Sanofi announced on Mar. 23 a new partnership with California-based Kali Therapeutics to develop a tri-specific antibody aimed at treating autoimmune disorders. The agreement includes $180 million in upfront and near-term payments for Kali's KT501, as well as up to $1.05 billion in potential development and commercial milestone payments. Kali will also be eligible for tiered royalties on sales.
The collaboration highlights Sanofi's ongoing focus on immunology, an area that has seen significant investment from the company recently. This deal is part of Sanofi's broader strategy to expand its presence in treatments targeting immune-related diseases.
KT501 is described as an IgG-like tri-specific antibody designed to target CD3 on T cells and both CD19 and BCMA on B cells, which allows it to address a wide range of B cell populations. According to the announcement, the therapy uses proprietary masking technology intended to maximize potency while reducing cytokine release—a factor that can pose safety risks in such treatments.
Currently, KT501 is being evaluated in its first human study focused on rheumatoid arthritis, where researchers are assessing its safety, tolerability, pharmacokinetics, and pharmacodynamics. Kali reported dosing the first patient last week but did not specify which additional indications Sanofi may pursue under this partnership.
This agreement follows other recent moves by Sanofi in the immunology space. Earlier this month, the company entered into a collaboration with Hong Kong’s Sino Biopharmaceutical for rovadicitinib—an oral drug that blocks JAK and ROCK pathways—committing up to $1.395 billion in milestones after an initial payment of $135 million. In December 2025, Sanofi expanded its relationship with Dren Bio through deals worth over $3 billion combined for targeted myeloid engager therapies and B cell depleters.
