Court won't raise Seagen damages award in Enhertu patent dispute

A Texas court has confirmed the $41.8 million damages awarded to Seagen in its patent dispute with Daiichi Sankyo over beast cancer drug Enhertu, but declined to raise the sum despite concluding that the infringement was 'wilful'.

Seagen won a lawsuit in April which claimed that Enhertu (trastuzumab deruxtecan) infringes a patient it holds (No. 10,808,039) covering antibody-drug conjugates that include auristatin compounds coupled to an antibody via a linker molecule.

The jury in the case awarded Seagen an amount for damages based on past royalties that should have been paid on Enhertu sales in the US to date.

In the latest development, the court has decided that an increase in damages isn't warranted "despite the jury's finding of wilfulness," said Daiichi Sankyo in a statement (PDF) today.

The Japanese drugmaker – which has partnered with AstraZeneca on commercialising Enhertu – pledged to "vigorously defend its rights and explore available post-trial motions and remedies to contest the judgment and damages awarded to Seagen."

Seagen had asked the court to look into the possibility of increasing damages, as well as making a request for royalties on future sales until the expiry of the '039 patent in November 2024. The court has not yet ruled on the future royalties matter.

Daiichi Sankyo said that the impact on its consolidated financials for the fiscal year ending 31 March 2023 "is currently being evaluated and will be announced as soon as possible."

An award for future royalties could be a big windfall for Seagen, currently rumoured to be a takeover target for Merck & Co, given that Enhertu sales are growing quickly and set to accelerate with additional approvals.

It is already approved as a second- and third-line treatment for HER2-positive breast cancer and as a second-line therapy for gastric and gastroesophageal junction (GEJ) cancer, but is poised to move into earlier lines of treatment as well as breast and gastric cancers with low HER2 expression levels.

In February, for example, Enhertu scored its first phase 3 win in HER2-low breast cancer in the DESTINY-Breast04 trial, which analysts at Credit Suisse said could unlock $3 billion in additional sales for the drug.