Merck...announced that the European Commission has approved KEYTRUDA, Merck’s anti-PD-1 therapy, as monotherapy for the treatment of microsatellite instability-high (MSI-H) or deficient mismatch repair (dMMR) tumors in adults with...unresectable or metastatic gastric, small intestine or biliary cancer, who have disease progression on or following at least one prior therapy.

…the NCCN Panel recommends either pembrolizumab or nivolumab, with or without ipilimumab, as second-line treatment options for dMMR/MSI-H advanced SBA.

Three hundred and fifty-one patients with various tumor types were enrolled in KEYNOTE-158 cohort K. The most common tumor types were endometrial (22.5%), gastric (14.5%), and small intestine (7.4%)...ORR among 321 patients in the efficacy population (patients who received ≥1 dose of pembrolizumab enrolled ≥6 months before the data cutoff date) was 30.8% (95% CI, 25.8‒36.2). Median duration of response was 47.5 months (range, 2.1+ to 51.1+ months). Median progression-free survival was 3.5 months (95% CI, 2.3‒4.2 months) and median overall survival was 20.1 months (95% CI, 14.1‒27.1 months)...Pembrolizumab demonstrated clinically meaningful and durable benefit, with high ORR of 30.8%, long median duration of response of 47.5 months, and manageable safety across a range of heavily pretreated, advanced MSI-H/dMMR noncolorectal cancers, providing support for use of pembrolizumab in this setting.

...Merck...today announced the European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP) has adopted a positive opinion recommending approval of KEYTRUDA, Merck’s anti-PD-1 therapy, as monotherapy for the treatment of the following microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) tumors in adults with: unresectable or metastatic colorectal cancer after previous fluoropyrimidine-based combination therapy; advanced or recurrent endometrial carcinoma who have disease progression on or following prior treatment with a platinum-containing therapy in any setting and who are not candidates for curative surgery or radiation; unresectable or metastatic gastric, small intestine or biliary cancer who have disease progression on or following at least one prior therapy....The CHMP’s recommendation was based on results from the Phase 2 KEYNOTE-158 trial as well as results from the Phase 2 KEYNOTE-164 trial...

Previously treated advanced SBA patients received pembrolizumab 200 mg IV q3 weeks until disease progression (PD)....50% of MSI-H patients achieved PR and remain alive without progression.

A 52-year-old man was diagnosed with small bowel adenocarcinoma...The primary lesion showed MSI-H. The patient was started on pembrolizumab therapy in April 2019. The tumor responded well to pembrolizumab(maximum therapeutic effect: PR, 31% reduction), but a new lesion appeared 6 months after the start of this regimen. He continued pembrolizumab therapy for 14 months without adverse events since it appeared to be clinically effective.