Pharmacokinetic study of cystemustine, administered on a weekly schedule in cancer patients.

BACKGROUND: Cystemustine is a chloroethylnitrosourea mostly active in humans against glioma and melanoma. The present report describes the results of a new phase I trial with cystemustine administered on a weekly schedule. The pharmacokinetic and pharmacodynamic properties of cystemustine were investigated. PATIENTS AND METHODS: Forty-three patients entered this study. Cystemustine was administered at dose levels ranging from 30 to 60 mg/m2. The drug was given on days 1, 8, 15 and 22, followed by a 4-week rest period. RESULTS: Thrombocytopenia was the dose-limiting toxicity and appeared to be reversible, but probably cumulative. This toxicity appeared dose-related, both in frequency and severity. The maximum tolerated dose was 60 mg/m2. Nonhematological toxicity was generally mild. Three partial responses were observed at dose levels of 50 and 60 mg/m2. Pharmacokinetics analysis showed mono- or biphasic cystemustine blood disposition with a mean a half-life of 4 min and mean terminal half-life of 49 min. CONCLUSIONS: There was a clear linear relationship between the area under the blood drug concentration-time curve (AUC) and the dose of cystemustine (P < 0.001). There was also a significant relationship between the AUC and the toxic effects of cystemustine on platelets, granulocytes and leukocytes (P < 0.001). A reasonable starting dose for phase II studies is 40 mg/m2, with dose escalation based on blood cell counts.     

Predicting hematological toxicity (myelosuppression) of cytotoxic drug therapy from in vitro tests

Several clinical oncology units are studying the roles of in vitro hematotoxicology in phase I evaluations. At the same time, the European Center for the Validation of Alternative Methods (ECVAM) is supporting a validation study of the CFU-GM assay [13]. It is important that these activities be coordinated so that high-performance, optimized technical protocols are used for prospective and retrospective clinical evaluations. The EORTC, the NCI, and ECVAM could provide support for these coordinated efforts. There is an opportunity for medical oncologists involved in early clinical trials to participate in the evaluation of in vitro tests and their clinical application. Fundamental to acceptance of these assays by oncologists and regulatory scientists, they must predict clinical outcome for myelosuppressive agents and then improve phase I design and performance. These achievements would justify more aggressive dose escalation schemes using guidance from in vitro studies without compromising patient safety. Success in predicting neutropenia might also stimulate the research required to understand how to predict other hematologic toxicities, such as thrombocytopenia.The complexity of a validation study in hematotoxicology is that it seeks to predict the level of exposure that causes neutropenia, in contrast to other validation studies that have sought to classify a xenobiotic as toxic or not. It may be that the clinical relevance of a new assay is not just a yes–no answer. This important distinction came from the realization that the xenobiotic tolerance in other organ systems of the body must be the same or greater than marrow in order for myelosuppression to be a clinical consequence of exposure. Pharmacological principles of systemic exposure and toxicity that are integrated into the prediction model provide the links to clinical oncology.It is also important to anticipate future applications of in vitro hematotoxicology. If the maximum tolerated level of drug exposure for human hematopoietic cells can be predicted, then in vitro hematotoxicology could play an important role in new drug discovery. One concept involves screening for compounds that show efficacy at the IC level that predicts maximum tolerated exposure levels in the human [12, 22]. 'Therapeutic index-based' drug discovery has been applied to the tallimustine family with some success [21].     

