Daiichi Sankyo Shuts Down Plexxikon to Focus on Three Core ADC Therapies: Enhertu, Dato-DXd, and HER3-DXd

On January 12, Daiichi Sankyo announced that it would close all operations of Plexxikon. Plexxikon, a subsidiary acquired by Daiichi Sankyo in 2011 for $935 million, has two marketed anticancer drugs and six drugs already in clinical trials. The company will continue to operate until the end of March.

According to a press release from Daiichi Sankyo, this adjustment aims to maximize the concentration of resources on the development of three key ADC products: Enhertu, Dato-DXd, and HER3-Dxd.

Plexxikon, Inc. was founded in 2001 and has successfully brought two cancer therapies to FDA approval in 21 years: Zelboraf, for melanoma in collaboration with Roche, and Turalio, for tenosynovial giant cell tumor. However, the sales of these two products are modest, with Zelboraf reaching an annual peak of approximately $200 million, and Turalio targeting only rare tumor types.

At the same time, Enhertu remains a key project for Daiichi and its partner AstraZeneca, which in 2019 paid $1.35 billion upfront for the collaboration to develop the drug, which could ultimately be worth $6.9 billion.

AstraZeneca/Daiichi Sankyo positions ADC Enhertu as the next blockbuster in breast cancer. In September 2021, the latest clinical data showed that Enhertu outperformed Roche's Kadcyla in a head-to-head study targeting certain second-line breast cancer patients, reducing the risk of disease progression or death by 72%.

At the same time, AstraZeneca and Daiichi are also collaborating on Dato-DXd, reaching a deal worth up to $6 billion in July 2020. For this project, the competitor of the two companies is Gilead's Trodelvy, which has already been approved by the FDA for triple-negative breast cancer and urothelial cancer.

Consistent with the future development strategy of the pipeline presented at the R&D Day in December, Daiichi Sankyo stated in a press release on Wednesday that focusing on the development of these three ADCs is one of Daiichi's key growth strategies for the future. The company will adopt the "3 and Alpha Strategy" to first maximize the therapeutic potential of the three main ADC products while developing subsequent potentially important candidates, including DS-7300, DS-6000, and others.

Source: Daiichi Sankyo R&D Day