2-Chlorodeoxyadenosine produces a high rate of complete hematologic remission in relapsed acute myeloid leukemia

Decitabine as epigenetic priming with CLAG induce improved outcome of relapsed or refractory acute myeloid leukemia in children

BACKGROUND

Decitabine (DAC), a DNA methyltransferase inhibitor, has shown efficacy combined with chemotherapy for relapsed or refractory (R/R) acute myeloid leukemia (AML) in adults, but less is known about its efficacy in children. Accordingly, we conducted a study which involved a priming regimen consisting of DAC with cladribine, cytarabine, and granulocyte-stimulating factor (DAC-CLAG) and compared the efficacy and safety of this regimen with CLAG alone.

METHODS

A total of 39 R/R AML children who received the CLAG or DAC-CLAG regimen in Shanghai Children's Hospital were retrospectively enrolled in this non-randomized study. These regimens were studied sequentially over time. Twenty-two patients received CLAG from 2015, while 17 patients were administered epigenetic priming with DAC before CLAG from 2020. Patients were subsequently bridged to stem cell transplantation (SCT) or consolidation chemotherapy. Complete remission (CR) and adverse effects were analyzed by Fisher's exact test, and survival was analyzed by the Kaplan-Meier method.

RESULTS

DAC-CLAG conferred a numerically higher CR compared to CLAG (70.59% vs 63.64%; P = 0.740). High CR rates occurred in patients with good cytogenetics (P = 0.029) and prior induction without cladribine (P = 0.099). The 1-year event-free survival (EFS) was 64.71% ± 11.59% and 63.31% ± 10.35% in the DAC-CLAG and CLAG group (P = 0.595), and 1-year overall survival (OS) was 81.45% ± 9.72% and 77.01% ± 9.04%, respectively (P = 0.265). The 1-year OS and EFS after SCT were higher in the DAC-CLAG than in the CLAG cohort (100% vs 92.31% ± 7.39%, P = 0.072; 92.31% ± 7.39% vs 85.71% ± 9.35%, P = 0.158). Univariate analysis revealed that a good prognosis included good cytogenetics (P = 0.002), non-complex karyotype (P = 0.056), CR on reinduction (P < 0.0001), and bridging to SCT (P = 0.0007). Use of a hypomethylating agent (P = 0.049) and bridging to SCT (P = 0.011) were independent prognostic factors. Grade 3/4 hematologic toxicity and infection were the main adverse events.

CONCLUSIONS

DAC prior to the CLAG regimen improved remission in pediatric R/R AML, and was feasible and well tolerated. CLAG ± DAC as a salvage therapy prior to SCT induced improved survival.

Safety and efficacy of cladribine in multiple sclerosis: a systematic review and meta-analysis

BACKGROUND

Previously, several studies investigated the effect of cladribine among patients with multiple sclerosis (MS) as a treatment option. Due to the contradictory results of previous studies regarding the efficacy and safety of cladribine in the MS population, we aimed to conduct a systematic review and meta-analysis by including clinical trials and observational studies in terms of having more confirmative results to make a general decision.

METHODS

The three databases including PubMed, Scopus, and Web of Science were comprehensively searched in May 2022. We included the studies that investigated the efficacy and safety of cladribine in patients with MS. Eligible studies have to provide sufficient details on MS diagnosis and appropriate follow-up duration. We investigated the efficacy of cladribine with several outcomes including Expanded Disability Status Scale (EDSS) change, progression-free survival (PFS), relapse-free survival (RFS), and MRI-free activity survival (MFAS).

RESULTS

After two-step reviewing, 23 studies were included in our qualitative and quantitative synthesis. The pooled SMD for EDSS before and after treatment was - 0.54 (95%CI: - 1.46, 0.39). Our analysis showed that the PFS after cladribine use is 79% (95%CI 71%, 86%). Also, 58% of patients with MS who received cladribine remained relapse-free (95%CI 31%, 83%). Furthermore, the MFAS after treatment was 60% (95%CI 36%, 81%). Our analysis showed that infection is the most common adverse event after cladribine treatment with a pooled prevalence of 10% (95%CI 4%, 18%). Moreover, the pooled prevalence of infusion-related adverse events was 9% (95%CI 4%, 15%). Also, the malignancies after cladribine were present in 0.4% of patients (95%CI 0.25%, 0.75%).

CONCLUSION

Our results showed acceptable safety and efficacy for cladribine for the treatment of MS except in terms of reducing EDSS. Combination of our findings with the results of previous studies which compared cladribine to other disease-modifying therapies (DMTs), cladribine seems to be a safe and effective drug in achieving better treatment for relapsing-remitting MS (RRMS) patients.

Acute myeloid leukemia in the medically unfit elderly patients

Acute Myeloid Leukemia is a clonal proliferative disorder whose incidence increases with age. While studies have shown that the elderly medically unfit patients have poorer outcomes with intensive chemotherapy, a vast majority of them are deemed ineligible for intensive chemotherapy. Multiple studies have also shown that poor performance status prior to treatment initiation affects the prognosis. An accurate comprehensive assessment is hence vital to the selection of such patients. The chemotherapy agents that have been used for AML in the medically unfit patients have also changed significantly in the past few years. In this review we focus on the importance of comprehensive geriatric assessment prior to chemotherapy initiation among patients who are 75 years and older and the treatment approaches available for the medically unfit, Acute Myeloid Leukemia patients.

CLAG-M chemotherapy followed by umbilical cord blood stem cell transplantation for primary refractory acute myeloid leukaemia in a child: A case report

BACKGROUND

The prognosis of paediatric primary refractory/relapsed acute myeloid leukaemia (R/R AML) remains poor. Intensive therapy is typically used as salvage treatment for those with R/R AML. No data are currently available about the use of the CLAG-M protocol as salvage therapy in paediatric patients with R/R AML.

CASE SUMMARY

An 8-year-old patient was diagnosed with acute myeloid leukaemia by bone marrow morphology and immunophenotype. The patient showed poor response to two cycles of induction therapy with 60% blast cells in the bone marrow after the second induction cycle. The patient achieved complete remission after being treated with the CLAG-M protocol as salvage therapy before undergoing umbilical cord blood stem cell transplantation. Morphological complete remission with haematological recovery has hitherto been maintained over 4 mo. Abnormal gene mutations detected at diagnosis were undetectable after haematopoietic stem cell transplantation.

CONCLUSION

Here we present a paediatric patient with primary refractory acute myeloid leukaemia who was successfully treated with the CLAG-M protocol. Given the positive results of the presented patient, large-scale clinical studies are required to assess the role of the CLAG-M protocol in the salvage treatment of refractory or relapsed AML in childhood.

