Relevance of Platinum-free Interval and BRCA Reversion Mutations for Veliparib Monotherapy after Progression on Carboplatin/Paclitaxel for gBRCA Advanced Breast Cancer (BROCADE3 Crossover)

Case report: Emerging BRCA mutation confers benefit from olaparib after chemotherapy intolerance in advanced triple-negative breast cancer

Key Clinical Message

In a patient with metastatic breast cancer, an acquired BRCA mutation in the BRCA gene was detected, resulting in benefits from olaparib treatment. This underscores the importance of ongoing genetic phenotype testing after paclitaxel chemotherapy.

Abstract

Triple-negative breast cancer (TNBC) is associated with a poor prognosis and elevated mortality risk. BRCA mutations are commonly regarded as prevalent mutations in TNBC patients, strongly associated with congenital familial heredity. Dynamic changes in mutation sites, however, are rarely reported. In this case report, we report a 59-year-old TNBC patient who developed pulmonary metastases post-chemoradiotherapy. No BRCA mutations were detected through NGS. After 7.6 months of nab-paclitaxel treatment, the patient experienced progression of lung metastases, and BRCA mutations were detected through NGS testing. Subsequent administration of olaparib resulted in a reduction in lung metastasis, demonstrating significant therapeutic efficacy. This case underscores the infrequent occurrence of treatment-induced BRCA mutations and emphasizes the significance of dynamic NGS genetic testing for real-time assessment of a patient's mutational status.

Small-scale mutations are infrequent as mechanisms of resistance in post-PARP inhibitor tumour samples in high grade serous ovarian cancer

While the introduction of poly-(ADP)-ribose polymerase (PARP) inhibitors in homologous recombination DNA repair (HR) deficient high grade serous ovarian, fallopian tube and primary peritoneal cancers (HGSC) has improved patient survival, resistance to PARP inhibitors frequently occurs. Preclinical and translational studies have identified multiple mechanisms of resistance; here we examined tumour samples collected from 26 women following treatment with PARP inhibitors as part of standard of care or their enrolment in clinical trials. Twenty-one had a germline or somatic BRCA1/2 mutation. We performed targeted sequencing of 63 genes involved in DNA repair processes or implicated in ovarian cancer resistance. We found that just three individuals had a small-scale mutation as a definitive resistance mechanism detected, having reversion mutations, while six had potential mechanisms of resistance detected, with alterations related to BRCA1 function and mutations in SHLD2. This study indicates that mutations in genes related to DNA repair are detected in a minority of HGSC patients as genetic mechanisms of resistance. Future research into resistance in HGSC should focus on copy number, transcriptional and epigenetic aberrations, and the contribution of the tumour microenvironment.

Enhancing the anti-tumor response by combining DNA damage repair inhibitors in the treatment of solid tumors

The anti-cancer efficacy of anti-malignancy therapies is related to DNA damage. However, DNA damage-response mechanisms can repair DNA damage, failing anti-tumor therapy. The resistance to chemotherapy, radiotherapy, and immunotherapy remains a clinical challenge. Thus, new strategies to overcome these therapeutic resistance mechanisms are needed. DNA damage repair inhibitors (DDRis) continue to be investigated, with polyadenosine diphosphate ribose polymerase inhibitors being the most studied inhibitors. Evidence of their clinical benefits and therapeutic potential in preclinical studies is growing. In addition to their potential as a monotherapy, DDRis may play an important synergistic role with other anti-cancer therapies or in reversing acquired treatment resistance. Here we review the impact of DDRis on solid tumors and the potential value of combinations of different treatment modalities with DDRis for solid tumors.

Emerging Intrinsic Therapeutic Targets for Metastatic Breast Cancer

Breast cancer is now the most common cancer worldwide, and it is also the main cause of cancer-related death in women. Survival rates for female breast cancer have significantly improved due to early diagnosis and better treatment. Nevertheless, for patients with advanced or metastatic breast cancer, the survival rate is still low, reflecting a need for the development of new therapies. Mechanistic insights into metastatic breast cancer have provided excellent opportunities for developing novel therapeutic strategies. Although high-throughput approaches have identified several therapeutic targets in metastatic disease, some subtypes such as triple-negative breast cancer do not yet have an apparent tumor-specific receptor or pathway to target. Therefore, exploring new druggable targets in metastatic disease is a high clinical priority. In this review, we summarize the emerging intrinsic therapeutic targets for metastatic breast cancer, including cyclin D-dependent kinases CDK4 and CDK6, the PI3K/AKT/mTOR pathway, the insulin/IGF1R pathway, the EGFR/HER family, the JAK/STAT pathway, poly(ADP-ribose) polymerases (PARP), TROP-2, Src kinases, histone modification enzymes, activated growth factor receptors, androgen receptors, breast cancer stem cells, matrix metalloproteinases, and immune checkpoint proteins. We also review the latest development in breast cancer immunotherapy. Drugs that target these molecules/pathways are either already FDA-approved or currently being tested in clinical trials.

