In Vivo Cytotoxic, Genotoxic and Radiosensitizing Effects of Clofarabine.

BACKGROUND/AIM: ClFdA is a second-generation antineoplastic agent that has demonstrated significant anticancer activity, particularly against acute lymphoblastic leukemia and has been shown to have radiosensitizing activity. The aim of the study was to explore the genotoxic, cytotoxic and radiosensitizing effects of clofarabine (ClFdA) on bone marrow cells (BMCs), normoblasts and leukocytes of mice in vivo. MATERIALS AND METHODS: Cytotoxicity was determined by the reduction in reticulocytes (RET), and genotoxicity was determined by the induction of micronucleated reticulocytes (MN-RET) in the peripheral blood and by DNA break induction in leukocytes determined by single-cell gel electrophoresis (SCGE). The radiosensitizing capacity of ClFdA was determined in leukocytes and BMCs by SCGE. RESULTS: Two mechanisms of MN-RET induction were identified according to the antecedents, that could be due to inhibition of DNA synthesis and demethylation of G-C regions, and subsequent chromosome fragility. ClFdA cytotoxicity causes two contiguous peaks, an early peak that seems to inhibit MN-RET induction and a second peak that seems to be caused by ribonucleotide reductase (RR) and/or DNA synthesis inhibitions. ClFdA induced early DNA damage in noncycling leukocytes, and also radiosensitizes leukocytes immediately after treatment. ClFdA-ionizing radiation (IR) causes two time-dependent episodes of DNA damage, the latest after 80 min triggers a major breakage of DNA. In terms of the number of damaged cells, leukocytes and BMCs are similarly sensitive to ionizing radiation; BMCs are slightly more sensitive than leukocytes to ClFdA, but BMCs are doubly sensitive to combined treatment. CONCLUSION: ClFdA causes early DNA damage and radiosensitivity in non-proliferating leukocytes, which rules out the most favored hypotheses of the participation of RR and DNA polymerase inhibition.

Safety and effectiveness of clofarabine in Japanese patients with relapsed/refractory acute lymphoblastic leukaemia: a post-marketing surveillance study.

OBJECTIVE: Clofarabine is used to treat acute lymphoblastic leukaemia, but evidence of its safety and effectiveness in Japanese patients is limited. We evaluated the safety and effectiveness of clofarabine in patients with relapsed/refractory acute lymphoblastic leukaemia in real-world clinical practice in Japan. METHODS: An observational, multicenter, post-marketing, all-case surveillance was conducted for safety. Effectiveness analyses were conducted in patients aged ≤21 years and those treated with clofarabine monotherapy and combination therapy (clofarabine plus etoposide and cyclophosphamide). RESULTS: In the all-case survey, 260 of 264 registered patients were eligible for safety analysis. Among the 225 patients eligible for effectiveness analysis, 139 were aged ≤21 years. For monotherapy and combination therapy, 20/31 and 34/88 patients were eligible, respectively. In the all-case survey, the median age was 16.0 years, and 47.7% of patients were <15 years old. Adverse drug reaction incidence was 83.5% and the most common were hematologic toxicities. The best overall response rates in the population aged ≤21 years were complete remission, 29.7%; complete remission without platelet recovery, 7.3% and partial remission, 10.9%. The rest (52.2%) were classified as ineffective. The sum of complete remission, complete remission without platelet recovery and partial remission rates (effectiveness rate) was 47.8% (66/138 patients). The effectiveness rates in the monotherapy and combination therapy surveys were 10.0% (2/20 patients) and 58.8% (20/34 patients), respectively. CONCLUSIONS: These post-marketing surveys provide real-world evidence of the safety and effectiveness of clofarabine regimens, including monotherapy and combination therapy in Japanese patients with relapsed/refractory acute lymphoblastic leukaemia. The safety and effectiveness profiles were comparable with those of previous prospective studies.

Clofarabine monotherapy in aggressive, relapsed and refractory Langerhans cell histiocytosis.

