Therapeutic drug monitoring of antimetabolic cytotoxic drugs

MoS2 quantum dots as fluorescent probe for methotrexate detection

Herein, we developed a unique fluorescence biosensor for methotrexate assay based on MoS₂ quantum dots, which were synthesized in one step using sodium molybdate and cysteine as raw materials. The fluorescence of MoS₂ QDs could be quenched when encountered with methotrexate, which was attributed to the inner filter effect (IFE). Furthermore, this present IFE-based method showed the linearity between the MoS₂ QDs fluorescence intensity and the methotrexate concentration in the range of 0.05-1 μM with the LOD of 42 nM. The practical applicability of this strategy was successfully demonstrated by detecting methotrexate in real samples. Results indicated that the proposed method could be a promising sensing platform for methotrexate analysis.

Raman Spectroscopy and Its Modifications Applied to Biological and Medical Research

Nowadays, there is an interest in biomedical and nanobiotechnological studies, such as studies on carotenoids as antioxidants and studies on molecular markers for cardiovascular, endocrine, and oncological diseases. Moreover, interest in industrial production of microalgal biomass for biofuels and bioproducts has stimulated studies on microalgal physiology and mechanisms of synthesis and accumulation of valuable biomolecules in algal cells. Biomolecules such as neutral lipids and carotenoids are being actively explored by the biotechnology community. Raman spectroscopy (RS) has become an important tool for researchers to understand biological processes at the cellular level in medicine and biotechnology. This review provides a brief analysis of existing studies on the application of RS for investigation of biological, medical, analytical, photosynthetic, and algal research, particularly to understand how the technique can be used for lipids, carotenoids, and cellular research. First, the review article shows the main applications of the modified Raman spectroscopy in medicine and biotechnology. Research works in the field of medicine and biotechnology are analysed in terms of showing the common connections of some studies as caretenoids and lipids. Second, this article summarises some of the recent advances in Raman microspectroscopy applications in areas related to microalgal detection. Strategies based on Raman spectroscopy provide potential for biochemical-composition analysis and imaging of living microalgal cells, in situ and in vivo. Finally, current approaches used in the papers presented show the advantages, perspectives, and other essential specifics of the method applied to plants and other species/objects.

Advancing Raman spectroscopy from research to clinic: Translational potential and challenges

Raman spectroscopy has emerged as a non-invasive and versatile diagnostic technique due to its ability to provide molecule-specific information with ultrahigh sensitivity at near-physiological conditions. Despite exhibiting substantial potential, its translation from optical bench to clinical settings has been impacted by associated limitations. This perspective discusses recent clinical and biomedical applications of Raman spectroscopy and technological advancements that provide valuable insights and encouragement for resolving some of the most challenging hurdles.

Determination of O6-Methylguanine in dried blood spot of breast cancer patients after cyclophosphamide administration

Cyclophosphamide is a nitrogen mustard class of drugs that are often used in cancer chemotherapy. However, the use of Cyclophosphamide in high doses over a long period has been shown to increase the risk of developing secondary cancer. This can be indicated by the formation of mutagenic DNA adducts, such as O⁶-Methylguanine. Therefore, this adduct can be used as a biomarker for secondary cancer in patients receiving Cyclophosphamide. Bio sampling was carried out by using the Dried Blood Spot (DBS) method, followed by DNA extraction by using QIAamp DNA mini kit, and acid hydrolysis to obtain O⁶-Methylguanine. Analysis of O⁶-Methylguanine was performed by using the UPLC-MS/MS instrument with the conditions developed by Vianney, Harahap, & Suryadi (2021). Partial validation was carried out before the analysis. The results obtained from the calibration curve, accuracy, and precision validation test met the FDA requirements. The analysis method was then implemented in 16 breast cancer patients who received the Cyclophosphamide regimen. The O⁶-Methylguanine was successfully detected and quantified in all of the samples in the range of 0.55–6.66 ng/mL. It shows that the O⁶-Methylguanine accumulation in cancer patients receiving Cyclophosphamide is very likely to occur and the analysis method proposed by Vianney, Harahap, & Suryadi (2021) is potential to be used for Therapeutic Drug Monitoring in this group of patients.

Clinical Considerations Regarding the Use of Thiopurines in Older Patients with Inflammatory Bowel Disease

The number of older patients with inflammatory bowel disease (IBD) is increasing due to both improvements in the life expectancy of patients with long-lasting IBD and later onset of the disease. In spite of a less aggressive IBD phenotype, disease management in older patients is hampered by comorbidities and polypharmacy (which increase the risk of drug-related adverse events and errors in medication intake) and also by an increased risk of the infections and malignancies associated with the immunosuppressive drugs that are frequently used to treat IBD. Thiopurines are the most frequently used immunosuppressive drugs in IBD, though they are often discontinued due to adverse events. However, when tolerated, thiopurines are efficient in the maintenance of remission in ulcerative colitis and Crohn's disease. In fact, thiopurines still have a role to play in the treatment algorithm of older patients with IBD because anti-tumor necrosis factor agents do not provide clear advantages for this population in terms of their safety profile, while data on the new biological drugs are still scarce. In this article, we review the optimal use of thiopurines in older patients with IBD.

