A Phase I Trial of Autologous Dendritic Cell Therapy for Chronic Myelogenous Leukemia.

This phase 1 clinical trial evaluated the safety and effects of autologous dendritic cells (DC) injected to patients in late chronic or accelerated phase of chronic myelogenous leukemia (CML). Seven patients with a median age of 63 years (range 55–78) entered the trial. Median time from diagnosis to registration was 38 months (range 16–94). Two patients were in the accelerated phase of disease based on the presence of additional bone marrow chromosomal abnormalities, all other patients were in chronic phase. Prior therapies included hydroxyurea and alpha interferon with or without cytosine arabinoside. Four patients were on therapy with imatinib mesylate during the course of the trial, two were treated before imatinib became available and one was previously intolerant of imatinib. CD14+ monocytes were selected from a leukapheresis product by clinical grade immunoadsorption (Miltenyi Biotec). The monocytes were matured to CD83+ and bcr-abl+ DC after 10 days in culture with X-VIVO 15 medium with 1% human AB serum, GM-CSF, IL-4, as the base culture media followed by maturation mediated by TNF-alpha, IL-6 and prostaglandin E₂. The first patient entered had a positive mycoplasma reaction by polymerase chain reaction at the time of his first DC injection, the cells were not given and he was withdrawn from the study. The other six patients were treated in two cohorts of three patients and received four injections each of 3x10⁶ DC and 15x10⁶ DC per injection, respectively. CML-DC injections were generally well tolerated and all non-hematologic toxicities were ≤ grade 2. All injections were given intra-nodally into a cervical lymph node except in the first patient where the DCs were injected subcutaneously. We observed no major clinical responses, but the white blood cell counts normalized or were maintained at normal level in four patients during therapy. Three patients experienced a transient reduction in the percentage of bcr-abl+ cells suggesting that the treatment may have affected the cells in a leukemia specific manner. We detected vascular endothelial growth factor (VEGF) in the plasma prior to therapy. In four of five patients, VEGF levels decreased by more than 75 percent during therapy. T cells isolated from patients’ blood and incubated with autologous CML DC before, during and after therapy showed increased proliferation and secretion of interferon gamma during the course of therapy. DCs from three patients were transfected with a recombinant replication-defective adenovirus carrying the gene for IL-2 under a constitutively active promoter. IL-2 secreted by transfected dendritic cells enhanced in vitro T cell proliferation and interferon gamma release and these effects increased with increasing numbers of DC injections. This study demonstrates that CML-DC can be prepared from the blood of patients treated with imatinib mesylate, that they can be administered safely and that progress of therapy is accompanied by an increase in DC-specific T cell reactivity and a decrease in circulating VEGF.