 This is a Phase 1b, multi-center, randomized, double-blind, placebo-controlled study designed to evaluate the safety, tolerability, and pharmacokinetics of GC021109 in subjects with mild to moderate Alzheimers Disease as determined by 2011 National Institute on Aging- Alzheimers Association NIA-AA criteria and Mini Mental State Examination MMSE. The Investigator, study site staff, with exception of a designated pharmacistpharmacy technician and all study subjects will be blinded to randomized study medication assignment until database lock. Treatment assignments may be unblinded for select pre-authorized individuals involved in the safety and PK data reviews in order to accurately determine how to proceed with dose escalation. 