Nucleobase and Nucleoside Analogues: Resistance and Re-Sensitisation at the Level of Pharmacokinetics, Pharmacodynamics and Metabolism

Antimetabolites, in particular nucleobase and nucleoside analogues, are cytotoxic drugs that, starting from the small field of paediatric oncology, in combination with other chemotherapeutics, have revolutionised clinical oncology and transformed cancer into a curable disease. However, even though combination chemotherapy, together with radiation, surgery and immunotherapy, can nowadays cure almost all types of cancer, we still fail to achieve this for a substantial proportion of patients. The understanding of differences in metabolism, pharmacokinetics, pharmacodynamics, and tumour biology between patients that can be cured and patients that cannot, builds the scientific basis for rational therapy improvements. Here, we summarise current knowledge of how tumour-specific and patient-specific factors can dictate resistance to nucleobase/nucleoside analogues, and which strategies of re-sensitisation exist. We revisit well-established hurdles to treatment efficacy, like the blood-brain barrier and reduced deoxycytidine kinase activity, but will also discuss the role of novel resistance factors, such as SAMHD1. A comprehensive appreciation of the complex mechanisms that underpin the failure of chemotherapy will hopefully inform future strategies of personalised medicine.

Recommendations of the Spanish Working Group on Crohn's Disease and Ulcerative Colitis (GETECCU) on the use of thiopurines in inflammatory bowel disease

Thiopurines (azathioprine and mercaptopurine) are widely used in patients with inflammatory bowel disease. In this paper, we review the main indications for their use, as well as practical aspects on efficacy, safety and method of administration. They are mainly used to maintain remission in steroid-dependent disease or with ciclosporin to control a severe ulcerative colitis flare-up, as well as to prevent postoperative Crohn's disease recurrence, and also in combination therapy with biologics. About 30-40% of patients will not respond to treatment and 10-20% will not tolerate it due to adverse effects. Before they are prescribed, immunisation status against certain infections should be checked. Determination of thiopurine methyltransferase activity (TPMT) is not mandatory but it increases initial safety. The appropriate dose is 2.5mg/kg/day for azathioprine and 1.5mg/kg/day for mercaptopurine. Some adverse effects are idiosyncratic (digestive intolerance, pancreatitis, fever, arthromyalgia, rash and some forms of hepatotoxicity). Others are dose-dependent (myelotoxicity and other types of hepatotoxicity), and their surveillance should never be interrupted during treatment. If therapy fails or adverse effects develop, management can include switching from one thiopurine to the other, reducing the dose, combining low doses of azathioprine with allopurinol and assessing metabolites, before their use is ruled out. Non-melanoma skin cancer, lymphomas and urinary tract tumours have been linked to thiopurine therapy. Thiopurine use is safe during conception, pregnancy and breastfeeding.

Adherence to guidelines on prophylaxis of chemotherapy-induced nausea and vomiting in the National Cancer Institute, Sudan

<strong>Objective</strong>: To evaluate the adherence to American Society of Clinical Oncology (ASCO) guidelines for antiemetic prophylaxis of chemotherapy-induced nausea and vomiting and assess the outcomes of the prescribed antiemetic drugs.<br /> <strong>Methods</strong>: This prospective, observational study enrolled chemotherapy-naive cancer patients who were admitted to the National Cancer Institute between May and July 2015 for intravenous chemotherapy. Patient’s demographic data, chemotherapy protocols and types of antiemetic drugs were collected by reviewing patients’ files, chemotherapy prescription forms and interviewing the patients.<br /> <strong>Results</strong>: The data revealed that 90% of pre-chemotherapy antiemetic prescriptions did not adhere to antiemetic guidelines. The trends of non-adherence included an overuse of ondansetron (14%), under-prescribing of dexamethasone (16%) and corticosteroid duplication (14%). Regarding antiemetic use for the prevention of delayed emesis, the data showed that 90% of antiemetic prescriptions were non-adherent with ASCO guidelines, with overuse of ondansetron (20%) and metoclopramide (37%) and lack of dexamethasone prescriptions (80%) on days 2 and 3 being the most frequently reported trends. The percentage of patients with complete response (no emesis or rescue therapy) over 5 days post chemotherapy was 36%.<br /> <strong>Conclusion</strong>: The study indicated an extremely low adherence rate to ASCO guidelines for antiemetic prophylaxis of chemotherapy-induced nausea and vomiting. Non-adherence included a trend of both underuse and overuse of indicated antiemetic medications.

Xanthine Oxidoreductase in Drug Metabolism: Beyond a Role as a Detoxifying Enzyme

The enzyme xanthine oxidoreductase (XOR) catalyzes the last two steps of purine catabolism in the highest uricotelic primates. XOR is an enzyme with dehydrogenase activity that, in mammals, may be converted into oxidase activity under a variety of pathophysiologic conditions. XOR activity is highly regulated at the transcriptional and post-translational levels and may generate reactive oxygen and nitrogen species, which trigger different consequences, ranging from cytotoxicity to inflammation. The low specificity for substrates allows XOR to metabolize a number of endogenous metabolites and a variety of exogenous compounds, including drugs.

The present review focuses on the role of XOR as a drug-metabolizing enzyme, specifically for drugs with anticancer, antimicrobial, antiviral, immunosuppressive or vasodilator activities, as well as drugs acting on metabolism or inducing XOR expression.

XOR has an activating role that is essential to the pharmacological action of quinone drugs, cyadox, antiviral nucleoside analogues, allopurinol, nitrate and nitrite. XOR activity has a degradation function toward thiopurine nucleotides, pyrazinoic acid, methylxanthines and tolbutamide, whose half-life may be prolonged by the use of XOR inhibitors.

In conclusion, to avoid potential drug interaction risks, such as a toxic excess of drug bioavailability or a loss of drug efficacy, caution is suggested in the use of XOR inhibitors, as in the case of hyperuricemic patients affected by gout or tumor lysis syndrome, when it is necessary to simultaneously administer therapeutic substances that are activated or degraded by the drug-metabolizing activity of XOR.

