Company Announcements

CAMBRIDGE, Mass., ROTTERDAM, Netherlands and SHANGHAI, July 29, 2025 /PRNewswire/ -- Harbour BioMed (HKEX: 02142), a global biopharmaceutical company focused on the discovery and development of novel antibody therapeutics in immunology and oncology, today announced that it will present Phase II clinical data on its next-generation, fully human heavy-chain-only anti-CTLA-4 antibody, porustobart (HBM4003), in combination with tislelizumab, for the treatment of microsatellite stable (MSS) metastatic colorectal cancer (mCRC), at the ESMO Congress 2025, taking place October 17-21, 2025, in Berlin, Germany.

MSS mCRC remains a therapeutic challenge with limited response to immune checkpoint inhibitors. Preclinical evidence supports the synergistic antitumor activity of CTLA-4 blockade combined with PD-(L)1 inhibition in mouse models. In this multicenter, open-label, Phase II study (NCT05167071), heavily pretreated non-liver metastatic MSS mCRC patients were enrolled. Preliminary efficacy and safety data will be presented in a poster session during the ESMO Congress 2025.

Details of the poster presentation are as follows:

Title: Efficacy and Safety of HBM4003, an anti-CTLA-4 Antibody, Combined with Tislelizumab in MSS Metastatic Colorectal Cancer: A Multicenter, Phase II Study

Presentation Number: 807P

Speaker: Frank Zheng

All accepted abstracts will be published online on the ESMO website.

About Porustobart (HBM4003)

Porustobart (HBM4003) is a next-generation, fully human heavy-chain-only anti-CTLA-4 antibody discovered and developed using the HCAb Harbour Mice^® platform. It is also the first fully human heavy-chain-only antibody which entered clinical development globally. Compared with conventional CTLA-4 antibodies, porustobart has unique, favorable properties, including significant Treg cell depletion and optimized pharmacokinetics for improved safety. Additionally, by enhancing antibody-dependent cellular cytotoxicity (ADCC), porustobart increases the potential to selectively deplete intratumoral Treg cells, helping to overcome the efficacy and toxicity bottleneck of current CTLA-4 therapies. Harbour BioMed has implemented a global development plan for multiple types of solid tumors with an adaptive treatment design for porustobart. Positive efficacy and safety data have been observed in the monotherapy trials targeting advanced solid tumors, as well as in combination trials with PD-1 inhibitors for melanoma, CRC, NEN and HCC.

About Harbour BioMed

Harbour BioMed (HKEX: 02142) is a global biopharmaceutical company committed to the discovery and development of novel antibody therapeutics in immunology and oncology. The company is building a robust and differentiated pipeline through internal R&D capabilities, strategic global collaborations in co-discovery and co-development, and selective acquisitions.

Harbour BioMed's proprietary antibody technology platform, Harbour Mice^®, generates fully human monoclonal antibodies in both the conventional two heavy and two light chain (H2L2) format and the heavy chain-only (HCAb) format. Building upon HCAb antibodies, the HCAb-based immune cell engagers (HBICE^®) bispecific antibody technology enables tumor-killing effects that traditional combination therapies cannot achieve. Additionally, the HCAb-based bispecific immune cell antagonist (HBICA^TM) technology empowers the development of innovative biologics for immunological and inflammatory diseases. By integrating Harbour Mice^®, HBICE^®, and HBICA^TM with a single B-cell cloning platform, Harbour BioMed has built a highly efficient and distinctive antibody discovery engine for developing next-generation therapeutic antibodies. For more information, please visit www.harbourbiomed.com.

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SOURCE Harbour BioMed