Alexion bags option on Stealth's phase 3 rare disease drug

ludwig hantson
Alexion CEO Ludwig Hantson (Alexion)

Alexion has put up $30 million to land an option to co-develop Stealth BioTherapeutics’ phase 3 primary mitochondrial myopathy (PMM) prospect. The agreement gives Alexion the chance to pick up most of the global rights to the mitochondria-targeted therapy after Stealth posts results from an ongoing late-phase study.

Stealth went public earlier this year, raising $78 million to take its lead asset elamipretide through to the delivery of phase 3 data. Stealth expects to wrap up the phase 3 and deliver data around the end of the year. 

If the trial delivers positive data, Stealth has a shot at becoming the first company to win approval in the U.S. and Europe for a drug to treat PMM, a disease characterized by debilitating skeletal muscle weakness that the startup thinks affects around 40,000 people in the U.S. 

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The deal unveiled today means Alexion may be the company that gets to target those patients. In return for a $15 million equity investment and a $15 million upfront package comprising an option fee and development funding, Alexion has secured the chance to bag the exclusive ex-U.S. rights to elamipretide and co-promote the product in the U.S.  If Alexion takes up that option, it will commit to additional option-related and milestone-dependent payments. 

Alexion’s option covers the use of elamipretide in PMM and two other indications: Barth syndrome and Leber’s hereditary optic neuropathy (LHON). Elamipretide has advanced deep into the clinic in the other two indications but has delivered some weak data along the way.

A phase 2/3 trial of elamipretide in Barth missed its primary endpoint late last year, leaving Stealth to point to “trends toward improvement” in a subset of patients to suggest the drug has a future in the indication. Elamipretide also failed to achieve the primary endpoint in a phase 2 LHON trial, although Stealth again highlighted trends favoring the drug. The studies joined an earlier phase 2 acute coronary syndrome trial on the list of failures involving elamipretide.

Stealth, which had run up an accumulated deficit of $400 million by the time of its IPO, now has a shot at putting those failures behind it by delivering data that secure a deal with Alexion. For Alexion, the option is the latest in a series of deals intended to lessen its reliance on Soliris.

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