Head to head evaluation of the analytical performance of two commercial methotrexate immunoassays and comparison with liquid chromatography-mass spectrometry and the former fluorescence polarization immunoassay

BACKGROUND

Monitoring of plasma drug levels is mandatory in patients receiving high-dose methotrexate. This study evaluated the analytical performance of the novel Architect and the established ARK™ methotrexate immunoassay (running on the Roche Cobas© c502 analyzer) in comparison with liquid chromatography-mass spectrometry (LC-MS) and the TDx/TDxFLx Methotrexate II assay.

METHODS

Imprecision and linearity were verified for the Architect and ARK assay according to CLSI EP15-A3 and EP6-A guidelines, respectively. The reported limit of quantitation (0.04 μmol/L) was tested for both assays according to the CLSI EP17-A2 guideline. Correlation and agreement between the different assays were evaluated using residual plasma samples (n=153).

RESULTS

Total imprecision was <6.3% and <9.5% for the Architect and ARK assay, respectively. The claimed linearity and limit of quantitation were confirmed for the Architect assay. For the ARK assay, imprecision at the limit of quantitation was <18% with a positive bias resulting in a high total error up to 58%, and hence the linearity could not be confirmed. Both assays showed strong correlations with the TDX assay and LC-MS but a positive bias of 12.2% and 20.5% in comparison to LC-MS for the Architect and ARK assay, respectively. For the ARK assay this bias increased dramatically for samples with concentrations towards the limit of quantitation.

CONCLUSIONS

The Architect assay is suitable for monitoring plasma methotrexate, but the ARK assay showed unsatisfactory performance in the analysis of low concentrated samples. Unlike the TDX assay, both assays require manual dilution of samples at higher concentrations, which delays sample processing in clinical routine.

Biosensors and nanobiosensors for therapeutic drug and response monitoring

Review of different biosensors and nanobiosensors increasingly used in therapeutic drug monitoring (TDM) for pharmaceutical drugs with dosage limitations or toxicity issues and for therapeutic response monitoring.

Development of an Assay for Methotrexate and Its Metabolites 7-Hydroxy Methotrexate and DAMPA in Serum by LC-MS/MS

Methotrexate (MTX) is a folic acid antagonist that is widely used as an immunosuppressant and chemotherapeutic agent. After high-dose administration of MTX serum levels must be monitored to determine when to administer leucovorin, a folic acid analog that bypasses the enzyme inhibition caused by MTX and reverses its toxicity. We describe a rapid and simple turbulent flow liquid chromatography (TFLC) method implementing positive heated electrospray ionization (HESI) for the accurate and precise determination of MTX, 7-hydroxymethotrexate (7-OH MTX), and 4-amino-4-deoxy-N(10)-methylpteroic acid (DAMPA) concentrations in serum. MTX is isolated from serum samples (100 μL) after protein precipitation with a methanolic solution containing internal standard (MTX-D3) followed by centrifugation. The supernatant is injected into the turbulent flow liquid chromatography which is followed by electrospray positive ionization tandem mass spectrometry (TFLC-ESI-MS/MS) and quantified using a six-point calibration curve. For MTX, 7-OH MTX, and DAMPA the assays were linear from 20 to 1000 nmol/L. Dilutions of 10-, 100-, and 1000-fold were validated giving a clinically reportable range of 20 to 1.0 × 10(6) nmol/L. Within-day and between-day precisions at concentrations spanning the analytical measurement ranges were less than 10 % for all three analytes.

Development and validation of a turbulent flow chromatography and tandem mass spectrometry method for the quantitation of methotrexate and its metabolites 7-hydroxy methotrexate and DAMPA in serum

A rapid and simple turbulent flow liquid chromatography (TFC-LC) method implementing positive heated electrospray ionization (HESI) for the accurate and precise determination of methotrexate (MTX), 7-hydroxy methotrexate (7-OH MTX), and 4-amino-4-deoxy-N(10)-methylpteroic acid (DAMPA) concentrations in serum was developed. MTX was isolated from serum samples (100μL) after protein precipitation with methanol containing formic acid and internal standard (MTX-D3) followed by centrifugation. The supernatant was injected into the turbulent flow liquid chromatography which is followed by electrospray positive ionization tandem mass spectrometry (TFC-LC-MS/MS) and quantified using a six-point calibration curve. For MTX and DAMPA the assays were linear from 10 to 1000nmol/L and for 7-OH MTX from 20 to 2000nmol/L. Dilutions of 10, 100 and 1000-fold were validated giving a clinically reportable range of 10nmol/L to 5×10(5)nmol/L. Within-day and between-day precisions at concentrations spanning the analytical measurement ranges were less than 10% for all three analytes. MTX, DAMPA and 7-OH MTX were sufficiently stable under all relevant analytical conditions. No significant matrix effect was observed during the method validation. The TFC-LC-MS/MS MTX method was also compared with three other clinically validated MTX assays: a dihydrofolate reductase (DHFR) inhibition assay, an immunoassay based on fluorescence polarization and a previously developed LC-MS/MS assay.

Physiologically based pharmacokinetic model for 6-mercpatopurine: exploring the role of genetic polymorphism in TPMT enzyme activity

AIMS

To extend the physiologically based pharmacokinetic (PBPK) model developed for 6-mercaptopurine to account for intracellular metabolism and to explore the role of genetic polymorphism in the TPMT enzyme on the pharmacokinetics of 6-mercaptopurine.

