Purine nucleoside analogues for the treatment of hematological malignancies: pharmacology and clinical applications

The purine nucleoside analogues (PNAs), fludarabine (FA), 2-CdA (2-chlorodeoxyadenosine, 2-CdA) and pentostatin (2'-deoxycoformycin, DCF) represent a group of cytotoxic agents with high activity in lymphoid and myeloid malignancies. PNAs share similar chemical structure and mechanism of action. Several mechanisms could be responsible for their cytotoxicity both in proliferating and quiescent cells, such as inhibition of DNA synthesis, inhibition of DNA repair and accumulation of DNA strand breaks. Induction of apoptosis through the mitochondrial pathway, direct binding to apoptosome or modulation of p53 expression all lead to apoptosis, which is the main end-point of PNA action. However, individual PNAs exhibit significant differences, especially in their interaction with enzymes involved in adenosine and deoxyadenosine metabolism. Synergistic interactions between PNAs and other cytotoxic agents (alkylating agents, anthracycline antitumor antibiotics, cytarabine, monoclonal antibodies) have been demonstrated in both preclinical and clinical studies. PNAs are highly effective in chronic lymphoid leukemias and low grade B- and T-cell non-Hodgkin's lymphomas, including Waldenström's macroglobulinemia. DCF and 2-CdA are currently the drugs of choice in hairy cell leukemia. Moreover, clinical studies have confirmed the efficacy of PNAs alone or in combination protocols in the treatment of acute myeloid leukemia and myelodysplastic syndromes. Finally, PNAs, especially FA, play an important role in non-myeloablative conditioning regimens for allogenic stem cell transplantation in high-risk patients. The toxicity profiles of PNAs are similar for all agents and consist mainly of dose-limiting myelotoxicity and prolonged immunosuppression. Three other compounds: clofarabine, nelarabine and immucillin-H are currently being evaluated clinically.

Activity of Cladribine Combined with Etoposide in Heavily Pretreated Patients with Indolent Lymphoid Malignancies

We determined the effectiveness and toxicity of combined chemotherapy consisting of etoposide 100 mg/m(2)/day i.v. and cladribine (2-CdA) 0.12 mg/kg/day i.v. each for 5 days (EC regimen) in the treatment of refractory or relapsed low-grade non-Hodgkin's lymphoma and chronic lymphocytic leukemia. The cycles were repeated every 28 days, reaching a maximum of six courses. Twenty patients entered the study. All patients had received three or more cycles of chemotherapy before the EC regimen (median 8, range 3-19). Thirteen patients received 2-CdA before the EC regimen. Seven out of 20 patients (35%) responded, including one complete response. Median overall survival time of responding patients was 22 months (range 3-30). Myelosuppression and infections were the major toxicity of the EC regimen.

Second malignancies and Richter's syndrome in patients with chronic lymphocytic leukaemia treated with cladribine

The increased frequency of second malignancies in chronic lymphocytic leukaemia (CLL) is well known. Moreover, antineoplastic therapy additionally increases the risk of secondary cancers. In this study, we analysed whether treatment with cladribine (2-chlorodeoxyadenosine, 2-CdA) during the course of CLL had an impact on the subsequent occurrence of either secondary solid tumours or Richter's syndrome. There were 1487 eligible patients, 251 treated with 2-CdA alone, 913 treated with alkylating agents (AA)-based regimens alone and 323 treated with both 2-CdA and AA. Median time from the start of CLL treatment to the diagnosis of secondary malignancy was 1.9 years (0.5-5.1 years) for the 2-CdA group, 1.8 years (0.3-7.9 years) for the AA group and 3.9 years (0.3-8.4 years) for the 2-CdA+AA group. A total of 68 malignancies were reported in 65 patients. Ten events were non-melanotic skin cancers and were excluded from the analysis, leaving 58 events in 58 patients. In the group of patients treated with 2-CdA alone, there were 15 (6.0%) cases, in the group of patients treated with AA alone there were 26 (2.8%) cases, and in the group treated with 2-CdA+AA there were 17 (5.3%) cases of secondary malignancies. The differences between the frequency of secondary malignancies in the 2-CdA and 2-CdA+AA versus AA alone groups were not significant (P=0.05 and P=0.06, respectively). Only lung cancers occurred significantly more frequently in the 2-CdA (2.8%) and 2-CdA+AA (2.2%) treated groups compared with the AA patients (0.3%) (P<0.001 and P<0.01, respectively). In conclusion, 2-CdA in CLL patients does not seem to increase the risk of secondary malignancies except for lung cancers. However, further studies are necessary to establish the real risk of lung cancer in CLL patients treated with 2-CdA.

