Drug:Target Affinity

Drug:Target Affinity, typically notated \(K_{D,X}\) for target \(X\) in Assess models, quantifies the strength of the binding interaction between a drug and its target. Specifically, the parameter controls the monovalent binding interactions between drug and target.

Binding is modeled as a dynamic process. The on and off rates of binding are derived from the affinity. The on-rate is assumed typical for a protein-protein interaction, and the off-rate is calculated from the affinity. The affinity default units are nM. For detailed discussion of the reactions' implementations see Binding Reactions

Drug:Target Affinity in Assess

Drug:Target Affinity is typically measured in vitro via surface plasmon resonance (Biacore ™) or bio-layer interferometry (Octet ®) assays. For membrane-associated targets, on-cell binding assays often provide an effective affinity that is appropriate for use in the models. Reported affinity for biotherapeutics of a similar mechanism of action or against targets of a similar class may be a good starting point for simulations.

Typical Values

Drug	Report Affinity (nM)	Reference
Adalimumab	0.0086	Kaymakcalan et al. 2009
Belimummab	0.274	BLA #125370
Infliximab	0.0042	Kaymakcalan et al. 2009
Omalizumab	0.02	Chang et al. 2000; Kolbinger et al. 1993
Panitumumab	0.05	Yang et al. 2001;
Risankizumab	0.001	Singh et al. 2015
Trastuzumab	0.1	Li et al. 2013; Troise et al. 2008
Ustekinumab	0.001	Luo et al. 2010; Ma et al. 2009