Rapid and Sustained Increase of LGL and Rare CMV-Reactivation During Dasatinib Treatments in CML

Abstract 2752

Dasatinib has extensive inhibition profile on multiple kinases. Clonal expansion of large granular lymphocyte (LGL) is a noteworthy off-target phenomenon. In this study, we investigated the increase of LGL in peripheral blood during dasatinib treatments which were changed from imatinib treatments, in 25 chronic myelogenous leukemia (CML) patients in CP or AP. METHODS: The criteria of the LGL-increase was set by “increase of lymphocytes over 3,000/μL, and increase of LGL count over 1,500/μL” was found during the course of the treatment. Flow cytometry analyses were performed during the treatments in all cases, and also before the dasatinib treatments in 17 cases. T-cell receptor (TCR) clonal rearrangements for TCR-β, -γ, and -δ, were examined by PCR-based method during the treatments in all cases. Furthermore, comparison of LGL counts before and 2 hours after oral intake were investigated in all 25 cases. CMV activations were assessed in all cases by serum CMV-IgG, serum CMV-IgM, and by “CMV antigen test Teijin (HRP-C7)” which can detect CMV pp65 antigen in leukocytes. RESULTS: Median follow-up time was 11 months (range 3–28). (1) Fifteen out of the 25 patients (60%) showed increase of LGL, which had not been observed during preceding imatinib treatments. Median time until LGL count reached 1,500/μL was 11 weeks (range 6–44), and increased-LGL sustained as far as dasatinib was continued. In these 15 patients, all showed increase of CD56+, CD16+, CD3- NK-cells, and 11 patients also showed increase of CD3+, CD8+, CD4- T-cells. Evident increase of γδ-T cells was not observed. Clonal rearrangements of TCR-β gene were observed in 13 of 15 (87%), and TCR-γ in 12 (80%), and TCR-δ in 9 (60%) patients. Pleural effusions were observed in 9 out of 15 (60%) patients. Regarding clinical response, 4 cases newly achieved CMR, 7 maintained CMR (totally 73% achieved or maintained CMR), and 3 achieved or maintained MMR. (2) On the other hand, 10 out of 25 patients (40%) did not show increase of LGL. In these 10 patients, clonal rearrangements of TCR-β gene were observed in 4 of 10 (40%), and TCR-γ in 3 (30%), and TCR-Δ in 4 (40%) patients. Three patients showed no clonality for all the three TCR genes. Pleural effusions were observed in 2 out of 10 (20%) patients. Regarding clinical response, no case newly achieved CMR, 5 maintained CMR (totally 50% achieved or maintained CMR), and 4 achieved or maintained MMR. (3) LGL counts increased 2 hours after intake of dasatinib in all patients. Regarding the 15 patients who showed LGL increase during the treatment courses, LGL counts were 1,349±918/μL (mean±SD)(before), and 2,895±2,240/μL (2 hours after), indicating 2.1 times increase (P=0.006); total lymphocyte counts were 2,153±1,129/μL (before), and 4,456±3,219/μL (after), indicating 2.1 times increase (P=0.01). Regarding the 10 patients who did not show LGL increase during the treatment courses, LGL counts were 422±384/μL (before), and 805±419/μL (after), indicating 1.9 times increase (P=0.02); total lymphocyte counts were 1,094±556/μL (before), and 1,859±899/μL (after), indicating 1.7 times increase (P=0.03). (4) In the total 25 patients, serum CMV-IgM were negative in most of the cases (23 of 25; 92%). CMV HRP-C7 were completely negative (meaning undetectable) in most of the cases (23 of 25; 92%), and it was barely positive only in 2 cases (1 cell and 2 cells were positive out of ∼60,000 leukocytes examined, respectively). CONCLUSION: LGL lymphocytosis occurred in 60% of patients, which seems to be related with favorable molecular responses, and with relatively high incidence of pleural effusions. The TCR gene rearrangements were observed in both groups, but higher in the increase-LGL group than the non-increase-LGL group. Approximately 2-times rapid increase of LGL and total lymphocytes were observed 2 hours after intake of dasatinib, in all the patients, irrespective of the LGL-increase during the treatment courses. In the clinical setting, evident immunodeficiency was not observed in terms of CMV-reactivation.