Last reviewed 2026-04-20 · How we verify

Amondys 45 (CASIMERSEN)

Amondys 45 works by binding to specific RNA sequences to prevent the production of a faulty protein that causes Duchenne muscular dystrophy.

Amondys 45 (Casimersen) is an antisense oligonucleotide developed by Sarepta Therapeutics Inc, targeting exon 53 of dystrophin pre-mRNA to treat Duchenne muscular dystrophy. It was FDA-approved in 2021 and is a patented, small molecule modality with a half-life of 3.5 hours. Amondys 45 works by binding to specific RNA sequences, preventing the production of a faulty protein that causes Duchenne muscular dystrophy. The commercial status of Amondys 45 is patented, with no generic manufacturers available. Key safety considerations include the potential for infusion reactions and liver enzyme elevations.

At a glance

Mechanism of action

Casimersen is designed to bind to exon 45 of dystrophin pre-mRNA resulting in exclusion of this exon during mRNA processing in patients with genetic mutations that are amenable to exon 45 skipping. Exon 45 skipping is intended to allow for production of an internally truncated dystrophin protein in patients with genetic mutations that are amenable to exon 45 skipping [see Clinical Studies (14)].

Approved indications

• Duchenne muscular dystrophy

Common side effects

• Upper Respiratory Tract Infections
• Cough
• Pyrexia
• Headache
• Arthralgia
• Oropharyngeal Pain
• Pharyngitis
• Rhinitis
• Ear Pain
• Nausea
• Ear Infection
• Post-traumatic Pain

Key clinical trials

• Study of SRP-4045 (Casimersen) and SRP-4053 (Golodirsen) in Participants With Duchenne Muscular Dystrophy (DMD) (PHASE3)
• A Long-term Observational Study Evaluating Eteplirsen, Golodirsen, or Casimersen in Routine Clinical Practice
• An Extension Study to Evaluate Casimersen or Golodirsen in Patients With Duchenne Muscular Dystrophy (PHASE3)
• A 48-Week, Open Label, Study to Evaluate the Efficacy and Safety of AMONDYS 45, EXONDYS 51, VYONDYS 53 in Subjects With DuchenneMuscular Dystrophy Carrying Eligible DMD Duplications. (PHASE2)
• Dose-Titration and Open-label Extension Study of SRP-4045 in Advanced Stage Duchenne Muscular Dystrophy (DMD) Patients (PHASE1)

Patents

Primary sources

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