Potent toxicity of 2-chlorodeoxyadenosine toward human monocytes in vitro and in vivo. A novel approach to immunosuppressive therapy.

Lymphoid cells were thought to be uniquely susceptible to excess 2'-deoxyadenosine (dAdo), when exposed to inhibitors of adenosine deaminase (ADA). However, we now find that human monocytes are as sensitive as lymphocytes to dAdo or to the ADA-resistant congener 2-chloro-2'-deoxyadenosine (CldAdo). Monocytes exposed in vitro to CldAdo, or to dAdo plus deoxycoformycin rapidly developed DNA strand breaks. Both the DNA damage and the toxicity of CldAdo or dAdo toward monocytes were blocked by deoxycytidine, but not by inhibitors of poly(ADP-ribose) polymerase. A partial decrease in RNA synthesis and a gradual decline of cellular NAD were early biochemical events associated with monocyte DNA damage. Low CldAdo concentrations (5-20 nM) inhibited monocyte phagocytosis and reduced the release of interleukin 6. Higher CldAdo concentrations led to a dose- and time-dependent loss of monocyte viability. Circulating monocytes disappeared within 1 wk in patients with cutaneous T cell lymphoma or with rheumatoid arthritis during continuous CldAdo infusion. The marked sensitivity of human monocyte function and survival to CldAdo in vitro, together with the monocyte depletion in patients receiving CldAdo chemotherapy, suggests that CldAdo or other dAdo analogues offer a novel therapeutic strategy for chronic inflammatory and autoimmune diseases characterized by inappropriate monocyte deployment or function.

2-Chlorodeoxyadenosine activity in patients with untreated chronic lymphocytic leukemia.

PURPOSE: 2-chlorodeoxyadenosine (2-CdA; cladribine) is a purine analog with activity in patients with chronic lymphocytic leukemia (CLL) who fail to respond to alkylator therapy. We conducted a phase II trial of 2-CdA in previously untreated CLL patients. PATIENTS AND METHODS: 2-CdA was administered to 20 patients with previously untreated CLL as a 0.1-mg/kg/d 7-day continuous intravenous infusion every 28 to 35 days until maximum response or prohibitive toxicity. RESULTS: A median of four courses (range, one to nine) was administered to each patient. Five patients (25%) achieved a complete response and 12 (60%) achieved a partial response, for an overall response rate of 85%. The median response follow-up duration was 8+ months (range, 3 to 27). Myelosuppression was the principal toxicity. Four of 20 patients (20%) experienced grade III or IV thrombocytopenia. Three patients, all of whom received corticosteroid therapy, developed opportunistic infections at a median of 19 months following discontinuation of 2-CdA therapy. CONCLUSION: 2-CdA has major activity in patients with previously untreated CLL, and the lower response rates seen in previously treated patients may be due in part to poor marrow reserve from prior therapy. Determination of the relative effectiveness of 2-CdA, fludarabine, and chlorambucil in the treatment of CLL patients will require a randomized trial.

Pharmacokinetic study of oral and bolus intravenous 2-chlorodeoxyadenosine in patients with malignancy.

PURPOSE: This study was designed to evaluate the absolute bioavailability (F value) of 2-chlorodeoxyadenosine (cladribine; 2-CdA) after multiple oral administrations, and the intersubject variability after oral and 2-hour intravenous (IV) administration schedules in patients with malignancy. PATIENTS AND METHODS: Patients with advanced malignancies were eligible. There were two treatment cycles; during cycle 1, patients received 2-CdA solution at 0.28 mg/kg/d orally under fasting conditions for 5 consecutive days concomitantly with omeprazole, and 4 weeks later during cycle 2 patients received 2-CdA as a 2-hour IV infusion of 0.14 mg/kg/d for 5 consecutive days. Serial blood samples for 2-CdA plasma levels were obtained after drug administrations on days 1 and 5 during each treatment cycle. RESULTS: Ten patients completed cycles 1 and 2. The F value of oral 2-CdA measured on days 1 and 5 was 37.2% and 36.7%, respectively. For both oral and IV multiple administrations, there was no significant accumulation in maximum concentration (Cmax), and the intersubject variabilities (coefficient of variation [CV], approximately 40%) in Cmax and area under the concentration-time curve from 0 to 24 hours [AUC(0-24)] values were comparable for both routes on days 1 and 5. A three-compartment open model was applied to the plasma concentration data after oral and IV administrations and resulted in good agreement between observed and simulated concentration-time profiles. Neutropenia was the principal adverse event observed when 2-CdA was administered orally and IV. CONCLUSION: The F value of 2-CdA after oral administration was approximately 37% and there were no cumulative differences in bioavailability observed on multiple dosing of the drug. The absorption and disposition characteristics of oral 2-CdA were linear and predictable with this dosing regimen.

