Kali Therapeutics’ T cell engager, for which Sanofi is initially paying $180 million, could potentially be developed for a range of B cell–driven autoimmune disorders.
Sanofi is partnering with California’s Kali Therapeutics to advance a tri-specific antibody targeting autoimmune disorders, continuing the pharma’s recent dealmaking spree in the immunology space.
Sanofi is putting down $180 million in upfront and near-term payments for Kali’s KT501, a novel T cell engager, according to a Monday news release. The pharma has also committed up to $1.05 billion in development and commercial milestones. Kali, meanwhile, will also be eligible to receive tiered royalties on sales in the high-single to double-digit range.
KT501 is an IgG-like tri-specific antibody that works by targeting CD3 on T cells and CD19 and BCMA on B cells—a binding profile that Kali claims on its website enables the targeting of a broad range of B cell populations. The asset also makes use of a proprietary masking technology that maximizes its potency while minimizing cytokine release, which otherwise could lead to safety risks.
KT501 is currently being tested in a first-in-human study for rheumatoid arthritis to assess its safety and tolerability as well as its pharmacokinetic and pharmacodynamic profiles. Kali dosed the first patient in this study last week.
It is unclear what indications Sanofi plans to target, but the antibody “has the potential to treat a broad range of B cell–mediated autoimmune diseases,” according to the Monday announcement.
Kali is the latest pickup in Sanofi’s recent immunology partnership push. Earlier this month, the pharma dropped an upfront sum of $135 million to collaborate with Hong Kong’s Sino Biopharmaceutical, gaining the right to advance and commercialize the oral drug rovadicitinib worldwide. Sino will be eligible for up to $1.395 billion in milestones.
As in the case of Kali, Sanofi has yet to disclose what indications it plans to address with Sino, but rovadicitinib blocks the JAK and ROCK pathways, which play a role in immune balance.
In December 2025, Sanofi expanded its existing partnership with Dren Bio, betting up to $1.7 billion to leverage the biotech’s targeted myeloid engager and phagocytosis platform. Under the deal, Dren will discover novel multi-specific therapies, which Sanofi will then take forward into the clinic. Months earlier, Sanofi bought a B cell depleter from Dren for $600 million upfront and up to $1.3 billion in milestones.
Two months earlier, Sanofi teamed up with EVOQ Therapeutics, putting up to $500 million on the line to use the biotech’s NanoDisc platform to develop therapies that selectively target dendritic cells.
