HBM HOLDINGS-B(02142): The design of the first phase 1 clinical study on MESOC2 in humans will be presented at the 2025 ASCO annual meeting.

HBM HOLDINGS-B (02142) announced that Pfizer, a partner of the group, will present the first-in-class antibody-drug conjugate (ADC) MesoC2 (HBM9033/PF-08052666) targeting mesothelin (MSLN) at the 2025 American Society of Clinical Oncology (ASCO) annual meeting. MesoC2 was originally developed by the company's wholly-owned subsidiary Nonna Biotech (Suzhou) Co., Ltd. (Nonna Biotech) using its proprietary Harbour Mice platform and integrated ADC platform, and was licensed to Pfizer in December 2023 through a global licensing agreement. The ADC is currently undergoing a phase 1 open-label study in patients with various late-stage solid tumors. Pfizer will present the following clinical research information at this year's ASCO annual meeting: A phase 1 study evaluating the safety and tolerability of the antibody-drug conjugate (ADC) MesoC2 (PF-08052666) in patients with late-stage solid tumors Abstract number: TPS3163; Presentation format: Poster; Poster number: 475a; Session name: Poster Presentation - Emerging Therapies - Molecularly Targeted Agents and Tumor Biology; Meeting date: June 2, 2025 Key points of the presentation: MesoC2 is an ADC consisting of a human IgG1 antibody targeting MSLN conjugated with a cleavable tripeptide linker and a topoisomerase 1 inhibitor (TOP1) payload (average antibody-drug ratio of 8). MesoC2 demonstrated significant anti-tumor efficacy in in vitro experiments and xenograft models, as well as acceptable safety features in cynomolgus monkeys. This phase 1 trial (NCT06466187) will be conducted with dose escalation, dose optimization, and cohort expansion, evaluating the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary efficacy of MesoC2 in up to 365 patients based on RECIST v1.1 criteria.