Cellular Pharmacology of Fludarabine Triphosphate in Chronic Lymphocytic Leukemia Cells During Fludarabine Therapy

The pharmacology of fludarabine triphosphate (F-ara-ATP) in leukemic lymphocytes was studied during a phase II trial of fludarabine in 24 patients with chronic lymphocytic leukemia (CLL). Fludarabine was given as a 30-min i.v. infusion at a dose of 25 or 30 mg/m² daily for 5 days. The concentrations of F-ara-ATP, the active metabolite of fludarabine, were determined in leukemic lymphocytes at intervals up to 24 hr after the first infusion. A median peak concentration of 19 μM (range, 6-52 μM) was generally reached 4hr after the beginning of the infusion. No significant relationship was observed between clinical response and the median peak level of F-ara-ATP or the retention of F-ara-ATP in leukemic lymphocytes. In vitro incubation of CLL cells with the parent nucleoside of fludarabine, arabinosyl-2-fluoroadenine (F-ara-A), indicated that F-ara-ATP accumulated in a linear fashion in response to the product of the F-ara-A concentration times the duration of incubation. Exposing cells longer with lower F-ara-A concentrations or shorter with higher F-ara-A concentrations resulted in similar intracellular levels of F-ara-ATP as long as the products of fludarabine concentration and time of exposure were equal. These results and the fact that the fludarabine dose rate currently administered is well tolerated suggest that it may be the optimal dose rate for F-ara-ATP accumulation in CLL cells.     

Survival of Young Patients with Chronic Lymphocytic Leukemia Failing Fludarabine Therapy: A Basis for the Use of Myeloablative Therapies

We examined the survival of 91 young patients (≤ 55 years) with chronic lymphocytic leukemia from the time of failure of fludarabine therapy, in an attempt to identify those with a poor outcome who may benefit from investigative dose-intensive therapies. The median survival of patients unresponsive to fludarabine (n = 42) was 48 weeks, and only 11% responded to subsequent therapies. The median survival of patients relapsing following a fludarabine-induced remission (n = 49) was 87 weeks, and 83% of those who had received fludarabine as their first therapy (n = 14) responded to further fludarabine-containing therapies, with 60% alive at four years. Only 7% of those relapsing patients who had received fludarabine as salvage therapy (n = 35) responded to subsequent therapies (median survival 72 weeks). The poor outlook for these patients justifies the consideration of innovative dose-intensive therapies, such as bone: marrow transplantation, with their attendant risk of toxicity.     

The Complement System in Chronic Lymphocytic Leukemia: A Possible Role in Autoimmune Manifestations

We describe the complement system of three CLL patients who developed autoimmune complications in the course of their disease. The complement profile was pathological in both CLL patients with active autoimmune diseases, while it showed no deficiency in the patient with quiescent autoimmunity. The complement profile could be an early marker for development of autoimmunity in CLL patients.     

Development of PH Positive Chronic Myeloid Leukemia in a Patient with Chronic Lymphocytic Leukemia Treated with Total Body Irradiation: A Rare Association

Philadelphia (ph) chromosome positive chronic myeloid leukemia developed in a patient treated for chronic lymphocytic leukemia after treatment with total body irradiation. The role of radiation in the development of CML is discussed.     

Phase II Clinical Trial of Fludarabine in Chronic Lymphocytic Leukemia on a Weekly Low-Dose Schedule

The major complication during therapy of chronic lymphocytic leukemia (CLL) with the purine nucleotide analogue fludarabine is infection, which is also the main cause of morbidity and mortality in the disease. As the incidence of infectious episodes during therapy correlated with severity of neutropenia, stage of disease, and response to therapy, an effort was made to reduce therapy-related myelosuppression and improve response by altering the conventional therapy regimen. The protocol which yielded a response rate of 57% in previously treated patients with CLL consisted of five consecutive daily doses of 25-30 mg/m^z fludarabine given every three to four weeks. Based on observations from intracellular pharmacology studies it was hypothesized that repetitive single weekly doses of fludarabine would allow normal bone marrow cells to recover while maintaining cytotoxic levels in the leukemic cells. The cumulative four-week dose of the once-weekly regimen was approximately 80% of the original protocol.

