Oral cladribine as primary therapy for patients with B-cell chronic lymphocytic leukemia

Targeting cancer-specific metabolic pathways for developing novel cancer therapeutics

Cancer is a heterogeneous disease characterized by various genetic and phenotypic aberrations. Cancer cells undergo genetic modifications that promote their proliferation, survival, and dissemination as the disease progresses. The unabated proliferation of cancer cells incurs an enormous energy demand that is supplied by metabolic reprogramming. Cancer cells undergo metabolic alterations to provide for increased energy and metabolite requirement; these alterations also help drive the tumor progression. Dysregulation in glucose uptake and increased lactate production via "aerobic glycolysis" were described more than 100 years ago, and since then, the metabolic signature of various cancers has been extensively studied. However, the extensive research in this field has failed to translate into significant therapeutic intervention, except for treating childhood-ALL with amino acid metabolism inhibitor L-asparaginase. Despite the growing understanding of novel metabolic alterations in tumors, the therapeutic targeting of these tumor-specific dysregulations has largely been ineffective in clinical trials. This chapter discusses the major pathways involved in the metabolism of glucose, amino acids, and lipids and highlights the inter-twined nature of metabolic aberrations that promote tumorigenesis in different types of cancer. Finally, we summarise the therapeutic interventions which can be used as a combinational therapy to target metabolic dysregulations that are unique or common in blood, breast, colorectal, lung, and prostate cancer.

Targeting nucleotide metabolism: a promising approach to enhance cancer immunotherapy

Targeting nucleotide metabolism can not only inhibit tumor initiation and progression but also exert serious side effects. With in-depth studies of nucleotide metabolism, our understanding of nucleotide metabolism in tumors has revealed their non-proliferative effects on immune escape, indicating the potential effectiveness of nucleotide antimetabolites for enhancing immunotherapy. A growing body of evidence now supports the concept that targeting nucleotide metabolism can increase the antitumor immune response by (1) activating host immune systems via maintaining the concentrations of several important metabolites, such as adenosine and ATP, (2) promoting immunogenicity caused by increased mutability and genomic instability by disrupting the purine and pyrimidine pool, and (3) releasing nucleoside analogs via microbes to regulate immunity. Therapeutic approaches targeting nucleotide metabolism combined with immunotherapy have achieved exciting success in preclinical animal models. Here, we review how dysregulated nucleotide metabolism can promote tumor growth and interact with the host immune system, and we provide future insights into targeting nucleotide metabolism for immunotherapeutic treatment of various malignancies.

The road to chemotherapy-free treatment in chronic lymphocytic leukaemia

PURPOSE OF REVIEW

The treatment landscape of chronic lymphocytic leukaemia (CLL) has tremendously evolved in the last decades, from chemo to chemoimmunotherapy (CIT) and, eventually, to pathway inhibitors that target critical pathways for leukaemic cells survival. Also, treatment goals are moving towards achieving undetectable minimal residual disease with little toxicity.

RECENT FINDINGS

We performed a thorough review of the history of treatment approvals by both the Food and Drug Administration (FDA) and the European Medicines Agency (EMA). This review especially focuses on therapies that are currently approved by both agencies. The indications and particular characteristics of each drug are examined.

SUMMARY

Currently available treatment approaches for CLL offer the opportunity to individualize therapy for every single patient with CLL. Inhibitors of B-cell receptor (BCR) signalling pathways and antiapoptotic proteins are nowadays the treatment of choice for most CLL patients, but CIT can be an option for younger and fit patients with low-risk disease [mutated IGHV, no del(11q) or del(17p)/TP53 mutations].

Contribution of Apaf-1 to the pathogenesis of cancer and neurodegenerative diseases

Deregulation of apoptosis is associated with various pathologies, such as neurodegenerative disorders at one end of the spectrum and cancer at the other end. Generally speaking, differentiated cells like cardiomyocytes, skeletal myocytes and neurons exhibit low levels of Apaf-1 (Apoptotic protease activating factor 1) protein suggesting that down-regulation of Apaf-1 is an important event contributing to the resistance of these cells to apoptosis. Nonetheless, upregulation of Apaf-1 has not emerged as a common phenomenon in pathologies associated with enhanced neuronal cell death, i.e., neurodegenerative diseases. In cancer, on the other hand, Apaf-1 downregulation is a common phenomenon, which occurs through various mechanisms including mRNA hyper-methylation, gene methylation, Apaf-1 localization in lipid rafts, inhibition by microRNAs, phosphorylation, and interaction with specific inhibitors. Due to the diversity of these mechanisms and involvement of other factors, defining the exact contribution of Apaf-1 to the development of cancer in general and neurodegenerative disorders, in particular, is complicated. The current review is an attempt to provide a comprehensive image of Apaf-1's contribution to the pathologies observed in cancer and neurodegenerative diseases with the emphasis on the therapeutic aspects of Apaf-1 as an important target in these pathologies.

The development and impact of cladribine on lymphoid and myeloid cells in multiple sclerosis

Cladribine is an approved selective immune reconstitution therapy for relapsing-remitting MS (RRMS). It was first developed and used to treat various forms of cancer, particularly leukemia via parenteral administration. The oral tablet version of cladribine was later developed to treat RRMS, an autoimmune disorder of the central nervous system (CNS) with periods of relapse and remission. Cladribine is found to selectively deplete adaptive immune cell types, and its role on innate immune cells is largely unknown. Among the lymphocyte populations and subtypes, the magnitude and kinetics of depletion by cladribine vary substantially. The current consensus on the selective cytotoxic effect of cladribine is that it is dependent on the deoxycytidine kinase (DCK) to 5'nucleotidase (5-NT) ratio of the immune cell type. Nonetheless, there are some discrepancies that cannot be fully elucidated by the DCK:5-NT ratio paradigm. This review aims to delineate the development and pharmacological properties of cladribine, and elucidate its influence on lymphoid and myeloid cells in MS.

