Sanofi's stock is down. Its sclerosis drug suffers 'double blow'

Sanofi shares fell on December 15 after the company's experimental drug for the treatment of multiple sclerosis faced two problems at once, Reuters writes: the late-stage clinical trials of the drug failed to achieve a key goal, and the U.S. regulator made it clear that the decision on the approval of the drug will again be delayed. Against this background, Sanofi's shares fell in price, and analysts warned that the setbacks could undermine confidence in the company's portfolio of drugs under development.

Shares of French pharmaceutical company Sanofi fell in Paris on December 15 by 2% on the news that the U.S. regulator postponed the decision on the approval of the company's experimental drug for the treatment of multiple sclerosis. The pharma giant's securities were also affected by disappointing results of late-stage clinical trials of its drug, Reuters writes.

At the beginning of trading on December 15, Sanofi securities fell by more than 5%, falling to the bottom of the index SBF 120 - an indicator of the most traded stocks in Paris - but then partially recovered losses. Since the beginning of the year Sanofi quotes have fallen by more than 13%.

Quotes were affected, among other things, by Sanofi's announcement on December 15 that its experimental drug for the treatment of multiple sclerosis - tolebrutinib - failed to meet the primary objective in a late-stage clinical trial, writes The Wall Street Journal (WSJ). Specifically - it did not show a slowing of patient deterioration in primary progressive multiple sclerosis. In this regard, the company decided not to apply for registration of the drug for this form of the disease, which is characterized by slow but persistent deterioration of neurological function without periods of improvement, the company said in a release.

Separately, Sanofi said that talks with the U.S. Food and Drug Administration showed that regulatory review of the drug for another form of the disease will take longer than previously expected. This is the second postponement by the U.S. regulator in relation to the drug Sanofi: initially a regulatory decision was expected in September, Reuters points out. The company expects to receive additional clarifications from the U.S. regulator by the end of the first quarter of 2026. Before the latest clinical trial results were published, analysts estimated that tolebrutinib had a chance of gaining regulatory approval in the US in Europe and reaching sales of more than €1 billion ($1.08 billion) by 2030, according to consensus forecasts from analysts at Visible Alpha.

"We are disappointed with today's results; however, we believe they will improve our understanding of the basic biology of multiple sclerosis," said Hooman Ashrafian, executive vice president, head of research and development at Sanofi.

At the same time, Sanofi said it remains confident in the potential of tolebrutinib to treat another form of the disease - secondary progressive multiple sclerosis without exacerbations, where relapses stop but symptoms continue to increase.

The company also noted that the results of the studies may require a reassessment of the value of the tolebrutinib asset and a possible write-down of a portion of it. However, Sanofi emphasized that such an adjustment would have no impact on net operating income, cleared of one-off factors, and the outlook for 2025 remains unchanged.

Amid Sanofi's attempts to overcome a series of recent disappointments in drug clinical trials, the latest reports are a blow to one of the most advanced drugs in Sanofi's pipeline, the WSJ points out.

Analysts polled by Reuters said the setbacks could undermine confidence in Sanofi's portfolio of drugs in development after weak results for experimental treatments for eczema and "smoker's lung" that the company reported earlier this year. Sanofi's shares are under pressure due to the company's need to diversify its sources of growth beyond its most popular drug at the moment, asthma remedy Dupixent.

Bank of America analysts also note that the delay in the regulator's decision on the sclerosis drug casts doubt on projected peak sales of tolebrutinib of €1.4 billion.

Jefferies analysts at the same time noted that the greatest commercial potential of the drug tolebrutinib is related specifically to the secondary progressive form of multiple sclerosis and that it is too early to talk about Sanofi's failure. "The market may write this asset off, but in our view this is premature. It is possible that further pressure on quotations will also increase pressure on the company's management," the analysts said in a commentary quoted by Morning Star.

In July 2025, the drug tolebrutinib was temporarily approved for use in the United Arab Emirates to treat a form of multiple sclerosis in which the disease progresses gradually without exacerbations. The drug is now being reviewed by regulators in the European Union and the United States, Reuters specifies . In December 2024, the US regulator gave Sanofi's multiple sclerosis drug a "priority review" status. The U.S. regulator will revisit the review of Sanofi's drug on December 28.

This article was AI-translated and verified by a human editor