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                                    <figcaption>The Phase I/IIa study will assess HMPL-A251 as a single agent in adults with unresectable, advanced, or metastatic HER2-expressing solid tumours. Credit: PeopleImages / Shutterstock.com.</figcaption>
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<p>Hutchmed has commenced its worldwide Phase I clinical development programme for a first-in-class phosphoinositide 3-kinase (PI3K) / phosphoinositide 3-kinase-related protein kinase (PIKK)-human epidermal growth factor receptor 2 (HER2) antibody-targeted therapy conjugate (ATTC), HMPL-A251.</p>



<p>Clinical trial sites for this study are located in China and the US. Recently, the first patient received a dose in China.</p>



<p>The first-in-human, Phase I/IIa, multi-centre, open-label clinical study will assess HMPL-A251 as a single agent in adults with unresectable, advanced, or metastatic HER2-expressing solid tumours.</p><div>
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        <img src="https://imageproxy.pbkrs.com/https://hubspot-pmisites.pantheonsite.io/techmonitor/wp-content/themes/goodlife-wp-B2B/assets/images/icons/Module.png?x-oss-process=image/auto-orient,1/interlace,1/resize,w_1440,h_1440/quality,q_95/format,jpg" alt="" width="130" height="183" original-src="https://imageproxy.pbkrs.com/https://hubspot-pmisites.pantheonsite.io/techmonitor/wp-content/themes/goodlife-wp-B2B/assets/images/icons/Module.png"/>
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<p>The clinical study is divided into two parts: a Phase I dose escalation stage and a Phase IIa dose expansion and optimisation stage.</p>



<p>Its main aims are to assess the tolerability and safety of HMPL-A251 and to identify the maximum tolerated dose (MTD) and/or recommended dose(s) for expansion (RDE) during Phase I.</p>



<p>In the Phase IIa segment, the study will further evaluate preliminary efficacy, safety at RDEs, and determine the recommended dose for Phase II (RP2D) or Phase III (RP3D).</p>



<p>Secondary outcome measures include evaluation of preliminary antitumour activity, the pharmacokinetic profile, and the immunogenicity of the therapy.</p>



<p>The initial group of programmes from this platform is based on a highly potent and selective PI3K/PIKK inhibitor payload.</p>



<p>By attaching this payload to an anti-HER2 antibody, the molecule is said to deliver targeted pathway inhibition directly into tumour cells which express HER2.</p>



<p>The company’s ATTC platform is described as a next-generation precision oncology approach, integrating monoclonal antibodies with small-molecule inhibitor payloads for dual mechanisms of action.</p>



<p>In March 2025, Hutchmed completed enrolment for its multi-centre Phase II trial of fanregratinib (HMPL-453), a treatment for intrahepatic cholangiocarcinoma (IHCC) patients with fibroblast growth factor receptor 2 fusion or rearrangement.</p>
                        
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<p>Hutchmed has launched a global Phase I clinical development program for HMPL-A251, a first-in-class PI3K/PIKK-HER2 antibody-targeted therapy conjugate. The study, conducted in China and the US, will assess the therapy in adults with advanced HER2-expressing tumors. The trial includes a Phase I dose escalation and a Phase IIa dose expansion stage, focusing on safety, tolerability, and efficacy. The ATTC platform integrates monoclonal antibodies with small-molecule inhibitors for precision oncology.</p>

Hutchmed begins Phase I HMPL-A251 clinical development programme