SB-334867 free base is a selective antagonist of orexin-1 receptor [1].

Orexin-A and orexin-B are two peptides isolated from rat hypothalamus. They are involved in some physiological functions such as the control of feeding, energy metabolism and regulation of the sleep-wake cycle.

SB-334867 free base could inhibit the orexin-A and orexin-B induced calcium responses in CHO-OX1 cells with pKB values of 7.27 and 7.23, respectively. SB-334867 was more selective for OX1 receptor over OX2 receptor. It caused 32.7% and 22% inhibition of orexin-A and orexin-B induced calcium responses in CHO-OX2 cells, respectively. Moreover, SB-334867 was found to reduce both orexin-A-induced and fasting-induced food intake. The acute anorectic effect of it was associated with significant reductions in all active behaviours [1, 2].

References:
[1] Smart D, Sabido-David C, Brough S J, et al.? SB-334867-A: the first selective orexin-1 receptor antagonist. British journal of pharmacology, 2001, 132(6): 1179-1182.
[2] Rodgers R J, Halford J C G, Nunes de Souza R L, et al.? SB-334867, a selective orexin-1 receptor antagonist, enhances behavioural satiety and blocks the hyperphagic effect of orexin-A in rats. European Journal of Neuroscience, 2001, 13(7): 1444-1452.