Astellas US LLC et al. v. Dr Reddys Laboratories Ltd

Case Overview: Astellas Defends Blockbuster Prostate Cancer Drug Xtandi® from Generic Competition

In a high-stakes pharmaceutical patent dispute, a consortium of Astellas entities, including Astellas US LLC and Medivation Prostate Therapeutics LLC, has sued Dr. Reddy's Laboratories Ltd., a major Indian multinational generics manufacturer. The lawsuit, filed on April 17, 2026, in the U.S. District Court for the District of New Jersey, is a direct response to Dr. Reddy's filing of an Abbreviated New Drug Application (ANDA) with the FDA seeking approval to market generic versions of Astellas's blockbuster prostate cancer drug, Xtandi® (enzalutamide) in 40 mg and 80 mg tablet forms. This type of litigation is common under the Hatch-Waxman Act, where a brand-name drug manufacturer sues a generic applicant for patent infringement, triggering an automatic 30-month stay on the FDA's approval of the generic product while the case is litigated. The plaintiffs are operating companies engaged in the development and commercialization of pharmaceutical products, while the defendant is a prominent global producer of generic drugs.

The litigation centers on four U.S. patents that Astellas asserts protect Xtandi® from generic competition. The patents cover various aspects of the drug product, reflecting a common "evergreening" strategy to extend market exclusivity for a highly profitable drug. The patents-in-suit are:

• U.S. Patent No. 12,161,628: Covers a dosage regimen for co-administering enzalutamide with another specific drug.
• U.S. Patent No. 12,447,128: Relates to specific formulations of enzalutamide designed to improve its properties.
• U.S. Patent No. 12,502,357: Also relates to novel formulations of the active ingredient enzalutamide.
• U.S. Patent No. 11,839,689: Describes solid formulations of enzalutamide, including in an amorphous state, to improve solubility and absorption.

The case (No. 3:26-cv-04101) is being heard in the District of New Jersey, a premier venue for patent litigation, particularly for ANDA cases. The district is known for its experienced judiciary, specialized local patent rules, and its proximity to the headquarters of numerous pharmaceutical companies, making it a strategic choice for both brand and generic drug litigants. This case is notable due to the significant market value of Xtandi®, which generated global sales of approximately $6 billion for Astellas in fiscal year 2025. The litigation represents a critical effort by Astellas to defend a key revenue stream as the drug approaches its "patent cliff." The suit is part of a broader, global legal strategy by Astellas, which has been enforcing its Xtandi® patent portfolio against multiple generic challengers in Europe as well.

Key Legal Developments & Case Status

As of May 1, 2026, the litigation is in its earliest stage, having been filed just two weeks prior. Key developments are limited to the initial complaint and procedural preliminaries.

Chronological Developments:

• 2026-04-17: Complaint Filed: Astellas and its co-plaintiffs filed a 75-page complaint for patent infringement against Dr. Reddy's Laboratories Ltd. ("DRL") in the District of New Jersey. The complaint alleges that DRL infringed the four patents-in-suit by submitting Abbreviated New Drug Application (ANDA) No. 220556 to the U.S. Food and Drug Administration (FDA). DRL's ANDA seeks approval to manufacture and sell generic versions of Astellas's Xtandi® (enzalutamide) 40 mg and 80 mg tablets prior to the expiration of the asserted patents. The lawsuit was triggered by a Paragraph IV certification notice letter sent by DRL, in which DRL asserted that the patents-in-suit are invalid, unenforceable, or will not be infringed by DRL's proposed generic products. The filing of this suit within 45 days of receiving the Paragraph IV notice automatically triggers a 30-month stay of FDA approval for DRL's ANDA, likely pushing any potential generic launch into late 2028, pending the outcome of this litigation.

• 2026-04-18: Summons Issued: The Clerk of the Court issued a summons for the defendant, Dr. Reddy's Laboratories Ltd.

