Efficacy of 2'-deoxycoformycin in hairy-cell leukemia: a study of the National Cancer Institute of Canada Clinical Trials Group.

Thirty-one patients with hairy-cell leukemia were treated with 2'-deoxycoformycin (DCF) in a National Cancer Institute of Canada multicenter trial. The DCF was administered in a cycle (4 mg/m2 iv weekly X 3), which was repeated every 8 weeks. Following a complete remission, consolidation was done with two further cycles of DCF. Of 28 patients evaluable for response, 25 obtained a complete remission; 3 had a partial response. To date there has been only one relapse; the median time with no therapy was 429.5 days (range 99-743 days). Toxicity was moderate and included nausea and vomiting, lethargy, and skin rash; with the first cycle of treatment, neutropenia and an increased incidence of fever or infection were also observed. We conclude that low-dose DCF is highly effective in treating hairy-cell leukemia.

Pentostatin in hairy cell leukemia: treatment by the special exception mechanism.

An analysis of the clinical outcomes in 66 patients with hairy cell leukemia treated with pentostatin under the Special Exception mechanism of the Division of Cancer Treatment, National Cancer Institute, between 1983 and 1987 has revealed a favorable balance of risk and benefit. Hematologic parameters and performance status were improved in most patients treated outside the clinical trials mechanism. The treating physicians considered 37 patients (56%) to be complete responders and 15 patients (23%) to be partial responders. Four patients (6%) died while receiving pentostatin. Life-threatening leukopenia (wbc count, less than 1,000/mm3) was reported in 24% of patients, and severe or life-threatening infection occurred in 11%. The experience gained with these patients supplements the information presently being collected from the controlled clinical trials and supports the development of a group C treatment protocol.

Levels of 2'-deoxycoformycin, adenosine, and deoxyadenosine in patients with acute lymphoblastic leukemia.

2'-Deoxycoformycin (dCF), a potent inhibitor of adenosine deaminase, has recently undergone Phase I clinical trials and has been found to be therapeutically active in acute lymphoblastic leukemia. In this report, levels of dCF in plasma, plasma concentrations of adenosine and deoxyadenosine, and urine levels of deoxyadenosine were measured in leukemic patients undergoing treatment with dCF during a Phase I clinical trial. dCF was administered i.v. at a dose of 0.25 to 1.0 mg/kg (7.5 to 30 mg/sq m) for 3 consecutive days. Plasma drug levels of 2 to 6 microM were observed following the third dose of dCF, and drug accumulation occurred only at the 1-mg/kg dosage. In this limited series of patients, the plasma concentrations of adenosine and deoxyadenosine and the urine concentrations of deoxyadenosine did not show an obvious correlation with dCF dose, therapeutic response, or toxicity.

Phase I study of 2'-deoxycoformycin in acute lymphoblastic leukemia.

2'-Deoxycoformycin (2'-dCF), a tight-binding inhibitor of adenosine deaminase, was administered to 26 pediatric patients with acute lymphoblastic leukemia in a Phase I study. Doses ranged from 0.25 to 1.0 mg/kg given i.v. for 3 consecutive days. Common toxicity included nausea, vomiting, diarrhea, hepatocellular enzyme elevations, and conjunctivitis. Lymphopenia occurred in all patients. The most serious adverse effects were acute tubular necrosis and central nervous system toxicity, which appeared to be dose related. In addition, two patients given the 0.75-mg/kg dose developed severe hepatic toxicity, although this could not be ascribed definitively to 2'-dCF. Antitumor activity was observed in eight patients, two of whom experienced a complete remission. Inhibition of lymphoblast adenosine deaminase activity was noted in the majority of cases and was observed at all doses. Antileukemic activity occurred at doses of 2'-dCF which were not associated with limiting toxicities. These results suggest that 2'-dCF is active against acute lymphoblastic leukemia and that a starting dose of 0.5 mg/kg/day be utilized in Phase II studies.

Dipyridamole enhancement of toxicity to L1210 cells by deoxyadenosine and deoxycoformycin combinations in vitro.