Cladribine to Treat Relapsing Forms of Multiple Sclerosis

Cladribine is a purine nucleoside analogue that selectively depletes peripheral lymphocytes without a major impact on cells of the innate immune system. An oral formulation of cladribine has been developed to be given as short courses over two annual cycles. Oral cladribine results in the peripheral depletion of lymphocytes that is gradual, occurring over several weeks, and is not associated with a cell lysis syndrome, has a greater impact on B cells than T cells, and is followed by gradual reconstitution of the peripheral lymphocyte counts over several months. Oral cladribine is effective in relapsing forms of multiple sclerosis. As a selective immune reconstitution therapy (SIRT), cladribine acts as a short-term immunosuppressant, relative to other maintenance immunosuppressive therapies that result in long-term immunosuppression. The main safety signal that has emerge relates primarily to herpes zoster infection, which was more common in patients with higher grades of lymphopenia, in particular grade 3 and 4 lymphopenia. Data from the oral cladribine extension trial and safety register, and reanalysis of the pivotal phase III trial has indicated that oral cladribine is unlikely to be associated with an increased short- to intermediate-term risk of malignancy.

Cladribine prolongs progression-free survival and time to second treatment compared to fludarabine and high-dose chlorambucil in chronic lymphocytic leukemia

We conducted a randomized phase III trial to compare the efficacy and safety of two purine analogs, cladribine and fludarabine, with high-dose chlorambucil, in patients with previously untreated chronic lymphocytic leukemia (CLL). Between 1997 and 2004, 223 patients with CLL were randomly assigned to cladribine, fludarabine or chlorambucil, for six cycles of therapy with frequent health-related quality of life assessments. There was no statistical difference for the primary endpoint of overall response with cladribine (70%), fludarabine (67%) and chlorambucil (59%), or complete remission (12%, 7% and 8%), respectively. However, the median progression-free survival (25, 10, 9 months) and median time to second treatment (40, 22, 21 months) were superior with cladribine. There was no significant difference in overall survival (96, 82 and 91 months), nor in toxicity or HRQoL assessments. Monotherapy with cladribine gives superior PFS and longer response duration than fludarabine and chlorambucil as first-line treatment of CLL.

Hairy cell leukemia: epidemiology, pharmacokinetics of cladribine, and long-term follow-up of subcutaneous therapy

Hairy cell leukemia is often reported as a disease of young males. The male predominance is strong, 4:1, but the median age in the Swedish national compulsory cancer registry is similar to that of follicular lymphoma, i.e. 62 years. The overall 6-year survival in the Swedish registry of patients diagnosed since 2000 is 80%, 93% of patients <60 years, and 68% of those >60 years. The yearly risk of secondary cancers is 1.75%. Cladribine is a prodrug which is selectively activated intracellularly. The intracellular initial half-life is 13 h and the terminal half-life is 30 h. Subcutaneous injection once daily is simple and effective due to 100% bioavailability and no local side effects from injection, and self-administration is easy. Long-term follow-up of Scandinavian patients treated with cladribine (mostly as subcutaneous injections) in the early 1990s shows a >80% 15-year survival from cladribine treatment in <60 years of age, but  <50% in older patients. Survival from diagnosis of these patients was similar for those previously treated and untreated.

Rituximab and subcutaneous cladribine in chronic lymphocytic leukemia for newly diagnosed and relapsed patients

The aim of this study was to investigate the efficacy of combined treatment with rituximab and subcutaneous cladribine in patients with newly diagnosed and relapsed chronic lymphocytic leukemia (CLL). Forty-three patients with active CLL or small lymphocytic lymphoma received rituximab 375 mg/m(2) on day 1 and cladribine 0.1 mg/kg subcutaneously on days 2-6. The treatment was repeated every 4 weeks for a total of four cycles. Sixteen patients were pretreated. The overall response rate was 88% (50% complete remission and 38% partial remission). The median time to treatment failure was 37.9 months. Grade 4 neutropenia developed in 5% of patients. The data indicate that combination therapy with rituximab and cladribine is a valuable and safe treatment for patients with CLL.

Identification of targets and new developments in the treatment of multiple sclerosis--focus on cladribine

Orally available disease-modifying drugs for relapsing-remitting multiple sclerosis (MS) represent an unmet need for this chronic and debilitating disease. Among 5 currently investigated drugs at phase 3 clinical stage, promising efficacy data for fingolimod and oral cladribine have recently been published. However, benefits need to be weighed against the risks to define the role of these compounds within current treatment regimens. In this review, data on the efficacy of a promising compound, oral cladribine, are discussed and balanced with known and anticipated risks in a postmarketing era, and finally gives an outlook on the potential place of this drug in treatment algorithms for MS in the future.

Development of oral cladribine for the treatment of multiple sclerosis

Multiple sclerosis (MS) is a chronic immune-mediated disorder of the CNS in which autoreactive CD4+ and CD8+ T lymphocytes, B lymphocytes, antibodies, macrophages and cytokines synergize to attack myelin sheaths and injure underlying axons. Current disease-modifying drugs (DMDs) for MS require regular and frequent parenteral administration and are associated with limited long-term treatment adherence. Of all the potential new oral MS agents in development, cladribine is the only therapy with the potential for short-course dosing. Cladribine is an immunosuppressant that offers targeted, sustained regulation of the immune system and that has a well-characterized safety profile, derived from more than 15 years of use of the parenteral formulation in oncology indications and MS. This paper discusses the need for new MS therapies to improve treatment adherence, and reviews the mechanism of action, existing efficacy and safety data, and the clinical development of oral cladribine. The need for continuous risk monitoring for all new potent immunoactive drugs under development is emphasized. Preliminary results of the 96-week, double-blind, randomized, placebo-controlled, multicenter CLARITY (CLAdRIbine Tablets Treating MS OrallY) study are encouraging and provide the first complete phase III data on an oral DMD for MS.

[Cladribin. Development of an oral formulation for the treatment of multiple sclerosis]

Multiple sclerosis (MS) is a chronic, immune-mediated disease of the central nervous system in which autoreactive CD4(+) and CD8(+) T lymphocytes, B lymphocytes, macrophages, antibodies, and cytokines attack the myelin sheaths and damage the axons. The basic therapeutic agents and disease-modifying drugs that are currently available for MS require regular and frequent parenteral administration and therefore long-term compliance is unsatisfactory. Among all of the new oral MS agents presently under development, cladribine is the only substance that appears able to achieve long treatment-free intervals after only short-term administration. Cladribine is an immunomodulator with a long-lasting effect and a well-characterized safety profile based on over 15 years of experience with the parenteral route for MS and other indications. This contribution addresses the need for novel MS treatment approaches to improve compliance and describes the mechanism of action of cladribine, the available data on effectivity and safety, and the clinical development of the oral formulation of cladribine. The results from the recently published 96-week, double-blind, randomized, placebo-controlled, multicenter study CLARITY (CLAdRIbine Tablets Treating MS OrallY) are very promising. They clearly show that oral cladribine reduces relapse rate, disability progression and disease activity and burden as evidenced by MRI.

