Samelisant (SUVN-G3031) is a potent and selective histamine H3 receptor (H3R) inverse agonist with good brain penetration and oral bioavailability. Samelisant has a similar binding affinity towards human (hH3R; Ki=8.7 nM) and rat (rH3R;Ki=9.8 nM) H3R indicating no inter-species differences. Samelisant can be used for the research of sleep-related disorders[1].

Samelisant displays inverse agonist activity and it exhibits very high selectivity towards H3R. The pEC50 value of histamine (8.5) for human H3 receptor increases to 8.2, 7.3 and 6.2 after treatment with 1, 10 and 100 nM of Samelisant, respectively. The pEC50 value of histamine (8.2) for rat H3 receptor increases to 7.9, 7.4 and 6.4 after treatment with 1, 10 and 100 nmol/L of Samelisant, respectively[1].Samelisant binds to the orthosteric site in a reversible manner with Kb values of 1.3 nM and 1.1 nM deduced from pA2 value for human and rat H3R, respectively[1].Samelisant also modulates dopamine and norepinephrine levels in the cerebral cortex while it has no effects on dopamine levels in the striatum or nucleus accumbens[1].

Treatment with Samelisant (10 and 30 mg/kg, p.o.) produces a significant increase in wakefulness with a concomitant decrease in non-rapid eye movement sleep (NREM) sleep in orexin knockout mice subjected to sleep electroencephalography (EEG)[1]. Samelisant also produces a significant decrease in direct rapid eye movement (REM) sleep onset (DREM) episodes, demonstrating its anticataplectic effects in an animal model relevant to narcolepsy[1].Samelisant treatment in mice produces a dose-dependent increase in tele-methylhistamine levels indicating the activation of histaminergic neurotransmission[1].

[1]. Ramakrishna Nirogi, et al. Samelisant (SUVN-G3031), a potent, selective and orally active histamine H3 receptor inverse agonist for the potential treatment of narcolepsy: pharmacological and neurochemical characterisation. Psychopharmacology (Berl). 2021 Jun;238(6):1495-1511.