FDA Issues CRL to SNY's Regulatory Filing for Multiple Sclerosis Drug

Sanofi SNY announced that the FDA has issued a complete response letter (CRL) to its new drug application (NDA), seeking approval for its investigational Bruton's tyrosine kinase (BTK) inhibitor, tolebrutinib. The NDA sought approval for tolebrutinib to treat adult patients with non-relapsing secondary progressive multiple sclerosis (nrSPMS).

More on FDA’s CRL for Sanofi’s Tolebrutinib

The FDA’s latest CRL for tolebrutinib does not come as a surprise, as earlier this month, the regulatory body extended the review timeline for tolebrutinib in nrSPMS for the second time this year.

Earlier this year, the FDA had extended the review period for Sanofi’s NDA for tolebrutinib in nrSPMS by three months. The FDA was initially expected to give its decision by Sept. 28, 2025. However, this date was extended by an additional three months to Dec. 28 after Sanofi’s submission of additional analyses during the review process, which the agency deemed a major amendment to the original filing.

The agency once again revised this date after the company submitted an expanded access protocol for the drug in nrSPMS at the FDA’s request. Further guidance from the FDA is expected by the end of the first quarter of 2026.

In the past six months, shares of Sanofi have inched up 1.1% compared with the industry’s increase of 20.4%.

In July 2025, tolebrutinib was provisionally approved in the United Arab Emirates for the treatment of nrSPMS and to slow disability accumulation independent of relapse activity in adults. A regulatory filing seeking approval for tolebrutinib for a similar indication is currently under review in the European Union.

SNY's Recent Hurdles With Tolebrutinib Studies

Earlier this month, Sanofi announced that the phase III PERCEUS study, which evaluated tolebrutinib in patients with primary progressive multiple sclerosis (PPMS), did not meet the primary endpoint, in delaying time to onset of six-month composite confirmed disability progression versus placebo.

However, the safety profile of tolebrutinib was similar to that seen with previously conducted studies on the candidate.

Following this, Sanofi decided not to pursue further development of tolebrutinib in PPMS — an area that represents 10% of the overall multiple sclerosis (MS) patient population.

In 2022, the FDA placed a partial clinical hold on Sanofi’s phase III studies on tolebrutinib in MS and myasthenia gravis (MG) indications after the regulatory agency identified cases of drug-induced liver injury in some study participants who were treated with the drug.

The MG studies on tolebrutinib were eventually discontinued in 2022 after careful evaluation of the emerging competitive treatment landscape.

Gets EU Nod for Wayrilz

In a separate press release, Sanofi announced that the European Commission has approved Wayrilz (rilzabrutinib), a novel BTK inhibitor, as a new treatment for immune thrombocytopenia (ITP) in adult patients who are refractory to other treatments.

The approval in the EU was expected, as in October, the European Medicines Agency's Committee for Medicinal Products for Human Use (CHMP) rendered a positive opinion recommending the approval of Wayrilz for the given indication.

The approval in the EU was based on data from the pivotal phase III LUNA 3 study, which showed that treatment with Wayrilz led to a positive impact on sustained platelet counts and other ITP symptoms, thus meeting both the primary and secondary endpoints.

The FDA approved Wayrilz for the treatment of persistent or chronic ITP in adult patients who have had an insufficient response to a previous treatment in August 2025.

SNY's Zacks & Stocks to Consider

Sanofi currently carries a Zacks Rank #3 (Hold).

Some better-ranked stocks in the biotech sector are CorMedix CRMD and Castle Biosciences CSTL, both sporting a Zacks Rank #1 (Strong Buy). You can see the complete list of today’s Zacks #1 Rank stocks here.

In the past 60 days, estimates for CorMedix’s 2025 earnings per share (EPS) have increased from $1.85 to $2.87. EPS estimates for 2026 have moved up from $2.49 to $2.88 during the same period. CRMD stock has decreased 23.8% in the past six months.

CorMedix’s earnings beat estimates in each of the trailing four quarters, with the average surprise being 27.04%.

In the past 60 days, estimates for Castle Biosciences’ loss per share have narrowed from 64 cents to 34 cents for 2025. During the same time, loss per share estimates for 2026 have narrowed from $1.82 to $1.06. In the past six months, shares of CSTL have rallied 109.9%.

Castle Biosciences’ earnings beat estimates in three of the trailing four quarters, while missing the same on the remaining occasion, the average surprise being 66.11%.

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