Concurrent predictors of an immune responsive tumor microenvironment within tumor mutational burden-high breast cancer.

Background: Data supporting high tumor mutational burden (TMB-H) as a lone biomarker for an immune-responsive tumor microenvironment (TME) in metastatic breast cancer (MBC) are weak, yet tumor agnostic approval in TMB-H advanced tumors provides immune checkpoint inhibition (ICI) as a clinical option. We evaluated concurrent predictors of immune-responsive and non-responsive TME within MBC. Methods: Tumor samples from patients with MBC (N=5621) were analyzed by next-generation sequencing of DNA (592-gene panel or whole exome) and RNA (whole transcriptome) at Caris Life Sciences (Phoenix, AZ). TMB-H threshold was set to ≥ 10 muts/Mb. PDL-1 was evaluated using SP142 antibody. Gene expression profiling and RNA deconvolution were used to estimate immune and stromal cell population abundance in the TME, and transcriptomic signature of immunotherapy response (T cell-inflamed score). Results: 461 (8.2%) TMB-H MBC samples were identified. Consistent with prior studies, TMB-H tumors exhibited significant dMMR/MSI-H enrichment (7 vs. 0%, p<0.0001) and PD-L1+ expression (36 vs. 28%, p<0.05) compared to TMB-L. Across all samples, T cell-inflamed scores were weakly correlated with TMB. TMB-H was not associated with significantly increased immune responsive cell types (CD8+ T-cells, NK cells, or B cells) or immune response gene signatures (e.g. antigen presentation), yet positive trends were observed, while immunosuppressive fibroblasts were significantly decreased in TMB-H tumors (0.84-fold change compared to TMB-L, P<0.05). HR+/HER2- breast cancer was the only subtype in which TMB-H tumors exhibited increased T cell-inflamed scores vs. TMB-L. Concurrent PD-L1+ or dMMR/MSI-H with TMB-H was associated with high T cell-inflamed scores in both HR+/HER2- and TNBC. Among several associated biomarkers, B2M mutations and CD274 amplifications were positively associated with T-cell inflamed scores in TMB-H tumors; CDH1 and ERBB2 mutations were negatively associated. Conclusion: High TMB alone does not strongly correlate with immune infiltrate or immune-related gene signatures in MBC. TMB-H predicts T-cell inflamed signature compared to TMB-L in HR+/HER2- tumors only. Along with MSI-H and PD-L1+, several biomarkers, including B2M mutation and CD274 amplification, may help predict ICI benefit amongst TMB-H tumors. Co-occurring biomarkers within TMB-H breast cancer warrant evaluation in larger cohorts for response or resistance to ICI to develop composite predictive biomarkers in MBC.

Investigating potential immune mechanisms of trilaciclib administered prior to chemotherapy in patients with metastatic triple-negative breast cancer.

PURPOSE: In a phase II trial in patients with metastatic triple-negative breast cancer (mTNBC; NCT02978716), administering trilaciclib prior to gemcitabine plus carboplatin (GCb) enhanced T-cell activation and improved overall survival versus GCb alone. The survival benefit was more pronounced in patients with higher immune-related gene expression. We assessed immune cell subsets and used molecular profiling to further elucidate effects on antitumor immunity. METHODS: Patients with mTNBC and ≤ 2 prior chemotherapy regimens for locally recurrent TNBC or mTNBC were randomized 1:1:1 to GCb on days 1 and 8, trilaciclib prior to GCb on days 1 and 8, or trilaciclib alone on days 1 and 8, and prior to GCb on days 2 and 9. Gene expression, immune cell populations, and Tumor Inflammation Signature (TIS) scores were assessed in baseline tumor samples, with flow cytometric analysis and intracellular and surface cytokine staining used to assess immune cell populations and function. RESULTS: After two cycles, the trilaciclib plus GCb group (n = 68) had fewer total T cells and significantly fewer CD8+ T cells and myeloid-derived suppressor cells compared with baseline, with enhanced T-cell effector function versus GCb alone. No significant differences were observed in patients who received GCb alone (n = 34). Of 58 patients in the trilaciclib plus GCb group with antitumor response data, 27 had an objective response. RNA sequencing revealed a trend toward higher baseline TIS scores among responders versus non­responders. CONCLUSION: The results suggest that administering trilaciclib prior to GCb may modulate the composition and response of immune cell subsets to TNBC.