Over 50% of patients with systemic LCH are not cured with front-line therapies, and data to guide salvage options are limited. We describe 58 patients with LCH who were treated with clofarabine. Clofarabine monotherapy was active against LCH in this cohort, including heavily pretreated patients with a systemic objective response rate of 92.6%, higher in children (93.8%) than adults (83.3%). BRAFV600E+ variant allele frequency in peripheral blood is correlated with clinical responses. Prospective multicentre trials are warranted to determine optimal dosing, long-term efficacy, late toxicities, relative cost and patient-reported outcomes of clofarabine compared to alternative LCH salvage therapy strategies.

Nelarabine-containing salvage therapy and conditioning regimen in transplants for pediatric T-cell acute lymphoblastic leukemia and lymphoma.

Therapy for relapsed or refractory (r/r) T-cell acute lymphoblastic leukemia (T-ALL) and T-cell lymphoblastic lymphoma (T-LBL) in children is challenging, and new treatment methods are needed. We retrospectively analyzed eight patients with r/r T-ALL (five patients) and T-LBL (three patients) who were treated with nelarabine (NEL) plus etoposide, cyclophosphamide, and intrathecal therapy, administered 3 days apart. Five patients achieved a complete response, and the other three achieved a partial response (PR). All patients underwent hematopoietic stem cell transplantation (HSCT) after two cycles of treatment, except for one patient who received one cycle. Three patients who had previously received HSCT were treated with reduced-intensity conditioning regimens, including fludarabine, melphalan, and NEL; one survived for over 5 years after the second HSCT. Grade 2 neuropathy occurred in one patient, but other severe toxicities commonly associated with NEL were not observed during NEL administration in combination with chemotherapy. The 2-year overall survival and event-free survival rates were 60.0% and 36.5%, respectively. The addition of NEL to reinduction chemotherapy was useful in achieving remission and did not lead to excessive toxicity. In addition, a conditioning regimen, including NEL, appeared to be effective in patients who had previously undergone HSCT.

Management of Nelarabine induced neurotoxicity in a child with T-cell acute lymphoblastic lymphoma.

INTRODUCTION: Nelarabine is now increasingly being used for the treatment of relapsed T-cell acute lymphoblastic leukemia/lymphoma, and about 18% of patients experience ≥ grade 3 toxicity. Despite the increasing use of this drug, there are no guidelines for managing its neurotoxicity. We would like to share our experience with one such case. CASE REPORT: A sixteen-year-old girl with T-lymphoblastic lymphoma received Nelarabine as part of her relapse treatment. Three weeks post-treatment, patient presented with worsening encephalopathy, bulbar palsy, and seizures. MANAGEMENT AND OUTCOME: After a detailed evaluation, Nelarabine neurotoxicity was strongly considered and was managed with a combination of steroids, intravenous immunoglobulin, and aminophylline, with almost complete recovery starting at 72 hours of treatment initiation. DISCUSSION: Despite the increasing use of this drug, guidelines for the management of the neurological adverse effects of Nelarabine are lacking. The above-mentioned combination of drugs worked for our patient, but larger numbers are needed to validate this as an approved treatment regimen.

The role of nelarabine in the treatment of T-cell acute lymphoblastic leukemia/lymphoma: challenges, opportunities, and future directions.

INTRODUCTION: Nelarabine is a guanine nucleoside analog and functions to terminate DNA synthesis in dividing cells. Pre-clinical and clinical studies have shown that it preferentially accumulates in T-cells where it exerts its cytotoxic effects. After generations of treatment protocol advances, it has been incorporated into numerous treatment regimens against T-lineage acute lymphoblastic leukemia/lymphoma (T-ALL/LLy). On 8 March 2023, the FDA approved the use of nelarabine for its use in T-ALL due to clear evidence of clinical benefits. This announcement concludes a nearly 6-decade period of evaluation for nelarabine and its role in the management of high-grade, aggressive T-cell malignancies. AREAS COVERED: We review the medicinal biology of nelarabine, its evaluation through decades of clinical studies, its dose-limited adverse effects, and its areas of highest impact in the treatment of T-ALL/LLy. EXPERT OPINION: We provide a context of when nelarabine might be considered in treatments against T-ALL/LLy, and also alternative strategies when it has or has not been used in therapies prior to relapse. We anticipate that an increasing number of treatment regimens will include nelarabine as a part of front-line therapy.

