Reversing/Blocking T cell suppression by extracellular vesicles as cancer therapy

ABSTRACTA major goal of cancer immunotherapy has been to re activate quiescent tumor associated T cells to enhance their detection and killing of cancer cells in tumor microenvironmentsIt is well established that with persistent activation of Tcellsin chronic inflammation and cancerimmune suppressive checkpoints exist that inhibit Tcell activation to limit collateral damage to host tissuesBuilding on this knowledge cancer therapies have been developed that block T cell checkpoints using monoclonal antibodiesCheckpoint blocking strategies that have targeted the inhibition of two T cell checkpointsPDand CTLAhave been curative for some cancersHowevera majority of patients either do not respond or the responses are not durableA likely reason for this is the presence of other immune regulatory systems that suppress T cell function in tumorsincluding T regulatory cells and myeloid derived suppressor cells that perhaps must also be eliminatedRecently there has been a growing awareness that nano sized extracellular vesicles present in tumors are able to arrest T cell functionWe have isolated micro vesicles called exosomesEXfrom human tumors that bind to and internalize into T cells resulting in a rapid and reversible blockade in the activation potential of these cellsThe immunosuppressive EX represents a new Tcell checkpoint that results in an arrest of the activation the T cell signaling cascadeThe suppression of T cells has been causally linked to phosphatidylserinePSexpressed on the surface of the EXSeveral non toxic water soluble organic molecules that bind PS have been synthesized by our collaborators at MTTIand have been screened and shown by us at IMT LLCto block reverse the immune suppressive activity of tumor associated EXOne of the PS binding moleculesZnT DPAsignificantly inhibits the T cell immune suppression of the tumor associated EX in vitroIn Aimthe pharmacokineticsPKthe bio availability and toxicity of Zn T DPAwill be addressed in globally immune deficient NSG naive miceand in these mice bearing human ovarian tumor xenograftsIn Aimwe will determine the pharmacodynamicsPDof this molecule in vivoWe predictand will test herethat treatment in vivo with Zn T DPAat a dose determined in Aimof NSG mice bearing human ovarian tumor xenografts will block or reverse the T cell suppression by the tumor associated exosomesre activate patientstumorassociated T cellsand enhance tumor killing in the tumor microenvironmentWith our novel xenograft modelthat includes tumor stromathe tumor associated T cellsand exosomeswe are able to quantify several matrices including changes in tumor cell numberserum levels of human cytokinesand in the number and activation potential of the tumorassociated T cellsOur in vivo studies in Phaseof this application are expected to provide a rationale and underpinning for a Phase II application to study the PKPD and efficacy of the Zn T DPA in combination with currently used checkpoint inhibition therapiesand provide for a scale up development of the Zn T DPA for a Phase I clinical trial NARRATIVE PUBLIC HEALTH RELEVANCESmall vesicles have been identified in human ovarian tumors that inhibit the anti tumor responses of patientswhite blood cellscalled T cellsA drug has been discovered that selectively blocks the immune suppressive vesiclesWe predict that by blocking the vesicleseffect in the tumors we will be able to reactivate quiescent T cellsand thereby enhance their tumor killing activity and prevent tumor spreadingThis is to be tested in this grant using novel techniques that have made it possible to study human tumors and tumor associated T cells that are established as grafts in immune deficient mice