Re-induction with modified CLAG regimen in relapsed or refractory acute myeloid leukemia in children bridging to allogeneic hematopoietic stem cell transplantation

BACKGROUND

The prognosis for relapsed or refractory acute myeloid leukemia (RR-AML) in children is poor, and the preferred salvage chemotherapy is unclear. One regimen is cladribine, cytarabine, and granulocyte-colony stimulating factor (CLAG), but little is known about its efficacy and safety in children with RR-AML.

METHODS

We enrolled RR-AML patients aged 0-18 years who received modified CLAG regimen for re-induction between July 1, 2015 and April 1, 2018, or conventional induction between August 1, 2011 and April 1, 2018. Patients were followed up to March 31, 2019. Patients underwent allogeneic stem cell transplantation (allo-SCT) or chemotherapy after the induction of complete remission (CR). The CR rate, survival, and side effects were analyzed.

RESULTS

The CR rate for induction was 66.7% after one cycle and 75.0% after two cycles of the CLAG regimen in 12 children. The nine children who received conventional chemotherapy had a CR rate of 22.2% after one cycle and 33.3% after two cycles (P = 0.087 vs. CLAG). The 3-year event-free survival (EFS) of the CLAG group and the conventional treatment group were 44.4 ± 15.7% and 22.2 ± 13.8% (P = 0.112). The 3-year overall survival of the two groups were 59.5 ± 16.2% and 22.2% ± 13.8% (P = 0.057). The 3-year EFS for allo-SCT and chemotherapy after CLAG regimen was 66.7 ± 19.2% and 25.0 ± 21.7% (P = 0.015). A single case of chemotherapy-related death was recorded.

CONCLUSION

Our data suggest a promising CR rate using CLAG salvage treatment in childhood RR-AML. Allo-SCT after CR may improve the long-term outcome in these patients.

Multiple Sclerosis and Cancer: The Ying-Yang Effect of Disease Modifying Therapies

Over the past two decades, the field of multiple sclerosis (MS) has been transformed by the rapidly expanding arsenal of new disease modifying therapies (DMTs). Current DMTs for MS aim to modulate innate and adaptive immune responses toward a less inflammatory phenotype. Since the immune system is also critical for identifying and eliminating malignant cells, immunosuppression from DMTs may predictably increase the risk of cancer development in MS patients. Compared with healthy controls, patients with autoimmune conditions, such as MS, may already have a higher risk of developing certain malignancies and this risk may further be magnified by DMT treatments. For those patients who develop both MS and cancer, these comorbid presentations create a challenge for clinicians on how to therapeutically address management of cancer in the context of MS autoimmunity. As there are currently no accepted guidelines for managing MS patients with prior history of or newly developed malignancy, we undertook this review to evaluate the molecular mechanisms of current DMTs and their potential for instigating and treating cancer in patients living with MS.

The role of cladribine in acute myeloid leukemia: an old drug up to new tricks

Despite advances in understanding the pathogenesis of acute myeloid leukemia (AML), the standard therapy remained nearly unchanged for several decades. There have been many efforts to improve the response and survival by either increasing the cytarabine (ARA-C) dose or adding a third agent to the standard chemotherapy regimen. Several studies have evaluated the addition of cladribine (CdA) to standard induction, exploiting its property to potentiate ARA-C uptake. Response rates for combination regimens including CdA in relapsed/refractory (R/R) adults are approximately 50% and approximately 70% in de novo AML. Recently, a low intensity combination of CdA and ARA-C alternating with decitabine has shown promising results in older patients with AML. In this review, we will discuss the role of CdA in the treatment of AML, summarizing the recent clinical data regarding its incorporation into the induction therapy for adult AML.

Efficacy and toxicity of cladribine for the treatment of refractory acute myeloid leukemia: a meta-analysis

Purpose: To investigate the overall efficacy and toxicity of cladribine and cladribine-based chemotherapy in the treatment of patients with refractory acute myeloid leukemia (AML) based on meta-analysis. Methods: PubMed, EMBASE database, and the Cochrane Library were searched for relevant studies. Eligible studies were clinical trials of refractory AML assigned to cladribine with data on efficacy including complete remission (CR) rate, overall response rate (ORR) and overall survival. Toxicity was evaluated based on the early death rate and the incidence of grade 3 and 4 adverse events (AEs). Results: A total of 10 clinical trials including 422 refractory AML patients were analyzed. The overall CR rate was 42.2% (95% CI: 31.0-54.3%). And the ORR of seven trials including 235 patients was 49.7% (95% CI: 33.5-66.0%). The overall early death rate of 260 patients enrolled in five trials was 6.8% (95% CI: 4.3-10.6%). Thrombocytopenia, anemia, neutropenia, and infection were the most common grade 3 and 4 AEs. Conclusion: Cladribine is effective for refractory AML, and its efficacy can be increased with the combination of cladribine, cytarabine, and granulocyte-colony stimulating factor regimen.

Cladribine and low-dose cytarabine alternating with decitabine as front-line therapy for elderly patients with acute myeloid leukaemia: a phase 2 single-arm trial

BACKGROUND

Front-line therapy for elderly or unfit patients with acute myeloid leukaemia (AML) remains unsatisfactory with poor outcomes and excessive toxicity. We studied a new low-intensity regimen of cladribine combined with low-dose cytarabine alternating with decitabine, aimed at improving outcomes in this population. Based on our previous experience, we hypothesised that this combination would be safe and more effective than current approaches with hypomethylating agents.

METHODS

In this single-arm, open-label, single-centre phase 2 study, we enrolled patients aged 60 years or older with previously untreated AML or high-risk myelodysplastic syndrome who had adequate organ function and an Eastern Cooperative Oncology Group performance status of 2 or less. Patients were treated with cladribine plus low-dose cytarabine for two 28-day cycles alternating with decitabine for two 28-day cycles, for up to 18 cycles. Induction therapy (cycle 1) consisted of cladribine 5 mg/m² intravenously over 1-2 h on days 1-5 and cytarabine 20 mg subcutaneously twice daily on days 1-10. Patients who had remission during this induction regimen moved on to consolidation therapy (cladribine 5 mg/m² intravenously over 1-2 h on days 1-3 and cytarabine 20 mg twice daily on days 1-10, alternating with decitabine 20 mg/m² intravenously on days 1-5). The primary outcome measure was disease-free survival. Secondary outcomes were overall survival, proportion of patients achieving complete response, proportion of patients achieving response, toxicity, and induction mortality. All treated patients were included in the analyses. This trial is ongoing and is registered with ClinicalTrials.gov, number NCT01515527.