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.

Cladribine in combination with mitoxantrone and cyclophosphamide(CMC) in the treatment of heavily pre-treated patients with advanced indolent lymphoid malignancies

The aim of our study was to determine the effectiveness and toxicity of combined chemotherapy consisting of cladribine (2-chloro-deoxyadenosine, 2-CdA), mitoxantrone and cyclophosphamide (CMC regimen) in the treatment of refractory or relapsed indolent lymphoproliferative disorders. The treatment course consisted of 2-CdA given at a dose of 0.12 mg/kg/24 h in a 2-h intravenous infusion for 5 (CMC5) or 3 (CMC3) consecutive days, mitoxantrone 10 mg/m2 on day 1 and cyclophosphamide 650 mg/m2/iv on day 1. Thirty-three patients (19 with B-CLL and 14 with LG-NHL) entered the study and all of them were eligible. Twenty patients (60.6%) were recurrent after prior therapy and 13 (39.4%) had refractory disease. All patients received 5 or more cycles of chemotherapy before CMC treatment. Twenty-one patients were treated with CMC5 regimen and 12 with CMC3 regimen. The overall response rate, including CR and PR, was 48.6% (95% CI 32-66). There were no differences in the frequency of responses between the CMC3 and CMC5 treated groups (p>0.05). One patient with B-CLL and three patients with lymphocytic lymphoma achieved CR (12.1%). Among 12 patients (36.4%) who achieved PR there were 6 CLL patients, and 6 lymphoma patients. The major toxicity was myelosuppression. Severe neutropenia was seen in 11/33 (33.3%) patients, more frequently in patients who received CMC5 than in the patients who received CMC3, both in the CLL (50.0% and 28.5%, respectively) and in the LG-NHL group (22.2% and 0%, respectively). The rate of thrombocytopenia was similar in both groups. Infections and fever of unknown origin complicated the treatment with CMC5 more often than with CMC3: five episodes were seen in 3 patients treated with CMC3 when compared to 15 episodes in 12 patients treated with CMC5. In conclusion, the CMC programme is an active combined regimen in heavily pre-treated CLL and LG-NHL patients. However, its toxicity is significant and we suggest a shortening of 2-CdA infusion from 5 to 3 d in further studies. Whether a combination of 2-CdA with cyclophosphamide and mitoxantrone would result in improved outcome as compared to 2-CdA alone, is being investigated in a prospective, randomised trial.

Cladribine combined with cyclophosphamide and mitoxantrone as front-line therapy in chronic lymphocytic leukemia