Efficacy and safety of PARP inhibitors in the treatment of BRCA-mutated breast cancer: an updated systematic review and meta-analysis of randomized controlled trials

INTRODUCTION

Poly-ADP-ribose polymerase inhibitors (PARPis) have emerged as a new class of therapeutic agents for breast cancer patients with breast cancer susceptibility gene (BRCA) mutations. However, the efficacy and toxicity of PARPis have not been clearly established.

METHODS

This study comprehensively evaluated the efficacy and safety of PARPis in patients with BRCA-mutated breast cancer. Online databases were systematically searched, and six clinical trials were included. The primary endpoint of efficacy was progression-free survival (PFS), whereas the secondary endpoints were overall survival (OS) and objective response rate (ORR). Additionally, we assessed the safety of PARPis.

RESULTS

The results of the meta-analysis showed that PARPis can effectively improve the PFS and OS in patients compared with the control group. The pooled HR (PARPi vs control groups) was 0.63 (95% CI, 0.55 - 0.73) and 0.83 (95% CI, 0.73 to -0.95) for PFS and OS, respectively. In safety, PARPis demonstrated controllable adverse reactions. There were no significant differences in overall AEs or grade ≥3 AEs between the PARP inhibitor and control arms.

CONCLUSIONS

Our results confirm the efficacy and safety of PARPis in patients with BRCA-mutated breast cancer, and more specifically clarify the efficacy of PARPis alone or in combination with other chemotherapy drugs. [Figure: see text].

All HER2-negative breast cancer patients need gBRCA testing: cost-effectiveness and clinical benefits

BACKGROUND

The OlympiA trial demonstrated the benefits of adjuvant usage of olaparib for high-risk patients with human epidermal growth factor receptor 2 (HER2)-negative breast cancer (BC) and germline BRCA (gBRCA) mutation. This provoked thoughts on the clinical criteria of gBRCA testing. This study aims to estimate the costs and benefits of gBRCA testing and adjuvant olaparib therapy for patients with triple-negative breast cancer (TNBC) and hormone-receptor (HR)-positive and HER2-negative BC in China and the United States of America (USA).

METHODS

We used a Markov chain decision tree analytic model to compare three gBRCA screening policies in China and the USA: (1) no gBRCA testing; (2) selected gBRCA testing and (3) universal gBRCA testing for nonmetastatic TNBC and HR-positive HER2-negative BC patients. We modelled the benefit of systemic therapy and risk-reducing surgeries among patients identified with pathogenic or likely pathogenic variants (PVs) in BRCA1 and BRCA2.

RESULTS

Changing from the selected gBRCA testing to the universal gBRCA testing in TNBC patients is cost-effective, with the incremental cost-effectiveness ratios (ICERs) being 10991.1 and 56518.2 USD/QALY in China and the USA, respectively. Expanding universal gBRCA testing to HR-positive HER2-negative BC and TNBC patients has ICERs of 2023.3 and 16611.1 USD/QALY in China and the USA, respectively.

DISCUSSION

By performing gBRCA testing on all HER2-negative BC patients, adjuvant olaparib can be offered to high-risk patients with a PV in BRCA1 or BRCA2. These patients are also candidates for risk-reducing surgeries, an important aspect of their survivorship care, and these interventions can improve survival outcomes. With the willingness-to-pay thresholds being 31,500.0 and 100,000.0 USD per QALY gained in China and the USA, respectively, universal gBRCA testing is likely cost-effective for all HER2-negative BC patients. This simplified criterion of gBRCA testing for BC is recommended for adoption by current guidelines in China and the USA.

Current Systemic Treatments for the Hereditary Cancer Syndromes: Drug Development in Light of Genomic Defects

Advances in the genetic basis of different tumors have led to identification of tumor vulnerabilities that can be turn into targeted therapies. In this regard, PARP inhibitors cause synthetic lethality with tumors harboring BRCA1 or BRCA2 genetic alterations. On the other hand, tumors with microsatellite instability, either due to germline or sporadic alterations, are candidates for immune checkpoint inhibitors. Finally, patients with von Hippel-Lindau disease who carry a germline alteration in the VHL gene may benefit form belzutifan, a hypoxia-inducible factor 2 alpha inhibitor. Overall, research on the underlying pathological mechanisms of these tumors has provided new therapeutic opportunities that might be expanded to other sporadic tumors with similar biology.

