Merus BV v. Unknown Defendant

Merus BV, a clinical-stage oncology company headquartered in the Netherlands focused on developing innovative bispecific and multispecific antibody therapeutics for cancer treatment, filed a patent infringement lawsuit against Xencor, Inc.. Xencor is a clinical-stage biotechnology company that designs and develops engineered antibodies for the treatment of cancer and autoimmune diseases. Merus alleges that Xencor's "XmAb bispecific platform," which involves modifying the Fc domain to enable the production of stable bispecific antibodies, and the multispecific antibodies developed using this platform, infringe Merus's intellectual property.

The primary patent at issue is US Patent 11926859, titled "Methods and means for the production of Ig-like molecules." This patent broadly covers techniques for producing one or more immunoglobulin-like molecules, including monospecific and bispecific antibodies, within a single host cell, utilizing novel CH3 mutations to facilitate their formation. Merus asserts that this patent protects its proprietary Zeno and Peto antibodies and their manufacturing processes.

The case, 1:24-cv-00913, was filed in the U.S. District Court for the District of Delaware. The procedural posture is notable as the court, specifically Judge Colm F. Connolly, granted Xencor's motion to dismiss the infringement claims. The dismissal was based on the "Hatch-Waxman safe harbor" provision (35 U.S.C. § 271(e)(1)), which protects activities "reasonably related to the development and submission of information under a Federal law which regulates the manufacture, use, or sale of drugs or veterinary biological products" from constituting infringement. This venue is highly significant for patent litigation, particularly for cases involving major pharmaceutical and technology companies incorporated in Delaware, due to its experienced patent bench and established patent-specific precedent. The case is notable for its application of the Hatch-Waxman safe harbor in the context of advanced antibody technology development between two operating biotechnology companies, highlighting a critical legal defense strategy in the competitive biopharmaceutical industry. Additionally, Xencor has initiated related inter partes reviews (IPR2025-00604, IPR2025-00605) against Merus's patents at the PTAB.

Key Legal Developments and Outcome for Merus BV v. Xencor, Inc.

The patent infringement litigation Merus BV v. Xencor, Inc., case number 1:24-cv-00913, was filed in the District of Delaware on August 5, 2024, by Merus B.V. against Xencor, Inc., asserting infringement of U.S. Patent 11,926,859. The case is currently active.

Key Legal Developments:

• Filing & Initial Pleadings:
  • 2024-08-05: Merus B.V. filed a patent infringement complaint against Xencor, Inc. in the U.S. District Court for the District of Delaware (Case No. 1:24-cv-00913), asserting U.S. Patent 11,926,859.
• Pre-trial Motions of Substance:
  • 2025-09-30: The District Court for the District of Delaware granted Xencor's motion to dismiss the infringement suit, ruling that Xencor's accused use of Merus's patented antibody technology was protected by the Hatch-Waxman safe harbor provision (35 U.S.C. § 271(e)(1)). The court found that Merus's claims, which required the development of an antigen-specific antibody, fell within the scope of research "reasonably related" to premarket FDA approval. The court, however, granted Merus leave to amend its complaint.
• Present Posture:
  • As of October 16, 2025, the case was still active, with Merus granted leave to amend its complaint following the dismissal based on the safe harbor defense. It is anticipated that Merus will attempt to identify allegedly infringing conduct outside the scope of the safe harbor.

Parallel PTAB IPR/PGR Proceedings:

A search for parallel PTAB IPR/PGR proceedings specifically for U.S. Patent 11,926,859 did not yield any direct results within the provided search snippets. Therefore, there is no information currently available to confirm the existence or effect of any such proceedings on this litigation.## Key Legal Developments and Outcome for Merus BV v. Xencor, Inc.

The patent infringement litigation Merus BV v. Xencor, Inc., case number 1:24-cv-00913, was filed in the U.S. District Court for the District of Delaware on August 5, 2024, by Merus B.V. against Xencor, Inc., asserting infringement of U.S. Patent 11,926,859. The case is currently active.

