ESMO Congress 2024 | OncologyPRO

Abstract 778P

Background

There is limited research on whether pts who have previously exposed to PARP inhibitors (PARPi) can be treated with PARPi again. Here we present a prospective, single-arm, phase II study and describe the efficacy and safety of pamiparib monotherapy as PARPi retreatment in patients with rOC (NCT05489926).

Methods

Patients with rOC of histological high-grade serous carcinoma and ≥2 prior lines of chemotherapy were enrolled and received pamiparib (60 mg po BID). All of them had received one prior PARPi therapy. The primary endpoint was clinical benefit rate ≥ 4 months (CBR_4m) assessed by investigators according to RECIST v1.1.

Results

By Apr 30, 2024, 15 pts with platinum-resistant (n=12) and platinum-sensitive (n=3) rOC were enrolled. 8 of 15 (53.3%) had known/suspected BRCA1/2 mutation. Median age was 57 yr (45-72), Median number of previous treatment lines was 3 (2-6). The median duration of prior PARPi therapy was 21 mo (11-46). After a median follow-up period of 13.9 mo (4.1-20.5), 2 pts (13.3%) achieved PR and 7 pts (46.7%) achieved SD, respectively. But the CBR_4m was 26.7% (4/15). According to BRCA status, the CBR_4m were 37.5% (3/8) and 14.3% (1/7) in the BRCAmut and BRCAwt pts, respectively. Median PFS was 2.8 mo (95%CI 2.1-4.9). Treatment-related adverse events (TRAE) occurred in 60% (9/15) pts. 26.7% (4/15) pts occurred Grade 3 AEs. Most frequent AEs were gastrointestinal and hematological toxicity.

Conclusions

Pamiparib monotherapy showed limited clinical efficacy in rOC pts who had used PARPi before. In PARPi after PARPi treatment strategy, PARPi monotherapy should be selected prudently.