Sanofi stock crumbled Thursday after the Food and Drug Administration slapped two of its final-phase studies with a hold, citing safety concerns.
The company is testing the drug, tolebrutinib, in patients with neuromuscular diseases multiple sclerosis and myasthenia gravis. Sanofi scooped up tolebrutinib when it acquired Principia Biopharma in 2020. Now, the FDA has sidelined one of the biggest programs from the buyout.
Due to the potential for liver injury, Sanofi paused U.S. enrollment in the study. Patients who began treatment within the last 60 days should stop. Others can continue.
"The FDA action was based on a limited number of cases of drug-induced liver injury that have been identified with tolebrutinib exposure in Phase 3 studies," Sanofi said in a written statement. "The majority of the impacted patients were determined to have concurrent complications known historically to predispose to drug-induced liver injury."
On the stock market today, Sanofi stock fell 5% to 50.03.
Sanofi Stock: Second Setback For Principia Drug
This isn't a new problem for tolebrutinib. Sanofi said it updated the study protocols last month after a discussion with the FDA about the liver issues. Researchers began monitoring patients more frequently and the company revised the enrollment criteria to exclude patients with preexisting liver conditions.
Still, the clinical hold is a blow to an expensive program for Sanofi. Sanofi first licensed tolebrutinib in 2017 for $40 million upfront and an agreement for future milestone payments. Then, two years ago, the company swooped in with a nearly $3.7 billion Principia buy out.
Bearishly for Sanofi stock, this is the second setback for a Principia drug. Last year, an experimental drug called rilzabrutinib failed to outperform a placebo in patients with a skin condition. Now, Sanofi is testing it in inflammatory conditions like eczema and asthma, as well as blood diseases.
Follow Allison Gatlin on Twitter at @IBD_AGatlin.
