We had the pleasure during the ASCO 2021 to present in the plenary session the first results from a study we were waiting for for some time, KEYNOTE-564. KEYNOTE-564 is a study in high-risk renal cell cancer, of trying to use adjuvant immunotherapy, with the PB1 inhibitor pembrolizumab to see if there is any impact on outcomes. So this was a randomized phase III double blinded study of pembrolizumab versus placebo for one year in patients with clear cell renal cell cancer, the most common type of kidney cancer. But patients needed to be at risk for developing metastatic disease after a curative intent nephrectomy.
The study enrolled at the end of the day, close to 1,000 patients, 994 patients. The primary endpoint was disease free survival by the investigator assessment. And the first interim result, disease free survival endpoint, was met. The hazard ratio was 0.68, corresponding to a 32% decrease in the risk of recurrence or death.
The study had other endpoints, key secondary endpoint of safety and overall survival. With overall survival, actually the events were limited, only 23% of intended events. But the hazard ratio was 0.54. And these were quite encouraging. It didn't meet the prespecified threshold to say that the OS was positive. But these were encouraging.
Now safety-wise, more treatment discontinuation, more toxicities on the active, on the pembrolizumab arm. But we did not have, luckily, any deaths on study here. Nothing that for pembrolizumab, the drug, it proved in multiple indications already in the metastatic setting. Even in renal cell cancer in the metastatic setting in combination, nothing that jumped out to us.
So we concluded at the end, that this is a statistically significant and clinically relevant result. With a treatment that is tolerated. With toxicities that are manageable. With potentially pembrolizumab being the first immunotherapy to show a benefit in terms of clinical outcomes in the adjuvant setting.