New isocratic high-performance liquid chromatographic procedure to assay the anti-sickling compound hydroxyurea in plasma with ultraviolet detection

Resveratrol plus low-dose hydroxyurea compared to high-dose hydroxyurea alone is more effective in γ-globin gene expression and ROS reduction in K562 cells

Hydroxyurea (HU) is an anti-cancer drug that is used for the treatment of hemoglobinopathies as a γ-globin inducer. However, its dose-dependent effects have hampered its clinical reliability. Resveratrol (RSV) is an antioxidant and γ-globin inducer. The present study aimed to assess their combined effects on the γ-globin gene expression and reactive oxygen species (ROS) level of K562 cells. The results indicated that the γ-globin gene expression was approximately two folds higher in the group treated with RSV 50 µM + HU 25 µM in comparison to HU 100 μM alone (***p < 0.001). However, there was an inverse relationship between the expression of γ-globin gene and HU concentration in the combined groups. Furthermore, the combinations of RSV and HU significantly reduced ROS levels compared to single drugs. Overall, the combination of these compounds was an appropriate strategy for increasing γ-globin expression, reducing oxidant levels, and alleviating the adverse effects of HU.

MicroNIR/Chemometrics Assessement of Occupational Exposure to Hydroxyurea

Portable Near Infrared spectroscopy (NIRs) coupled to chemometrics was investigated for the first time as a novel entirely on-site approach for occupational exposure monitoring in pharmaceutical field. Due to a significant increase in the number of patients receiving chemotherapy, the development of reliable, fast, and on-site analytical methods to assess the occupational exposure of workers in the manufacture of pharmaceutical products, has become more and more required. In this work, a fast, accurate, and sensitive detection of hydroxyurea, a cytotoxic antineoplastic agent commonly used in chemotherapy, was developed. Occupational exposure to antineoplastic agents was evaluated by collecting hydroxyurea on a membrane filter during routine drug manufacturing process. Spectra were acquired in the NIR region in reflectance mode by the means of a miniaturized NIR spectrometer coupled with chemometrics. This MicroNIR instrument is a very ultra-compact portable device with a particular geometry and optical resolution designed in such a manner that the reduction in size does not compromise the performances of the spectrometer. The developed method could detect up to 50 ng of hydroxyurea directly measured on the sampling filter membrane, irrespective of complexity and variability of the matrix; thus extending the applicability of miniaturized NIR instruments in pharmaceutical and biomedical analysis.

Hydroxyurea-Lactose Interaction Study: In Silico and In Vitro Evaluation

The Maillard reaction between hydroxyurea (a primary amine-containing drug) and lactose (used as an excipient) was explored. The adduct of these compounds was synthesized by heating hydroxyurea with lactose monohydrate at 60 °C in borate buffer (pH 9.2) for 12 h. Synthesis of the adduct was confirmed using UV-visible spectroscopy and Fourier transform infrared, differential scanning calorimetry, high-pressure liquid chromatography, and liquid chromatography-mass spectrometry studies. An in silico investigation of how the adduct formation affected the interactions of hydroxyurea with its biological target oxyhemoglobin, to which it binds to generate nitric oxide and regulates fetal hemoglobin synthesis, was carried out. The in silico evaluations were complemented by an in vitro assay of the anti-sickling activity. Co-incubation of hydroxyurea with deoxygenated blood samples reduced the percentage of sickled cells from 38% to 12 ± 1.6%, whereas the percentage of sickled cells in samples treated with the adduct was 17 ± 1.2%. This indicated loss of anti-sickling activity in the case of the adduct. This study confirmed that hydroxyurea can participate in a Maillard reaction if lactose is used as a diluent. Although an extended study at environmentally feasible temperatures was not carried out in the present investigation, the partial loss of the anti-sickling activity of hydroxyurea was investigated along with the in silico drug-target interactions. The results indicated that the use of lactose in hydroxyurea formulations needs urgent reconsideration and that lactose must be replaced by other diluents that do not form Maillard adducts.

Hydroxyurea: Analytical techniques and quantitative analysis

Hydroxyurea is a potent disease-modifying therapeutic agent with efficacy for the treatment of sickle cell anemia. When administered at once-daily oral doses that lead to mild marrow suppression, hydroxyurea leads to substantial and sustained fetal hemoglobin induction, which effectively inhibits erythrocyte sickling. When escalated to maximum tolerated dose, hydroxyurea has proven laboratory and clinical effects for both children and adults with sickle cell anemia. However, there is substantial inter-patient variability with regard to the optimal dosing regimen, as well as differences in treatment-related toxicities and responses that may be explained by hydroxyurea pharmacokinetics and pharmacogenetics. Addressing the safety and efficacy of hydroxyurea treatment requires quantitative and accurate drug analysis, and various laboratory techniques have been established. We review the historical and current analytical techniques for measuring hydroxyurea concentrations accurately, and discuss clinical settings where quantitative analysis can increase understanding and safety of this important therapeutic agent, and ultimately improve patient outcomes.

