PROJECT SUMMARY
The serotonin (5-HT) neurotransmitter system comprises at least 14 distinct receptors that share topologically
similar orthosteric sites, a fact that contributes to the historically difficult goal of sub-type selective modulation.
Allosteric modulation of G protein-coupled receptors (GPCRs) can yield drug candidates for previously elusive
receptors through targeting a structurally divergent allosteric site. Evidence suggests that dysregulated signaling
of the 5-HT2C receptor underlies pathological processes implicated in numerous mental health disorders,
including cocaine use disorder, which is without an FDA-approved medication. Interestingly, reduced 5-HT2C
receptor signaling plays a modulatory role in stimulating relapse-related phenotypes in preclinical models of
cocaine addiction, and conversely, rescuing this dysfunction may provide clinical utility to promote and maintain
abstinence. We hypothesize that the rational design of novel 5-HT2C receptor positive allosteric modulators
(PAMs) and optimization of 5-HT2C receptor PAM lead compounds will serve as a useful strategy to rescue
pathologically decreased 5-HT2C receptor signaling and, ultimately, suppress relapse-related behavioral
phenotypes. To this end, 4-alkylpiperidine-2-carboxamides were designed and synthesized in a PAM hit-to-lead
discovery effort. The work resulted in the discovery of two novel lead compounds, which displayed subtype-
selective functional enhancement of the 5-HT2C receptor, and lacked intrinsic agonism, in vitro. Leads, CTW0415
and CYD-6-2-1, exhibited favorable in vitro and in vivo pharmacokinetics, while a broad-panel GPCR screen
confirmed selectivity. In addition, these leads maintain adequate lead-like physicochemical characteristics and
represent ideal molecules upon which to build our lead optimization efforts. Our iterative strategy for 5-HT2C
receptor PAM lead optimization will enable robust structure activity relationship (SAR) and will be accomplished
by 1) rational design and synthesis of novel 5-HT2C receptor selective PAMs; and 2) biological characterization
in a cell-based 5-HT2C receptor functional assay and pharmacological characterization in a radioligand binding
assay. The proposed work will advance our knowledge of 5-HT2C receptor positive allosteric modulation and
provide insight towards PAM mechanism. Additionally, the current PAM lead compounds require activity
enhancements via optimization to enable development of preclinical candidates. The completion of this proposal
will foster technical expertise and scientific intuition, ultimately enabling the applicant to achieve the goal of
becoming an academic chemical biologist studying drug use disorders and the neuropharmacology of drugs of
abuse. The applicant will gain experience in medicinal, organic and computational chemistry; neuroscience;
molecular and cellular pharmacology; GPCR targeting experimental design; and the fundamentals of drug
discovery in allosteric modulation, neurobiology and the psychostimulant addiction fields. Taken together, the
present studies represent a high impact approach towards the discovery of neurotherapeutics for cocaine use
disorder, and will generate novel tools to elucidate 5-HT2C receptor function and potential therapeutic candidates.