Gilead Sciences Inc v. Macleods Pharma Ltd

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: Gilead Sciences, Inc. (Delaware)
  • Defendant: Macleods Pharmaceuticals Ltd. (India)
  • Plaintiff’s Counsel: Morris, Nichols, Arsht & Tunnell LLP; Gibson, Dunn & Crutcher LLP
• Case Identification: 1:26-cv-00094, D. Del., 01/28/2026
• Venue Allegations: Venue is alleged to be proper because the defendant is a foreign corporation, which may be sued in any judicial district where it is subject to personal jurisdiction.
• Core Dispute: Plaintiff alleges that Defendant’s filing of an Abbreviated New Drug Application (ANDA) to market a generic version of the antiviral drug VEMLIDY® constitutes an act of infringement of two patents related to a specific crystalline salt form of the active ingredient, tenofovir alafenamide.
• Technical Context: The technology concerns a specific hemifumarate salt form of tenofovir alafenamide, an antiviral prodrug used to treat chronic Hepatitis B Virus (HBV) and Human Immunodeficiency Virus (HIV).
• Key Procedural History: This action was initiated under the Hatch-Waxman Act following Defendant’s submission of an ANDA with a Paragraph IV certification, asserting that the patents-in-suit are invalid or will not be infringed by its proposed generic product. The complaint was filed within the 45-day statutory window after Plaintiff received Defendant's notice letter, which triggers an automatic 30-month stay of FDA approval for the generic drug.

Case Timeline

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 8,754,065 - “Tenofovir Alafenamide Hemifumarate,” issued June 17, 2014

The Invention Explained

• Problem Addressed: The patent's background references prior art describing tenofovir alafenamide and a monofumarate salt form of the compound Compl., Ex. A, ’065 Patent, col. 1:16-28 The specification notes that the claimed invention provides advantages over the prior monofumarate form, including improved thermodynamic and chemical stability, better process reproducibility, and an "exceptional capability" to purge a major diastereomeric impurity during manufacturing ’065 Patent, col. 5:4-10; col. 10:36-50
• The Patented Solution: The invention is a specific crystalline salt form of tenofovir alafenamide, known as tenofovir alafenamide hemifumarate, where the molar ratio of fumaric acid to the tenofovir alafenamide base is approximately 0.5 ’065 Patent, col. 2:29-43 The patent characterizes this solid form by its unique X-ray powder diffraction (XRPD) pattern, illustrated in Figure 1 of the patent ’065 Patent, col. 2:46-52
• Technical Importance: The development of a stable, pure, and consistently manufacturable crystalline form of an active pharmaceutical ingredient is critical for drug development, regulatory approval, and commercial-scale production.

Key Claims at a Glance

• The complaint asserts at least independent claim 1 Compl. ¶36
• Independent Claim 1:
  • Tenofovir alafenamide hemifumarate.
• The complaint notes that Plaintiff will identify all asserted claims in accordance with court rules, reserving the right to assert additional claims Compl. ¶36, n.1

U.S. Patent No. 9,296,769 - “Tenofovir Alafenamide Hemifumarate,” issued March 29, 2016

The Invention Explained

• Problem Addressed: The patent, which is a continuation of the application that led to the ’065 patent, addresses the same technical challenges. It specifically highlights the difficulty of removing a key impurity—a diastereomer of tenofovir alafenamide known as GS-7339—when using the previously known monofumarate salt form Compl., Ex. B, ’769 Patent, col. 8:55-62; col. 10:35-50
• The Patented Solution: The invention claims a pharmaceutical composition that contains the tenofovir alafenamide hemifumarate salt but is further defined by its purity. The claims require the composition to contain less than a specified percentage of the corresponding monofumarate salt form, thereby claiming a purer drug substance ’769 Patent, Abstract; col. 4:46-53
• Technical Importance: Controlling the levels of impurities and related substances is a fundamental requirement for pharmaceutical safety and efficacy, and achieving high purity can be a significant non-obvious technical achievement.

Key Claims at a Glance

• The complaint asserts at least independent claim 1 Compl. ¶69
• Independent Claim 1:
  • A composition comprising tenofovir alafenamide hemifumarate,
  • wherein the composition comprises less than about 5% by weight of tenofovir alafenamide monofumarate.
• The complaint reserves the right to assert additional claims Compl. ¶68, n.3

III. The Accused Instrumentality

Product Identification

Defendant’s proposed generic version of VEMLIDY®, identified as the subject of ANDA No. 220967 (the "VEMLIDY ANDA Product") Compl. ¶7, ¶23

