To evaluate the efficacy of open-label ganaxolone as adjunctive therapy for uncontrolled seizures in female children with PCDH19 mutation and other rare genetic epilepsies in an open-label proof-of-concept study.

The purpose of this proof-of-concept study is to evaluate ganaxolone as adjunctive therapy for uncontrolled seizures in female children with PCDH19 mutations and other rare genetic epilepsies. After establishing baseline seizure frequency, qualifying subjects will enter the study and be treated with open-label ganaxolone for up to six months.

Key Inclusion Criteria:

1. Have parent or legal guardian available and willing to give written informed consent.
2. Male and female outpatients between 2 and 18 years of age years of age at time of consent.
3. Have any of the following epilepsy syndromes: PCDH19; CDKL5; Dravet Syndrome; Lennox Gastaut Syndrome (LGS); Continuous Spikes and Waves during Sleep (CSWS)
4. Have uncontrolled cluster seizures and/or non-clustered seizures.
5. Subjects should be on a stable regimen of anti-epileptic medication, and generally in good health.
6. Parent or guardian is able and willing to maintain an accurate and complete daily written seizure calendar.
7. Able and willing to take study medication with food, two or three times daily.

Key Exclusion Criteria

1. Have had previous exposure to ganaxolone.
2. Known sensitivity or allergy to any component in the study drug, progesterone, or other related steroid compounds.
3. Exposure to any investigational drug or device < 90 days prior to screening, or plans to participate in another drug or device trial at any time during the study.
4. Concurrent use of vigabatrin, tiagabine, or ezogabine is not permitted.
5. 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, including but not limited to: clinically significant cardiac, renal, pulmonary, gastrointestinal, hematologic or hepatic conditions; or a condition that affects the absorption, distribution, metabolism or excretion of drugs.
6. Have active suicidal plan/intent, or have had active suicidal thoughts in the past 6 months or a suicide attempt in the past 3 years.
7. 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 at the screening and baseline visits.