The combination of 2'-deoxyadenosine and deoxycoformycin is known to be markedly toxic to T-lymphocyte cell lines relative to B-cell lines, and this difference appears to be related to the capacity of the cells to accumulate deoxyadenosine triphosphate (dATP). In the presence of dipyridamole and 2'-deoxyadenosine and when adenosine deaminase was inhibited with deoxycoformycin, the L1210 leukemia cell which is a non-T-, non-B-cell type accumulated dATP like a T-cell type. The intracellular L1210 concentration of dATP using the triple combination (1.1 microM deoxycoformycin-40 microM deoxyadenosine-10 microM dipyridamole) reached 400 microM at which concentration ribonucleotide reductase specific activity was reduced by 80%. While this degree of enzyme may be significant, complete inhibition might have been expected, since 400 microM dATP is approximately 40 times the concentration to give 50% inhibition in some purified systems.

Resistance to 9-beta-D-arabinofuranosyladenine in cultured leukemia L 1210 cells.

A cultured line of L1210 leukemia cells, designated L1210/ara-A, was selected for resistance to 9-beta-D-arabinofuranosyladenine (ara-A) by a series of 72-hr exposures to increasing concentrations of ara-A in the presence of 1 microM deoxycoformycin. Cells of the resistant line were about one-tenth as sensitive as were cells of the parent line to the effects of ara-A on proliferation, viability, and tumorigenicity. Cross-resistance, as determined by comparison of drug effects on rates of proliferation of L1210/C2 and L1210/ara-A cells, was seen with adenosine, deoxyadenosine, methylmercaptopurine ribonucleoside, tubercidin, and cordycepin but not with 1-beta-D-arabinofuranosylcytosine or with 9-beta-D-arabinofuranosyl-2-fluoroadenine. The levels of resistance to methylmercaptopurine ribonucleoside, cordycepin, and tubercidin were considerably greater than that seen with ara-A itself. L1210/C2 and L1210/ara-A cells were compared with respect to the effects of ara-A on cell size distributions, DNA distributions, labeling indices, and apparent rates of DNA synthesis, and the differences seen were consistent with inhibition of DNA synthesis and unbalanced growth as the major mechanism of ara-A cytotoxicity. The decreased sensitivity of DNA synthesis in L1210/ara-A cells treated with ara-A, relative to L1210/C2 cells, was due to reduced intracellular accumulation of ara-A phosphates in the resistant line. Phosphorylation of ara-A, adenosine, and tubercidin, but not deoxyadenosine or deoxycytidine, was greatly reduced in intact L1210/ara-A cells, relative to L1210/C2 cells, and adenosine kinase activity in extracts of L1210/ara-A cells was negligible. Resistance to ara-A, and cross-resistance to tubercidin, methylmercaptopurine ribonucleoside, and cordycepin is attributed to loss of adenosine kinase activity.

Clinical pharmacology of 9-beta-D-arabinofuranosyladenine in combination with 2'-deoxycoformycin.

It has been suggested that, by inhibiting the adenosine deaminase (ADA)-mediated catabolism of 9-beta-D-arabinofuranosyladenine (ara-A), 2'-deoxycoformycin (DCF) would increase the half-life (t1/2) of ara-A, a compound with known antileukemic activity. To test this hypothesis, we collected serial plasma samples from five patients with refractory acute lymphoblastic leukemia who participated in a Phase I trial of i.v. DCF 915 mg/sq m) in combination with i.v. single-dose ara-A (120-250 mg/sq m). In four of these patients, of whom three were known to have achieved greater than 98% ADA inhibition, a mean ara-A t1/2 of 227 min was achieved. Extrapolated peak levels (i.e., following infusion of ara-A) ranged from 1.5 to 7.4 micrograms/ml (mean, 4.2 micrograms/ml). Elimination of drug appeared to follow a single-compartment model. In two patients who received ara-A without prior DCF and in a third patient who had significant residual ADA activity despite DCF, ara-A was unmeasurable within 5 min of the end of infusion. These data confirm that the kinetics of ara-A catabolism can be altered by inhibition of ADA and suggest that more than one dose of DCF may be necessary for complete inhibition of the enzyme and optimal pharmacological modulation of ara-A.

