AMO Pharma Aligns With Regulators on Registrational Study for AMO-02 in Myotonic Dystrophy

In recent news, AMO Pharma announced agreement with regulators in the US, UK, and Canada on the design of a planned registrational study of AMO-02 (oral tideglusib) for congenital myotonic dystrophy type 1 (cDM1).

Based on feedback from meetings held over the past 6 months, the study will use hospitalization as its primary outcome measure, supported by multiple functional assessments as secondary measures. AMO Pharma said it expects to provide an update on the study's initiation in the third quarter of 2026.¹

"We appreciate the thoughtful engagement of FDA, MHRA and Health Canada throughout this important process and are pleased to have received feedback that informs the design of the planned registrational study for AMO-02," Mike Snape, PhD, chief executive officer of AMO Pharma, said in a statement.¹ "With insights from these regulatory agencies, we are now well positioned to plan and execute a registrational study as quickly as possible."¹

Supporting long-term safety data

The hospitalization endpoint draws on long-term data from REACHCDM-X, AMO Pharma's ongoing open-label extension study and, according to the company, the largest and longest-running interventional study conducted in congenital and childhood-onset DM1. Across more than 151 patient-years of exposure, participants treated with AMO-02 experienced a hospitalization rate of 0.14 events per patient per year, with no deaths or cardiovascular events reported.²

As of August 2025, 45 participants remained on treatment, including 20 who had received AMO-02 for more than 3 years; of 14 who discontinued, only 1 did so due to an adverse event (elevated liver enzymes). Most adverse events were mild or moderate, consisting primarily of respiratory infections and gastrointestinal events consistent with the natural course of the disease. In a secondary 10-meter walk/run test, participants aged 10 and older showed little or no decline over a year of treatment.²

"We are pleased to share new findings that reflect the experience of patients treated with AMO-02 for almost four full years...we were especially encouraged by the low rate of hospitalizations observed during the study," Snape said at the time the data were reported.² AMO Pharma has submitted these data to the FDA and said it plans to submit them to Health Canada and the MHRA as well.

Efficacy signals from REACH-CDM

The hospitalization-focused design also reflects lessons from AMO Pharma's earlier pivotal REACH-CDM trial, a 56-participant, double-blind, placebo-controlled study in children and adolescents with cDM1. That trial missed its primary endpoint, a clinician-administered rating scale, after both treatment and placebo groups showed improvement, an effect the company attributed in part to pandemic-related disruptions to patient monitoring and reporting compliance.³

Despite missing the primary endpoint, the trial showed statistically significant benefit with AMO-02 relative to placebo on several functional and biomarker measures, including cognitive performance on the Peabody Picture Vocabulary Test (P < .05), a reduction in creatine phosphokinase, a biomarker of skeletal and cardiac muscle integrity (P < .05), and near-significant improvement on the 10-meter walk/run test (P = .054).

READ MORE: Phase 3 BEACON Trial in Angelman Syndrome Gets Underway

A composite analysis spanning motor skills, muscle strength, cognition, daily living skills, and biomarker data also showed a statistically significant benefit favoring AMO-02 (P < .05), and higher plasma AMO-02 levels were associated with greater clinical improvement. Following the trial, 98% of participants opted to continue into an open-label extension, and 85% opted to continue again after that extension's first year.

"We are very encouraged by the consistent benefit shown across multiple clinically confirmed measures of efficacy," Joe Horrigan, MD, then chief medical officer at AMO Pharma, said in a statement at the time.³

Preclinical context

AMO-02 has also shown activity beyond DM1. In a mouse-model study conducted with Brock University in a dystrophic mdx model of Duchenne muscular dystrophy (DMD), 1 month of AMO-02 treatment was associated with improved skeletal muscle function, improved glucose handling, reduced muscle fat deposition, and benefits in cardiac and CNS function, with effects seen at both early and advanced stages of disease.⁴

"Benefit was seen in multiple organ domains including heart and brain as well as in metabolic function, skeletal muscle, and glucose and fat handling," Val Fajardo, PhD, of Brock University, said in a statement.⁴ AMO-02 is not currently in registered clinical development for DMD.

Mechanism and disease background

AMO-02, an investigational agent, works by inhibiting glycogen synthase kinase 3β (GSK3β), an enzyme with abnormally elevated activity in DM1 and DMD, and by disrupting the accumulation of the abnormal RNA repeats that drive cDM1 pathology.⁵ For context, congenital DM1 is a rare, inherited neuromuscular disorder that can cause serious and lifelong effects on muscle function, learning, development, and cardiac health, with many affected individuals experiencing complications requiring hospitalization and ongoing multidisciplinary care.

REFERENCES
1. AMO Pharma Announces Update on Scientific Advice for Registrational Clinical Study of AMO-02 in Congenital Myotonic Dystrophy Type 1 Following Meetings with the U.S. Food and Drug Administration, the U.K. Medicines and Healthcare products Regulatory Agency and Health Canada. News release. AMO Pharma Limited. July 6, 2026. Accessed August 19, 2026. https://www.prnewswire.com/news-releases/amo-pharma-announces-update-on-scientific-advice-for-registrational-clinical-study-of-amo-02-in-congenital-myotonic-dystrophy-type-1-following-meetings-with-the-us-food-and-drug-administration-the-uk-medicines-and-healthcare--302818756.html
2. AMO Pharma Reports Long-Term Safety Data from REACHCDM-X Study of AMO-02 in Treatment of Congenital Myotonic Dystrophy Type 1. News release. AMO Pharma Limited. September 15, 2025. Accessed August 19, 2026. https://www.prnewswire.com/news-releases/amo-pharma-reports-long-term-safety-data-from-reachcdm-x-study-of-amo-02-in-treatment-of-congenital-myotonic-dystrophy-type-1-302555592.html
3. AMO Pharma Announces Affirming Data from REACH-CDM Clinical Trial for AMO-02 in Treatment of Myotonic Dystrophy. News release. AMO Pharma Limited. September 6, 2023. Accessed August 19, 2026. https://www.prnewswire.com/news-releases/amo-pharma-announces-affirming-data-from-reach-cdm-clinical-trial-for-amo-02-in-treatment-of-myotonic-dystrophy-301918241.html
4. AMO Pharma Announces Preclinical Data Showing AMO-02 Improves Muscle Function, Glucose Handling and CNS function in Mouse Models of Duchenne Muscular Dystrophy. News release. AMO Pharma Limited. September 19, 2023. Accessed August 19, 2026. https://www.prnewswire.com/news-releases/amo-pharma-announces-preclinical-data-showing-amo-02-improves-muscle-function-glucose-handling-and-cns-function-in-mouse-models-of-duchenne-muscular-dystrophy-301931362.html
5. Angeard N, Jauffret C, Gargiulo M, et al. A Phase 2 Study of AMO-02 (Tideglusib) in Congenital and Childhood-Onset Myotonic Dystrophy Type 1 (DM1). Pediatr Neurol. 2021;115:20-28. doi:10.1016/j.pediatrneurol.2020.10.001