Halozyme, Inc. v. Merck Sharp & Dohme Corp. et al.

Halozyme, Inc., a biotechnology operating company headquartered in San Diego, California, is suing Merck Sharp & Dohme Corp. and Merck Sharp and Dohme LLC, multinational pharmaceutical operating companies based in Rahway, New Jersey. Halozyme's core business revolves around its proprietary ENHANZE® drug delivery technology, which utilizes a recombinant human hyaluronidase enzyme (rHuPH20) to enable and enhance the subcutaneous administration of injectable drugs. Merck, a major player in the pharmaceutical industry known for its cancer treatments, vaccines, and animal health products, is accused of infringing Halozyme's patents with its subcutaneous KEYTRUDA® (Keytruda Qlex) formulation. Keytruda Qlex is a fixed-combination drug product of pembrolizumab (Keytruda's active ingredient) and berahyaluronidase alfa, a hyaluronidase variant that enhances the dispersion and permeability of pembrolizumab, thereby facilitating its subcutaneous administration instead of the traditional intravenous infusion.

The lawsuit, filed on April 24, 2025, in the U.S. District Court in New Jersey, alleges infringement of 15 of Halozyme's patents, including US Patent No. 11,041,149. All asserted patents belong to a single patent family and stem from Halozyme's extensive research into modifications of human hyaluronidase (PH20), leading to their patented MDASE™ technology which enables rapid subcutaneous drug administration. United States Patent No. 11,041,149, consistent with this technology, broadly covers modified human hyaluronidase enzymes and their use in facilitating drug delivery. The case is assigned to District Judge Esther Salas and Magistrate Judge Joel R. Abelow.

This litigation is particularly notable as it targets Merck's strategy to extend the market exclusivity of its blockbuster cancer immunotherapy, KEYTRUDA®. With Keytruda's intravenous formulation facing patent expiry from 2028, the subcutaneous version, Keytruda Qlex, approved by the FDA in September 2025, represents a critical effort by Merck to maintain its market share by offering a more convenient and faster administration option for patients. Halozyme seeks significant damages and injunctive relief to block the commercialization of SC Keytruda, also alleging willful infringement, underscoring the high stakes involved for both companies in the competitive oncology market. Merck has also filed post-grant reviews against several of Halozyme's patents, demonstrating an ongoing intellectual property dispute between the parties.

The patent infringement litigation, Halozyme, Inc. v. Merck Sharp & Dohme Corp. et al. (Case number: 2:25-cv-03179 (ES) (JRA)), filed in the U.S. District Court in New Jersey, concerns Halozyme's allegations that Merck's subcutaneous KEYTRUDA® formulation infringes several of its patents, including US 11041149. Halozyme seeks damages and injunctive relief, also alleging willful infringement. The case is currently ongoing, with significant activity at both the district court and the Patent Trial and Appeal Board (PTAB).

Here are the key legal developments in chronological order:

• Filing & Initial Pleadings:

  • 2025-04-24: Halozyme, Inc. filed its Complaint for Patent Infringement against Merck Sharp & Dohme Corp., alleging infringement of 15 of its patents, including US 11041149.
  • 2025-05-15: Merck Sharp & Dohme Corp. was formally substituted as the defendant by Merck Sharp and Dohme LLC via a stipulation and order. Merck Sharp and Dohme LLC was granted 60 days from this date to file its answer or otherwise respond to the complaint.
  • Merck likely filed its answer and potentially counterclaims around 2025-07-14, aligning with the 60-day deadline, though specific docket entries for the answer were not explicitly found.

• Pre-trial Motions of Substance:

  • Motions to Stay: Merck filed motions to stay the district court litigation pending the outcome of parallel Post-Grant Review (PGR) proceedings at the PTAB. Halozyme has opposed these motions.
  • 2026-01-07: The court granted a motion for the issuance of Letters Rogatory, indicating international discovery efforts.
  • January - February 2026: Parties engaged in disputes regarding a Discovery Confidentiality Order (DCO).
  • 2026-02-19: The Discovery Confidentiality Order was signed by Magistrate Judge Jose R. Almonte.

• Claim Construction (Markman):

  • As of May 2026, there has been no explicit Markman hearing or claim construction order issued in the district court case. However, in related PTAB PGR proceedings, the Board stated it would interpret claims using the same standard as in a civil action under 35 U.S.C. § 282(b).

• Discovery Milestones:

  • Key discovery activity in early 2026 centered on establishing a Discovery Confidentiality Order, which was finalized in February, and the issuance of Letters Rogatory in January to facilitate discovery.

