Table 4.

Binding affinity of aprepitant and compounds 5A–E for the rat neurokinin 1 receptor.

Compound	IC50 ± SEM a [µM]	Ratio to APT
Aprepitant	0.13 ± 0.06	1.0
APT-Et-DOTA, 5A	6.2 ± 2.6	48.2
APT-Pr-DOTA, 5B	0.69 ± 0.07	5.3
APT-Bu-DOTA, 5C	1.8 ± 0.7	14.3
APT-Ac-HN-NH-DOTA, 5D	2.5 ± 0.7	19.1
APT-Ac-Et-DOTA, 5E	2.5 ± 0.5	19.7

^a IC₅₀ ± SEM: the half-maximal inhibitory concentration with the standard error of the mean of three independent experiments done in duplicate.