Pamiparib in combination with tislelizumab in patients with advanced solid tumours: results from the dose-expansion stage of a multicentre, open-label, phase I trial

Background: This study aimed to evaluate the antitumor efficacy, safety, and tolerability of pamiparib combined with tislelizumab in patients with previously treated advanced solid tumors.

Methods: Patients were enrolled in eight groups based on tumor type. All participants received pamiparib at 40 mg orally twice daily along with tislelizumab at 200 mg intravenously every three weeks. The primary endpoint was the objective response rate (ORR), assessed by investigators using the Response Evaluation Criteria in Solid Tumors version 1.1. Secondary endpoints included duration of response (DoR), safety, and tolerability.

Results: A total of 180 patients were enrolled. The overall ORR was 20.0% (ranging from 0% to 47.4% across study arms), with a median DoR of 17.1 months (95% confidence interval [CI]: 6.2, not estimable [NE]). The highest ORR was observed in the triple-negative breast cancer (TNBC) group (patients with BRCA1/2 mutations and/or homologous recombination deficiency), reporting an ORR of 47.4% and a median DoR of 17.1 months (95% CI: 3.0, NE). Treatment-emergent adverse events (TEAEs) of grade 3 or higher occurred in 61.7% of patients, with serious TEAEs reported in 50.0%.

Conclusions: The combination of pamiparib and tislelizumab demonstrated varying levels of antitumor activity in patients with advanced solid tumors, with the highest ORR observed in the TNBC group, and showed a manageable safety profile.