Key Points

• Federal court denies Rule 25(c) party substitution in ANDA patent infringement case, holding that unresolved questions about scope of patent rights transfer weigh against replacing original plaintiffs with acquirer.
• Hatch-Waxman 30-month regulatory stay creates finite litigation window that constrains party substitution and discovery restructuring in ANDA cases
• Third Circuit precedent favors joinder over substitution under Rule 25(c) when the completeness of a patent rights transfer remains in dispute.

When intellectual property changes hands mid-litigation, courts will not automatically grant a substitution motion simply because the assets have moved, as a recent decision by a federal magistrate judge in New Jersey illustrated.

In Azurity Pharmaceuticals, Inc. v. Alkem Laboratories Ltd., Civil No. 25-12118 (D.N.J. Apr. 8, 2026), U.S. Magistrate Judge Elizabeth A. Pascal denied a motion to substitute a patent acquirer as the sole plaintiff in consolidated Hatch-Waxman ANDA litigation, finding that unresolved questions about the scope of the asset transfer — and the risk of significant discovery disruption under the 30-month regulatory stay — outweighed any benefit of streamlining the case to a single plaintiff.

The ruling underscores a practical reality for patent litigators: if the scope of the transfer is unclear and substitution threatens to derail discovery, courts may instead keep all parties in the case until the record is fully developed.

Background

Braintree Laboratories, Inc. and Sebela US Inc. originally filed suit against Alkem Laboratories Ltd. in June 2025, alleging infringement of patents covering SUTAB®. A similar lawsuit was filed against Hetero USA Inc. in July 2025 and consolidated. In December 2025, plaintiffs disclosed that Azurity Pharmaceuticals, Inc. had acquired the entirety of the U.S. rights to the SUTAB® product and the asserted patents from Braintree and Sebela under an asset purchase agreement. Following a conference, the Court ordered, with consent of all parties, that Azurity be added as a plaintiff and counterclaim defendant, while Braintree and Sebela remained in the case in the same capacity. The Court further ordered that the full Asset Purchase Agreement be submitted for in camera review. Plaintiffs subsequently moved for full substitution of Azurity in place of Braintree and Sebela, which defendants opposed.

The Court's Analysis

In its 12-page decision, the Court evaluated the motion under the Third Circuit's Rule 25(c) analytical framework, which instructs courts to focus on whether substitution or joinder would best "facilitate the conduct of the litigation."

The Court addressed two primary issues raised by defendants.

Transfer of Patent Rights

Defendants argued that they could not adequately assess whether Braintree and Sebela had transferred all substantial rights in the asserted patents and the SUTAB® NDA to Azurity, because they lacked access to the full Asset Purchase Agreement. Azurity had declined to share the full agreement on confidentiality grounds, instead providing only a “heavily redacted” excerpt. Defendants pointed to the original patent assignment documents, which contained provisions under which the inventors had “covenanted—and Braintree had retained—continuing obligations to procure, maintain, enforce, and defend the patents, including obligations to participate in any proceedings related to those patents.” Defendants thus contended it remained unclear whether the Asset Purchase Agreement conveyed the “full bundle of substantive rights and responsibilities associated with the patents.”

Plaintiffs countered that they had “completely divested” themselves of their “entire interest in the patents-in-suit” and that the relevant portion of the Agreement, to which defendants had access, was clear.

The Court noted, however, that although it had received an unredacted copy of the asset purchase agreement for in camera review suggesting a substantial portion of Braintree's and Sebela's rights had been transferred, “deciphering the intricacies of the seventy-five-page contract would require a unilateral analysis by the Court unaided by the parties' adversarial arguments and evidentiary proofs.” Given this “uncertainty,” the Court found it more appropriate for Braintree and Sebela to remain as plaintiffs alongside the already-joined Azurity until the factual record could be more fully developed.

