Sanofi backs down from fight with AstraZeneca, argenx and more by stopping phase 3 trial of $3.7B drug

Sanofi backs down from fight with AstraZeneca, argenx and more by stopping phase 3 trial of $3.7B drug

The fight for the myasthenia gravis market has become too hot for Sanofi to handle. After reviewing the competitive landscape, the Big Pharma has decided to stop a phase 3 clinical trial of a drug candidate it acquired in its $3.7 billion takeover of Principia Biopharma.

Myasthenia gravis, a rare long-term condition that causes muscle weakness, has emerged as a focus for several drug developers in recent years. Alexion, now part of AstraZeneca, won approval for Soliris in the indication in 2017 before following up with an OK for Ultomiris last year. In between those approvals, argenx secured the green light to sell Vyvgart in the U.S.

UCB has filed for approval of two molecules, zilucoplan and rozanolixizumab, in the indication. Johnson & Johnson is following close behind, with the phase 3 trial of its challenger nipocalimab scheduled to get to primary completion by the end of the year.

The throng of companies targeting the indication has caused Sanofi to bow out. The French pharma began a phase 3 trial of tolebrutinib, the BTK inhibitor it acquired in the Principia buyout, in myasthenia gravis at the end of 2021. However, last summer, cases of drug-induced liver injury led Sanofi to pause enrollment in the study and in its phase 3 multiple sclerosis program.

At the time, Sanofi outlined plans to get the FDA partial clinical hold lifted in the fourth quarter but has now decided to walk away from myasthenia gravis while continuing to advance tolebrutinib in multiple sclerosis. In a full-year earnings document this morning, Sanofi said it reached the decision after a “careful evaluation of the emerging competitive treatment landscape.”

Even before the partial clinical hold, Sanofi faced the prospect of being late to the party. The phase 3 trial had a primary completion date of November 2024, suggesting Sanofi would have faced a fight to win a share of a market already served by drugs from argenx, AstraZeneca, J&J and UCB.

The decision leaves Sanofi looking to multiple sclerosis for a return on its $3.7 billion Principia bet. A phase 3 trial in non-relapsing secondary progressive multiple sclerosis hit its recruitment target late last year. Sanofi is continuing to recruit patients for its primary progressive multiple sclerosis trial outside of the U.S.

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