Ibrutinib-induced acute kidney injury via interstitial nephritis.

The introduction of Bruton's tyrosine kinase inhibitor ibrutinib has made a significant progress in the treatment of chronic lymphocytic leukemia and other B-cell malignancies. Due to the reduction of cytokine release, it is effective in chronic graft-versus-host disease, and its use has also been suggested in autoimmune diseases and in prevention of COVID-19-associated lung damage. Despite this effect on the immune response, we report a severe hypersensitivity reaction in a 76-year-old male patient diagnosed with prolymphocytic leukemia. Four weeks after the ibrutinib start, non-oliguric acute kidney injury with proteinuria and microscopic hematuria developed and that was accompanied by lower limb purpuras and paresthesia. Renal biopsy revealed acute interstitial nephritis. Employing 1 mg/kg methylprednisolone administration, serum creatinine decreased from 365 µmol/L to 125 µmol/L at 11 days and the proteinuria-hematuria as well as the purpura, paresthesia resolved. Three months later at stabile eGFR of 56 ml/min/1.73 m2 methylprednisolone was withdrawn and a rituximab-venetoclax treatment was initiated without side effects. We conclude that despite the beneficial effect on cytokines response in Th1 direction, ibrutinib can cause acute interstitial nephritis. Early detection, discontinuation of ibrutinib, glucocorticoid administration may help to better preserve renal function, thereby lowering the risk of potential subsequent kidney injury.

How I treat prolymphocytic leukemia.

T- and B-cell subtypes of prolymphocytic leukemia (PLL) are rare, aggressive lymphoid malignancies with characteristic morphologic, immunophenotypic, cytogenetic, and molecular features. Recent studies have highlighted the role of specific oncogenes, such as TCL-1, MTCP-1, and ATM in the case of T-cell and TP53 mutations in the case of B-cell prolymphocytic leukemia. Despite the advances in the understanding of the biology of these conditions, the prognosis for these patients remains poor with short survival and no curative therapy. The advent of monoclonal antibodies has improved treatment options. Currently, the best treatment for T-PLL is intravenous alemtuzumab, which has resulted in very high response rates of more than 90% when given as first-line treatment and a significant improvement in survival. Consolidation of remissions with autologous or allogeneic stem cell transplantation further prolongs survival, and the latter may offer potential cure. In B-PLL, rituximab-based combination chemo-immunotherapy is effective in fitter patients. TP53 abnormalities are common and, as for chronic lymphocytic leukemia, these patients should be managed using an alemtuzumab-based therapy. The role of allogeneic transplant with nonmyeloablative conditioning needs to be explored further in both T- and B-cell PLL to broaden the patient eligibility for what may be a curative treatment.

Clinical efficacy of immunochemotherapy with fludarabine, epirubicin and rituximab in the treatment for chronic lymphocytic leukaemia and prolymphocytic leukaemia.

Despite some considerable progress in the therapy for chronic lymphocytic leukaemia (CLL) owing to fludarabine-based regimens and rituximab, no curative treatment is available so far. We conducted an explorative phase II study in patients with CLL, prolymphocytic leukaemia (PLL) and leukaemic lymphoplasmacytic lymphoma (LL) with the combination of fludarabine, epirubicin and rituximab (FER) to improve the complete remission (CR) rate and progression-free survival (PFS). Fludarabine 25 mg/m(2) was administered i.v. on days 1-5 and epirubicin 25 mg/m(2) i.v. on days 4 and 5, and rituximab was added at a dose of 375 mg/m(2) i.v. day 1 in the first cycle and at a dose of 500 mg/m(2) in all consecutive cycles. Patients exhibiting responsive disease after FER were eligible to receive maintenance therapy of up to 12 cycles of rituximab 375 mg/m(2) bimonthly. Forty-four patients (38 CLL, 4 PLL and 2 LL) with a median age of 65 yrs (43-84 yrs) were evaluable. Seventeen patients with CLL had stage Binet C, 14 Binet B and seven symptomatic or rapid progressive stage Binet A. Cytogenetic features showed normal karyotype in nine cases, an isolated deletion (del) 13q in 12 patients, trisomy 12 in 7, del 11 in two and del 17p in 4. Half of the patients (48%) had mutated IgVH genes. Treatment with FER achieved an overall response rate of 95%, including 63% CRs and 32% PRs. Haematological toxicity was considerable. After a median follow-up period of 34 months (range: 8-84 months), median PFS was 61 months and overall survival was yet not reached. All patients with PLL and LL achieved CR. The data support the high efficacy of the combination of rituximab with chemotherapy (FE) and are suggestive of possible benefit with rituximab maintenance therapy for PFS and DFS.

