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GlaxoSmithKline Receives 17th FDA Breakthrough Therapy Designation

June 28, 2013

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GlaxoSmithKline (GSK) announces on June 27, 2013, that the FDA grants the Breakthrough Therapy Designation to the company’s orphan drug Drisapersen, an exon-51 skipping compound, for the potential treatment of Duchenne Muscular Dystrophy (DMD). Drisapersen is a drug designed to skip over the defective exon 51 in DMD patients and to produce functional dystrophin. GSK has exclusive, worldwide rights to develop and commercialize Drisapersen from Prosensa under a 2009 deal. DMD is a “severely debilitating childhood neuromuscular disease that affects 1 in 3,500 live male births. The rare disease is caused by mutations in the dystrophin gene, resulting in the absence or defect of the dystrophin protein.”

The Breakthrough Therapy Designation is based on results from a Phase II Study (DMD114117), presented in April 2013, at a RNA & Oligonucleotide Therapeutics Conference, at Cold Spring Harbor Labs, New York.  The Phase II study is a 53-participant, 48-week trial, of Drisapersen with a placebo. Originally, no data from the Phase II Drisapersen study was to be announced until the third quarter 2013, when an ongoing Phase III study was expected to be completed. GSK reports in an Abstract, posted on the CureDuchenne website, that “the primary objective is achieved–the continuous treatment arm showed a clinically meaningful and statistically significant difference from placebo on 6MWD [6-minute walk distance] at week 24. At week 48, both treatment arms showed a clinically meaningful difference from placebo on 6MWD (supported by improvement in other secondary endpoints). Drisapersen may represent an important treatment option for boys with DMD having mutations correctable by exon 51 skipping.”

Exon-skipping is a genetic intervention that alters dystrophin expression in the skeletal muscle. The DMD gene is the largest known human gene that consists of a coding sequence of 79 exons. Exon-skipping excludes particular exons from the dystrophin to bypass mutations. This type of treatment can be applied to approximately 72% of DMD patients (Per Review of Phase II and Phase III clinical trials for Duchenne Muscular Dystrophy. Scully M, Pandya S, Moxley R. Expert Opinion on Orphan Drugs. Jan 2013; 1(1): 33-46).

GSK is currently recruiting for a Phase III late-stage clinical trial for patients with DMD. To be eligible, the patient must be male, five years or older. The company is also running another trial to determine the long-term effects of the drug in males five years and older.

GSK’s Drisapersen is in a race with Sarepta Therapeutics’ orphan drug Eteplirsen to become the first FDA approved drug for the treatment of DMD. DMD patients and their families, investors, and the media, are watching this close competition between rivals. It has been Sarepta Therapeutics who has stolen the media spotlight since the October 2012 World Muscle Society Congress in Perth, Australia, where an abstract titled, “Results at 48 Weeks of a Phase IIb extension study of the exon-skipping drug Eteplirsen in patients with DMD” presented impressive results. In recent months, there has been mounting hype and publicity in Sarepta Therapeutics’ attempts to convince the FDA to grant Accelerated Approval for Eteplirsen. It is GSK’s Drisapersen that in the end has received FDA’s Breatkthrough Therapy Designation. But GSK is dealing with reports related to the side effects caused by Drisapersen. The news of GSK’s Breakthrough Therapy Designation is also a positive for Prosensa, who has filed for an IPO.

Please Note: FDA Official Logo from FDA website.

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