Bristol Myers Squibb (NYSE:BMY) started off the week by delivering a double-dose of good news regarding its cancer drug Opdivo: In two late-stage clinical trials testing the drug in patients with kidney cancer and mesothelioma, it met its primary endpoints.

In the CheckMate-9ER clinical trial, the combination of Opdivo and Exelixis' (NASDAQ:EXEL) Cabometyx improved progression-free survival -- the time it takes for the tumor to start growing again while the patient remains alive -- compared to Pfizer's (NYSE:PFE) Sutent in previously untreated kidney cancer patients. The combination also improved overall survival and had a higher response rate than Sutent. The companies are saving the full results to release at an upcoming medical conference, so investors will have to wait to see the exact extent of the improvement over Sutent.

Opdivo is already approved for use in combination with Bristol Myers Squibb's Yervoy in patients with previously untreated kidney cancer, so the results are a bigger deal for Exelixis than the larger pharmaceutical company. Shares of Exelixis closed trading Monday up more than 21% Monday, while Bristol Myers was up 1.8%. The broad market S&P 500 index, by contrast, was down by 1.8%. 

Doctor showing a report to a patient in a hospital bed

Image source: Getty Images.

In the mesothelioma trial, CheckMate-743, Opdivo plus Yervoy improved overall survival compared to standard chemotherapy. And here too, Bristol Myers is saving the data to be released at an upcoming medical meeting.

Opdivo is approved by the Food and Drug Administration to treat 11 different types of cancer. The drug works by blocking a protein called programmed death receptor-1 (PD-1) on immune cells that tumor cells use to signal to the immune cells that they shouldn't be attacked. By blocking PD-1, Opdivo allows the immune system to attack the tumor.