Daiichi Sankyo wins key ADC patent dispute against Seagen

Daiichi Sankyo announced on December 3, 2025, that the U.S. Court of Appeals for the Federal Circuit reversed a lower court's decision, ruling Seagen Inc.'s U.S. Patent No. 10,808,039 ('039 patent) invalid. This judgment vacates the previous finding of patent infringement and the associated damages award against Daiichi Sankyo concerning its ADC products. The prior ruling from October 17, 2023, had ordered Daiichi Sankyo to pay damages and royalties on ENHERTU® U.S. sales from April 1, 2022, to November 4, 2024.

In a related but separate decision, the Federal Circuit also dismissed Seagen's appeal against a January 2024 decision by the U.S. Patent and Trademark Office. This earlier decision, stemming from Daiichi Sankyo's post-grant review (PGR) challenge, had already invalidated all challenged claims of the '039 patent. The Federal Circuit deemed Seagen's appeal moot, as the '039 patent's invalidity was affirmed in the primary appeal from the Texas decision.

Daiichi Sankyo expressed satisfaction with the Federal Circuit's latest rulings, which nullify the infringement judgment and damages award. This outcome concludes a significant patent dispute, reinforcing Daiichi Sankyo's position in the ADC market.