CX 516, a compound synthesized by Cortex Pharmaceuticals using Ampakine® technology licensed from the University of California, was in clinical investigations for the treatment of Alzheimer's disease, schizophrenia, fragile X syndrome and autism, and sleep disorders, however, development of this drug candidate has been discontinued. CX 516 had an extremely short halflife in humans, very low potency and failed to show any benefits in phase II studies. The compound did have a good safety profile, reducing concerns about the toxicity of excess glutamate. Cortex subsequently terminated clinical development of CX 516.