Recent progress in the management of chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a clonal disease characterized by proliferation and accumulation of small CD5-positive B cells. More than 50% of patients are asymptomatic at diagnosis and usually require no treatment. However, treatment is needed in the advanced and progressive disease. Chlorambucil with or without steroids has been the drug of choice for many years in previously untreated patients with CLL. The purine nucleoside analogs (PNAs), fludarabine (FA), cladribine (2-CdA-chlorodeoxyadenosine) and pentostatin (DCF, 2'-deoxycoformycin) also have been introduced for treatment of CLL. Significantly higher overall response (OR) and complete response (CR) and longer progression free survival (PFS) in patients with CLL treated with FA or 2-CdA have been confirmed in randomized, multicenter trials and more recently in meta-analysis. However, the median survival time did not differ between patients treated with PNA and alkylating agents. Combination therapies with PNAs and cyclophosphamide and especially with cyclophosphamide and rituximab are more active than monotherapy in terms of OR, CR and PFS. Several reports have shown significant activity of alemtuzumab in previously untreated and pretreated patients even when refractory to FA. Alemtuzumab also can be used in CLL as a preparative regimen before stem cell transplantation (SCT) and to eliminate minimal residual disease (MRD). Recently, several new agents have shown promise in treating CLL, including new monoclonal antibodies, agents targeting bcl-2 family of proteins, antisense oligonucleotides and other agents. Moreover, autologous and allogenic hematopoietic cell transplantations are increasingly considered for treatment of patients with CLL. In this review current therapeutic strategies in CLL are presented.

Purine analogues: rationale for development, mechanisms of action, and pharmacokinetics in hairy cell leukemia

Cladribine is effective therapy for HCL, and there are several ways to achieve the adequate concentrations of the active metabolites in relevant cells, without the need for long-term continuous infusions. This simplifies therapy, although careful control of patients is required during and after treatment in most instances because of the significant activity of the drug on leukemia cells of various types and also on lymphoid cells and normal stem cells.

Therapy of Chronic Lymphocytic Leukaemia with Purine Nucleoside Analogues

Chronic lymphocytic leukaemia (CLL) is a neoplastic disease of unknown aetiology characterised by an absolute lymphocytosis in peripheral blood and bone marrow. The disease is diagnosed most commonly in the elderly with the median age at diagnosis being about 65 years. The purine nucleoside analogues (PNAs) fludarabine, cladribine (2-chlorodeoxyadenosine) and pentostatin (2'-deoxycoformycin) are highly active in CLL, both in previously treated and in refractory or relapsed patients. These three agents share similar chemical structures and mechanisms of action such as induction of apoptosis. However, they also exhibit significant differences, especially in their interactions with enzymes involved in adenosine and deoxyadenosine metabolism. Recent randomised studies suggest that fludarabine and cladribine have similar activity in CLL. However, clinical observations indicate the existence of cross-resistance between fludarabine and cladribine. Patients who received PNAs as their initial therapy and achieved long-lasting response can be successfully retreated with the same agent. PNAs administered in combination with other chemotherapeutic agents and/or monoclonal antibodies may produce higher response rates, including complete response (CR) or molecular CR, compared with PNAs alone or other treatment regimens. Management decisions are more difficult in elderly patients because of the apparent increase in toxicity of PNAs in this population. In elderly patients, we recommend chlorambucil as the first-line treatment, with PNAs in lower doses in refractory or relapsed patients. Myelosuppression and infections, including opportunistic varieties, are the most frequent adverse effects in patients with CLL treated with PNAs. Therefore, some investigators recommend routine antibacterial and antiviral prophylaxis during and after PNA treatment. This review presents current results and treatment strategies with the use of PNAs in CLL, especially in elderly patients.

Purine nucleoside analogues and combination therapies in B-cell chronic lymphocytic leukemia: dawn of a new era

Purine nucleoside analogues are unique drugs that are effective in a variety of hematologic malignancies. Fludarabine and 2-chlorodeoxyadenosine (2-CdA) are active in chronic lymphocytic leukemia (CLL) both as salvage therapy and in newly diagnosed patients. These agents have revolutionized therapeutic strategies for patients with CLL that had remained unchanged for many years and included alkylating agents-based therapy with no potential for long-term remission or cure. Purine analogues have also been successfully combined with a variety of other chemotherapeutic drugs such as mitoxantrone, cyclophosphamide, corticosteroids, and monoclonal antibodies, specifically Rituximab and CAMPATH-1H. These agents are immunosuppressive and have been associated with opportunistic infections, the incidence of which can be significantly reduced by early recognition and administration of prophylactic antibiotics. In this review, the activity and toxicity of 2-CdA, fludarabine, and pentostatin in CLL as single agents and in combination with conventional chemotherapy are discussed. These drugs are increasingly used as initial therapy in CLL. Such strategies are associated with higher remission rates than have been previously achieved and in some cases, molecular remission, suggesting an important step towards cure.