Cryptococcal immune reconstitution inflammatory syndrome following alemtuzumab therapy.

Alemtuzumab is a lymphocyte ablative agent that may cause susceptibility to severe opportunistic infections similar to those seen in AIDS. Pathogen-specific immune reconstitution syndromes can complicate antiretroviral therapy and immune recovery in HIV-infected patients. We present the first reported case of immune reconstitution syndrome associated with T lymphocyte recovery after alemtuzumab therapy.

Phase I/II study of the mammalian target of rapamycin inhibitor everolimus (RAD001) in patients with relapsed or refractory hematologic malignancies.

PURPOSE: Everolimus (RAD001, Novartis), an oral derivative of rapamycin, inhibits the mammalian target of rapamycin (mTOR), which regulates many aspects of cell growth and division. A phase I/II study was done to determine safety and efficacy of everolimus in patients with relapsed or refractory hematologic malignancies. EXPERIMENTAL DESIGN: Two dose levels (5 and 10 mg orally once daily continuously) were evaluated in the phase I portion of this study to determine the maximum tolerated dose of everolimus to be used in the phase II study. RESULTS: Twenty-seven patients (9 acute myelogenous leukemia, 5 myelodysplastic syndrome, 6 B-chronic lymphocytic leukemia, 4 mantle cell lymphoma, 1 myelofibrosis, 1 natural killer cell/T-cell leukemia, and 1 T-cell prolymphocytic leukemia) received everolimus. No dose-limiting toxicities were observed. Grade 3 potentially drug-related toxicities included hyperglycemia (22%), hypophosphatemia (7%), fatigue (7%), anorexia (4%), and diarrhea (4%). One patient developed a cutaneous leukocytoclastic vasculitis requiring a skin graft. One patient with refractory anemia with excess blasts achieved a major platelet response of over 3-month duration. A second patient with refractory anemia with excess blasts showed a minor platelet response of 25-day duration. Phosphorylation of downstream targets of mTOR, eukaryotic initiation factor 4E-binding protein 1, and/or, p70 S6 kinase, was inhibited in six of nine patient samples, including those from the patient with a major platelet response. CONCLUSIONS: Everolimus is well tolerated at a daily dose of 10 mg daily and may have activity in patients with myelodysplastic syndrome. Studies of everolimus in combination with therapeutic agents directed against other components of the phosphatidylinositol 3-kinase/Akt/mTOR pathway are warranted.

Prolymphocytic leukemias.

T and B subtypes of prolymphocytic leukemias (PLLs) are rare, highly aggressive lymphoid malignancies with characteristic morphologic, immunophenotypical, cytogenetic, and molecular features. Recent studies have highlighted the role of specific oncogenes such as TCL1, MTCP-1, and ATM in the case of T-cell and p53 mutations in the case of B-cell PLLs. Despite the advances in the understanding of the biology of these conditions, prognosis for these patients remains poor with short survival and no curative treatment. The advent of monoclonal antibody therapy has improved treatment options for this group. In particular, the use of Campath-1H, in T-PLL has more than doubled median survival. The role of allogeneic transplant with nonmyeloablative conditioning needs to be explored further.

T-cell prolymphocytic leukemia.

