CHMP Rejects Sarepta’s DMD Drug, Company Strikes Gene Therapy Deal with Myonexus Therapeutics

Sarepta

Shares of Sarepta Therapeutics slipped Thursday after the company announced a European Medicines Agency committee rejected Exondys 51 (eteplirsen), the company’s treatment for Duchenne Muscular dystrophy.

Sarepta revealed the rejection during a Thursday call with investors and analysts to discuss the company’s first quarter results. Sarepta announced that the EMA Committee for Medicinal Products for Human Use voted against Exondys 51 following the company’s oral explanations. Sarepta said it will request re-examination of the data it submitted and for the Scientific Advisory Group to be convened.

Doug Ingram, Sarepta's president and chief executive officer downplayed the rejection, calling it a “delay” in the company’s effort to bring eteplirsen to patients in Europe. Ingram said the holdup over the CHMP’s rejection was not over efficacy concerns, but that the company had not “met the regulatory threshold for conditional approval.” Ingram said that appears to hinge on the company’s use of external controls as comparators in the studies.

“Sarepta plans to file for re-examination and will request that a Scientific Advisory Group, which is made up of DMD and neuromuscular specialists, be convened to provide expert guidance and insight into, among other things, the validity of the external controls used and the importance of slowing pulmonary decline in patients with DMD,” Ingram said in a statement.

The battle for approval in Europe will likely be as tough as the battle Sarepta faced in the United States. Exondys 51, formerly known as eteplirsen, was approved by the U.S. Food and Drug Administration for treatment of DMD in September 2016. It was the first drug of its kind for DMD patients. The drug was hotly contested before it was finally approved by the FDA, with strong support from the DMD community in the United States.

Duchenne muscular dystrophy is an X-linked degenerative neuromuscular disorder causing severe progressive muscle loss and premature death. One of the most common fatal genetic disorders, DMD affects approximately one in every 3,500 boys born worldwide. DMD is associated with specific errors in the gene that codes for dystrophin, a protein that plays a key structural role in muscle fiber function.

Exondys 51 is designed to skip exon 51, a genetic mutation in the DNA sequence for DMD. Exon skipping is intended to allow for production of an internally truncated but functional dystrophin protein.

During the first quarter of 2018 Exondys 51 brought in net revenues of $64.6 million, the company said in its report.

Sarepta is on its way to seeking approval for a second DMD drug in the United States. Earlier this year the company said it intends to file for approval of its drug candidate golodirsen, a phosphordiamidate morpholino oligimer engineered to treat DMD who have genetic mutations subject to skipping exon 53 of the DMD gene. The company hopes to receive accelerated approval, which could allow it to begin marketing the drug before completion of an ongoing Phase III study.

During the first quarter, Sarepta said it signed an exclusive partnership and buy-out option with Myonexus Therapeutics, which will expand the company’s pipeline expands from 16 to 21 programs. The two companies will develop multiple gene therapy programs aimed at treating distinct forms of limb-girdle muscular dystrophy, the company said. The lead Myonexus program, MYO-101, has generated encouraging pre-clinical safety and efficacy data utilizing the AAVrh.74 vector system, the same vector used in the micro-dystrophin gene therapy program, Sarepta said in its announcement. A Phase I/IIa study of MYO-101 is scheduled to begin in mid-2018.

Under terms of the deal with Myonexus, Sarepta paid the company $60 million in upfront money. Sarepta will pay the company up to $45 million in milestone payments if goals are met, the company said.

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