Outpatient high-dose chemotherapy with autologous stem-cell rescue for hematologic and nonhematologic malignancies.

PURPOSE: A prospective study to determine the feasibility of high-dose chemotherapy (HDC) and autologous stem-cell rescue (ASCR) in the outpatient setting. METHODS: One hundred thirteen consecutive patients underwent 165 cycles of HDC/ASCR for a variety of malignancies. HDC regimens were disease-specific. Initially, patients were hospitalized for HDC, discharged on completion, and maintained as outpatients unless toxicities required rehospitalization (subtotal outpatient transplantation [STOT]). Once this was established as safe, a total outpatient transplant (TOT) program was developed in which patients received all of the HDC, as well as supportive care, as outpatients. Patients who declined the outpatient programs received the same HDC and supportive care as inpatients. RESULTS: In 140 of 165 (85%) HDC cycles, patients agreed to participate in one of the outpatient transplant programs. Five patients in the STOT program could not be discharged from the hospital because of toxicities that developed during HDC; thus, 135 patients were monitored the outpatient setting, 95 (70%) of whom were never readmitted. The mean +/- SEM total hospital length of stay (LOS), including all readmissions and excess days after chemotherapy, was 18.33 +/- 5.06 days for patients who refused the outpatient program, 8.22 +/- 5.76 days for patients in the STOT program, and 2.81 +/- 7.66 days for those in the TOT program (P < .001). One treatment-related death occurred in each treatment setting: day 120 inpatient, day 17 STOT, and day 110 TOT. CONCLUSION: Outpatient management of HDC/ASCR is safe and acceptable for the vast majority of patients. The STOT program resulted in significant reduction in hospital LOS, while the TOT program appears equally safe and further reduces LOS. Hospitalization for HDC/ASCR is unnecessary in most patients.

2-Chlorodeoxyadenosine dose escalation in nonhematologic malignancies.

PURPOSE: We performed a dose-escalation study of 2-chlorodeoxyadenosine (2-CdA) in solid tumors to determine the maximum-tolerated dose (MTD) and define its toxicity profile at higher doses. PATIENTS AND METHODS: Twenty-one patients, seven with malignant astrocytoma, twelve with metastatic melanoma, and two with metastatic hypernephroma, were enrolled onto the study. Patients were entered onto cohorts that received 0.10, 0.15, or 0.20 mg/kg/d of 2-CdA by continuous intravenous infusion for 7 days every 28 days. 2-CdA levels were determined by radioimmunoassay. In tumor tissue samples, deoxycytidine kinase (dCK) levels were measured by both enzyme activity and immunoreactive protein analysis. RESULTS: Of seven patients treated with 2-CdA at 0.1 mg/kg/d, one experienced grade 3 or 4 myelotoxicity. Of 11 patients treated at 0.15 mg/kg/d, four experienced myelotoxicity, two after a single course of 2-CdA. All three patients who received 2-CdA at 0.2 mg/kg/d experienced myelosuppression. Neurologic events occurred in two patients, both with malignant melanoma. Two of seven patients (28.6%) with astrocytomas obtained partial responses with a median duration of 8 months. 2-CdA penetrated the blood-brain barrier. An association was found between dCK levels as measured by enzymatic activity and immunoreactive proteins, but this did not correlate with 2-CdA tumor responsiveness. CONCLUSION: The MTD for 2-CdA delivered as a 7-day intravenous infusion in patients with nonhematologic malignancies was determined to be 0.1 mg/kg/d, the same as the MTD for patients with hematologic malignancies. There was no clinical correlation with dCK expression and response to 2-CdA. The responses noted in patients with malignant astrocytoma warrant further phase II study.

2-Chlorodeoxyadenosine treatment of low-grade lymphomas.