T-cell prolymphocytic leukemia (T-PLL) is a rare aggressive post-thymic malignancy with poor response to conventional treatment and short survival. It can readily be distinguished from other T-cell leukemias on the basis of the distinctive morphology, immunophenotype, and cytogenetics. Consistent chromosomal translocations involving the T-cell receptor gene and one of two protooncogenes (TCL-1 and MTCP-1) are seen in the majority of cases and are likely to be involved in the pathogenesis of the disorder. The CD52 antigen is expressed at high density on the malignant T-cells and therapy with alemtuzumab, a humanized IgG1 antibody that targets this antigen, has produced promising results. In relapsed/refractory patients overall and complete response rates have been seen in up to 76% and 60%, respectively. In previously untreated patients, complete remission rates of 100% have been reported. These responses are durable and translate into improved survival for responders. However, relapse is inevitable and strategies using both autologous and allogeneic stem cell transplantation are currently being explored. Additional clinical trials are investigating the use of alemtuzumabin combinations with chemotherapy, either concurrent or sequential. In the future we hope to have a betterunderstanding of how best to integrate these therapeutic approaches to further prolong survival for patients with T-PLL.

Pentostatin in prolymphocytic leukemia: phase II trial of the European Organization for Research and Treatment of Cancer Leukemia Cooperative Study Group.

BACKGROUND: B-cell prolymphocytic leukemias or T-cell prolymphocytic leukemias are aggressive variants of chronic lymphoid leukemias. The small studies conducted to date have shown median survival durations of approximately 3 years for patients who have B-cell prolymphocytic leukemia and 7.5 months for those who have T-cell prolymphocytic leukemia, compared with about 8 years for patients who have chronic lymphocytic leukemia. In chronic lymphocytic leukemia, chemotherapy consisting of alkylating agents such as cyclophosphamide and chlorambucil combined with prednisone has achieved overall response rates of 50% to 70%, but this regimen has resulted in response rates of less than 25% in prolymphocytic leukemia. Pentostatin (2'-deoxycoformycin; DCF) is a purine analogue that has shown activity in treatment of chronic lymphoid malignancies. PURPOSE: This prospective phase II trial by the Leukemia Cooperative Group of the European Organization for Research and Treatment of Cancer was performed to assess the activity and toxicity of DCF in prolymphocytic leukemia. METHODS: Twenty patients with B-cell or T-cell prolymphocytic leukemia were given DCF at a dosage of 4 mg/m2 intravenously once a week for 3 weeks, then every other week for three doses. Patients who had at least partial response received maintenance therapy once a month for a maximum of 6 months. Fourteen patients had B-cell prolymphocytic leukemia, and six had T-cell prolymphocytic leukemia, as evidenced by morphologic and immunologic criteria; three were previously untreated, eight had been given one or two chemotherapeutic regimens, and nine had been given more than two. RESULTS: One patient died of an unknown cause during the first 6 weeks of treatment, and one died of disseminated toxoplasmosis during the period of maintenance therapy, 5 months after achieving partial remission. Nine (45% response rate) of the 20 patients achieved partial remission, including seven (50%) of 14 with B-cell prolymphocytic leukemia and two (33%) of six with T-cell prolymphocytic leukemia. The median duration of response was 9 months (range, 2-30 months); for patients with B-cell prolymphocytic leukemia, the median remission duration was 12 months. No complete remission was observed. Toxic effects included nausea and vomiting (30%), infections (30%), and transient increase in liver enzymes (35%) and in creatinine (20%) levels. Eight patients experienced thrombocytopenia, the major hematologic toxic effect; four had grade 3 or 4 toxic effects. CONCLUSION: DCF is active in prolymphocytic leukemia, even as salvage therapy in patients who had received multiple prior chemotherapeutic regimens. IMPLICATIONS: Trials using DCF or other purine analogues alone or in combination with standard chemotherapeutic agents in front-line or salvage therapy are warranted to improve the prognosis of patients with prolymphocytic leukemia.

