Harbour BioMed announced that the preclinical results of porustobart (HBM4003, or the HCAb 4003-2 in the research paper), a next-generation fully human heavy-chain antibody with a Treg depletion mechanism, were published in the Proceedings of the National Academy of Sciences (PNAS). PNAS is one of the world's most-cited and comprehensive multidisciplinary scientific journals. The Proceedings of the National Academy of Sciences (PNAS), a peer-reviewed journal of the National Academy of Sciences (NAS), is an authoritative source of high-impact, original research that broadly spans the biological, physical, and social sciences.

Porustobart (HBM4003) is a fully human anti-CTLA-4 heavy chain antibody (HCAb) generated in Harbour Mice®. It is the first fully human heavy chain antibody entered into clinical stage globally. By enhancing antibody-dependent cell cytotoxicity (ADCC) killing activity, porustobart demonstrates significantly improved depletion of high CTLA-4 expressing Treg cells in tumor tissues.

The potent anti-tumor efficacy and differentiated pharmacokinetics with durable pharmacodynamic effect present a favorable product profile. This novel and differentiated mechanism of action has the potential to improve efficacy while significantly reducing the toxicity of the drug in monotherapy and combination therapy.