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).

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The user is asking to identify the counsel of record for the plaintiff(s) in the patent infringement case.
Based on the "Key legal developments & outcome" section, Halozyme Therapeutics, Inc. is the plaintiff in the parallel district court patent infringement lawsuit against Merck Sharp & Dohme Corp. (Merck) in the U.S. District Court in New Jersey. Merck Sharp & Dohme LLC is the Petitioner in the IPR.

Therefore, I need to identify the counsel for Halozyme, Inc. in the district court litigation. I will search for "Halozyme Therapeutics, Inc. v. Merck Sharp & Dohme Corp. counsel" and similar queries to find this information. I also need to ensure I differentiate between IPR counsel and district court counsel, as the question specifically asks for the "plaintiff(s) in this patent infringement case", which refers to the district court case where Halozyme is the plaintiff.

Let's break down the search:

1. Identify the district court case: The previous section states "Halozyme Therapeutics, Inc. filed a patent infringement lawsuit against Merck Sharp & Dohme Corp. (Merck) in the U.S. District Court in New Jersey." I need to find the case number for this.
2. Search for counsel for Halozyme (plaintiff) in that district court case.

Given the current information, I only know the parties and the court (U.S. District Court in New Jersey), but not the specific case number for the district court litigation. My initial search queries will try to uncover that case number and then identify counsel.

If I cannot find specific counsel for the district court case for Halozyme, I will explicitly state that. I will also be mindful not to conflate IPR counsel (for Merck) with district court counsel (for Halozyme).

Let's refine the search to look for the district court case number and then counsel.
Given the information provided earlier: "Halozyme Therapeutics, Inc. filed a patent infringement lawsuit against Merck Sharp & Dohme Corp. (Merck) in the U.S. District Court in New Jersey." and "Complaint Filing (2025-04-24)". I will look for this specific case.Halozyme, Inc. (Plaintiff) is represented by a team of lead counsel from Quinn Emanuel Urquhart & Sullivan, LLP, and local counsel from Walsh Pizzi O'Reilly Falanga LLP, in addition to its in-house legal team, in the patent infringement case Halozyme Inc v. Merck Sharp & Dohme Corp, Case No. 2:25-cv-03179 in the U.S. District Court in New Jersey.

The counsel of record for Halozyme, Inc. includes:

• David A. Nelson, Lead Counsel
  • Firm: Quinn Emanuel Urquhart & Sullivan, LLP, Chicago, IL.
  • Experience: Co-Chair of Quinn Emanuel's National Intellectual Property Litigation Practice, specializing in patent infringement litigation with a degree in Electrical Engineering. He has led over 150 patent litigation matters and tried over 35 jury cases, representing multinational technology companies in various forums including the Eastern District of Texas, District of Delaware, Northern District of California, and the ITC.
• Zachariah B. Summers, Lead Counsel
  • Firm: Quinn Emanuel Urquhart & Sullivan, LLP, Los Angeles, CA.
  • Experience: Partner focusing on technology-related litigation with an emphasis on complex patent trials. He has represented clients such as Qualcomm, Samsung, Google, and Motorola in district court, ITC, and PTAB proceedings, including work on CRISPR-Cas9 patent interference proceedings.
• Liza M. Walsh, Local Counsel
  • Firm: Walsh Pizzi O'Reilly Falanga LLP, Newark, NJ.
  • Experience: Managing Partner with over 30 years of experience in federal and complex commercial litigation, focusing on intellectual property, antitrust, and class action defense. She has defended major pharmaceutical companies in significant patent litigation and has been recognized in "Best Lawyers in America" for Patent Law.
• Lauren Ruth Malakoff, Local Counsel
  • Firm: Walsh Pizzi O'Reilly Falanga LLP, Newark, NJ.
  • Experience: An associate focusing on business and commercial litigation, as well as intellectual property matters. She has been recognized in "Best Lawyers: Ones to Watch® in America 2026" for Litigation - Patent.

Halozyme In-House Counsel:

• Mark Snyder, Chief Legal Officer
• Josh Mack, Executive Director and Patent Litigation Counsel
• Aubrey Haddach, Executive Director Intellectual Property

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.