Tolperisone is a nonopioid, centrally acting muscle relaxant in clinical development in the USA for the treatment of symptoms associated with acute, painful muscles spasms of the back. CLN-301, RESUME-1, is a 14-day double-blind, randomized, placebo-controlled, parallel-group Phase III study of the efficacy and safety of tolperisone administered orally three-times daily in 1000 male and female subjects at approximately 70 clinical sites in the USA experiencing back pain due to or associated with muscle spasm of acute onset. Tolperisone is a promising therapeutic for managing acute, painful muscle spasms of the back as it appears to lack the off-target CNS effects often seen with conventional skeletal muscle relaxants. Clinical Trials Registration: NCT04671082