METHODS

The developed PBPK model was extended for 6-mercaptopurine to account for intracellular metabolism and genetic polymorphism in TPMT activity. System and drug specific parameters were obtained from the literature or estimated using plasma or intracellular red blood cell concentrations of 6-mercaptopurine and its metabolites. Age-dependent changes in parameters were implemented for scaling, and variability was also introduced for simulation. The model was validated using published data.

RESULTS

The model was extended successfully. Parameter estimation and model predictions were satisfactory. Prediction of intracellular red blood cell concentrations of 6-thioguanine nucleotide for different TPMT phenotypes (in a clinical study that compared conventional and individualized dosing) showed results that were consistent with observed values and reported incidence of haematopoietic toxicity. Following conventional dosing, the predicted mean concentrations for homozygous and heterozygous variants, respectively, were about 10 times and two times the levels for wild-type. However, following individualized dosing, the mean concentration was around the same level for the three phenotypes despite different doses.

CONCLUSIONS

The developed PBPK model has been extended for 6-mercaptopurine and can be used to predict plasma 6-mercaptopurine and tissue concentration of 6-mercaptopurine, 6-thioguanine nucleotide and 6-methylmercaptopurine ribonucleotide in adults and children. Predictions of reported data from clinical studies showed satisfactory results. The model may help to improve 6-mercaptopurine dosing, achieve better clinical outcome and reduce toxicity.

Comparison of pharmacokinetics and toxicity after high-dose methotrexate treatments in children with acute lymphoblastic leukemia

We carried out a detailed comparative study of the pharmacokinetics and toxicity of methotrexate (MTX) and 7-hydroxy-methotrexate (7-OH-MTX) after high-dose intravenous methotrexate (HD-MTX) in children with acute lymphoblastic leukemia (ALL). Overall, 65 children were treated with 5 g/m2/24 h MTX and 88 children were treated with 2 g/m2/24 h MTX according to ALL-BFM 95 and ALL IC-BFM 2002 protocols (mean age: 6.4 years, range 1.0-17.9 years). A total of 583 HD-MTX courses were analyzed. Serum MTX and 7-OH-MTX levels were measured at 24, 36, and 48 h, and cerebrospinal fluid (CSF) MTX levels were determined 24 h after the initiation of the infusion. The area under the concentration-time curve was calculated. Hepatotoxicity, nephrotoxicity, and bone marrow toxicity were estimated by routine laboratory tests. We investigated pharmacokinetics and toxicity in distinct age groups (< 6 and > 14 years). 5 g/m2/24 h treatments resulted in higher serum and CSF MTX and 7-OH-MTX levels (P < 0.05). The CSF penetration rate of MTX was independent of the MTX dose [2.3% (95% confidence interval: 1.7-2.5%) vs. 2.8% (95% confidence interval: 2.4-3%)]. The CSF MTX concentration was correlated with the 24 h MTX serum level (r = 0.38, P < 0.0001). Repeated treatments did not alter MTX or 7-OH-MTX levels. 7-OH-MTX levels were correlated with nephrotoxicity (r = 0.36, P < 0.0001). Higher MTX levels and toxicity occurred more frequently in children aged older than 14 years (P < 0.05). Therapeutic serum and CSF MTX concentrations can be achieved more reliably with 5 g/m2/24 h treatments. To predict the development of toxicity, monitoring of the level of the 7-OH-MTX is useful. Monitoring of pharmacokinetics is essential to prevent the development of severe adverse events in adolescents.

Determination of urinary 6-mercaptopurine and three of its metabolites by HPLC–UV coupled with the iodine–azide reaction

Background: The presented method is able to determine 6-mercaptopurine (6-MP), 6-thioguanine, 6-mercaptopurine riboside and 6-thioguanine riboside in urine, and is thereby dedicated to control of thiopurine therapy of children with acute lymphoblastic leukemia. Good separation of the mentioned compounds was achieved on a C18 stationary phase with a sodium azide and sodium heptane sulfonate solution, acetonitrile and water at ratio of 50:1:49 (v/v/v). Results: Coefficient of regression is >0.99 for all linearity ranges. LOD and LOQ are 0.3, 0.4, 0.3, 0.8 and 0.4, 0.6, 0.5 and 0.9 nmol/ml of urine for 6-MP, 6-thioguanine, 6-mercaptopurine riboside and 6-thioguanine riboside, respectively. Intra- and inter-day recovery and RSD are close to 100% and less than 10%, respectively, for all investigated thiopurines. Conclusion: The elaborated method was successfully applied for detection and quantitation of 6-MP and its selected metabolites in patients’ urine samples.

Promise and challenges in drug discovery and development of hybrid anticancer drugs

BACKGROUND

Because cancer is a complex disease, it is unlikely that a single mono functional 'targeted' drug will be effective for treating this most advanced disease. Combined drugs that impact multiple targets simultaneously are better at controlling complex disease systems, are less prone to drug resistance and are the standard of care in cancer treatment. In order to improve the efficiency of using a two-drug cocktail, one approach involves the use of the so-called hybrid drugs, which comprises the incorporation of two drugs in a single molecule with the intention of exerting dual drug action.

OBJECTIVE

In the present article, we discuss the design, synthesis and various applications of anticancer hybrid agents and the developments in this field during the last few decades. Additionally, we describe different types of linkers and their role in contributing towards biological effects and the in vivo mechanism of drug release. We also depict some challenges from scientific and regulatory perspectives in the hybrid drug development process.

CONCLUSION

In the era of increasing drug resistance in cancer patients, the discovery of hybrid drugs could provide an effective strategy to create chemical entities likely to be more efficacious and less prone to resistance. However, some technical and regulatory challenges will have to be surmounted before hybrid drugs succeed in the clinical settings and justify the considerable promise of this novel concept.

