F-15599 is a novel agonist with high selectivity and efficacy at serotonin 5-HT(1A) receptors. In signal transduction, electrophysiological and neurochemical tests, F-15599 preferentially activates post-synaptic 5-HT(1A)Rs in rat frontal cortex. Such a profile may translate to an improved profile of therapeutic activity for mood disorders. [(18)F]F-15599 is a radiofluorinated agonist presenting interesting characteristics for probing in vitro and in vivo the high-affinity states of the 5-HT(1A) receptors. The Rett Syndrome Research Trust awarded a grant to Neurolixis to advance F-15599 to clinical development.

PHA-543613 was discovered by Pfizer and has been under development primarily as a potential treatment of schizophrenia. PHA-543613 acts as an agonist to the Neuronal acetylcholine receptor protein alpha-7 subunit. A single human trial was conducted in healthy human volunteers, but the compound has been studied extensively in rat models for schizophrenia as well as Parkinson's disease and Alzheimer's disease.