Targeted Therapies and the Evolving Standard of Care for Triple-Negative and Germline BRCA1/2-Mutated Breast Cancers in the High-Risk, Early-Stage Setting.

PURPOSE: Immune checkpoint inhibitors (ICIs) and poly (ADP-ribose) polymerase (PARP) inhibitors have transformed the treatment landscape of metastatic triple-negative breast cancer (TNBC). Trial results have demonstrated the clinical benefit of these targeted agents in the advanced TNBC setting and have led to their evaluation in the treatment of high-risk, early-stage TNBC and BRCA-mutated breast cancer. We provide a summary of the results that have led to the establishment of the ICI pembrolizumab and the PARP inhibitor olaparib as new standards of care. METHODS: Using PubMed, we searched for original articles published in English between 2017 and 2022. Search terms included triple-negative breast cancer, adjuvant, neoadjuvant, immunotherapy, and PARP inhibitors. RESULTS: Two targeted therapies have been approved by the US Food and Drug Administration for the treatment of TNBC and BRCA-mutated breast cancers in the high-risk, early-stage setting on the basis of clinical trial results demonstrating improved clinical outcomes. For high-risk, early-stage TNBC, pembrolizumab was approved as neoadjuvant therapy in combination with chemotherapy and as a single agent for continued treatment after surgery; this approval was based on results of the KEYNOTE-522 trial. Olaparib was approved for the adjuvant treatment of patients with high-risk, early-stage human epidermal growth factor receptor type 2 (HER2)-negative breast cancer with germline BRCA1/2 mutations who have been previously treated with neoadjuvant or adjuvant chemotherapy on the basis of the OlympiA trial results. CONCLUSION: Clinical trial results demonstrate the pronounced clinical benefits of pembrolizumab combined with chemotherapy for high-risk, early-stage TNBC and adjuvant olaparib for high-risk, early-stage HER2-negative BRCA1/2-mutated breast cancer.

Association Between Biomarkers and Clinical Outcomes of Pembrolizumab Monotherapy in Patients With Metastatic Triple-Negative Breast Cancer: KEYNOTE-086 Exploratory Analysis.

PURPOSE: In the two-cohort phase II KEYNOTE-086 study (ClinicalTrials.gov identifier: NCT02447003), first-line and second-line or later pembrolizumab monotherapy demonstrated antitumor activity in metastatic triple-negative breast cancer (mTNBC; N = 254). This exploratory analysis evaluates the association between prespecified molecular biomarkers and clinical outcomes. METHODS: Cohort A enrolled patients with disease progression after one or more systemic therapies for metastatic disease irrespective of PD-L1 status; Cohort B enrolled patients with previously untreated PD-L1-positive (combined positive score [CPS] ≥ 1) metastatic disease. The association between the following biomarkers as continuous variables and clinical outcomes (objective response rate [ORR], progression-free survival [PFS], and overall survival [OS]) was evaluated: PD-L1 CPS (immunohistochemistry), cluster of differentiation 8 (CD8; immunohistochemistry), stromal tumor-infiltrating lymphocyte (sTIL; hematoxylin and eosin staining), tumor mutational burden (TMB; whole-exome sequencing [WES]), homologous recombination deficiency-loss of heterozygosity, mutational signature 3 (WES), mutational signature 2 (apolipoprotein B mRNA editing catalytic polypeptide-like; WES), T-cell-inflamed gene expression profile (TcellinfGEP; RNA sequencing), and 10 non-TcellinfGEP signatures (RNA sequencing); Wald test P values were calculated, and significance was prespecified at α = 0.05. RESULTS: In the combined cohorts (A and B), PD-L1 (P = .040), CD8 (P < .001), sTILs (P = .012), TMB (P = .007), and TcellinfGEP (P = .011) were significantly associated with ORR; CD8 (P < .001), TMB (P = .034), Signature 3 (P = .009), and TcellinfGEP (P = .002) with PFS; and CD8 (P < .001), sTILs (P = .004), TMB (P = .025), and TcellinfGEP (P = .001) with OS. None of the non-TcellinfGEP signatures were associated with outcomes of pembrolizumab after adjusting for the TcellinfGEP. CONCLUSION: In this exploratory biomarker analysis from KEYNOTE-086, baseline tumor PD-L1, CD8, sTILs, TMB, and TcellinfGEP were associated with improved clinical outcomes of pembrolizumab and may help identify patients with mTNBC who are most likely to respond to pembrolizumab monotherapy.

