In an attempt to use scheduling to decouple therapeutic efficacy from toxicity, Rothschilds et al. treated tumor-bearing mice with a tumor-targeting antibody on day 0, IFNα on day 1, and an extended half-life version of IL2 (eIL2) on days 0, 1, 2, or 3. All regimens exhibited similar therapeutic efficacy, but only administration of eIL2 before IFNα resulted in significant weight loss, which could be attributed to eIL2-mediated increase in NK cell activation and sensitization to IFNα signaling as well as multiple systemic cytokine increases. NK cells played a critical role in weight loss, but not in efficacy.
In combination cancer immunotherapies, consideration should be given to designing treatment schedules that harmonize with the immune system’s natural timing. An efficacious temporally programmed combination therapy of extended half-life interleukin 2 (eIL2), tumor targeting antibody, and interferon (IFN) α was recently reported; however, tumor-ablative efficacy was associated with significant toxicity. In the current work, altering the order and timing of the three agents is shown to decouple toxicity from efficacy. Delaying the administration of eIL2 to be concurrent with or after IFNα eliminates toxicity without affecting efficacy in multiple syngeneic tumor models and mouse strains. The toxicity resulting from eIL2 administration before IFNα is dependent on multiple systemic inflammatory cytokines including IL6, IL10, IFNγ, and tumor necrosis factor α. Natural killer (NK) cells are the main cellular contributor to toxicity, but are not essential for tumor control in this system. When pre-conditioned with eIL2, splenic NK cells became hyper-activated and upregulate IFNα signaling proteins that cause an excessive, toxic response to subsequent IFNα exposure. This work illustrates an example where accounting for the temporal dynamics of the immune system in combination therapy treatment schedule can favorably decouple efficacy and toxicity.