Quantitative systems pharmacology model of GITR‐mediated T cell dynamics in tumor microenvironment

T cell interaction in the tumor microenvironment is a key component of immuno‐oncology therapy. Glucocorticoid‐induced tumor necrosis factor receptor (TNFR)‐related protein (GITR) is expressed on immune cells including regulatory T cells (Tregs) and effector T cells (Teffs). Preclinical data suggest that agonism of GITR in combination with Fc‐γ receptor‐mediated depletion of Tregs results in increased intratumoral Teff:Treg ratio and tumor shrinkage. A novel quantitative systems pharmacology (QSP) model was developed for the murine anti‐GITR agonist antibody, DTA‐1.mIgG2a, to describe the kinetics of intratumoral Tregs and Teffs in Colon26 and A20 syngeneic mouse tumor models. It adequately captured the time profiles of intratumoral Treg and Teff and serum DTA‐1.mIgG2a and soluble GITR concentrations in both mouse models, and described the response differences between the two models. The QSP model provides a quantitative understanding of the trade‐off between maximizing Treg depletion versus Teff agonism, and offers insights to optimize drug design and dose regimen.