TriLeukeVax: A CD80/IL-15/IL-15Rα Expressing Autologous AML Cell Vaccine Elicits Robust Anti-Leukemic Cytolytic Activity

Abstract

Acute myeloid leukemia (AML) is the most common acute leukemia in adults and is associated with poor outcomes due to frequent relapse after remission induction. While hematopoietic stem cell transplantation (HSCT) can improve survival, many individuals, especially older patients, are ineligible. Prior immunotherapies have not reliably induced effective anti-leukemic immunity and have been associated with severe and unpredictable toxicities. Thus, there is a need for safe and effective therapies that reduce relapse and increase overall survival (OS). We have developed a universally applicable, patient-specific, lentivirally engineered autologous AML cell vaccine, TriLeukeVax (TLV), designed to stimulate leukemia-specific cytolytic immune responses in AML patients in remission. To generate TLV, AML cells are engineered to express the highly synergistic combination of the co-stimulatory protein CD80 and the IL-15/IL-15-receptor alpha (IL-15R) heterodimer. Prior proof-of-concept (POC) studies demonstrated eradication of disease in >80% of leukemic mice with serial administration of TLV. In the current studies, TLV was generated from 59/60 cryopreserved, diagnostic bone marrow-derived patient AML samples. Ex vivo priming of post-remission patient T-cells by ex vivo co-culture with autologous TLV stimulated robust proliferative and cytotoxic responses. In secondary co-cultures, T-cells previously primed by initial co-culture with TLV, showed greater clonal expansion and leukemia-specific cytolytic activity towards de novo autologous AML blasts than did control, unprimed T-cells. The enhanced anti-leukemic activity of TLV-primed T-cells against de novo AML confirms the potential for vaccine administration to effectively target minimal residual disease (MRD) persisting after chemotherapy and reduce relapse. Key PointsO_LITriLeukeVax induces proliferation, activation, and effective anti-leukemic cytolytic responses in remission T-cells. C_LIO_LIPrimed T-cells show polyclonal expansion and transcription profiles associated with proliferation, memory, and cytotoxicity. C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=177 SRC="FIGDIR/small/687000v2_ufig1.gif" ALT="Figure UFIG"> View larger version (38K): org.highwire.dtl.DTLVardef@5c1827org.highwire.dtl.DTLVardef@35b2e2org.highwire.dtl.DTLVardef@1732914org.highwire.dtl.DTLVardef@18df655_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOVisual Abstract.C_FLOATNO TriLeukeVax (TLV) workflow and mechanism of action. Diagnostic AML patient bone marrow aspirates are collected, purified in Ficoll and cryopreserved. Samples are thawed and lentivirally transduced to produce TLV. Vaccination of AML patients in remission with TLV will stimulate the activation and expansion of leukemia-specific T-cells, effector memory cells, and NK cells by combining the co-stimulatory effects of CD80 with immune stimulation by the IL-15/IL-15R heterodimer expressed by the transduced AML cells, thereby targeting MRD and potentially increasing relapse-free survival in AML patients. C_FIG