Flow and Particle Deposition Patterns in a Realistic Human Double Bifurcation Airway Model

Velocity profiles, local deposition efficiencies (DE), and deposition patterns of aerosol particles in the first three generations (i.e., double bifurcations) of an airway model have been simulated numerically, in which the airway model was constructed from computed tomography (CT) scan data of real human tracheobronchial airways. Three steady inhalation conditions, 15, 30, and 60 L/min, were simulated and a range of micrometer particle sizes (1–20 μm diameter) were injected into the model. Results were then compared with experimental and other numerical results which had employed either similar model geometry or test conditions. The effects of inhalation conditions on velocity profiles and particle deposition were studied. The data indicated that the local deposition efficiencies in the first bifurcation increased with a rise in the Stokes number (St) within St range from 0.0004 to 0.7. Within the same St range, DE in the second bifurcations (both left and right) was dropped dramatically after St increased to 0.17. Also, the second bifurcation in the right side (B2.1, closer to first bifurcation than left side, B2.2) was found to show a much higher (almost double) DE than the left side. This may be due to the fact that the left main bronchus is longer and has greater angulation than the right main bronchus. Generally, the present simulation using a computational fluid dynamic (CFD) technique obtained concurrent results with subtle differences compared to other works. However, due to omission of larynx in the model, which is known to significantly modify airflow and hence particle deposition, the present model may only serve as the “stepping stone” to simulating and analyzing dose-response or inhalation risk assessment visually for clinical researchers.     

Toxicity of the antimalarial artemisinin and its dervatives

As long as no effective malaria vaccine is available, chemotherapy belongs to the most important weapons fighting malaria. One of the most promising new drug developments is the sesquiterpene artemisinin (ARS) and its derivatives, e.g., artemether, arteether, and sodium artesunate. Large clinical studies and meta-analyses did not show serious side effects, although proper monitoring of adverse effects in developing countries might not be a trivial task. There is a paucity of large-scale clinical trials suitable to detect rare but significant toxicity. Therefore, a final and definitive statement on the safety of artemisinins still cannot be made. In contrast, animal experiments show considerable toxicity upon application of artemisinins. In the present review, the authors give a comprehensive overview on toxicity studies in cell culture and in animals (mice, rats, rabbits, dogs, monkeys) as well as on toxicity reported in human clinical trials. The authors emphasize the current knowledge on neurotoxicity, embryotoxicity, genotoxicity, hemato- and immunotoxicity, cardiotoxicity, nephrotoxicity, and allergic reactions. The lesson learned from animal and human studies is that long-term availability rather than short-term peak concentrations of artemisinins cause toxicity. Rapid elimination of artemisinins after oral intake represents a relatively safe route of administration compared to delayed drug release after intramuscular (i.m.) injection. This explains why considerable toxicities were found in the majority of animal experiments, but not in human studies. In addition, there are drug-related differences, i.e., intramuscular application of artemether or arteether, but not to artesunate, which is safe and gives good profiles after i.m. administration in severe malaria. Although there is no need to increase doses of artemisinins for uncomplicated malaria, this has to be taken into account for cerebellar involvement in severe malaria. It might also be important in determining dose limitations for treatment of other diseases such as cancer.     

Hematotoxicity and genotoxicity evaluations in Swiss mice intraperitoneally exposed to Bacillus thuringiensis (var kurstaki) spore crystals genetically modified to express individually Cry1Aa,Cry1Ab,Cry1Ac,or Cry2Aa

Bacillus thuringiensis (Bt) has been widely used in foliar sprays as part of integrated pest management strategies against insect pests of agricultural crops. Since the advent of genetically modified plants expressing Bt δ‐endotoxins, the bioavailability of Cry proteins has increased, and therefore for biosafety reasons their adverse effects should be studied, mainly for nontarget organisms. We evaluated, in Swiss mice, the hematotoxicity and genotoxicity of the genetically modified strains of Bt spore crystals Cry1Aa, 1Ab, 1Ac, or 2Aa at 27 mg/kg, and Cry1Aa, 1Ab and 2Aa also at 136 and 270 mg/kg, administered with a single intraperitoneal injection 24 h before euthanasia. Controls received filtered water or cyclophosphamide. Blood samples collected by cardiac puncture were used to perform hemogram, and bone marrow was extracted for the micronucleus test. Bt spore crystals presented toxicity for lymphocytes when in higher doses, which varied according to the type of spore crystal studied, besides promoting cytotoxic and genotoxic effects for the erythroid lineage of bone marrow, mainly at highest doses. Although the profile of such adverse side effects can be related to their high level of exposure, which is not commonly found in the environment, results indicated that these Bt spore crystals were not harmless to mice. This suggests that a more specific approach should be taken to increase knowledge about their toxicological properties and to establish the toxicological risks to nontarget organisms. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 970–978, 2016.     

