Bow River LLC v. Zydus Lifesciences Global FZE

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: Bow River LLC (Wyoming)
  • Defendant: Zydus Lifesciences Global FZE (Dubai); Zydus Pharmaceuticals (USA) Inc. (New Jersey); Zydus Lifesciences Limited (India)
  • Plaintiff's Counsel: Robinson Miller LLC
• Case Identification: 2:26-cv-05216, D.N.J., 05/08/2026
• Venue Allegations: Venue is alleged to be proper in the District of New Jersey primarily because Defendant Zydus Pharmaceuticals (USA) Inc. is incorporated under the laws of New Jersey, rendering it "essentially at home" in the District.
• Core Dispute: Plaintiff alleges that Defendants' submission of an Abbreviated New Drug Application (ANDA) to market a generic version of the cancer drug VITRAKVI® (larotrectinib) constitutes an act of infringement of patents covering methods for safely administering the drug to patients who have also been treated with a strong CYP3A inhibitor.
• Technical Context: The technology addresses potentially dangerous drug-drug interactions (DDIs) by providing specific dosing regimens to avoid adverse events when a drug metabolized by the CYP3A4 enzyme (a substrate) is given after treatment with a drug that inhibits that same enzyme.
• Key Procedural History: This action was commenced under the Hatch-Waxman Act following a notice letter from Zydus, dated March 26, 2026, informing Bow River of its filing of ANDA No. 220875 with a Paragraph IV certification. The patents-in-suit are listed in the U.S. Food and Drug Administration's "Orange Book" as covering the VITRAKVI® reference product.

Case Timeline

Date	Event
2017-05-16	Priority Date for '967 and '998 Patents
2022-05-24	U.S. Patent No. 11,337,967 Issues
2024-05-07	U.S. Patent No. 11,974,998 Issues
2026-03-26	Zydus sends Notice Letter regarding ANDA filing
2026-05-08	Complaint Filed

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

U.S. Patent No. 11,337,967 - "Methods of Treatment"

• Patent Identification: U.S. Patent No. 11,337,967, issued May 24, 2022.

The Invention Explained

• Problem Addressed: The patent addresses a safety gap in pharmaceutical labeling and practice Compl. ¶¶6-7 While it is known that co-administration of a strong CYP3A4 enzyme inhibitor (like the antifungal posaconazole) and a drug metabolized by that enzyme (a CYP3A4 substrate) is contraindicated, there was previously no guidance on how long a patient must wait after stopping the inhibitor before it is safe to start the substrate drug '967 Patent, col. 1:47-64
• The Patented Solution: The invention is based on the discovery that the inhibitory effects of posaconazole persist longer than expected after treatment stops, creating a risk of adverse drug interactions if a CYP3A4 substrate is administered too soon '967 Patent, col. 2:15-22 The patent claims methods to mitigate this risk, which involve either a "washout or delay period" of approximately 2-42 days after ceasing posaconazole administration before starting the substrate drug, or alternatively, administering a reduced dose of the substrate drug for a similar period '967 Patent, abstract '967 Patent, col. 2:23-41
• Technical Importance: This method provides a protocol to safely administer critical medications, such as certain cancer therapies, to immunocompromised patients who may also require treatment with strong antifungal agents, thereby minimizing the risk of life-threatening DDIs Compl. ¶¶31-33

Key Claims at a Glance

The complaint asserts infringement of "one or more claims" of the '967 Patent without further specification Compl. ¶52 Independent claim 1 includes the following essential elements:

• A method of treating a patient having a disease or condition with a therapeutically effective amount of a CYP3A4 substrate drug contraindicated for concomitant use with a strong CYP3A4 inhibitor.
• The patient has previously been treated with posaconazole.
• The method comprises: (a) ceasing administration of posaconazole; and (b) delaying a first treatment of the CYP3A4 substrate drug for at least 2 days after ceasing the posaconazole regimen.

U.S. Patent No. 11,974,998 - "Methods of Treatment"

• Patent Identification: U.S. Patent No. 11,974,998, issued May 7, 2024.

