This is a multicenter, prospective, randomized controlled investigator-initiated trial (IIT) aimed at evaluating the efficacy and safety of switching to mazdutide therapy in patients with type 2 diabetes mellitus (T2DM) and moderate-to-severe non-alcoholic fatty liver disease (NAFLD) who have achieved glycemic control.

Chinese patients with type 2 diabetes mellitus (T2DM) are susceptible to visceral fat accumulation, which increases the risk of cardiometabolic diseases and mortality. Metabolic associated fatty liver disease (MAFLD) is highly prevalent among Chinese T2DM patients, and the coexistence of T2DM and moderate-to-severe fatty liver significantly elevates liver-related and all-cause mortality. The vicious cycle of hepatic lipid deposition and insulin resistance aggravates T2DM progression, while weight loss has been proven to alleviate hepatopancreatic fat accumulation and improve the management of T2DM.

GLP-1 receptor agonists (GLP-1RAs) including semaglutide are standard therapies for T2DM with glycemic improvement and weight-loss benefits. However, nearly a quarter of patients show poor response to semaglutide. Long-term semaglutide treatment may cause GLP-1 receptor desensitization, and the agent lacks direct regulatory effects on adipose tissue and hepatic lipid metabolism. Clinically, many patients still have persistent moderate-to-severe fatty liver despite standardized semaglutide therapy, highlighting an unmet clinical need for optimized treatment.

Mazdutide is a novel dual GLP-1R/GCGR agonist. GCGR is highly expressed in the liver and adipose tissues. Via GCGR activation, mazdutide directly inhibits hepatic lipogenesis, promotes hepatic fat decomposition and fatty acid oxidation, and improves adipose tissue browning and thermogenesis. Compared with single GLP-1RAs, mazdutide exerts more direct and comprehensive regulatory effects on hepatic and systemic lipid metabolism, making it a promising option for T2DM patients with residual moderate-to-severe fatty liver after semaglutide treatment.

This study is a multicenter, prospective, stratified randomized controlled design and enrolls T2DM patients with persistent moderate-to-severe NAFLD after receiving subcutaneous semaglutide 1.0 mg once weekly for ≥28 weeks. with 1:1 group allocation and concealed grouping. Eligible subjects are randomized into two groups without drug washout: the intervention group switches to mazdutide therapy, while the control group continues semaglutide treatment. All baseline concomitant medications for metabolic diseases remain stable throughout the study to avoid confounding factors.

Mazdutide is titrated per official instructions, initiating at 2 mg once weekly and escalating to a 4 mg once weekly maintenance dose based on patient tolerability and efficacy. All participants maintain their habitual diet and exercise routines with regular lifestyle supervision to ensure study stability. After the initial intervention phase, patients with <30% reduction in hepatic fat content will receive a mazdutide dose increase to 6 mg once weekly. Meanwhile, the control group will cross over to mazdutide treatment, and all patients will enter the subsequent observational stage.

The primary endpoint is the change in hepatic fat content from baseline to study endpoint, measured by MRI-PDFF and liver elastography, to evaluate the efficacy of mazdutide on hepatic steatosis. Secondary endpoints include inter-group differences in glycemic control, body composition, islet function, liver enzymes and lipid profiles. The efficacy changes during the crossover period are also observed. All adverse events are recorded to assess the safety and tolerability of mazdutide in this patient population.