Hematotoxocity among Chinese workers heavily exposed to benzene

Benzene is a well-established hematotoxin. However, reports of its effects on specific blood cells have been somewhat inconsistent and the relative toxicity of benzene metabolites on peripheral blood cells in humans has not been evaluated. We compared hematologic outcomes in a cross-sectional study of 44 workers heavily exposed to benzene (median: 31 parts permillion [ppm] as an 8-hr time-weighted average [TWA] and 44 age and gender-matched unexposed controls from Shanghai, China. All hematologic parameters (total white blood cells [WBC], absolute lymphocyte count, platelets, red blood cells, and hematocrit) were decreased among exposed workers compared to controls, with the exception of the red blood cell mean corpuscular volume (MCV), which has higher among exposed subjects. In a subgroup of workers who were not exposed to more than 31 ppm benzene on any of 5 sampling days (n = 11, median 8 hr TWA = 7.6 ppm, range = 1–20 ppm), only the absolute lymphocyte count was significantly different between exposed workers (mean [sd] 1.6 [0.4] x 10³ μL) and controls (1.9 [0.4] x 10³ μL, p = 0.03). Among exposed subjects, a dose-response relationship with various measures of current benzene exposure (i.e., personal air monitoring, benzene metabolites in urine) was present only for the total WBC count, the absolute lymphocyte count, and the MCV. Correlations between benzene metabolites and hematologic parameters were generally similar, although hydroquinone was somewhat more strongly associated with a decrease in the absolute lymphocyte count, and catechol was more strongly associated with an increase in MCV. Morphologic review of peripheral blood slides demonstrated an excess of red blood cell abnormalities (i.e., stomatocytes and target cells) only in the most heavily exposed workers, with no differences in granulocyte, lymphocyte, or platelet morphology noted. Although benzene can affect all the major peripheral blood elements, our results support the use of the absolute lymphocyte count as the most sensitive indicator of benzene-induced hematotoxicity. © 1995 Wiley-Liss, Inc.     

Acute hematologic toxicity and practicability of dose-intensified BEACOPP chemotherapy for advanced stage Hodgkin's disease

Background:Evidence is recently accumulating that the novelBEACOPP (bleomycin (B), etoposide (E), adriamycin (A), cyclophosphamide (C),vincristine (O), procarbazine (P), prednisone (P)) chemotherapy is a highlyeffective treatment for advanced stage Hodgkin's disease. Two dose variantsof BEACOPP are currently tested in a phase III randomized multicenter trialof the GHSG. To enable more extensive testing of BEACOPP we characterized itspracticability regarding schedule adherence, acute hematotoxicity and need forsupportive treatment. Patients and methods:Data of 858 patients (6592 therapy cycles)from 184 participating institutions were evaluated. Planned total drug dosesof the baseline variant (arm 1) were 80, 2400, 200, 5200, 11.2, 5600 and 4480mg/m² for B, E, A, C, O, P and P, respectively. Compared to arm 1,the doses of E, A and C in the dose-intensified variant (arm 2) were escalatedby factor 2.0, 1.4, 1.92, respectively, using G-CSF assistance. Stepwise dosereductions were specified in case of dose-limiting toxicities. Both variantsare given in eight three-weekly courses. Results:Median dose adherence (dose actually given relative toplanned arm 1 dose) in arm 1 was 1.0 for all drugs. Relative dose escalationof E, A, and C actually maintained in arm 2 was 1.83, 1.37 and 1.77 (medians),respectively, and 70% of patients maintained elevated dose levelsthroughout the entire treatment. Dose-limiting toxicities occurred in25% of cycles in arm 2, most frequently due to leukocytopenia andthrombocytopenia. Time courses of leukocytes in arm 2 showed more severe butnot more prolonged leukocytopenia compared with arm 1. WHO grades 3–4infections were documented in 2.1% (arm 1) and 3.1% (arm 2) ofall cycles. Erythrocytes were transfused in 6% (arm 1) and 28%(arm 2), platelets in <1% (arm 1) and 6% (arm 2) of allcycles. Conclusions:Both BEACOPP schemes are practicable in a largemulticenter setting. Despite increased hematotoxicity, moderate doseescalation is safe for the majority of the patients with G-CSF assistance andstandard supportive treatment.     