COVID-19 vaccine uptake trends in SARS-CoV-2 previously infected cancer patients.

Purpose: Cancer patients are at high risk of developing severe illness from SARS-CoV-2 infection, but risk is lowered with receipt of COVID-19 vaccine. COVID-19 vaccination uptake among previously infected cancer patients may be influenced by an assumption of natural immunity, predicted weak immune response, or concerns about vaccine safety. The objective of this study was to evaluate COVID-19 vaccine uptake trends in cancer patients previously infected with SARS-CoV-2. Materials and Methods: Medical records of 579 sequential cancer patients undergoing active treatment at Levine Cancer Institute who tested positive for COVID-19 between January 2020 and January 2021 were evaluated. Patients who died prior to vaccine eligibility were excluded from the analysis. Demographic, clinical, and COVID-19 related characteristics were analyzed to identify prognostic factors for COVID-19 vaccine uptake as this information could be important for health policy design for future pandemics. Results: Eighty-one patients died prior to the availability of COVID-19 vaccines. The acceptance rate of COVID-19 vaccination among 498 previously infected cancer patients was 54.6%. Of the patients with known vaccination dates, 76.8% received their first vaccine by April 17th, 2021. As of November 30, 2021, 23.7.% of eligible patients were boosted. In univariate models, older age, female sex, higher income, solid tumor cancer type, and hormone therapy were significantly associated with higher vaccine uptake, while Hispanic/Latino ethnicity was significantly associated with lower vaccine uptake. In a multivariable model, age (OR 1.18, 95% CI 1.10-1.28; p < 0.001), female sex (OR 1.80, 95% CI 1.22-2.66; p = 0.003), and higher income (OR 1.11, 95% CI 1.01-1.22; p = 0.032), were predictive of COVID-19 vaccine uptake. Conclusions: Overall, vaccine uptake was low among our cohort of previously infected cancer patients. Older age, female sex, and higher income were the only variables associated with COVID-19 vaccine uptake within this vulnerable patient population.

Incidence and severity of anaphylaxis and hypersensitivity in trials of intravenous pertuzumab plus trastuzumab or the fixed-dose combination of pertuzumab and trastuzumab for subcutaneous injection for HER2-positive breast cancer.

AIM: To characterise risk of anaphylaxis/hypersensitivity with intravenous pertuzumab plus trastuzumab (PH IV), the fixed-dose combination of pertuzumab and trastuzumab for subcutaneous injection (PH FDC SC) or concomitant chemotherapy to support potential administration of PH FDC SC by healthcare professionals outside clinics. METHODS: A cumulative search for anaphylaxis/hypersensitivity (Roche Standard Adverse Event Group Terms) was performed for all pivotal trials cited in the current EMA P IV/PH FDC SC summaries of product characteristics: MBC: NCT00567190, NCT02402712; EBC: NCT01358877, NCT00545688, NCT00976989, NCT02132949, NCT03493854 and NCT03674112. Occurrence, incidence and severity of events were analysed and a time-trend analysis (by cycle) was performed. RESULTS: This analysis includes 4772 patients who received PH IV and/or PH FDC SC. Incidence of all-grade (grade ≥3) anaphylaxis/hypersensitivity events: 3-11% (≤2%) for PH IV MBC trials; 1-13% (0-3%) for PH IV EBC trials; and 2-3% (<1%; not related to PH FDC SC) for PH FDC SC EBC trials. Discontinuations due to anaphylaxis/hypersensitivity were rare for PH IV (generally <1% except two arms of TRYPHAENA: 1% and 3%); no discontinuations of PH FDC SC have been recorded so far. Time-trend analysis showed that most events were reported during the first 6-8 cycles with concurrent chemotherapy, with a decrease in later cycles (except MetaPHER). CONCLUSION: PH IV and PH FDC SC were well tolerated, with few grade ≥3 anaphylaxis/hypersensitivity events reported with PH IV and no grade ≥3 related events with PH FDC SC. Most events occurred during chemotherapy.