Major activity of cladribine in patients with de novo B-cell prolymphocytic leukemia.

PURPOSE: De novo B-cell prolymphocytic leukemia (B-PLL) is a distinct clinicopathologic entity usually characterized by marked lymphocytosis, massive splenomegaly, an aggressive course, and refractoriness to therapy. Cladribine (2-chlorodeoxyadenosine [2-CdA]; Ortho Biotech, Raritan, NJ) is a newer purine analog with potent activity against indolent lymphoproliferative disorders. PATIENTS AND METHODS: We treated eight patients with cladribine 0.1 mg/kg/d for 7 days by continuous infusion or 0.14 mg/kg/d over 2 hours for 5 days, every 28 to 35 days, for a median of three courses (range, two to five). There were five men and three women, with a median age of 62 years and a median pretreatment duration of 6 months; four patients were previously untreated. RESULTS: All eight patients were assessable: five achieved a complete response with a median response duration of 14 months (range, 1+ to 55+), and three achieved a partial response with a median duration of 3 months (range, 1 to 3). Of four patients who achieved a complete response and in whom a peripheral-blood immunophenotypic analysis was performed, two had no circulating B-PLL cells and one had no residual disease on Southern blot analysis. Myelosuppression and infection were the major toxicities: three patients developed grade 3 or 4 myelosuppression, four had bacterial infections, and two had herpes zoster infections. CONCLUSION: In this small study of patients with de novo B-PLL, cladribine was an active agent that induced a high overall and complete response rate. These results require confirmation in larger numbers of B-PLL patients.

Treatment of T-cell prolymphocytic leukemia with human CD52 antibody.

PURPOSE: T-prolymphocytic leukemia (T-PLL) is an aggressive malignancy of mature T cells refractory to conventional chemotherapy, with a median survival duration of 7.5 months. We report here promising results with the use of a genetically reshaped human CD52 antibody, CAMPATH-1H. PATIENTS AND METHODS: Fifteen patients with T-PLL, most of whom had received the purine analog deoxycoformycin (DCF), were treated with CAMPATH-1H. Results were compared with those of 25 patients treated with DCF. RESULTS: Major responses occurred in 11 patients (73%) treated with CAMPATH-1H compared with 40% with DCF. Complete remissions (CRs) were documented in nine (60%) of the CAMPATH-1H cases and only three (12%) were obtained with DCF. CRs with CAMPATH-1H were durable, and re-treatment with the antibody resulted in second CRs in three relapsed patients. Two of them were successfully autografted with peripheral-blood and bone marrow stem cells collected during the first CR. Apart from first-dose reactions, infusions of CAMPATH-1H were well tolerated. However, two responding patients developed severe bone marrow aplasia that was fatal in one; the second remained moderately pancytopenic 21 weeks after stopping CAMPATH-1H therapy. The cause of this adverse effect is unknown. CONCLUSION: CAMPATH-1H is an effective agent in T-PLL and represents a significant improvement over other types of therapy. However, CAMPATH-1H alone is not sufficient for long-term remissions, and the role of autologous stem-cell transplantation needs further investigation.

Evaluation of the combination of nelarabine and fludarabine in leukemias: clinical response, pharmacokinetics, and pharmacodynamics in leukemia cells.

