Efimosfermin Leads to Significant MASH Improvement

Medscape

09-05-2025

SAN DIEGO — Boston Pharmaceuticals' once-monthly efimosfermin alfa (formerly BOS-580) prescribed for metabolic dysfunction–associated steatohepatitis (MASH) with F2 and F3 fibrosis significantly improved MASH resolution and fibrosis after 24 weeks, according to results of a phase 2 trial presented at Digestive Disease Week (DDW) 2025.
An analogue of the fibroblast growth factor 21 (FGF21) protein, the agent regulates metabolic processes to reduce liver fat. It has a half-life of about 21 days, said study presenter Margaret J. Koziel, MD, chief medical officer at Boston Pharmaceuticals.
MASH is marked by inflammation and fibrosis and can progress to cirrhosis and liver failure. About 2%-5% of US adults have MASH, according to the American College of Gastroenterology. Up to 20% of adults who are obese may have the condition.
The researchers randomly assigned 84 participants with biopsy-confirmed F2/F3 MASH to receive once-monthly injections of 300 mg efimosfermin alpha (43 patients) or placebo (41 patients) for 24 weeks.
The mean body mass index (BMI) of participants in both groups was about 37. Most study sites were in the southern United States, so that BMI 'reflects the demographics,' Koziel said. Mean age was 55 years in the placebo group and 53 years in the treatment group, and about half of patients in both groups were women. Eighteen patients in each group had a fibrosis stage of F3.
Primary endpoints were safety and tolerability.
Exploratory objectives included the proportion of patients achieving fibrosis improvement of one or more stages without MASH worsening, MASH resolution without worsening of fibrosis, or both fibrosis improvement and MASH resolution.
Sixty-seven patients completed the treatment, and 65 post-baseline biopsies were collected — 34 in the placebo group and 31 in the treatment group.
Positive Results
'We saw statistically significant changes in fibrosis improvement,' Koziel said. 'This has been the hardest barrier to hit.'
After 24 weeks, 45% of patients in the treatment group and 21% in the placebo group showed fibrosis improvement of one or more stages without worsening of MASH ( P = .038), and 68% of those in the treatment group and 29% in the placebo group had MASH resolution without fibrosis worsening ( P = .002).
The between-group difference in fibrosis improvement and MASH resolution did not reach statistical significance, with 39% of patients in the treatment group and 18% in the placebo group achieving the combined endpoint ( P = .066). 'It just missed statistical significance,' Koziel said, but she viewed the outcome as meaningful.
Additionally, 'a third of the group taking efimosfermin normalized their liver fat, and all but one normalized their liver enzymes,' she said.
Adverse events — most often nausea, vomiting and diarrhea — were mild to moderate in both groups, Koziel said. In the treatment group, one patient withdrew from the study due to a grade 3 serious adverse event, and two others did so due to low-grade adverse events.
'These data support further development of once-monthly efimosfermin for the treatment of MASH-related fibrosis,' the research team concluded.
Hopeful Development
'Finally, there's hope,' said DDW attendee Na Li, MD, associate clinical professor of internal medicine at Ohio State University Wexner Medical Center, Columbus, Ohio, whose clinical focus is on metabolic-associated steatotic liver disease.
The new hope, she said, refers not only to the phase 2 study results but to the Food and Drug Administration approval of resmetirom (Rezdiffra) last year, which reduces liver fat by stimulating thyroid hormone receptor beta. 'That was the first medication that got approved with a specific indication to treat MASH,' she said. Before that, lifestyle measures aimed at weight loss were the only approach.
Lifestyle measures are still important, Li said, but it's helpful to have additional options. 'There are quite a few agents in the pipeline now,' she said. One example is another FGF21 analogue efruxifermin, which is in phase 3 trials.