09:10 AM EDT, 05/14/2025 (MT Newswires) -- GSK (GSK) on Wednesday agreed to acquire Boston Pharmaceuticals' steatotic liver disease therapeutic candidate in a deal worth up to $2 billion in cash, as the UK drugmaker looks to expand its hepatology portfolio.

Under the terms, GSK will buy Boston Pharmaceuticals' subsidiary, BP Asset IX, for an upfront payment of $1.2 billion and up to $800 million in milestone payments. The transaction requires approval from regulators, the companies said in a joint statement.

The transaction will give the British firm access to efimosfermin alfa, a once-monthly fibroblast growth factor 21 analog therapeutic, which is currently in clinical development for the treatment of metabolic dysfunction-associated steatohepatitis and future development for alcohol-related liver disease.

The acquisition reflects GSK's research and development focus on the immune system and its aim to develop precision interventions to stop and reverse disease progression related to fibrosis and auto-inflammation, the company said. The acquisition of efimosfermin is expected to strengthen the company's hepatology pipeline for viral and steatotic drivers of fibrotic liver diseases.

"Efimosfermin has the potential to define a new standard-of-care with its monthly dosing and tolerability profile," GSK Chief Scientific Officer Tony Wood said in the statement. "Efimosfermin will significantly expand our hepatology pipeline and provide us the opportunity to develop a new potential best-in-class medicine with first launch expected in 2029."

Recent data from a phase two study of the product showed that it "significantly" reversed liver fibrosis and stopped its progression, according to the companies.

GSK will also pay milestone payments and tiered royalties for efimosfermin owed to Novartis Pharma, a subsidiary of Swiss pharmaceutical giant Novartis ( NVS ) . In 2020, Boston Pharmaceuticals agreed to license worldwide development and commercial rights for Novartis' ( NVS ) non-alcoholic steatohepatitis drug candidate.

"We are delighted that GSK, a global leader, recognised efimosfermin's potential to address a growing global public health concern and unmet medical need," Boston Pharmaceuticals Chair Elias Zerhouni said. "Together, we look forward to efimosfermin's ongoing journey to become a best-in-class treatment for patients with (steatotic liver disease)."