Biochemical changes induced in hairy-cell leukemia following treatment with the adenosine deaminase inhibitor 2'-deoxycoformycin.

The adenosine deaminase inhibitor 2'-deoxycoformycin and interferon are highly effective in the treatment of hairy-cell leukemia. In this study, a patient with type 2 hairy-cell leukemia was treated with one cycle of 2'-deoxycoformycin (4 mg/m2, i.v. weekly for 3 weeks), which was repeated at 9 wk. No toxicity was observed, and the hairy cell count fell from 72,000/mm3 to 5,000/mm3 in 3 mo, with a concomitant 50% decrease in the spleen size. The erythrocyte deoxyadenosine triphosphate content increased to 13.6 pmol/10(6) cells following the initial three weekly treatments, but there was no decrease in the adenosine triphosphate pool size and no evidence of hemolysis. The hairy cell adenosine deaminase activity was inhibited by greater than 95% 24 h following the first 2'-deoxycoformycin injection and returned to the pretreatment value at Day 8, although there was a linear decline in peripheral hairy cell count (50%) during this period. No ultrastructural changes were observed in the hairy cells following 2'-deoxycoformycin to suggest lymphocytotoxicity or cellular differentiation. The antitumor activity of 2'-deoxycoformycin could not be attributed to alterations in the hairy cell deoxyadenosine triphosphate/adenosine triphosphate levels or to the induction of DNA strand breaks. Additionally, the plasma levels of interferon did not change during therapy, making it unlikely that 2'-deoxycoformycin exerts its activity by inducing endogenous interferon synthesis.

Alterations in erythrocyte adenine nucleotide pools resulting from 2'-deoxycoformycin therapy.

2'-Deoxycoformycin, a tight-binding adenosine deaminase inhibitor, was administered to 11 adult patients with refractory lymphoproliferative diseases. Total doses ranged from 1.0 to 13.5 mg/kg. Inhibition of lymphoblast adenosine deaminase was obtained in all cases and tumor cytoreduction was noted in eight of ten cases, but no clinically meaningful remissions were obtained. Major toxicities occurred in five patients and included pulmonary edema, renal failure, central nervous system toxicity, hypotension, and death. Toxicity prevented retreatment in several cases in which marked cytoreduction occurred. Deoxyadenosine triphosphate accumulated to a variable extent in the red blood cells of all patients, and a reciprocal decrease in erythrocyte adenosine triphosphate was noted in all cases but one. All patients who suffered major organ toxicity had red blood cell deoxyadenosine triphosphate/adenosine triphosphate ratios greater than 1.3. These data suggest that the degree of replacement of adenosine triphosphate by deoxyadenosine triphosphate in erythrocytes reflects the biochemical milieu which may result in systemic toxicity following treatment with 2'-deoxycoformycin.

Hairy-cell leukemia: induction of complete remission with pentostatin (2'-deoxycoformycin).

Two men with advanced but previously untreated B cell hairy-cell leukemia were treated with low doses of pentostatin (2'-deoxycoformycin) in intermittent courses. There was prompt clearance of hairy cells from the blood, regression of splenomegaly and lymphadenopathy, and correction of anemia, thrombocytopenia, and granulocytopenia. Side effects were tolerable and myelosuppression was not observed. Both patients achieved complete remission documented by bone marrow aspiration and biopsy and radionuclide scans of liver and spleen. They remain in complete remission nine and six months, respectively, after their last treatment. Pentostatin (Warner-Lambert, Ann Arbor, Mich) is highly active in hairy-cell leukemia and merits more extensive evaluation in this disease. A woman with hairy-cell leukemia has begun treatment with pentostatin, and at ten weeks there is disappearance of gross splenomegaly and clearance of hairy cells from the blood. Bone marrow studies have not yet been repeated.

Response to pentostatin in hairy-cell leukemia refractory to interferon-alpha. The European Organization for Research and Treatment of Cancer Leukemia Cooperative Group.

