GSK has already moved on from its decision to drop a cancer asset on Tuesday by snagging a late-stage liver disease candidate for a hefty $1.2 billion upfront.
That drug in question is efimosfermin, Boston Pharmaceuticals’ lead asset. The asset has already passed midstage tests and is now a phase 3-ready therapy to help stop the progression of steatotic liver disease (SLD), a condition where fat builds up in the liver. If left untreated, this can lead to increasing levels of liver damage through scarring and cirrhosis.
GSK will pay $1.2 billion upfront for the drug while also putting a further $800 million on the table should efimosfermin hit certain milestones.
The therapy, which was once owned by Novartis, works as a once-monthly fibroblast growth factor 21 (FGF21) analog therapeutic and is being assessed in metabolic dysfunction-associated steatohepatitis (MASH), including cirrhosis, with GSK eyeing future work in alcohol-related liver disease (ALD), both of which are forms of SLD.
The British Big Pharma already has an earlier-stage liver disease asset in GSK’990, a siRNA therapeutic being evaluated for subsets of patients with SLD. GSK said in its Wednesday morning release that there is potential to combine efimosfermin with GSK’990 in future studies.
In November 2024, Boston posted phase 2 data that showed that after 24 weeks, 14 of the 31 patients who received 300 mg of efimosfermin had a one-stage or greater improvement in fibrosis without worsening of MASH, compared to seven of the 34 people on placebo. The difference between the proportion of people who met the criteria, 45.2% and 20.6%, was statistically significant.
The drug is similar to Akero Therapeutics’ efruxifermin and 89bio’s pegozafermin, both of which work as FGF21 analogues. While efruxifermin and pegozafermin are given weekly, Boston has modified efimosfermin's fusion protein to extend its half-life so the therapy can be administered monthly.
Liver disease is becoming a major area of research. After years of weak data and safety issues across multiple pharma studies, last year’s approval of Madrigal Pharmaceuticals' Rezdiffra in MASH marked a new hope for a market potentially worth tens of billions of dollars.
GSK’s figures show that ALD affects around 26 million patients globally, and, together with MASH, typically caused by longstanding obesity, is the leading reason for liver transplant in the U.S.
“The FGF21 class has shown some of the most exciting data in MASH including first-in-disease evidence of cirrhosis reversal, and efimosfermin has the potential to define a new standard-of-care with its monthly dosing and tolerability profile,” Tony Wood, Ph.D., chief scientific officer at GSK, said in the release.
“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.”
This morning's asset deal comes a day after GSK dropped work on its iTeos Therapeutics-partnered TIGIT antibody belrestotug amid poor trial data.