Halozyme Therapeutics Inc. Secures Patent Ruling Against Merck’s Keytruda SC in Europe

Halozyme Therapeutics Inc. (Nasdaq: HALO) obtained a decisive patent ruling from the Dutch court of the Hague that bars Merck & Co. from marketing its newly approved subcutaneous formulation of Keytruda (pembrolizumab) in several European markets. The decision, announced on 7 October 2026, follows a sustained legal battle in which Halozyme asserted infringement of its patented ENHANZE drug‑delivery technology.

Key Points of the Ruling

  • Infringement Finding: The court found that Merck’s injectable Keytruda SC infringed Halozyme’s patent covering the use of recombinant human hyaluronidase and associated enzymes to enhance subcutaneous drug delivery.
  • Markets Affected: Merck is prohibited from manufacturing, marketing, and selling the Keytruda SC formulation in the Netherlands, Belgium, Luxembourg, Austria, France, Germany, Denmark, and Switzerland.
  • Court’s Decision Date: The ruling was issued on 7 October 2026, following a petition submitted by Halozyme on 4 October 2026.
  • Implications for Merck: The injunction undermines Merck’s strategy to extend the commercial life of Keytruda, its flagship immuno‑oncology product, ahead of the expiration of its original patent and exclusivity period.

Background of the Dispute

Halozyme’s ENHANZE platform, based on recombinant human hyaluronidase, enables higher drug concentrations to be delivered subcutaneously. Halozyme has licensed this technology to several pharmaceutical partners and has defended its intellectual property aggressively.

Merck’s Keytruda SC was developed to offer a more convenient, injectable form of the drug for patients who previously required intravenous infusions. Merck’s application for market authorization in the European Economic Area was withdrawn in October 2025 after the Dutch court denied its request to rely on a prior‑art patent. The court’s refusal was a precursor to the 2026 injunction.

Market and Investor Impact

  • Halozyme’s Share Price: Following the announcement, Halozyme’s shares increased, reflecting the company’s strengthened position in the drug‑delivery technology space.
  • Merck’s Share Price: Merck’s shares experienced a temporary decline as the market priced in the loss of access to key European markets for its new Keytruda formulation.
  • Strategic Positioning: The ruling positions Halozyme as a leading enabler for subcutaneous therapies and may expand its partnership portfolio beyond the collaboration with argenx SE, which was recently extended to include two additional therapeutic targets.

Subsequent Developments

  • Halozyme–argenx Collaboration Expansion: On 13 October 2026, Halozyme announced the expansion of its partnership with argenx SE, granting exclusive access to the ENHANZE platform for two new therapeutic targets.
  • Regulatory Filings: Halozyme has submitted further patent applications to strengthen its intellectual property portfolio in the EU, anticipating future conflicts with large biopharmaceutical companies.

Conclusion

Halozyme’s victory in the Dutch patent court demonstrates the commercial viability and legal robustness of its ENHANZE drug‑delivery technology. The ruling not only restricts Merck’s immediate commercial opportunities in Europe but also reinforces Halozyme’s standing as a critical technology partner in the biopharmaceutical industry.