Systemic and myelotoxic effects of single administration of 2,3,7,8-tetrabromodibenzo-p-dioxin in rats

Objective  Systemic and myelotoxic effects of 2,3,7,8-tetrabromodibenzo-p-dioxin (TBDD) were examined by the single administration of TBDD by gavage to rats. Methods  Fifteen Wistar rats of both sexes per group received 0, 10, 30, 100 or 300 μg TBDD/kg body weight. Rats surviving to the scheduled necropsy on Days 2, 7 and 36 after TBDD administration were examined for growth rate, organ weight, hematology, histopathology and adipose tissue levels of TBDD. Results  Three 300 μg/kg-dosed females died on Days 21, 23 and 27, and exhibited a marked decrease in body weight, severe thymic atrophy, decreased bone marrow hematopoiesis and hemorrhage in the subarachnoid space of brain and spinal cord. TBDD-dosed surviving rats exhibited growth retardation, decreased bone marrow hematopoiesis, decreases in red blood cell counts, hemoglobin concentrations, and hematocrit values, an increase in reticulocytes and decreases in platelet counts, white blood cell counts and eosinophils. These signs suggested TBDD myelotoxicity. Splenic extramedullary hematopoiesis was increased in both sexes given TBDD, whereas atrophy of the splenic white pulp occurred only in TBDD-dosed females. Marked decreases in body weights and the size and weight of the thymus, severe thymic atrophy and death in TBDD-dosed females suggested a wasting syndrome. The adipose tissue level of TBDD culminated on Day 7 and decreased to 20–30% of the Day 7 level on Day 36. Conclusions  The TBDD-induced effects were characterized by a wasting syndrome and myelotoxicity that appeared at the dose levels of 30 μg/kg and higher and caused death in 300 μg/kg-dosed females.     

Prognostic factors for hematotoxicity of chemotherapy in aggressive non-Hodgkin's lymphoma.

BACKGROUND: Little is known on the heterogeneity of hematotoxicity in patients receiving multicycle chemotherapy. PATIENTS AND METHODS: We analyzed data of 1399 patients with aggressive lymphoma from trials using CHOP (combination chemotherapy with cyclophosphamide, doxorubicin, vincristine and prednisone)-like therapies. Multivariate modeling was carried out for leukocytopenia, thrombocytopenia and anemia and the models were validated by two large independent datasets from trials with/without usage of the CD20-antibody rituximab. RESULTS: On the basis of these models, we are able to predict the remarkable heterogeneity of hematotoxicity and propose to use risk groups. Regarding leukocytopenia, the low toxicity risk group experienced World Health Organization grade 4 in <10% of the cycles while the high toxicity risk group in almost all cycles. For thrombocytopenia, groups were detectable with almost no grade 3 or 4 toxicity and others where two out of three cycles were affected. In a separate set of models, the first cycle toxicity was the strongest predictor for later hematotoxicity. The risk for leukocytopenia was associated with infections, antibiotic use, hospitalization and treatment-related mortality, indicating the clinical usefulness of the models. For the first time, a Web-based tool is made available to easily predict the hematotoxicity in clinical practice (www.toxcalculator.com). CONCLUSION: This analysis has implications for patient management and prophylaxis.