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Seagen antibody-drug conjugate patent suffers dual defeats on appeal in US

By Melissa Ritti ( December 2, 2025, 22:02 GMT | Insight) -- A patent owned by Seagen was declared anticipated Tuesday by the same anti-cancer treatment it accused of infringement in 2020. The US Court of Appeals for the Federal Circuit not only wiped out a $41 million jury award in favor of the US-based pharmaceutical company, they voiced the “suspicion” Seagen drafted its patent claims “specifically to encompass” Enhertu — the blockbuster drug jointly developed by Daiichi Sankyo and AstraZeneca.A Seagen patent claiming priority to a 2004 application that encompassed almost four billion pentapeptides and 47 million species of tetrapeptides was held invalid Tuesday by the US Court of Appeals for the Federal Circuit....

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