TwinStrand Biosciences (TwinStrand), the pioneer in Duplex Sequencing technology, today announced that the U.S. Patent and Trademark Office (USPTO) has confirmed the patentability of all 23 claims of U.S. Patent No. 10,287,631 (the ‘631 patent), one of two foundational patents for Duplex Sequencing technology at issue in TwinStrand’s patent infringement litigation against Guardant Health, Inc. (Nasdaq: GH). In a November 4, 2026, Notice of Intent to Issue an Ex Parte Reexamination Certificate, the USPTO determined that all claims of the ‘631 patent are patentable without amendment or cancellation, concluding a substantive reexamination proceeding initiated by Guardant Health.

The notice represents the examiner’s final determination on the patentability of the challenged claims. This decision cannot be appealed. The USPTO will now issue a formal reexamination certificate confirming all 23 claims of the ’631 patent.

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