Trilaciclib prior to gemcitabine plus carboplatin for metastatic triple-negative breast cancer: phase III PRESERVE 2.

Triple-negative breast cancer (TNBC) is an aggressive malignancy for which cytotoxic chemotherapy remains the backbone of treatment. Trilaciclib is an intravenous cyclin-dependent kinase 4/6 inhibitor that induces transient cell cycle arrest of hematopoietic stem and progenitor cells and immune cells during chemotherapy exposure, protecting them from chemotherapy-induced damage and enhancing immune activity. Administration of trilaciclib prior to gemcitabine plus carboplatin (GCb) significantly improved overall survival (OS) compared with GCb alone in an open-label phase II trial in patients with metastatic TNBC, potentially through protection and direct activation of immune function. The randomized, double-blind, placebo-controlled, phase III PRESERVE 2 trial will evaluate the efficacy and safety of trilaciclib administered prior to GCb in patients with locally advanced unresectable or metastatic TNBC. Clinical Trial Registration: NCT04799249 (ClinicalTrials.gov).

Molecular characterization of ESR1 variants in breast cancer.

PURPOSE: Estrogen receptor 1 (ESR1) mutations and fusions typically arise in patients with hormone receptor-positive breast cancer after aromatase inhibitor therapy, whereby ESR1 is constitutively activated in a ligand-independent manner. These variants can impact treatment response. Herein, we characterize ESR1 variants among molecularly profiled advanced breast cancers. METHODS: DNA next-generation sequencing (592-gene panel) data from 9860 breast cancer samples were retrospectively reviewed. Gene fusions were detected using the ArcherDx fusion assay or whole transcriptome sequencing (n = 344 and n = 4305, respectively). Statistical analyses included Chi-square and Fisher's exact tests. RESULTS: An ESR1 ligand-binding domain (LBD) mutation was detected in 8.6% of tumors evaluated and a pathogenic ESR1 fusion was detected in 1.6%. Most ESR1 LBD mutations/fusions were from estrogen receptor (ER)-positive samples (20.1% and 4.9%, respectively). The most common ESR1 LBD mutations included D538G (3.3%), Y537S (2.3%), and E380Q (1.1%) mutations. Among biopsy sites, ESR1 LBD mutations were most observed in liver metastases. Pathogenic ESR1 fusions were identified in 76 samples (1.6%) with 40 unique fusion partners. Evaluating co-alterations, ESR1 variant (mutation/fusion) samples more frequently expressed androgen receptor (78.0% vs 58.6, P < 0.0001) and less frequently immune checkpoint proteins than ESR1 wild-type (PD-1 20.0% vs 53.4, P < 0.05; immune cell PD-L1 10.0% vs 30.2, P < 0.0001). CONCLUSION: We have described one of the largest series of ESR1 fusions reported. ESR1 LBD mutations were commonly identified in ER-positive disease. Limited data exists regarding the clinical impact of ESR1 fusions, which could be an area for future therapeutic exploration.

Does Residual Cancer Burden Predict Local Recurrence After Neoadjuvant Chemotherapy?