PURPOSE: Because of the need to identify effective new agents in the treatment of non-Hodgkin's lymphoma and because of the high activity of the purine analog 2-chlorodeoxyadenosine (2-CdA) against chronic lymphocytic leukemia and hairy cell leukemia, a phase II trial of 2-CdA was initiated in patients with low-grade lymphocytic lymphomas. PATIENTS AND METHODS: Forty patients with low-grade lymphocytic lymphomas including diffuse small lymphocytic, follicular small-cleaved, and follicular mixed histologies were enrolled onto the study. Conventional therapies had failed in all patients, and six patients had lymph node biopsies showing evidence of histologic evolution to a higher-grade lymphoma. A total of 107 courses of 2-CdA were administered. There were 27 males and 13 females. The median age was 59 years (range, 37 to 80 years). Patients had received a median of three prior therapies (range, one to six therapies). RESULTS: An overall response rate of 43% was achieved, with eight patients experiencing complete responses (CRs) and nine patients experiencing partial responses (PRs). The duration of responses ranged from 1 to greater than 33 months without maintenance therapy (median duration of response, 5 months). Histology and prior therapy history did not seem to correlate with responses. Significant toxicity was limited to bone marrow suppression; 18% of patients developed neutropenia, and 30% developed thrombocytopenia. CONCLUSIONS: This phase II trial demonstrates that 2-CdA is an effective antilymphocyte, antineoplastic agent with significant activity as a single agent in patients with recurrent or refractory low-grade lymphocytic lymphoma. Responses were achieved with an acceptable toxicity profile. Further trials of this agent in previously untreated patients and in combination regimens are indicated and will be developed.

Normal cortical bone mass in patients after long term coumadin therapy.

Clinical delineation of the warfarin embryopathy and the recent discovery of osteocalcin (a vitamin K-dependent bone protein) suggest that coumadin therapy could adversely affect the skeleton. Using bone densitometry and metacarpal cortical width measurement, we found normal cortical bone mass in 17 adults receiving long term coumadin therapy.

The optimal management of hairy cell leukaemia.

Hairy cell leukaemia is an uncommon B cell chronic lymphoproliferative disorder characterised by circulating lymphocytes displaying prominent cytoplasmic projections. Therapy is initiated for severe cytopenias or recurrent infections. Splenectomy, the first standard treatment, is now less commonly used as primary treatment. Interferon-alpha (IFN alpha) induces partial responses in most patients but complete responses in only a few. Adverse effects from IFN alpha are common but not life-threatening. The ability of two newer purine analogues, pentostatin (2'-deoxycoformycin) and cladribine (2-chlorodeoxyadenosine), to induce long-lasting complete remissions in the majority of patients has revolutionised the treatment of this disease. Cladribine is emerging as the treatment of choice because of its favourable toxicity profile, brief duration of treatment, high percentage of unmaintained complete remissions and low incidence of relapse.

Prolonged, complete remission after 2-chlorodeoxyadenosine therapy in a patient with refractory essential mixed cryoglobulinemia.

Essential mixed cryoglobulinemia is a systemic disorder in which cutaneous vasculitis and frequently glomerulonephritis are associated with cryoprecipitable serum immune complexes. Typically, the treatment regimen consists of plasmapheresis, high-dose corticosteroids, and cytotoxic chemotherapy, as well as interferon alfa for hepatitis C virus-related cryoglobulinemia. Herein we describe a man with progressive, symptomatic cryoglobulinemia and multisystem organ dysfunction in whom corticosteroid and alkylating therapy failed; however, he had a complete and long-lasting remission after administration of 2-chlorodeoxyadenosine (cladribine).

Reduced charges and costs associated with outpatient autologous stem cell transplantation.

High-dose chemotherapy and stem cell rescue is increasingly being delivered in the outpatient setting. Such intensive outpatient management programs have reduced the total hospital length of stay without compromising clinical outcomes. However, a detailed financial analysis of outpatient programs has not been performed. These data are the results of a prospective study of 94 patients receiving high-dose chemotherapy and autologous peripheral blood stem cell transplant in one of three settings: traditional inpatient, partial outpatient, total outpatient. Patients were allowed to choose their own treatment setting based upon the availability of a caregiver and personal preference. Total hospital length of stay and the actual cost and charges for each patient were monitored prospectively. The patients in the three groups were well balanced with regard to age and functional status prior to high-dose chemotherapy. The average length of stay was reduced from 17.3 to 8.2 to 2.7 days in the three different treatment settings (P < 0.01). Mean procedure costs were reduced from $39.7 thousand (US dollars) to $36.2 thousand to $29.4 thousand in the three treatment settings (P < 0.029). No differences in toxicity or overall response to therapy was noted. High-dose chemotherapy and stem cell rescue can be safely administered in the outpatient setting and results in significant cost savings.

