** Shares of drugmaker Merck MRK.N rise 1.4% to $122.50 premarket

** MRK says its cancer drug Keytruda met the main goal in a late-stage trial of patients with advanced or recurrent endometrial cancer, a cancer that starts in the lining of the uterus

** Keytruda helped patients with dMMR tumors, a genetic feature that makes it harder for cells to repair DNA damage, live longer without their disease worsening versus chemotherapy

** MRK says Keytruda is the first immunotherapy to show better progression-free survival than carboplatin and paclitaxel chemotherapy in this patient group

** Early data also showed a trend toward improved overall survival, though results are not yet final

** Merck says it plans to discuss the data with regulators and present detailed results at a medical meeting

** As of last close, stock up ~15% YTD