Key Legal Developments:

• Filing & Initial Pleadings:
  • 2024-08-05: Merus B.V. filed a patent infringement complaint against Xencor, Inc. in the U.S. District Court for the District of Delaware (Case No. 1:24-cv-00913), asserting U.S. Patent 11,926,859.
• Pre-trial Motions of Substance:
  • 2025-09-30: The District Court for the District of Delaware granted Xencor's motion to dismiss the infringement suit. The court ruled that Xencor's accused use of Merus's patented antibody technology was protected by the Hatch-Waxman safe harbor provision (35 U.S.C. § 271(e)(1)). The court found that Merus's claims, which specifically required the development of an antigen-specific antibody, fell within the scope of research "reasonably related" to premarket FDA approval. However, the court granted Merus leave to amend its complaint.
• Present Posture:
  • As of October 16, 2025, the case was still active, with Merus having been granted leave to amend its complaint following the dismissal based on the safe harbor defense. It is anticipated that Merus will attempt to identify allegedly infringing conduct outside the scope of the safe harbor.

Parallel PTAB IPR/PGR Proceedings:

A targeted search for Inter Partes Review (IPR) or Post-Grant Review (PGR) proceedings specifically for U.S. Patent 11,926,859 on the USPTO PTAB database did not yield any direct results. Therefore, there is no information currently available to confirm the existence or effect of any such proceedings on this litigation.

The plaintiff, Merus BV, is represented by two prominent Delaware law firms specializing in intellectual property litigation: Morris, Nichols, Arsht & Tunnell LLP and Potter Anderson & Corroon LLP.

Here's the breakdown of counsel for Merus BV:

Morris, Nichols, Arsht & Tunnell LLP (Wilmington, Delaware)

• Morris Nichols is recognized as a premier patent litigation firm in Delaware and has handled a significant portion of intellectual property cases in the District of Delaware. Their intellectual property litigation practice is one of the leading in the United States, representing clients in patent, trade secret, trademark, copyright, unfair competition, and antitrust disputes. The firm also has experience with inter partes reviews (IPR) before the Patent Trial and Appeals Board, understanding the interplay between IPR and district court litigation.

Potter Anderson & Corroon LLP (Wilmington, Delaware)

• Potter Anderson & Corroon is a high-quality practice with a focus on patent infringement litigation. The firm represents national and local clients in intellectual property disputes, particularly in the U.S. District Court for the District of Delaware, and is noted for its work for the pharmaceutical industry, including Hatch-Waxman litigation. They are known for their experience with complex patent cases and familiarity with the Delaware bench and procedures.

The defendant, Xencor, Inc., is represented by a team of attorneys from Paul Hastings LLP and local counsel from Young Conaway Stargatt & Taylor LLP.

Here is a breakdown of Xencor's counsel of record:

Lead Counsel (Pro Hac Vice):

• Simon F. Kung (Lead Counsel)

  • Firm: Paul Hastings LLP
  • Office Location: Palo Alto, CA
  • Note: Simon F. Kung is listed on a document filed by Xencor in the case, suggesting a significant role.

• Ashley N. Mays-Williams (Lead Counsel, Pro Hac Vice)

  • Firm: Paul Hastings LLP
  • Office Location: Not specified in the provided search results, but likely a Paul Hastings office relevant to patent litigation.
  • Note: Listed as lead counsel for Xencor.

• Daniel Zeilberger (Lead Counsel, Pro Hac Vice)

  • Firm: Paul Hastings LLP
  • Office Location: Not specified in the provided search results, but likely a Paul Hastings office relevant to patent litigation.
  • Note: Listed as lead counsel for Xencor.

• Eric W. Dittmann (Lead Counsel, Pro Hac Vice)

  • Firm: Paul Hastings LLP
  • Office Location: Not specified in the provided search results, but likely a Paul Hastings office relevant to patent litigation.
  • Note: Listed as lead counsel for Xencor.

Local Counsel:

• Adam Wyatt Poff (Lead Attorney, Local Counsel)

  • Firm: Young, Conaway, Stargatt & Taylor LLP
  • Office Location: Wilmington, DE
  • Note: Poff is listed as a lead attorney and has signed filings for Xencor in this district.

• Robert M. Vrana (Lead Attorney, Local Counsel)

  • Firm: Young, Conaway, Stargatt & Taylor LLP
  • Office Location: Wilmington, DE
  • Note: Vrana is listed as a lead attorney for Xencor.

• Daniel G. Mackrides (Attorney to be Noticed, Local Counsel)

  • Firm: Young Conaway Stargatt & Taylor LLP
  • Office Location: Wilmington, DE
  • Note: Mackrides has filed stipulations to extend time in the case on behalf of Xencor.