An In-Depth Analysis of MTR-601: A First-in-Class Selective Myosin-2 Inhibitor for Muscle Spasticity

Executive Summary

MTR-601 is an investigational, orally administered, small molecule drug representing a potential first-in-class antispastic therapy.[1] Developed by Motric Bio, MTR-601 functions as a highly selective inhibitor of the myosin heavy chain 2 (MYH2) protein, the molecular motor responsible for contraction in fast-twitch skeletal muscle.[1] The core scientific innovation of MTR-601 lies in its unique mechanism, which targets a single amino acid variation (L476) exclusive to the fast-twitch skeletal myosin-2 isoform.[3] This precision is designed to confer high selectivity, thereby relaxing overactive skeletal muscles while potentially avoiding the significant off-target cardiotoxicity that has historically hindered the development of less selective myosin inhibitors.[3]

The clinical development program for MTR-601 is advancing, having successfully completed a Phase 1 first-in-human study (NCT06117020) in healthy volunteers, which reportedly demonstrated that the drug was safe and well-tolerated.[2] This positive safety profile has enabled the program to progress to a pivotal Phase 2a clinical trial (NCT06830642).[1] This study, which began recruiting in the first quarter of 2025, is designed to assess the safety, tolerability, and efficacy of MTR-601 in patients with cervical dystonia, a debilitating neurological movement disorder.[1]