Sanofi has agreed to license from Kali Therapeutics its lead tri-specific T-cell engager (TCE) antibody candidate KT501, which is being developed to treat a variety of B-cell-mediated autoimmune diseases, through a collaboration that could generate more than $1.23 billion for the San Mateo, CA, biotech.
Sanofi has agreed to obtain exclusive worldwide rights to KT501, which was discovered using Kali’s discovery and research platform. KT501 is an Immunoglobulin G (IgG)-like tri-specific T cell engager that is designed to bind CD3, CD19, and BCMA with high affinity, thereby targeting a broad range of B cell populations.
Using a molecular design aimed at maximizing potency while minimizing cytokine release through a CD3 masking platform technology, KT501 has shown what Kali has termed “potent” B cell depletion and “significantly” reduced cytokine production in non-human primate (NHP) studies.
As a result, Kali said, KT501 shows potential to treat a broad range of B-cell-mediated autoimmune diseases—starting with rheumatoid arthritis, the disease for which KT501 is now under study in a Phase Ia first-in-human trial (NCT07234773).
The open-label, dose escalation trial is designed to assess the drug’s safety, tolerability, pharmacokinetics, and pharmacodynamics in up to approximately 24 participants with rheumatoid arthritis. On March 18, Kali said it dosed the first patient in the Phase I trial, whose estimated primary completion date is February 2027.
“By depleting a broad range of B cell populations effectively while minimizing cytokine release, we believe KT501 can address significant unmet needs of autoimmune patients,” Kali Therapeutics CEO Weihao Xu said in a statement. “We are confident that Sanofi’s extensive expertise will accelerate the development of this promising therapy.”
Investors responded to news of the Kali collaboration by sending Sanofi shares traded on Euronext Paris down 1% Monday, from €77.79 ($90.42) to €76.83 ($89.12).
Sanofi agreed to pay privately-held Kali $180 million in upfront and near-term payments, plus up to a total of $1.05 billion in payments tied to achieving development and commercial milestones, as well as tiered royalties on product sales ranging from the high-single to double digits.
“This collaboration highlights the potential of our unique CD3 masking technology to decouple potency from toxicity, aiming to provide safer, more effective options for patients,” Xu added.
Looking beyond Dupixent
Kali is the latest of several immunology and inflammation (I&I) drug developers with which Sanofi has launched collaborations in recent months.
Sanofi’s I&I pipeline has long been anchored by Dupixent® (dupilumab) co-marketed with Regeneron Pharmaceuticals, but the blockbuster drug is set to lose exclusivity for key U.S. patents starting in 2030. Dupixent finished 2025 with €15.714 billion ($18.253 billion) in global net sales as recorded by Sanofi.
Through the Kali deal, the pharma giant is expanding its presence in TCEs, as it did in 2022 when Sanofi acquired Amunix for up to $1.225 million in upfront and milestone payments.
However, three years later, Sanofi licensed three of Amunix’s TCE programs developed via the PRO-XTEN® platform to Vir Biotechnologies for up to $1.986 billion. Last month, Vir agreed to partner with Astellas Pharma to co-develop and co-commercialize the lead PRO-XTEN TCE program, the prostate cancer candidate VIR-5500, through a collaboration that could generate more than $1.7 billion for Vir.
Last year, Houman Ashrafian, PhD, Sanofi’s executive vice president, head of research and development, articulated the company’s ambition to analysts on the Q4 2024 earnings call: “Sanofi is now becoming a premier immunology powerhouse, and we have network effects internally where we can combine our molecules to generate greater value for patients.”
On March 4, Sanofi secured global rights to develop and commercialize Sino Biopharmaceutical’s rovadicitinib, an oral first-in-class small-molecule inhibitor of the JAK/STAT and ROCK pathways, through an up-to-$1.53 billion partnership consisting of an upfront payment, milestones, and tiered royalties.
Rovadicitinib is approved and marketed in China under the name Anxu® for the first-line treatment of adult patients with intermediate-2 or high-risk primary myelofibrosis (PMF), post-polycythaemia vera myelofibrosis (PPV-MF), or post-essential thrombocythaemia myelofibrosis (PET-MF).
“Emerging leader”
And in December 2025, Sanofi expanded a collaboration with Dren Bio to develop a next-generation B-cell depleting therapy to treat various autoimmune diseases. In return, Sanofi agreed to pay Dren $100 million upfront, up to $1.7 billion in development, regulatory, and commercial milestone payments, plus tiered royalties on ex-U.S. sales.
Sanofi began partnering with Dren in March 2025 when the pharma giant agreed to acquire the San Carlos, CA, biotech’s DR-0201 program for deep B-cell depletion. Sanofi has since renamed the program SAR448501 and has launched two ongoing Phase I studies for the targeted bispecific myeloid cell engager, which, according to Dren, has shown B-cell depletion that was robust enough to suggest it could induce sustained treatment-free remission in patients with autoimmune diseases.
Last October, Sanofi licensed the NanoDisc technology of EVOQ Therapeutics, designed to restore the body’s natural immune tolerance pathways, through an up to $500 million-plus collaboration designed to develop NanoDisc-based curative therapies for multiple autoimmune diseases—citing celiac disease, type 1 diabetes, MOG (myelin oligodendrocyte glycoprotein) antibody disease, rheumatoid arthritis, and lupus.
And in April 2025, Sanofi expanded a partnership with Earendil Labs by acquiring for up to $1.845 billion exclusive worldwide licensing rights to two of Earendil’s bispecific antibodies in autoimmune and inflammatory bowel diseases—HXN-1002, which targets α4β7 and TL1A and is designed to treat moderate to severe ulcerative colitis and Crohn’s disease; and HXN-1003, which targets TL1A and IL23 and is designed to treat colitis and skin inflammation.
“We’re an emerging leader in immunology, poised to transform medicine by rebalancing the immune responses that cause systemic, chronic diseases,” Sanofi declared on its website.