New directions in the diagnosis and treatment of chronic lymphocytic leukaemia

Chronic lymphocytic leukaemia (CLL) is the most common leukaemia of adults in Western countries. It is a systemic haematological malignancy that originates from B cells (B-CLL) in 95% of patients, while only a minority are derived through malignant transformation of T cells (T-CLL). Although B-CLL is classified as a non-Hodgkin's lymphoma, several issues make this leukaemia a unique entity among malignant lymphoma. Inhibition of the programmed cell death (apoptosis) and upregulation of the anti-apoptotic protein Bcl-2 are key elements of the pathophysiology of B-CLL cells and define clinical prognosis. Furthermore, B-CLL cells are arrested in G0/G1 phase of the cell cycle. Dysfunctional apoptosis and cell cycle are the main reasons for the clinical enigma, that CLL can not yet be cured with conventional chemotherapy. However, the molecular pathways that are responsible for this characteristic feature of the B-CLL cells still need further definition.Recently, considerable progress has been made in defining the molecular basis for the pathogenesis of CLL and in finding new therapeutic options. Recent studies indicate that B-CLL cells may be delineated from two main groups of normal B cells, i.e. pre- and postgerminal B cells, and can be distinguished through lack of or existence of mutations of the V heavy chain gene. This differential mutational status of the Ig V gene has significant impact on patient survival. Modern cytogenetic methods such as fluorescence in situ hybridisation (FISH) have opened a new era in the molecular analysis of CLL cells. Determining the chromosomal aberration of the leukaemic cells has become a standard scientific programme for each clinical trial. The cytogenetic profile may soon help to define a clinical risk profile and guide the various treatment strategies. Further progress has been made in the therapy of CLL. Purine analogues such as fludarabine were able to induce significant improvement in remission rates; however, they did not lead to improved survival. Chimera of murine or rat monoclonal antibodies and human antibodies were designed to treat CLL. Antibodies such as rituximab and alemtuzumab (Campath-1H), directed against CD20 and CD52, respectively, appear as attractive alternatives to conventional chemotherapy because of their lack of significant myelotoxicity. Studies using myeloablative chemotherapy followed by autologous or allogeneic stem cell transplantation were initiated with the hope of finding a cure for CLL. In contrast to autologous stem cell transplantation, allogeneic transplants appear to display a plateau of relapse rates. In conclusion, for many years CLL was considered as a chronic haematological malignancy that required only few diagnostic tools and for whom no hope of cure could be offered. The current review focuses on recent improvements in diagnosis and treatment of CLL that have opened a new era in the management of patients with this systemic malignancy.

Advances in the treatment of hairy-cell leukaemia

Hairy-cell leukaemia (HCL) is an uncommon B-cell chronic lymphoproliferative disorder that accounts for about 2% of all leukaemias. Although the disease is generally indolent in its natural course, the majority of patients require treatment for life-threatening infections due to pancytopenia or symptomatic splenomegaly. During the past 20 years, remarkable progress has been made in the treatment of HCL. Since the introduction of interferon-alpha, splenectomy, which was formerly the standard therapy, has been rarely used. With the purine analogues cladribine and pentostatin, response rates are even better than with interferon-alpha and long-lasting remissions can be achieved in most patients. Therefore, these agents are now considered the treatment of choice. Recently, immunotherapeutic approaches which use monoclonal antibodies have increased the number of therapeutic options for HCL and offer promising salvage strategies for patients who relapse or who are refractory to treatment with purine analogues. In this review the different treatment options available are discussed and recommendations for the clinical management of the HCL are summarised.

Phase II study of cladribine and cyclophosphamide in patients with chronic lymphocytic leukemia and prolymphocytic leukemia

BACKGROUND

One of the mechanisms of action of cladribine is the inhibition of DNA repair of damage caused by radiation, alkylating agents, or other drugs. To determine its antitumor activity in combination with cyclophosphamide, we initiated a Phase II trial of the two agents in patients with advanced chronic lymphocytic leukemia (CLL) or prolymphocytic leukemia (PLL).

METHODS

Twenty-nine patients with refractory or recurrent CLL or PLL received cladribine 4 mg/m(2)/day and cyclophosphamide 350 mg/m(2)/day (both administered intravenously) for 3 days every 4 weeks.

RESULTS

Eleven patients (38%), nine with CLL and two with PLL, had a response. The median duration of response was 12 months. Severe extrahematologic toxicity (National Cancer Institute Grade 3-4) occurred in two patients, consisting of skin rash in one patient and progressive multifocal leukoencephalopathy in the other. The most common form of hematologic toxicity was severe neutropenia, which developed after 25% of the 84 courses was administered. Severe thrombocytopenia and anemia developed after 12% and 7% of the courses, respectively, and five episodes of anemia were immunomediated. In addition, three major infections resulted in the death of one patient.

CONCLUSIONS

Although inferior to the combination fludarabine plus cyclophosphamide, this regimen showed interesting activity in patients with advanced CLL or PLL. Myelosuppression was the major dose-limiting toxic effect.

Re-treatment with cladribine-based regimens in relapsed patients with B-cell chronic lymphocytic leukemia. Efficacy and toxicity in comparison with previous treatment

The aim of the study was to determine the effectiveness and toxicity of cladribine (2-CdA) used alone or in combination with prednisone (P) or cyclophosphamide and mitoxantrone in re-treatment of patients with progressive B-cell chronic lymphocytic leukemia (B-CLL). We analyzed treatment outcome in 40 patients who had responded to previous treatment with 2-CdA-based regimens. Criteria for re-treatment were the same as for the first treatment. The patients were retreated with the same agents if they responded to the first treatment and then relapsed with progressive disease not earlier than 3 months after achieving the first response. Eight patients received 2-CdA alone (0.12 mg kg(-1) d(-1)) i.v. for 5 d, and 21 patients additionally were given P (30 mg m(-2) d(-1)) orally, also for 5 d. Eleven patients received 2-CdA for 3 d combined with cyclophosphamide (650 mg m(-2)) i.v. and mitoxantrone (10 mg m(-2)) i.v. on day 1 (CMC regimen). The cycles were repeated usually at 4 wk intervals or longer if severe myelosuppression or infections occurred. The therapy was finished if complete remission (CR) was achieved or until maximum of six courses. Overall response (OR) in re-treatment was obtained in 16 out of 40 (40%) patients (95% CI 16-64), including 62% after 2-CdA, 33% after 2-CdA +P and 36% after CMC. CR was obtained in four (10%) patients. Residual disease evaluated in the patients with CR by surface immunophenotyping had been demonstrated in 5 out of 16 (31%) patients after the first treatment and in one out of four (25%) patients after re-treatment. The median progression-free survival (PFS) was 16 months (range 3-39) for the first treatment and 9.5 months (range 3-18) for re-treatment (P=0.34). Grade III or IV neutropenia was observed in 20% patients during the first treatment and in 35% patients during re-treatment (P=0.1). 2-CdA-induced thrombocytopenia occurred in 20% and 42% of the patients, respectively (P=0.05). Anemia was also more frequent during re-treatment (35%) than during the first treatment (7%) (P=0.007). Autoimmune hemolytic anemia developed in four (10%) of the patients during or after re-treatment. Severe infections, including pneumonia and herpes reactivation, occurred in 11 patients during the first treatment and in 10 patients during re-treatment. Twelve (30%) patients died during the study. Infections were the cause of death in six and AIHA in two patients. In conclusion, 2-CdA applied in monotherapy or in combination with prednisone or cyclophosphamide and mitoxantrone has therapeutic activity in some B-CLL patients in whom these drugs induced earlier complete or partial remission. However, since the second response is usually shorter and myelotoxicity more pronounced than during the first therapy, more clinical trials to find other therapeutical approaches are necessary.

