An Exploratory Single-Arm Study of Maintenance Fluzoparib in Platinum-Sensitive, Advanced Triple-Negative Breast Cancer Patients With BRCA1/2 Mutation or Wild-Type BRCA
Breast cancer is the most common malignancy in women; approximately 5-10% are hereditary, with 14% of triple-negative breast cancers (TNBC) harboring BRCA mutations. BRCA1/2 are essential for homologous recombination repair of DNA double-strand breaks, whereas PARP mediates base-excision repair of single-strand breaks. PARP inhibitors (PARPi) exploit synthetic lethality to selectively eliminate BRCA-deficient tumor cells. Olaparib and talazoparib have demonstrated superior PFS and ORR versus chemotherapy in BRCA-mutated, HER2-negative advanced breast cancer, leading to FDA approval. In ovarian cancer, PARPi maintenance improves overall survival, with consistent benefits observed in Asian populations. The domestically developed PARPi fluzoparib, engineered with a trifluoromethyl moiety for enhanced stability and tissue penetration, showed in the phase III FABULOUS trial a median PFS of 6.7 vs 3.0 months and an ORR of 43.6% vs 23.3% compared with chemotherapy in gBRCA-mutated, HER2-negative breast cancer, with manageable safety. Data remain limited in Chinese patients and those with BRCA wild-type disease. This study aims to evaluate the efficacy and safety of fluzoparib maintenance monotherapy in advanced TNBC patients-either BRCA1/2-mutated or wild-type-who have derived clinical benefit from prior platinum-based therapy.
• Age 18-75 years (inclusive) at the time of informed consent.
• Histologically confirmed triple-negative breast cancer (TNBC; ER \<1%, PR \<1%, HER2-negative).
• Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1.
• Received ≥2 prior lines of systemic therapy, including a platinum-based regimen (single-agent or combination); must have achieved partial response (PR) or stable disease (SD) during or after that platinum-based treatment.
• Platinum-sensitive disease defined as: Objective response (complete or partial) or stable disease lasting ≥6 months while on platinum-based therapy, or Platinum-free interval (PFI) ≥6 months from the end of the last platinum-containing regimen to documented progression/relapse.
• Estimated life expectancy ≥3 months.
• At least one measurable lesion per RECIST 1.1 on CT/MRI; evidence of metastatic disease (soft-tissue and/or bone lesions) is required.
• Willing to provide archived tumour tissue (core biopsy or excision) or fresh biopsy/blood for biomarker analyses.
• Adequate organ function within 14 days (7 days for liver enzymes) before first dose:
• Absolute neutrophil count ≥1.5 × 10⁹/L Platelets ≥100 × 10⁹/L Haemoglobin ≥80 g/L Total bilirubin ≤1.5 × upper limit of normal (ULN) ALT \& AST ≤2.5 × ULN (≤5 × ULN if liver metastases present) Serum creatinine ≤1.25 × ULN and calculated creatinine clearance ≥60 mL/min
⁃ Toxicities from prior anti-cancer therapy resolved to Grade ≤1 per NCI-CTCAE v5.0 (except alopecia or other stable chronic toxicities deemed tolerable by the investigator).
⁃ Participants of reproductive potential and their partners must agree to use highly effective contraception from 30 days before the first dose until 120 days after the last dose of fluzoparib.
⁃ Signed written informed consent prior to any study-specific procedures.