The purpose of this study is to determine the safety, tolerability, and efficacy of VX-765 in subjects with Treatment-resistant Partial Epilepsy

Inclusion Criteria:

• Subjects that are male or female aged 18 to 64 years (inclusive) with a body mass index between 18 and 35 (kg/m2)
• Subjects must have a diagnosis and history of treatment resistant partial onset seizures for which they are taking 1 to 4 concomitant antiepileptic drugs (AED). Treatment resistance is defined as failure to achieve seizure freedom despite adequate use of 2 different AEDs. All AED doses must remain stable for 4 weeks prior to the Screening Visit and throughout the entire study
• Subjects must have had at least 1 electroencephalogram (EEG) consistent with partial epilepsy and a brain magnetic resource imaging (MRI) or computed tomography (CT) scan within 5 years of Screening Visit negative for other confounding conditions
• Subjects must have had at least 6 observable partial seizures in 6 weeks prior to randomization, with at least 1 seizure per week during 3 of the 6 weeks within the Baseline Period
• Subjects who are male or female must agree to use acceptable contraceptive methods as defined in the protocol
• Subjects who are in otherwise good health

Exclusion Criteria:

• Subjects with a history of non-epileptic transient alterations in consciousness
• Subjects who have a history of status epilepticus in the past 12 months
• Subjects whose seizure frequency cannot be quantified
• Subjects who have significant medical illness including kidney, liver, pulmonary or gastrointestinal disease; or unstable or poorly controlled conditions
• Subjects who have clinically significant psychiatric illness
• Subjects with a positive drug screen (excluding any allowed prescribed medications) and history of alcoholism or drug addiction within past 2 years
• Males subjects that have a female partner of childbearing potential who do not agree to use medically approved methods of birth control
• Male subjects that have a female partner who is pregnant, nursing, or is planning to become pregnant during the study period, or within 90 days of the last dose of study drug
• Female subjects who are pregnant or lactating, or who are of reproductive potential who do not agree to use medically approved birth-control methods
• Subjects with a current or prior history of illness precluding them from immunomodulatory therapy (e.g. history of recurrent infections)
• Subjects with active hepatitis B, hepatitis C, or human immunodeficiency virus (HIV)
• Subjects who have participated in any other clinical trials involving an investigational product or device and have received the last dose of study drug within 45 days or 5 half-lives of the Screening Visit