Shares of biotech firm Geron crashed nearly 70 percent in premarket trading Thursday after Johnson & Johnson's Janssen Biotech unit said it will end a partnership with the firm on the cancer drug imetelstat.
"The decision not to continue the collaboration is the result of a strategic portfolio evaluation and prioritization of assets within the robust Janssen portfolio," Janssen said in a press release. "Janssen will work with Geron to transition the imetelstat program back to the company."
It added that patients currently in trials will "continue to be supported through the respective trial protocols, including treatment and follow-up."
The two companies had begun collaborating on the drug in late 2014.
Shares of Geron were trading at around $2.30 before the market opened Thursday morning.