Seagen Patent at Heart of $42M Verdict Endures Daiichi Challenge

A Seagen Inc. patent whose infringement by Enhertu—a breast-cancer treatment marketed by Daiichi Sankyo Co. in the US via AstraZeneca PLC—led a Texas jury in April to award Seagen $41.8 million has survived Daiichi’s bid for findings that it was unenforceable and shouldn’t have been issued.

Daiichi “has failed to meet its burden of clear and convincing evidence” to show the patent “should be unenforceable under the equitable theory of prosecution laches,” Judge Rodney Gilstrap of the US District Court for the Eastern District of Texas wrote in a July 15 opinion.

Gilstrap, who presided over a bench ...