Interferon-alpha (IFN-a) or 2'-deoxycoformycin (pentostatin; DCF) have each been shown to be highly active in hairy-cell leukemia (HCL). In this phase II study of the Leukemia Cooperative Group of the European Organization for Research and Treatment of Cancer (EORTC), the efficacy and toxicity of DCF were investigated in patients who were resistant to IFN-a treatment. Resistance was defined as: (1) progressive disease (PD) under IFN-a therapy for more than 2 months; (2) stable disease (SD) after more than 6 months of IFN-a treatment; (3) relapse within 3 months of discontinuing IFN-a; and (4) intolerance to IFN-a because of World Health Organization (WHO) grade 3 or 4 toxicity. DCF was applied at a dosage of 4 mg/m2 weekly x 3, then 4 mg/m2 every other week x 3. Responders were given a maintenance therapy once per month for a maximum of 6 months. At the time of report, 33 patients with resistant disease were evaluable for response and toxicity. Median duration of IFN-a therapy before DCF administration was 14.7 months (range, 1 to 41 months). Complete remissions (CRs) were achieved in 11 patients and partial remissions (PRs) in 15, resulting in a total response rate of 78.8%. Median interval between beginning of DCF therapy to best response was 3.9 months with a range from 2.0 to 7.0 months. Two patients who achieved PR have relapsed 7 and 14 months after cessation of DCF therapy. The median duration of response was over 11.5 months (range, over 3.0 to over 24.0 months). Three patients died within the first 6 weeks of DCF treatment: one of drug-unrelated cardiomyopathy and two of fungal pneumonia. The patients with early death (n = 3) and nonresponsive disease (n = 4) received IFN-a treatment for a longer period (median, 18.0 months) than did the 26 responsive patients (median, 10.0 months). Major side effects included nausea, skin rash, and infections and were otherwise mild. Thus, DCF is highly active in patients with HCL resistant to IFN-a.

Pentostatin in the treatment of advanced hairy cell leukemia.

2'-Deoxycoformycin (pentostatin [dCF]), a potent inhibitor of adenosine deaminase (ADA), was administered in a biweekly low-dose (2 to 4 mg/m2) intravenous (IV) schedule to patients with advanced hairy cell leukemia. Twenty-three patients were treated, including 12 patients previously treated by splenectomy and five patients treated with interferon. Twenty-one of 23 patients had objective responses, including 20 who achieved a complete remission (CR). Responses occurred rapidly, with an average time to CR of 5.4 months. Treatment was not continued once CR was achieved, and 15 of 20 patients remain in remission with an average duration of 12.6 months. CRs were achieved in both patients previously treated with interferon (three of five) and patients with marked splenomegaly (three of three). Relapses, when seen, have occurred in the bone marrow alone and the one patient who required retreatment was reinduced into CR. Toxicity has been mild and reversible, with nausea and vomiting, conjunctivitis, and skin rash as the main complications of treatment. dCF is the most effective single agent in the treatment of hairy cell leukemia, inducing a high percentage of CRs in all subgroups. Two multiinstitutional trials are now underway to compare its effectiveness v alpha interferon.

Low-dose deoxycoformycin in lymphoid malignancy.

Deoxycoformycin (dCF), a potent inhibitor of adenosine deaminase (ADA), was explored for its antineoplastic potential in 28 patients with advanced lymphoid malignancy. Both normal and malignant B lymphocytes have low levels of ADA activity, and low doses of dCF profoundly inhibit this enzyme in the peripheral blood of patients with chronic lymphocytic leukemia (CLL). The low doses of dCF administered in this trial (4 mg/m2) were not associated with prohibitive toxicity. Five of 28 patients had an objective response. Four additional patients had clinical improvement. No significant difference in the pretreatment ADA activity existed between responding patients and treatment failures. The demonstration of responses to dCF following failure on standard alkylating agents suggests that dCF may not be cross-resistant with current agents used to treat CLL. Additional studies should be pursued using low-dose dCF in patients with advanced malignancy.

Pentostatin in chronic lymphocytic leukemia: a phase II trial of Cancer and Leukemia group B.

