Sanofi has dropped its respiratory syncytial virus (RSV) vaccine for toddlers after the candidate underperformed in a phase 3 study.
The French Big Pharma was evaluating the intranasal live attenuated vaccine, dubbed SP0125, in a late-stage study of about 6,300 children aged between 6 months and 22 months. The study launched last year, according to the federal trials database, and was scheduled to complete at the end of 2027.
But Sanofi—which markets the AstraZeneca-partnered RSV blockbuster Beyfortus—revealed this morning that it has recently terminated the SP0125 program after the study’s independent data monitoring committee (IDMC) decided it was unlikely to demonstrate suitable efficacy.
“The safety profile was acceptable, and no signals of vaccine-associated enhanced respiratory disease were observed by the IDMC,” Sanofi explained in its third-quarter earnings results
At a vaccines R&D day back in 2023, Sanofi had touted SPO125 as the “first RSV vaccine designed to protect toddlers” and referenced “positive phase 1/2 data for the asset.” While the vaccine’s subsequent phase 3 failure may be a blow to Sanofi’s RSV plans, the company has been expanding its presence in the space.
Sanofi already has mRNA vaccines for older adults in the clinic in the form of SP0256, which targets RSV and hMPV, as well as SP0291, which targets RSV, hMPV and PIV3. In July, Sanofi paid $1.15 billion upfront for Vicebio for its non-mRNA vaccine for RSV.
GSK’s Arexvy and Pfizer’s Abrysvo are the top-selling RSV vaccines for older adults and will be joined this RSV season by Moderna’s recently approved mRESVIA.
Meanwhile, Sanofi and AZ’s Beyfortus had an unchallenged spot as the lone prophylactic RSV antibody for children. But that all changed in June when the FDA approved Merck & Co.’s monoclonal antibody Enflonsia to prevent lower respiratory tract disease from RSV in children who are born during or entering their first RSV season.