B-chronic lymphocytic leukemia: practical aspects

B-CLL is the most common adult leukemia in the Western world. It is a neoplasia of mature looking B-monoclonal lymphocytes co-expressing the CD5 antigen (involving the blood, the bone marrow, the lymph nodes and related organs). Much new information about the nature of the neoplastic cells, including chromosomal and molecular changes as well as mechanisms participating in the survival of the leukemic clone have been published recently, in an attempt to elucidate the biology of the disease and identify prognostic subgroups. For the time being, clinical stage based on Rai and Binet staging systems remains the strongest predictor of prognosis and patients' survival, and therefore it affects treatment decisions. In the early stages treatment may be delayed until progression. When treatment is necessary according to well-established criteria, there are nowadays many different options. Chlorambucil has been the standard regimen for many years. During the last decade novel modalities have been tried with the emphasis on fludarabine and 2-chlorodeoxyadenosine and their combinations with other drugs. Such an approach offers greater probability of a durable complete remission but no effect on overall survival has been clearly proven so far. Other modalities, included in the therapeutic armamentarium, are monoclonal antibodies, stem cell transplantation (autologous or allogeneic) and new experimental drugs. Supportive care is an important part of patient management and it involves restoring hypogammaglobulinemia and disease-related anemia by polyvalent immunoglobulin administration and erythropoietin respectively.

Evolving role of ribonucleoside reductase inhibitors in hematologic malignancies

Ribonucleotide reductases catalyze the de novo biosynthesis of deoxyribonucleosides for DNA synthesis. Increased ribonucleotide reductases activity has been associated with malignant transformation and tumor cell growth. The ribonucleotide reductases inhibitors may bind with the R1 subunit of the enzyme (Class 1) or the nonheme iron (Class 2). This review focuses on the therapeutic use of ribonucleotide reductases inhibitors in hematologic malignancies. Hydroxyurea, fludarabine and cladribine have established roles in the management of hematologic malignancies, while other ribonucleotide reductases inhibitors, such as gemcitabine, tezacitabine and heterocyclic carboxaldehyde thiosemicarbazones (e.g., triapine) are being evaluated in clinical trials.

Alkylating agents and nucleoside analogues in the treatment of B cell chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most common form of leukemia in the Western world. The natural clinical course is highly variable and chemotherapy is usually not indicated in early and stable disease. Treatment is needed in the progressive form of this leukemia. Chlorambucil, with or without steroids, has been for many years the drug of choice in the treatment of CLL. More recently, treatment approaches have included nucleoside analogues, (NA) fludarabine (FAMP) and cladribine (2-CdA, 2-chlorodeoxyadenosine), which seem to be the treatment of choice for patients failing standard therapies. Their role as first line therapy is being investigated in randomized trials and the results have recently been published. These studies have shown a higher overall response and complete remission (CR) rate and longer response duration in patients treated initially with NA than with chlorambucil or cyclophosphamide-based combination regimens. In contrast, overall survival is similar in patients treated with NA and alkylating agents. However, the randomized trials were designed as crossover studies which may influence survival. Combined use of NA with other cytotoxic drugs, cytokines, monoclonal antibodies and other agents may increase the CR and prolong survival time. However, the results of randomized trials comparing combination treatment with NA alone are not yet available. In conclusion, alkylating agents still have an important place in the routine management of the majority of CLL patients. NA should be routinely used as second line treatment and possibly as first line therapy in younger patients, who are candidates for potentially curative treatment such as stem cell transplantation and/or monoclonal antibodies.

Oral cladribine for B-cell chronic lymphocytic leukaemia: report of a phase II trial with a 3-d, 3-weekly schedule in untreated and pretreated patients, and a long-term follow-up of 126 previously untreated patients

A phase II study was undertaken to evaluate the efficacy and toxicity of a new schedule of cladribine administration (10 mg/m2 orally daily for 3 d every 3 weeks) in 107 patients with B-cell chronic lymphocytic leukaemia (CLL). To minimize toxicity, treatment withdrawal criteria were defined. The results of the 63 previously untreated patients were retrospectively compared with 63 from an earlier study using a 5-d monthly schedule. The compiled data were analysed for prognostic factors for survival. No significant difference regarding response were seen in the two cohorts of the 126 previously untreated patients. The complete response (CR), nodular partial response (nPR) and partial response (PR) rates were 15%, 21% and 41%. Quality of response had no impact on survival. The 3- and 5-year overall survival for previously untreated patients was 73% and 58%, respectively, with a median follow-up of 54 months. Pretreatment haemoglobin <11.0 g/dl and elevated beta-2-microglobulin had a negative influence on survival. Major infections occurred in 21% of patients in the 3-d study compared with 35% in the 5-d study. The overall response (OR) and CR rates in the 40 previously treated patients were 34% and 5% respectively. Median overall survival was 24 months and median progression-free survival for responding patients was 14 months. Cladribine used as a single agent is an effective treatment with an acceptable safety profile for pretreated and untreated B-CLL. The achievement of complete remission was not a prerequisite for long-term survival.

The role of nucleoside analogues in the treatment of chronic lymphocytic leukemia-lessons learned from prospective randomized trials

The newer purine nucleoside analogues (PNA), fludarabine (FAMP) and cladribine (2-chlorodeoxyadenosine, 2-CdA) have been synthesized recently and introduced into the treatment of chronic lymphocytic leukemia (CLL). The results of large phase II studies indicate that FAMP and 2-CdA are similarly active in CLL. Unfortunately, no prospective randomized study comparing the results of the treatment of CLL patients with FAMP and 2-CdA has been published so far. Significantly higher overall response (OR) and complete remission (CR) in patients treated initially with PNA than with chlorambucil or cyclophosphamide based combination regimens has been recently confirmed in five prospective multicentre randomized trials. These studies have also shown longer response duration in patients treated with PNA than with conventional chemotherapy. Overall survival progression free and events free survival were similar in patients treated with PNA and with chlorambucil or other alkylating agent based regimens. However, the majority of randomized trials were designed as cross over studies and most patients, treated with conventional chemotherapy were given PNA when refractory or in early relapse, which may influence the survival time. The results of a randomized study have shown a higher incidence of neutropenia and infections in patients treated with PNA than with chlorambucil. However. the frequency of autoimmune hemolytic anemia, pure red cell aplasia, secondary neoplasms and Richter's syndrome seems to be similar in patients treated with PNA and standard alkylating agents based chemotherapy. In conclusion, alkylating agents still have an important place in the routine management of the majority of CLL patients. They are in general safe, given on an out patients basis and significantly cheaper than PNA. PNA should be routinely used as second line treatment, and possibly as first line therapy in younger patients, who are candidates for potentially curative treatment such as stem cell transplantation and/or monoclonal antibodies.