BACKGROUND: The extent of residual disease after neoadjuvant chemotherapy (NAC) can be quantified by the Residual Cancer Burden (RCB), a prognostic tool used to estimate survival outcomes in breast cancer. This study investigated the association between RCB and locoregional recurrence (LRR). METHODS: The study reviewed 532 women with breast cancer who underwent NAC between 2010 and 2016. Relapse in the ipsilateral breast, skin/subcutis at the surgical site, chest wall, pectoralis, or regional lymph nodes defined an LRR. The LRR cumulative incidence (LRCI) was estimated using the Fine and Gray competing-risks model, with death and distant recurrence defined as competing events. The association of LRCI with prognostic variables was evaluated. RESULTS: Overall, 5.5% of the patients experienced an LRR after a median follow-up period of 65 months. The 5-year LRCI rates by RCB were as follows: RCB-0 (0.9%), RCB-1 (3.2%), RCB-2 (6.0%), and RCB-3 (12.9%). In the univariable analysis, LRCI varied significantly by RCB (p = 0.010). The multivariable analysis showed a significant association of LRCI with increasing RCB, and the patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) phenotype were at lower risk for LRR than those with HER2+ and triple-negative cancers (p < 0.032). The patients with RCB-3 were at a higher risk for local relapse than those with RCB-0 (hazard ratio, 13.78; confidence interval, 2.25-84.45; p = 0.04). Type of operation (p = 0.04) and use of adjuvant radiation (p = 0.046) were statistically significant in the multivariable model. CONCLUSIONS: The study results demonstrate a significant association between LRCI and increasing RCB, although distant recurrence is a substantial driver of disease outcomes. Future prospective studies should examine the role of RCB in clinical decisions regarding indications for adjuvant therapy.

A phase 1 and pharmacodynamic study of chronically-dosed, single-agent veliparib (ABT-888) in patients with BRCA1- or BRCA2-mutated cancer or platinum-refractory ovarian or triple-negative breast cancer.

PURPOSE: BRCA1 or BRCA2 mutated cancers (BRCAmut) have intrinsic sensitivity to PARP inhibitors due to deficiency in homologous recombination-mediated DNA repair. There are similarities between BRCAmut and BRCAwt ovarian and basal-like breast cancers. This phase I study determined the recommended phase II dose (RP2D) and preliminary efficacy of the PARP inhibitor, veliparib (ABT-888), in these patients. PATIENTS AND METHODS: Patients (n = 98) were dosed with veliparib 50-500 mg twice daily (BID). The BRCAmut cohort (n = 70) contained predominantly ovarian (53%) and breast (23%) cancers; the BRCAwt cohort (n = 28) consisted primarily of breast cancer (86%). The MTD, DLT, adverse events, PK, PD, and clinical response were assessed. RESULTS: DLTs were grade 3 nausea/vomiting at 400 mg BID in a BRCAmut carrier, grade 2 seizure at 400 mg BID in a patient with BRCAwt cancer, and grade 2 seizure at 500 mg BID in a BRCAmut carrier. Common toxicities included nausea (65%), fatigue (45%), and lymphopenia (38%). Grade 3/4 toxicities were rare (highest lymphopenia at 15%). Overall response rate (ORR) was 23% (95% CI 13-35%) in BRCAmut overall, and 37% (95% CI 21-55%) at 400 mg BID and above. In BRCAwt, ORR was 8% (95% CI 1-26%), and clinical benefit rate was 16% (95% CI 4-36%), reflecting prolonged stable disease in some patients. PK was linear with dose and was correlated with response and nausea. CONCLUSIONS: Continuous veliparib is safe and tolerable. The RP2D was 400 mg BID. There is evidence of clinical activity of veliparib in patients with BRCAmut and BRCAwt cancers.

A phase I study of veliparib with cyclophosphamide and veliparib combined with doxorubicin and cyclophosphamide in advanced malignancies.

