tumor/tissue uptake, followed by a clinical diagnostic study for visualization in HER+ patients with metastatic breast cancer, to be followed by a theranostic study in humans. Results: Pre-clinical Study: A preclinical study in mice has previously demonstrated high contrast uptake in HER2 tumor tissue using the diagnostic analog ABY-025. Off target accumulation was seen in kidney tissue using the diagnostic ABY-025, which in the ABY-251 therapeutic molecule has been reduced by further engineering of the molecule. This molecule has now been proven to increase survival in mice bearing HER2+ tumors. Median survival in the treated animals was 68 days as compared to 29 and 27.5 days in animals treated with vehicle and non-labelled peptide respectively. Clinical diagnostic study ph1/2: ABY-025 was studied in HER2+ patients with metastatic breast cancer. In a study of 16 women with refractory metastatic breast cancer (>2 prior lines of therapy, 12 IHC positive and 4 IHC negative) 9 out of 10 patients showed high HER2 expression levels as measured with ABY-025 PET despite ongoing treatment with HER2 targeted therapy. Persistent high 68Ga-ABY-025 tumor uptake in patients despite treatment with standard HER2-targeted therapies is a sign of therapeutic drug resistance. These patients would be eligible for treatment with the therapeutic analog ABY-251 using 188Re generated beta radiation for tumor eradication. Clinical therapeutic study (planned): ABY-251 is in development to soon enter therapeutic clinical Ph1/2a trials in patients with refractory HER2+ tumors and positive tumor imaging using ABY-025 as a theranostic pair. Conclusions: A radiopharmaceutical theranostic approach diagnosing HER2+ patients with metastatic disease using 68Ga-ABY-025 for targetability and subsequent treatment using 188Re-ABY-251 seems feasible and is currently in clinical trials. Clinical trial information: NCT01858116.

Phase 1b/2 study of GX-I7 plus pembrolizumab in patients with refractory or recurrent (R/R) metastatic triple-negative breast cancer (mTNBC): The KEYNOTE-899 Study.

1081 Background: GX-I7 (efineptakin alfa) is a hybrid Fc-fused long-acting recombinant human IL-7 which plays an essential role in the development and homeostasis of T-cells. GX-I7 can potentially enhance the anti-tumor effect of pembrolizumab via induction of T-cell activity. Here, we report results of phase 1b/2 study of GX-I7 plus pembrolizumab in patients with R/R mTNBC. Methods: Eligible patients had R/R mTNBC that failed up to 3rd lines of chemotherapy in the metastatic setting. Phase 1b patients received GX-I7 in 5 dose levels ranging from 360 µg/kg to 1,440 µg/kg every 9 (Q9W) or 12 (Q12W) weeks plus pembrolizumab 200 mg Q3W (n=51). Phase 2 is an expansion cohort where 33 patients were treated with the recommended phase 2 dose (RP2D). The primary objective was to determine the RP2D for phase 1b and to assess the objective response rate (ORR) for phase 2. Results: The study included 84 patients (phase 1b, n=51; phase 2, n=33) and 53.6% (45/84) of patients have received 2nd to 3rd lines of previous therapy. In phase 1b, one dose-limiting toxicity (DLT; grade 3 skin rash) was reported in the 1,440 µg/kg cohort and GX-I7 1,200 µg/kg Q9W was selected as RP2D. The ORRs were 15.7% [95% confidence interval (CI): 7.0 – 28.6] for phase 1b (n=51) and 21.2% [95% CI: 9.0 – 38.9] for phase 2 (n=33). Median PFS was 2.4 months (95% CI: 2.1 – 2.7) at the median follow-up of 10.4 months for all patients combined (n=84). GX-I7 induced up to 3.6-fold (range 1.2 – 8.1) increase in absolute lymphocyte counts (including CD4+ and CD8+ T cell) in all dose levels. The most common treatment-related adverse events (AEs) of any grade were injection site reaction (50.0%), ALT increased (39.3%), pyrexia (38.1%) and rash (35.7%). The additional correlative study data will be presented. Conclusions: GX-I7 in combination with pembrolizumab demonstrated a manageable safety profile with promising anti-tumor activity in patients with R/R metastatic TNBC. Clinical trial information: NCT03752723. [Table: see text]

