U.S. Patent Office Re-Institutes Post Grant Review of Seagen Patent in Dispute between Daiichi Sankyo and Seagen

TOKYO & BASKING RIDGE, N.J.--(BUSINESS WIRE)-- Daiichi Sankyo Co., Ltd. (TSE: 4568) (hereinafter, Daiichi Sankyo) announced today that the U.S. Patent and Trademark Office (PTO) granted its request to re-institute post-grant review (PGR) of the patentability of certain claims of Seagen’s U.S. patent 10,808,039 (the ’039 patent).

“We are very pleased that the PGR will be reinstituted given the PTO’s determination that our petition presented compelling evidence of unpatentability of the ’039 patent,” said Naoto Tsukaguchi, Corporate Officer and General Counsel, Daiichi Sankyo, Co., Ltd.

On December 23, 2020, Daiichi Sankyo filed a petition with the U.S. PTO for post-grant review contesting the patentability of certain claims of the ’039 patent. On April 7, 2022, the U.S. PTO initiated post-grant review of the ’039 patent to determine whether the claims of that patent should not have originally been granted. On July 15, 2022, the U.S. PTO granted Seagen’s request for rehearing of the decision to institute post-grant review, deciding not to proceed with the PGR process. On February 7, 2023, a PTO Precedential Opinion Panel issued an order instructing the original PGR panel to decide whether the PGR should be reinstituted by applying the applicable standard of whether Daiichi Sankyo’s petition presented compelling evidence of unpatentability.

About Daiichi Sankyo

Daiichi Sankyo is dedicated to creating new modalities and innovative medicines by leveraging our world-class science and technology for our purpose “to contribute to the enrichment of quality of life around the world.” In addition to our current portfolio of medicines for cancer and cardiovascular disease, Daiichi Sankyo is primarily focused on developing novel therapies for people with cancer as well as other diseases with high unmet medical needs. With more than 100 years of scientific expertise and a presence in more than 20 countries, Daiichi Sankyo and its 16,000 employees around the world draw upon a rich legacy of innovation to realize our 2030 Vision to become an “Innovative Global Healthcare Company Contributing to the Sustainable Development of Society.” For more information, please visit: www.daiichisankyo.com.

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Global/Japan:

Koji Ogiwara

Daiichi Sankyo Co., Ltd.

ogiwara.koji.ay@daiichisankyo.co.jp

+81 3 6225 1126 (office)

US

Kim Wix

Daiichi Sankyo, Inc.

kwix@dsi.com

+1 908 992 6633

Investor Relations Contact:

DaiichiSankyoIR@daiichisankyo.co.jp

Source: Daiichi Sankyo Co., Ltd.