The Invention Explained

• Problem Addressed: The '998 Patent addresses the same technical problem as the '967 Patent: the risk of DDIs when administering a CYP3A4 substrate drug to a patient who was previously being treated with the strong CYP3A4 inhibitor posaconazole '998 Patent, col. 1:50-67
• The Patented Solution: The patent discloses methods of treatment that involve a specific delay period after stopping the CYP3A4 inhibitor before administering the substrate drug, which is identified as a tyrosine kinase inhibitor for treating certain cancers '998 Patent, claim 1 The invention is based on clinical findings that the inhibitor's effects persist longer than previously understood, necessitating a "washout" period to ensure patient safety '998 Patent, col. 2:15-34
• Technical Importance: The claimed method provides specific, actionable guidance for clinicians to manage the transition between two critical but interacting drug classes, enhancing the safe use of targeted cancer therapies in patients with fungal co-infections Compl. ¶¶32-34

Key Claims at a Glance

The complaint asserts infringement of "one or more claims" of the '998 Patent Compl. ¶58 Independent claim 1 includes the following essential elements:

• A method of treating a patient in need thereof with a tyrosine kinase inhibitor, wherein the patient is treated with a strong CYP3A4 inhibitor.
• The method comprises the steps of: (a) stopping the strong CYP3A4 inhibitor treatment; (b) delaying administration for at least 9 days of a dose of the tyrosine kinase inhibitor; and then (c) administering the dose of the tyrosine kinase inhibitor.
• The strong CYP3A4 inhibitor is posaconazole.
• The treatment is for a solid tumor characterized by a gene fusion, selected from a specific list including sarcoma, colorectal cancer, and others.

III. The Accused Instrumentality

• Product Identification: The accused instrumentalities are the "Zydus ANDA Products," which are generic versions of VITRAKVI® (larotrectinib) capsules in 25 mg and 100 mg dosage strengths, for which Zydus seeks FDA approval under ANDA No. 220875 Compl. ¶2
• Functionality and Market Context: The active ingredient, larotrectinib, is a first-in-class cancer drug approved for treating adult and pediatric patients with solid tumors that have a specific genetic mutation (an NTRK gene fusion) Compl. ¶¶28-30 As a generic equivalent, the Zydus ANDA Products are alleged to have the same active ingredient, dosage form, and strength as VITRAKVI® Compl. ¶43 The complaint alleges that the proposed prescribing information for Zydus's product is "substantially identical" to that of VITRAKVI®, which allegedly instructs the performance of the patented methods Compl. ¶45

IV. Analysis of Infringement Allegations

The complaint alleges that by filing its ANDA, Zydus has committed an act of infringement under 35 U.S.C. § 271(e)(2)(A), and that commercialization of the Zydus ANDA Products would induce infringement by medical professionals and patients who would follow the instructions on the proposed product label (Compl. ¶51; Compl. ¶52).

No probative visual evidence provided in complaint.

'967 Patent Infringement Allegations

Claim Element (from Independent Claim 1)	Alleged Infringing Functionality	Complaint Citation	Patent Citation
A method of treating a patient... with a therapeutically effective amount of a CYP3A4 substrate drug contraindicated for concomitant use with a strong CYP3A4 inhibitor,	The Zydus ANDA Products contain larotrectinib, which is a CYP3A4 substrate drug. The proposed label is alleged to instruct its use for treating cancer.	¶30; ¶32; ¶45	col. 2:11-15
wherein the patient has previously been treated with posaconazole,	The complaint alleges that patients prescribed larotrectinib are often immunocompromised and may also be prescribed antifungal agents such as posaconazole.	¶31	col. 1:19-25
said method comprising: (a) ceasing administration of posaconazole; and (b) delaying a first treatment of the CYP3A4 substrate drug for at least 2 days after ceasing the posaconazole regimen.	The complaint alleges the proposed Zydus label will be substantially identical to the VITRAKVI® label, which instructs this method of use.	¶34; ¶45; ¶52	col. 2:23-34

'998 Patent Infringement Allegations

Claim Element (from Independent Claim 1)	Alleged Infringing Functionality	Complaint Citation	Patent Citation
A method of treating a patient in need thereof with a tyrosine kinase inhibitor, wherein the patient is treated with a strong CYP3A4 inhibitor,	The Zydus ANDA Products contain larotrectinib, a tyrosine kinase inhibitor, and the proposed label allegedly provides instructions for its use in patients also treated with posaconazole, a strong CYP3A4 inhibitor.	¶29; ¶31; ¶32	col. 4:15-18
comprising the steps of: (a) stopping the strong CYP3A4 inhibitor treatment; (b) delaying administering, for at least 9 days... a dose of the tyrosine kinase inhibitor...; and then (c) administering the dose...	The complaint alleges the proposed Zydus label will instruct performance of this dosing regimen.	¶34; ¶45; ¶58	col. 3:15-29
wherein the strong CYP3A4 inhibitor is posaconazole;	The complaint specifically alleges the interaction between larotrectinib and posaconazole as the basis for the invention.	¶32; ¶33	col. 1:50-54
and wherein the solid tumor characterized by a gene fusion is selected from the group consisting of sarcoma, colorectal cancer, thyroid cancer, melanoma, gastrointestinal stromal tumor, pancreatic cancer, breast cancer, ovarian cancer, and astrocytoma.	The Zydus ANDA Product is a generic of VITRAKVI®, which is used for treating solid tumors with an NTRK gene fusion.	¶29	col. 4:30-67

