GSK (LSE/NYSE: GSK) has completed the acquisition of Canada-based 35Pharma Inc., a private clinical-stage biopharmaceutical company, for USD 950 million in cash. The transaction delivers HS235, a Phase I activin receptor signalling inhibitor for pulmonary hypertension (PH), into GSK's Respiratory, Immunology and Inflammation (RI&I) pipeline.

The deal is structured as a 100% equity acquisition with no disclosed milestone payments, royalty tiers, or contingent value rights. GSK assumes unrestricted global rights to all 35Pharma assets.

HS235 and activin receptor signalling

HS235 is a subcutaneously administered protein therapeutic that inhibits the activin receptor signalling pathway, a clinically validated target in PH. The molecule is engineered with enhanced receptor selectivity that reduces binding to bone morphogenetic proteins BMP9 and BMP10, ligands associated with adverse events including bleeding and telangiectasia observed with earlier-generation activin pathway inhibitors. By attenuating off-target BMP engagement, HS235 is designed to lower the risk of bleeding and pericardial effusion — dose-limiting toxicities that constrain use of current PAH agents in patients requiring concomitant anticoagulant or antiplatelet therapy.

Phase I pharmacokinetic and pharmacodynamic data from a completed healthy-subject study (NCT06714825) characterized HS235 in overweight and obese individuals. Two disease-focused Phase I trials are now enrolling: one in pulmonary arterial hypertension (PAH) (NCT07143448) and one in PH due to heart failure with preserved ejection fraction (PH-HFpEF) in obese patients (NCT07123779). Early clinical observations also indicated fat-selective weight loss, preservation of lean mass, and improved insulin sensitivity — metabolic signals with potential relevance given the high prevalence of obesity and insulin resistance across the broader PH population, though confirmation in controlled trials remains outstanding.

Strategic outlook

PH affects approximately 82 million people worldwide across multiple disease subtypes, with a five-year survival rate of approximately 50%. The global PH therapeutics market is forecast to reach USD 18 billion by 2032, with activin signalling inhibitors projected to represent approximately 50% of that total. Current approved therapies address vasodilatory and proliferative mechanisms but leave unmet need in fibrotic and inflammatory disease drivers, and the bleeding risk profile of existing activin pathway agents limits their use in anticoagulated patients.

HS235 extends GSK's RI&I portfolio into the vascular and fibrotic biology of cardiopulmonary disease, complementing existing pipeline programmes targeting inflammatory and fibrotic mechanisms in lung, liver, and kidney. The dual PAH and PH-HFpEF development strategy positions HS235 across two distinct PH subtypes with separate patient populations and prescriber bases, broadening the potential addressable market from the outset. The USD 950 million upfront, all-cash structure reflects the early clinical stage of HS235 and the absence of disclosed late-stage efficacy data, with GSK absorbing full development risk in exchange for unrestricted global ownership.

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