Chemoimmunotherapy for relapsed/refractory and progressive 17p13-deleted chronic lymphocytic leukemia (CLL) combining pentostatin, alemtuzumab, and low-dose rituximab is effective and tolerable and limits loss of CD20 expression by circulating CLL cells

Abstract

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL) patients with purine analog refractory disease or TP53 dysfunction still have limited treatment options and poor survival. Alemtuzumab-containing chemoimmunotherapy regimens can be effective but frequently cause serious infections. We report a Phase II trial testing the efficacy and tolerability of a short-duration regimen combining pentostatin, alemtuzumab, and low-dose high-frequency rituximab designed to decrease the risk of treatment-associated infections and to limit the loss of CD20 expression by CLL cells. The study enrolled 39 patients with progressive CLL that was either relapsed/refractory (n = 36) or previously untreated with 17p13 deletion (17p13-) (n = 3). Thirteen (33%) patients had both 17p13- and TP53 mutations predicted to be dysfunctional, and eight patients had purine analog refractory CLL without TP53 dysfunction. Twenty-six (67%) patients completed therapy, with only five (13%) patients having treatment-limiting toxicity and no treatment-related deaths. Twenty-two (56%) patients responded to treatment, with 11 (28%) complete responses (four with incomplete bone marrow recovery). Median progression-free survival was 7.2 months, time to next treatment was 9.1 months, and overall survival was 34.1 months. The majority of deaths (82%) were caused by progressive disease, including transformed diffuse large B-cell lymphoma (n = 6). Correlative studies showed that low-dose rituximab activates complement and natural killer cells without a profound and sustained decrease in expression of CD20 by circulating CLL cells. We conclude that pentostatin, alemtuzumab, and low-dose high-frequency rituximab is a tolerable and effective therapy for CLL and that low-dose rituximab therapy can activate innate immune cytotoxic mechanisms without substantially decreasing CD20 expression.

Trial registration: ClinicalTrials.gov NCT00669318.

© 2014 Wiley Periodicals, Inc.

Figures

Figure 1. Response to Therapy

The median progression free survival was 7.2 months (95% confidence interval (CI): 5.3;18.3) (A) and 21 patients received subsequent treatment for progressive CLL with a median time to next treatment of 9.1 months (95% CI: 5.7; 27.0)(B). The 11 patients who received subsequent treatment before disease progression are censored and 7 patients did not receive subsequent treatment. Median overall survival was 34.1 months (95% CI: 13.6; not reached)(C).

Figure 2. Effects of rituximab infusion on absolute lymphocyte count, CD20 levels, and C3d deposition

A. Absolute lymphocyte counts (ALC) are reduced as a result of rituximab therapy (20 mg/m2/dose) on day 1, day 3 and day 5 with additional therapy with alemtuzumab on days 3, 4 and 5. All values are normalized to the pre-infusion levels on day 1 for each patient. There was a decrease in ALC 48 hours after the first rituximab infusion, and a further decrease was observed over the course of day 3 treatment with a second rituximab infusion, followed by a small increase on day 8, despite the additional monoclonal therapy on days 4 and 5. Initial ALC varied between 9.8 and 240.0 × 109/L (mean 63 × 109/L). All post treatment normalized ALC values were significantly lower than pre-treatment values (p< 0.001). B and C. Infusion of rituximab leads to transient reduction of CD20 levels (B), and to deposition of C3d fragments on surviving, circulating cells (C). Normalized CD20 and C3d levels are based on analyses of fresh washed whole blood (open circles) or of PBMC which were isolated and then frozen (closed circles) for later analyses. The reduction in CD20 is most evident in the day 3 post-treatment samples. By day 8, CD20 levels had increased, even though rituximab was also infused on day 5. C3d levels are reported as the normalized increase relative to the values for day 1 pre-treatment samples. D and E. The amount of C3d deposited on the cells of patients in the Day 3 post samples is positively correlated with the levels of CD20 on the cells at that time point. In this case MESF values are reported, and the signals are not normalized. D. filled circles: PBMC samples; E. open circles: Fresh samples, Analyses based on Spearman rank correlation gave a correlation coefficient of 0.833 and p= 0.00526 for both plots. F. Within the CLL cell populations of individual patients, in the day 3 post-treatment samples there is a correlation between the amount of C3d deposited and the levels of CD20. Panel i is a plot for cells in a pre-treatment sample. Panels ii and iii are plots for Day 3 Post samples for two different patients. *, p

Figure 3. Effect of Low Dose Rituximab on NK Cells

Treatment of patients with low dose rituximab resulted in significant NK cell activation, as evidenced by significant down modulation of surface CD16 expression (A) (p=0.001) and up regulation of surface CD54 expression (B)(p=0.04). All values are expressed as median fluorescence intensity (MFI). Circulating NK cell percentages showed a significant drop following therapy with low dose rituximab (C) (p