Identification of monoclonal immunoglobulins and quantitative immunoglobulin abnormalities in hairy cell leukemia and chronic lymphocytic leukemia.

Serum and urine samples from 161 cases of hairy cell leukemia (HCL) and 50 cases of chronic lymphocytic leukemia (CLL) were analyzed for monoclonal immunoglobulin (MIg) by using a combination of high-resolution protein electrophoresis, immunoelectrophoresis, and immunofixation. Quantitative immunoglobulin analysis also was performed on all serum samples. Monoclonal immunoglobulin, usually of low intensity, was identified in serum or urine in 26 (16.1%) cases of HCL compared with 27 (54%) cases of CLL. Forty-eight (29.8%) cases of HCL had an increase in one or more immunoglobulins; increases in IgG were the most frequent. In CLL, 48 (96.0%) cases had a decrease in one or more immunoglobulins, with decreases in IgG, IgA, and IgM in 76%, 68%, and 56% of the cases, respectively. The correlation between serum or urine monoclonal immunoglobulin light chain and the surface membrane light chain was 88% in CLL compared with 47.4% in HCL. These findings confirm previous observations of frequent polyclonal hyper-gamma-globulinemia in HCL, hypo-gamma-globulinemia in CLL, and weak monoclonal immunoglobulins in both disorders. The contrasting immunoglobulin abnormalities in HCL and CLL indicate distinctive biologic differences in these chronic B-cell leukemias.

Purine metabolism of lymphocytes. Targets for chemotherapy drug development.

The unique metabolic profile that renders lymphoid cells sensitive to purine deoxynucleosides also accounts for the response of chronic lymphoid malignancies to purine analogues. Consistent with earlier observations in children with adenosine deaminase deficiency, a profound and relatively selective lymphocyte depletion results from treatment with drugs that elevate or mimic deoxyadenosine. Three such agents available for clinical use are 2-chlorodeoxyadenosine, 2'-deoxycoformycin, and fludarabine phosphate. In addition to a review of the relevant biochemistry and cellular pharmacology of these agents in target lymphoid cells, this article reviews the current clinical response data in leukemias and lymphoma.

2-Chlorodeoxyadenosine in the treatment of hairy cell leukemia and chronic lymphocytic leukemia.

More than 450 patients with hairy cell leukemia have been treated at the Scripps Clinic. Of 144 patients followed for a median of 14.2 months (range, 8.1-70 months), 123 (85%) obtained complete responses, 17 (12%) partial responses, 3 (2%) did not respond, and 1 patient was unevaluable. So far, 4 patients have relapsed at a median of 36 months (range, 12-48 months). Fever was the principal toxicity occurring in 43% of patients. Five patients resistant (3 patients) or intolerant (2 patients) to deoxycoformycin were also treated. Of these 5 patients, 4 obtained complete responses, including 2 patients resistant to deoxycoformycin, and 1 patient a partial response, suggesting a possible lack of cross-resistance between deoxycoformycin and 2-CdA in hairy cell leukemia. Other single-institution studies have documented similar response rates and toxicities. Ninety patients with advanced chronic lymphocytic leukemia were treated with 2-CdA administered either as a 0.1 mg/kg/day 7-day continuous intravenous infusion or as a 0.028-0.14 mg/kg/day 2-hour bolus for 5 consecutive days. Four patients (4%) obtained complete responses and 36 patients (40%) partial responses, using NCI-sponsored Working Group guidelines. Of the 50 patients who were non-responders, 27 (54%) had a > or = 50% sustained reduction in the absolute lymphocyte count. The ratio of deoxycytidine kinase to cytoplasmic 5'-nucleotidase was predictive of 2-CdA responsiveness. Fourteen patients with fludarabine-failed chronic lymphocytic leukemia were also treated. No responses were achieved and 2 patients had progressive disease. Six patients had a > or = 50% reduction in the absolute lymphocyte count.(ABSTRACT TRUNCATED AT 250 WORDS)

The Scripps Clinic experience with 2-chlorodeoxyadenosine in the treatment of hairy cell leukemia.