FINDINGS

Between Feb 17, 2012, and July 6, 2017, 118 patients were enrolled and treated, among whom 48 (41%) had an adverse karyotype, 20 (17%) had therapy-related AML, 18 (15%) had treated secondary AML, and 20 (17%) had TP53 mutations. Median disease-free survival was 10·8 months (IQR 5·4-25·9). 80 (68%) patients achieved objective response: 69 (58%) achieved a complete response and 11 (9%) patients had complete response with incomplete count recovery. The median overall survival was 13·8 months (6·9-28·6). The regimen was well tolerated, with one (1%) death within the first 4 weeks and eight (7%) deaths within the first 8 weeks. The most common non-haematological adverse events of grade 3 or worse were infection (88 [75%] patients), elevated total bilirubin (26 [22%] patients), rash (13 [11%] patients), and nausea (13 [11%] patients).

INTERPRETATION

The combination of cladribine and low-dose cytarabine alternating with decitabine appears to be a safe and highly effective regimen for the treatment of elderly or unfit patients with newly diagnosed AML. Further testing of this regimen is warranted, and could help to provide a new, effective option for reduced-intensity therapy in this population.

FUNDING

Part supported by the National Institutes of Health.

Phase I and Phase II Objective Response Rates are Correlated in Pediatric Cancer Trials: An Argument for Better Clinical Trial Efficiency

Although many phase I trials report tumor response, formal analysis of efficacy is deferred to phase II. We reviewed paired phase I and II pediatric oncology trials to ascertain the relationship between phase I and II objective response rate (OR%). Single-agent phase I trials were paired with corresponding phase II trials (comparable study drug, dosing schedule, and population). Phase I trials without efficacy data or a matching phase II trial were excluded. OR% was tabulated for all trials, and phase II authors' subjective conclusions regarding efficacy were documented; 35 pairs of trials were analyzed. The correlation between phase I and II OR% was 0.93. Between phase II studies with a "positive" conclusion versus a "negative" one, there was a statistically significant difference in mean phase I OR% (32.0% vs. 4.5%, P<0.001). Thirteen phase II studies were undertaken despite phase I OR% of 0%; only 1 had a "positive" conclusion, and none exceeded OR% of 15%. OR% are highly correlated between phase I and II pediatric oncology trials. Although not a formal measure of drug efficacy, phase I OR% may provide an estimate of phase II response, inform phase II study design, and should be given greater consideration.

Clinical Characteristics and Treatment of Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) is a disease caused by clonal proliferation of CD1a+/CD207+ cells that is characterized by a spectrum of varying degrees of organ involvement and dysfunction. Treatment of LCH is risk adapted; patients with single lesions may respond well to local treatment, whereas patients with multi-system disease and risk-organ involvement require more intensive therapy. Although survival for patients without organ dysfunction is excellent, mortality rates for patients with organ dysfunction may reach 30% to 40%. For patients with low-risk disease, although cure is almost universal, disease reactivation rates are in excess of 30%.

Revisiting the role of cladribine in acute myeloid leukemia: an improvement on past accomplishments or more old news?

Originally studied in lymphoid diseases, cladribine (CdA) is an adenosine deaminase resistant analog of adenosine that was later discovered to induce myeloid cell apoptosis. The activity of CdA in myeloid malignancies was first reported in relapsed/refractory (RR) pediatric acute myeloid leukemia (AML) with complete response (CR) rates of up to 47%. Consequently, several studies have confirmed the efficacy of single agent CdA or CdA combination regimens in AML. Established CR rates for combination regimens in RR adults are approximately 50%, while CR rates for newly diagnosed (ND) adults are approximately 70% and show similar toxicity profiles to previously used regimens. Despite these promising data, many centers have yet to adopt CdA combination regimens for these difficult to treat populations. We review the pharmacology, pharmacokinetics, clinical data, and safety of CdA monotherapy and combination regimens for the management of pediatric and adult ND and RR-AML.

Relapsed and refractory pediatric acute myeloid leukemia: current and emerging treatments

Survival rates for children with acute myeloid leukemia (AML) exceed 60 % when modern, intensified chemotherapeutic regimens and enhanced supportive care measures are employed. Despite well-recognized improvements in outcomes, primary refractory or relapsed pediatric AML yields significant morbidity and mortality, and improved understanding of this obstinate population along with refined treatment protocols are urgently needed. Although a significant number of patients with refractory or relapsed disease will achieve remission, long-term survival rates remain poor, and efforts to identify therapies which will improve OS are under continuous investigation. The current fundamental goal of such investigation is the achievement of as complete a remission as possible without dose-limiting toxicities, and the progression to hematopoietic stem cell transplantation thereafter. In this review the scope of the problem of relapsed and refractory AML as well as current and emerging chemotherapy options will be discussed.

Older and new purine nucleoside analogs for patients with acute leukemias

Purine nucleoside analogs (PNAs) compose a class of cytotoxic drugs that have played an important role in the treatment of hematological neoplasms, especially lymphoid and myeloid malignancies. All PNA drugs have a chemical structure similar to adenosine or guanosine, and they have similar mechanisms of action. They have many intracellular targets: they act as antimetabolites, competing with natural nucleosides during DNA or RNA synthesis, and as inhibitors of key cell enzymes. In contrast to other antineoplastic drugs, PNAs act cytotoxically, both in the mitotic and quiescent cell cycle phases. In the last few years, three PNAs have been approved for the treatment of lymphoid malignancies and other hematological disorders: 2-chlorodeoxyadenosine (2-CdA), fludarabine and pentostatin. 2-CdA and fludarabine are also active in the treatment of acute myeloid leukemia (AML). These drugs, in combination with cytarabine and other agents, are commonly used as salvage regimens in relapsed or refractory AML. Moreover, the addition of 2-CdA to the standard induction regimen is associated with an increased rate of complete remission and improved survival of adult patients with AML. More recently three novel PNAs have been synthesized and introduced into clinical trials: clofarabine, nelarabine and forodesine. Clofarabine is the most promising PNA in current clinical trials in pediatric and adult patients with acute leukemias. Nelarabine is more cytotoxic in T-lineage than in B-lineage leukemias. Clofarabine and nelarabine have been approved for the treatment of refractory patients with acute lymphoblastic leukemia (ALL) and lymphoblastic lymphoma. Clofarabine is also an active drug in AML treatment when administered either alone or in combination regimens as front-line treatment and in relapsed or refractory patients. Unlike other PNA, forodesine is not incorporated into DNA but displays a highly selective purine nucleoside phosphorylase inhibitory action. Forodesine is undergoing clinical trials for the treatment of T-cell malignancies, including T-cell ALL. This article summarizes recent achievements in the mechanism of action, pharmacological properties and clinical activity and toxicity of PNAs, as well as their emerging role in lymphoid and myeloid acute leukemias.