PURPOSE: A pilot protocol was designed to evaluate the efficacy of fludarabine with nelarabine (the prodrug of arabinosylguanine [ara-G]) in patients with hematologic malignancies. The cellular pharmacokinetics was investigated to seek a relationship between response and accumulation of ara-G triphosphate (ara-GTP) in circulating leukemia cells and to evaluate biochemical modulation of cellular ara-GTP metabolism by fludarabine triphosphate. PATIENTS AND METHODS: Nine of the 13 total patients had indolent leukemias, including six whose disease failed prior fludarabine therapy. Two patients had T-acute lymphoblastic leukemia, one had chronic myelogenous leukemia, and one had mycosis fungoides. Nelarabine (1.2 g/m(2)) was infused on days 1, 3, and 5. On days 3 and 5, fludarabine (30 mg/m(2)) was administered 4 hours before the nelarabine infusion. Plasma and cellular pharmacokinetic measurements were conducted during the first 5 days. RESULTS: Seven patients had a partial or complete response, six of whom had indolent leukemias. The disease in four responders had failed prior fludarabine therapy. The median peak intracellular concentrations of ara-GTP were significantly different (P =.001) in responders (890 micromol/L, n = 6) and nonresponders (30 micromol/L, n = 6). Also, there was a direct relationship between the peak fludarabine triphosphate and ara-GTP in each patient (r = 0.85). The cellular elimination of ara-GTP was slow (median, 35 hours; range, 18 to > 48 hours). The ratio of ara-GTP to its normal counterpart, deoxyguanosine triphosphate, was higher in each patient (median, 42; range, 14 to 1,092) than that of fludarabine triphosphate to its normal counterpart, deoxyadenosine triphosphate (median, 2.2; range, 0.2 to 27). CONCLUSION: Fludarabine plus nelarabine is an effective, well-tolerated regimen against leukemias. Clinical responses suggest the need for further exploration of nelarabine against fludarabine-refractory diseases. Determination of ara-GTP levels in the target tumor population may provide a prognostic test for the activity of nelarabine.

T-cell prolymphocytic leukemia: a single-institution experience.

BACKGROUND: T-cell prolymphocytic leukemia is an uncommon, aggressive, mature T-cell leukemia characterized by proliferation of T-cell lymphocytes. The recent availability of modern immunophenotypic and molecular tools has allowed a better distinction of this disorder from its B-cell counterpart and other mature T-cell leukemias. PATIENTS AND METHODS: The clinical, pathologic, and cytogenetic features of 57 patients with T-PLL who were evaluated at the Department of Leukemia, M. D. Anderson Cancer Center (MDACC) from 1986 to 2004 were examined. RESULTS: The most common cytogenetic abnormality was inv(14)(q11;q32), which was present in 7 patients. In all 7 patients, this abnormality was associated with other chromosomal aberrations. Patients treated with alemtuzumab at MDACC had a significantly better response rate (P = 0.02) and survival rate (P = 0.002). There were no significant differences in survival based on Tcl-1 expression or different patterns of CD4 and CD8 expression. CONCLUSION: Treatment with alemtuzumab results in higher response rates and a better survival rate in patients with T-cell prolymphocytic leukemia.

Phenotypic transformation of CD52(pos) to CD52(neg) leukemic T cells as a mechanism for resistance to CAMPATH-1H.

Immunotherapy utilizing CAMPATH-1H for patients with chemotherapy-refractory chronic lymphocytic leukemia has yielded encouraging results with many reports of complete remission. Here we report the outcome of two patients with CD4-positive T cell prolymphocytic leukemia treated with CAMPATH-1H. Both patients responded rapidly to treatment and subsequently developed CD4 lymphopenia. One patient remained in complete remission after 14 weeks of treatment. Serial peripheral blood flow cytometry revealed that the CD52 antigen was present throughout treatment. The other patient who was initially CD52-positive, became CD52-negative after 6 weeks of treatment, and developed progressive symptoms of T cell prolymphocytic leukemia. Immunotherapy was stopped, chemotherapy proved futile, and the patient died. This change in phenotype from CD52-positive to -negative during CAMPATH-1H therapy points out a need to develop strategies for maintaining antigenic expression during monoclonal antibody therapy.

Pentostatin (Nipent) in T-cell malignancies. Leukemia Cooperative Group and the European Organization for Research and Treatment of Cancer.

