PTAB challenges

Proceedings overview

US patent 11066656 is currently subject to one active Inter Partes Review (IPR) proceeding, IPR2026-00314, which is in the pending phase. This means that the patent's validity is currently being challenged before the Patent Trial and Appeal Board (PTAB), but no claims have been invalidated or sustained by a final decision yet. For a defendant, this indicates that the patent is under active scrutiny, and the ultimate scope of its enforceable claims is uncertain pending the outcome of this proceeding.

IPR2026-00314 — Merck Sharp & Dohme LLC v. Halozyme Inc.

• Type: Inter Partes Review
• Filed: 2026-03-23
• Status: Pending. This proceeding is currently undergoing preliminary review by the PTAB to determine whether to institute a trial. A decision on institution is expected by September 23, 2026.
• Judge panel: Not publicly available prior to an institution decision.
• Petition grounds: The specific claims challenged and prior art grounds are not yet public, as the institution decision has not been rendered. However, the patent US11066656 generally covers "PH20 polypeptide variants, formulations and uses thereof," particularly modified hyaluronidase polypeptides exhibiting increased stability and/or activity.
• Institution decision: The decision on whether to institute an IPR trial is pending, with a statutory deadline of September 23, 2026. As of March 3, 2026, the parties were actively litigating a motion to terminate filed by Halozyme Inc., alleging that Merck Sharp & Dohme LLC failed to name its corporate parent, Merck & Co., Inc., as a real party-in-interest. The Board authorized the Petitioner to file a declaration addressing these factual assertions by March 12, 2026, and to coordinate a deposition with the Patent Owner, with the transcript due by March 27, 2026.
• Final Written Decision (if issued): Not applicable, as the proceeding is pending institution.
• Settlement / termination: Not applicable yet. The RPI motion represents an active preliminary dispute.
• Appeal: Not applicable yet.
• Defensive value: The existence of an active IPR means that the validity of patent US11066656 is formally contested. While no claims have been invalidated, the outcome of this IPR could significantly alter the patent's landscape. Defendants should monitor the institution decision closely, as institution indicates the PTAB's initial finding of a reasonable likelihood of invalidity for at least one challenged claim.

Strategic summary

Currently, all claims of US patent 11066656 are UNTESTED by a Final Written Decision from the PTAB. There is one pending Inter Partes Review, IPR2026-00314, challenging the patent. This means that while the validity of the patent is under challenge, no claims have been definitively canceled or sustained by the PTAB.

The estoppel landscape for IPR2026-00314 has not yet formed. Estoppel under 35 U.S.C. § 315(e)(2) only applies after a Final Written Decision is issued and would bar the petitioner (Merck Sharp & Dohme LLC) and its privies from raising any ground they raised or reasonably could have raised in a subsequent district court action or other USPTO proceeding. As the proceeding is still in the pre-institution phase, these estoppel provisions are not yet in effect.

Regarding pattern signals, Merck Sharp & Dohme LLC has demonstrated an active strategy of challenging Halozyme Inc.'s patent portfolio, with multiple IPRs and PGRs filed against related patents,,. The ongoing dispute over the real party-in-interest in IPR2026-00314 and other related cases (e.g., PGR2025-00003 mentioned in) indicates that Halozyme Inc. is actively defending its patents at the PTAB.

Recommended next steps

For anyone facing assertion of US patent 11066656, the primary focus should be on the upcoming institution decision for IPR2026-00314. The PTAB's deadline to decide whether to institute a trial in this IPR is September 23, 2026.

Monitor the PTAB's Electronic Filing System (EFS-Web) for IPR2026-00314 to obtain the petition, the Patent Owner Preliminary Response, and any subsequent filings related to the real party-in-interest dispute, as these documents will reveal the specific claims challenged and the prior art relied upon by Merck Sharp & Dohme LLC. The PTAB's decisions, including institution decisions, are typically made public via the USPTO PTAB Decisions portal.

Given the active litigation of the real party-in-interest issue, it is also advisable to track this procedural aspect, as its resolution could impact the progression of the IPR.