A Practical Synthesis of 2-chloro-2′-deoxyadenosine (Cladribine) from 2′-deoxyadenosine

A practical synthesis of 2-chloro-2′-deoxyadenosine (Cladribine) from 2′-deoxyadenosine is reported. Treatment of fully protected 2′-deoxyadenosine with 2,2,2-trifluoroacetic anhydride and tetrabutylammonium nitrate gave protected 2-nitro-2′-deoxyadenosine with high yield. 2-Chloro-2′-deoxyadenosine was synthesised in four steps and 44.8% yield after substitution by chloride and deprotection steps.

Phase II study of 2-chlorodeoxyadenosine plus idarubicin for children with acute myeloid leukaemia in first relapse: a paediatric oncology group study

Relapse remains the leading cause of death in patients with acute myeloid leukaemia (AML). Relatively few new chemotherapy agents have been proven to be effective in this population. We report on a Phase 2 clinical trial using the novel combination of 2-chlorodeoxyadenosine (2-CDA) (8 mg/m² per d x 5 d) plus idarubicin (Ida) (10 mg/m² per d x 3 d). The study involved 109 paediatric patients with AML at first relapse, of whom 104 were available for analysis. The overall response rate was 51% (complete response [CR] + partial response) with a CR rate of 46%. 2-year event-free survival (EFS) and overall survival (OS) were 20% and 26%. The only significant variable in determining response, EFS and OS was duration of initial remission, with patients who had an initial remission >1 year having much worse outcomes overall (response rate 74% vs. 25%, EFS 8% vs. 37% and OS of 16% vs. 39%, P < 0.01 for all). There was an acceptable toxicity profile with one neurological event and no cardiac events observed. The most common grade 3-4 toxicities observed were neutropenia (59%) and thrombocytopenia (68%). This study demonstrated that the novel combination of 2-CDA/Ida was effective and should be considered for incorporation in front line therapy for children with AML.

A new synthesis of 2-chloro-2'-deoxyadenosine (Cladribine), CdA)

A new efficient route for the synthesis of 2-chloro-2';-deoxyadenosine (Cladribine), CdA) has been developed. The key step of this method was selective deprotection of the acetyl group at the 2' position; the 3', 5' acetyl groups were not affected. This can be accomplished efficiently with hydroxylamine hydrochloride and sodium acetate in pyridine. The 2' hydroxyl group was removed by the Barton-McCombie reaction. Using this strategy, CdA was prepared in five steps and 31.0% yields.

Systematic in-vitro evaluation of the NCI/NIH Developmental Therapeutics Program Approved Oncology Drug Set for the identification of a candidate drug repertoire for MLL-rearranged leukemia

Despite significant progress made in the overall cure rate, the prognosis for relapsed and refractory malignancies in children remains extremely poor. Hence, there is an urgent need for studies that enable the timely selection of appropriate agents for Phase I clinical studies. The Pediatric Oncology Experimental Therapeutics Investigators’ Consortium (POETIC) is systematically evaluating libraries of known and novel compounds for activity against subsets of high-risk pediatric malignancies with defined molecular aberrations for future clinical development. In this report, we describe the in-vitro activity of a diverse panel of approved oncology drugs against MLL-rearranged pediatric leukemia cell lines. Agents in the Approved Oncology Drug Set II (National Cancer Institute/National Institutes of Health Developmental Therapeutics Program) were evaluated by in-vitro cytotoxicity assays in pediatric acute lymphoblastic leukemia and acute myeloid leukemia cell lines with MLL gene rearrangements. Validation studies were carried out with patient leukemia cells in culture. Comparative analysis for toxicity against nonmalignant cells was evaluated in normal bone marrow stromal cells and normal human lymphocytes. Results from this study show that 42 of the 89 agents tested have measurable cytotoxicity against leukemia cells, and among these, 12 were effective against all five MLL-rearranged cell lines (IC₅₀ [half maximal inhibitory concentration] < 1 μM). These 12 agents include cladribine, dactinomycin, daunorubicin, docetaxel, etoposide, gemcitabine, mitomycin C, mitoxantrone, teniposide, topotecan, triethylenemelamine, and vinblastine. We show that the Approved Oncology Drug Set II contains a number of agents with potent antileukemic activity in the tested cell lines. As approved drugs, these agents have been used in clinical settings for many years for other malignancies, thus their toxicity profile, pharmacokinetics, and other properties are readily available. Further evaluation of their use in future clinical trials for pediatric leukemia with MLL abnormalities should be considered.

Combination of cladribine plus topotecan for recurrent or refractory pediatric acute myeloid leukemia

BACKGROUND

The prognosis after recurrence of pediatric acute myeloid leukemia (AML) is poor, and effective salvage regimens are urgently needed.

METHODS

In phase 1 and pilot studies, the authors evaluated the maximum tolerated dose (MTD) and dose-limiting toxicities (DLTs) of a 5-day course of cladribine followed by topotecan in pediatric patients with recurrent/refractory AML. The cladribine dose was escalated as follows: 9.1, 13.6, 16.3, and 19.5 mg/m(2) per day (8.9 mg/m(2) per day in the pilot study). Outcome was analyzed according to the absence (Stratum 1) versus presence (Stratum 2) of previous allogeneic hematopoietic stem cell transplantation. Twenty-six patients (20 in Stratum 1 and 6 in Stratum 2) were treated.

RESULTS

The MTD was not reached in Stratum 1, but a DLT occurred at the lowest cladribine dosage (9.1 mg/m(2) per day) in Stratum 2. Febrile neutropenia was common in both strata. Nine (34.6%) of 26 patients experienced a complete response, and 7 (30.4%) achieved a partial response; 5 (19.2%) were long-term survivors at the time of last follow-up. Clinical outcome was not associated with cladribine or topotecan systemic exposure.

CONCLUSIONS

The combination was well tolerated in Sratum 1, and the response rate was encouraging. This regimen offers a postrecurrence treatment alternative for patients, especially those who have received anthracycline-containing chemotherapy.