The objective of the study was to determine the effectiveness and the toxicity of a combined chemotherapy consisting of cladribine (2-CdA), mitoxantrone and cyclophosphamide (CMC regimen) in the treatment of previously untreated B cell chronic lymphocytic leukemia (B-CLL). From August 1998 to December 2000 2-CdA was administered at a dosage of 0.12 mg/kg for 3 (CMC3) or 5 (CMC5) consecutive days, mitoxantrone at 10 mg/m2 on day 1 and cyclophosphamide at 650 mg/m2 on day 1 to 62 patients with advanced or progressive B-CLL. The cycles were repeated at 4 week intervals or longer if severe myelosuppression occurred. Twenty patients received CMC5 and 42 patients CMC3. Within the analyzed group an overall response (OR) rate (CR+PR) of 64.5% (95% CI: 52.7-76.3%) was reported, including 29.0% CR. There was no difference in the CR rate between the patients treated with CMC5 (30%) and CMC3 (28.6%) (P = 0.9), nor in the OR rate (55.0% and 69.0%, respectively, P = 0.3). Residual disease was identified in seven out of 18 (38.9%) patients who were in CR, including two treated with CMC5 and five treated with CMC3 protocols. CMC-induced grade III or IV thrombocytopenia occurred in 12 (19.4%) of patients, including four (20%) CMC5-treated and eight (19%) CMC3-treated patients (P= 0.8). Neutropenia grade III or IV was observed in seven (35%) and 11 (26.2%) patients, respectively (P = 0.8). Severe infections, including pneumonia and sepsis, occurred more frequently after CMC5 (11 patients, 55.0%) than CMC3 (10 patients, 28.6%) (P = 0.03) Fourteen patients died, including six treated with CMC5 and eight treated with CMC3 (30% and 19%, respectively). Infections were the cause of death in nine patients, including four in the CMC5 group and five in the CMC3 group. In conclusion, our results indicate that the CMC programme is an active combined regimen in previously untreated B-CLL patients; its efficiency seems to be similar to that observed earlier in B-CLL patients treated with 2-CdA as a single agent. However, toxicity, especially after CMC5 administration, is significant. Therefore, we recommend the CMC3 but not the CMC5 programme for further evaluation.

Richter's syndrome following cladribine therapy for chronic lymphocytic leukemia first manifested as pathologic fracture of the femur

Richter's syndrome (RS) refers to the development of aggressive non-Hodgkin's lymphoma (NHL) during the course of chronic lymphocytic leukaemia (CCL). It occurs in approximately 3% of patients with CLL. The isolated form of this complication in bone is extremely rare and, so far, has not been described in a patient treated with cladribine (2-CdA). We report a case of CLL treated successfully with 2-CdA, where isolated diffuse large B-cell lymphoma (LBCL) developed 2 years after the diagnosis of CLL Rai II and one year after the completion of 2-CdA treatment. RS was first manifested as a pathologic fracture of the left femur. The LBCL was clonally distinct from the original CLL cells. The patient was successfully treated with CHOP and radiotherapy and obtained complete response of the LBCL.

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 with prednisone versus chlorambucil with prednisone as first-line therapy in chronic lymphocytic leukemia: report of a prospective, randomized, multicenter trial

The efficacy and toxicity of cladribine (2-CdA) + prednisone (P) versus chlorambucil (Chl) + P were compared in previously untreated patients with progressive or symptomatic chronic lymphocytic leukemia (CLL) in a randomized, multicenter prospective trial. Eligible patients were assigned to either 2-CdA 0.12 mg/kg per day in 2-hour infusions and P 30 mg/m(2) per day for 5 consecutive days or Chl 12 mg/m(2) per day and P 30 mg/m(2) per day for 7 consecutive days. Three courses were administered at 28-day intervals or longer if myelosuppression developed. The therapy was finished if complete response (CR) was achieved. Of 229 available patients 126 received 2-CdA+P and 103 received Chl+P as a first-line treatment. CR and overall response rates were significantly higher in the patients treated with 2-CdA+P (47% and 87%, respectively) than in the patients treated with Chl+P (12% and 57%, respectively) (P = .001). Progression-free survival was significantly longer in the 2-CdA-treated group (P = .01), but event-free survival was not statistically different. Thirteen percent of patients were refractory to 2-CdA+P and 43% to Chl+P (P = .001). Drug-induced neutropenia was more frequently observed during 2-CdA+P (23%) than Chl+P therapy (11%) (P = .02), but thrombocytopenia occurred with similar frequency in both groups (36% and 27%, respectively). Infections were seen more frequently in the 2-CdA+P-treated group (56%) than in the Chl+P-treated group (40%; P = .02). Death rates have so far been similar in patients treated with 2-CdA (20%) and with Chl (17%). The probability of overall survival calculated from Kaplan-Meier curves at 24 months was also similar for both groups (78% and 82%, respectively). (Blood. 2000;96:2723-2729)

Cladribine with or without prednisone in the treatment of previously treated and untreated B-cell chronic lymphocytic leukaemia - updated results of the multicentre study of 378 patients