Would the choice of multiplex platform impact the management of the allergic patient? A first approach focusing on LTPs.

BACKGROUND: In the Mediterranean area, patients with LTP syndrome who are sensitized to multiple allergens are often tested for sIgE using multiplex platforms. The results obtained from different commercial platforms are not interchangeable, so it is important to compare and validate the platform selected for use. The objective of this study is to compare and validate the performance of the ImmunoCAP ISAC E112i and the macroarray ALEX2 in our daily practice. METHODS: From August 2021 to March 2022, we tested 20 random serum samples from polysensitized patients using the ALEX2 test (MADx) and ImmunoCAP tIgE and ISAC E112i (Thermo Fisher Scientific). We compared the total IgE (tIgE) and sIgE levels for shared allergens. RESULTS: The heatmap generally showed more intense results for ISAC. The overall correlation was good, but some exceptions were noted. The main discrepancies were found for Ole e 7, which was positive for 11 patients in ISAC but negative for all patients in ALEX2, and for nut LTPs, for which ISAC showed a threefold higher detection rate for Ara h 9 and a fivefold higher detection rate for Cor a 8 and Jug r 3 compared to ALEX2. The regression model showed no interchangeability of tIgE results. CONCLUSIONS: Despite our small sample size and the complexity of comparing a quantitative and a semi-quantitative platform, our results suggest that patient diagnosis and management can be influenced by the platform used. Therefore, our findings must be taken into consideration when choosing a platform to use for some profiles of LTP-polysensitized patients, even though more data is needed.

Enzymatic Synthesis of 2-Chloropurine Arabinonucleosides with Chiral Amino Acid Amides at the C6 Position and an Evaluation of Antiproliferative Activity In Vitro.

A number of purine arabinosides containing chiral amino acid amides at the C6 position of the purine were synthesized using a transglycosylation reaction with recombinant E. coli nucleoside phosphorylases. Arsenolysis of 2-chloropurine ribosides with chiral amino acid amides at C6 was used for the enzymatic synthesis, and the reaction equilibrium shifted towards the synthesis of arabinonucleosides. The synthesized nucleosides were shown to be resistant to the action of E. coli adenosine deaminase. The antiproliferative activity of the synthesized nucleosides was studied on human acute myeloid leukemia cell line U937. Among all the compounds, the serine derivative exhibited an activity level (IC50 = 16 µM) close to that of Nelarabine (IC50 = 3 µM) and was evaluated as active.

Nelarabine-induced myelopathy in patients undergoing allogeneic hematopoietic cell transplantation: a report of three cases.

Nelarabine is an effective treatment for T-cell acute lymphoblastic leukemia/lymphoma. Myelopathy is a rare but serious adverse event associated with this drug. Three patients who received nelarabine at the National Cancer Center Hospital from December 2014 to March 2021 developed myelopathy 20 days before, 12 days after, and 29 days after allogeneic hematopoietic cell transplantation (allo-HCT), respectively. Magnetic resonance imaging showed that two of the patients had lesions in the dorsal column or medulla oblongata, and one had no abnormalities in the head or spine. Despite treatment with intravenous immunoglobulin and methylprednisolone, all patients became unable to walk. One patient died on day 101 after allo-HCT due to progressive neurotoxicity. The other two patients showed spontaneous improvement in neurological symptoms, but one died of mucormycosis on day 476. Autopsy revealed spongiosis in the posterior funiculus in both patients who died, and also in the medulla oblongata in one patient. In the surviving patient, positron emission tomography on day 84 showed abnormal accumulation, suggesting continued inflammation. These cases demonstrated pathophysiological features of nelarabine-induced myelopathy and indicate that allo-HCT may worsen the condition. It is necessary to elucidate the underlying mechanism and establish diagnostic methods and therapies.

Central nervous system neurotoxicity associated with nelarabine in T-cell acute lymphoblastic leukemia.