2'-Chlorodeoxyadenosine (2-CdA) as salvage therapy for Langerhans cell histiocytosis (LCH). results of the LCH-S-98 protocol of the Histiocyte Society

BACKGROUND

A prospective phase II Histiocyte Society study, LCH-S-98, evaluated the efficacy of 2-chlorodeoxyadenosine (2-CdA) monotherapy as salvage therapy in Langerhans cell histiocytosis (LCH).

PROCEDURES

Patients with poor and intermediate risk LCH not responsive to initial therapy and patients with low-risk chronic recurrent LCH were evaluated for response and survival after treatment with 2-6 courses of 2-CdA.

RESULTS

Forty-six patients (55%) had involvement of risk organs; lung, liver, spleen, or hematopoetic system (RO+), 37 (45%) were RO-. Twenty-two percent of RO+ patients had a good response while 44% progressed, 62% RO- patients responded, and 11% progressed. Two-year predicted survival is 48% for RO+, 97% for RO- patients, 100% for RO+ patients reactivating in non-risk organs, 67% for RO- patients reactivating in risk organs. Two-year pSU for the entire group is 68%. Seventy-three percent of patients with a poor response to 2-CdA died. Sixty-five percent patients >2 years old and 30% <2 years old survived. There was a median of 26 months from diagnosis to 2-CdA for responders compared to a median of 5 months for non-responders. Twenty-one percent of patients treated <12 months and 57% treated >12 months from diagnosis responded.

CONCLUSION

2-CdA is active in LCH. It produces a higher response rate in patients with low-risk multisystem or multifocal bone disease than those with risk organ involvement. "Risk" patients who fail to respond to 2-CdA have a high mortality. Patient age at 2-CdA therapy and length of time from diagnosis to 2-CdA significantly affect response and survival.

Infectious complications in patients with acute myeloid leukemia treated according to the protocol with daunorubicin and cytarabine with or without addition of cladribine. A multicenter study by the Polish Adult Leukemia Group (PALG)

OBJECTIVES

The addition of cladribine to the standard regimen consisting of daunorubicin and cytarabine has been reported to increase the efficacy of induction therapy in acute myeloid leukemia (AML). The goal of this study was to determine the effect of this modification on the incidence and spectrum of infectious complications.

METHODS

Case report forms of 309 patients with newly diagnosed AML who had been enrolled in the prospective, randomized 'DAC-7 vs. DA-7' trial were reviewed. The frequency, etiology, localization, severity, and outcome of infections were compared for patients receiving only daunorubicin and cytarabine (DA-7) and those additionally treated with cladribine (DAC-7).

RESULTS

A total of 443 febrile episodes were reported with no significant difference between the treatment groups. A trend towards a higher frequency of bacteremias was observed among DA-7 patients compared to those in the DAC-7 group (31% vs. 21%; p=0.08). The treatment arms did not differ in terms of the distribution of the isolated Gram-positive, Gram-negative, fungal, and viral organisms. However, when bacteremias were considered, Gram-positive blood cultures tended to be more frequent in the DA-7 compared to the DAC-7 group (16% vs. 8.5%; p=0.07). This difference reached statistical significance when major blood bacteremias were analyzed separately (13% vs. 5%; p=0.02). Complete recovery from infections was observed in the majority of patients across both treatment arms and no significant difference was noted regarding infection-related mortality.

CONCLUSIONS

The addition of cladribine to standard induction chemotherapy has no impact on the incidence and spectrum of infectious complications in newly diagnosed AML patients.

Treatment strategies for pediatric acute myeloid leukemia

Therapeutic strategies utilized in recently completed Phase III clinical trials in children with de novo acute myeloid leukemia have led to long-term disease-free survival in 50 - 60% of children. This review describes the contributions from early intensification of therapy and postremission intensification using highly myelosuppressive chemotherapy strategies and discusses the controversial roles of allogeneic bone marrow transplantation, maintenance therapy and CNS irradiation. Current strategies focusing on the identification of critical biologic features and measurements of early response to therapy allow for greatly improved risk group stratification. Future improvements in the treatment of children with acute myeloid leukemia will depend on a better understanding of the biology of the disease, targeted therapeutic approaches directed to specific biologic targets, selective use of allogeneic transplantation and innovative clinical trial designs that will allow for the testing of an increasing number of new agents in increasingly small numbers of patients in defined risk groups.

Combination of cladribine and cytarabine is effective for childhood acute myeloid leukemia: results of the St Jude AML97 trial

Because cladribine can increase cytarabine triphosphate levels, we tested a cladribine—cytarabine combination in the St. Jude AML97, trial in which this combination was administered before standard chemotherapy to 96 children with acute myeloid leukemia (AML) or myelodysplastic syndrome. Patients received a 5-day course of cladribine (9 mg/m²/dose) and cytarabine either as daily 2-hour infusions (500 mg/m²/dose) (arm A) or a continuous infusion (500 mg/m²/day) (arm B). Ara-CTP levels and inhibition of DNA synthesis increased from day 1 to day 2, but were not different between the two arms. In addition, the median blast percentages at day 15 did not differ between arms A and B, but patients treated in arm A had shorter intervals between the initiation of the first and second courses of therapy. Thus, although there were trends towards better CR rates and overall survival for patients treated in arm B, the reduced efficacy of arm A may have been partially compensated by more intense timing of therapy for that group. For all patients, 5-yr event-free survival and overall survival estimates were 44.1% ± 5.4 % and 50.0% ± 5.5%. Our results suggest that cladribine in combination with continuous-infusion cytarabine is effective therapy for childhood AML.

Prognostic factors and outcome of recurrence in childhood acute myeloid leukemia

BACKGROUND

Outcome after recurrence of childhood acute myeloid leukemia (AML) is poor. We performed this study to identify prognostic factors for recurrence and for survival after recurrence of AML.

METHODS

The clinical characteristics, biological features, treatment modalities, and outcomes of children with de novo AML who were enrolled on 3 consecutive clinical protocols from 1987 to 2002 at St. Jude Children's Research Hospital were studied. Regression modeling was used to identify prognostic factors for recurrence and for survival after recurrence.

RESULTS

The outcome after recurrence was poor, with a 5-year survival estimate of only 23.3% +/- 5.7%. Multivariable analysis indicated that male sex (P = .005), autologous stem cell transplant before recurrence (P = .097), each additional month from diagnosis to recurrence (P = .041), and stem cell transplant after recurrence (P < .001) were associated with a better survival after recurrence, whereas M5 or M7 morphology (P = .001) were significantly predictive of a lower survival estimate after recurrence.

CONCLUSIONS

Survival after recurrence was poor in children with AML. Novel therapies are urgently needed to prevent or to treat recurring AML.

