Lack of significant activity of 2'-deoxycoformycin alone or in combination with adenine arabinoside in relapsed childhood acute lymphoblastic leukemia. A randomized phase II trial from the Childrens Cancer Study Group

Purine nucleoside analogues: fludarabine, pentostatin, and cladribine

Purpose. The primary objective of this article is to continue the discussion of the pharmacology, phar macokinetics, clinical use, and adverse effects of the currently approved adenosine analogues, focusing on pentostatin. This is part two of a three part series.

Data Sources. We reviewed the literature through a MEDLINE search from 1986 to 1996. Rele vant articles cited in the literature obtained by MED LINE searching also were considered. We searched the following terms: fludarabine, cladribine, pentosta tin, apoptosis, and adenosine analogues. The search was restricted to the English language.

Data Extraction. We have reviewed the current literature in regard to the chemistry, mechanisms of action and pharmacology, pharmacokinetics, clinical use, adverse effects, drug interactions, indications, formulation, dosage, administration, and pharmaceu tical issues of the currently approved adenosoine analogues, focusing on pentostatin.

Data Synthesis. The adenosine analogues are structurally similar agents used in the management of hematological malignancies. Pentostatin and cladrib ine are both active agents in the treatment of hairy cell leukemia. There are no comparative clinical trials between the agents, and we have provided compari sons based on pharmacology, clinical experience, adverse effects, and cost.

Long-term outcome in children with relapsed acute lymphoblastic leukemia after time-point and site-of-relapse stratification and intensified short-course multidrug chemotherapy: results of trial ALL-REZ BFM 90

PURPOSE

The multicenter trial ALL-REZ BFM (ie, Acute Lymphoblastic Leukemia Relapse Berlin-Frankfurt-Münster) 90 was designed to improve prognosis for children with relapsed acute lymphoblastic leukemia (ALL) by time-to-relapse- and site-of-relapse-adapted stratification and by introduction of novel chemotherapy elements and to evaluate new prognostic parameters in a large, population-based cohort.

PATIENTS AND METHODS

Five hundred twenty-five patients stratified into risk groups A (early bone marrow [BM] relapses), B (late BM relapses), and C (isolated extramedullary relapses) received alternating short-course intensive polychemotherapy (in blocks R1, R2, or R3) and cranial/craniospinal irradiation followed by maintenance therapy. Block R3 (high-dose cytarabine and etoposide) was introduced to improve the outcome compared with historical controls. Patients with early BM or T-ALL relapse (poor prognosis group [PPG]) were eligible for experimental regimens. One hundred seventeen patients received stem-cell transplantation (SCT).

RESULTS

The probabilities (and standard deviations) of event-free survival (pEFS) and overall survival (pOS) at 10 years were 0.30 +/- .02 and 0.36 +/- .02, respectively. Significant differences existed between strategic groups (pEFS(A) = .17 +/- .03; pEFS(B) = .43 +/- .04; pEFS(C) = .54 +/- .06; pEFS(PPG) = .15 +/- .03; log-rank P < .001). Patients of high-risk groups A plus PPG did better with SCT than with chemotherapy (pEFS = .33 +/- .05 v 0.20 +/- .05; P = .005). The pEFS was similar to trials ALL-REZ BFM 85/87 (.36 +/- .03. v 0.37 +/- .03; P = .419; PPG excluded). Time point, site of relapse, immunophenotype, and SCT were significant predictors of pEFS in multivariate analyses.

CONCLUSION

More than one third of patients in this large, population-based trial were cured. Neither R3 nor adaptation of chemotherapy intensity was capable of improving pEFS or of overcoming prognostic factors. In high-risk patients, remission induction regimens must be improved, and allogeneic SCT should be recommended in patients achieving second complete remission.

A novel therapeutic strategy against monocytic leukemia with deoxyadenosine analogs and adenosine deaminase inhibitors

The adenosine deaminase inhibitor 2'-deoxycoformycin (dCF) significantly inhibits the proliferation of leukemia and lymphoma cells in the presence of either 2'-deoxyadenosine (dAdo) or its analog adenine arabinoside (araA). The concentration of dCF required to induce apoptosis of monocytoid leukemia cells is much lower than that required for myeloid, erythroid, or lymphoma cells. dATP effectively induces caspase-3 activation in cytosol from monocytoid cells, but not in that from non-monocytoid cells, suggesting that dATP-dependent caspase-3 activation is involved in the preferential induction of apoptosis in monocytoid leukemia cells. Athymic nude mice inoculated with human monocytoid leukemia U937 cells show significantly prolonged survival following combined treatment with dCF and araA. The clinical usefulness of the combination of adenosine deaminase inhibitor and dAdo analog is discussed.