Prejudice and Facilitation of the Litigation

The Court also found that substitution at this stage of the litigation would not facilitate the conduct of the case and could result in prejudice to defendants. The statutory framework underlying the case was central to this analysis. Under the Hatch-Waxman Act, a patent owner who brings an infringement claim against an ANDA filer within 45 days of receiving the filer's Paragraph IV certification triggers an automatic 30-month stay preventing FDA approval of the filer’s ANDA. The stays in this case began on May 15, 2025 and June 11, 2025. By the time plaintiffs filed the substitution motion on January 21, 2026, more than seven months of the 30-month stay had already elapsed, leaving less than two years in which to complete the litigation.

Defendants observed that Braintree and Sebela had identified multiple employees in their Rule 26 Initial Disclosures—including senior executives and inventors—with first-hand knowledge concerning the SUTAB® NDA, the patents, and related topics such as inventorship, conception, and reduction to practice. Despite these representations, defendants argued that Braintree and Sebela had not provided any relevant information listed in their initial disclosures or responded to previously served discovery requests, under the objection that Azurity would be substituted in their place and provide relevant discovery. The Court noted that this course of conduct had squandered several months of the limited 30-month stay period.

Plaintiffs, for their part, argued that substitution “would not materially prejudice defendants or disrupt ongoing discovery,” because fact discovery does not close until December 2026. Further, defendant could obtain discovery from a single party (Azurity) or if any discovery was necessary from Braintree and Sebela, third-party discovery could be used.

The Court was not persuaded, finding that granting the substitution would require defendants to re-serve all existing discovery on Azurity and pursue Rule 45 subpoenas directed to Braintree's and Sebela's previously identified witnesses, resulting in duplication of already completed efforts. The Court also noted that non-party discovery requires a stronger showing of relevance than routine party discovery, and non-parties are generally afforded greater protection from discovery than parties. The mere availability of Rule 45 as a discovery tool, the Court reasoned, does not serve as a replacement for party discovery. The Court further noted that Braintree’s and Sebela’s “ongoing failure” to respond to the existing discovery requests undermined their assurances that they would willingly comply with third-party discovery. Thus, these additional discovery efforts would not “facilitate the conduct of the litigation.”

Conclusion

The Court denied plaintiffs' motion for substitution without prejudice, holding that Braintree, Sebela, and Azurity should all remain as named plaintiffs and conduct discovery accordingly. The Court indicated that plaintiffs may renew the motion after the close of fact discovery, once defendants have had the opportunity to develop the record regarding the rights and obligations of the parties.

Takeaways

This opinion underscores three noteworthy principles for practitioners considering substitution of parties:

1. Courts may decline to independently parse complex transactional documents.
   Even with an unredacted copy available for in camera review, the Court was unwilling to decipher the intricacies of a seventy-five-page Asset Purchase Agreement without the benefit of adversarial arguments and evidentiary proofs from the parties, in particular where defendants did not have access to the full agreement. This signals that parties seeking substitution based on complex transactional agreements or factual situations should anticipate the need to provide detailed briefing and evidence addressing the scope of the transfer.
2. The 30-month stay in ANDA litigation imposes meaningful time constraints.
   The Court emphasized that the Hatch-Waxman 30-month stay creates a finite window for completing litigation, and discovery delays resulting from the attempted substitution of Braintree and Sebela risked the timely completion of the case. This consideration weighed against granting substitution.
3. Joinder is preferred over substitution when the scope of a transfer is uncertain.
   Consistent with established Third Circuit precedent, the Court opted to maintain all three entities as named plaintiffs rather than substitute Azurity alone, preserving the status quo until the factual record is more fully developed.

Paul W. Kalish and Jonathan J. Madara are members of the IP Litigation team in Fox Rothschild’s Princeton, NJ office and write about patent litigation decisions in the District of New Jersey. Contact Paul at pkalish@foxrothschild.com or 609.895.6751 and Jonathan at jmadara@foxrothschild.com or 609.844.7428.

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