PURPOSE: Veliparib (V), an oral poly(ADP-ribose) polymerase (PARP) inhibitor, potentiates effects of alkylating agents and topoisomerase inhibitors in preclinical tumor models. We conducted a phase I trial of V with iv cyclophosphamide (C) and V plus iv doxorubicin (A) and C. METHODS: Objectives were to establish the maximum tolerated dose (MTD) of the combinations, characterize V pharmacokinetics (PK) in the presence and absence of C, measure PAR in peripheral blood mononuclear cells (PBMCs) and γH2AX in circulating tumor cells (CTCs). In Group 1, dose escalations of V from 10 to 50 mg every 12 h Days 1-4 plus C 450 to 750 mg/m2 Day 3 in 21-day cycles were evaluated. In Group 2, V doses ranged from 50 to 150 mg every 12 h Days 1-4 with AC (60/600 mg/m2) Day 3 in 21-day cycles. In Group 3, patients received AC Day 1 plus V Days 1-7, and in Group 4, AC Day 1 plus V Days 1-14 was given in 21-day cycles to evaluate effects on γH2AX foci. RESULTS: Eighty patients were enrolled. MTD was not reached for V and C. MTD for V and AC was V 100 mg every 12 h Days 1-4 with AC (60/600 mg/m2) Day 3 every 21 days. V PK appears to be dose-dependent and has no effect on the PK of C. Overall, neutropenia and anemia were the most common adverse events. Objective response in V and AC treated groups was 22% (11/49). Overall clinical benefit rate was 31% (25/80). PAR decreased in PBMCs. Percentage of γH2AX-positive CTCs increased after treatment with V and AC. CONCLUSION: V and AC can be safely combined. Activity was observed in patients with metastatic breast cancer.

Combination of HER2-targeted agents with immune checkpoint inhibitors in the treatment of HER2-positive breast cancer.

INTRODUCTION: Human epidermal growth factor receptor 2 (HER2)-positive breast cancers account for approximately 15 to 20% of breast cancer diagnoses. Historically, HER2-positive breast cancers had been associated with poorer prognosis. The addition of HER2-targeted agents to treatment regimens has significantly improved outcomes for patients with HER2-positive breast cancer. Despite this, relapses continue to occur in about 20% of patients. Newer therapeutic strategies are needed. The role of immunotherapy in the treatment of HER2-positive breast cancer is currently under clinical investigation. AREAS COVERED: This article will focus on the clinical trial data evaluating immune checkpoint inhibitors, including pembrolizumab, atezolizumab, avelumab, durvalumab, and nivolumab in the treatment of HER2-positive breast cancer. EXPERT OPINION: The incorporation of immunotherapy in the treatment of HER2-positive breast cancer is a reasonable strategy. Clinical trials of checkpoint inhibitors with HER2-targeted agents show clinical activity in HER2-positive breast cancer tumors that are programmed cell death-ligand 1 (PD-L1) positive and also when used as an earlier line of therapy in the metastatic setting. Treatment of HER2-positive breast cancer with immunotherapy and HER2-targeted agents warrants continued clinical investigation.

Trilaciclib Prior to Chemotherapy in Patients with Metastatic Triple-Negative Breast Cancer: Final Efficacy and Subgroup Analysis from a Randomized Phase II Study.

PURPOSE: We report final antitumor efficacy results from a phase II study of trilaciclib, an intravenous cyclin-dependent kinase 4/6 (CDK4/6) inhibitor, administered prior to gemcitabine plus carboplatin (GCb) in patients with metastatic triple-negative breast cancer (NCT02978716). PATIENTS AND METHODS: Patients were randomized (1:1:1) to group 1 [GCb (days 1, 8); n = 34], group 2 [trilaciclib prior to GCb (days 1, 8); n = 33], or group 3 [trilaciclib (days 1, 8) and trilaciclib prior to GCb (days 2, 9); n = 35]. Subgroup analyses were performed according to CDK4/6 dependence, level of programmed death-ligand 1 (PD-L1) expression, and RNA-based immune signatures using proportional hazards regression. T-cell receptor (TCR) ß CDR3 regions were amplified and sequenced to identify, quantify, and compare the abundance of each unique TCRß CDR3 at baseline and on treatment. RESULTS: Median overall survival (OS) was 12.6 months in group 1, not reached in group 2 (HR = 0.31; P = 0.0016), 17.8 months in group 3 (HR = 0.40; P = 0.0004), and 19.8 months in groups 2 and 3 combined (HR = 0.37; P < 0.0001). Efficacy outcomes were comparable regardless of cancer CDK4/6 dependence status and immune signatures. Administering trilaciclib prior to GCb prolonged OS irrespective of PD-L1 status but had greater benefit in the PD-L1-positive population. T-cell activation was enhanced in patients receiving trilaciclib. CONCLUSIONS: Administering trilaciclib prior to GCb enhanced antitumor efficacy, with significant improvements in OS. Efficacy outcomes in immunologic subgroups and enhancements in T-cell activation suggest these improvements may be mediated via immunologic mechanisms.