• Identified Points of Contention:
  • Scope Questions: The core of the dispute will likely concern the content of Zydus's proposed label. A primary question for the court will be whether the instructions on Zydus's label direct, encourage, or recommend that medical professionals perform the specific steps of the asserted claims. The complaint's allegation that the proposed label is "substantially identical" to the VITRAKVI® label will be a key factual issue Compl. ¶45
  • Technical Questions: A factual question is whether the specific delay periods recited in the claims ("at least 2 days" in the '967 Patent; "at least 9 days" in the '998 Patent) are explicitly or implicitly taught by Zydus's proposed labeling. Any ambiguity or lack of specificity in the proposed label's instructions regarding a "washout" period could be a central point of dispute.

V. Key Claim Terms for Construction

• The Term: "delaying a first treatment... for at least 2 days" ('967 Patent, claim 1)

• Context and Importance: This term is the central limitation of the method claim. The infringement analysis will depend on whether Zydus's proposed label is found to instruct a delay of this specific minimum duration. Practitioners may focus on this term because its construction will define the temporal boundary for an infringing act.

• Intrinsic Evidence for Interpretation:

  • Evidence for a Broader Interpretation: The specification discloses a much wider range for the delay, stating the washout period is "about 2-42 days (e.g., 2-21 days)" '967 Patent, col. 2:26-29 This may support an argument that "at least 2 days" is merely an exemplary lower bound of a broader, more flexible concept.
  • Evidence for a Narrower Interpretation: The claim language itself provides a specific, numerical floor ("at least 2 days"). A party may argue that this plain language should be given its ordinary meaning, establishing a clear, non-negotiable minimum delay required for infringement.

• The Term: "delaying administering, for at least 9 days" '998 Patent, claim 1

• Context and Importance: This limitation is highly specific and central to infringement of the '998 Patent. The case may turn on whether Zydus's proposed label instructs a delay of this exact minimum duration. Any different or more general instruction on the label could form the basis of a non-infringement argument.

• Intrinsic Evidence for Interpretation:

  • Evidence for a Broader Interpretation: The specification discloses the same broad "about 2-42 days" washout period as the '967 Patent, which may suggest the "9 days" limitation is one specific embodiment rather than the sole scope of the invention '998 Patent, col. 2:26-29
  • Evidence for a Narrower Interpretation: The patent includes Figure 9, which explicitly plots data points for "Days After Posaconazole Discontinuation" extending to 14 days, with data shown near the 9-day mark. The patentee may argue this figure demonstrates the technical significance and deliberate selection of the "at least 9 days" period, supporting a narrow construction focused on this specific timeframe.

VI. Other Allegations

• Indirect Infringement: The complaint alleges induced infringement under 35 U.S.C. § 271(b). The factual basis is the allegation that Zydus's proposed prescribing information for its ANDA products will instruct and encourage patients and medical practitioners to administer the drug in a manner that directly infringes the patented methods Compl. ¶52 Compl. ¶58
• Willful Infringement: The complaint alleges that Zydus had "actual and constructive knowledge" of the patents prior to filing its ANDA, in part because the patents are listed in the Orange Book Compl. ¶54 Compl. ¶60 It further alleges Zydus had "specific intent to infringe" when it filed the ANDA, forming the basis for a willfulness claim Compl. ¶54 Compl. ¶60

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

• A central issue will be one of induced infringement: does the specific language in Zydus's proposed product label actively instruct or encourage medical practitioners to delay the administration of larotrectinib for the specific minimum durations required by the asserted claims ("at least 2 days" and "at least 9 days"), or does it provide more general guidance that falls outside the claims' scope?
• A second key question will be one of claim construction: how will the court define the specific temporal limitations of the claims? The dispute may focus on whether the phrase "at least 9 days," for example, should be interpreted strictly as a numerical requirement for infringement, or more broadly in the context of the specification's disclosure of a "2-42 day" washout period.