FDA Grants Breakthrough Therapy Designation to Colorectal Cancer Treatment

Keytruda has already been approved for metastatic non-small cell lung cancer and metastatic melanoma.

Patients with colorectal cancer may soon have a new treatment option in their fight against the disease.

The FDA this week granted breakthrough therapy designation to the PD-1 inhibitor pembrolizumab (Keytruda) for the treatment of microsatellite instability-high (MSI-H) metastatic colorectal cancer (mCRC).

The designation was granted based on findings from an ongoing phase 2 study that showed high response rates from Keytruda among patients with heavily pretreated CRC with defective DNA mismatch repair systems (MMR) deficiency, which causes MSI.

“We are committed to understanding the full potential of Keytruda to help patients with a broad range of difficult-to-treat cancers,” said Roger M. Perlmutter, MD, president of Merck Research Laboratories. “The data investigating the use of Keytruda in patients with advanced colorectal cancer whose tumors have substantial evidence of mismatch DNA repair defects have been encouraging, and we appreciate the opportunity that this FDA breakthrough therapy designation provides us to accelerate our effort to bring Keytruda to these patients.”

Findings from the ongoing trial were published in The New England Journal of Medicine (NEJM).

The overall response rate (ORR) with Keytruda was 40% in patients with MMR-deficient mCRC (n = 10), with a 78% progression free survival (PFS) rate at 20 weeks.

The most common adverse events were rash/pruritus (17%), pancreatitis (15%), and thyroiditis/hypothyroidism (10%).

The study noted that patients with Lynch syndrome (n = 11) were less likely to respond to therapy compared with other forms of MMR.

The ORR was 27% among patients with Lynch Sundrome treated with Keytruda compared with 100% in patients with MMR unrelated to Lynch syndrome (n = 6).

Merck is also planning to launch a phase 3 trial to evaluate Keytruda in patients with treatment-naive MMR-deficient mCRC.