• Trial Events, Verdict, and Post-trial Motions:

  • No such events have occurred, which is typical for a patent litigation case filed relatively recently (April 2025) and with ongoing PTAB proceedings.

• Parallel PTAB IPR/PGR Proceedings and their Effect:

  • Beginning in November 2024, Merck initiated multiple Post-Grant Reviews (PGRs) against numerous Halozyme patents related to modified PH20 hyaluronidase polypeptides, arguing invalidity on grounds including lack of written description and enablement. These PGRs are explicitly linked to the ongoing district court litigation.
  • US 11041149, the patent specifically at issue in this case summary, is considered by Halozyme to be one of its "Fortress of 3" patents (along with US 10,865,400 and US 11,066,656) which are less susceptible to PGR challenges based on "lack of written description/enablement" due to their older priority dates predating the America Invents Act (AIA) cutoff. To challenge these specific patents on such grounds, Merck would likely need to do so in district court or through an Inter Partes Review (IPR), which is limited to prior art. While US 11041149 is listed as a related patent in some PGR documents, there is no indication that a PGR specifically challenging its validity was instituted on "written description" or "enablement" grounds.
  • 2025-09-08: The PTAB instituted PGR2025-00017 against Halozyme's U.S. Patent No. 12,110,520.
  • 2025-10-01 to 2025-10-02: The PTAB instituted PGR2025-00033 against US 12,049,652 and PGR2025-00039 against US 12,104,185.
  • 2025-10-10: The PTAB instituted PGR2025-00046 against Halozyme's U.S. Patent No. 12,091,692.
  • 2025-10-16: The PTAB instituted PGR2025-00052 against US 12,264,345, PGR2025-00024 against US 12,060,590, and PGR2025-00030 against US 12,054,758. Prior to these decisions, Halozyme disclaimed multiple claims in some of these patents.
  • 2025-10-17 (effective 2025-10-20): The USPTO Director reclaimed authority over all IPR and PGR institution decisions, which were previously delegated to three-judge PTAB panels. The Director now consults with PTAB judges but makes the ultimate decision on institution.
  • 2026-05-12: In a significant development, the PTAB issued a Final Written Decision ruling that all challenged claims (1-4, 8-21) of Halozyme's U.S. Patent 11,952,600 were invalid. This patent was one of the MDASE patents asserted against Merck.

• Present Posture:

  • The district court case remains active ("Open"). The court is awaiting a joint letter from the parties by 2026-06-09, advising on the status of the matter following the Final Written Decision of the PTAB, indicating the ongoing influence of the PTAB proceedings on the litigation's direction. The invalidation of US 11,952,600 claims is a major development that could impact the scope of the infringement claims in the district court.

Halozyme, Inc. is represented by attorneys from Quinn Emanuel Urquhart & Sullivan, LLP, and local counsel from Walsh Pizzi O'Reilly Falanga LLP.

Here is a breakdown of the identified counsel for Halozyme, Inc.:

Quinn Emanuel Urquhart & Sullivan, LLP (Attorneys for Plaintiff)

• David A. Nelson

  • Role: Lead Counsel (pro hac vice forthcoming as of May 2025).
  • Office Location: Chicago, Illinois.
  • Experience Note: Quinn Emanuel is widely recognized for its intellectual property and patent litigation practice and has represented Halozyme in related proceedings, including securing a preliminary injunction against Merck in Germany regarding SC Keytruda.

• Jeffrey S. Gerchick

  • Role: Lead Counsel (pro hac vice forthcoming as of May 2025).
  • Office Location: Washington, D.C.
  • Experience Note: Mr. Gerchick is a partner at Quinn Emanuel and focuses on intellectual property litigation.

• Zachariah B. Summers

  • Role: Lead Counsel (pro hac vice forthcoming as of May 2025).
  • Office Location: Los Angeles, California.
  • Experience Note: Mr. Summers is a partner at Quinn Emanuel, focusing on high-stakes intellectual property and patent litigation.

• Lauren Martin

  • Role: Lead Counsel (pro hac vice forthcoming as of May 2025).
  • Office Location: Boston, Massachusetts.
  • Experience Note: Ms. Martin is an attorney at Quinn Emanuel involved in patent disputes.

Walsh Pizzi O'Reilly Falanga LLP (Local Counsel)

• Liza M. Walsh

  • Role: Local Counsel.
  • Office Location: Newark, New Jersey.
  • Experience Note: Ms. Walsh is a founding partner of the firm and has extensive experience in complex litigation, including intellectual property matters in New Jersey federal courts.

• Katelyn O'Reilly

  • Role: Local Counsel.
  • Office Location: Newark, New Jersey.
  • Experience Note: Ms. O'Reilly is a partner at the firm and practices in complex commercial and intellectual property litigation.

