Figure 1. Schematic representation of biological mechanisms included in the mathematical model.
These processes are described by four partial differential equations, which are solved to obtain Equation (1). Briefly, the checkpoint inhibitor enters the tumor via diffusion (Da) leading to time-dependent drug concentration (σ), which then binds to the conjugate receptor on immune cells at rate λ. Immune cells (ψk) are drawn into the tumor microenvironment via cytokine-mediated chemotaxis (χ), resulting in immune checkpoint inhibitor-mediated cancer cell kill at rate λp. The full mathematical model derivation and its underlying assumptions are provided in a recent modeling and analysis report (Butner et al., 2020).