• To assess the effects of RVT-101 versus placebo on global function as measured by the Clinician's Interview-Based Impression of Change Plus Caregiver Input (CIBIC+) after 24 weeks of treatment • To assess the effects of RVT-101 versus placebo on cognition as measured by the composite z-score of the 7 domains of the Cognitive Drug Research (CDR) computerized assessment system after 24 weeks of treatment (CDR domains include Power of Attention, Continuity of Attention, Quality of Working Memory, Quality of Episodic Memory, Speed of Memory, Cognitive Reaction Time and Reaction Time Variability)