MSD’s immunotherapy Keytruda (pembrolizumab) has been approved in the EU for the first-line treatment of metastatic Microsatellite Instability-High (MSI-H) or Mismatch Repair Deficient (dMMR) colorectal cancer.

According to MSD, Keytruda is the first checkpoint inhibitor to be approved in the EU to treat MSI-H or dMMR colorectal cancer.

The European Commission (EC) approval is based on results from the Phase III KEYNOTE-177 trail.

In this study, Keytruda monotherapy significantly reduced the risk of disease progression or death by 40% compared to chemotherapy in this patient population.

Treatment with Keytruda also more than doubled median progression-free survival (PFS) compared to chemotherapy – 16.5 months versus 8.2 months.

For patients treated with Keytruda, the overall response rate (ORR) was 44%, with a complete response rate of 11% and a partial response rate of 33%.

Meanwhile, in the chemotherapy arm, patients demonstrated an ORR of 33%, a complete response rate of 4% and a partial response rate of 29%.

“This decision by the EC, which was based on the important findings from KEYNOTE-177, exemplifies our commitment to using biomarkers such as MSI/MMR to help identify patients who are most likely to respond to Keytruda,” said Dr. Scot Ebbinghaus, vice president, clinical research, Merck Research Laboratories.

“Our efforts in biomarker-driven research across tumour types – including colorectal cancer, the most common type of gastrointestinal cancer – will continue to help us bring new options to patients across the globe,” he added.

In Europe, it is estimated that there were nearly 520,000 new cases of colorectal cancer diagnosed in 2020.

Of these new cases, it is estimated that around 4-20% have tumours that score as either MSI-H or dMMR when testing is performed.