A Two-year Open-label Extension Study of Ganaxolone in Patients With Drug-resistant Partial-onset Seizures

Inclusion Criteria: * Subjects who have completed all scheduled clinical study visits in the previous protocol 1042-0603 and have shown a minimum 35% improvement in mean 28-day seizure frequency over the last three 28-day periods in study 1042-603 as compared to the baseline of study 1042-603. * Subjects whose daily study drug compliance in Study 1042-0603 was 90% or greater, and for whom the investigator feels that the subject was compliant with the full dose as prescribed. * Able to give informed consent in writing, or have a legally authorized representative able to do so, after being properly informed of the nature and risks of the study and prior to engaging in any study-related procedures. * Currently being treated and maintained with a stable regimen of 1, 2, or 3 anti-epileptic drugs (AED) at a consistent dose for one month prior to study entry. * Implanted Vagus Nerve Stimulator (VNS) is permitted and will not count towards the number of concomitant AEDs. * Able and willing to maintain an accurate and complete daily written seizure calendar or has a caregiver who is able and willing to maintain an accurate and complete daily written seizure calendar. * Able and willing to take drug with food twice daily. Ganaxolone must be administered with food. * Sexually active women of childbearing potential (WCBP) must be using a medically acceptable method of birth control and have a negative pregnancy test at Visit 1 and at subsequent visits. Exclusion Criteria: * Have any medical condition that, in the investigator's judgment, is considered to be clinically significant and could potentially affect subject safety or study outcome * Experienced a Serious Adverse Event or a moderate or severe medically important adverse event judged probably or definitely related to open-label ganaxolone in the previous study, 1042-0603 * Have Alanine transferase (ALT; SGPT) or Aspartate transferase (AST; SGOT) levels \> 3 times upper limits of normal (ULN), or total bilirubin \>1.5 time ULN during Study 1042-0603. * Have a history of malignancy within the past 2 years, with the exception of basal cell carcinoma. * Seizures secondary to illicit drug or alcohol use, infection, neoplasm, demyelinating disease, degenerative neurological disease, or central nervous system (CNS) disease deemed progressive, metabolic illness, or progressive degenerative disease. * Have active suicidal plan/intent, or have had active suicidal thoughts in the past 6 months. Have a history of an actual suicide attempt in the last 5 years or more than 1 lifetime actual suicide attempt as classified by the Columbia-Suicide Severity Rating Scale (C-SSRS). * Have a history of drug or alcohol abuse within the past 5 years. As with other AEDs, the use of alcohol is not advised. * Are currently following or planning to follow a ketogenic diet. * Current use of vigabatrin or ezogabine (retigabine; Potiga; Trobalt) is not permitted. * Females who are pregnant, currently breastfeeding or planning to become pregnant during the study. * Inability/unwillingness to withhold grapefruit and grapefruit juice from diet during the entire clinical trial.