Sanofi expanded its autoimmune pipeline by licensing KT501, a tri-specific T-cell engager antibody candidate from Kali Therapeutics. The collaboration gives Sanofi exclusive worldwide rights and includes $180 million in upfront and near-term payments plus up to $1.05 billion in development and commercial milestones, along with tiered royalties. KT501 is designed to bind CD3, CD19, and BCMA using Kali’s CD3 masking platform aimed at separating potency from cytokine release. Kali reported “potent” B-cell depletion and reduced cytokine production in non-human primate studies, supporting a clinical entry for rheumatoid arthritis. Kali said it dosed the first patient in a Phase 1a first-in-human trial (NCT07234773) with estimated primary completion in February 2027. The next catalyst for the program will be early safety/tolerability and pharmacodynamic evidence of B-cell depletion with manageable immune activation.