Sequential tumor and dual immune targeted immunotherapy: anti-lymphoma activity of Rituximab with 4-1bb stimulation and PD-1 blockade

Abstract

To select maximally-efficacious, minimally-toxic regimens of combination tumor-and immune-targeted therapy, pre-clinical testing in immune-competent models is required. We previously demonstrated 4-1bb(CD137) stimulation augmented the innate immune response mediated by CD137 + activated natural killers (NK) cells and the subse-quent CD8 + T cell adaptive immune response when admi-nistered after tumor-targeting, ADCC-competent, mAbs targeting CD20, HER2, and EGFR. As four ongoing clini-cal trials (NCT01471210, NCT01775631, NCT02110082, NCT01307267) investigate this strategy, the CD8 + T cell response stimulated by 4-1bb was determined pre-clini-cally to be further augmented by PD-1/PD-L1 blockade, and a clinical trial is planned (NCT02179918). Taken together, we hypothesized, sequential tumor-targeting with anti-CD20 mAb, Rituximab, followed by dual immune-targeting with anti-CD137 agonism and PD-1/ PD-L1 blockade would be efficacious and tolerable due to non-overlapping immune mechanisms and toxicity profiles. Preclinical modeling was performed in a therapeutic, syngenic, A20 lymphoma BALB/c model combining anti-CD20 mAb (IgG2a-18B12, delivered intraperitoneally, i.p. on d5) with agonistic anti-CD137 mAb (IgG2a-2A, i.p. d6) and anti-PD-1 mAb (IgG2a-RMPI-14, i.p. d6) with intratu-moral (i.t.) and circulating (c.) immune responses pheno-typed by flow cytometry and time of flight mass cytometry (CyTOF). Combination immunotherapy with anti-CD137 and anti-PD1 was superior to either monotherapy without anti-CD20 treatment in a dose-dependent manner (p < .001 survival), though no mice were cured long-term. When administered following anti-CD20 treatment, combination immunotherapy with anti-CD137 and anti-PD1 was superior to either monotherapy in a sequence-dependent manner (p