Encenicline hydrochloride (EVP-6124 hydrochloride) is a new-type partial agonist of α7 neuronal nicotinic acetylcholine receptors (nAChRs).

EVP-6124 hydrochloride displaces [3H]-MLA (Methyllycaconitine) (Ki=9.98 nM, pIC50=7.65±0.06, n=3) and [125I]-α-bungarotoxin (Ki=4.33 nM, pIC50=8.07±0.04, n=3). EVP-6124 is approximately 300 fold more potent than the natural agonist ACh (Ki=3 μM), measured in binding assays using [3H]-MLA. EVP-6124 inhibits the 5-HT3 receptor by 51% at 10 nM, the lowest concentration tested. Evaluation of the human 5-HT2B receptor expressed in CHO cells demonstrates displacement of [3H]-mesulergine (Ki=14 nM) and only antagonist activity in the rat gastric fundus assay at an IC50 of 16 μM. In binding and functional experiments, EVP-6124 shows selectivity for α7 nAChRs and does not activate or inhibit heteromeric α4β2 nAChRs[1].

EVP-6124 hydrochloride has good brain penetration and an adequate exposure time. EVP-6124 (0.3 mg/kg, p.o.) significantly restores memory function in scopolamine-treated rats (0.1 mg/kg, i.p.) in an object recognition task (ORT). Although donepezil at 0.1 mg/kg, p.o. or EVP-6124 at 0.03 mg/kg, p.o. did not improve memory in this task, co-administration of these sub-efficacious doses fully restored memory. In a natural forgetting test, an ORT with a 24 h retention time, EVP-6124 improved memory at 0.3 mg/kg, p.o. This improvement is blocked by the selective α7 nAChR antagonist methyllycaconitine (0.3 mg/kg, i.p. or 10 μg, i.c.v.). EVP-6124 is found to bind moderately to rat plasma proteins with a mean fu of 0.11±0.01 (mean±SD) or 11%. Over a range of 0.1-30 mg/kg, p.o., EVP-6124 demonstrates proportional dose escalation. Tmax is at 4 h in plasma and 2 h brain, although the brain concentrations remained similar between 2 and 8 h. The B:P ratios are 1.7-5.1 between 1 and 8 h[1]. Pharmacokinetic studies have shown that EVP-6124 (0.4 mg/kg, i.p.) reaches peak brain concentration 2 hr after administration and remains at effective concentrations for at least 4 hr. EVP-6124 is administered to WT mice at ZT0 (0.4 mg/kg i.p single dose) and significantly increases the saturation index of NMDARs in slices obtained 4 hr later without causing prolonged wakefulness or enhanced locomotor activity [2].

Binding or activity of EVP-6124 is measured at 10 μM in a selectivity panel according to standard validated protocols under conditions defined by the contractor. For the 5-HT2A receptor binding assay, membranes are prepared from HEK293 cellsexpressing the human recombinant 5-HT2A receptor. For 5-HT2B and 5-HT2C receptor binding assays, membranes are prepared from CHO cells expressing the human recombinant 5-HT2B or 5-HT2C receptor. Affinity is determined by incubating different concentrations of EVP-6124 in binding buffer for 1 h. For 5-HT2A binding, the incubation is at 22°C in the presence of 0.5 nM [3H]-ketanserin; for 5-HT2B, at 22°C in the presence of 2 nM [3H]-mesulergine; and for 5-HT2C, at 37°C in the presence of 1 nM [3H]-mesulergine. Nonspecific binding is determined in the presence of 1 μM ketanserin, 10 μM mesulergine, or 10 μM RS-102221 for 5-HT2A, 5-HT2B, or 5-HT2C, respectively. All measurements are performed in triplicate. EVP-6124 is also tested in the 5-HT2B rat gastric fundus tissue response assay. Briefly, inhibition of α-methyl serotonin-induced contraction is isometrically measured. All measurements are performed in duplicate[1].