Pralsetinib has been proven efficacious activity in a variety of solid tumors including medullary thyroid cancer (MTC) in the phase 1/2 global ARROW study (BLU-667-1101; NCT03037385). We assessed the safety and efficacy of pralsetinib in Chinese ad-vanced RET-mutant MTC patients. In the extension cohort of ARROW, adult patients with advanced MTC who had not received systemic therapy (except for cytotoxic chem-otherapy), treated with pralsetinib (400 mg once daily, orally). The primary endpoints were blinded independent central reviewed (BICR) objective response rate (ORR), and safety. Between October 9, 2019 and April 29, 2020, 34 patients were enrolled at 12 centers across China. Among them, 28 patients tested positive for RET mutations by central laboratory, and 26 of these with measurable disease at baseline per BICR were included in the analysis set for tumor response. As of April 12, 2021 (data cutoff), ORR was 73.1% (95% CI: 52.2-88.4). Median duration of response was not reached. The most common (≥15%) grade ≥3 treatment-related adverse events (TRAEs) in 28 patients with RET-mutant MTC were neutrophil count decreased (8/28, 28.6%), blood creatine phosphokinase increased (6/28, 21.4%), and lymphocyte count decreased (5/28, 17.9%). Serious TRAEs were reported by six patients (21.4%), with the most common event being pneumonia (3/28, 10.7%). No patient discontinued treatment or died from pralsetinib-related adverse events. Pralsetinib demonstrated broad, deep, and durable efficacy, a manageable and acceptable safety profile in Chinese patients with advanced RET-mutant MTC.