BACKGROUND & AIMSGlucagon-like peptide-1 (GLP-1) and fibroblast growth factor 21 (FGF21) are key regulators of glucose and lipid metabolism. In the present study, we assessed the safety and efficacy of a novel GLP-1/FGF21 dual agonist HEC88473 for the treatment of metabolic dysfunction-associated steatotic liver disease (MASLD) combined with type 2 diabetes mellitus (T2DM).METHODSThis was a randomized, double-blind, placebo-controlled, multiple-ascending-dose phase Ib/IIa trial. Sixty patients with MASLD and T2DM were randomized (10:2) to receive HEC88473 (5.1, 15.3, 30.6, 45.9, or 68.0 mg) or placebo via weekly subcutaneous injection for 5 weeks.RESULTSAfter 5 weeks of treatment with HEC88473, MRI-proton density fat fraction (MRI-PDFF) was reduced in a dose-proportional manner. The largest relative mean change reached -47.21% (p = 0.0143) in the 30.6 mg cohort, compared with -15.05% in the placebo group, with a higher proportion of >30% relative reductions in patients with baseline PDFF >8%. The 5-week treatment with HEC88473 significantly reduced levels of HbA1c (glycated hemoglobin), as well as fasting and postprandial glucose levels. The largest mean change in HbA1c was -1.10% in the 68.0 mg cohort, compared with -0.31% in the placebo group. Improvement was also observed in participants' lipid profiles. Most adverse events were mild to moderate in severity. The most frequently reported adverse events were gastrointestinal disorders (n = 29, 48.3%).CONCLUSIONSHerein, we report the clinical safety and proof-of-concept data for the GLP-1/FGF21 dual agonist HEC88473. A 5-week treatment with HEC88473 was generally safe and well tolerated, with multiple positive effects observed, including reduced liver fat, and improved glycemic control, insulin resistance and lipid metabolism, together indicating comprehensive improvement in metabolic syndrome.IMPACT AND IMPLICATIONSIn this randomized, double-blind, placebo-controlled phase Ib/IIa study, we assessed clinical safety, pharmacodynamic and pharmacokinetic data of the GLP-1/FGF21 dual agonist HEC88473 in patients with MASLD (metabolic dysfunction-associated steatotic liver disease) and T2DM (type 2 diabetes mellitus). HEC88473 was generally safe and well tolerated. The GLP-1/FGF21 dual agonist significantly reduced the hepatic fat fraction assessed using MRI-proton density fat fraction, and improved glycemic control and lipid profiles with only 5 weeks' treatment, leading to comprehensive improvement in metabolic syndrome. The present results suggest that HEC88473 could be a promising treatment option in this patient population.CLINICAL TRIAL NUMBERChinese Drug Trial Identifier (http://www.chinadrugtrials.org.cn/index.html): CTR20211088.CLINICALTRIALSGOV: NCT05943886.