HUTCHMED Initiates Global Clinical Development of ATTC Candidate HMPL-A251 in Patients with Solid Tumors

— First-in-human trial of candidate from the next-generation ATTC platform —

— Simultaneous China and global clinical development strategy to expedite development process —

HONG KONG and SHANGHAI and FLORHAM PARK, N.J., Dec. 17, 2025 (GLOBE NEWSWIRE) -- HUTCHMED (China) Limited (“HUTCHMED”) (Nasdaq/AIM:​HCM; HKEX:​13) today announces the initiation of its global Phase I clinical development program for HMPL-A251, a first-in-class PI3K/PIKK-HER2 Antibody-Targeted Therapy Conjugate (“ATTC”) comprising a highly selective and potent PI3K/PIKK inhibitor payload conjugated to a humanized anti-HER2 IgG1 antibody via a cleavable linker. Study sites are in the US and China. The first patient received the first dose on December 16, 2025, in China.

This first-in-human Phase I/IIa, open-label, multicenter clinical study evaluates HMPL-A251 monotherapy in adult patients with unresectable, advanced or metastatic HER2-expressing solid tumors. The study is divided into two parts, a Phase I dose escalation part and a Phase IIa dose expansion and optimization part. The primary outcome measures are to evaluate the safety and tolerability of HMPL-A251 and to determine the maximum tolerated dose (MTD) and/or recommended dose(s) for expansion (“RDE”) in the Phase I part, and to further evaluate safety and preliminary efficacy at RDEs and to determine the recommended dose for Phase II (RP2D) or Phase III (RP3D) in the Phase IIa part. Secondary outcome measures include preliminary antitumor activity, pharmacokinetic profile, and the immunogenicity of HMPL-A251. Additional details may be found at clinicaltrials.gov, using identifier NCT07228247.

HMPL-A251 is the first clinical-stage candidate derived from HUTCHMED’s next-generation ATTC platform. The first family of programs are based on a highly potent and selective PI3K/PIKK inhibitor payload. By conjugating this highly novel payload to an anti-HER2 antibody, the molecule is designed to deliver targeted pathway inhibition directly into HER2-expressing tumor cells, thereby potentially overcoming the systemic toxicity and narrow therapeutic index historically associated with PI3K/PIKK inhibitors. This approach aims to achieve deeper and more durable target inhibition while improving the overall tolerability profile.