Sanofi posts results across four trials; RSV toddler study OPAL ended early by sponsor decision

Sanofi posted results this week for four completed or terminated trials spanning urticaria, RSV prevention, and influenza vaccination.

• **Rilzabrutinib (SAR444671) in chronic spontaneous urticaria**: This Phase 2 trial tested three oral doses of rilzabrutinib against placebo over 12 weeks in patients with moderate-to-severe chronic spontaneous urticaria who remained symptomatic despite H1 antihistamine treatment.¹ The study enrolled 160 participants¹ and used change from baseline in weekly Urticaria Activity Score (UAS7) at Week 12¹ as a primary outcome, with results posted August 6, 2026.
• **RSV vaccine candidate (LNP-based, Phase I/IIa)**: This trial evaluated a single intramuscular injection of three dose-levels of an RSV vaccine candidate formulated with two different lipid nanoparticles in adults aged 18 to 50 and 60 and older². The study, sponsored by Sanofi Pasteur, enrolled 865 participants² and completed May 2, 2025, with results posted August 5, 2026.
• **Quadrivalent influenza mRNA vaccines (MRT5421, MRT5424, MRT5429)**: This Phase I/II study compared a single intramuscular injection of different mRNA formulations of quadrivalent influenza vaccine against active controls including standard-dose, high-dose, and recombinant influenza vaccines in adults 18 and older³. Sponsored by Sanofi Pasteur, the trial enrolled 908 participants³ and completed June 9, 2025, with results posted August 4, 2026.
• **Intranasal RSV vaccine for infants and toddlers (OPAL)**: This Phase III trial, sponsored by Sanofi Pasteur, was terminated for sponsor decision after enrolling 42 healthy children aged 6 months to under 22 months⁴. The study aimed to evaluate non-inferiority of a lower-dose RSV vaccine compared to standard dose, and assess safety of low, standard, and high doses given intranasally versus placebo⁴, with results posted August 3, 2026.