Casimersen: First Approval

Declarations

Funding The preparation of this review was not supported by any external funding.

Authorship and Conflict of interest During the peer review process the manufacturer of the agent under review was offered an opportunity to comment on the article. Changes resulting from any comments received were made by the author on the basis of scientific completeness and accuracy. M. Shirley is a salaried employee of Adis International Ltd/Springer Nature, and declares no relevant conflicts of interest. All authors contributed to the review and are responsible for the article content.

Ethics approval, Consent to participate, Consent to publish, Availability of data and material, Code availability Not applicable.

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Abstract

Casimersen (Amondys 45™) is an antisense oligonucleotide of the phosphorodiamidate morpholino oligomer subclass developed by Sarepta Therapeutics for the treatment of Duchenne muscular dystrophy (DMD) in patients who have a mutation in the DMD gene that is amenable to exon 45 skipping. Administered by intravenous infusion, casimersen is designed to bind to exon 45 of the DMD gene pre-mRNA, resulting in skipping of this exon during mRNA processing, intended to allow for production of an internally truncated but functional dystrophin protein in patients with DMD. Casimersen received its first approval on 25 February 2021, in the USA, for the treatment of DMD in patients who have a confirmed mutation of the DMD gene that is amenable to exon 45 skipping. The approval, granted under the US FDA Accelerated Approval Program, was based on an observed increase in dystrophin production in skeletal muscle in patients treated with casimersen. Casimersen is continuing in phase III development for the treatment of DMD in several other countries worldwide. This article summarises the milestones in the development of casimersen leading to this first approval for DMD. As with other approvals under the Accelerated Approval Program, continued approval for this indication may be contingent upon verification of a clinical benefit in confirmatory trials.

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