Caspase inhibition and N6-benzyladenosine-induced apoptosis in HL-60 cells

As an extension of our recently published work (Mlejnek and Kuglík [2000] J. Cell. Biochem. 77:6-17), the role of caspases in N(6)-benzylaminopurine riboside (BAPR)-induced apotosis in HL-60 cells was evaluated in this study. Here, BAPR-induced apoptosis was accompanied by activation of caspase-3 and caspase-9. However, when these caspases were selectively inhibited, the progression of BAPR-induced apoptosis was not markedly affected. Besides that, activation of caspase-3 and caspase-9 was found to be rather late event in apoptotic process. These results suggested that other caspases might be critically implicated. Indeed, pan-specific caspase inhibitor, Z-VAD-FMK, completely prevented DNA cleavage and apoptotic bodies formation. However, Z-VAD-FMK failed to prevent cell death and it was incapable to fully counteract the main apoptotic hallmark-chromatin condensation. Finally, our data indicate that cellular decision between apoptosis and necrosis is made upon the availability of both caspase proteases and intracellular ATP.

Nucleoside analogues in the treatment of haematological malignancies

The nucleoside analogues are a group of antimetabolite cytotoxics which generally have to be metabolised to the equivalent nucleotide before incorporation into DNA. Cytarabine is a well established component of the treatment of acute leukaemias and has its principal action on dividing cells. New formulations include a liposome encapsulated product for intrathecal use and oral cytarabine ocfosfate which may be suitable for long-term outpatient use. Pentostatin acts by causing accumulation of deoxynucleotides and, although active against hairy cell leukaemia, is associated with a poor tolerance profile. Cladribine and fludarabine have substantial activity in the treatment of chronic lymphocytic leukaemia (CLL) and low-grade non-Hodgkin's lymphoma (NHL). Fludarabine is the more thoroughly investigated of the two and is currently being developed in combination therapies for CLL and NHL and also in a combination with cytarabine for acute myeloid leukaemia. Fludarabine's immunosuppressive activity is being exploited in the conditioning of patients for non-myeloablative stem cell transplantation. Gemcitabine is an established agent in the treatment of a number of solid tumours but also has activity in haematological malignancies which might be exploited by the use of extended infusion schedules. Newer agents including nelarabine, clofarabine and troxacitabine are undergoing clinical evaluation and show promising activity.

Does intensive treatment with high dose chlorambucil and prednisone as first line and cladribine as second line influence the survival of the patients with chronic lymphocytic leukemia?

Cladribine (2-CdA) and fludarabine are the new purine analogs introduced in the treatment of chronic lymphocytic leukemia (CLL). Despite the high response rate, their influence on survival is still uncertain. The aim of this study was a retrospective analysis and comparison of the response rate and survival of CLL patients treated with high dose chlorambucil (HDChl) as first and 2-CdA as second line, with an historical group of patients never treated with purine analogs who received standard doses of chlorambucil (SDChl). We analyzed 347 patients with CLL treated between January 1985 and January 2000. Group A (190 patients) received HDChl (12 mg/m(2) ) with prednisone (P) 30 mg/m(2) daily for 7 days monthly as first line and in refractory or early relapsed patients 2-CdA (0.12 mg/kg/day) for 5 days with or without P (30mg/m(2) ) as second line. Group B (157 patients) received continuous SDChl (4-8 mg/m(2) /day) and P as first line and COP or CHOP as second line. The overall response rate (OR) for the first line was 48,4% in group A and 38,9% in group B (p=0.09). 148 patients in group A and 52 in group B received the second line treatment and the second OR was 19.6% and 13.5%, respectively (p=0.4). At the time of analysis, 124 patients died in group A and 139 in group B. Median survival was 65 months and 50 months, respectively. In group A, survival was longer in advanced Rai stage patients (p=0.001) but in early Rai stage was similar for both groups (p=0.4). We suggest that intensive treatment with HDChl as first line and 2-CdA as second line should be applied in more advanced rather than in less advanced stages of CLL until the final results of randomized clinical trials are available.

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.

Nucleotide requirements for the in vitro activation of the apoptosis protein-activating factor-1-mediated caspase pathway

Adenine deoxynucleosides, such as 2-chlorodeoxyadenosine (2CdA) and fludarabine, induce apoptosis in quiescent lymphocytes, and are thus useful drugs for the treatment of indolent lymphoproliferative diseases. We previously demonstrated that that the 5'-triphosphate metabolite of 2CdA (2CdATP), similar to dATP, can cooperate with cytochrome c and apoptosis protein-activating factor-1 (APAF-1) to trigger a caspase pathway in a HeLa cell-free system. We used a fluorometry-based assay of caspase activation to extend the analysis to several other clinically relevant adenine deoxynucleotides in B-chronic lymphocytic leukemia extracts. The nucleotide-induced caspase activation displayed typical Michaelis-Menten kinetics. As estimated by the V(max)/K(m) ratios, the relative efficiencies of different nucleotides were Ara-ATP > 9-fluoro-9-beta-D-arabinofuranosyladenine 5'-triphosphate > dATP > 2CdATP > 9-beta-D-arabinofuranosylguanine 5'-triphosphate > dADP > ATP. In contrast to dADP, both ADP and its nonhydrolyzable alpha, beta-methylphosphonate analog were strong inhibitors of APAF-1-dependent caspase activation. The hierarchy of nucleotide activation was confirmed in a fully reconstituted system using recombinant APAF-1 and recombinant procaspase-9. These results suggest that the potency of adenine deoxynucleotides as co-factors for APAF-1-dependent caspase activation is due both to stimulation by the 5'-triphosphates and lack of inhibition by the 5'-diphosphates. The capacity of adenine deoxynucleoside metabolites to activate the apoptosome pathway may be an additional biochemical mechanism that plays a role in the chemotherapy of indolent lymphoproliferative diseases.