INTRODUCTION: Nelarabine, a prodrug of arabinosylguanine has lineage-specific toxicity for T lymphoblasts and is used to treat refractory or relapsed T-cell acute lymphoblastic leukemia and T-cell lymphoblastic lymphoma patients. The most commonly observed adverse effects associated with nelarabine are mainly hematological, i.e. neutropenia, anemia, and thrombocytopenia. Additionally, neurological, and gastrointestinal toxicities have been reported. Central nervous system neurotoxicity associated with nelarabine is very rare. CASE DESCRIPTION: A 37-year-old man patient diagnosed with T-cell acute lymphoblastic leukemia had experienced generalized tonic-clonic seizure which lasted for a few seconds and upper extremity weakness after three weeks of the nelarabine infusion. Computed tomography and magnetic resonance imaging have shown periventricular and nucleus caudatus abnormalities. Radiological findings suggested toxic leukoencephalopathy and acute infarct of right nucleus caudatus. MANAGEMENT AND OUTCOME: After high-dose steroids, intravenous immunoglobulin, and support treatment, his neurologic symptoms disappeared except for mild peroral numbness. However, radiological sequelae persisted despite clinical improvement. CONCLUSION: Physicians involved in the care of these patients who use nelarabine should be aware of the fact that cerebral toxicity of the nelarabine may occur especially in the presence of predisposing factors. It is crucial to monitor closely those patients receiving nelarabine and also those who have additional predisposing factors for neurotoxicity.

A phase 1 study to evaluate the safety, pharmacology, and feasibility of continuous infusion nelarabine in patients with relapsed and/or refractory lymphoid malignancies.

BACKGROUND: Nelarabine is a purine nucleoside analogue prodrug approved for the treatment of relapsed and refractory T-cell acute lymphoblastic leukemia (R/R T-ALL) and lymphoblastic lymphoma (T-LBL). Although effective in R/R T-ALL, significant neurotoxicity is dose-limiting and such neurotoxicity associated with nucleoside analogues can be related to dosing schedule. METHODS: The authors conducted a phase 1 study to evaluate the pharmacokinetics and toxicity of nelarabine administered as a continuous infusion (CI) for 5 days (120 hours), rather than the standard, short-infusion approach. RESULTS: Twenty-nine patients with R/R T-ALL/LBL or T-cell prolymphocytic leukemia (T-PLL) were treated, with escalating doses of nelarabine from 100 to 800 mg/m2 /day × 5 days. The median age of the patients was 39 years (range, 14-77 years). The overall response rate was 31%, including 27% complete remission (CR) or CR with incomplete platelet recovery (CRp). Peripheral neuropathy was observed in 34% of patients, including four ≥grade 3 events related to nelarabine. Notably, there was no nelarabine-related central neurotoxicity on study. The maximum tolerated dose was not reached. Pharmacokinetic data suggested no relationship between dose of nelarabine and accumulation of active intracellular ara-GTP metabolite. Higher intracellular ara-GTP concentrations were statistically associated with a favorable clinical response. CONCLUSION: Preliminary evaluation of continuous infusion schedule of nelarabine suggests that the safety profile is acceptable for this patient population, with clinical activity observed even at low doses and could broaden the use of nelarabine both as single agent and in combinations by potentially mitigating the risk of central nervous system toxicities.

Imaging Findings in Children Presenting with CNS Nelarabine Toxicity.

Nelarabine is a nucleoside analog critical for the treatment of patients with T-cell acute lymphoblastic leukemia/lymphoma. However, clinical peripheral and central neurologic adverse events associated with nelarabine administration have been reported. Neuroimaging of brain neurotoxicity has only been described in very few reports in pediatric patients so far. Six children with diagnosed T-cell acute lymphoblastic leukemia who clinically experienced possible, probable, or definite nelarabine-induced toxicity and underwent spine and/or brain MR imaging were reviewed. Neuroimaging findings showed a mixture of patterns including features of acute toxic leukoencephalopathy (seen in 6 cases), posterior reversible encephalopathy syndrome (2 cases), involvement of deep gray structures (1 case) and brainstem (2 cases), cranial and spinal neuropathy (2 cases each), and myelopathy (2 cases). Even though neuroimaging findings are nonspecific, the goal of this article was to alert the pediatric neuroradiologists, radiologists, and clinicians about the possibility of nelarabine-induced neurotoxicity and its broad neuroimaging spectrum.

Rational Design of a Thermostable 2'-Deoxyribosyltransferase for Nelarabine Production by Prediction of Disulfide Bond Engineering Sites.

