Petitioner v. Halozyme, Inc.

This case, IPR2026-00313, is an Inter Partes Review (IPR) before the Patent Trial and Appeal Board (PTAB) initiated by Merck Sharp & Dohme LLC (Merck), a multinational pharmaceutical company, against Halozyme, Inc., a biotechnology company specializing in drug delivery solutions. Halozyme develops and licenses its proprietary ENHANZE® technology, which utilizes recombinant human hyaluronidase (rHuPH20) enzymes to facilitate the subcutaneous delivery of therapeutics typically administered intravenously, aiming to improve patient convenience and reduce administration time. Merck, a major global healthcare company with significant revenues from cancer treatments, vaccines, and animal health products, is the petitioner seeking to invalidate Halozyme's U.S. Patent No. 11,041,149. This patent broadly relates to modified hyaluronidase enzymes for enhancing the subcutaneous delivery of therapeutic drugs, a core aspect of Halozyme's technology.

The accused product at the heart of this dispute is Merck's subcutaneous (SC) formulation of its blockbuster cancer immunotherapy, Keytruda (pembrolizumab), marketed as Keytruda Qlex. This SC formulation incorporates berahyaluronidase alfa, an enzyme alleged by Halozyme to infringe its patented MDASE™ technology, which allows for faster and more convenient drug administration compared to traditional intravenous infusions. The IPR is part of a broader, high-stakes patent battle between the two pharmaceutical giants. Halozyme filed a patent infringement lawsuit against Merck in the U.S. District Court in New Jersey on April 24, 2025, alleging willful infringement of 15 patents, including the '149 patent, by Merck's SC Keytruda. Merck, in turn, has filed multiple IPR and post-grant review (PGR) petitions challenging the validity of several of Halozyme's patents asserted in the district court litigation.

This case is particularly notable due to the substantial market value of Keytruda, which generated $29.5 billion in sales for Merck in 2024, representing 46% of its total revenue, and the strategic importance of subcutaneous delivery for patient convenience and healthcare efficiency. The FDA approved Keytruda Qlex for various solid tumor indications in September/October 2025, further increasing the stakes of the patent dispute. The parallel PTAB proceedings and district court litigation, including a preliminary injunction granted to Halozyme against Merck's Keytruda SC in Germany in December 2025 regarding a related European patent, underscore the global and multi-faceted nature of this pharmaceutical patent conflict. The outcome of these challenges will significantly impact the commercialization of Keytruda Qlex and the future of subcutaneous drug delivery technologies.

This case involves a patent infringement lawsuit filed by Halozyme, Inc. against Merck Sharp & Dohme Corp. (Merck) in the U.S. District Court for the District of New Jersey, along with parallel Inter Partes Review (IPR) and Post-Grant Review (PGR) proceedings before the Patent Trial and Appeal Board (PTAB) challenging the validity of Halozyme's patents.

Case Caption (District Court): Halozyme, Inc. v. Merck Sharp & Dohme Corp.
Case Number (District Court): 2:25-cv-03179 (D.N.J.)
Patents at Issue: United States Patent No. 11,041,149 is one of fifteen patents asserted by Halozyme in the district court litigation.

Here is a chronological overview of the key legal developments:

District Court Litigation (Halozyme v. Merck)

• 2025-04-24 – Complaint Filed: Halozyme, Inc. filed a patent infringement lawsuit against Merck Sharp & Dohme Corp. in the U.S. District Court for the District of New Jersey. Halozyme alleges that Merck's subcutaneous (SC) formulation of its cancer medicine, Keytruda (marketed as QLEX in the U.S. and Keytruda SC in Germany), infringes 15 of Halozyme's patents related to its MDASE™ subcutaneous delivery technology. Halozyme is seeking damages and injunctive relief to prevent the manufacture, sale, and import of SC Keytruda in the U.S.
• 2025-07-14 – Responsive Pleading Deadline: The court set the deadline for Merck's responsive pleading as July 14, 2025. As of May 23, 2025, the district court case was in its very early stages, with Halozyme's complaint being the only substantive filing and no significant orders issued other than initial stipulations regarding the defendant entity and service.
• Present Posture: The district court litigation is ongoing and in its early stages. There has been no reported claim construction (Markman) ruling, discovery milestones, or trial events. Given the parallel PTAB proceedings, it is possible that a motion to stay the district court litigation pending the outcome of the IPRs and PGRs has been considered or discussed, with a PTAB filing noting that the D.N.J. "would likely stay the litigation if the Board institutes at least some of Merck's pending PGRs."

