In vitro activity: In CHO-OX1 cells, SB-334867 inhibits the orexin-A (10 nM) and orexin-B (100 nM)-induced calcium responses with pKB of 7.27 and 7.23 respectively, without effect on the UTP (3 microM)-induced calcium response.

Kinase Assay: SB-334867 free base is a selective non-peptide orexin OX1 receptor antagonist with a pKb value of 7.2. IC50 value: 7.2 (pKb). SB-334867-A inhibited the orexin-A (10 nM) and orexin-B (100 nM)-induced calcium responses (pK(B)=7.27+/-0.04 and 7.23+/-0.03 respectively, n=8), but had no effect on the UTP (3 microM)-induced calcium response in CHO-OX(1) cells. SB-334867-A (10 microM) also inhibited OX(2) mediated calcium responses (32.7+/-1.9% versus orexin-A).

Cell Assay: 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 can 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 is more selective for OX1 receptor over OX2 receptor. It causes 32.7% and 22% inhibition of orexin-A and orexin-B induced calcium responses in CHO-OX2 cells, respectively.