202P Abemaciclib in HR+/Her2- metastatic breast cancer patients after previous progression on palbociclib or ribociclib: Clinical experience in a tertiary hospital in Madrid, Spain

Preclinical and pharmacological data of the three approved cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) suggest differences among them. Abemaciclib inhibits other targets (CDK2/Cyclin A/E and CDK1/Cyclin B) causing cell cycle arrest in phases G1 and G2. In preclinical models, both senescence and apoptosis occurred earlier and at lower concentrations of Abemaciclib, compared to treatment with either palbociclib or ribociclib. Abemaciclib monotherapy or combined with tamoxifen has demonstrated activity in endocrine refractory metastatic breast cancer (MBC) who had received prior treatment with chemotherapy. There are limited clinical data of abemaciclib after a prior CDK4/6i exposure. To assess the safety profile and clinical outcomes of a consecutive cohort of HR+/HER2- MBC patients treated with abemaciclib beyond a previous progression on palbociclib or ribociclib at our institution. From April, 2020 until February, 2022, 11 women met inclusion criteria and were included. 9 out 11 received abemaciclib combined with tamoxifen. 8 patients had visceral involvement, none had brain metastasis. Median age was 69 years (range 42-84 years). Median time to abemaciclib from the end of previous CDK4/6i was 17.5 months (range 3-41 months). Median number of therapies until rechallenge was 3 (range 1-7) including chemotherapy in 54.5% of patients. Median time of follow-up was 6 months (range 1-22 months). The median progression-free survival (PFS) was 6 months (95%CI 3.5 – 10). 5 patients still continue on abemaciclib. Of these, 1 patient with hepatic metastases achieved complete response. Clinical benefit rate (CBR) at 24 weeks was seen in 5 patients out of 8 evaluable patients. Most common adverse events (AEs) were diarrhea (72.7%, no grade ≥ 3) and asthenia (27.3%, no grade ≥3). Neutropenia grade 4 was seen in a heavily treated patient with previous episodes on other therapies. Abemaciclib may result an effective and safe treatment option in MBC patients previously treated with palbociclib or ribociclib. Further prospective studies to confirm this hypothesis are required.

Randomized Phase II Study of Two Doses of Pixantrone in Patients with Metastatic Breast Cancer (NCCTG N1031, Alliance).

BackgroundAnthracycline use in metastatic breast cancer (MBC) is hindered by cumulative exposure limits and risk of cardiotoxicity. Pixantrone, a novel aza-anthracenedione with structural similarities to mitoxantrone and anthracyclines, is theorized to exhibit less cardiotoxicity, mainly due to lack of iron binding. We conducted a randomized phase II study to evaluate the efficacy and safety of 2 dosing schedules of pixantrone in patients with refractory HER2-negative MBC.MethodsIntravenous pixantrone was administered at 180 mg/m2 every 3 weeks (group A) versus 85 mg/m2 on days 1, 8, and 15 of a 28-day cycle (group B). Primary endpoint was objective response rate (ORR) and secondary endpoints included progression-free survival (PFS), median 6-month PFS, overall survival (OS), safety, quality of life, and serial assessment of circulating tumor cells. A 20% ORR was targeted as sufficient for further testing of pixantrone in this patient population.ResultsForty-five patients were evaluable, with 2 confirmed partial responses in group A and 1 in group B. The trial was terminated due to insufficient activity. Overall median PFS and OS were 2.8 (95% confidence interval [CI]: 2.0-4.1) and 16.8 (95% CI: 8.9-21.6) months, respectively. Notable overall grade 3-4 adverse events were the following: neutrophil count decrease (62%), fatigue (16%), and decrease in ejection fraction (EF) (4%).ConclusionPixantrone has insufficient activity in the second- and third-line MBC setting. It appears, however, to have limited cardiotoxicity. (ClinicalTrials.gov ID: NCT01086605).

