Design, Synthesis, and Biological Evaluation of Novel ML-167 Analogues as Therapeutic Candidates Against Sarcopenia-Induced Muscle Wasting

Background: Sarcopenia is an aging-related syndrome characterized by loss of skeletal muscle mass, strength, and function, with no approved pharmacological treatment. This study aimed to design, synthesize, and evaluate novel ML-167 derivatives for sarcopenia-associated muscle wasting. Methods: ML-167 derivatives were synthesized and characterized by 1H NMR, 13C NMR, and mass spectrometry. Biological activity was evaluated in C2C12 myoblasts using MTT and Western blot assays. Selected compounds were evaluated in a dexamethasone-induced muscle wasting model. Muscle strength, mass, biochemical parameters, and histopathology were assessed. Structure–activity relationships were analysed using cell viability, molecular docking, and ligand efficiency data, alongside physicochemical properties. Results: Compounds 6b (116%), 3a (115%), 8d (114%), 4c (112%), 3m (112%), and 3c (111%) showed the highest C2C12 viability at 1 μM. Compounds 3a, 3c, and 6b increased MyH3 expression by approximately 1.6–1.7-fold, while MyoG remained near basal levels. In vivo, these compounds improved muscle strength, mass, and biochemical parameters without overt hepatic or renal abnormalities based on assessed serum and histopathological findings. Among the evaluated derivatives, compound 6b emerged as the most promising overall lead candidate, showing the greatest improvement in skeletal muscle mass and metabolic parameters, whereas compound 3c demonstrated the strongest histopathological protection and favourable effects on muscle strength with favourable physicochemical properties. Molecular docking supported the SAR trends, although did not consistently correlate with cellular activity. Conclusions: The findings identify 3a, 3c, and 6b as promising lead compounds and support further investigation of ML-167 derivatives as potential pharmacological approaches for sarcopenia-associated muscle wasting.