Final results of the double-blind placebo-controlled randomized phase 2 LOTUS trial of first-line ipatasertib plus paclitaxel for inoperable locally advanced/metastatic triple-negative breast cancer.

PURPOSE: In LOTUS (NCT02162719), adding the oral AKT inhibitor ipatasertib to first-line paclitaxel for locally advanced/metastatic triple-negative breast cancer (aTNBC) improved progression-free survival (PFS; primary endpoint), with an enhanced effect in patients with PIK3CA/AKT1/PTEN-altered tumors (FoundationOne next-generation sequencing [NGS] assay). We report final overall survival (OS) results. METHODS: Eligible patients had measurable previously untreated aTNBC. Patients were stratified by prior (neo)adjuvant therapy, chemotherapy-free interval, and tumor immunohistochemistry PTEN status, and were randomized 1:1 to paclitaxel 80 mg/m2 (days 1, 8, 15) plus ipatasertib 400 mg or placebo (days 1-21) every 28 days until disease progression or unacceptable toxicity. OS (intent-to-treat [ITT], immunohistochemistry PTEN-low, and PI3K/AKT pathway-activated [NGS PIK3CA/AKT1/PTEN-altered] populations) was a secondary endpoint. RESULTS: Median follow-up was 19.0 versus 16.0 months in the ipatasertib-paclitaxel versus placebo-paclitaxel arms, respectively. In the ITT population (n = 124), median OS was numerically longer with ipatasertib-paclitaxel than placebo-paclitaxel (hazard ratio 0.80, 95% CI 0.50-1.28; median 25.8 vs 16.9 months, respectively; 1-year OS 83% vs 68%). Likewise, median OS favored ipatasertib-paclitaxel in the PTEN-low (n = 48; 23.1 vs 15.8 months; hazard ratio 0.83) and PIK3CA/AKT1/PTEN-altered (n = 42; 25.8 vs 22.1 months; hazard ratio 1.13) subgroups. The ipatasertib-paclitaxel safety profile was unchanged. CONCLUSIONS: Final OS results show a numerical trend favoring ipatasertib-paclitaxel and median OS exceeding 2 years with ipatasertib-paclitaxel. Overall, results are consistent with the reported PFS benefit; interpretation within biomarker-defined subgroups is complicated by small sample sizes and TNBC heterogeneity.

Checkpoint inhibitor therapy for metastatic triple-negative breast cancer.

Immunotherapy has become a mainstay of cancer treatment in many malignancies, though its application in breast cancer remains limited. Of the breast cancer subtypes, triple-negative breast cancers (TNBCs) are characterized by immune activation and infiltration and more commonly express biomarkers associated with response to immunotherapy. Checkpoint inhibitor therapy has shown promising activity in metastatic TNBC. In 2019, the US FDA granted accelerated approval of atezolizumab, a programmed death-ligand 1 (PD-L1) inhibitor, in combination with nab-paclitaxel for unresectable locally advanced or metastatic PD-L1-positive TNBC, based on the results of the phase III IMpassion130 trial. In 2020, the FDA also granted accelerated approval of pembrolizumab, a PD-1 inhibitor, in combination with chemotherapy for locally recurrent unresectable and metastatic PD-L1-positive TNBC, based on results of the phase III KEYNOTE-355 trial. Additional combination strategies are being explored in the treatment of metastatic TNBC, with the goal of augmenting antitumor activity. In this review, the clinical development of checkpoint inhibitors in the treatment of metastatic TNBC will be discussed, including clinical outcomes with monotherapy and combination therapy regimens, biomarkers that may predict for benefit, and future directions in the field.

Combination of Pertuzumab and Trastuzumab in the Treatment of HER2-Positive Early Breast Cancer: A Review of the Emerging Clinical Data.

