Chinese biopharmaceutical company Harbour BioMed (HKEX:02142) announced on Tuesday 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 in Berlin, Germany.

According to Harbour BioMed, MSS mCRC remains a therapeutic challenge with limited response to immune checkpoint inhibitors. Preclinical evidence supports the synergistic anti-tumour activity of CTLA-4 blockade combined with PD-(L)1 inhibition in mouse models. Heavily pretreated non-liver metastatic MSS mCRC patients were enrolled in this multicentre, open-label, Phase II study.

Preliminary efficacy and safety data will be presented in a poster session titled 'Efficacy and Safety of HBM4003, an anti-CTLA-4 Antibody, Combined with Tislelizumab in MSS Metastatic Colorectal Cancer: A Multicentre, Phase II Study'.

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

Porustobart (HBM4003) is a next-generation, fully human heavy-chain-only anti-CTLA-4 antibody discovered and developed using the HCAb Harbour Mice platform.