Chemotherapy agents: a primer for the interventional radiologist

In this article, the authors review the basic principles of cancer chemotherapy and provide an overview of each of the general classes of chemotherapeutic agents with a target audience of interventional radiologists in mind. Special attention is paid to agents used in regional chemotherapy as well as agents commonly included in systemic chemotherapeutic regimens for patients who also require regional chemotherapy.

Distribution of three antituberculous drugs and their metabolites in different parts of pathological vertebrae with spinal tuberculosis

STUDY DESIGN

To detect drug concentration levels and metabolite using high-performance liquid chromatography.

OBJECTIVE

To map concentration levels of three antituberculous drugs and two metabolites in the abnormal osseous tissues around the foci of patients with spinal tuberculosis.

SUMMARY OF BACKGROUND DATA

Concentration levels of antituberculous drugs in the focus of spinal tuberculosis has been reported. However, the mapping of drugs distribution in different regions surrounding the foci of tuberculosis vertebrae remains unexplored, as well as the metabolite of the drugs.

METHODS

Thirty-eight patients with spinal tuberculosis were assigned into sclerotic group (n = 13) and nonsclerotic group (n = 25) based on computed tomographic (CT) images. All patients received a chemotherapy 10 months with 2HRZE/8H(2)R(2)E(2). All patients received surgery after 4 weeks of chemotherapy. Samples of serum, ilium, and pathologic vertebral tissues, including the foci, sclerotic wall (if applicable), region I of abnormal osseous tissues (within 4 mm), and region II of abnormal osseous tissues (more than 4 mm) from the foci were collected during operation. Concentration levels and metabolite of three drugs were measured using high-performance liquid method for all samples. Differences of means within groups were evaluated by ANOVA and Dunnett post hoc. A significant levels was set at P < 0.05.

RESULTS

Concentration levels of drugs varied greatly in different regions of spinal tuberculosis vertebrae. Concentration levels of isoniazid and rifampin were higher than the effective bactericidal concentration (EBC) level and that of pyrazinamide was five times of the minimal inhibitory concentration in the region II of abnormal osseous tissues and the ilium of nonsclerotic group. Three drugs achieved EBC in the region I of abnormal osseous tissues in the nonsclerotic group but not in the sclerotic group. Except pyrazinamide no drugs and their metabolite were identified in the foci of the sclerotic group, whereas there is trace of drugs and their metabolite in the foci of the nonsclerotic group.

CONCLUSION

Three drugs resulted in an effective bactericidal concentration level in osseous tissues around the foci of spinal tuberculosis except the osseous tissues 4 mm surrounding the sclerotic wall. The results suggested that osseous tissues within 4 mm surrounding the sclerotic wall should be excised during the surgery.

Use of antineoplastic agents in patients with cancer who have HIV/AIDS

Highly active antiretroviral therapy (HAART) has substantially reduced morbidity and mortality of AIDS-related complications in patients with HIV; however, the prevalence of AIDS-defining cancers and non-AIDS-defining cancers has increased. In this Review we discuss the management of HAART pharmacotherapy in relation to cytotoxic chemotherapy or targeted antineoplastic agents. We will review potential pharmacological interactions between antiretroviral and antineoplastic therapies and consider how to combine antiretroviral and antineoplastic agents in patients with HIV who are receiving HAART therapy.

Pharmacogenomic studies of the anticancer and immunosuppressive thiopurines mercaptopurine and azathioprine

AIMS

To examine the allelic variation of three enzymes involved in 6-mercaptopurine/azathioprine (6-MP/AZA) metabolism and evaluate the influence of these polymorphisms on toxicity, haematological parameters and metabolite levels in patients with acute lymphoblastic leukaemia (ALL) or inflammatory bowel disease (IBD).

METHODS

Clinical data and blood samples were collected from 19 ALL paediatric patients and 35 IBD patients who were receiving 6-MP/AZA therapy. All patients were screened for seven genetic polymorphisms in three enzymes involved in mercaptopurine metabolism [xanthine oxidase, inosine triphosphatase (C94-->A and IVS2+21A-->C) and thiopurine methyltransferase]. Erythrocyte and plasma metabolite concentrations were also determined. The associations between the various genotypes and myelotoxicity, haematological parameters and metabolite concentrations were determined.

RESULTS

Thiopurine methyltransferase variant alleles were associated with a preferential metabolism away from 6-methylmercaptopurine nucleotides (P = 0.008 in ALL patients, P = 0.038 in IBD patients) favouring 6-thioguanine nucleotides (6-TGNs) (P = 0.021 in ALL patients). Interestingly, carriers of inosine triphosphatase IVS2+21A-->C variants among ALL and IBD patients had significantly higher concentrations of the active cytotoxic metabolites, 6-TGNs (P = 0.008 in ALL patients, P = 0.047 in IBD patients). The study confirmed the association of thiopurine methyltransferase heterozygosity with leucopenia and neutropenia in ALL patients and reported a significant association between inosine triphosphatase IVS2+21A-->C variants with thrombocytopenia (P = 0.012). CONCLUSIONS; Pharmacogenetic polymorphisms in the 6-MP pathway may help identify patients at risk for associated toxicities and may serve as a guide for dose individualization.