Management of chronic lymphocytic leukaemia

Chronic lymphocytic leukaemia (CLL) is the most common form of adult leukaemia in Western countries. The diagnosis requires mature-appearing lymphocytes in the peripheral blood to >5 x 10(9)/L. The immunophenotype typically includes B cell antigens CD19, CD20 and CD23, low expression of surface immunoglobulin and CD5+, with other T cell antigens absent. Bone marrow biopsy, although not required for diagnosis, must show at least 30% lymphocytes. Cytogenetic abnormalities are frequent in patients with CLL, and may be associated with poor prognosis. Clinically, most patients are asymptomatic at presentation, with incidental lymphadenopathy and/or hepatosplenomegaly in the routine physical examination. Infections by opportunistic pathogens are the major cause of death. Aggressive transformation occurs in 10% of patients with CLL, most commonly prolymphocytic leukaemia (PLL) and Richter's syndrome. PLL de novo must be differentiated from PLL of an aggressive transformation. The incidences of autoimmune diseases and solid or haemopoietic secondary malignancies are increased in patients with CLL. Clinical stage is the strongest prognostic factor in CLL. There is no indication for early intervention. The current recommendation to start treatment includes disease-related symptoms, massive and/or progressive hepatosplenomegaly or lymphadenopathy, increasing bone marrow failure, autoimmune disease, and recurrent infections. Alkylating agents (e.g. chlorambucil) and nucleoside analogues (e.g. fludarabine) are the most active agents for CLL. Fludarabine induces higher response rates, but no improvement in overall survival has been observed. Fludarabine is the drug of choice for the majority of patients with CLL. Chlorambucil may be helpful for elderly patients with poor performance, and for patients who do not tolerate fludarabine. No drug combination is better than single agents. For patients refractory to initial treatment, referral to a clinical trial is the best choice. Other salvage therapy includes retreatment with the same initial agent (chlorambucil or fludarabine) if initial response was observed, or fludarabine for patients refractory to chlorambucil. Promising new approaches include cycle-active agents, nelarabine, biological therapy such as anti-CD52 monoclonal antibody, bone marrow transplantation, including the use of submyeloablative preparative regimens ('minitransplant') to induce graft-versus-leukaemia effect, and gene therapy. Prophylactic antibacterials and intravenous immunoglobulin should not be used routinely during supportive care. Epoetin may be helpful for patients who have anaemia without obvious cause. Assessment of response to therapy in CLL has been updated by the National Cancer Institute Working Group, and these guidelines are used worldwide for clinical trials.

Phase II study of 2-chlorodeoxyadenosine in combination with chlorambucil in previously untreated B-cell chronic lymphocytic leukemia

The objective was to determine the safety and efficacy of adding a maximally tolerated dose of 2-chlorodeoxyadenosine (2-CdA) to standard chlorambucil (CLB) therapy in previously untreated B-cell chronic lymphocytic leukemia (CLL). Thirty patients with CLL (median age, 64 years) received two courses of 2-CdA given intravenously (2 mg/m2 daily for 7 days) added to biweekly administration of CLB at 30 mg/m2 given orally. The diagnosis of CLL, treatment indications, and response criteria were according to the National Cancer Institute established guidelines. Sixteen patients (53%) had advanced-stage disease, and four (13%) had trisomy 12 abnormality. The overall remission rate was 80%, including 20% complete remission (CR), 30% nodular partial remission (nPR), and 30% partial remission (PR). Minimal residual disease was detected phenotypically in two of five patients with CR and in eight of nine with nPR. Overall, CR, nPR, and PR rates were not influenced significantly by the presence of cytogenetic abnormalities or advanced clinical stage. With a median follow-up of 33 months, 58% of patients who had a response had relapse. Median time to progression in all 30 patients was 30 months, and time to progression and progression-free survival were not significantly different for the different response groups, clinical stages, or cytogenetic groups. Severe neutropenia and thrombocytopenia occurred in 33% and 7% of patients, respectively. Only two patients had documented bacterial infections, and four had herpetic infections. Concurrent combination chemotherapy with abbreviated doses of 2-CdA and standard-dose CLB is feasible and safe in previously untreated CLL. Antitumor activity may be superior to that of CLB alone given in conventional doses. Whether a different schedule of combining these two agents would result in improved outcome is being investigated.

Common resistance mechanisms to nucleoside analogues in variants of the human erythroleukemic line K562

Variants of the human K562 were developed against the nucleoside analogues cytosine arabinoside, 2 chlorodeoxyadenosine, fludarabine and gemcitabine. The resistant lines displayed a high degree of cross-resistance to all nucleoside analogues, with little or no cross resistance to other agents. There was a profound accumulation defect of the different nucleoside analogues in all of the variants. There was a strong overexpression of 5'nucleotidase, measured by rt-PCR and enzyme activity, in all resistant variants. There was a two fold increase of ribonucleotide reductase in the fludarabine resistant line and increased expression of purine nucleoside phosphorylase in the 2 chlorodeoxyadenosine selected line. Karyotypic analysis revealed the loss of a 6(q16;q22) deletion present in the parental line in all of the resistant lines. This portion of chromosome 6 has been shown to contain the gene for 5'nucleotidase. Early events in the transport and metabolism appear to be involved in the resistance mechanisms to nucleoside analogues and are responsible for broad cross resistance to this family of compounds.

Response to cladribine in previously treated patients with chronic lymphocytic leukaemia identified by ex vivo assessment of drug sensitivity by DiSC assay

The ability to identify non-responders to cytotoxic chemotherapy has significant clinical and economic benefits. Differential staining cytotoxicity (DiSC) assays were performed in 34 previously treated patients with chronic lymphocytic leukaemia prior to treatment with cladribine. Of the 28 identified as ex vivo sensitive, 26 achieved a complete (CR) or partial response (PR) (median length of response 1. 5 years, median survival 3.37 years) and two had a >70% fall in lymphocytes: six identified as ex vivo resistant failed to respond. The DiSC assay can accurately identify a subgroup of patients resistant to cladribine.