Functionality and Market Context

The accused product is a 25 mg tablet intended for treating chronic hepatitis B virus infection in adults with compensated liver disease Compl. ¶18, ¶29 As part of the ANDA process, Defendant has represented to the FDA that its product contains the same active ingredient, has the same dosage form and strength, and is bioequivalent to Gilead's VEMLIDY® product Compl. ¶27 The complaint identifies the active ingredient in VEMLIDY® as tenofovir alafenamide fumarate and provides a structural diagram indicating a hemifumarate salt form Compl. ¶20 The complaint includes a visual diagram depicting the chemical structure of tenofovir alafenamide paired with a half-equivalent of fumaric acid, illustrating the hemifumarate form Compl. ¶20

IV. Analysis of Infringement Allegations

'065 Patent Infringement Allegations

• Identified Points of Contention:
  • Factual Question: The primary question is factual: does the chemical composition manufactured by Defendant and submitted to the FDA for approval meet the definition of "tenofovir alafenamide hemifumarate"? While often a central dispute in ANDA cases, the nature of the ANDA process itself (requiring sameness of active ingredient) may narrow the scope of this disagreement.

'769 Patent Infringement Allegations

• Identified Points of Contention:
  • Technical Question: The infringement analysis will likely depend on analytical chemistry evidence. A key question for the court will be: What is the measured percentage by weight of tenofovir alafenamide monofumarate in the Defendant's proposed product?
  • Scope Questions: What is the scope of the term "about 5%"? This raises the question of whether a product with a measured monofumarate level at or slightly above 5.0% would infringe.

V. Key Claim Terms for Construction

The Term: "hemifumarate" (from ’065 Patent, Claim 1)

• Context and Importance: This term defines the specific stoichiometric salt form of the claimed compound. The infringement and validity analyses will depend on whether this term requires a precise 0.5 molar ratio of fumaric acid to the base compound or if it permits some deviation.
• Intrinsic Evidence for a Broader Interpretation: The specification describes the ratio as "about 0.5" and provides ranges such as "0.5±0.1" and "0.5±0.05," which may support a construction that does not require strict stoichiometric precision ’065 Patent, col. 2:41-43
• Intrinsic Evidence for a Narrower Interpretation: The term "hemi-" has a recognized chemical meaning of "half." A party could argue that in the context of a crystalline solid, this implies a specific, repeating crystal lattice structure consistent with a ratio very close to 0.5, distinguishing it from a physical mixture or other salt forms.

The Term: "about 5% by weight" (from ’769 Patent, Claim 1)

• Context and Importance: This term defines the upper limit of a specified impurity and is therefore central to the question of infringement for the ’769 patent. Practitioners may focus on this term because the difference between an infringing and non-infringing product could be a fraction of a percentage point.
• Intrinsic Evidence for a Broader Interpretation: The use of "about" suggests the patentee did not intend to be limited to a strict numerical cutoff and that the claim covers compositions with impurity levels in the general vicinity of 5%, accounting for manufacturing and measurement variability.
• Intrinsic Evidence for a Narrower Interpretation: The patent does not provide an explicit definition for "about." A party could argue that the term only accounts for standard experimental error associated with the analytical techniques used to measure the impurity and does not substantially broaden the 5% limit.

VI. Other Allegations

• Indirect Infringement: The complaint alleges induced infringement under 35 U.S.C. § 271(b). The basis for this allegation is that Defendant’s proposed product label will instruct physicians and healthcare providers to administer the VEMLIDY ANDA Product for the treatment of hepatitis B, which would cause those providers to directly infringe the patents Compl. ¶51-55, ¶84-88
• Willful Infringement: The complaint alleges that Defendant had actual knowledge of the patents-in-suit no later than the date they were listed in the FDA's Orange Book for VEMLIDY® Compl. ¶48, ¶81 It further alleges that Defendant's efforts to market its generic product were made with full knowledge of the patents and "without a reasonable basis for believing" it would not be liable for infringement, which may support a finding of willfulness Compl. ¶49, ¶82

VII. Analyst’s Conclusion: Key Questions for the Case

• A central issue will be one of analytical proof: Does the defendant's proposed generic product, upon chemical analysis, possess the specific hemifumarate crystalline structure claimed in the ’065 patent and the purity profile—specifically, less than "about 5%" monofumarate by weight—recited in the ’769 patent?
• A related question will be one of definitional scope: How will the court construe the term "about" in the context of the ’769 patent's purity requirement? The resolution of this classic claim construction issue may be dispositive of infringement if the accused product's impurity level is near the 5% threshold.
• Finally, while not detailed in the complaint, the Defendant's Paragraph IV certification signals that a core part of the litigation will be a dispute over patent validity: Are the claims directed to a specific salt form and purity level non-obvious and enabled over the prior art, including the previously disclosed monofumarate form of the same compound?