Thiopurines in current medical practice: molecular mechanisms and contributions to therapy-related cancer

Thiopurines have diverse clinical applications and their long-term use as anti-rejection drugs in transplant patients has been associated with a significantly increased risk of various types of cancer. Although they are slowly being replaced by a new generation of non-thiopurine immunosuppressants, it is anticipated that their use in the management of inflammatory and autoimmune diseases will continue to increase. Therapy-related cancer will remain a potential consequence of prolonged treatment for these generally non-life-threatening conditions. Understanding how thiopurines contribute to the development of cancer will facilitate clinical decisions about the potential risks to patients of long-term treatment for chronic inflammatory disorders.

The clinical role of genetic polymorphisms in drug-metabolizing enzymes

For most drug-metabolizing enzymes (DMEs), the functional consequences of genetic polymorphisms have been examined. Variants leading to reduced or increased enzymatic activity as compared to the wild-type alleles have been identified. This review tries to define potential fields in the therapy of major medical conditions where genotyping (or phenotyping) of genetically polymorphic DMEs might be beneficial for drug safety or therapeutic outcome. The possible application of genotyping is discussed for depression, cardiovascular diseases and thromboembolic disorders, gastric ulcer, malignant diseases and tuberculosis. Some drugs used for relief of these ailments are metabolized with participation of genetically polymorphic DMEs including CYP2D6, CYP2C9, CYP2C19, thiopurine-S-methyltransferase, dihydropyrimidine dehydrogenase, uridine diphosphate glucuronosyltransferase and N-acetyltransferase type 2. Current evidence suggests that taking genetically determined metabolic capacities of DMEs into account has the potential to improve individual risk/benefit relationship. However, more prospective studies with clinical endpoints are needed before the paradigm of 'personalized medicine' based on DME variants can be established.

Thiopurine methyltransferase activity in Spain: a study of 14,545 patients

We sought to assess the activity of thiopurine methyltransferase (TPMT) in 14,545 Spanish patients with different diseases amenable to treatment with azathioprine/6-mercaptopurine (6-MP), and to evaluate the proportion of patients with low TPMT activity and therefore a higher risk of myelotoxicity with these drugs. TPMT activity in red blood cells (RBCs) was measured by a radiochemical method. The association between several clinical variables and TPMT activity was assessed by multiple linear regression. We included 14,545 patients: autoimmune hepatitis (n=359 patients), inflammatory bowel disease (n=7,046), multiple sclerosis (n = 814), myasthenia gravis (n=344), pemphigus (n=133), and other diseases (n=5,849). Mean TPMT activity was 20.1 +/- 6 U/mL, but differed depending on the disease (P<.001). TPMT distribution was low (<5) in 0.5%; intermediate (5.0-13.7) in 11.9%; or high (>or=13.8) in 87.6%. Only when TPMT activity was considered separately in each disease did it reveal a normal distribution. In the multivariate analysis, gender, hematocrit, and treatment with 5-aminosalicylates/steroids/azathioprine/6-MP statistically influenced TPMT activity, although, probably, in a clinically irrelevant manner. This study shows, in a large sample of 14,545 patients, that 0.5% had low TPMT activity, indicating a higher risk of myelotoxicity with azathioprine/6-MP, a figure similar or slightly higher than that reported in other areas. Nevertheless, the trimodal distribution of TPMT activity varied depending on disease, and the proportion of patients with low activity values ranged from 0-0.8%. The drugs prescribed for the treatment of autoimmune diseases, including azathioprine/6-MP, modified TPMT activity, but the magnitude of this effect was very small and the differences found are probably irrelevant from the clinical point of view.

Chemotherapy Dosing Part II: Alternative Approaches and Future Prospects

This overview follows on from part I, which described the current practices used in chemotherapy dosing and the paucity of scientific evidence to support them. In part II, alternative approaches are discussed, both in terms of scientific rationale and practical application. These include therapeutic drug monitoring, the use of pharmacokinetic-pharmacodynamic relationships, flat-fixed dosing, Bayesian modelling and dose banding.

[Monitoring of thiopurine methyltransferase and thiopurine metabolites to optimize azathioprine therapy in inflammatory bowel disease]

Determination of the activity of thiopurine methyltransferase (TPMT) and of thiopurine metabolites (6-thioguanine and 6-methylmercaptopurine nucleotides) could be useful for individualized monitoring of azathioprine (AZA) and 6-mercaptopurine (6-MP) doses. TPMT activity in the general population follows a trimodal distribution, in which approximately 0.3% of the population is homozygotic for the low-activity allele. A notable correlation has been observed between the low TPMP activity genotype or phenotype and the risk of myelotoxicity. Patients with a high TPMT activity genotype or homozygous phenotype should receive immunosuppressive doses that have clearly been demonstrated to be effective. In contrast, in patients with a low TPMT activity genotype or homozygous phenotype, the use of AZA/6-MP should be contraindicated or only very small doses should be administered. Importantly, TPMP deficiency explains only some cases of myelotoxicity and consequently periodic laboratory testing should be performed in patients receiving AZA/6-MP, even though TPMP function may be normal. Currently, the utility of routine thiopurine metabolite determinations in patients undergoing AZA/6-MP therapy has not been established and this practice should be limited to specific situations such as lack of response to thiopurine therapy or the occurrence of thiopurine-related adverse effects. Randomized trials comparing the routine strategy of AZA/6-MP dosing (based exclusively on the patient's weight) versus individualized monitoring (based on quantification of TPMP activity and/or thiopurine metabolites) are required before definitive conclusions on the most effective alternative can be drawn.

