Sanofi is committing $1 billion to strengthen its alliance with Regeneron Pharmaceuticals, accelerating the development of four new antibody treatments meant to extend the success of Dupixent, its best-selling immunology drug. The expanded partnership leverages Regeneron’s proprietary platform for creating fully human antibodies—the same technology used in Dupixent, which brought in €15.7 billion in revenue last year, making it the pharma company’s top-selling product. First approved by the FDA in 2017 for treating atopic dermatitis, also called eczema, the drug has since received approvals in eight other immunological indications, with additional trials evaluating broader applications.
The agreement, revealed on Thursday, follows a 2007 collaboration between the two firms. Dupixent operates by inhibiting IL-4 and IL-13, critical inflammatory pathways, and has secured approval for nine conditions, including atopic dermatitis, asthma, and eosinophilic esophagitis. The drug’s mechanism involves blocking signaling of these cytokines, which drive inflammation in immune-mediated diseases.
The most developed of the four new candidates is an IL-13-targeting antibody designed for administration every three to six months, a significant improvement over Dupixent’s current dosing schedule of every two to four weeks. A Phase 1 trial in atopic dermatitis is already underway. The remaining three programs remain in preclinical development, including a long-acting version of Dupixent’s mechanism, a bispecific antibody that targets both IL-4 and IL-3 to achieve dual pathway inhibition, and a long-acting antibody designed to block the IL-4 ligand rather than the receptor. This last approach could enable combination therapies for enhanced efficacy.
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Sanofi anticipates these four drugs could enter late-stage testing between 2029 and 2031, aligning with the expiration of Dupixent’s patents. This timing is strategic, as competitors like AbbVie advance their own long-acting immunology treatments. AbbVie’s recent $11 billion purchase of Apogee Therapeutics brought a Phase 3-ready antibody for atopic dermatitis, adding to the growing field of alternatives. The competitive market is evolving rapidly, with biotech firms developing next-generation immunology drugs that could offer dosing and tolerability advantages.
The updated deal shifts financial terms to favor Regeneron. While the two companies split U.S. profits equally for Dupixent, Sanofi holds a larger share in other markets. Under the new terms, profits from the four new drugs will be divided 50-50 worldwide. Regeneron stands to earn up to $7 billion in milestone payments if the programs succeed, while Sanofi will lead commercialization efforts and share development costs equally. The deal also resolves a 2024 lawsuit in which Regeneron had accused Sanofi of withholding commercial data under the original agreement.
