** Shares of medical device maker NeuroPace NPCE.O fall 15% to $15.02 premarket

** Co, citing preliminary data, says neuromodulation therapy for a group of genetic epilepsy syndromes failed to meet main efficacy goal in the overall population in a 2-year study

** The device, RNS System, is implanted in the skull to constantly monitor brain waves, identifying and disrupting unusual activity that may trigger seizures

** The device, however, showed significant efficacy in a subset of patients, which represents the majority of participants - NPCE

** It is approved in the U.S. to treat focal epilepsy, a type of seizure that affects only one side of the brain and body

** Up to last close, stock up ~58% YTD

(Reporting by Mariam Sunny in Bengaluru)

((Mariam.ESunny@thomsonreuters.com;))