GSK Acquires Boston Pharmaceuticals' Efimosfermin for Liver Disease in $2 Billion Deal
Key Insights
GSK has agreed to acquire Boston Pharmaceuticals' phase 3-ready liver disease candidate efimosfermin alfa for $1.2 billion upfront, with potential milestone payments bringing the total to $2 billion.
Efimosfermin, a once-monthly FGF21 (search) analog therapeutic, has demonstrated significant ability to reverse liver fibrosis and halt disease progression in patients with moderate-to-advanced MASH (search) in phase 2 trials.
The acquisition expands GSK's hepatology pipeline and offers potential combination therapy options with GSK's siRNA therapeutic GSK'990 (search), targeting steatotic liver disease (search) which affects approximately 5% of the global population.
GSK has announced the acquisition of Boston Pharmaceuticals' subsidiary BP Asset IX in a deal worth up to $2 billion, securing rights to efimosfermin alfa, a phase 3-ready investigational drug for steatotic liver disease (search) (SLD). The agreement includes $1.2 billion upfront and up to $800 million in success-based milestone payments.
Efimosfermin alfa is a novel fibroblast growth factor 21 (FGF21 (search)) analog therapeutic administered as a once-monthly subcutaneous injection. The drug has shown promising results in treating metabolic dysfunction-associated steatohepatitis (search) (MASH (search)) and will also be evaluated for alcohol-related liver disease (search) (ALD (search)).
Addressing a Significant Unmet Medical Need
Steatotic liver disease (search), characterized by fat buildup in the liver associated with inflammation and fibrosis, affects approximately 5% of the global population. The condition encompasses both MASH (search) and ALD (search), with limited therapeutic options currently available. ALD affects about 26 million patients globally and, together with MASH, represents the leading cause of liver transplants in the United States.
Tony Wood, GSK's Chief Scientific Officer, highlighted the drug's potential: "Efimosfermin has the potential to define a new standard-of-care with its monthly dosing and tolerability profile. It 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."
Impressive Phase 2 Results
In November 2024, Boston Pharmaceuticals shared results from a Phase 2 study evaluating efimosfermin alfa (formerly known as BOS-580) at the American Association for the Study of Liver Diseases meeting. The data demonstrated that treatment with efimosfermin led to significant improvements in fibrosis ≥1 stage without worsening of MASH (search), and MASH resolution without worsening of fibrosis over 24 weeks.
Study participants showed rapid and significant improvement in fibrosis biomarkers and reductions in non-invasive markers of liver injury and liver fat. Notably, participants with type 2 diabetes also experienced significant and clinically meaningful improvement in HbA1c values.
The drug demonstrated a favorable tolerability profile with low discontinuation rates due to adverse events and a low incidence of gastrointestinal side effects and injection site reactions.
Strategic Fit in GSK's Portfolio
The acquisition complements GSK's existing hepatology pipeline, particularly its siRNA therapeutic GSK'990 (search), which is currently in development for other subsets of SLD patients. GSK noted that efimosfermin's direct anti-fibrotic mechanism of action could address more advanced stages of SLD and potentially be used in combination with GSK'990.
As part of the agreement, GSK will also be responsible for success-based milestone payments and tiered royalties for efimosfermin owed to Novartis Pharma.
Elias Zerhouni, chair of Boston Pharmaceuticals' board, expressed optimism about the acquisition: "We are delighted that GSK recognized efimosfermin's potential to address a growing global public health concern and unmet medical need. Together, we look forward to efimosfermin's ongoing journey to become a best-in-class treatment for patients with SLD."
Market Impact and Future Outlook
The acquisition strengthens GSK's position in the hepatology space, with the company expecting the first launch of efimosfermin in 2029. The deal reflects the growing importance of addressing liver diseases, which represent a significant global health burden with limited treatment options.
With its once-monthly dosing regimen and promising efficacy and safety profile, efimosfermin has the potential to transform the treatment landscape for patients with steatotic liver disease (search), offering new hope for those with limited therapeutic alternatives.