EVALUATING THE TREATMENT RESULTS OF GEMCITABINE IN ANTHRACYLINE-AND TAXANE-PRETREATED RECURRENT OR METASTATIC BREAST CANCER

Abstract: Background: Gemcitabine monotherapy has been widely used in pretreated recurrent or metastatic breast cancer. This study aimed to evaluate the efficacy of this regimen. Method: Retrospective study of 41 anthracyline-and taxane-refractory recurrent or metastatic breast cancer patients in National Cancer Hospital from December 2016 to December 2020. Results: Of all patients, 73.2% had more than two sites of metastasis. 70.7% had elevated CA 15-3 level. Mean number of cycles was 7.2 (range 2-22). Disease control rate was 71.7%. Overall response rate was 34.1% (complete response, 12.2%; partial response 21.9%). Subgroup of Her2/neu amplification had significantly higher response rate (46.2% vs 13.3%). Median progression free survival was 6.1 months. Neutropenia was the most common adverse event, most of which was in grade 1 (36.6%) or grade 2 (7.3%). Conclusion: Gemcitabine monotherapy is effective and safe in anthracycline- and taxane- refractory recurrent or metastatic breast cancer patients Key words: gemcitabine, recurrent or metastatic breast cancer.

Abstract P1-17-01: Response of persistent metastatic ER+/Her2- breast cancer treated with fulvestrant plus enzalutamide

Abstract Background: The clinical implications of the androgen receptor (AR), particularly in the context of aromatase inhibitor (AI) refractory metastatic breast cancer (MBC), are unclear. While AR is associated with more indolent primary tumors, in the absence of low estradiol/blocked ER, AR can exert a pro-survival signal. Thus, in a phase II trial of Fulvestrant (Fulv) plus Enzalutamide (Enza) in ER+/Her2- MBC (NCT02953860) we analyzed serial biopsies pre- and post-treatment. Methods: Eligible patients were women with ECOG 0-2, ER+/Her2- MBC. Fulv at 500 mg IM days 1, 15, 29 and every 4 weeks thereafter and Enzaat 160 mg po daily on a continual basis were administered. Biopsies were required at study entry and at ~4 weeks on therapy. The clinical benefit rate at 24 weeks (CBR24) was the primary endpoint for efficacy. We performed mutational analysis using a modified Archer VariantPlex Solid Tumor Assay to detect mutations in ESR1 exon 8 and 67 other gene hotspots. We examined estrogen, progesterone, androgen and glucocorticoid receptor protein by IHC and multiplex for immune cells and PD-L1. Frozen cores were utilized to perform reverse phase protein array (RPPA) based protein pathway activation analysis of over 150 proteins from LCM-enriched tumor in baseline and post-treatment metastatic biopsies. Comparisons of Responders (progression free survival (PFS) equal to or longer than 24 weeks) and Non-Responders were performed using moderated t-tests on log2 transformed data. Results: 32 patients were eligible, median age was 61 years (46-87), and 90.6% had visceral disease with an average of 4 prior non-hormonal therapies and 3 prior hormonal agents (including 37.5% with prior Fulv). PFS >24 weeks was observed in ~22% of patients treated with Fulv plus Enza, including 42% of those who had prior Fulv. When stratified by both AR and ER protein levels, median time to progression was 59 days (95% CI: 55 to Inf) when both targets were high (greater than or equal to 10%), but only 14 days (95% CI: 13 to Inf) when both were less than 10%. Metastases with ESR1 mutations in the ligand binding domain had significantly higher levels of ER and PR protein than those with wild type ESR1 (p<0.05), while AR did not significantly differ. ER significantly decreased following 5 weeks post Fulv plus Enza in a paired t-test (p<0.003). ESR1 mutation positive metastases had significantly more T helper cells, T regulatory cells and macrophages than those with wild type ESR1. In contrast, those with TP53 or PIK3CA mutations had higher CD8+ T cells, but also increased T regulatory cells compared to those WT for these genes. PD-L1 increased with treatment in all patients by paired t test (p<0.03). RPPA analysis indicated that activation of mTOR pathway proteins was associated with non-response to Fulv plus Enza and patients with PIK3CA and or PTEN mutated disease had a shorter progression free survival time following treatment, with the hazard of disease progression for participants with PIK3CA or PTEN mutated disease being 2.27 times (95% CI: 0.94 to 5.46) than without these mutations (p=0.068). Conclusions: PFS >24 weeks was observed in 22% of patients treated with Fulv plus Enza, including 42% who had prior Fulv treatment, suggesting contribution of the anti-androgen. Response was significantly better when metastases were >10% for ER and AR. Poor response to Fulv plus Enza was significantly associated with mTOR pathway activation and patients with PIK3CA and or PTEN mutated metastases had a significantly shorter PFS. Mutation status also affected hormone receptor expression and immune infiltrates. The increase in PD-L1 protein following treatment with Fulv plus Enza warrants further pre-clinical investigation into whether the addition of anti-androgen can enhance efficacy of checkpoint inhibitor therapy in ER+ metastatic disease resistant to standard endocrine therapy approaches. Citation Format: Jennifer Richer, Nicole Spoelstra, Alyse Winchester, Julia Wulfkuhlue, Rosa Gallagher, Sharon Sams, Gregory Vidal, Peter Kabos, Jennifer Diamond, Elena Shagisultanova, Anosheh Afghahi, Jose Mayordomo, Tessa McSpadded, Gloria Crawford, Virginia Borges, Dexiang Gao, Emanuel Petricoin, Anthony Elias. Response of persistent metastatic ER+/Her2- breast cancer treated with fulvestrant plus enzalutamide [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-17-01.