Eleven out of 46 evaluable patients (24%) responded to the therapy. Seven patients (15%) achieved a complete remission, and four (9%) a partial remission. While myelosuppression was reduced by about 30% compared with the original protocol, the incidence of febrile episodes was increased by 17%. Pretreatment serum IgG levels below the normal range correlated significantly with a high incidence of infectious episodes and with a short median survival time. These observations suggest that in addition to myelosuppressive therapy, disease related depressed immune function causes morbidity and mortality due to infections. The results further show that changes in the scheduling of the therapy regimen, associated with a slightly lower dose, resulted in reduced efficacy as measured by the response rate.     

Two Distinct Clinical Patterns of Ibrutinib-to-Venetoclax Transition in Relapsed Chronic Lymphocytic Leukemia Patients

Patients with chronic lymphocytic leukemia (CLL) relapsing on ibrutinib are often treated with the Bcl-2 inhibitor venetoclax. However, the transition from one agent to another poses some clinical challenges due to disease flares sometimes occurring right after ibrutinib interruption. Here, we describe three clinical vignettes highlighting two distinct patterns of ibrutinib-to-venetoclax transition. While patients following the favorable pattern transited to venetoclax without experiencing disease flare, the one patient who took the unfavorable path showed rapid disease rebound, with large-cell transformation occurring one week after ibrutinib interruption. A high burden of BTK and PLCG2 mutations was found only in patients with the favorable transition pattern, suggesting that removing BTK inhibition might be particularly harmful if CLL cells are progressing through mechanisms external to the BTK axis.     

Cladribine in the Treatment of Chronic Lymphocytic Leukemia

Cladribine (2-chlorodeoxyadenosine, 2-CdA) is a nucleoside analog with substituted halogen atom at position 2 in its purine ring that makes it resistant to deamination by adenosine deaminase (ADA). 2-CdA is the drug of choice in the treatment of hairy cell leukemia, but it is also highly active in other low grade lymphoid malignancies including chronic lymphocytic leukemia (CLL). The results of the studies presented so far have shown that 2-CdA gives similar complete response (CR) rate and overall response (OR) rate to fludarabine but the influence of both agents on survival times of the patients with CLL is still uncertain. CR rate induced with 2-CdA is significantly higher than in the patients treated with conventional chemotherapy. In refractory or relapsed patients 2-CdA induces 31 to 68% of overall responses including CR in 4 to 31%. In previously untreated patients overall remission rates of about 56-82% have been achieved with 2-CdA alone. When 2-CdA was used as primary therapy the CR rate was also significantly higher and ranged from 10% to 47%. Patients who received 2-CdA as their initial therapy and experienced a response lasting at least a year may be successfully treated subsequently with the same agent. A second response has been achieved in 35 to 100% patients treated with this agent for the second time. Despite the fact that 2-CdA gives higher CR and OR rates than conventional chemotherapy, it has not been established whether it has any influence on survival time. However, cross resistance between 2-CdA and FAMP in CLL patients is evident in the majority of studies. Bone marrow suppression with anemia neutropenia and thrombocytopenia are the dose limiting factors for 2-CdA use. These side effects are pronounced in heavily pretreated patients and after multiple courses of therapy. Treatment with this agent also leads to the decrease of the CD4+/CD8+ ratio for an extensive period of time exceeding 12, even up to 24 months. In consequence, infections including opportunistic type, are frequently observed. We suggest, that in patients with CLL, 2-CdA should be used as second line treatment rather than the first line therapy until the final results of ongoing randomized clinical trials are available.     