One of the major drawbacks of the industrial implementation of enzymatic processes is the low operational stability of the enzymes under tough industrial conditions. In this respect, the use of thermostable enzymes in the industry is gaining ground during the last decades. Herein, we report a structure-guided approach for the development of novel and thermostable 2'-deoxyribosyltransferases (NDTs) based on the computational design of disulfide bonds on hot spot positions. To this end, a small library of NDT variants from Lactobacillus delbrueckii (LdNDT) with introduced cysteine pairs was created. Among them, LdNDTS104C (100% retained activity) was chosen as the most thermostable variant, displaying a six- and two-fold enhanced long-term stability when stored at 55 °C (t1/255 °C ≈ 24 h) and 60 °C (t1/260 °C ≈ 4 h), respectively. Moreover, the biochemical characterization revealed that LdNDTS104C showed >60% relative activity across a broad range of temperature (30−90 °C) and pH (5−7). Finally, to study the potential application of LdNDTS104C as an industrial catalyst, the enzymatic synthesis of nelarabine was successfully carried out under different substrate conditions (1:1 and 3:1) at different reaction times. Under these experimental conditions, the production of nelarabine was increased up to 2.8-fold (72% conversion) compared with wild-type LdNDT.

Synthesis and Anticancer and Antiviral Activities of C-2'-Branched Arabinonucleosides.

d-Arabinofuranosyl-pyrimidine and -purine nucleoside analogues containing alkylthio-, acetylthio- or 1-thiosugar substituents at the C2' position were prepared from the corresponding 3',5'-O-silylene acetal-protected nucleoside 2'-exomethylenes by photoinitiated, radical-mediated hydrothiolation reactions. Although the stereochemical outcome of the hydrothiolation depended on the structure of both the thiol and the furanoside aglycone, in general, high d-arabino selectivity was obtained. The cytotoxic effect of the arabinonucleosides was studied on tumorous SCC (mouse squamous cell) and immortalized control HaCaT (human keratinocyte) cell lines by MTT assay. Three pyrimidine nucleosides containing C2'-butylsulfanylmethyl or -acetylthiomethyl groups showed promising cytotoxicity at low micromolar concentrations with good selectivity towards tumor cells. SAR analysis using a methyl ß-d-arabinofuranoside reference compound showed that the silyl-protecting group, the nucleobase and the corresponding C2' substituent are crucial for the cell growth inhibitory activity. The effects of the three most active nucleoside analogues on parameters indicative of cytotoxicity, such as cell size, division time and cell generation time, were investigated by near-infrared live cell imaging, which showed that the 2'-acetylthiomethyluridine derivative induced the most significant functional and morphological changes. Some nucleoside analogues also exerted anti-SARS-CoV-2 and/or anti-HCoV-229E activity with low micromolar EC50 values; however, the antiviral activity was always accompanied by significant cytotoxicity.

Nelarabine, etoposide, and cyclophosphamide in relapsed pediatric T-acute lymphoblastic leukemia and T-lymphoblastic lymphoma (study T2008-002 NECTAR).

Children with relapse of T-cell acute lymphoblastic leukemia (T-ALL) or lymphoblastic lymphoma (T-LBL) have a dismal prognosis, largely due to difficulty attaining second remission. We hypothesized that adding etoposide and cyclophosphamide to the nucleoside analog nelarabine could improve response rates over single-agent nelarabine for relapsed T-ALL and T-LBL. This phase I dose-escalation trial's primary objective was to evaluate the dose and safety of nelarabine given in combination with etoposide at 100 mg/m2 /day and cyclophosphamide at 330-400 mg/m2 /day, each for 5 consecutive days in children with either T-ALL (13 patients) or T-LBL (10 patients). Twenty-three patients were treated at three dose levels; 21 were evaluable for dose-limiting toxicities (DLT) and response. The recommended phase II doses (RP2D) for this regimen, when given daily ×5 every 3 weeks, were nelarabine 650 mg/m2 /day, etoposide 100 mg/m2 /day, and cyclophosphamide 400 mg/m2 /day. DLTs included peripheral motor and sensory neuropathies. An expansion cohort to evaluate responses at the RP2D was terminated early due to slow accrual. The overall best response rate was 38% (8/21), with 33% (4/12) responses in the T-ALL cohort and 44% (4/9) responses in the T-LBL cohort. These response rates are comparable to those seen with single-agent nelarabine in this setting. These data suggest that the addition of cyclophosphamide and etoposide to nelarabine does not increase the incidence of neurologic toxicities or the response rate beyond that obtained with single-agent nelarabine in children with first relapse of T-ALL and T-LBL.