We conducted a phase II trial of deoxycoformycin (pentostatin [DCF]) in chronic lymphocytic leukemia (CLL). Eligibility criteria included age greater than 18 years, Cancer and Leukemia Group B (CALGB) performance status 0 to 2, lymphocyte count greater than or equal to 15,000 cells/microL, international stage B or C disease (multiple lymph nodes involved and/or hemoglobin [Hgb] less than 11 g and/or platelets less than 100,000/microL) and no more than one prior treatment regimen. DCF dose was 4 mg/m2 intravenously (IV) weekly for 3 weeks and then every 2 weeks. There were 39 eligible patients (35 men and four women; median age, 63 years; median time from diagnosis to study entry, 3 years). Of these 39 patients, 31% were stage B and 33% had no prior treatment. Median laboratory values at entry were Hgb 10.5 g, WBC 96,100/microL, and platelets 93,500/microL. Nodal involvement was present in 90%, splenomegaly in 81%, and hepatomegaly in 47%. Patients received a median of nine DCF injections, with a range of four to 26. Three patients were not evaluable for response. Overall, 3% achieved a complete response (CR), 23% a partial response (PR), 28% showed clinical improvement (CI), and 38% had stable disease (SD). Associated toxicities (grade 2 or worse) observed were infections (52%), worsening of thrombocytopenia (26%) or anemia (33%), nausea and vomiting (31%), rash or pruritus (20%), and stomatitis (8%). We conclude that DCF is an active agent in CLL with acceptable toxicity.

Plasma levels of soluble CD8 antigen and interleukin-2 receptor antigen in patients with hairy cell leukemia, relationship with splenectomy and with clinical response to therapy.

A soluble form of CD8 antigen (sCD8) has been shown to be released by activated CD8 + lymphocytes. Measurements of sCD8 may serve as an index of suppressor/cytotoxic cell activity. To assess the clinical significance of this observation in response to malignancy, we have investigated the sCD8 concentrations in 38 patients with hairy cell leukemia (HCL) not yet treated with any systemic therapy. The median plasma sCD8 level of the 20 nonsplenectomized patients was 1,025 U/ml and was significantly higher than that in the 18 patients who had previous splenectomy (median = 200 U/ml, p less than 0.0001), or in 14 normal controls (median = 350 U/ml, p less than 0.0001). Compared to controls, splenectomized patients had also significantly lower levels of sCD8 (p less than 0.01). The median concentration of soluble interleukin-2 receptor (sIL2R) in nonsplenectomized patients was 14,500 U/ml and was in the same range as in splenectomized patients (15,000 U/ml). There was no overlap in sIL2-R levels between controls (median = 300 U/ml) and patients. Investigation of serial plasma samples in 7 patients who received deoxycoformycin (DCF) and 11 patients treated with interferon alpha (IFN-alpha) showed a normalization of sCD8 levels and a decrease of sIL2R concentrations in those patients who showed hematological improvement. Normalization of sIL2R was, however, only observed in patients with complete remission. Our observation indicates that splenectomy might cause a reduction of the activation of suppressor/cytotoxic cells in patients with HCL. Treatment with either DCF or IFN-alpha also modulates the sCD8 levels to normal range. Measurements of sCD8 and sIL2-R might give more insight into the pathogenesis of HCL and serve as parameters for monitoring different phases of the disease and response to therapy.

The treatment of hairy cell leukemia with 2'-deoxycoformycin: results in India and in the United States.

We treated 11 patients (nine men and two women) with hairy cell leukemia with low doses of pentostatin (2'-deoxycoformycin). As of January 1987, 10 patients (91%) were in complete remission (CR) and one (9%) was in partial remission. Thus, the overall response rate was 100%. Maintenance therapy was not given once CR was attained, but no patient in CR relapsed: remission durations were from 40+ to 9+ months. For hairy cell leukemia, pentostatin is a better treatment than splenectomy and probably is superior to interferon, but further studies are needed to better define its role in this disease.

Treatment of hairy cell leukemia: the Ohio State University experience with deoxycoformycin.

