avelumab

Avelumab is a fully human IgG1 anti-PD-L1 monoclonal antibody with potential antibody-dependent cell-mediated cytotoxicity property. Avelumab increases NK-cell lysis 3.1-fold (P=0.01) in JHC7 cells relative to isotype control. When the cells are treated with IFN-gamma, Avelumab markedly enhances NK-cell lysis relative to isotype control in the following cell lines: JHC7 (7.56-fold; P=0.001), UM-Chor1 (7.34-fold; P< 0.001), U-CH2 (2.6 fold; P=0.008), MUG-Chor1 (8.38-fold; P=0.0016). Avelumab effectively increases antibody-dependent cell-mediated cytotoxicity (ADCC) of both the non-cancer stem cell (CSC) and CSC subpopulations to the same degree[1]. Results also demonstrate that the addition of Avelumab increases the frequency of antigen-specific multifunctional CD8+ T cells by more than fivefold, relative to the isotype control in CEFT-stimulated peripheral blood mononuclear cells (PBMCs).

Cell Assay: To examine the relationship between a cancer stem cell (CSC) subpopulation and antibody-dependent cell-mediated cytotoxicity (ADCC) activity, UM-Chor1 cells are left untreated or treated with 50 ng/mL of IFN-gamma for 24 h. Cells are then plated as targets at 50, 000 cells/well in 6-well round-bottom culture plates and incubated with 2 ug/mL of Avelumab at room temperature for 30 min. NK cells are added at 2500, 000 cells/well at an effector-to-target (E:T) ratio of 50:1. After 4 h, tumor cells are harvested and stained with antibodies for flow cytometry.

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Animal Studies: Female C57BL/6 mice are used in this study. Subcutaneous tumor injections are carried out by inoculating C57BL/6 mice with 1x105 MB49 parental cells on the right shaved flank. Tumor growth is measured with calipers and 8 days post-inoculation mice are assigned to treatment groups. Tumor-bearing mice are treated with Avelumab (400 ug per 100 uL) and injected i.p. three times, 3 days apart. Since Avelumab is a human IgG1, three injections have to be compressed within a 7 to 9 day window (i.e., days 9, 12, and 15 post-tumor inoculation) to avoid the onset of neutralizing mouse anti-human Ig.