Stable-Isotope Dilution HPLC-Electrospray Ionization Tandem Mass Spectrometry Method for Quantifying Hydroxyurea in Dried Blood Samples

BACKGROUND

Sickle cell anemia (SCA) is a life-threatening blood disorder characterized by the presence of sickle-shaped erythrocytes. Hydroxyurea is currently the only US Food and Drug Administration-approved treatment and there is a need for a convenient method to monitor compliance and hydroxyurea concentrations, especially in pediatric SCA patients.

METHODS

We describe a novel approach to the determination of hydroxyurea concentrations in dried whole blood collected on DMPK-C cards or volumetric absorptive microsampling (VAMS) devices. Hydroxyurea was quantified by electrospray ionization LC-MS/MS using [¹³C¹⁵N₂]hydroxyurea as the internal standard. Calibrators were prepared in whole blood applied to DMPK-C cards or VAMS devices.

RESULTS

Calibration curves for blood hydroxyurea measured from DMPK-C cards and VAMS devices were linear over the range 0.5-60 μg/mL. Interassay and intraassay CVs were <15% for blood collected by both methods, and the limit of detection was 5 ng/mL. Whole blood hydroxyurea was stable for up to 60 days on DMPK-C cards and VAMS devices when frozen at -20 °C or -80 °C. Whole blood hydroxyurea concentrations in samples collected on DMPK-C cards or VAMS devices from SCA patients were in close agreement.

CONCLUSIONS

This tandem mass spectrometry method permits measurement of hydroxyurea concentrations in small volumes of dried blood applied to either DMPK-C cards or VAMS devices with comparable performance. This method for measuring hydroxyurea from dried blood permits the evaluation of therapeutic drug monitoring, individual pharmacokinetics, and medication adherence using heel/finger-prick samples from pediatric patients with SCA treated with hydroxyurea.

Isotope-dilution gas chromatography-mass spectrometry method for the analysis of hydroxyurea

BACKGROUND

Hydroxyurea is used in the treatment of various malignancies and sickle cell disease. There are limited studies on the pharmacokinetics of hydroxyurea, particularly in pediatric patients. An accurate, precise, and sensitive method is needed to support such studies and to monitor therapeutic adherence. We describe a novel gas chromatography-mass spectrometry (GC-MS) method for the determination of hydroxyurea concentration in plasma using stable labeled hydroxyurea C N2 as an internal standard.

METHODS

The method involved an organic extraction followed by the preparation of trimethylsilyl (TMS) derivatives of hydroxyurea for GC-MS selected ion-monitoring analysis. The following mass-to-charge (m/z) ratio ions for silated hydroxyurea and hydroxyurea C N2 were monitored: hydroxyurea-quantitative ion 277, qualifier ions 292 and 249; hydroxyurea C N2-quantitative ion 280, qualifier ion 295. This method was evaluated for reportable range, accuracy, within-run and between-run imprecisions, and limits of quantification.

RESULTS

The reportable range for the method was 0.1-100 mcg/mL. All results were accurate within an allowable error of 15%. Within-run and between-run imprecisions were <15%. Samples were stable for at least 4 hours at room temperature, 2 months at -20°C, and 6 months at -70°C, and after 3 freeze/thaw cycles. Extraction efficiency for 1-, 5-, 10-, and 50-mcg/mL samples averaged 2.2%, 1.8%, 1.6%, and 1.4%, respectively.

CONCLUSIONS

The isotope-dilution GC-MS method for analysis of hydroxyurea described here is accurate, sensitive, precise, and robust. Its characteristics make the method suitable for supporting pharmacokinetic studies and/or clinical therapeutic monitoring.

Plasma hydroxyurea determined by gas chromatography-mass spectrometry

Hydroxyurea treatment is efficiently used to ameliorate the clinical course of patients affected with sickle cell disease. To understand the patient's wide variation in the clinical response to that drug and monitor its plasma levels, a new method was developed and validated. Fifty microL plasmatic samples containing hydroxyurea are added with internal standard, deproteinized, evaporated to dryness, silanized, and analyzed by gas chromatography-mass spectrometry, which operates in the selected ion mode after electron impact fragmentation. Linearity was found to extend to at least 100mg/L. Over a 1-25mg/L concentration range, coefficients of variation for intra-day and inter-day precision are 5.3% and 7.7%, respectively. Plasma blank-samples reveal endogenous hydroxyurea at a level <or=0.2mg/L. The performances of the method, which is fast and simple, encounter the analytical goals needed for evaluation of hydroxyurea treatment and for pharmacokinetic studies.

Plasma and urine hydroxyurea levels might be useful in the management of adult sickle cell disease

Hydroxyurea (HU) is useful for treating sickle cell anemia because of its ability to reduce some of the severe clinical events such as painful crises and acute chest syndrome. It may also reduce the need for blood transfusions and frequent hospitalizations and reduce mortality. Nevertheless, no consistent recommendations regarding its therapeutic schedule are defined. Our aim was to improve and validate a high performance liquid chromatography (HPLC) technique to measure HU and to study HU levels in serum and urine of sickle cell anemia patients and relate this to treatment efficacy and compliance. Thirty-seven patients received 1,128 +/- 333 mg of HU per day (8.0 to 28.0 mg/kg/day). Plasma and/or urine were sampled and HU was measured using an HPLC method coupled with UV detection. We validated a specific, sensitive assay with good reproducibility and linearity, and showed a positive relationship between plasma HU concentrations and time elapsed between oral HU intake and sampling. We observed plasma HU concentrations were positively correlated with change in mean corpuscular volume (MCV) before and during the treatment. No correlation was obtained between HU concentration and Hb F level.

