TABLE 2

Summary of parameters for kinetic binding of various ligands to NK3

All of the values were obtained in 50 mM Tris-HCl, pH 7.4, at 22°C. Radiolabeled osanetant, SB222200, and [MePhe7]NKB were used in filter binding assays to quantify association and dissociation binding kinetics. The apparent first-order rate constant for association kon[A], kon, and koff were obtained by fitting data to eqs. 12 to 14. The koff value for talnetant was determined using a hot-chase procedure with 125I-[MePhe7]NKB as discussed under Materials and Methods. The Kd values were taken as the ratio of koff/kon.


Compound

kon[A]

kon

koff

Kd
min-1 min-1nM-1 min-1 nM
Osanetant 0.23 0.23 0.03 ± 0.01 0.15
SB222200 0.26 0.13 0.07 ± 0.01 0.56
[MePhe7]NKB 0.16 1.55 0.14 ± 0.02 0.09
Talnetant
N.D.
N.D.
>0.13 ± 0.04
N.D.
  • Not determined.