Invasive Fungal Disease in Patients with Chronic Lymphocytic Leukemia in Japan: A Retrospective Database Study

Invasive fungal disease (IFD) is an important cause of morbidity and mortality in patients with hematological malignancies. As chronic lymphocytic leukemia (CLL) is a rare hematological malignancy in Japan, IFD incidence in Japanese patients with CLL is unclear. This study aimed to investigate IFD incidence in Japanese patients with CLL. This retrospective cohort study used data of patients with CLL registered between April 2008 and December 2019 in the Medical Data Vision database (n = 3484). IFD incidence after CLL diagnosis in the watch-and-wait (WW) and drug therapy (DT) groups was 1.5% and 9.2%, respectively. The most common type of IFD was invasive aspergillosis (28.1%). Cox proportional hazards multivariate analysis revealed that DT (hazard ratio [HR]: 2.13) and steroid use (HR: 4.19) were significantly associated with IFD occurrence. IFD incidence was significantly higher in the DT group than in the WW group (log-rank p < 0.001); however, there was no significant between-group difference in the time to IFD onset or the type of IFD (p = 0.09). This study determined the incidence of IFD in patients with CLL during WW. Physicians should monitor for IFD, even among patients with CLL undergoing the WW protocol.     

Alterations of the Retinoblastoma a Susceptibility Gene in Chronic Lymphocytic Leukemia

Research in recent years has shown that malignant transformation is a genetic multistep process. This holds true not only for in-vitro model systems, but has also been elegantly shown in-vivo, as in colorectal cancer. Chronic lymphocytic leukemia (CLL) is the most frequent leukemia in Western countries and occurs mainly in elderly patients, suggesting that in this form of leukemia, cumulative molecular lesions may be necessary for transformation. However, the molecular background is unknown in most cases. Cytogenetic aberrations may be used as markers for genes, involved in the process of malignant transformation. In CLL, the most frequently observed structural cytogenetic lesion is a deletion/translocation involving the long arm of chromosome 13, a region where the retinoblastoma susceptibility gene (Rb-gene) has been mapped (13q14). Many groups have studied the question as to whether alterations of the Rb-gene play a causal role in the pathogenesis of CLL., This review deals with recent data indicating that i) the Rb-gene may be altered in a minority of CLL cases, and ii) there may be another gene localized on chromosome 13q14 that may be important in the molecular biology of CLL.     

Chronic Lymphocytic Leukemia Associated with Myelodysplastic Syndrome and/or Chronic Myeloid Leukemia: Evidence for Independent Clonal Chromosomal Evolution

We describe the cytogenetic findings of three cases with simultaneous or sequential development of a B-chronic lymphocytic leukemia (B-CLL) and either a myelodysplastic syndrome (MDS) in 2 cases or a chronic myeloid leukemia (CML) in one case. The coexistence of these two hematologic malignancies leads to questions about their cell of origin. Through analysis of the cytogenetic abnormalities, we studied the derivation of both malignancies. The cytogenetic analyses of these three patients were simultaneously studied from both peripheral blood and bone marrow. Furthermore unstimulated short-time (USSTC) and long-time (72-96 hours) stimulated cultures (LTSC) were systematically performed. In all cases, we have demonstrated the independent bi-clonal evolution. This is the first report ever described for patients with CLPD and MDS and/or MPD shown to arise from distinct chromosomal abnormalities.     

Hypersensitivity of Lymphocytes from Chronic Lymphocytic Leukemia Patients to Ultraviolet Light-C Radiation

Chronic lymphocytic leukemia (CLL) results in the accumulation of mature immunologi-cally defective lymphocytes in GO phase. Lymphocytes from CLL patients were exposed to UVC radiation to determine whether these cells are capable of undergoing apoptosis, as a response to DNA damage. Lymphocytes from CLL patients were found to be readily killed by ultraviolet light-C (UVC) radiation. Cells from healthy donors were minimally affected by doses of UVC ten times higher then those which caused dramatic drops in the metabolism of CLL cells. At four hours after irradiation, the reduction of 3-(4,5-dimethylthia-zol-2-yl)-2,5-diphenyl tetrazoliurn bromide (MTT) had dropped by 50% for CLL cells exposed to a dose of 10 J/m². In contrast, there was no significant drop for healthy cells exposed to 100 J/m². Cell death was measured by trypan blue staining, flow cytometry of Annexin V-PI stained cells, and Wright staining. By 24 hours after irradiation, significant amounts of cell death were observed in CLL cells at doses which had no significant effects on viability of healthy lymphocytes. The extreme sensitivity of CLL lymphocytes to UVC indicates that phototherapy should be explored as a potential treatment for this neoplasm.