PD-L1 (Programmed cell death ligand-1), also known as B7-H1 and CD274, is mainly expressed in antigen-presenting cells (APCs) and activated T cells, and is one of the two ligands of PD-1. The interaction between PD1 and PD-L1 plays an important role in the negative regulation of the immune response. PD-L1 is highly expressed in a variety of solid tumors. PD-1 and PD-L1 interactions can reduce T Cell Activation and promote tumor immune escape. The PD-1/PD-L1 signaling pathway can be blocked and antitumor immune response can be restored by using by anti-PD-1 or anti-PD-L1 antibodies to block the binding of PD1 to PD-L1.
OX40, also known as Tnfrsf4 (Tumor necrosis factor receptor super family, member 4), is mainly expressed on the surface of activated CD4+ and CD8+ T cells, and its binding with the OX40 ligand can stimulate CD8+ T Cell Activation. The coactivation of OX40/OX40L enhances T cell function, including cytokine production, proliferation and T cell survival. An OX40 agonist can reduce Regulatory T cells (Tregs) and improve anti-tumor activity.
Gene targeting strategy for B-hPD-L1/hOX40 mice. The exon 3 of mouse Pd-l1 gene that encodes the extracellular domain was replaced by human PD-L1 exon 3 and the exons 1-5 of mouse Tnfrsf4 gene that encode the extracellular domain were replaced by human TNFRSF4 exons 1-5 in B-hPD-L1/hOX40 mice.
Protein Expression Analysis
Strain specific OX40 and PD-L1 expression analysis in homozygous B-hPD-L1/hOX40 mice by flow cytometry. Splenocytes were collected from WT and homozygous B-hPD-L1/hOX40 (H/H) mice stimulated with anti-CD3ε in vivo (7.5 μg/mice), and analyzed by flow cytometry with species-specific anti-OX40 antibody. Mouse OX40 and PD-L1 were exclusively detected in WT mice. Human OX40 and PD-L1 were exclusively detected in homozygous B-hPD-L1/hOX40 but not WT mice.
Combination therapy of PD-L1 Ab and OX40 Ab
Antitumor activity of anti-hOX40 antibody combined with anti-hPD-L1 antibody in B-hPD-L1/hOX40 mice. (A) Anti-hOX40 antibody combined with anti-hPD-L1 antibodies inhibited MC38-hPD-L1 tumor growth in B-hPD-L1/hOX40 mice. Murine colon cancer MC38-hPD-L1 cells (5×105) were subcutaneously implanted into homozygous B-hPD-L1/hOX40 mice (female, 6-7 week-old, n=6). Mice were grouped when tumor volume reached approximately 150±50 mm3, at which time they were treated with anti-hOX40 antibody combined with anti-hPD-L1 antibody with doses and schedules indicated in panel (B) Body weight changes during treatment. As shown in panel A, combination of anti-hOX40 and anti-hPD-L1 antibody shows more inhibitory effects than individual groups, demonstrating that the B-hPD-L1/hOX40 mice provide a powerful preclinical model for in vivo evaluating combination therapy efficacy of hOX40 antibodies and hPD-L1 antibodies. Values are expressed as mean ± SEM.