Vidarabine and 2-deoxycoformycin as antileukemic agents against monocytic leukemia

Although 2'-deoxycoformycin (dCF) has been reported in clinical trials to be less effective against myeloid than lymphoid malignancies, it may be useful for treating monocytic leukemia with the aid of 2'-deoxyadenosine (dAd) analogs. In the presence of 10 microM dAd, the concentration of dCF required to inhibit the viability of monocytoid leukemia cells was much lower than that required on normal or non-monocytoid malignant cells in primary culture. Among the dAd analogs, 9-beta-D-arabinofuranosyladenine (AraA) was also effective in combination with dCF. Although dCF alone slightly but significantly prolonged the survival of mice inoculated with U937 monocytic leukemia cells, combined treatment with dCF and AraA markedly prolonged the survival. These results suggest that the combination of dCF and AraA may be useful for the clinical treatment of acute monocytic leukemia.

Antileukemic efficacy of 2′-deoxycoformycin in monocytic leukemia cells

2′-Deoxycoformycin (dCF) as a single agent has been reported to be less effective against myeloid than against lymphoid malignancies in clinical trials. However, previous studies have shown that in the presence of 2′-deoxyadenosine (dAd), human monocytoid leukemia cell lines are much more sensitive to dCF with regard to the inhibition of cell proliferation. Thus, dCF might be useful for treating monocytoid leukemia with the aid of dAd analogs. The antiproliferative effects of dCF in combination with dAd or its derivatives were examined on normal and malignant blood and bone marrow cells. In the presence of 10 μmol/L dAd, the concentration of dCF required to inhibit the viability of primary monocytoid leukemia cells was much lower than that required to inhibit normal or non-monocytoid leukemic cells. Among the dAd analogs, 9-β-d-arabinofuranosyladenine (AraA) was also effective in combination with dCF. Athymic nude mice were inoculated with human monocytoid leukemia U937 cells and treated with dCF or a dAd analog or both. Although dCF alone slightly but significantly prolonged the survival of mice inoculated with U937 cells, combined treatment with dCF and AraA markedly prolonged their survival. These data suggest that the combination of dCF and AraA may be useful for the clinical treatment of acute monocytic leukemia.

Antileukemic efficacy of 2′-deoxycoformycin in monocytic leukemia cells

2′-Deoxycoformycin (dCF) as a single agent has been reported to be less effective against myeloid than against lymphoid malignancies in clinical trials. However, previous studies have shown that in the presence of 2′-deoxyadenosine (dAd), human monocytoid leukemia cell lines are much more sensitive to dCF with regard to the inhibition of cell proliferation. Thus, dCF might be useful for treating monocytoid leukemia with the aid of dAd analogs. The antiproliferative effects of dCF in combination with dAd or its derivatives were examined on normal and malignant blood and bone marrow cells. In the presence of 10 μmol/L dAd, the concentration of dCF required to inhibit the viability of primary monocytoid leukemia cells was much lower than that required to inhibit normal or non-monocytoid leukemic cells. Among the dAd analogs, 9-β-d-arabinofuranosyladenine (AraA) was also effective in combination with dCF. Athymic nude mice were inoculated with human monocytoid leukemia U937 cells and treated with dCF or a dAd analog or both. Although dCF alone slightly but significantly prolonged the survival of mice inoculated with U937 cells, combined treatment with dCF and AraA markedly prolonged their survival. These data suggest that the combination of dCF and AraA may be useful for the clinical treatment of acute monocytic leukemia.

Myeloid and monocytoid leukemia cells have different sensitivity to differentiation-inducing activity of deoxyadenosine analogs

The differentiation-inducing effect of clinically applicable analogs of deoxyadenosine on myelomonocytic leukemia cells was examined. Monocytoid leukemia cells were more sensitive to the analogs than were erythroid or myeloid leukemia cells based on the inhibition of cell growth and induction of cell differentiation. Monocytoid leukemia cells were highly sensitive to combined treatment with 2'-deoxycoformycin (dCF) and 9-beta-D-arabinofuranosyladenine (Ara A) for inducing cell differentiation. Ara A induced the differentiation of monocytoid leukemia U937 and THP-1 cells at concentrations which were 1/1000-10000 of that at which it induced the differentiation of other cell lines in the presence of dCF. In combination with a low concentration of 1alpha,25-dihydroxyvitamin D3 (VD3), the induction of the monocytic differentiation was greater in monoblastic U937 cells. Adenosine deaminase-resistant analogs such as fludarabine (FLU) and cladribine (CdA) also induced the differentiation of human myelomonocytic leukemia cells, and these analogs synergistically enhanced the differentiation induced by all-trans retinoic acid (ATRA) or VD3. CdA was the most potent analog for inducing the differentiation of myeloid leukemia NB4 and HL-60 cells in the presence or absence of ATRA. These findings indicate that dCF + Ara A and CdA may be effective for the therapy of acute monocytoid and myeloid leukemia, respectively.