Follow-up data is now available on 144 patients with hairy cell leukemia treated with 2-chlorodeoxyadenosine (2-CdA) at the Scripps Clinic. Of 144 patients followed for a median of 14.2 months, 123 (85%) obtained complete responses, 17 (12%) partial responses, 3 (2%) did not respond and 1 patients was unevaluable. So far, only 4 patients have relapsed at a median of 36 months. Fever was the major toxicity occurring in 43% of patients. Five patients resistant (3 patients) or intolerant (2 patients) to 2'-deoxycoformycin were also treated. Of these 5 patients, 4 obtained complete responses, including 2 patients resistant to 2'-deoxycoformycin, and 1 patient a partial response, suggesting a possible lack of cross-resistance between 2'-deoxycoformycin and 2-CdA in hairy-cell leukemia. More than 200 patients have been treated with 2-CdA worldwide with 82% obtaining complete remission and 12% partial remissions. Serial peripheral blood immunophenotypic analyses have documented the absence of circulating hairy cells. When bone marrow biopsies were examined using sensitive immunohistochemical staining techniques, residual hairy cells were detected in 25-50% of morphologic complete responders. Patients will need to be observed longitudinally to determine if this staining is predictive of relapse. A double-blind, placebo-controlled study of pentoxifylline, a modulator of tumor necrosis factor-alpha and other cytokines, was performed in 2-CdA-treated hairy cell leukemia patients to determine whether the incidence of neutropenic fever would be reduced. Although pentoxifylline resulted in less febrile, hospital and antibiotic therapy days than placebo, only the number of days in the hospitalized patients achieved statistical significance. 2-CdA is emerging as the treatment of choice for hairy cell leukemia given the high percentage of long-lasting, complete responses that follow a single course of therapy.

2-chlorodeoxyadenosine administration to patients with the myeloid blast phase of chronic myelogenous leukemia.

Three patients with chronic myelogenous leukemia (CML) in myeloid blast phase received 2-chlorodeoxyadenosine (2-CdA) at 0.7 mg/kg per course over 5 days every 2-4 weeks for 7, 2 and 5 courses. Each patient had a decrement in their white blood cell count, and in the absolute number and percentage of circulating immature cells following 2-CdA administration. Two patients achieved hematologic responses of 14 and 3 months and survived 19 and 6 months, respectively, while the non-responder died 2 months later. 2-CdA-induced anemia and thrombocytopenia, generally mild and reversible, were observed in all patients. Given the dismal results and considerable toxicities that follow multiagent induction chemotherapy for CML in myeloid blast phase, 2-CdA therapy may represent a reasonable therapeutic alternative, although confirmation is required in larger numbers of patients.

2-Chlorodeoxyadenosine Treatment of Refractory Chronic Lymphocytic Leukemia.

Ninety patients with advanced refractory chronic lymphocytic leukemia (CLL) were treated with 2-chlorodeoxyadenosine (2-CdA) administered either as a 0.1 mg/kg/day 7-day continuous intravenous infusion or as a 0.028 mg to 0.14 mg/kg/day 2-hour bolus for 5 consecutive days. One patient had stage A disease, seven patients had stage B disease, and 82 patients had stage C disease. Twenty-seven patients were female and 63 were male, with an age range of 40 to 84 years, median 63 years. All patients had received prior therapy and failed, with a range of one to four and a median of two prior therapies. Six patients had previously failed fludarabine therapy. Four patients (4%) experienced complete remissions, and 40 patients (40%) experienced partial remissions, yielding an over all response rate of 44%. The median duration of response was four months, with a range of two to 30 months. Of 50 patients who were non-responders, 27 (54%) had a greater than 50% sustained reduction in the absolute lymphocyte count despite insufficient improvement in hemoglobin concentration or platelet count to achieve a response status. Therapy was well tolerated with myelosuppression being the principal toxicity. Twenty-two patients (24%) experienced thrombocytopenia and 16 patients (18%) had documented infections. We confirm our early pilot results with 2-CdA demonstrating in a large group of patients that 2-CdA achieves a significant response rate with two different drug administration schemes in failed CLL patients. Responses are achieved with acceptable toxicity. 2-CdA merits further evaluation in previously untreated patients and in combination regimens for failed patients.

