Sanofi's MS Drug Shows Promise, Aims for $5B Peak Sales

Sanofi has achieved a significant milestone with its anti-CD40L antibody, frexalimab, for the treatment of multiple sclerosis (MS). The drug's efficacy was confirmed in a Phase II study, the results of which were published in The New England Journal of Medicine. The study demonstrated a marked reduction in disease activity among individuals suffering from relapsing MS after being administered frexalimab.

In December 2023, Sanofi highlighted frexalimab as one of its key assets with the potential to achieve peak annual sales exceeding 5 billion euros. This optimism stems from the positive Phase II data that were initially announced in May 2023.

The NEJM publication presented a comprehensive review of the Phase II outcomes. A total of 129 MS patients were randomly assigned to receive either a placebo or frexalimab, administered through intravenous or subcutaneous routes. The primary focus of the study was on the antibody's impact on gadolinium-enhancing T1-lesions, indicative of active inflammation within the body.

By the 12th week, the adjusted average count of new gadolinium-enhancing T1-weighted lesions was significantly lower in both the intravenous and subcutaneous frexalimab groups, compared to the placebo group. This outcome was statistically significant, meeting the study's primary goal.

Sanofi also reported that frexalimab contributed to a decrease in another category of lesions. The counts remained minimal for patients who continued treatment up to the 24th week and showed a decline in those who switched from placebo to the antibody post-week 12. However, there was no significant impact on MSIS-29, a measure of MS's effect on patients, which was an exploratory endpoint.

The French pharmaceutical company has initiated Phase III trials to further evaluate the drug's clinical efficacy. In December 2023, they began enrolling 1,400 relapsing MS patients in one such trial, aiming to assess the drug's effect on the annualized relapse rate with results expected in 2027. Additionally, a second Phase III trial has commenced, focusing on nonrelapsing secondary progressive MS patients.

The Phase III results will be pivotal for Sanofi's ambition to make frexalimab a leading drug in its market segment. Originally licensed from ImmuNext in 2017, Sanofi has been developing frexalimab to harness the therapeutic potential of the CD40 pathway. This approach had previously been explored by Biogen and Idec, but their efforts were halted due to safety concerns regarding blood clots.

It is noteworthy that no participant in Sanofi's Phase II trial experienced thromboembolic events. This has bolstered the company's confidence, with CEO Paul Hudson expressing his belief that frexalimab is poised to enter a receptive market.

The development and testing of frexalimab represent a significant step forward in the treatment of MS, with the potential to offer a new therapeutic option for patients. The upcoming Phase III trials will provide crucial insights into the drug's long-term safety and efficacy, which will be instrumental in determining its future as a potential blockbuster treatment.