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. 

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.