New perspectives on the approach to chronic lymphocytic leukemia.

Investigation of the biological actions of loxoribine in chronic lymphocytic leukemia (CLL) was undertaken because of the pervasive immunostimulatory effects of the nucleoside on normal B cells. In vitro studies with cells from a spectrum of CLL patients demonstrate that loxoribine induces B-CLL cells to enter and traverse the cell cycle. This is reflected by marked increases in DNA synthesis, by standard morphological criteria, and by flow cytometric evaluation of cell cycle status and of cell surface activation markers. Cells from about 75% of patients studied evince this response. Analysis of a variety of biological parameters indicate that only the ratio of T cells (CD4+ or CD8+) to B-CLL cells correlates with induction and degree of proliferative response. Co-stimulation with loxoribine and IL-2 results in modest proliferative synergy, presumably due to upregulation of IL-2R alpha expression on B-CLL cells by loxoribine. Prolonged exposure of B-CLL cells to stimulatory concentrations of loxoribine frequently culminates in progression of the responsive cells to apoptosis. The capacity of loxoribine to transiently approximate the reversible transformation of a low grade B cell malignancy to one of a higher grade presents the opportunity for evaluation of cycle-active drugs under these conditions. Recent studies indicate that pre-treatment of B-CLL cells with loxoribine results in synergistic killing of leukemic cells with cycle-active drugs. The ability to induce B-CLL cells into cell cycle entry and/or into either activation-induced apoptosis or into phases of the cell cycle sensitive to cytotoxic therapy opens up new perspectives for the development of potentially curative strategies for this chronic leukemia.

2-Chlorodeoxyadenosine (2-CdA): A Potent Chemotherapeutic and Immunosuppressive Nucleoside.

Hereditary adenosine deaminase deficiency results in failure of the lymphocyte development. This occurs because of the accumulation of deoxyadenine nucleotides in cells with high deoxycytidine kinase and low 5'-nucleotidase activity. 2-Chlorodeoxyadenosine (2-CdA) resists the action of adenosine deaminase and accumulates in cells with high deoxycytidine kinase and low 5'-nucleotidase activity. It is equally toxic to dividing and nondividing cells and may act by preventing repair of DNA single-strand breaks. In doses of 0.1 mg/kg/day given for seven days 2-CdA manifests low toxicity. It has been found to be effective in the treatment of patients with lymphoid neoplasms, including advanced cutaneous T-cell lymphomas, chronic lymphocytic leukemia, non-Hodgkin lymphomas, and hairy cell leukemia. In the latter disorder it appears to be as or more effective than the tight-binding adenosine deaminase inhibitor, deoxycoformycin, and is probably less toxic. 2-CdA also appears to be effective in controlling autoimmune hemolytic anemia and shows promise in the treatment of other autoimmune diseases.

Profound toxicity of deoxyadenosine and 2-chlorodeoxyadenosine toward human monocytes in vitro and in vivo.

Deoxyadenosine is known to be toxic to both proliferating and resting lymphocytes that lack adenosine deaminase (ADA) activity. We now show that human monocytes are also highly sensitive in vitro to nanomolar concentrations of deoxyadenosine plus the ADA inhibitor deoxycoformycin, and to the ADA-resistant analogue 2-chlorodeoxyadenosine (CdA). Monocytes exposed to deoxyadenosine or to CdA in vitro accumulate massive DNA damage detectable within 1 hour. The DNA damage in monocytes exposed to CdA is associated with a decrease in protein synthesis and with inhibitions of phagocytosis and IL-6 secretion. However, unlike lymphocytes with similar DNA damage, the monocytes show no significant NAD or ATP depletion until cell viability declines. The selective toxicity of CdA to monocytes was confirmed by in vivo studies. In almost all patients receiving CdA infusion chemotherapy for cutaneous lymphoma, the blood monocytes counts fell to near 0 during one week of therapy. Our results suggest that CdA and related compounds may have potential clinical use in the therapy of immune disorders associated with monocyte/macrophage activation.