Sanofi’s partnership with Regeneron Pharmaceuticals yielded Dupixent, whose approvals in multiple indications make it one of the top immunology drugs in the world. The pharmaceutical company is now trying to replicate that success, paying $1 billion to broaden the alliance to Regeneron molecules that could become Dupixent’s successors.
Sanofi and Regeneron began collaborating on antibody drug R&D in 2007. The expanded license and collaboration agreement announced Thursday spans four antibody drugs developed from a Regeneron platform technology that generates fully human antibodies. It’s the same technology that produced Dupixent.
Dupixent is a monoclonal antibody designed to block signaling of IL-4 and IL-13, two pathways that drive inflammation. 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. Clinical trials are ongoing that could further expand the drug’s label. For 2025, Sanofi reported €15.7 billion (about $17.6 billion) in global Dupixent revenue, making it the pharma company’s top-selling product.
Dosing of subcutaneously injected Dupixent ranges from every two to four weeks. The most advanced Regeneron drug in the expanded partnership is an IL-13-targeting antibody. This long-acting antibody is intended to offer a dosing interval of every three to six months, according to a Sanofi investor presentation. A Phase 1 study is ongoing in atopic dermatitis.
The other three partnered programs are preclinical. A long-acting antibody that hits the same target as Dupixent is being positioned as a successor to the blockbuster drug, according to the presentation. Another program is a long-acting bispecific antibody designed to target IL-4 and IL-3, offering dual blockade in a single molecule. The last program is a long-acting antibody designed to block the IL-4 ligand, not the receptor. This approach could offer the opportunity for dual blockade when used in combination with other long-acting antibodies.
“By deepening our collaboration, we will make rapid progress in creating the next generation of meaningful therapies for patients with immune-mediated diseases, while contributing to Sanofi’s long-term future,” Sanofi CEO Belén Garijo said in a prepared statement.
In the investor presentation, Sanofi projects the four partnered drugs will reach late-stage clinical testing in the 2029 to 2031 time frame. That timing is important because Dupixent’s patents will start expiring in 2031. By then, the landscape for immunology and inflammation drugs should look much different.
A growing list of biotech companies is developing next-generation immunology drugs that could take market share from Dupixent. AbbVie, which for a time had the top-selling drug in the world with the biologic immunology medicine Humira, acquired Apogee Therapeutics earlier this year for $11 billion. The deal brings a long-acting antibody ready for Phase 3 testing in atopic dermatitis. Biotech companies are also progressing with programs that could offer dosing and tolerability advantages over Dupixent.
In a research note, Leerink Partners analyst David Risinger said the expanded collaboration is a good move for both Sanofi and Regeneron ahead of Dupixent’s patent expirations. The early development stage of the partnered programs means it will take a few years to assess their competitive profiles. But Risinger added that it’s important for the companies to launch the new drugs before Dupixent biosimilars enter the market.
Beyond Sanofi’s upfront payment, Regeneron could earn up to $7 billion if the partnered drugs achieve milestones. The deal makes Regeneron responsible for leading R&D work while Sanofi will lead global commercialization. Development and commercialization costs will be split equally.
The two companies will also share equally in profits from sales of any approved products, which is a more favorable arrangement for Regeneron than the current financial terms for Dupixent. While the companies share equally in Dupixent’s U.S. profits, Sanofi currently gets a greater cut of profits from the drug’s sales outside the U.S. In 2024, Regeneron sued Sanofi alleging the pharma company breached the collaboration agreement by failing to provide full access to information about Dupixent’s commercialization. The companies said Thursday that this litigation has been settled. They added that the profit-sharing agreement for Dupixent remains unchanged.
One Sanofi drug could become part of the expanded collaboration. The agreement gives Regeneron the option to collaborate on lunsekimig, a bispecific antibody that targets TSLP and IL-13. Regeneron may exercise this option after the Sanofi drug completes Phase 3 tests in chronic obstructive pulmonary disease.
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