Within this phase II trial of the European Organization for Research and Treatment of Cancer, we have investigated the safety and efficacy of pentostatin (Nipent; SuperGen, San Ramon, CA) in refractory lymphoid malignancies. Pentostatin was administered at a dosage of 4 mg/m2 every week for the first 3 weeks, then every 14 days, followed by maintenance therapy of 4 mg/m2 monthly for a maximum of 6 months. We have previously reported the results in T- and B-cell prolymphocytic leukemia, B-cell chronic lymphocytic leukemia, and hairy cell leukemia This report focuses on the outcome in T-cell malignancies: T-cell chronic lymphocytic leukemia, Sézary syndrome, mycosis fungoides, and T-zone lymphoma. Of 92 patients with these diagnoses enrolled, 76 were evaluable for response and toxicity, ie, 25 of 28 with T-cell chronic lymphocytic leukemia, 21 of 26 with Sézary syndrome, 22 of 26 with mycosis fungoides, and eight of 12 with T-zone lymphoma. All patients had progressive and advanced disease. Sixteen patients (21%) died during the first 9 weeks of treatment: 12 of progressive disease, two of infectious complications thought to be unrelated to treatment, one of myocardial infarction, and one of renal failure related to administration of intravenous contrast. Major toxicity (grades 3 and 4) included infection in 10.5% of patients, nausea/vomiting in 5%, and hepatotoxicity in 3%. One patient (1.3%) achieved a complete remission and 15 (19.7%) a partial remission. Better results were achieved in patients with Sézary syndrome or mycosis fungoides (complete remission + partial remission = 33.4% and 22.7%, respectively) than in patients with T-cell chronic lymphocytic leukemia (8%) or T-zone lymphoma (25%). We conclude that pentostatin is active in low-grade T-cell malignancies. Toxicities are mild to moderate at the dose schedule administered. Severe hematologic toxicity has not been observed. The efficacy at the present dose level is moderate. A higher dose might be necessary for some T-cell malignancies.

Clinical overview of pentostatin (Nipent) use in lymphoid malignancies.

We summarize the results of our experience over the past 15 years using pentostatin (Nipent; SuperGen, San Ramon, CA) to treat a range of mature B- and T-cell malignancies. This includes 145 patients with postthymic T-cell malignancies in whom disease subtype was found to be the most significant predictor of response, with the best response rates seen in Sézary syndrome (62%) and T-prolymphocytic leukemia (45%). However, there are no long-term survivors among patients with this group of disorders, and strategies using pentostatin in combination with other therapies, such as CAMPATH-1H, are currently being explored. Among the mature B-cell diseases, pentostatin in both standard- and low-dose regimens is effective in advanced, relapsed/refractory B-chronic lymphocytic leukaemia, showing no cross-resistance with other purine analogs such as fludarabine. Our largest series treated with pentostatin consists of 165 patients with hairy cell leukemia. The follow-up period in this group extends to more than 10 years, with a projected event-free survival rate at 5 years of 60% and an overall survival rate of 97%.

Efficacy of fludarabine, a new adenine nucleoside analogue, in patients with prolymphocytic leukemia and the prolymphocytoid variant of chronic lymphocytic leukemia.

PURPOSE: To describe the results of fludarabine therapy in patients with prolymphocytic leukemia (PLL) and the prolymphocytoid variant of chronic lymphocytic leukemia (CLL-Pro). PATIENTS AND METHODS: Seventeen patients with a diagnosis of PLL or CLL-Pro received fludarabine 30 mg/m2 over 30 minutes daily for 5 days every 4 weeks alone (12 patients), or with prednisone (five patients). Previously defined criteria for response were used. Differences in response rates according to various characteristics were evaluated by chi-square test. RESULTS: Three patients (18%) achieved complete remission, and three (18%) had a partial remission, for an overall response rate of 35%. Responses were durable and occurred in all involved organ sites. Lower response rates were observed in patients with anemia, thrombocytopenia, advanced Rai stages, and primary resistance to prior therapy. Toxicities were minimal except for febrile episodes associated with therapy. CONCLUSION: Fludarabine has shown encouraging results in these patients and deserves further investigation in combination with other active agents, and in the setting of front-line therapy.

