Efficacy Confirmation Study of Aceneuramic Acid Administration for GNE Myopathy in Japan

Background A rare muscle disease, GNE myopathy is caused by mutations in the GNE gene involved in the sialic acid biosynthesis. Our recent phase II/III study has indicated that oral administration of aceneuramic acid to patients would slow disease progression. Methods We conducted a phase III, randomized, placebo-controlled, double-blind, parallel-group, multicenter study. Participants were assigned to receive an extended-release formulation of aceneuramic acid (SA-ER) or placebo. Changes in muscle strength and function over 48 weeks were compared between treatment groups using change in the upper extremity composite (UEC) score from baseline to Week 48 as the primary endpoint and the investigator-assessed efficacy rate as the key secondary endpoint. For safety, adverse events, vital signs, body weight, electrocardiogram, and clinical laboratory results were monitored. Results A total of 14 patients were enrolled and given orally SA-ER (n = 10) or placebo (n = 4) tablets. Decrease in least square mean (LSM) of change in UEC score at Week 48 with SA-ER (−0.115 kg) was numerically smaller as compared with placebo (−2.625 kg), with LSM difference (95% confidence interval) of 2.510 (−1.720 to 6.740) kg. In addition, efficacy rate was higher with SA-ER as compared with placebo. There were no clinically significant adverse events and other safety concerns observed. Conclusions The present study reproducibly showed the effect of orally administered SA-ER on slowing loss of muscle strength and function, indicating supplementation of sialic acid might be a promising replacement therapy for GNE myopathy. Trial registration number: ClinicalTrials.gov (NCT04671472)