Cladribine with cyclophosphamide and prednisone in the management of low-grade lymphoproliferative malignancies

The feasibility of combining cladribine with cyclophosphamide and prednisone in the management of indolent lymphoid malignancies was determined. Nineteen patients [nine chronic lymphocytic leukaemia (CLL), seven non-Hodgkin's lymphoma (NHL) and three macroglobulinaemia (M))] received cladribine 0.1 mg kg(-1) per day as a subcutaneous bolus injection on days 1-3 (up to 5 injections) with intravenous cyclophosphamide 500 mg m(-2) on day 1 and oral prednisone 40 mg (m-2) on days 1-5 at 4-weekly intervals up to a maximum of six courses. A total of 80 courses were given. Overall response rate was 88%, with four patients achieving a complete clinical and haematological response and 12 achieving a partial response. Neutropenia WHO grade 4 in two patients and WHO grade 3 infection in one patient were the limiting toxicities on treatment. During the follow-up, WHO grade >3 haematological complications occurred in five patients and WHO grade >3 non-haematological complications in five patients. There were no treatment-related deaths. This study demonstrates the feasibility of the cladribine/cyclophosphamide/prednisone (CCP) combination that appears highly active and safe in the management of indolent lymphoid malignancies.

Long-Term Follow-Up of Patients With Chronic Lymphocytic Leukemia (CLL) Receiving Fludarabine Regimens as Initial Therapy

One hundred seventy-four patients with progressive or advanced chronic lymphocytic leukemia (CLL) have received initial therapy with fludarabine as a single agent or fludarabine combined with prednisone. The overall response rate was 78% and the median survival was 63 months. No difference in response rate or survival was noted in the 71 patients receiving fludarabine as a single agent compared with the 103 patients who received prednisone in addition. The median time to progression of responders was 31 months and the overall median survival was 74 months. Patients over the age of 70 years had shorter survivals. Patients with advanced stage disease (Rai III and IV) had a somewhat shorter survival than earlier stage patients. More than half the patients who relapsed after fludarabine therapy responded to salvage treatment, usually with fludarabine-based regimens. Second remissions were more common in patients who had achieved a complete remission on their initial treatment. The CD4 and CD8 T-lymphocyte subpopulations decreased to levels in the range of 150 to 200/μL after the first 3 courses of treatment. Although recovery towards normal levels was slow, the incidence of infections was low in patients in remission (1 episode of infection for every 3.33 patient years at risk) and decreased with time off treatment. There was no association of infections or febrile episodes with the use of corticosteroids or the CD4 count at the end of treatment and a poor correlation with the increase in CD4 counts during remission. Infectious episodes were less common in patients who had a complete response compared with partial responders. Richter’s transformation occurred in 9 patients and Hodgkin’s disease occurred in 4 patients. Five other patients died from other second malignancies. Fludarabine appears to be an effective initial induction therapy with a reasonable safety profile for patients with CLL.

© 1998 by The American Society of Hematology.

Long-Term Follow-Up of Patients With Chronic Lymphocytic Leukemia (CLL) Receiving Fludarabine Regimens as Initial Therapy

One hundred seventy-four patients with progressive or advanced chronic lymphocytic leukemia (CLL) have received initial therapy with fludarabine as a single agent or fludarabine combined with prednisone. The overall response rate was 78% and the median survival was 63 months. No difference in response rate or survival was noted in the 71 patients receiving fludarabine as a single agent compared with the 103 patients who received prednisone in addition. The median time to progression of responders was 31 months and the overall median survival was 74 months. Patients over the age of 70 years had shorter survivals. Patients with advanced stage disease (Rai III and IV) had a somewhat shorter survival than earlier stage patients. More than half the patients who relapsed after fludarabine therapy responded to salvage treatment, usually with fludarabine-based regimens. Second remissions were more common in patients who had achieved a complete remission on their initial treatment. The CD4 and CD8 T-lymphocyte subpopulations decreased to levels in the range of 150 to 200/μL after the first 3 courses of treatment. Although recovery towards normal levels was slow, the incidence of infections was low in patients in remission (1 episode of infection for every 3.33 patient years at risk) and decreased with time off treatment. There was no association of infections or febrile episodes with the use of corticosteroids or the CD4 count at the end of treatment and a poor correlation with the increase in CD4 counts during remission. Infectious episodes were less common in patients who had a complete response compared with partial responders. Richter’s transformation occurred in 9 patients and Hodgkin’s disease occurred in 4 patients. Five other patients died from other second malignancies. Fludarabine appears to be an effective initial induction therapy with a reasonable safety profile for patients with CLL.

© 1998 by The American Society of Hematology.

Reduced dose of subcutaneous cladribine induces identical response rates but decreased toxicity in pretreated chronic lymphocytic leukaemia. Swiss Group for Clinical Cancer Research (SAKK)

PURPOSE

To study the efficacy and the safety of cladribine (2-chlorodeoxyadenosine, 2-CDA) administered as 24-hour infusions or as subcutaneous bolus injections at two different doses to patients with relapsing or refractory chronic lymphocytic leukaemia (CLL).

PATIENTS AND METHODS

In this non randomised 2-cohort study, 20 patients with pretreated CLL received cladribine at a dose of 0.7 mg/kg/cycle as continuous i.v. infusions over seven days (group 1) and 35 patients were treated at a reduced dose of 0.5 mg/kg/cycle given as s.c. bolus injections for five days (group 2). After two cycles of four week duration, response was assessed. In the case of progressive disease, therapy was discontinued, otherwise a maximum of four additional cycles were administered until best response.

RESULTS

A total of 130 cycles were administered (group 1: 41, group 2: 89). Patient characteristics in both groups were comparable. The median dose intensities were 0.172 mg/kg per week and 0.123 mg/kg per week for groups 1 and 2, respectively (P < or = 0.0001). The overall response rate for all 55 patients was 38% (95% confidence interval (95% CI): 25%-52%), with 5% CR and 33% PR. Response was similar in both patient groups (35% in group 1, 40% in group 2). No association between cladribine dose intensity and response rate was found, and there was no difference between patients relapsing after or refractory to previous therapies (11 of 24 vs. 10 of 31). Median remission duration was six months in both groups. Toxicity, in particular infections (all WHO grades, 34% in group 1 versus 7% in group 2) and myelosuppression (grade 1-4 neutropenia, 72% versus 41% of cladribine cycles) were statistically significantly more frequent in group 1.

CONCLUSION

Cladribine is active in heavily pretreated patients with chronic lymphocytic leukaemias. Dose reduction by 29% led to similar response and remission duration, but to a significant decrease of myelotoxicity and risk of infection. Cladribine administered as s.c. bolus injections at 0.5 mg/kg per cycle is safe and this dose level should not be exceeded in this patient population.