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.

“This outcome reinforces what we have consistently maintained: the innovations behind Duplex Sequencing are distinct and deserving of strong patent protection,” said Chad Waite, chair of the TwinStrand board of directors. “With every claim of the ’631 patent now upheld, and the PTAB’s ruling last month in our favor on the related ’127 patent, the validity of both patents at the center of our litigation against Guardant Health has been confirmed by the USPTO.”

The USPTO determination follows an October 14, 2026, decision by the USPTO Patent Trial and Appeal Board (PTAB), which rejected Guardant Health’s challenge to all 30 claims of U.S. Patent No. 10,760,127 (the ’127 patent) in an inter partes review. On remand from the U.S. Court of Appeals for the Federal Circuit, the board reconsidered the challenge under a different legal framework than it had previously applied and again ruled in favor of the University of Washington, which owns the ’127 and ‘631 patents and exclusively licenses them to TwinStrand.

Both patents underlie the August 21, 2026, final judgment entered by the U.S. District Court for the District of Delaware in favor of TwinStrand and the University of Washington in its patent infringement litigation against Guardant Health. That judgment preserved a November 2023 jury verdict finding that Guardant Health willfully infringed both patents and awarded more than $245.2 million in damages, accrued royalties for infringement, and interest for sales through May 31, 2026. The court also ordered an ongoing 6% royalty on sales of 11 covered Guardant Health products and services through patent expiration on March 15, 2033. These products and services include: Guardant360 Lab Developed Test; Guardant360 CDx; GuardantOMNI; Guardant Reveal / LUNAR-1; Guardant360 Response; Guardant360 TissueNext; Guardant HEME; GuardantINFINITY / Sirius; Guardant LUNAR-2 / Shield; Guardant COMPANION; and Guardant EXPLORE.

About TwinStrand Biosciences

TwinStrand Biosciences is a precision genomics company advancing highly accurate DNA sequencing through its patented TwinStrand Duplex Sequencing® technology, originally developed at the University of Washington. Duplex Sequencing achieves more than 10,000-fold greater accuracy than conventional next-generation sequencing by independently sequencing and comparing both complementary strands of each DNA molecule. This enables reliable detection of ultra-low-frequency genetic variants that conventional methods often cannot distinguish from background sequencing errors. The technology supports applications across oncology, molecular diagnostics, genetic toxicology and drug development. TwinStrand collaborates with leading pharmaceutical companies, molecular diagnostics developers, academic institutions and research organizations, and its intellectual property portfolio includes more than 150 issued patents and patent applications worldwide. For more information, visit www.twinstrandbio.com.

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