Parallel PTAB Proceedings (Merck v. Halozyme & Halozyme v. Alteogen)

Merck has initiated multiple challenges against Halozyme's patents at the PTAB, and Halozyme has also filed an IPR against a related patent.

• November 2024 to April 2025 – Merck Files PGRs: Merck filed multiple Post-Grant Reviews (PGRs) with the PTAB challenging the validity of at least ten of Halozyme's U.S. patents, eight of which are asserted in the district court litigation. These filings started as early as November 2024.
• 2026-03-23 – IPR2026-00313 Filed (Against 11041149): Merck Sharp & Dohme LLC (Petitioner) filed IPR2026-00313 against Halozyme Inc. (Patent Owner), challenging the validity of U.S. Patent No. 11,041,149. This IPR is currently pending a decision on institution.
• May 2026 – PTAB Rulings on Related Proceedings:
  • The PTAB ruled that a claim of a Halozyme MDASE patent, which was challenged by Merck in a PGR, could not be patented. This was reportedly the first final judgment among several MDASE patent invalidation trials.
  • The PTAB rejected an IPR (IPR2026-00176) filed by Halozyme against U.S. Patent No. 12,221,638, owned by Alteogen (a company whose ALT-B4 platform is used by Merck for SC Keytruda). The PTAB found that Halozyme did not show a reasonable possibility of winning at least one of the challenged claims.

Effect on Litigation:
The ongoing PTAB proceedings, particularly the decisions on institution and final written decisions, are likely to have a significant impact on the district court litigation. Successful invalidation of Halozyme's asserted patents at the PTAB could lead to a stay or dismissal of the corresponding claims in the district court case. The early PTAB decisions, which appear to favor Merck and Alteogen, are being closely watched by the industry for their potential influence on the main U.S. lawsuit.

International Development:
In a related international development, Halozyme announced on December 4, 2025, that a German court granted its request for a preliminary injunction, ordering Merck to refrain from distributing and offering Keytruda SC in Germany based on infringement of a European MDASE patent (European Patent No. 2 797 622).

I'll research the petitioner/plaintiff side counsel. Let me run several targeted searches.

Let me drill into counsel of record for the petitioner and for the parallel district court case.

Good progress. Now let me pin down counsel of record specifically in IPR2026-00313 and verify the institution status.

Plaintiff (Petitioner) representatives — Merck Sharp & Dohme LLC

Party-alignment note (important). IPR2026-00313 is captioned Petitioner v. Halozyme, Inc., and the case metadata lists Halozyme as the sole "Defendant." On the plaintiff side of this PTAB proceeding, the party in the plaintiff's position is the Petitioner, Merck Sharp & Dohme LLC ("MSD LLC"). The section above already catalogues Halozyme's counsel (Patent Owner / district-court-side defendants). If your question is instead aimed at the literal plaintiff in the underlying infringement suit — Halozyme, Inc. v. Merck Sharp & Dohme Corp., No. 2:25-cv-03179 (D.N.J., filed Apr. 24, 2025) — that plaintiff is Halozyme, and its PTAB and district-court counsel are the ones already set out in the "Defendant representatives" section (Sterne Kessler; Quinn Emanuel; Cravath; Walsh Pizzi as local counsel). I do not repeat them here. What follows is the plaintiff-side (Merck/Petitioner) counsel of record, which was not covered previously.

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Outside counsel — Sidley Austin LLP (lead trial counsel)

Outside counsel — Dechert LLP (Merck's district-court and PTAB team, admitted pro hac vice)

In-house counsel

District-court counsel for the same client (Merck), for context

Law.com Radar reports that Dechert LLP and Gibbons P.C. (Newark, NJ) entered appearances for Merck in D.N.J. 2:25-cv-03179, with Halozyme represented by Walsh Pizzi O'Reilly Falanga. Dechert's role is corroborated by the Goldberg and Helm declarations; I could not verify individual Gibbons attorney names as local counsel from the sources retrieved, so I am not naming any.