Retinobenzoic acids. 5. Retinoidal activities of compounds having a trimethylsilyl or trimethylgermyl group(s) in human promyelocytic leukemia cells HL-60.

The retinoidal activities of trimethylsilyl or trimethylgermyl-containing retinobenzoic acids are discussed on the basis of differentiation-inducing activity on human promyelocytic leukemia cells HL-60. Compounds with a trimethylsilyl or trimethylgermyl group at the meta position of the generic formula 2 have more potent activities than the corresponding retinobenzoic acids with a m-tert-butyl group. Compounds having two m-trimethylsilyl or -trimethylgermyl groups also have strong activities, and (E)-4-[3-[3,5-bis(trimethylsilyl)phenyl]-3-oxo-1-propenyl]benzoic acid (22, Ch55S) and (E)-4-[3-[3,5-bis(trimethylgermyl)phenyl]-3-oxo-1- propenyl]benzoic acid (35, Ch55G) are more active than retinoic acid by 1 order of magnitude. However, in the para-substituted chalcone derivatives, the replacement of a tert-butyl group (49, Ch40) with a trimethylsilyl (27, Ch40S) or a trimethylgermyl (30, Ch40G) group caused the disappearance of the activity.

Effects of dolastatins on human B-lymphocytic leukemia cell lines.

Dolastatins are naturally occurring peptides isolated from marine animals and are known to be potent anti-neoplastic agents. Here, the three compounds dolastatin 10 (Dola 10), dolastatin 15 (Dola 15) and deo-dolastatin 10 (Deo-Dola 10) were added to cultures of two human chronic B-leukemia cell lines, JVM-2 and EHEB. The three dolastatins (Dola 10 > Dola 15 > Deo-Dola 10) inhibited cell proliferation and immunoglobulin production. Decreased cell growth and lack of accumulation of immunoglobulin was not caused by cytotoxicity as cell viability in the cultures remained high. The unchanged surface marker immunoprofiles during treatment and a predominance of treated cells in S and G2/M phase suggested cytostatic rather than directly cytotoxic effects. Exposure to these reagents increased quickly, albeit only short c-myc and bcl-2 mRNA expression. These results indicate that the three dolastatins are potent inhibitors of leukemic B-cell proliferation.

Enzyme activities of leukemic cells and biochemical changes induced by deoxycoformycin in vitro--lack of correlation with clinical response.

Deoxycoformycin (DCF) is a specific inhibitor of adenosine deaminase (ADA) and has been shown to be active in lymphoid neoplasms. Cytotoxicity is thought to be mediated by the accumulation of deoxyadenosine (AdR) and deoxyadenosine triphosphate (dATP) which inhibits ribonucleotide reductase and DNA synthesis in rapidly proliferating cells. Others suggested mechanisms leading to cell death particularly in non-dividing cells include depletion of ATP and NAD pools, inhibition of S-adenosylhomocysteine (SAH) hydrolase and induction of DNA strand breaks. In patients with high leukemic counts who were subsequently treated with DCF, we have studied (a) the levels of ADA, ecto-5'-nucleotidase (5NT), deoxyadenosine kinase (AdR-kinase) and SAH-hydrolase in the leukemic cells; [b) the in-vitro effects of DCF on dATP, ATP, NAD, SAH-hydrolase levels and on DNA strand breaks; and (c) the correlation between these parameters with clinical response to DCF. No significant difference in ADA, 5NT, AdR-kinase and SAH-hydrolase activities could be found between responders and non-responders. Incubation of the leukemic cells in vitro with DCF caused an inhibition of ADA, an accumulation of dATP, a moderate reduction in ATP and NAD levels, a suppression of SAH-hydrolase activity and an increase in DNA strand breaks in practically all the leukemic samples, irrespective of clinical response. Our results show that neither measurement of these enzymes nor studies of these biochemical sequelae of ADA inhibition in vitro predicts clinical responsiveness to DCF therapy.