Treatment of Fragile-X Associated Tremor/Ataxia Syndrome (FXTAS) With Allopregnanolone

Allopregnanolone is an endogenous inhibitory pregnane neurosteroid. It is synthesized from progesterone, and is a potent positive allosteric modulator of the action of γ-aminobutyric acid at GABAA receptor. Subjects will receive up to 12 infusions in the study. Subjects will all begin with 2.0 mg dosage. If tolerated, the next infusion will be 4.0 mg, and if that is tolerated, the next infusion will be 6.0 mg. Subject infusions will remain stable at the highest dosage tolerated for the remainder of the study. Each infusion will consist of 2.0 mg, 4.0 mg, or 6.0 mg aliquots of the 0.5 mg/ml allopregnanolone in 6% sulfobutylether-β-cyclodextrin with 0.9% sodium chloride injection solution.