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Two things worth flagging

1. Status contradiction. The case metadata says "Status: Pending," and the earlier summary describes IPR2026-00313 as "pending a decision on institution." The USPTO's Notice of Decisions on Institution (Sept. 2026) lists IPR2026-00312, -00313 and -00314 among the proceedings in which institution was granted, and IP Verse records -00313 as "Trial Instituted." The metadata should be updated to Instituted.
2. Counsel-of-record caveat. I was unable to retrieve the live PTAB docket sheet or the Petitioner Power of Attorney for IPR2026-00313 itself (PTAB API/PACER snippets only; the Sidley/Dechert counsel tables above are drawn from the closely parallel Merck-Halozyme PGRs, the shared petitioner Power of Attorney, and the declarations appearing on the -00313 record). Sidley's Kushan/Merck in-house Stewart combination is near-certain, and the Dechert pro hac vice team is highly likely, but until the -00313 Power of Attorney and any pro hac vice orders are pulled directly, treat the Engen, Wang, and Hackman entries as inferred rather than confirmed. Notably, no separate "plaintiff's counsel" appears for Halozyme in this IPR that is not already listed in the prior section.

Relevant sourcing: Petitioner's Power of Attorney and Updated Mandatory Notice, PGR2025-00017 (docketalarm); Notice re Sue Wang, PGR2025-00039 (Nov. 11, 2025); Declarations of Katherine A. Helm (EX1115) and Brian M. Goldberg (EX1114), PGR2025-00009; Hecht deposition transcript, Aug. 26, 2025 (appearances); Law.com Radar card, Halozyme, Inc. v. Merck Sharp & Dohme Corp., 2:25-cv-03179 (D.N.J.); USPTO Notice of Decisions on Institution (Sept. 2026) (pearceip.law); IP Verse Halozyme PTAB tracker; Docket Alarm IPR2026-00313 docket page.

Halozyme, Inc., as the patent owner in IPR2026-00313, is represented by both outside counsel and in-house counsel.

Outside Counsel

• Eldora L. Ellison, Ph.D.

  • Role: Lead Counsel
  • Firm: Sterne, Kessler, Goldstein & Fox PLLC, Washington, D.C.
  • Note: Dr. Ellison is consistently listed as lead counsel for Halozyme in PTAB proceedings, including related PGRs against Merck. Sterne Kessler is a prominent intellectual property law firm.

• Lauren N. Martin

  • Role: Backup Counsel
  • Firm: Quinn Emanuel Urquhart & Sullivan, LLP, Boston, MA
  • Note: Lauren Martin was recently added as backup counsel for Halozyme in a related PGR. Quinn Emanuel has successfully represented Halozyme in other patent matters, including securing a preliminary injunction against Merck in Germany for a related patent.

While not explicitly listed for IPR2026-00313, it is highly probable that other attorneys from Sterne Kessler, such as R. Wilson Powers III, Jennifer Meyer Chagnon, David H. Holman, Tyler C. Liu, and Louis P. Panzica, Jr., will also be involved, as they have been listed as counsel to receive service in related PTAB filings.

In-house Counsel

• Josh Mack

  • Role: Executive Director, Patent Litigation Counsel
  • Firm: Halozyme, Inc., San Diego, CA
  • Note: Josh Mack leads all litigation matters for Halozyme and has extensive experience in patent litigation from both in-house and outside counsel positions, including at Wilson Sonsini Goodrich & Rosati and Amgen.

• Aubrey Haddach

  • Role: Executive Director, Intellectual Property
  • Firm: Halozyme, Inc., San Diego, CA
  • Note: Aubrey Haddach has a diverse background in intellectual property, including managing global patent portfolios and advising on IP and corporate transactions for life sciences companies.

• Mark Snyder

  • Role: Senior Vice President, General Counsel, Chief Compliance Officer and Corporate Secretary
  • Firm: Halozyme, Inc., San Diego, CA
  • Note: Mark Snyder oversees Halozyme's legal teams, including IP strategy and litigation. He previously led litigation strategy for Qualcomm.

It is worth noting that in the parallel district court litigation (Halozyme, Inc. v. Merck Sharp & Dohme Corp., D.N.J. Case No. 2:25-cv-03179), Halozyme is also represented by Liza M. Walsh, Katelyn O'Reilly, and Lauren R. Malakoff of Walsh Pizzi O'Reilly Falanga LLP, located in Newark, New Jersey, as local counsel. Additionally, Elliot Choi, Zachariah B. Summers, and Nancy L. Zhang have appeared pro hac vice for Halozyme in the district court case. While these attorneys are involved in the broader dispute, the PTAB representation for IPRs specifically tends to rely on specialized PTAB counsel.