Mobilization of CD8+ Central Memory T-Cells with Enhanced Reconstitution Potential in Mice By a Combination of G-CSF and GMI-1271-Mediated E-Selectin Blockade

T-cells are critical mediators of immune defense against pathogens and cancer. Adoptive T cell immunotherapy and T-cell engineering have promising clinical applications but T cell survival and exhaustion are current limitations. Central memory cells (TCM CD62L+ CCR7+) and their precursors, stem central memory T-cells (TSCM) possess the stem-like properties needed to reconstitute and prolong an effective immune response long-term. These cells have been shown to significantly improve therapeutic efficacy of adoptive T-cell therapy. The challenge remains to harvest good quality TCM-cells for these immunotherapy approaches. The bone marrow (BM) is the major reservoir of CD8+ TCM and their precursors. We have previously shown that E-selectin is expressed in the BM vasculature and drives activation and differentiation of hematopoietic stem cells during G-CSF induced mobilization to the blood. We find therapeutic blockade of E-selectin promotes HSC self-renewal and reconstitution in vivo. We now examine the impact of E-selectin blockade on CD8+ T cell mobilization from the bone marrow to the blood and hypothesize that E-selectin blockade may also dampen the activation/differentiation of this subset. First we administered a standard G-CSF regime (filgastim 250ug/kg/day for 3 days) to mice and then dosed some cohorts with GMI-1271 (40mg/kg BID) from 12 to 72 hours within this 3 day period. Administration of G-CSF alone results in a near complete disappearance of bone marrow resident CD8+ TCM cells, and their apparent migration (increase in numbers) to the blood, while CD8+ subsets in the lymph nodes and spleen were barely affected by G-CSF. Furthermore among T-cell subsets, CD8+ but not CD4+ TCM were specifically mobilized into the blood when GMI-1271 was co-administered for the last 12 to 24 hours of G-CSF. These findings are consistent with reports demonstrating the bone marrow to be a major reservoir for CD8+ but not CD4+ central memory T-cells. Administration of GMI-1271 caused a marked enhancement in mobilization into the blood of CD8+ TCM/SCM (CD62Lhi, CCR7+) cells over treatment with G-CSF alone (p In a previous report we have shown that therapeutic blockade of E-selectin promotes HSC self-renewal in vivo. Thus, it is possible that E-selectin blockade boosts mobilization of CD8+ TCM/SCM with stem-like properties into the blood by loosening factors retaining CD8+ TCM/SCM in the bone marrow and/or blocking the E-selectin-mediated activation and differentiation of this T-cell subset. In summary, our studies identify E-selectin blockade as a novel target to improve harvesting of CD8+ TCM/SCM cells with stem-like properties. Blockade of this target with GMI-1271 significantly improves the in vivo reconstitution potential and regenerative properties of CD8+ T-cells from donor blood allowing a valuable source of desired T-cells for use in adoptive immunotherapy and T-cell engineering. Disclosures Winkler: GlycoMimetics Inc: Research Funding. Barbier:GlycoMimetics Inc: Research Funding. Davies:GlycoMimetics Inc: Research Funding. Smith:GlycoMimetics, Inc.: Employment. Fogler:GlycoMimetics, Inc.: Employment. Magnani:GlycoMimetics Inc: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees.