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.
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Information & Authors
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© 2018 American Academy of Neurology.
Publication History
Received: October 13, 2017
Accepted: March 15, 2018
Published online: May 11, 2018
Published in issue: June 12, 2018
Disclosure
J. Charleston, F. Schnell, and J. Dworzak are employees of Sarepta Therapeutics and may own stock/options in the company. J. Dworzak is currently working in the marketing department of Sarepta Therapeutics and was working in the translational development department at the time of this research. C. Donoghue is an employee of Sarepta Therapeutics and may own stock/options in the company. S. Lewis and L. Chen report no disclosures relevant to the manuscript. G. Young and A. Milici are employees of Flagship Biosciences, which was contracted by Sarepta Therapeutics. J. Voss and U. DeAlwis are employees of Sarepta Therapeutics and may own stock/options in the company. B. Wentworth was an employee of Sarepta Therapeutics at the time of this research. L. Rodino-Klapac received a research grant from Sarepta Therapeutics. Z. Sahenk serves as a remunerated consultant for Sarepta Therapeutics, providing pathology consulting services. D. Frank is an employee of Sarepta Therapeutics and may own stock/options in the company. J.R. Mendell serves as a consultant to Sarepta Therapeutics, reviewing and advising on clinical trials subsequent to the study reported here. Go to Neurology.org/N for full disclosures.
Study Funding
This study was supported by Sarepta Therapeutics, Inc.
Authors
Author Contributions
J.R. Mendell, J.S. Charleston, D. Frank, and J. Dworzak contributed to the study design. J.R. Mendell, F.J. Schnell, C. Donoghue, L. Chen, A.J. Milici, D. Young, L.R. Rodino-Klapac, and Z. Sahenk served as study investigators. F.J. Schnell, C. Donoghue, S. Lewis, L. Chen, L.R. Rodino-Klapac, and Z. Sahenk acquired the study data. J.S. Charleston, G.D. Young, A.J. Milici, U. DeAlwis, B. Wentworth, D. Frank, J. Dworzak, and J. Voss provided data analysis. J.S. Charleston, J. Dworzak, and D. Frank participated in manuscript preparation. All authors contributed to the interpretation of the data and to the critical review and revision of the manuscript. All authors approved the final draft of the manuscript for submission.
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