Development of Next-Generation Poly(ADP-Ribose) Polymerase 1-Selective Inhibitors

ABSTRACT

Poly(ADP-ribose) polymerase (PARP) inhibitors have transformed the therapeutic landscape for advanced ovarian cancer and expanded treatment options for other tumor types, including breast, pancreas, and prostate cancer. Yet, despite the success of PARP inhibitors in our current therapeutic armamentarium, not all patients benefit because of primary resistance, whereas different acquired resistance mechanisms can lead to disease progression on therapy. In addition, the toxicity profile of PARP inhibitors, primarily myelosuppression, has led to adverse events in a proportion of patients as monotherapy, and has limited the use of PARP inhibitors for certain rational combination strategies, such as chemotherapy and targeted therapy regimens. Currently approved PARP inhibitors are essentially equipotent against PARP1 and PARP2 enzymes. In this review, we describe the development of next-generation PARP1-selective inhibitors that have entered phase I clinical trials. These inhibitors have demonstrated increased PARP1 inhibitory potency and exquisitely high PARP1 selectivity in preclinical studies-features that may lead to improved clinical efficacy and a wider therapeutic window. First-in-human clinical trials seeking to establish the safety, tolerability, and recommended phase II dose, as well as antitumor activity of these novel agents, have commenced. If successful, this next-generation of PARP1-selective agents promises to build on the succeses of current PARP inhibitor treatment paradigms in cancer medicine.

Expanding the Use of PARP Inhibitors as Monotherapy and in Combination in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, and is known to be associated with a poor prognosis and limited therapeutic options. Poly (ADP-ribose) polymerase inhibitors (PARPi) are targeted therapeutics that have demonstrated efficacy as monotherapy in metastatic BRCA-mutant (BRCAMUT) TNBC patients. Improved efficacy of PARPi has been demonstrated in BRCAMUT breast cancer patients who have either received fewer lines of chemotherapy or in chemotherapy-naïve patients in the metastatic, adjuvant, and neoadjuvant settings. Moreover, recent trials in smaller cohorts have identified anti-tumor activity of PARPi in TNBC patients, regardless of BRCA-mutation status. While there have been concerns regarding the efficacy and toxicity of the use of PARPi in combination with chemotherapy, these challenges can be mitigated with careful attention to PARPi dosing strategies. To better identify a patient subpopulation that will best respond to PARPi, several genomic biomarkers of homologous recombination deficiency have been tested. However, gene expression signatures associated with PARPi response can integrate different pathways in addition to homologous recombination deficiency and can be implemented in the clinic more readily. Taken together, PARPi have great potential for use in TNBC patients beyond BRCAMUT status, both as a single-agent and in combination.

Veliparib monotherapy following carboplatin/paclitaxel plus veliparib combination therapy in patients with germline BRCA-associated advanced breast cancer: results of exploratory analyses from the phase III BROCADE3 trial

BACKGROUND

In the BROCADE3 trial (NCT02163694), addition of the poly(ADP-ribose) polymerase (PARP) inhibitor, veliparib, to carboplatin/paclitaxel improved progression-free survival (PFS) (hazard ratio [HR] 0.71, 95% confidence interval 0.57-0.88; P=0.002) in patients with advanced HER2-negative, germline BRCA1/2-mutated breast cancer. A subset of patients discontinued both carboplatin and paclitaxel prior to progression and continued on veliparib/placebo maintenance monotherapy until progression. Analyses in this patient subgroup are reported.

PATIENTS AND METHODS

Patients were randomized 2:1 to veliparib plus carboplatin/paclitaxel or placebo plus carboplatin/paclitaxel. Veliparib (120 mg twice daily [BID]) or placebo was given on days -2 to 5, carboplatin (AUC 6 mg/mL) on day 1, and paclitaxel (80 mg/m²) on days 1, 8, and 15 of 21-day cycles. Patients who discontinued both carboplatin and paclitaxel prior to progression received blinded study drug monotherapy at an increased dose of 300-400 mg BID continuously. PFS was the primary endpoint. Exploratory analyses were performed in the subgroup of patients who received blinded study drug as monotherapy. A time-varying Cox model including data from all patients was also used to evaluate treatment effect in the combination and monotherapy phases.

RESULTS

136 of 337 patients randomized to veliparib plus carboplatin/paclitaxel and 58/172 patients randomized to placebo plus carboplatin/paclitaxel discontinued both carboplatin and paclitaxel prior to progression and continued on blinded veliparib or placebo monotherapy. In this blinded monotherapy subgroup, investigator-assessed median PFS from randomization was 25.7 months with veliparib versus 14.6 months with placebo. HRs from a time-varying Cox model favored veliparib during both combination therapy and monotherapy. Any-grade adverse events (AEs) occurring in the monotherapy phase were primarily gastrointestinal. The most common grade ≥3 AEs were neutropenia and anemia (4% each with veliparib; 5% and 2%, respectively, with placebo).

CONCLUSIONS

Veliparib maintenance monotherapy had a tolerable safety profile and may extend PFS following combination chemotherapy.