Anti-tumor activity of a novelLAIR1antagonist in combination with anti-PD-1to treat collagen-rich solid tumors (human)

We recently reported that resistance to PD-1-blockade in a refractory lung cancer-derived model involved increased collagen deposition and the collagen-binding inhibitory receptor leukocyte-associated immunoglobulin-like receptor 1 (LAIR1), and thus we hypothesized that LAIR1 and collagen cooperated to suppress therapeutic response. Here, we report LAIR1 is associated with tumor stroma and is highly expressed by intratumoral myeloid cells in both human tumors and mouse models of cancer. Stroma-associated myeloid cells exhibit a suppressive phenotype and correlate with LAIR1 expression in human cancer. NGM438, a novel humanized LAIR1 antagonist monoclonal antibody, elicits myeloid inflammation and allogeneic T cell responses by binding to LAIR1 and blocking collagen engagement. Further, a mouse-reactive NGM438 surrogate antibody sensitized refractory KP mouse lung tumors to anti-PD-1 therapy and resulted in increased intratumoral CD8+ T cell content and inflammatory gene expression. These data place LAIR1 at the intersection of stroma and suppressive myeloid cells and support the notion that blockade of the LAIR1/collagen axis can potentially address resistance to checkpoint inhibitor therapy in the clinic. Overall design: Dendritic cells were derived from monocytes, which were purified from PBMCs using a human pan monocyte isolation kit (Miltenyi). DCs were generated by culturing monocytes in X-VIVO 15 media (Lonza) containing 50 ng/mL recombinant human GM-CSF (Peprotech) and 50 ng/mL recombinant human IL-4 (Peprotech) for 5-6 days. 96-well tissue culture plates (Corning) were coated with 5 µg/mL human collagen type 1 (Millipore Sigma) in PBS overnight at 4° C, then washed in PBS. 1 x 105 DCs were added to the plates with anti-LAIR1 or an isotype control antibody at the listed concentrations then incubated for 2 days at 37° C. Conditioned media was collected the next day and analyzed using Luminex (ProcartaPlex, ThermoFisher).