Abstract P2-14-04: Updated data from FUTURE-C-PLUS: Combination of famitinib with camrelizumab plus nab-paclitaxel as first-line treatment for advanced, immunomodulatory triple-negative breast cancer, an open-label, single-arm, phase 2 trial

Abstract Background Camrelizumab and nab-paclitaxel demonstrated promising anti-tumour activity in refractory metastatic immunomodulatory triple-negative breast cancer (TNBC) in FUTURE trial. Anti-angiogenic agents have been reported to facilitate immune infiltration. Famitinib is a tyrosine kinase inhibitor targeting VEGFR-2, PDGFR and c-kit. The FUTURE-C-PLUS trial (NCT04129996) which added famitinib to camrelizumab and nab-paclitaxel is a single-arm, phase 2 trial evaluating this novel triplet combinatorial strategy in patients with advanced immunomodulatory TNBC. Study design and the primary endpoint ORR has been reported previously (Zhi-ming Shao, et al. ASCO 2021, Abstract 1007). Here, we reported the updated results of this trial. Method Briefly, this study enrolled women aged 18-70 years, with previously untreated, histologically confirmed, unresectable, locally advanced, recurrent or metastatic immunomodulatory TNBC. Immunomodulatory TNBC was defined as CD8 expression on at least 10% of cells using immunohistochemistry analysis. Eligible patients received the triple therapy. Study design has been reported previously in ASCO 2021. Results Between Oct 2019 and Oct 2020, 48 patients were enrolled and treated. 39 (81.3%, 95% CI 70.2-92.3) patients had a confirmed objective response which has been reported in ASCO 2021. At this updating data cutoff (June 30, 2021), the median progression-free survival was 11.9 months (95% CI, 7.3-16.5) with the median follow-up was 14.0 months. While overall survival data were not mature yet, a promising overall survival rate was observed at 12 months (84•2%, 95% CI 73.4-95.0) and 18 months (73.6%, 95% CI 52.0-95.2). In the 39 responders, median duration of response was also not mature. The disease control rate was 95.8% (46/48). The most common treatment-related grade 3 or 4 adverse events were neutropenia (16 [33.3%]), anemia (5 [10.4%]), febrile neutropenia (5 [10.4%]), and thrombocytopenia (4 [8.3%]). No treatment-related deaths were reported. Conclusions These data, combined with those from our previous reports, provide further evidence for the triplet combination of famitinib, camrelizumab and nab-paclitaxel as an active therapy in advanced Immunomodulatory TNBC. To our knowledge, this is the best objective response rate reached in first-line treatment of advanced TNBC. A randomized controlled FUTURE-Super trial (NCT04395989) is keeping recruiting patients to further validate those findings. Citation Format: Li Chen, Yi-Zhou Jiang, Songyang Wu, Jiong Wu, Genhong Di, Guangyu Liu, Keda Yu, Lei Fan, Junjie Li, Yifeng Hou, Zhen Hu, Canming Chen, Xiaoyan Huang, Ayong Cao, Xin Hu, Shen Zhao, Xiaoyan Ma, Xiaoyu Zhu, Jianjun Zou, Wentao Yang, Zhonghua Wang, Zhi-ming Shao. Updated data from FUTURE-C-PLUS: Combination of famitinib with camrelizumab plus nab-paclitaxel as first-line treatment for advanced, immunomodulatory triple-negative breast cancer, an open-label, single-arm, phase 2 trial [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-14-04.