Between January 1992 and January 1999, we treated 378 B-chronic lymphocytic leukaemia (CLL) patients with cladribine (2-CdA), and 255 of the patients were also treated with prednisone. A total of 194 patients were previously untreated, and 184 had relapsed or refractory disease after previous other therapy. Complete response (CR) was obtained in 111 (29.4%) and partial response (PR) in 138 (36.5%) patients, giving an overall response (OR) rate of 65.9%. CR and OR were achieved more frequently in patients in whom 2-CdA was a first-line treatment (45.4% and 82.5% respectively) than in the pretreated group (12.5% and 48.4% respectively) (P < 0.0001). The median duration of OR for previously untreated patients was 14.7 months and for pretreated patients 13.5 months (P = 0.09). The median survival evaluated from the beginning of 2-CdA treatment was shorter in the pretreated group (16.3 months) than in the untreated group (19.4 months) (P < 0.0001). A total of 117 (63.9%) patients died in the pretreated group and 63 (32.6%) in the untreated group. In pretreated patients, 2-CdA + prednisone (P) and 2-CdA alone resulted in similar OR (51.0% and 45.0% respectively; P = 0.4). In contrast, in untreated patients, 2-CdA + P produced a higher OR (85.4%) than 2-CdA alone (72.1%) (P = 0.04). Infections and fever of unknown origin, observed in 91 (49.4%) pretreated and 74 (38.1%) untreated patients (P = 0.03), were the most frequent toxic effects. Our results indicate that 2-CdA is an effective, relatively well-tolerated drug, especially in previously untreated CLL.

Atypical chronic myelogenous leukemia following immunosuppressive therapy for severe aplastic anemia

Late clonal complications of aplastic anemia (AA) such as acute leukemia, myelodysplastic syndromes or paroxysmal nocturnal hemoglobinuria have been recognized for a long time. To our knowledge, chronic myelogenous leukemia (CML) as a late complication of severe aplastic anemia has as yet not been reported. We report here a case of AA treated successfully with antilymphocytic globulin and cyclosporin in whom Ph1 negative, BCR/ABL negative CML developed 8 years after diagnosis of AA. This case of atypical, secondary CML was refractory to treatment with interferon alpha and hydroxyurea.

Intermittent 2-hour intravenous infusions of 2-chlorodeoxyadenosine in the treatment of 110 patients with refractory or previously untreated B-cell chronic lymphocytic leukemia

The purpose of our study was to determine the effectiveness of 2-CdA in 2-hour intravenous infusions in the treatment of B-CLL. One hundred and ten patients with B-CLL received 1 to 10 courses of 2-CdA (median 2.5) at a dosage of 0.12 mg/kg daily for 5 consecutive days. Eighteen of them were untreated and 92 relapsed or became refractory to previous therapeutic modalities. Complete remission (CR) was achieved in 8 (7.3%) and partial remission (PR) in 35 patients (31.8%) giving an overall response rate of 39.1%. In 3 patients, cross-resistance to fludarabine was noticed. Toxic effects of 2-CdA were more frequently observed in previously treated patients. Hemorrhagic complications due to drug-induced thrombocytopenia were noticed in 25 (22.7%) and severe infections including sepsis in 14 (12.7%) patients.

[Heart valve prosthesis, anticoagulants and pregnancy]

Patients with artificial valve prostheses require lifelong anticoagulation treatment. The risk of thrombotic complications increases greatly in pregnancy. Anticoagulant treatment in pregnant women with artificial heart valve prostheses in one of the most controversial problems in medical practice as anticoagulants which are beneficial and safe for the mother may by hazardous for the fetus. Recommended procedure is to administer heparin subcutaneously at last during the first 14 weeks and the last 2 weeks of gestation and coumarin derivates throughout the second and third trimesters. In asymptomatic or mildly symptomatic women who are willing to follow a strict regimen of antithrombotic prophylaxis in pregnancy the risk is not associated with an increased morbidity or mortality in the mother or fetus. Hence, recommendations against pregnancy in women with artificial heart valves are not always justified.