Eteplirsen treatment for Duchenne muscular dystrophy: Exon skipping and dystrophin production.

Abstract

OBJECTIVE:

To describe the quantification of novel dystrophin production in patients with Duchenne muscular dystrophy (DMD) after long-term treatment with eteplirsen.

METHODS:

Clinical study 202 was an observational, open-label extension of the randomized, controlled study 201 assessing the safety and efficacy of eteplirsen in patients with DMD with a confirmed mutation in the DMD gene amenable to correction by skipping of exon 51. Patients received once-weekly IV doses of eteplirsen 30 or 50 mg/kg. Upper extremity muscle biopsy samples were collected at combined study week 180, blinded, and assessed for dystrophin-related content by Western blot, Bioquant software measurement of dystrophin-associated immunofluorescence intensity, and percent dystrophin-positive fibers (PDPF). Results were contrasted with matched untreated biopsies from patients with DMD. Reverse transcription PCR followed by Sanger sequencing of newly formed slice junctions was used to confirm the mechanism of action of eteplirsen.

RESULTS:

Reverse transcription PCR analysis and sequencing of the newly formed splice junction confirmed that 100% of treated patients displayed the expected skipped exon 51 sequence. In treated patients vs untreated controls, Western blot analysis of dystrophin content demonstrated an 11.6-fold increase (p = 0.007), and PDPF analysis demonstrated a 7.4-fold increase (p < 0.001). The PDPF findings were confirmed in a re-examination of the sample (15.5-fold increase, p < 0.001). Dystrophin immunofluorescence intensity was 2.4-fold greater in treated patients than in untreated controls (p < 0.001).

CONCLUSION:

Taken together, the 4 assays, each based on unique evaluation mechanisms, provided evidence of eteplirsen muscle cell penetration, exon skipping, and induction of novel dystrophin expression.

CLASSIFICATION OF EVIDENCE:

This study provides Class II evidence of the muscle cell penetration, exon skipping, and induction of novel dystrophin expression by eteplirsen, as confirmed by 4 assays.

• Authors: Jay S Charleston, Frederick J Schnell, Johannes Dworzak, Cas Donoghue, Sarah Lewis, Lei Chen, G David Young, Anthony J Milici, Jon Voss, Uditha DeAlwis, Bruce Wentworth, Louise R Rodino-Klapac, Zarife Sahenk, Diane Frank, Jerry R Mendell
• Journal: Neurology (Neurology) Vol. 90 Issue 24 Pg. e2146-e2154 (06 12 2018) ISSN: 1526-632X [Electronic] United States
• PMID: 29752304 (Publication Type: Journal Article, Observational Study, Randomized Controlled Trial, Research Support, Non-U.S. Gov't)
• Copyright: © 2018 American Academy of Neurology.

Chemical References

• Dystrophin
• Morpholinos
• eteplirsen

Topics

• Biopsy
• Child
• Dystrophin (biosynthesis)
• Exons (genetics)
• Humans
• Morpholinos (therapeutic use)
• Muscle, Skeletal (metabolism, pathology)
• Muscular Dystrophy, Duchenne (drug therapy, genetics, metabolism)
• Treatment Outcome