Sinus histiocytosis with massive lymphadenopathy (Rosai-Dorfman disease) treated with 2-chlorodeoxyadenosine

Sinus histiocytosis with massive lymphadenopathy (SHML) or Rosai-Dorfman disease (RDD) is a rare but well-defined histiocytic proliferative disorder of unknown etiology that usually presents with cervical lymphadenopathy, fever, leukocytosis, and hypergammaglobulinemia in an otherwise healthy child. Although many patients undergo spontaneous remission, a subset of patients with systemic disease has a more serious course. For those patients with a poor outcome, steroids and chemotherapeutic agents such as etoposide or 6-mercaptopurine plus low dose methotrexate have been used. We present a child with a massive cervical lymphadenopathy treated with 2-chlorodeoxyadenosine (2-CdA, cladribine) after other approaches failed.

Regiospecific and Highly Stereoselective Coupling of 6-(Substituted-imidazol-1-yl)purines with 2-Deoxy-3,5-di-O-(p-toluoyl)-α-d-erythro-pentofuranosyl Chloride. Sodium-Salt Glycosylation in Binary Solvent Mixtures: Improved Synthesis of Cladribine1

Glycosylation of 6-(substituted-imidazol-1-yl)purine sodium salts with 2-deoxy-3,5-di-O-(p-toluoyl)-alpha-D-erythro-pentofuranosyl chloride proceeds with regiospecific formation of the N9 isomers. Base substrates with lipophilic substituents on the C6-linked imidazole moiety are more soluble in organic solvents, and the solubility is further increased with binary solvent mixtures. Selective solvation also diminishes the extent of anomerization of the chlorosugar. Stirred reaction mixtures of the modified-purine sodium salts generated in a polar solvent and cooled solutions of the protected 2-deoxysugar chloride in a nonpolar solvent give 2'-deoxynucleoside derivatives with N9 regiochemistry and enhanced beta/alpha configuration ratios. Application of the binary-solvent methodology with 2-chloro-6-(substituted-imidazol-1-yl)purine salts in cold acetonitrile and the chlorosugar in cold dichloromethane gives essentially quantitative yields of the N9 isomers of beta-anomeric 2'-deoxynucleoside intermediates. Direct ammonolysis (NH(3)/MeOH) of such intermediates or benzylation of the imidazole ring followed by milder ammonolysis of the imidazolium salt gives high yields of the clinical anticancer drug cladribine (2-chloro-2'-deoxyadenosine).

Efficacy and tolerability of gemtuzumab ozogamicin (anti-CD33 monoclonal antibody, CMA-676, Mylotarg) in children with relapsed/refractory myeloid leukemia

BACKGROUND

Gemtuzumab ozogamicin (GO) is a cytotoxic anti-CD33 monoclonal antibody that has given promising preliminary results in adult myeloid CD33+ AML. We conducted a retrospective multicenter study of 12 children treated with GO on a compassionate basis (median age 5.5 y). Three patients (2 MDS/AML, 1 JMML) were refractory to first-line treatment, 8 patients with de novo AML were in refractory first relapse, and one patient with de novo AML was in 2nd relapse after stem cell transplantation (SCT). CD33 expression exceeded 20% in all cases.

METHODS

GO was administered alone, at a unit dose of 3-9 mg/m2, once (3 patients), twice (3 patients), three (5 patients) or five times (1 patient). Mean follow-up was 128 days (8-585 d).

RESULTS

There were three complete responses (25%) leading to further curative treatment (SCT). Treatment failed in the other nine patients, and only one patient was alive at the end of follow-up. NCI-CTC grade III/IV adverse events comprised hematological toxicity (n = 12), hypertransaminasemia (n = 2), allergy and hyperbilirubinemia (1 case each). There was only one major adverse event (grade IV allergy). No case of sinusoidal obstruction syndrome occurred.

CONCLUSION

These results warrant a prospective trial of GO in a larger population of children with AML.

High activity and incomplete cross resistance of nucleoside analogues cladribine and fludarabine versus Ara-C on leukemic cells from patients with AML

The in vitro activity and cross-resistance pattern of the purine analogues cladribine and fludarabine and the pyrimidine analogue cytarabine on leukemic cells from 170 patients with AML was evaluated using a bioluminescence assay. In in vivo mimicking concentrations, cladribine (50 nmol/L) and fludarabine (2 micromol/L) were more cytotoxic than cytarabine (0.5 micromol/L). The cytotoxic effect of fludarabine correlated weakly to cytarabine (r = 0.37, P < 0.001). The cytotoxic effect of cladribine correlated better to cytarabine (r = 0.49, P = 0.0002) but best to fludarabine (r = 0.82, P < 0.001). There was an absence of correlation between either cladribine or fludarabine and daunorubicin (0.2 micromol/L). Of 45 highly Ara-C-resistant samples, cladribine exerted high or intermediate effect in 54% and fludarabine in 52%. These in vitro data indicate that cladribine and fludarabine are active drugs in the treatment of AML. The cross resistance to cytarabine was not complete, and the drugs can be valuable either as alternatives to Ara-C or in combination therapy for treatment of leukemia resistant to standard therapy.

Long-term analysis of the palliative benefit of 2-chlorodeoxyadenosine for myelofibrosis with myeloid metaplasia

OBJECTIVE

Therapeutic splenectomy in myelofibrosis with myeloid metaplasia (MMM) may result in extreme thrombocytosis and leukocytosis and accelerated hepatomegaly. We previously described initial palliative benefit from 2-chlorodeoxyadenosine (2-CdA) in such instances. The purpose of this study is to provide long-term follow-up on the durability of response in the initial cohort and in additional subsequent cases.

METHODS

We retrospectively identified patients with histologically confirmed MMM who had palliative therapy with 2-CdA. Clinical characteristics and information on subsequent clinical course were abstracted at the time of diagnosis of MMM and at initiation of 2-CdA therapy until death.

RESULTS

To date, we have used 2-CdA as palliative therapy in 14 patients with MMM. After a median of four cycles of therapy, responses for hepatomegaly occurred in 56% of patients, thrombocytosis 50%, leukocytosis 55%, and anemia 40%. Cytopenias were frequent but usually transient and without clinical consequence. Responses occurred usually by the second cycle; median duration of response was 6 months (range, 2-19) after completion of 2-CdA therapy.

CONCLUSION

This study confirmed relevant and frequently durable palliation of symptoms in about half the patients. 2-CdA is a reasonable palliative option in postsplenectomy patients with MMM who have problematic myeloproliferation.

