rs-39604 and Pain

We report the synthesis of new compounds 4-35 based on two different openings (A and B) of the chromane ring present in the previously identified 5-HT1A receptor (5-HT1AR) ligand 3. The synthesized compounds were assessed for binding affinity, selectivity, and functional activity at the 5-HT1AR. Selected candidates resulting from B opening were also evaluated for their potential antinociceptive effect in vivo and pharmacokinetic properties in vitro. Analogue 19 [2-(4-{[2-(2-ethoxyphenoxy)ethyl]amino}butyl)tetrahydro-1H-pyrrolo[1,2-c]imidazole-1,3(2H)-dione] has been characterized as a high-affinity and potent 5-HT1AR agonist (Ki = 2.3 nM; EC50 = 19 nM). Pharmacokinetic studies indicated that compound 19 displays a good metabolic stability in human liver microsomes (t1/2 ∼ 3 h and CLint = 3.5 mL/min/kg, at 5 μM), and a low level of protein binding (25%, at 5 μM). Interestingly, 19 (3 mg/kg, ip, and 30 mg/kg, po) caused significant attenuation of formalin-induced behavior in early and late phases of the mouse intradermal formalin test of pain, and this in vivo effect was reversed by the selective 5-HT1AR antagonist WAY-100635. Thus, the new 5-HT1AR agonist identified in this work, 19, exhibits oral analgesic activity, and the results herein represent a step toward identifying new therapeutics for the control of pain.

Topics: Analgesics; Animals; Binding, Competitive; Cyclic AMP; Cytochrome P-450 CYP2D6; Cytochrome P-450 CYP2D6 Inhibitors; HeLa Cells; Heterocyclic Compounds, 2-Ring; Humans; Hydantoins; Kinetics; Ligands; Male; Mice; Models, Chemical; Molecular Structure; Pain; Pain Measurement; Piperazines; Pyridines; Radioligand Assay; Rats; Receptor, Serotonin, 5-HT1A; Serotonin 5-HT1 Receptor Agonists; Serotonin Antagonists