In-vivo reprogramming macrophages and dendritic cells with Allocetra-OTS: Successful mono- and combination-antitumor therapy.

Abstract

2532 Background: Chimeric antigen receptor (CAR) T cells can activate an immune response to a cancer-specific antigen but is less effective in solid tumors. Immune check point inhibitors (ICI) revolutionized the treatment of solid tumors, however, in many tumors only partial response is achieved. Here we questioned the role of synergistic effect of Allocetra-OTS (cellular therapy for in-vivo reprogramming macrophages and dendritic cells, Enlivex Therap.) on solid tumor progression. Methods: To follow tumor growth in vivo, HeLa-CD19 cells were stably transduced with pLenti-PGK-V5-Luc-Neo. For CAR preparation, fresh mononuclear cells (MNC) were transfected with CD19-CAR plasmids. For the intraperitoneal solid tumor model, SCID-Bg mice were injected intraperitoneally (IP) with human HeLa-CD19 or HeLa-CD19-luciferase cells, 10×106 allocetra-OTS or vehicle, and 10×106 CD19-CAR T cells or mock T cells. In an immune-competent model, Balb/c mice were treated IP with AB12 (mesothelioma) with pLenti-PGK-V5-Luc-Neo and treated with anti-CTLA4 with or without Allocetra-OTS. Mice were monitored daily for clinical signs and peritoneal fluid accumulation and weekly for tumor growth. Kaplan-Meier log rank test was done for survival. Peritoneal cells were evaluated using single cell analysis and flow cytometry. Tumors were examined for bacterial presence by immunohistochemistry staining with antilipoteichoic acid (LTA) and antilipopolysaccharide (LPS). For allocetra-OTS preparation, enriched mononuclear fractions were collected by leukapheresis from healthy eligible human donors and induced to undergo early apoptosis. Results: SCID mice survived 30±5 days (range 27–37) and were sacrificed or died from solid tumor in the peritoneal cavity after accumulation of bloody peritoneal fluid and clinical deterioration. Results were verified using IVIS of intraperitoneal HeLaCD19-Luc cells. CAR T cell therapy significantly ameliorated survival to 55±11 days (p < 0.05 vs MOCK) but Alloctra-OTS further ameliorated survival to 75±10 (p < 0.001) with 20-40% complete remission. In AB12 model, anti CTLA4 therapy significantly ameliorated survival from 26±5 to 38 ±9 days (p < 0.05). However, Allocetra-OTS monotherapy ameliorated survival to 45 ±12 days (p < 0.02) and combinational therapy to 75±9 days (p < 0.0001) with complete remission in 60-75% of mice. Single cell analysis revealed that restoration of large peritoneal macrophages (LPM), were associated with antitumor activity. Conclusions: During intraperitoneal tumor progression, allocetra-OTS as monotherapy or combinational therapy with CAR or anti-CTLA4 significantly reduced tumor size and enable complete remission in up to 75% treated mice. Based on excellent safety profile in > 30 patients treated for sepsis and Covid19, human phase I/II of allocetra-OTS plus ICI, for peritoneal metastases, is planned for 2022.