PROJECT SUMMARY/ABSTRACT - In response to PAR-16-384, the goal of this NIDA/NIH Chemical
Discovery (CHEM) Award (R21/R33) proposal is to discover antidotes for treating “Acute Marijuana
Intoxication” produced by ¿9-tetrahydrocannabinol (THC) and the next generation synthetic psychoactive
cannabinoids (SPCs) such as JWH-018. The cannabis constituent THC exerts its psychotropic effects
(marijuana “high”) mainly via CB1R activation. SPCs mimic the effects of THC with higher potency and are
illegally sold as “designer drugs”. Although acute toxicity is benign in the average adult, patients who consume
high doses of THC (herbal and synthetic) present themselves with recurrent episodes of nausea and vomiting
(Hyperemesis Syndrome), injected conjunctiva, and experience impaired cognition, motor skills and psychotic
symptoms in the ER. In comparison, the neurotoxicity associated with SPCs is more severe wherein patients
are admitted into the ER for altered mental status, somnolence, cardiotoxicity, stroke, kidney damage and
acute psychosis. There are no antidotes available for treating acute cannabinoid poisoning, highlighting the
need to address this critical public-health issue. The goal of this project is to discover antidotes to counteract
the intoxicating effects of excessive CB1R activation and be therapeutically useful in an emergency setting.
In this regard, the R21 phase will focus on use of in silico analysis, synthesis and characterization of
compounds with favorable drug-like safety profiles. The synthesized ligands will be tested for their affinity and
selectivity for CB1R and for their functional in vitro efficacy using the cAMP assay. Subsequently, ligands will
be evaluated for their stability in plasma, whole blood and towards liver microsomes. Accordingly, their
biochemical half-lives and interspecies variations will be determined. The R33 phase will focus on lead
optimization, scale-up and re-synthesis along with in vivo evaluation of compounds in mice (both genders).
Ligands will be first studied using a physiologically effective dose i.v. to quantify relative brain penetration using
LC/MS/MS. Compounds exhibiting good brain penetration, when administered i.v., will be screened for their
ability to rapidly normalize an on-going hypothermic effect induced by an acute dose of an agonist. Ligands
with minimal intrinsic activity will be assayed i.v. using the functional observation battery (FOB) for their ability
to normalize the neurological effects produced by “suprapharmacological” doses of the CB1 agonist. Given
that the patients’ drug histories may not be known at admission, a key desired characteristic of short-acting
antagonists as compared to the CB1 inverse-agonist, rimonabant (SR), is that they not elicit a physical
withdrawal syndrome in cannabis-dependent subjects. To test this hypothesis, lead compounds will be
administered to mice treated repeatedly with THC or JWH-018, to investigate whether they precipitate
withdrawal. Results will be compared to rimonabant. Data will be used in an iterative manner to establish proof-
of-concept and ultimately identify compounds for treating acute cannabinoid intoxication.