Figure 2. Schematic of alternative approaches to directly inject cytokines into tumors.

Administration of soluble or depot-contained cytokine produces a kinetic competition between target cell uptake (T cells in this representation), and leakage out of the tumor. Skewing that competition towards intratumoral target-mediated consumption and away from leakage is a moving target, as both the number of target cells and depot release rate may vary patient-to-patient, by tumor microenvironment composition, and over time. Administering cytokine in a sterically accessible but anchored format obviates this issue.