Possibilities for tailored and targeted therapy in paediatric acute myeloid leukaemia

The clinical outcome of acute myeloid leukaemia (AML) in children has improved considerably using intensive chemotherapy and/or stem cell transplantation. This leads to cure in 50-70% of patients, and also results in significant morbidity and mortality. Hence, we need other ways to improve the cure rate. This review discusses possibilities for tailored therapy, reviewing in vitro cellular drug sensitivity data. The results provide suggestions regarding the adaptation of clinical protocols in certain AML subgroups, although further clinical studies will show whether this is effective. Secondly, we review type 1 genetic abnormalities (such as receptor tyrosine kinase mutations) that result in enhanced survival and proliferation of leukaemic cells, which can be detected in approximately 50% of paediatric AML samples, and are non-randomly associated with French-American-British type and cytogenetic subgroups. FLT3 internal tandem duplication is associated with poor clinical outcome, and may be used for risk-group stratification. The first results with small molecule inhibitors in adult AML do not suggest their use in children as yet. International collaboration is needed to further improve outcome by developing treatment protocols for subgroups of paediatric AML.

Phase II trial of cladribine and cytarabine in relapsed or refractory myeloid malignancies

To evaluate the efficacy of cladribine and cytarabine in children with relapsed or refractory myeloid malignancies, we administered cytarabine (200 mg/m2 per day) by continuous subcutaneous infusion and cladribine (8.9 mg/m2 per day) by continuous intravenous infusion concomitantly for 5 days to nine patients younger than 21 years. After one course, five patients had no response, two patients had partial responses, one had stable disease, and one had progressive disease. Two patients received a second course: one patient had stable disease after one course and progressive disease after the second; another patient had a partial response after one course and no response after the second. Despite the efficacy of the cladribine and cytarabine regimen in treating newly diagnosed acute myeloid leukemia (AML) in a previously reported study, the combination was not effective for relapsed or refractory childhood AML.

Addition of cladribine to daunorubicin and cytarabine increases complete remission rate after a single course of induction treatment in acute myeloid leukemia. Multicenter, phase III study

To assess the efficacy of an original DAC-7 regimen: daunorubicine (DNR) 60 mg/m2/day, days 1-3; cytarabine (AraC) 200 mg/m2/day, days 1-7; cladribine (2-CdA) 5 mg/m2/day, days 1-5, 400 untreated adult acute myeloid leukemia patients (including 63 with preceding myelodysplastic syndrome), aged 45 (16-60) years were randomized to either DAC-7 (n=200) or DA-7 (without 2-CdA, n=200). The overall CR rate equaled 72% for DAC-7 and 69% for DA-7 arm (P=NS). After a single course of DAC-7 induction, the CR rate equaled 64% and was significantly higher compared to 47% in the DA-7 arm (P=0.0009). Median hospitalization time during the induction was 7 days shorter for DAC-7 compared to the DA-7 group (33 vs 40 days, P=0.002). Toxicity was comparable in both groups. The probability of 3-year leukemia-free survival (LFS) for DAC-7 and DA-7 group equaled 43 and 34%, respectively (P=NS). There was a trend toward higher LFS rate for patients aged >40 years receiving DAC-7 compared with DA-7 regimen (44 vs 28%, P=0.05). This study proves that addition of 2-CdA increases antileukemic potency of DNR+AraC regimen, thus resulting in a higher CR rate after one induction cycle when compared to DA-7, without additional toxicity. It shortens hospitalization time and may improve long-term survival in patients aged >40 years.

Increased remissions from one course for intermediate-dose cytosine arabinoside and idarubicin in elderly acute myeloid leukaemia when combined with cladribine. A randomized population-based phase II study

Cladribine has single-drug activity in acute myeloid leukaemia (AML), and may enhance the formation of the active metabolite (ara-CTP) of cytosine arabinoside (ara-C). To evaluate the feasibility of adding intermittent cladribine to intermediate-dose ara-C (1 g/m2/2 h) b.i.d. for 4 d with idarubicin (CCI), we performed a 2:1 randomized phase II trial in AML patients aged over 60 years. Primary endpoints were time to recovery from cytopenia and need for supportive care following the first course. Sixty-three patients (median 71 years, range 60-84 years) were included, constituting 72% of all eligible patients. Toxicity was limited, with no differences between the treatment arms. The early toxic death rate was 11%. The median time to recovery from neutropenia and thrombocytopenia was 22 and 17 d from the start of course no. 1, respectively, and the requirement for platelet and red cell transfusions was four and eight units respectively. Patients had a median of 8 d with fever over 38 degrees C, and 17 d with intravenous antibiotic treatment. The overall complete remission (CR) rate was 62%, with 51% CR from one course of CCI in comparison with 35% for the two-drug therapy (P = 0.014). The median survival with a 2-year follow-up was 14 months, and the 2-year survival was over 30%, with no differences between the treatment arms. Considering the median age and our population-based approach, the overall results are encouraging.

Clofarabine, a novel nucleoside analog, is active in pediatric patients with advanced leukemia

Despite progress in leukemia therapy, most children who experience relapse have a dismal prognosis. New, effective approaches are needed. We conducted a phase 1 study of a novel nucleoside analog, clofarabine, in pediatric patients with refractory and relapsed leukemia. Clofarabine was infused intravenously over 1 hour each day for 5 days. Six dose levels, between 11.25 and 70 mg/m(2) per day for 5 days, were studied in 25 patients. A modified 3 + 3 phase 1 design was followed with 30% dose escalation until the dose-limiting toxicity (DLT) was defined. The maximum tolerated dose (MTD) was 52 mg/m(2) per day for 5 days. At the end of infusion at MTD, clofarabine triphosphate levels in leukemia blasts varied between 6 microM and 19 microM, which resulted in complete and sustained inhibition of DNA synthesis. The DLT was reversible hepatotoxicity and skin rash at 70 mg/m(2) per day for 5 days. Twenty-five patients were treated. Five patients achieved complete remission (CR), and 3 achieved partial remission (PR), for an overall response rate of 32%. Clofarabine is well tolerated and shows significant antileukemic activity in heavily pretreated children. Multicenter phase 2 trials in pediatric acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) are ongoing.

Mitoxantrone and cytarabine induction, high-dose cytarabine, and etoposide intensification for pediatric patients with relapsed or refractory acute myeloid leukemia: Children's Cancer Group Study 2951

PURPOSE

To evaluate the response rate, survival, and toxicity of mitoxantrone and cytarabine induction, high-dose cytarabine and etoposide intensification, and further consolidation/maintenance therapies, including bone marrow transplantation, in children with relapsed, refractory, or secondary acute myeloid leukemia (AML). To evaluate response to 2-chlorodeoxyadenosine (2-CDA) and etoposide (VP-16) in patients who did not respond to mitoxantrone and cytarabine.

