MUSTBIO announced that it presented research findings on its αPD-1/IL-2v bispecific fusion protein, MB5029, at the SITC 2024 conference held in Houston, Texas, from November 6 to 10.

MB5029 is a drug designed to bind selectively to the IL-2 receptor beta-gamma (IL-2Rβγ) without interacting with the IL-2 receptor alpha (IL-2Rα). Additionally, its affinity for IL-2Rγ has been reduced, preventing immune cell activation in PD-1 low-expressing peripheral blood while specifically activating immune cells in the PD-1 overexpressing tumor microenvironment (TME). This mechanism improves tolerability compared to existing IL-2 variant (IL-2v) drugs.

MUSTBIO has completed cell line development for MB5029 and is currently conducting GLP toxicology studies. The company aims to submit an Investigational New Drug application next year, with plans to enter clinical trials in the second half of 2025.

Key findings showed that MB5029 demonstrated tumor growth inhibition in immune checkpoint inhibitor (ICI)-resistant mouse tumor models, where PD-1 or PD-L1 checkpoint inhibitors had failed. The study also revealed increased tumor-infiltrating lymphocytes (TILs) in treated tumors. Pharmacokinetic (PK) and pharmacodynamic (PD) profiles were confirmed in mouse and monkey studies, with safety observed even at high doses.

In addition to MB5029, MUSTBIO is advancing its proprietary multi-antibody platform, "BICSTA," to enhance productivity and "STARKINE," a cytokine-based platform for improved selectivity. These platforms are being used to develop next-generation multi-specific antibodies.

The company is also working on tri-specific fusion protein immunotherapies, including an αPD-1/αVEGF-based candidate.