Daiichi Sankyo shuts down Plexxikon subsidiary to streamline Enhertu, ADC development
Daiichi Sankyo is saying goodbye to one of its longtime subsidiaries.
The multinational pharma company announced Wednesday it will shut down all operations of Plexxikon, which it acquired in a $935 million buyout back in 2011. In a release, Daiichi said it’s closing Plexxikon’s offices to “maximize its R&D investment” in its major cancer drug Enhertu as well as two other ADC programs, Dato-DXd and HER3-DXd.
Plexxikon will remain operational until the end of March, Daiichi added. The subsidiary has about 60 employees, all of whom will “transition from employment” from Plexxikon, Daiichi spokesperson Masashi Kawase told Endpoints News in an email.
Kawase added the company couldn’t comment on whether the employees would be retained in other positions at Daiichi.
Founded in 2001, Plexxikon has pushed two cancer therapies to FDA approval in its 21 years: Zelboraf, partnered with Roche for melanoma, and Turalio for tenosynovial giant cell tumors. The latter, a CSF1R inhibitor, faced a bit of a bumpy road in its development path as liver toxicity spurred clinical holds on two separate occasions. Ultimately, the drug was approved in August 2019.
The drugs only generate modest sales, however, as Zelboraf reached a peak of about $200 million per year — far below analyst expectations of $700 million. Turalio is in a similar boat, as it is indicated only for a rare tumor type and not anticipated to pull in big sales.
Enhertu, meanwhile, continues to be a moneymaker for both Daiichi and partner AstraZeneca, which paid $1.35 billion upfront in 2019 to collaborate on the drug in a deal that could ultimately be worth $6.9 billion.
The pair has positioned Enhertu as the next big breast cancer drug, getting approvals in second- and third-line breast cancer settings, as well as for certain types of HER2-positive gastric cancer. In September, new data showed Enhertu blew Roche’s Kadcyla out of the water in a head-to-head study for some second-line breast cancer patients, cutting the risk of disease progression or death by 72%.
But AstraZeneca and Daiichi are also collaborating on datopotamab deruxtecan, or dato-DXd, agreeing to a deal worth up to $6 billion back in July 2020. For that program, the companies are chasing Gilead’s Trodelvy, which got FDA approval in April to treat metastatic TNBC patients in the second line or later as well as an accelerated nod in urothelial carcinoma the same month.
Ensuring these three ADCs flourish is one of Daiichi’s main growth strategies through the first half of the 2020s, the company noted in its release Wednesday.