Metabolism and transport of oxazaphosphorines and the clinical implications

The oxazaphosphorines including cyclophosphamide (CPA), ifosfamide (IFO), and trofosfamide represent an important group of therapeutic agents due to their substantial antitumor and immuno-modulating activity. CPA is widely used as an anticancer drug, an immunosuppressant, and for the mobilization of hematopoetic progenitor cells from the bone marrow into peripheral blood prior to bone marrow transplantation for aplastic anemia, leukemia, and other malignancies. New oxazaphosphorines derivatives have been developed in an attempt to improve selectivity and response with reduced toxicity. These derivatives include mafosfamide (NSC 345842), glufosfamide (D19575, beta-D-glucosylisophosphoramide mustard), NSC 612567 (aldophosphamide perhydrothiazine), and NSC 613060 (aldophosphamide thiazolidine). This review highlights the metabolism and transport of these oxazaphosphorines (mainly CPA and IFO, as these two oxazaphosphorine drugs are the most widely used alkylating agents) and the clinical implications. Both CPA and IFO are prodrugs that require activation by hepatic cytochrome P450 (CYP)-catalyzed 4-hydroxylation, yielding cytotoxic nitrogen mustards capable of reacting with DNA molecules to form crosslinks and lead to cell apoptosis and/or necrosis. Such prodrug activation can be enhanced within tumor cells by the CYP-based gene directed-enzyme prodrug therapy (GDEPT) approach. However, those newly synthesized oxazaphosphorine derivatives such as glufosfamide, NSC 612567 and NSC 613060, do not need hepatic activation. They are activated through other enzymatic and/or non-enzymatic pathways. For example, both NSC 612567 and NSC 613060 can be activated by plain phosphodiesterase (PDEs) in plasma and other tissues or by the high-affinity nuclear 3'-5' exonucleases associated with DNA polymerases, such as DNA polymerases and epsilon. The alternative CYP-catalyzed inactivation pathway by N-dechloroethylation generates the neurotoxic and nephrotoxic byproduct chloroacetaldehyde (CAA). Various aldehyde dehydrogenases (ALDHs) and glutathione S-transferases (GSTs) are involved in the detoxification of oxazaphosphorine metabolites. The metabolism of oxazaphosphorines is auto-inducible, with the activation of the orphan nuclear receptor pregnane X receptor (PXR) being the major mechanism. Oxazaphosphorine metabolism is affected by a number of factors associated with the drugs (e.g., dosage, route of administration, chirality, and drug combination) and patients (e.g., age, gender, renal and hepatic function). Several drug transporters, such as breast cancer resistance protein (BCRP), multidrug resistance associated proteins (MRP1, MRP2, and MRP4) are involved in the active uptake and efflux of parental oxazaphosphorines, their cytotoxic mustards and conjugates in hepatocytes and tumor cells. Oxazaphosphorine metabolism and transport have a major impact on pharmacokinetic variability, pharmacokinetic-pharmacodynamic relationship, toxicity, resistance, and drug interactions since the drug-metabolizing enzymes and drug transporters involved are key determinants of the pharmacokinetics and pharmacodynamics of oxazaphosphorines. A better understanding of the factors that affect the metabolism and transport of oxazaphosphorines is important for their optional use in cancer chemotherapy.

Therapeutic Drug Monitoring and Pharmacogenetic Tests as Tools in Pharmacovigilance

Therapeutic drug monitoring (TDM) and pharmacogenetic tests play a major role in minimising adverse drug reactions and enhancing optimal therapeutic response. The response to medication varies greatly between individuals, according to genetic constitution, age, sex, co-morbidities, environmental factors including diet and lifestyle (e.g. smoking and alcohol intake), and drug-related factors such as pharmacokinetic or pharmacodynamic drug-drug interactions. Most adverse drug reactions are type A reactions, i.e. plasma-level dependent, and represent one of the major causes of hospitalisation, in some cases leading to death. However, they may be avoidable to some extent if pharmacokinetic and pharmacogenetic factors are taken into consideration. This article provides a review of the literature and describes how to apply and interpret TDM and certain pharmacogenetic tests and is illustrated by case reports. An algorithm on the use of TDM and pharmacogenetic tests to help characterise adverse drug reactions is also presented. Although, in the scientific community, differences in drug response are increasingly recognised, there is an urgent need to translate this knowledge into clinical recommendations. Databases on drug-drug interactions and the impact of pharmacogenetic polymorphisms and adverse drug reaction information systems will be helpful to guide clinicians in individualised treatment choices.

Actividad de la tiopurina metiltransferasa en la enfermedad inflamatoria intestinal. Un estudio en 7.046 pacientes españoles

BACKGROUND AND OBJECTIVE

Our objective was to assess the activity of thiopurine methyltransferase (TPMT) in a very large number of Spanish patients with inflammatory bowel disease (IBD), to evaluate the influence of several variables (including azathioprine or 6-mercaptopurine) on that activity, and to know the proportion of patients with low TPMT activity and therefore high risk of myelotoxicity when treated with these drugs.

PATIENTS AND METHOD

TPMT activity in red blood cells (RBCs) was measured by a radiochemical method. The association between several variables and TPMT values was assessed by multiple lineal regression.

RESULTS

7046 patients were included (mean age: 37 years; 53% males): 70% with Crohn's disease, 22% with ulcerative colitis, and 8% with indeterminate colitis. Mean TPMT value was 20 (6) U/ml RBCs (minimum 0 and maximum 46). TPMT activity distribution was as follows: low levels (< 5 U/ml), 0.5%; intermediate (5-13.7), 11.1%; and high (> or = 13.8), 88.4%. TPMT values did not follow a normal distribution (p < 0.001). In the univariate study, statistically significant differences (p < 0.001), yet of doubtly clinical significance because its minimal magnitude, were demonstrated in TPMT values depending on age, sex, type of disease, and treatment with azathioprine/6-mercaptopurine. In the multivariate study, the variables associated with TPMT activity were: sex, treatment with 5-aminosalicylates, steroids and azathioprine/6-mercaptopurine.