Human epidermal growth factor receptor type 2 (HER2) is a relevant and effective target in breast cancer. The development of monoclonal antibodies against HER2 has revolutionized the treatment of HER2-positive breast cancer. The humanized monoclonal antibody, trastuzumab, was the first in its class to be widely adopted. It was initially studied in the metastatic setting and then in the treatment of early-stage disease, demonstrating significant improvement in overall survival in both settings. The addition of pertuzumab further improved upon results achieved with trastuzumab and chemotherapy, specifically extending overall survival in patients with metastatic disease, lessening the risk of recurrence when used in the adjuvant setting, and improving pathologic complete response rate when utilized in the neoadjuvant setting. In this article, we review the studies that support the use of HER2-directed monoclonal antibodies in early-stage breast cancer both in the adjuvant and neoadjuvant settings and focus on the success of dual HER2-targeted therapy achieved with the combination of trastuzumab and pertuzumab. A newer way to administer these agents, specifically the subcutaneous formulation of pertuzumab and trastuzumab with recombinant human hyaluronidase, will also be discussed.

First-in-Human, Phase 1 Dose-Escalation Study of Biparatopic Anti-HER2 Antibody-Drug Conjugate MEDI4276 in Patients with HER2-positive Advanced Breast or Gastric Cancer.

MEDI4276 is a biparatopic tetravalent antibody targeting two nonoverlapping epitopes in subdomains 2 and 4 of the HER2 ecto-domain, with site-specific conjugation to a tubulysin-based microtubule inhibitor payload. MEDI4276 demonstrates enhanced cellular internalization and cytolysis of HER2-positive tumor cells in vitro This was a first-in-human, dose-escalation clinical trial in patients with HER2-positive advanced or metastatic breast cancer or gastric cancer. MEDI4276 doses escalated from 0.05 to 0.9 mg/kg (60- to 90-minute intravenous infusion every 3 weeks). Primary endpoints were safety and tolerability; secondary endpoints included antitumor activity (objective response, progression-free survival, and overall survival), pharmacokinetics, and immunogenicity. Forty-seven patients (median age 59 years; median of seven prior treatment regimens) were treated. The maximum tolerated dose was exceeded at 0.9 mg/kg with two patients experiencing dose-limiting toxicities (DLTs) of grade 3 liver function test (LFT) increases, one of whom also had grade 3 diarrhea, which resolved. Two additional patients reported DLTs of grade 3 LFT increases at lower doses (0.4 and 0.6 mg/kg). The most common (all grade) drug-related adverse events (AEs) were nausea (59.6%), fatigue (44.7%), aspartate aminotransferase (AST) increased (42.6%), and vomiting (38.3%). The most common grade 3/4 drug-related AE was AST increased (21.3%). Five patients had drug-related AEs leading to treatment discontinuation. In the as-treated population, there was one complete response (0.5 mg/kg; breast cancer), and two partial responses (0.6 and 0.75 mg/kg; breast cancer)-all had prior trastuzumab, pertuzumab, and ado-trastuzumab emtansine (T-DM1). MEDI4276 has demonstrable clinical activity but displays intolerable toxicity at doses >0.3 mg/kg.

The evolving role of immune checkpoint inhibitors in the treatment of triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer for which chemotherapy had been the only active treatment option once metastatic disease developed. Immune checkpoint inhibitors (ICIs) are now available to treat patients with advanced TNBC who have programmed cell death ligand 1 (PD-L1)-positive tumors; these agents have been shown to improve clinical outcomes. Additionally, long-term disease control can be achieved in a subset of patients. Continued investigations of ICIs and optimal combinations with chemotherapy and targeted agents to enhance the immune response are ongoing, along with studies aimed at identifying the patients most likely to benefit. For early-stage TNBC, the data to date on administering ICI-based combination therapies in the neoadjuvant setting are compelling and suggest that the benefit from immunotherapy does not depend on PD-L1 expression. This review will discuss the clinical trial data on ICIs as monotherapy and in combination with chemotherapy in the treatment of patients with metastatic and early-stage TNBC.