• Lauren R. Malakoff

  • Role: Local Counsel.
  • Office Location: Newark, New Jersey.
  • Experience Note: Ms. Malakoff is an attorney at the firm with experience in various litigation matters.

Counsel of Record for Merck Sharp & Dohme Corp. and Merck Sharp and Dohme LLC

Merck Sharp & Dohme Corp. and Merck Sharp and Dohme LLC are represented by O'Melveny & Myers LLP as lead counsel, with Walsh Pizzi O'Reilly Falanga LLP serving as local counsel. Merck also has in-house counsel involved in the litigation.

Here is a detailed breakdown of the identified counsel:

• Benjamin Haber

  • Role: Lead Counsel
  • Firm: O'Melveny & Myers LLP, Los Angeles, CA
  • Experience Note: Mr. Haber is listed as lead counsel for Merck Sharp & Dohme LLC in PTAB proceedings, specializing in patent litigation before the Patent Trial and Appeal Board.

• William M. Fink

  • Role: Back-Up Counsel (likely Lead Counsel for district court purposes)
  • Firm: O'Melveny & Myers LLP, Washington, DC
  • Experience Note: Mr. Fink is identified as back-up counsel for Merck in PTAB proceedings, focusing on patent matters.

• Robert F. Shaffer

  • Role: Back-Up Counsel (Pro Hac Vice Pending)
  • Firm: O'Melveny & Myers LLP, Washington, DC
  • Experience Note: Mr. Shaffer is listed as back-up counsel for Merck in PTAB proceedings, with pro hac vice status pending in the district court.

• Caitlin P. Hogan

  • Role: Back-Up Counsel
  • Firm: O'Melveny & Myers LLP, New York, NY
  • Experience Note: Ms. Hogan is identified as back-up counsel for Merck in PTAB proceedings, involved in the overall patent litigation strategy.

• Constance P. Lee

  • Role: Back-Up Counsel
  • Firm: O'Melveny & Myers LLP, Washington, DC
  • Experience Note: Ms. Lee is listed as back-up counsel for Merck in PTAB proceedings.

• Mark Stewart

  • Role: In-House Counsel
  • Firm: Merck Sharp & Dohme LLC, Rahway, NJ
  • Experience Note: Mr. Stewart serves as VP-Global IP Litigation for Merck Sharp & Dohme LLC and is listed as in-house counsel for PTAB proceedings.

• Aaron G. Clay

  • Role: In-House Counsel
  • Firm: Merck Sharp & Dohme LLC, Rahway, NJ
  • Experience Note: Mr. Clay is a Director of Global Litigation & Patents at Merck Sharp & Dohme Corp. and has prior experience in patent litigation, post-grant proceedings, and appeals related to pharmaceuticals and biologics as Of Counsel at Finnegan, Henderson, Farabow, Garrett & Dunner LLP.

• Liza M. Walsh

  • Role: Local Counsel
  • Firm: Walsh Pizzi O'Reilly Falanga LLP, Newark, NJ
  • Experience Note: Ms. Walsh is a founding partner with extensive experience in complex commercial litigation, including intellectual property and trade secret litigation.

• Lauren R. Malakoff

  • Role: Local Counsel
  • Firm: Walsh Pizzi O'Reilly Falanga LLP, Newark, NJ
  • Experience Note: Ms. Malakoff is an attorney at Walsh Pizzi O'Reilly Falanga LLP, supporting litigation efforts.

While a complete PACER docket for the District Court case (2:25-cv-03179) detailing all appearing counsel was not directly accessible, information from related PTAB proceedings and general firm representations for Merck in patent litigation provides a strong indication of their legal team. Specifically, O'Melveny & Myers LLP is identified as representing Merck in PTAB challenges related to this litigation, and their attorneys are often involved in parallel district court cases. Walsh Pizzi O'Reilly Falanga LLP is the local counsel for Halozyme in this case, but also represents other pharmaceutical companies in patent matters, suggesting they are a common local firm for such disputes in the District of New Jersey.

Other potential lead counsel for Merck in general patent litigation, though not explicitly linked to this specific case in the immediate search results, could include firms like Williams & Connolly LLP, which has defended Merck in patent litigation related to its Keytruda product in other instances, or Quinn Emanuel Urquhart & Sullivan, LLP, which has a strong life sciences patent litigation practice and has represented Merck in various Hatch-Waxman and other patent disputes. However, the available information specifically for the Halozyme v. Merck case points to O'Melveny & Myers LLP as the primary external lead counsel.