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Sarepta soars as FDA clears its muscular dystrophy drug

Analysts anticipate blockbuster status for DMD therapy despite efficacy concerns

Sarepta has become the first company to get US approval for a drug to treat Duchenne muscular dystrophy, with the FDA overruling its own advisors in backing the drug.

Sarepta shares closed up 74% yesterday after news of the conditional approval for Exondys 51 (eteplirsen) broke - taking investors by surprise. The biopharma company still has to conduct a new clinical trial to allay lingering concerns about its efficacy and if that fails, the approval will be rescinded.

In the meantime Sarepta has said it will move swiftly to launch the drug, which has been given a list price of $300,000 a year.

Sarepta can also claim to be the first company to secure US approval for a drug that modifies an underlying disease mechanism in DMD after the FDA's rejection of other candidates, including BioMarin's drisapersen and PTC Therapeutics' ataluren.

Exondys 51 is indicated for patients who have a confirmed mutation of the dystrophin gene amenable to exon 51 skipping, which affects about 13% of the approximately 9,000-12,000 people with DMD in the US.

"Accelerated approval makes this drug available to patients based on initial data, but we eagerly await learning more about the efficacy of this drug through a confirmatory clinical trial that the company must conduct after approval," said Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research (CDER).

Documents published by the FDA reviewers ahead of an advisory committee meeting raised major doubts about its efficacy, and those concerns were played out at the meeting with only three of 10 panellists voting that the drug is effective in DMD.

In clinical trials conducted over four years, boys were able to walk around 150 metres further in six minutes compared to the average distance DMD boys of a similar age could walk without treatment.  One of the major criticisms of the trial was that it involved just 12 boys. 

The panel meeting was inundated with patients and their families calling for the FDA to take a chance and green light the drug, and it seems that lobbying effort swayed the agency.

The approval decision is far from unanimous however, with Woodcock in opposition to fellow CDER officials including CDER deputy director Ellis Unger who appealed the decision to approve via the FDA's internal disputes procedures. Meanwhile, the FDA's lead reviewer Ronald Farkas - who criticised the quality of the eteplirsen data in a recent report - left the agency a few weeks ago.

Analysts have suggested that Sarepta will reap the benefits of being the first company to bring a DMD drug to market in the US, with some predicting global sales of up to $2bn for Exondys 51.

Sarepta has not filed for approval of eteplirsen outside the US, although the company has been put under pressure by medical charities to submit it more widely. For example, Muscular Dystrophy UK requested in April that it accelerate plans to proceed with a marketing application in the EU.

Earlier this year, Sarepta Therapeutics told Muscular Dystrophy UK that they plan to apply to the EMA by the end of 2016," said the charity in a statement.

"We have written to Sarepta asking for an update on these plans, in light of the FDA approval," adding that it is also trying to establish whether an orphan drug designation in the EU for another exon 51-skipping therapy - BioMarin's now-abandoned drisapersen - could block eteplirsen's approval.

Article by
Phil Taylor

20th September 2016

From: Regulatory



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