Metabolism and Distribution of Clozapine-N-oxide: Implications for Nonhuman Primate Chemogenetics.
The use of Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) in neuroscience has rapidly expanded in rodent studies but has lagged behind in nonhuman primate (NHP) experiments, slowing the development of this method for therapeutic use in humans. One reason for the slow adoption of DREADD technology in primates is that the pharmacokinetic properties and bioavailability of clozapine-n-oxide (CNO), the most commonly used ligand for human muscarinic (hM) DREADDs, are not fully described in primates. We report an extensive pharmacokinetic study using subcutaneous (SC) administration of CNO in five adult rhesus monkeys. CNO reached maximal plasma and cerebrospinal fluid (CSF) concentrations within 2 h after injection, with an observed dose-dependent increase in levels following a 3 and 10 mg/kg SC dose. Since CSF concentrations were below values predicted from unbound plasma concentrations, we investigated whether CNO was restricted from the CNS through active transport at the blood-brain barrier. In vitro assessment demonstrated that CNO is a substrate for P-glycoprotein (Pgp; efflux ratio, 20), thus providing a likely mechanism limiting CNO levels in the CNS. Furthermore, CNO is metabolized to the psychoactive compounds clozapine and n-desmethylclozapine in monkeys. The concentrations of clozapine detected in the CSF are sufficient to activate several types of receptor (including the hM-DREADDs). Our results suggest that CNO metabolism and distribution may interfere with reproducibility and interpretation of DREADD-related experiments in NHPs and calls for a re-evaluation of the use of CNO in DREADD-related experiments in NHPs along with the need to test alternative compounds.
Yerkes National Primate Research Center , Atlanta, Georgia 30329, United States.
Jessica
0000-0002-0964-9944
J
Raper
Sano Informed Prescribing, Inc. Franklin, Tennessee 37067, United States.
Ryan D
RD
Morrison
Sano Informed Prescribing, Inc. Franklin, Tennessee 37067, United States.
J Scott
JS
Daniels
Yerkes National Primate Research Center , Atlanta, Georgia 30329, United States.|Department of Psychiatry and Behavioral Sciences, School of Medicine, Emory University , Atlanta, Georgia 30322, United States.
Leonard
L
Howell
Yerkes National Primate Research Center , Atlanta, Georgia 30329, United States.|Department of Psychology, Emory University , Atlanta, Georgia 30322, United States.
Jocelyne
J
Bachevalier
Yerkes National Primate Research Center , Atlanta, Georgia 30329, United States.|Department of Neurology, School of Medicine, Emory University , Atlanta, Georgia 30322, United States.|Udall Center of Excellence for Parkinson's Disease Research, Emory University , Atlanta, Georgia 30329, United States.
Thomas
T
Wichmann
Yerkes National Primate Research Center , Atlanta, Georgia 30329, United States.|Department of Neurology, School of Medicine, Emory University , Atlanta, Georgia 30322, United States.|Udall Center of Excellence for Parkinson's Disease Research, Emory University , Atlanta, Georgia 30329, United States.
Adriana
0000-0001-9939-0130
A
Galvan
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D000818:Animals; D014150:Antipsychotic Agents / Q000097:blood / Q000134:cerebrospinal fluid / Q000493:pharmacokinetics*; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000378:metabolism; D002199:Capillary Permeability / Q000187:drug effects; D003024:Clozapine / Q000031:analogs & derivatives* / Q000097:blood / Q000134:cerebrospinal fluid / Q000493:pharmacokinetics; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D005260:Female; D006801:Humans; D008253:Macaca mulatta; D061985:Madin Darby Canine Kidney Cells; D008297:Male; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D014162:Transfection
C116614:ABCG2 protein, human; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D014150:Antipsychotic Agents; D009363:Neoplasm Proteins; D003024:Clozapine; C079149:clozapine N-oxide
DREADDs; Rhesus macaque; blood−brain barrier; clozapine; pharmacokinetics