Legal Dispute Erupts Between Regeneron and Sanofi Over Dupixent Collaboration

Regeneron Pharmaceuticals has filed a lawsuit against its long-time partner Sanofi, alleging violations of their collaboration agreement for the blockbuster drug Dupixent. The legal action, initiated in late November and amended in December, centers on claims that Sanofi has withheld critical commercialization details, particularly regarding pharmacy benefit manager (PBM) contracting information.

Allegations of Transparency Violations

Regeneron asserts that Sanofi has refused to share specific commercialization details, citing concerns about divulging information on other immunology drugs included in payer contracts through product bundling. The lawsuit, filed in New York federal court, contends that this lack of transparency violates the terms of their long-standing partnership, which dates back to 2007.

According to Regeneron's legal team, Sanofi has "stonewalled" repeated requests for full access to PBM agreements. This alleged obstruction has, in Regeneron's view, prevented them from exercising their rights to contribute to key Dupixent commercialization decisions. The situation is described as "commercially unreasonable" given the substantial U.S. sales of Dupixent.

Implications for the Dupixent Collaboration

The collaboration between Regeneron and Sanofi has been crucial in developing and commercializing Dupixent, an antibody treatment approved for multiple indications including atopic dermatitis, asthma, and chronic obstructive pulmonary disease (COPD). Under the current agreement, Sanofi bears the majority of development costs and records Dupixent's sales, while Regeneron retains co-commercialization rights on a country-by-country basis, including in the United States.

Regeneron's lawsuit suggests that Sanofi's reluctance to share PBM deal information may be due to agreements tied to other, non-partnered drugs beyond Dupixent. This raises concerns for Regeneron about potential unfair advantages given to other Sanofi products at Dupixent's expense.

Financial Performance and Future Prospects

Despite the legal dispute, Dupixent continues to perform exceptionally well in the market. In the fourth quarter of 2024, the drug's sales grew 16% to 3.5 billion euros ($3.6 billion), surpassing a full-year sales target of 13 billion euros. Following its recent approval for COPD, some analysts project that Dupixent could reach peak sales of $20 billion.

The timing of this litigation is noteworthy, coming on the heels of Dupixent's strong financial performance and expanded indications. As both companies navigate this legal challenge, the pharmaceutical industry will be watching closely to see how this dispute may impact one of the sector's most successful collaborations and the future of a drug that has become a cornerstone therapy for millions of patients worldwide.