Multi‐omic molecular profiling guide’s efficacious treatment selection in refractory metastatic breast cancer: a prospective phase II clinical trial

This prospective phase II clinical trial (Side Out 2) explored the clinical benefits of treatment selection informed by multi‐omic molecular profiling (MoMP) in refractory metastatic breast cancers (MBCs). Core needle biopsies were collected from 32 patients with MBC at trial enrollment. Patients had received an average of 3.94 previous lines of treatment in the metastatic setting before enrollment in this study. Samples underwent MoMP, including exome sequencing, RNA sequencing (RNA‐Seq), immunohistochemistry, and quantitative protein pathway activation mapping by Reverse Phase Protein Microarray (RPPA). Clinical benefit was assessed using the previously published growth modulation index (GMI) under the hypothesis that MoMP‐selected therapy would warrant further investigation for GMI ≥ 1.3 in ≥ 35% of the patients. Of the 32 patients enrolled, 29 received treatment based on their MoMP and 25 met the follow‐up criteria established by the trial protocol. Molecular information was delivered to the tumor board in a median time frame of 14 days (11–22 days), and targetable alterations for commercially available agents were found in 23/25 patients (92%). Of the 25 patients, 14 (56%) reached GMI ≥ 1.3. A high level of DNA topoisomerase I (TOPO1) led to the selection of irinotecan‐based treatments in 48% (12/25) of the patients. A pooled analysis suggested clinical benefit in patients with high TOPO1 expression receiving irinotecan‐based regimens (GMI ≥ 1.3 in 66.7% of cases). These results confirmed previous observations that MoMP increases the frequency of identifiable actionable alterations (92% of patients). The MoMP proposed allows the identification of biomarkers that are frequently expressed in MBCs and the evaluation of their role as predictors of response to commercially available agents. Lastly, this study confirmed the role of MoMP for informing treatment selection in refractory MBC patients: more than half of the enrolled patients reached a GMI ≥ 1.3 even after multiple lines of previous therapies for metastatic disease.

Sacituzumab Govitecan for Treatment of Refractory Triple-Negative Metastatic Breast Cancer.

Sacituzumab govitecan was initially approved in April 2020 under accelerated approval for the treatment of patients with metastatic triplenegative breast cancer who received at least two prior therapies for metastatic disease. A confirmatory phase III trial evaluating sacituzumab govitecan vs. chemotherapy of the provider's choice was published in April 2021. Based on this trial, the FDA granted sacituzumab govitecan full regulatory approval. This antibody-drug conjugate is composed of a monoclonal antibody targeted at Trop-2 and contains the active metabolite of irinotecan, SN-38, as a cytotoxic side moiety. In a phase III clinical trial, sacituzumab govitecan demonstrated a median progression-free survival of 5.7 months vs. 1.7 months with chemotherapy. It is now an additional option for patients with unresectable locally advanced or metastatic triple-negative breast cancer who have received two or more prior systemic therapies, at least one of them for metastatic disease.