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Abstract Background Pamiparib is an investigational PARP1/2 inhibitor that has demonstrated brain penetration and PARP–DNA complex trapping in preclinical studies. In the phase 1 dose-escalation/expansion study of pts with advanced solid tumors, pamiparib was generally well tolerated and showed preliminary antitumor activity. Here we report updated antitumor activity focused on the ovarian cancer cohort and safety data. Methods This is a two-stage dose-escalation/expansion study (NCT02361723). The dose-escalation study component established the pamiparib PK profile, and the recommended phase 2 dose (RP2D) of pamiparib administered orally 60 mg BID in pts with solid tumors. The dose-expansion component was conducted in pts with ovarian, breast, prostate, gastric, and small cell lung cancer. Results As of 1 January 2019, 97 pts (median age, 60 years; Eastern Cooperative Oncology Group performance status of 0, 1, or 2 [37%, 62%, and 1%, respectively]) were enrolled in the dose-escalation (n = 60) and dose-expansion (n = 37) components. Among the 97 enrolled pts, 48 pts (n = 30, ovarian pts) received 60 mg BID, the RP2D. Of 57 ovarian pts in the efficacy evaluable population (≥1 postbaseline tumor assessment), 22 (39%) achieved a confirmed objective response (complete response, n = 4; partial response, n = 18) per RECIST v1.1 criteria. Median duration of response was 12.3 months (range, 1.3–40.8). Biomarker data will be included in future analyses. In the safety population (n = 97), drug-related adverse events (AEs) in ≥ 10% of pts were nausea, fatigue, anemia, diarrhea, vomiting, and decreased appetite. The most common drug-related G3 (no G4 or G5) AEs were anemia (18.6%) and neutropenia (6.2%). AEs led to treatment discontinuation in 6.2% of pts. Four pts died due to disease progression with non-drug–related AEs. Pamiparib plasma exposure generally increased with increased dose, with a median t1/2 of ∼13 hours. Conclusions Pamiparib continues to be generally well tolerated and demonstrates antitumor activity in this update of an ongoing, phase 1 dose-escalation/expansion study in pts with advanced solid tumors. Clinical trial identification NCT02361723. Editorial acknowledgement Editorial/writing support was provided by Ira Mills, PhD, and Shannon Davis at Ashfield Healthcare Communications, Middletown, CT. Legal entity responsible for the study BeiGene. Funding BeiGene. Disclosure M. Voskoboynik: Honoraria (self): AstraZeneca; Honoraria (self): MSD Oncology; Travel / Accommodation / Expenses: Bristol-Myers Squibb. L. Mileshkin: Travel / Accommodation / Expenses, Beigene paid for flights and accommodation for me to attend and present at the ASCO STIC meeting Jan 2018: Beigene. M. Millward: Research grant / Funding (self), Per patient payments for clinical trials: Beigene; Advisory / Consultancy, Advisory Board for Immuno-Oncology: Bristol-Myers Squibb; Advisory / Consultancy, Advisory Board for Immuno-Oncology: Merck Sharp & Dohme; Advisory / Consultancy, Advisory Board for Immuno-Oncology: Roche; Advisory / Consultancy, Advisory Board for Immuno-Oncology: AstraZeneca. K. Zhang: Full / Part-time employment: Beigene. M. Zhang: Full / Part-time employment: Beigene. S. Mu: Full / Part-time employment: Beigene. All other authors have declared no conflicts of interest.