XCOPRI is a new option to treat adults with partial-onset seizures, which is an often difficult-to-control condition. The safety and efficacy of XCOPRI was established in two randomized, double-blind, placebo-controlled studies that enrolled 655 adults. In these studies, patients had partial-onset seizures with or without secondary generalization for an average of approximately 24 years and median seizure frequency of 8.5 seizures per 28 days during an 8-week baseline period. During the trials, XCOPRI reduced the percent of seizures per 28 days compared with the placebo group.