Quantitative analysis of trimethylsilyl derivative of hydroxyurea in plasma by gas chromatography–mass spectrometry

Hydroxyurea is an antitumor drug widely used in the treatment of sickle cell disease. The drug has been analyzed in biological fluids by a number of high-performance liquid chromatography (HPLC) methods. This paper describes a fast and highly reliable capillary gas chromatography-mass spectrometry (GC-MS) procedure that was developed for the detection and quantitation of hydroxyurea in plasma. The compound and its labeled internal standard were liquid extracted from plasma and derivatized with BSTFA before analysis. The detection limit of the assay was 0.078 microg/ml and the limit of quantitation was 0.313 microg/ml with linearity up to 500 microg/ml. Intra-day variation, as coefficient of variation (C.V., %) over the selected concentration range, was 0.3-8.7% and inter-day variation was 0.4-9.6%.

Combined use of nonmyelosuppressive nitrosourea analogues with hydroxyurea in the induction of F-cell production in a human erythroleukemic cell line

OBJECTIVE

Although hydroxyurea (HU) has been used clinically to treat patients with sickle cell disease (SCD), not all patients benefit from HU treatment due to its toxicity. The objective of this study was to investigate the effectiveness of the use of two new Hb F-inducing nitrosourea analogues, 2-[3-(2-methyl, 2-nitroso) ureido]-2-deoxy-D-glucopyranose (MNGU) and 2-[3-(2-chloroethyl) ureido]-2-deoxy-D-glucopyranose (CGU), in combination with HU in K562 cells or erythroid progenitors.

MATERIALS AND METHODS

After K562 cells were cultured with different concentrations of HU with CGU or MNGU, aliquots of the cells were obtained to determine the total (benzidine-positive) hemoglobin level, number of F cells, and Hb F level. Erythroid progenitor cells of SCD patients and healthy donors were cultured with the optimal drug concentrations, and the number of BFU-E and Hb F level were determined.

RESULTS

Our results showed that the combined use of HU with CGU or MNGU increased the number of both benzidine-positive normoblasts and F cells in a synergistic manner. Further, a lower concentration of HU was required to induce a significant level of Hb F synthesis when combined with either of the two compounds in comparison with treatment with HU alone. On day 4, the number of benzidine-positive cells was 4.5- to 6.5-fold and the number of F cells was 5.0- to 8.0-fold higher than the respective numbers in the untreated K562 cells. Similarly, a 3.2- to 14.3-fold induction of Hb F was obtained when human erythroid progenitors from SCD patients were treated with the same drug combinations.

CONCLUSION

Based on these results, the use of CGU or MNGU in combination with HU might offer substantial benefits to patients with SCD and other hemoglobinopathies.

Enhancement of hemoglobin and F-cell production by targeting growth inhibition and differentiation of K562 cells with ribonucleotide reductase inhibitors (didox and trimidox) in combination with streptozotocin

Upon appropriate drug treatment, the human erythroleukemic K562 cells have been shown to produce hemoglobin and F-cells. Fetal hemoglobin (Hb F) inhibits the polymerization events of sickle hemoglobin (Hb S), thereby ameliorating the clinical symptoms of sickle cell disease. Ribonucleotide reductase inhibitors (RRIs) have been shown to inhibit the growth of myeloid leukemia cells leading to the production of Hb F upon differentiation. Of the RRIs currently in use, hydroxyurea is the most effective agent for Hb F induction. We have examined the capacity of two novel RRIs, didox (DI) and trimidox (TRI), in combination with streptozotocin (STZ), to induce hemoglobin and F-cell production. The K562 cells were cultured with different concentrations of didox-STZ or trimidox-STZ at a fixed molar ratio of 3:1 and 1:5 for 96 hr, respectively. At pre-determined time intervals, aliquots of cells were obtained and total hemoglobin (benzidine positive) levels, number of F-cells, and Hb F were determined by the differential staining technique, fetal hemoglobin assay kit, and fluorescence cytometry respectively. The effect of combined drug treatment on the growth of K562 cells was examined by isobologram analysis. Our results indicate that a synergistic growth-inhibitory differentiation effect occurred when didox or trimidox was used in combination with STZ on K562 cells. There was an increase in the number of both benzidine-positive normoblasts and F-cells, accompanied by morphologic appearances typical of erythroid maturation. On day 4, the number of benzidine-positive cells showed a 6-9-fold increase and the number of F-cells was between 2.5- and 5.7-fold higher than the respective controls. Based upon these results, treatment with a ribonucleotide reductase inhibitor, such as didox or trimidox, in combination with STZ, might offer an additional promising option in sickle cell disease therapy.