A phase I/II trial of oxidized autologous tumor vaccines during the "watch and wait" phase of chronic lymphocytic leukemia

Abstract

Based on their activity in patients with advanced stage chronic lymphocytic leukemia (CLL), a phase I/II study was designed to evaluate the feasibility, safety, and efficacy of autologous vaccines made from oxidized tumor cells in patients with earlier stage CLL, and to determine an optimal schedule of injections. Eighteen patients (at risk for disease progression and with white blood cell counts between 15 and 100 x 10(6) cells/ml) were injected intramuscularly with 10 ml of oxidized autologous blood (composed mainly of CLL cells) either 12 times over 6 weeks (group 1), 12 times over 16 days (group 2), or 4 times over 6 weeks (group 3). Fourteen out of eighteen patients had Rai stage 0-II disease, while 4/18 had stage III-IV disease but did not require conventional treatment. Partial clinical responses, associated with enhanced anti-tumor T cell activity in vitro, were observed in 5/18 patients of whom three were in group 2. Stable disease was observed in six patients while disease progression appeared not to be affected in the remaining patients. Toxicity was minimal. Vaccination with oxidized autologous tumor cells appears worthy of further investigation and may be a potential alternative to a "watch and wait" strategy for selected CLL patients.

Fig. 1

Clinical course of individual patients. The clinical response to vaccination is shown for each patient during the 6-month period of monitoring while on the study. The WBC counts before vaccination (time 0) and each month during the follow-up period are shown on the x-axis. The schedule of injections for group 1 is indicated by the long horizontal bar (12 injections over 6 weeks). The schedule for group 2 is indicated by the short horizontal bar (12 injections over 16 days) and the schedule for group 3 is indicated by the four vertical bars (four injections on days 1, 2, 21, and 38). The lines with arrowheads indicate booster injections given at monthly injections to patients who appeared to respond to their prescribed injections. The patients are grouped according to their apparent responses to vaccination

Fig. 2

Correlation of clinical responses with changes in anti-CLL T cell reactivity. Blood was taken before and after the vaccination protocol. T cells were isolated as described in the Materials and methods and then cryopreserved. As a measure of anti-CLL T cell reactivity, an aliquot of pretreatment CLL cells was thawed and activated with phorbol esters and IL-2 in order to make them into efficient APCs, as described in the Materials and methods. After 4 days, the activated CLL cells were washed, irradiated, and used to stimulate the T cells from the different time-points (after they had been thawed simultaneously and washed). Subsequent T cell proliferation was measured in a colorimetric assay, 7 days later. a Characteristic results are shown for pt. 18 (who exhibited a PR to the vaccine protocol) and pt. 17 (who did not). T cell proliferation and corresponding WBC counts at the different time points are shown. As a control to ensure that apparent increases in anti-CLL responses were not simply an artifact of freezing conditions at that time point, the ability of the thawed T cells to respond to mitogens was measured (at the time that the anti-CLL assays were set up) by a colorimetric assay after 5 days of stimulation. For pt. 18, the PHA responses at 0, 2, 3, and 6 months were 0.014, 0.007, 0.129, and 0.034, respectively. For pt. 17, these PHA responses were 0.011, 0.070, 0.042, and 0.070, respectively. b The absolute value of the peak T cell proliferation response to CLL cells after vaccination is shown for each patient. The average and standard error was then determined for patients whose disease responded, stabilized, or progressed after the vaccines (as described in Tables 1, 2, and Fig. 1). A response to vaccination tended to correlate with a higher T cell reactivity against CLL cells (approaching statistical significance; p<0.10). c For each patient, the initial anti-CLL T cell proliferative response before vaccination was subtracted from the peak response at any time during the study period (Table 3). The average and standard error of these differences were then determined according to the clinical outcome. The results show that a response to vaccination correlated with a significant increase (p<0.02) in T cell reactivity against CLL cells

Fig. 3

Correlation of costimulatory molecule expression on CLL cells with clinical response to vaccination. a Examples of costimulatory molecule expression by circulating CLL cells. The expression of CD80, CD86, CD54, and CD83 on purified CLL cells were determined by flow cytometry, as described in the Materials and Methods. The percentages of CD80⁺ and CD86⁺ cells (defined as the percentages of cells staining above the first decade of log fluorescence) for each patient (top and bottom rows, respectively) are shown in the upper right quadrants of the dot-plots. b The percentages of CLL cells that expressed CD80 and CD86 were determined for each patient (Table 3). The average and standard error of these numbers for the patients whose disease responded partially to the vaccines (pts. 2, 7, 8, 10, 18), remained stable (pts. 1, 4, 6, 11, 12, 13), or progressed (pts. 3, 5, 9, 14, 15, 16, 17) are shown in the figure. Although not statistically significant (p<0.10), the results suggest that patients whose disease responded, or remained stable, received vaccines that expressed higher levels of CD80