ALBERT

Description: IL-1R3 is the co-receptor required for signaling of IL-1β, IL-1α, IL-33 and IL-36α, β and γ. The naturally occurring IL-1 receptor antagonist (anakinra), is used to block IL-1β, and IL-1α and clinical trials have demonstrated a reduction in progression to multiple myeloma as well as increased overall survival in stage IV pancreatic cancer using anakinra. In addition, a monoclonal antibody that targets IL-1α increases overall survival in metastatic colorectal cancer. However, blocking IL-1R3 would reduce not only IL-1β and IL-1α but also IL-33 as well as IL-36α, β and γ. The data described below reveal the broad efficacy of anti-IL-1R3. In the present studies, monoclonal humanized anti-IL-1R3 antibodies were studied in the mixed leukocyte reaction (MLR), in peripheral mononuclear cells (PBMC) stimulated with LPS, heat-killed Candida albicans or anti-CD3/antiCD28 as well as in THP-1 cells, a cell line derived from a patient with acute myeloid leukemia (AML). In the MLR, anti-IL-1R3 at 5 µg/mL reduced IFNγ by 81% and IL-6 by 48% compared to 36% by anakinra. In LPS-stimulated PBMCs, IL-6 was reduced by 40% and 58% with anakinra and anti-IL-1R3 respectively. Using heat-killed Candida, the suppression of IL-6 production by anti-IL-1R3 was up to 70%, comparable to anakinra. Immuno-stimulation using anti-CD3/CD28 resulted in a similar inhibition capacity for anakinra (42%) and anti-IL-1R3 (45%) on IL-6 production also. Since neutralizing anti-IL-1α antibodies have increased overall survival in metastatic colorectal cancer, we also measured the effect of anti-IL-1R3 on intracellular levels of IL-1α. In PBMCs stimulated with LPS, the levels of IL-1α were reduced by 35% in cells cultured with anakinra at 10 µg/mL and by 66% in cells exposed to anti-IL-1R3 at same concentration. Activating PBMCs with anti-CD3/anti-CD28 led to a reduction in IL-1α by anakinra of 17%, whereas anti-IL-1R3 suppressed by 29%. We next examined the effect on THP-1 cells as a model for blocking IL-1 family members in AML. THP-1 were differentiated with phorbol myristate acetate (PMA) for 3 hours, washed and subsequently rested for 3 days. The cells were then stimulated with LPS for 3 hours and anti-IL-1R3 was added for 1 hour followed by inflammasome activation with ATP. The reduction in secretion of IL-1β was here 30% at 5 µg/mL of anti-IL-1R3. Collectively, these studies indicate that antibody blockade of IL-1R3 is effective in reducing cytokines from primary cells using in-vitro models of organ rejection, infection and immunostimulation. In THP-1 cells, the reduction in inflammasome-dependent IL-1β suggests that anti-IL-1R3 can be used to treat acute myeloid leukemia, or progression to multiple myeloma. Since anti-IL-1R3 inhibits the signaling through IL-1R1, both IL-1α and IL-1β are targeted by this antibody. Suggesting a future role for this antibody in not only AML, but also other cancer types dominated by IL-1 mediated inflammation, such as metastatic colorectal and pancreatic cancer. Disclosures Fischer: MAB Discovery GmbH: Employment. Pollyea:Ariad: Other: advisory board; Pfizer: Other: advisory board, Research Funding; Glycomimetics: Other: DSMB member; Alexion: Other: advisory board; Celgene: Other: advisory board, Research Funding.