• Current Status: The case is currently pending service of the complaint and summons on the defendant. As Dr. Reddy's Laboratories Ltd. is an Indian corporation, service will likely proceed under the Hague Convention, which can be a time-consuming process. The defendant has not yet filed an answer or any other responsive pleading. No judge has been assigned to the case, and no initial scheduling conference has been set.

Parallel PTAB Proceedings:

As of May 1, 2026, a search of the U.S. Patent and Trademark Office's Patent Trial and Appeal Board (PTAB) docket reveals that Dr. Reddy's Laboratories has not yet filed any petitions for inter partes review (IPR) against the four asserted patents. It is a common strategy for ANDA filers to challenge the validity of asserted patents at the PTAB in parallel with district court litigation, so such filings may occur as the case progresses. The absence of any IPRs at this early stage is not unusual.

Plaintiffs' Counsel of Record

As of May 3, 2026, the initial complaint filed on April 17, 2026 (D.I. 1) identifies the following attorneys from Sidley Austin LLP and Williams & Connolly LLP as counsel for the plaintiffs Astellas US LLC, Medivation AG, Astellas Pharma Inc., and Medivation Prostate Therapeutics LLC. No formal appearances have been entered on the docket beyond the signatures on the complaint, but the attorneys listed are expected to represent the plaintiffs.

Sidley Austin LLP

• Thomas D. Rein (Lead Counsel): Partner at Sidley Austin's Chicago office. Rein is a veteran patent litigator with extensive experience in pharmaceutical cases, having previously represented major drugmakers in Hatch-Waxman litigation.
• Ching-Lee Fukuda (Of Counsel): Partner in Sidley Austin's New York office. Fukuda has a strong record in life sciences patent litigation, including representing Astellas in prior ANDA litigation over Xtandi®.
• Nathan R. Luber (Of Counsel): Counsel in Sidley Austin's Chicago office. Luber focuses his practice on pharmaceutical patent litigation and has been involved in previous cases defending brand-name drugs from generic challenges.

Williams & Connolly LLP

• David M. Berl (Lead Counsel): Partner at Williams & Connolly's Washington, D.C. office. Berl is a seasoned trial lawyer who has represented major pharmaceutical companies in high-stakes patent disputes, including previous successful defenses of blockbuster drugs.
• Jessica E. Ryen (Of Counsel): Associate in Williams & Connolly's Washington, D.C. office. Her practice focuses on patent litigation, often in the pharmaceutical sector.

Local Counsel

The complaint does not yet list a New Jersey-based attorney as local counsel. Pursuant to Local Civil Rule 101.1, an appearance by an attorney from the District of New Jersey is expected to be filed shortly. The specific local counsel has not yet been identified on the public docket.

Defendant's Counsel of Record Not Yet Available

As of May 4, 2026, counsel for the defendant, Dr. Reddy's Laboratories Ltd. ("DRL"), has not yet filed a notice of appearance in this case. The docket for case number 3:26-cv-04101 in the District of New Jersey does not show any filings by the defendant or any attorneys representing them.

The complaint was filed on April 17, 2026, and a summons was issued the following day. Given that DRL is an Indian corporation, the process of serving the complaint and summons is governed by international agreements, such as the Hague Convention, which typically takes longer than domestic service. It is therefore not unusual for an appearance to be delayed in the initial weeks of such a case.

While no attorneys have formally appeared, DRL frequently retains specialized outside counsel for its Hatch-Waxman ANDA litigation. Law firms known to have represented DRL in prior, similar patent cases include Pillsbury Winthrop Shaw Pittman LLP and the former Budd Larner Rosenbaum Greenberg & Sade.

Additionally, DRL maintains an in-house intellectual property legal team to manage such litigation. Key in-house counsel at DRL with responsibility for patent litigation include:

• Jeffrey Martin: Senior Director, Legal Counsel - Intellectual Property. Martin has extensive experience in ANDA and biosimilar litigation from both his current in-house role and prior positions at law firms.

It is expected that DRL will retain both national and local New Jersey counsel, who will file appearances in the coming weeks or months after service is perfected. Until then, no attorneys are officially on record for the defendant.