Twelve evaluable patients with progressive hairy cell leukemia were treated with deoxycoformycin at a dose of 4 mg/m2 every 2 weeks. Five patients had not been splenectomized, and one had failed to respond to interferon-alpha. Complete remission, as defined by absence of hairy cells in the bone marrow and normalization of the peripheral blood and regression of splenomegaly, was obtained in 11 of 12 patients (92%). These patients have remained in unmaintained remission for 1+ to 13 months with an average of 7.5 months. Two of these patients had a bone marrow relapse at 8 and 12 months, respectively. During treatment the monocytopenia corrected, and, after complete remission was obtained, marrow was aspirable. Toxicity was mild and reversible. There were no significant infections associated with this treatment. It was of interest that we could treat two patients with creatinine clearance of 50 and 60 ml/min using lower doses (and 2-3 mg/m2) than our conventional therapy of 4 mg/m2 every 2 weeks. They obtained a complete remission after 6 and 10 treatments, respectively. Low-dose deoxycoformycin has proven to be an excellent treatment for hairy cell leukemia.

Prevention of graft-versus-host disease in allogeneic bone marrow transplantation by pretreatment with 2'-deoxycoformycin.

Germ-free mice were used as a model for acute graft-versus-host disease (GVHD) in allogeneic bone marrow transplantation (BMT). C3H/He recipients of DBA/2 cells showed typical symptoms of acute GVHD and died within 8 days. Incubation of the cells with 10 microM 2'-deoxycoformycin (2dCF) + 100 microM deoxyadenosine (dAdo) for 1 h inhibited all T-cell functions as well as T-cell-dependent B-cell functions, but had no effect on B-cell functions that are T-cell independent, nor on the hemopoietic stem cells (CFU-S). Recipients of allogeneic cells that had been incubated with 2dCF + dAdo for 1 h prior to inoculation showed no signs, gross or histological, of acute or chronic GVHD up to 15 months after transplantation. The recovery patterns of the blood and bone marrow were not affected by the treatment, and were similar to those of recipients of treated and untreated syngeneic cells.

The role of pentostatin (2'-deoxycoformycin, dCF) in the management of lymphoproliferative malignancies.

Laboratory and clinical data relating to the use of 2'-deoxycoformycin in human disease are reviewed. Pentostatin is an inhibitor of adenosine deaminase, an enzyme that is important for purine metabolism, but more than one mechanism may be involved in its cytotoxic action. Early studies with dCF employed large doses and for the most part were conducted in patients with acute lymphocytic leukaemia: responses were brief and relatively few, and severe renal, hepatic, and central nervous system toxicity were encountered, leading to temporary abandonment of clinical trials. More recently, it has been shown that dCF is effective in much smaller doses, with considerably less toxicity. It has proved to be more effective in low-grade lymphoid malignancies (chronic leukaemias, indolent lymphomas) than in more undifferentiated neoplasms (acute leukaemias, lymphoblastic and immunoblastic lymphomas), and is outstandingly effective in hairy cell leukaemia, both as initial therapy and after failure of splenectomy and interferon. Pentostatin is profoundly immunosuppressive: generally this is considered a disadvantage but its potential therapeutic exploitation merits investigation. Despite extensive knowledge of its biochemical effects, the optimal dose regimen of dCF and the value of combining it with purine antagonists remain to be defined.

Clinical, pharmacologic, and immunologic effects of 2'-deoxycoformycin.

Clinical, pharmacologic, and immunologic effects of 2'-deoxycoformycin (dCF) were evaluated in 15 patients with advanced malignancies. Toxicity was less severe with a low dose (4 mg/m2) of dCF, but this dose still resulted in suppression of cellular adenosine deaminase activity, skin test reactivity, and lymphocyte responses to mitogens. Improvement in cutaneous T cell lymphoma plaques was seen after dCF. Further investigations of antitumor efficacy with the use of this low dosage schedule should continue in patients with hematologic neoplasms, and additional preliminary studies of the combination of an adenosine deaminase inhibitor with an adenosine analog should also be considered.