Summit Therapeutics Inc. shares rose after it said Astra Zeneca Plc would make a $2 billion strategic equity investment in the cancer drugmaker to jointly develop drugs. The investment in convertible preferred shares represents a common stock price of $18.36, an almost 19% premium to Summit’s closing share price Monday. Summit shares climbed 19% in trading after New York markets closed.

The companies will collaborate on work involving one of Summit’s experimental drugs, ivonescimab, combined with Astra Zeneca’s sonesitatug vedotin in gastrointestinal cancers. Those studies will start “imminently,” Summit said. Each company will retain the rights to their molecules.

The companies also intend to do more trials with ivonescimab and other Astra Zeneca compounds, including antibody drug conjugates. The companies will jointly fund the studies and Astra Zeneca will sponsor them.

Ivonescimab is Summit’s lead candidate. It’s being tested in certain types of lung cancer and colorectal cancer, among other trials. Data from a study of more than 500 patients in China earlier this year showed positive results but some doctors questioned whether they would apply to a US population that’s typically older than the participants in the trial.