PATIENTS AND METHODS

Patients with relapsed/refractory AML (n = 101) and secondary AML (n = 13) were entered.

RESULTS

Mitoxantrone and cytarabine induction achieved a remission rate of 76% for relapsed/refractory patients and 77% for patients with secondary AML, with a 3% induction mortality rate. Cytarabine and etoposide intensification exceeded the acceptable toxic death rate of 10%. The response rate of 2-CDA/VP-16 was 8%. Two-year overall survival was estimated at 24% and was better than historical control data. Patients with secondary AML had similar outcomes to relapsed or refractory patients. Initial remission longer than 1 year was the most important prognostic factor for patients with primary AML (2-year survival rate, 75%), whereas for patients with primary AML, with less than 12 months of initial remission, survival was 13% and was similar to that of refractory patients (6%).

CONCLUSION

Mitoxantrone and cytarabine induction is effective with reasonable toxicity in patients with relapsed/refractory or secondary AML. The cytarabine and etoposide intensification regimen should be abandoned because of toxicity. Patients with relapsed AML with initial remissions longer than 1 year have a relatively good prognosis.

Cladribine in the treatment of hairy-cell leukaemia

Cladribine, a purine nucleoside analogue, is a safe and effective treatment for patients with hairy-cell leukaemia. It is administered at a dose of 0.09 mg/kg daily as a continuous intravenous infusion over 7 days. This chapter discusses the history, rationale, chemical structure and mechanism of action of cladribine. The indications for therapy and guidelines for clinical usage are reviewed. The response of hairy-cell leukaemia to cladribine, the acute and chronic complications and the risk for second malignancies are summarized. The chapter concludes with a section on salvage therapy.

Purine nucleoside analogues in the treatment of myleoid leukemias

The purine nucleoside analogues (PNA), fludarabine (FA), cladribine (2-chlorodeoxyadenosine, 2-CdA) and 2'-deoxycoformycin (DCF), represent a novel group of cytotoxic agents with high activity in low-grade lymphoid malignancies. However, several investigations have revealed that these agents are active also in acute myeloid leukemia (AML) and chronic myelogenous leukemia (CML). Synergistic interaction between FA or 2-CdA with cytarabine (Ara-C) have been demonstrated in both preclinical and clinical studies. PNA enhance the cell concentration of Ara-CTP, which is active metabolite of Ara-C. It is likely that the addition of granulocyte colony stimulating factor (G-CSF) may further improve the effects of FA (FLAG) or 2-CdA (CLAG). The addition of anthracyclines to induction therapy does not appear to result in a substantial advantage in terms of CR achievement and duration. An alternative approach to increase FLAG activity might be the addition of investigational drugs with novel mechanism of action, such as topoiromerase I inhibitors. The addition of anthracyclines to induction therapy does not appear to result in a substantial advantage in terms of CR achievement and duration. Clinical studies have confirmed the efficacy of PNA alone or in combination protocols in the treatment of AML. These regimens seem to produce superior results with acceptable toxicities in previously treated and relapsed, poor risk AML. However, early relapses remain a significant problem in a majority of refractory or relapsed patients in CR after treatment with PNA based regimens. To prolong remission duration or even cure AML, auto--or allo stem cell transplantation should be considered. However, FAMP or 2-CdA containing regimens may impair mobilization and collection of stem cells from peripheral blood for autotransplantation. Few studies have analyzed the role of PNA in CML. 2-CdA, FAMP and DCF can induce hematologic response in chronic phase of CML but cytogenetic responses have not been observed. Preliminary results suggest, that PNA used alone or in combination may be used as palliation in blast phase of the disease. However, currently, the role of these agents in CML is insignificant because of the high activity of Glivec in this disease. Finally, PNA, especially FA play an important role in non-myeloablative conditioning regimens for allogenic stem cell transplantation in high-risk patients, possibly also with myeloid malignancies.

2-Chlorodeoxyadenosine therapy for disseminated Langerhans cell histiocytosis

OBJECTIVE

To evaluate the efficacy of 2-chlorodeoxyadenosine (2-CDA), a purine nucleoside analogue, in treating disseminated Langerhans cell histiocytosis (LCH).

PATIENTS AND METHODS

We retrospectively reviewed the clinical records of 5 patients who were seen at our institution for histologically confirmed disseminated LCH, including 1 patient with central nervous system parenchymal involvement. These patients were treated consecutively with 2-CDA chemotherapy between December 1994 and January 2001. The patients ranged in age from 19 to 81 years, and the median pretreatment duration of disease was 23 months. Median follow-up after initiation of 2-CDA treatment was 33 months. 2-Chlorodeoxyadenosine was used as frontline therapy for 1 patient and as salvage therapy for the other patients. Patients generally received 0.7 mg/kg over 5 or 7 days; the median number of courses was 4.

RESULTS

Complete responses were achieved in 3 patients, including the patient with central nervous system disease, which, to our knowledge, has not been described previously. Two other patients achieved partial responses. The overall response rate was 100%. Toxic effects consisted mainly of myelosuppression; 1 patient developed dermatomal herpes zoster infection.

CONCLUSION

Our experience confirms the reported efficacy of 2-CDA in the treatment of LCH; however, the optimal timing and schedule of therapy remain to be determined.

Pharmacokinetics of 2-chlorodeoxyadenosine in a child undergoing hemofiltration and hemodialysis for acute renal failure

The clearance of 2-chlorodeoxyadenosine (2-CdA) in patients with renal insufficiency has not been characterized previously. The authors describe the clinical course and the pharmacokinetics of 2-CdA in a child with acute monoblastic leukemia who experienced acute renal failure during treatment with cytarabine and 2-CdA. 2-CdA (9 mg/m per day) was infused over 30 minutes daily for 5 days. Plasma and dialysate concentrations of 2-CdA were measured by high-performance liquid chromatography. The rate of this patient's 2-CdA clearance was lower than the rates reported for children with normal renal function. The average clearance rate, reflecting systemic clearance and clearance by continuous venovenous hemofiltration and hemodialysis, was 12.4 L/hour per m for the first 3 days of 2-CdA therapy. He did not experience untoward hematologic toxicity. Because high 2-CdA plasma concentrations were observed in this patient, clinicians are advised to exercise caution when using this drug in patients with renal dysfunction. More experience in the administration of 2-CdA to patients with renal insufficiency will be necessary to determine the need for dosage adjustment.