Efficacy and safety of nelarabine in patients with relapsed or refractory T-cell acute lymphoblastic leukemia: a systematic review and meta-analysis.

Nelarabine is approved for the treatment of relapsed/refractory (R/R) T-cell acute lymphoblastic leukemia (T-ALL) patients who relapse following at least two different chemotherapy regimens. Previous studies have evaluated the efficacy and safety of nelarabine with chemotherapy in the treatment of R/R T-ALL. However, the results are inconsistent. This review aimed to summarize findings on efficacy and safety data in R/R T-ALL patients administered with the drug nelarabine. The present review conducted a comprehensive search of MEDLINE (via PubMed), WHO Clinical Trial Registry, Clinical Trials.gov, and Cochrane Central Register of Controlled Trials until 15 January 2022. Thirteen studies fulfilled the eligibility criteria with a total of 2508 patients. The efficacy of nelarabine was studied in terms of complete remission (CR) and partial remission (PR). Included studies reported overall random-effects pooled prevalence of CR and PR were 37.2 (95% CI: 22.8, 51.5) and 10.2 (95% CI: 4.9, 15.5), respectively. Most common adverse events associated with nelarabine were neutropenia, thrombocytopenia, fatigue, infections, and reversible peripheral neuropathy. Nelarabine is being used as salvage therapy as a bridge to hematopoietic stem cell transplantation and the findings of this meta-analysis indicate that it is an effective and safe treatment to be used in addition to the first-line treatment for R/R T-ALL.

Use of Arabinonucleosides for Development and Implementation of a Novel 2'-O-Protecting Group for Efficient Solid-Phase Synthesis and 2'-O-Deprotection of RNA Sequences.

The implementation of protecting groups for 2'-hydroxyl function of ribonucleosides is very demanding in that synthetic RNA sequences must be highly pure to ensure the safety and efficacy of nucleic acid-based drugs for treatment of human diseases. A synthetic approach consisting of a condensation reaction between 2'-O-aminoribonucleosides with ethyl pyruvate has been employed to provide stable 2'-O-imino-2-methyl propanoic acid ethyl esters. Conversion of these esters to fully protected ribonucleoside phosphoramidite monomers has allowed rapid and efficient incorporation of 2'-O-protected ribonucleosides into RNA sequences while minimizing the formation of process-related impurities during solid-phase synthesis. Two chimeric 20-mer RNA sequences have been synthesized and then exposed to a solution of sodium hydroxide to saponify the 2'-O-imino-2-methyl propanoic acid ethyl ester protecting groups to their sodium salts. When subjected to ion-exchange conditions at 65°C and near neutral pH, fully deprotected RNA sequences are isolated without production of alkylating side-products and/or formation of mutagenic nucleobase adducts. © 2022 Wiley Periodicals LLC. This article has been contributed to by US Government employees and their work is in the public domain in the USA. Basic Protocol 1: Synthesis of uridine 2'-O-imino-2-propanoic acid ethyl ester and its fully protected 3'-O-phosphoramidite Basic Protocol 2: Synthesis of N6 -protected adenosine 2'-O-imino-2-propanoic acid ethyl ester and its fully protected 3'-O-phosphoramidite Basic Protocol 3: Synthesis of N4 -protected cytidine 2'-O-imino-2-propanoic acid ethyl ester and its fully protected 3'-O-phosphoramidite Basic Protocol 4: Synthesis of N2 -protected guanosine 2'-O-imino-2-propanoic acid ethyl ester and its fully protected 3'-O-phosphoramidite Basic Protocol 5: Automated solid-phase RNA synthesis and deprotection using 2'-O-imino-2-proponate-protected phosphoramidites.