SUVN-502 With Donepezil and Memantine for the Treatment of Moderate Alzheimer's Disease- Phase 2a Study

Inclusion Criteria: * Has a diagnosis of probable Alzheimer's disease based on the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA) criteria at least 1 year prior to the screening visit. * Has a score between 12 and 20 inclusive on the MMSE at the screening and baseline visits. * Has a MRI or CT scan performed within 12 months prior to screening with findings consistent with the diagnosis of dementia due to Alzheimer's disease without any other clinically significant comorbid pathologies. * Must be receiving treatment with stable doses of donepezil HCl and memantine HCl for at least 3 months prior to the screening visit * Availability of an eligible and reliable caregiver * Must be living in the community or an assisted living facility. * Must be ambulatory or ambulatory aided (use of cane or walker). * Is not pregnant or planning to become pregnant during the study. * Subject (or subject's legally acceptable representative) and caregiver must sign an Informed Consent to participate in the study. Exclusion Criteria: * Has a diagnosis of dementia due to other than Alzheimer's Disease * Is taking cholinesterase inhibitors other than donepezil HCl or taking doses of donepezil HCl other than 10 mg * Is taking doses of memantine HCl other than 10 mg bid or Namenda XR® 28 mg qd. * Has uncontrolled cardiac disease or hypertension. * Has clinically significant renal or hepatic impairment. * Has cancer or a malignant tumor, untreated thyroid disorder or has a history of seizure disorder * Is treated or likely to require treatment during the study, with any medications prohibited by the study protocol.