Kadmon and Sanofi Sue MSN, Natco, and Hetero Over Generic Rezurock Belumosudil ANDAs.

The case

The case is Kadmon Corp., LLC v. MSN Pharms. Inc., No. 3:26-cv-14005-GC-TJB (D.N.J.), filed October 27, 2026. The case number on the filed complaint carries the initials GC-TJB, for Judge Georgette Castner and Magistrate Judge Tonianne J. Bongiovanni. Plaintiffs are Kadmon Corporation, LLC (Delaware), Kadmon Pharmaceuticals, LLC (Pennsylvania), and sanofi-aventis U.S. LLC (Delaware), each described as an indirect wholly-owned subsidiary of Sanofi, a French company. The complaint says Kadmon Pharmaceuticals filed NDA No. 214783 for Rezurock (belumosudil) tablets for oral use, which FDA approved on July 16, 2021 for adult and pediatric patients 12 years and older with chronic graft-versus-host disease after failure of at least two prior lines of systemic therapy.

The drug and the patents

The complaint asserts U.S. Patent 12,097,202, titled "Methods of Administering Belumosudil for Treatment of Chronic Graft Versus Host Disease," issued September 24, 2024 to Kadmon Corporation, and U.S. Patent 12,766,143, titled "Method of Administering Belumosudil for Treatment of Chronic Graft Versus Host Disease," issued October 20, 2026 to Kadmon Corporation. It says claims 2, 5, and 6 of the '202 patent were disclaimed on April 3, 2025; supplemental examination was requested May 7, 2025; ex parte reexamination was ordered June 5, 2025; and a reexamination certificate issued January 30, 2026 containing an amended claim 1. The complaint says Kadmon Corporation owns both patents and that sanofi-aventis is the exclusive licensee of each under an agreement with Kadmon Corporation. It says the '202 patent is listed in the Orange Book for Rezurock and that patent information for the '143 patent was timely submitted for Orange Book listing within 30 days of issuance.

U.S. Patent 12,097,202 covers methods of treating chronic graft-versus-host disease by administering a daily dose equivalent to 200 mg free base of 2-{3-[4-(1H-indazol-5-ylamino)-2-quinazolinyl]phenoxy}-N-(propan-2-yl) acetamide or a pharmaceutically acceptable salt, identifying a treatment-related infection adverse reaction, ceasing administration when that infection is at Grade 3 (IV antibiotic, antifungal, antiviral, radiological, or operative intervention indicated), and resuming the previously administered daily dose when the infection has recovered to Grade 1 or less (intervention not indicated). Claim 1, as amended by the January 30, 2026 reexamination certificate, covers that method of treating cGVHD in a patient in need thereof with those administering, identifying, ceasing, and resuming steps for a treatment-related infection.

U.S. Patent 12,766,143 covers methods of treating chronic graft-versus-host disease by administering a daily dose equivalent to 200 mg free base of the same Compound, ceasing administration when the patient experiences a treatment-related infection that is Grade 3 under Common Terminology Criteria for Adverse Events (CTCAE), and resuming the previously administered daily dose when the infection has recovered to Grade 1 or less under CTCAE. Claim 1 covers that method. The complaint says claims 1 and 19 are the only independent claims, with claims 2-18 depending from claim 1 and claim 20 depending from claim 19.

The ANDAs and the notice letters

The complaint names three Abbreviated New Drug Applications seeking approval before the patents expire: MSN ANDA No. 220840 for "belumosudil tablets, 200 mg"; Natco ANDA No. 220781 for "belumosudil mesylate, oral tablet"; and Hetero ANDA No. 220751 for "Belumosudil Mesylate Tablets Eq. 200mg Base; Oral." It says notice letters dated August 28, 2025 (MSN), September 11, 2025 (Natco), and September 19, 2025 (Hetero) each advised that the ANDA included a certification under 21 U.S.C. 355(j)(2)(B)(iv) that, in that defendant group's opinion, certain claims of the '202 patent are invalid, unenforceable, and/or will not be infringed. By letters dated October 20, 2026, plaintiffs informed each defendant group that the '143 patent had issued and would be submitted for Orange Book listing and that, on information and belief, use of each generic product according to its proposed labeling would infringe the '143 patent claims. On information and belief, each ANDA seeks the same chronic GVHD indication as the Rezurock label.

The counts

Each defendant group faces four counts: infringement of the '202 patent, a declaratory judgment of infringement of the '202 patent, infringement of the '143 patent, and a declaratory judgment of infringement of the '143 patent. Counts I through IV run against the MSN Defendants, Counts V through VIII against the Natco Defendants, and Counts IX through XII against the Hetero Defendants. The infringement counts allege an act of infringement under 35 U.S.C. 271(e)(2)(A) from the ANDA submissions. The complaint alleges, on information and belief, that each generic product's proposed labeling will be substantially identical to the Rezurock label, which instructs 200 mg once-daily administration and dosage modification for adverse reactions, and that the labeling will induce infringement under 271(b) after approval. The declaratory-judgment counts rest on 28 U.S.C. 2201 and 2202. The complaint reproduces claim 1 of each patent and says claim 1 is the only independent claim of the '202 patent, with all other claims depending from it. It alleges the case is exceptional.

The relief sought

As to each defendant group, the prayer seeks judgment of infringement under 35 U.S.C. 271(e)(2)(A) and 271(b); permanent injunctions under 35 U.S.C. 271(e)(4)(B) and/or 283 barring commercial manufacture, use, offer for sale, sale, and/or importation before patent expiration (inclusive of extensions); orders under 35 U.S.C. 271(e)(4)(A) that the effective date of any FDA approval of each ANDA be no earlier than the expiration of each patent, inclusive of extensions; judgment that the patent claims remain valid and enforceable; damages with costs and interest if commercial launch occurs before expiration; a declaration that the case is exceptional with reasonable attorneys' fees under 35 U.S.C. 285; costs and expenses; and other just relief.

What to watch next

Watch for answers or Rule 12 motions from the MSN, Natco, and Hetero defendant groups, any motion practice on the newly issued '143 patent and Orange Book listing, and scheduling of a Hatch-Waxman case-management order before Judge Castner.