Percheron Therapeutics Outlines Phase II Strategy for VISTA Inhibitor HMBD-002

Percheron Therapeutics Ltd has laid out an ambitious roadmap for its lead immuno-oncology asset, HMBD-002, as it moves from phase I completion into what management hopes will be a value-defining phase II program in 2026. The company positions HMBD-002 as a potential next-generation immune checkpoint inhibitor targeting VISTA — a relatively underexplored checkpoint that has proven difficult for others to drug.

With a market capitalisation of around $9 million and about $4.5 million in cash as of December 31, 2025, Percheron is operating leanly. The company argues that the enterprise value largely reflects the acquisition cost of HMBD-002 and imputes little to no value to future clinical data.

Percheron's thesis is that VISTA — V-domain immunoglobulin suppressor of T-cell activation — represents a complementary checkpoint that may overcome limitations of existing therapies. The company notes that VISTA is expressed across a wide range of tumour types and that high VISTA expression correlates with worse prognosis and resistance to PD-1 inhibition in certain settings. That biology underpins the strategy of combining HMBD-002 with pembrolizumab, as well as exploring its activity as a monotherapy.

Several companies have previously attempted to develop VISTA-targeting antibodies, but most programs were discontinued in early-phase development, with toxicity a central issue. HMBD-002 is built on an IgG4 scaffold rather than the IgG1 format used in most prior VISTA antibodies. IgG1 antibodies can activate antibody-dependent cellular cytotoxicity, potentially driving cytokine release and other immune-mediated toxicities. HMBD-002, by contrast, is designed to block VISTA signalling without necessarily depleting VISTA-positive cells, which may reduce the risk of severe immune-related toxicity.

The phase I study, conducted in the United States under an open IND with the FDA, enrolled 48 advanced cancer patients across monotherapy and pembrolizumab combination cohorts. The company reports a favourable safety profile in both settings. While early-phase oncology trials are not powered for efficacy, Percheron highlights several patients who achieved tumour shrinkage or prolonged stable disease despite being heavily pre-treated. In the dataset presented, patients included those with metastatic triple-negative breast cancer, non-small-cell lung cancer and head and neck squamous cell carcinoma. Some remained on therapy for extended periods, including one patient treated for 53 weeks.

Percheron's next step is an adaptive, multi-arm phase II trial expected to commence in calendar 2026. Rather than running entirely separate studies, the company plans a modular platform structure, in which each "arm" effectively resembles a standalone study in a defined tumour type but shares infrastructure and oversight. Each arm may initially enrol around 20–30 patients in an open-label exploratory stage, before potentially expanding into a randomised controlled format if early signals are promising.