Daiichi Sankyo Wins $47M in ADC Patent Case, Pfizer Dispute Ahead

Daiichi Sankyo announced a significant win in its ongoing patent dispute with Seagen, securing $47 million in attorneys' fees and costs, including interest. The battle, which centers around technologies used in Daiichi Sankyo's antibody-drug conjugate (ADC) Enhertu (fam-trastuzumab deruxtecan-nxki), has seen various legal twists over the years.

The conflict dates back to 2008 when Daiichi Sankyo and Seagen entered a partnership to utilize Seagen's ADC technology for developing therapies targeting solid tumors. This collaboration concluded in 2015, but disputes over intellectual property persisted. Enhertu, developed in collaboration with AstraZeneca, became a focal point of contention. Seagen alleged that the technology used in Enhertu was developed during their partnership and thus claimed entitlement to a share of the proceeds from Daiichi Sankyo's $6.9 billion deal with AstraZeneca.

In August 2022, an arbitrator sided with Daiichi Sankyo, declaring Seagen's claims invalid. This ruling was contested by Seagen, which sought to overturn the decision. However, a federal court rejected Seagen's appeal in April 2024, affirming the arbitrator's decision and adding interest to the award, bringing the total to $47 million.

Seagen has also had its share of legal victories. In a 2020 civil action suit, Seagen won a jury verdict awarding $41.82 million in damages over the same patent infringement issue. Additionally, the District Court for the Eastern District of Texas ruled in favor of Seagen in October 2023, ordering Daiichi Sankyo to pay an 8% royalty on all Enhertu sales from April 1, 2022, to November 4, 2024.

Despite the recent ruling in favor of Daiichi Sankyo, the broader patent dispute may not be fully resolved. In January 2024, the U.S. Patent and Trademark Office declared Seagen's contentious patent 10,808,039, which covers the use of auristatin peptides in ADCs through a specific linker technology, invalid.

The history of the dispute is complex. When Seagen claimed a share of Daiichi Sankyo's lucrative contract with AstraZeneca in 2019, Daiichi Sankyo responded by filing a Declaratory Judgement, arguing that Seagen's claims lacked merit. This legal maneuvering has been part of a broader strategy to protect their respective interests in the ADC technology that both companies helped develop during their partnership.

Seagen's acquisition by Pfizer for $43 billion in March 2023 added another layer to the conflict. Pfizer's failure to appeal the ruling before the deadline effectively handed Daiichi Sankyo a decisive win in this phase of the dispute. However, given the ongoing legal proceedings and the overturned patent, the situation remains fluid.

The ongoing legal battles emphasize the high stakes involved in pharmaceutical patents and the lengths companies will go to protect their intellectual property and financial interests. Both Daiichi Sankyo and Seagen have invested heavily in developing innovative cancer therapies, and the outcome of this dispute could have significant implications for their future strategies and partnerships.

As the situation evolves, it remains to be seen how both companies will navigate the complex legal landscape and what impact this will have on their operations and collaborations in the pharmaceutical industry.