Table 1.

Summary of the parameters used in system (1)

Parameter	Description	Units
Physiological parameters
$V_{\text{P}}$	Volume of the plasma compartment	L
$V_{\text{T}}$	Volume of the tissue (site of action) compartment	L
Drug pharmacokinetics
${\text{CL}}_{\text{P}},{\text{CL}}_{\text{T}}$	Rate of drug clearance from the plasma and tissue compartments	L/day
$k_{01}$	Rate of drug absorption	1/day
$k_{\text{TP}}$	Drug distribution rate from tissue to plasma	1/day
$k_{\text{PT}}$	Drug distribution rate from plasma to tissue	1/day
$k_{\text{eP}}$	Rate of drug elimination from plasma, $k_{\text{eP}}=\frac{{\text{CL}}_{\text{P}}}{V_{\text{P}}}$	1/day
Target properties
$K_{\text{D}}$	Equilibrium dissociation constant for drug–target binding	nM
$k_{\text{on}}$	Second-order rate constant of drug–target binding	nM/day
$k_{\text{off}}$	First-order rate constant for drug dissociation; $k_{\text{off}}=K_{\text{D}}{k}_{\text{on}}$	1/day
$S_0$	Homeostatic baseline target concentrations (determined experimentally or obtained from the literature)	nM
$k_{\text{int}}$ or $k_{\text{deg}}$	Rate of target internalization, degradation, or clearance (this can also be calculated from the half-life of the target as $k_{\text{deg}}=ln(2)/(\text{target half-life)}$)	1/day
$k_{\text{syn}}$	Target synthesis rate $(k_{\text{syn}}=S(0)\times k_{deg}),$ where $S(0)$ is the target-specific baseline target concentration	nM/day