Because Ad-CD154-infected CLL B-cells could induce autologous T-cells to generate cytotoxic T-cells against the patient's leukemia cells in vitro, we developed a phase I clinical trial to examine this effect in patients with CLL (78). Leukemia cells were harvested by pheresis and then infected ex vivo with Ad-CD154 in a good-manufacturing practice facility. The cells were examined for expression of the CD154 and immune costimulatory molecules. After sterility testing, some of the modified leukemia cells were administered back to the same patient as a single intravenous injection given over a few minutes. This strategy allowed us to conduct a dose-escalation study, in which we could infuse defined numbers of leukemia cells that expressed defined amounts of the CD154-transgene.
Two patients in our pilot group received 3 x 108 autologous CLL cells, of which less than a few percent expressed the CD154 transgene. Although the infusion was well tolerated, the patients did not show any biological or clinical effects. Subsequently, three patients received 3 x 108 (group 1), three received 1 x 109 (group 2), and three received 3 x 1010 (group 3) autologous Ad-CD154 CLL cells. For all patients in these groups, about half of the Ad-CD154-transduced CLL cells expressed the CD154 transgene. Furthermore, unlike the cells used in the pilot patients, the modified CLL B cells for patients in groups 1-3 expressed high levels of immune costimulatory molecules resulting from high-level expression of the CD154 transgene.
The intravenous infusion of transduced cells was well tolerated. None of the patients experienced immediate toxicity or adverse events. The patients in groups 1, 2, and 3 commonly experienced flu-like symptoms. These included fever, fatigue, and anorexia, which began within
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