The combination of zalfermin and semaglutide has additive therapeutic effects in a diet-induced obese and biopsy-confirmed mouse model of MASH

Fibroblast growth factor 21 (FGF21) analogs have significant therapeutic potential in metabolic dysfunction-associated steatohepatitis (MASH) but limited body weight effects in patients with MASH. This study investigated the effect of combined treatment with the FGF21 analog zalfermin and the glucagon-like peptide-1 receptor agonist semaglutide on body weight and plasma and liver biochemistry and histology in a mouse model of MASH. Amylin liver nonalcoholic steatohepatitis diet-induced obese-MASH mice with biopsy-confirmed MASH and fibrosis were administered (subcutaneous [SC], daily [QD]) vehicle, zalfermin (0.05 or 0.2 mg/kg), semaglutide (3 or 120 µg/kg), or zalfermin 0.05 mg/kg + semaglutide 3 µg/kg for 8 weeks (n = 11-12 per group). Vehicle-dosed (SC, QD) chow-fed mice served as normal controls (n = 10). Pre- to post-liver biopsy histology was compared for within-subject evaluation of changes in non-alcoholic fatty liver disease Activity Score (NAS), fibrosis stage, and quantitative histology. Additional endpoints included plasma/liver biochemistry and liver RNA sequencing. Combined low-dose zalfermin and semaglutide treatment resulted in super-additive body weight loss (-18%) vs. individual low-dose monotherapies (zalfermin, -6%; semaglutide, -4%) and was equally effective as high-dose zalfermin monotherapy (-16%) and semaglutide (-15%). Low-dose combination therapy promoted greater benefits on transaminases, total cholesterol and triglycerides, NAS, steatosis, and inflammation vs. individual low-dose monotherapies and high-dose semaglutide, and high-dose zalfermin was as effective as the low-dose combination therapy on most endpoints. Combination treatment reduced gene expression markers of fibrosis to a greater degree than monotherapies. In conclusion, combined low-dose zalfermin and semaglutide, as well as high-dose zalfermin, resulted in beneficial effects on body weight and biochemical and histological endpoints, supporting the clinical development of zalfermin as therapy for patients with MASH.