Evaluation of an IgG therapeutic efficacy in a humanized immune system mouse model lacking murine Fc gamma receptors

Abstract

Abstract Fc gamma receptors (FcγRs) on residual murine immune cells in humanized immune system (HIS) mice can interact with human IgG-based therapeutics and confound preclinical results. We assessed impact of murine FcγRs on anti-PD1 efficacy in HIS mice engrafted with lung adenocarcinoma cells treated with pembrolizumab or vehicle. We also present humanization results for the newly generated FcγR knockout NOG-EXL. Methods: HIS NOG (huNOG) or HIS FcγR knockout NOG mice (FcResolv™ huNOG) were made using identical protocols with CD34+ cells (3 shared donors). Reconstitution was evaluated in naïve animals and HCC827 cells were inoculated in remaining animals. From D7, mice were dosed twice weekly for 4 wks then euthanized for blood, spleen, and tumor analysis. Results: Humanization was equivalent between strains. Pembro treatment showed significant tumor growth inhibition in 1 donor in FcResolv huNOG, but not in donor-matched huNOG. Human TILs in pembro-treated mice were significantly different between the strains for all donors, with more CD8+ T cells and fewer TAMs in FcResolv huNOG compared to vehicle-treated mice, and no significant differences in huNOG. Murine TIL analysis showed differences in murine macrophage populations between strains. Conclusions: Anti-PD1-treated FcResolv huNOG mice show expected pharmacodynamic changes and donor-dependent efficacy, whereas pembro-treated huNOG mice showed neither, demonstrating the impact of murine FcγRs on antibody IgG-based therapeutics.