On May 17, 2024, Regeneron filed a second infringement litigation against Celltrion’s proposed EYLEA® (aflibercept) biosimilar CT-P42, Case No. 1:24-cv-00053 (N.D.W. Va.).  The aBLA for CT-P42 was submitted to the FDA in June 2023.  Regeneron’s Complaint listed 25 patents, including 8 patents with method of treatment claims, 5 patents with formulation/composition claims, 4 patents with composition of matter claims, 12 patents with manufacturing claims, one patent with device claims, and one patent with packaging claims.

Regeneron previously filed a lawsuit against Celltrion related to CT-P42 in November 2023, Case No. 1:23-cv-00089 (N.D.W. Va.), alleging infringement of 38 of Regeneron’s patents (previously reported in BPCIA Litigation Related to Proposed Eylea Biosimilar CT-P42 Filed).

The November 2023 lawsuit was filed after Regeneron provided Celltrion with its list of patents in the patent dance, and the May 2024 lawsuit was filed after the parties completed the patent dance and agreed on which patents to litigate.  All of the patents asserted in the May 2024 litigation were previously asserted in the November 2023 litigation.

This is the seventh BPCIA litigation brought by Regeneron against a proposed EYLEA® biosimilar.  It was filed days before the first two interchangeable biosimilars were approved by the FDA, Biocon Biologics and Mylan’s Yesafili™ (aflibercept-jbvf) and Samsung Bioepis’s Opuviz™ (aflibercept-yszy) (previously reported in FDA Approves First Two Interchangeable EYLEA® Biosimilars – Biocon’s Yesafili™ (aflibercept-jbvf) and Samsung Bioepis’s Opuviz™ (aflibercept-yszy)).

Celltrion has also filed an IPR Petition against Regeneron’s U.S. Patent No. 11,253,572 (IPR2024-00260, pending), which has been asserted in both litigations against Celltrion.  Four previous IPRs by Celltrion (IPR2022-00257- U.S. Patent No. 9,669,069; IPR2022-00258- U.S. Patent No. 9,254,338; IPR2023-00532- U.S. Patent No. 10,130,681; IPR2023-00533- U.S. Patent No. 10,888,601) resulted in Final Written Decisions finding all challenged claims unpatentable.  These decisions are currently being appealed to the Federal Circuit.

Regeneron reported EYLEA® sales of $5.89 billion in 2023.

We continue to monitor these cases and will provide updates as they become available. For more information about these and other biosimilar patent disputes, please visit BiologicsHQ.



The authors would like to thank April Breyer Menon for her contributions to this article.


    Information contained in the Venable BiologicsHQ database relates to FDA-approved drug products listed in the CDER Purple Book or on the FDA website ( Information relating to FDA licensed products, FDA-approved indications, and aBLA and 505(b)(2) applications is obtained from public sources including the U.S. FDA website ( Information relating to litigations is given only for cases active from January 31, 2010 onward. Information relating to foreign biosimilar / biologics follow-on products approved in Australia, Canada, the E.U., Japan and South Korea is from public sources. Statistics graphics are compiled from information contained in the Venable BiologicsHQ database.


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