Soleno and Neurocrine Sue Alvogen Over a Generic Vykat XR Diazoxide Choline ANDA.

The case

The case is Soleno Therapeutics Inc. and Neurocrine Biosciences, Inc. v. Alvogen, Inc., No. 1:26-cv-01365 (D. Del.), filed October 22, 2026, and assigned to Judge Maryellen Noreika. The plaintiffs are Soleno Therapeutics Inc., which the complaint says holds various exclusive rights in the asserted patents and holds New Drug Application No. 216665 for VYKAT XR, and Neurocrine Biosciences, Inc., which the complaint identifies as the owner of the asserted patents. The complaint says Neurocrine completed its acquisition of Soleno on May 18, 2026. The defendant is Alvogen, Inc. The claims arise under 35 U.S.C. 271(e)(2).

The drug and the patents

VYKAT XR (diazoxide choline) is an extended-release oral tablet, in 25 mg, 75 mg, and 150 mg strengths, that FDA approved on March 26, 2025, under NDA No. 216665, for the treatment of hyperphagia in adults and pediatric patients 4 years of age and older with Prader-Willi syndrome. The complaint says FDA granted the product Breakthrough Therapy designation and Orphan Drug exclusivity, that Soleno has marketed it since April 2025, and that it holds New Product exclusivity until March 26, 2028, and Orphan Drug exclusivity until March 26, 2032. The complaint asserts five patents listed in the Orange Book for VYKAT XR: U.S. Patent 7,799,777, Salts of potassium ATP channel openers and uses thereof, issued September 21, 2010; 9,757,384, Methods for treating subjects with Prader-Willi syndrome or Smith-Magenis syndrome, issued September 12, 2017; 12,178,823 and 12,343,348, both under that same title, issued December 31, 2024, and July 1, 2025, respectively; and 12,419,895, Methods for treating subjects with Prader-Willi syndrome, issued September 23, 2025. The Orange Book use codes the complaint lists for the four method patents are reducing hyperphagic aggressive behaviors in Prader-Willi syndrome patients (the '384 and '823 patents), treating hyperphagia and reducing hyperphagic aggressive behaviors (the '348 patent), and treating hyperphagia and reducing food-related behaviors (the '895 patent). Google Patents lists an adjusted expiration date of March 5, 2029, for the '777 patent and an anticipated expiration date of November 12, 2035, for the other four.

USPTO assignment records list Soleno Therapeutics, Inc. as the most recent recorded assignee of all five asserted patents, under an assignment from Essentialis, Inc. executed November 25, 2025, and recorded December 3, 2025 (reel 73832, frame 0312). The complaint describes Essentialis as Soleno's predecessor and alleges that Neurocrine owns the patents.

Claim 1 of the '777 patent, as recited in the complaint, covers crystalline form B of 7-chloro-3-methyl-2H-1,2,4-benzothiadiazine dioxide:2-hydroxy-N,N,N-trimethyl ethanaminium (1:1) salt having characteristic peaks in an XRPD pattern substantially as shown in FIG. 13(b). The complaint also recites claim 35, covering a pharmaceutical composition comprising an effective amount of that crystalline form B of one of claims 1-7. Claim 1 of the '384 patent covers a method of reducing one or more aggressive behaviors in a subject having Prader-Willi syndrome or Smith-Magenis syndrome by administering for at least 10 weeks a pharmaceutical formulation comprising an effective amount of diazoxide or a pharmaceutically acceptable salt thereof, wherein administration reduces one or more aggressive behaviors. Claim 1 of the '823 patent covers a method of treating a subject having Prader-Willi Syndrome by administering for at least 10 weeks a pharmaceutical formulation comprising an effective amount of diazoxide or a pharmaceutically acceptable salt thereof, wherein administration reduces one or more aggressive behaviors. Claim 1 of the '348 patent covers a method of treating hyperphagia in a subject having Prader-Willi Syndrome by orally administering once per day a pharmaceutical formulation comprising an effective amount of diazoxide choline, wherein administration reduces hyperphagia and one or more aggressive behaviors. Claim 1 of the '895 patent covers a method of treating hyperphagia in a subject having Prader-Willi Syndrome by administering once per day a pharmaceutical formulation comprising an effective amount of diazoxide choline, wherein administration reduces hyperphagia and one or more food related behaviors; the complaint also recites claim 16, which depends from claim 1 and requires titration from a starting dose every two weeks to a maintenance dose.

The ANDA and the notice letter

The complaint alleges that Alvogen submitted ANDA No. 221658 seeking approval to manufacture, use, sell, offer for sale, and/or import purported generic versions of VYKAT XR 25 mg, 75 mg, and 150 mg extended-release tablets before the asserted patents expire, and that, on information and belief, FDA has not approved that ANDA. It alleges Alvogen's ANDA includes proposed labeling for the treatment of hyperphagia in adults and pediatric patients four years of age and older with Prader-Willi syndrome, matching VYKAT XR's indication, and that Alvogen did not submit a statement under 21 U.S.C. 355(j)(2)(A)(viii) seeking to carve out patented uses. According to the complaint, Alvogen sent Soleno a notice letter dated September 8, 2026, which Soleno received on September 9, 2026, representing that the ANDA included Paragraph IV certifications with respect to each of the asserted patents. The complaint states this action was brought within 45 days of receipt of the notice letter and that plaintiffs are entitled to a stay of FDA approval under 21 U.S.C. 355(j)(5)(B)(iii) until March 9, 2029.

The counts

Counts 1 through 5 assert infringement of the '777, '384, '823, '348, and '895 patents, respectively, under 35 U.S.C. 271(e)(2)(A) based on submission of the ANDA with Paragraph IV certifications. Count 1 alleges infringement of at least claims 1 and 35 of the '777 patent. Counts 2 through 4 allege infringement of at least claim 1 of the '384, '823, and '348 patents. Count 5 alleges infringement of at least claim 16 of the '895 patent (which depends from claim 1). Count 1 also alleges that commercial manufacture, use, sale, offer for sale, or importation of the Alvogen ANDA Products before the '777 patent expires would directly infringe it, and that Alvogen would induce and contribute to infringement. Counts 2 through 5 allege that prescribers following Alvogen's proposed labeling would directly infringe the method patents and that Alvogen would induce and contribute to that infringement. Each count alleges that Alvogen's conduct in certifying invalidity and/or noninfringement renders the case exceptional under 35 U.S.C. 285.

The relief sought

The prayer asks for a judgment that Alvogen has infringed the Asserted Patents under 35 U.S.C. 271(e)(2)(A); an order under 35 U.S.C. 271(e)(4)(A) that the effective date of any FDA approval of Alvogen's ANDA be no earlier than the latest expiration date of the Asserted Patents, including any additional exclusivity; a judgment under 35 U.S.C. 271(a), (b), and/or (c) that making, using, selling, offering to sell, or importing the ANDA products, or inducing or contributing to such conduct, would constitute infringement; a permanent injunction under 35 U.S.C. 271(e)(4)(B) and 283 until the day after patent expiry including exclusivity; damages or other relief under 35 U.S.C. 271(e)(4)(C) if commercial activity occurs before expiry; a finding that the case is exceptional with attorneys' fees under 35 U.S.C. 285; costs and expenses; and other relief.

What to watch next

Watch for Alvogen's answer or Rule 12 motion, a District of Delaware Hatch-Waxman schedule, and the stay of FDA approval that the complaint says runs until March 9, 2029. The case can end at any time, including by settlement or voluntary dismissal.