CONCLUSIONS

This study shows that 0.5% of the Spanish patients with IBD have low TPMT activity (< 5 U/ml RBCs), a figure similar to that reported in other countries, these patients being at higher risk of myelotoxicity when treated with azathioprine or 6-mercaptopurine. The drugs usually prescribed for the treatment of IBD, including 5-aminosalicylates and azathioprine/6-mercaptopurine, do not seem to modify in a clinically relevant manner TPMT activity.

A Simple and Sensitive Fully Validated HPLC-UV Method for the Determination of 5-Fluorouracil and Its Metabolite 5,6-Dihydrofluorouracil in Plasma

The authors developed a simple and sensitive, fully validated HPLC-UV method for the determination of both 5-FU and its metabolite DHFU in small-volume plasma samples. The analytes were separated on a 4.6 x 250 mm ID Atlantis dC18 5-microm column with isocratic elution at room temperature. Chlorouracil was used as internal standard. The analytes were detected with an UV diode array detector. DHFU was detected at 205 nm, 5-FU at 266 nm, and chlorouracil at both wavelengths. The limits of quantification in plasma were 0.040 mug /mL for 5-FU and 0.075 microg/mL for DHFU. Linearity, accuracy, precision, recovery, dilution, freeze-thaw stability, and stability in the sample compartment were evaluated. The method appeared linear over a range from 0.04 to 15.90 microg/mL for 5-FU and from 0.075 to 3.84 microg/mL for DHFU. The method appeared very suitable for therapeutic drug monitoring and pharmacokinetic studies of 5-FU because of its simple extraction and small sample volume. Problems in earlier published methods with interfering peaks and variable retention times were overcome. The method appeared also to be suitable for detection of uracil and its metabolite dihydrouracil in plasma.

The impact of thiopurine S-methyltransferase polymorphisms on azathioprine dose 1 year after renal transplantation

Azathioprine metabolism is influenced by activity of the enzyme thiopurine S-methyltransferase (TPMT), which varies markedly between individuals. In this study we examined the influence of TPMT gene polymorphisms on azathioprine dose 1 year after renal transplantation. TPMT coding and promoter genotypes were determined using PCR-based assays. Azathioprine dose, white cell count, and intercurrent events throughout the first year after renal transplantation were ascertained from contemporaneous clinical notes. All patients analysed ( n=172) received an initial azathioprine dose of 1.5 mg/kg per day. Twelve individuals with one variant TPMT coding allele were detected (*3A n=11, *3C n=1). Of these, 58% required azathioprine dose reduction because of leucopenia, compared to only 30% of homozygous wild-type patients ( P=0.04). A significant correlation between the presence of >/=11 variable number tandem repeats (VNTRs) in the TPMT promoter and reduction in azathioprine dose was also identified ( P=0.001). We concluded that when azathioprine is administered at an initial dose of 1.5 mg/kg per day, both coding and promoter TPMT polymorphisms influence the dose tolerated.

[Thiopurine methyltransferase activity and myelosuppression in inflammatory bowel disease patients treated with azathioprine and 6-mercaptopurine]

BACKGROUND AND OBJECTIVE

We aimed at assessing whether there exists a relationship between thiopurine methyltransferase (TPMT) activity and the incidence of adverse events, especially myelotoxicity, in patients with inflammatory bowel disease treated with azathioprine (AZA) or 6-mercaptopurine (6-MP).

PATIENTS AND METHOD

By means of a radiochemical method, we determined the TPMT activity in erythrocytes of patients with inflammatory bowel disease who had received previously or at the time of the study AZA or 6-MP (n = 97). A group of 37 patients who had never been treated with these drugs was included. We studied the relationship between several variables and TPMT values as well as their correlation with adverse events.

RESULTS

Mean (SD) TPMT value was 20.8 (5) U/ml erythrocytes (from 7.8 to 32.7). There was no patient with low TPMT levels (< 5); 9% patients had intermediate levels (from 5 to 13.7 U/ml), while 91% displayed high levels (>= 13.8 U/ml). There were no differences when comparing TPMT values according to several variables such as age, gender, tobacco consumption, weight, type of inflammatory bowel disease, and treatment with 5-aminosalicylates, steroids or AZA/6-MP. Side effects were seen in 13 out of 97 (13%) patients administered AZA/6-MP. None patient with side effects exhibited low TPMT levels (< 5 U/ml), nor even intermediate levels (5-13.7 U/ml). There were no differences when comparing mean TPMT values in patients with side effects and in those without side effects.

CONCLUSIONS

In this study, the usefulness of the determination of the TPMT activity to identify patients with inflammatory bowel disease at risk of myelotoxicity due to AZA or 6-MP has not been confirmed. Therefore, even when the TPMT enzymatic activity is normal, it is necessary to continue performing the periodic laboratory analysis.

Utility of measuring 6-methylmercaptopurine and 6-thioguanine nucleotide levels in managing inflammatory bowel disease patients treated with 6-mercaptopurine in a clinical practice setting

BACKGROUND

Measuring levels of 6-mercaptopurine (6-MP) metabolites (6-thioguanine nucleotides [6-TGNs] and 6-methylmercaptopurine [6-MMP]) has been proposed as a method to adjust 6-MP dose to optimize therapeutic response while minimizing toxicity in patients with inflammatory bowel disease. A 6-TGN level of >230 pmol/8 x 108 red blood cells (RBCs) has been reported to be associated with a higher efficacy rate, and a level of >450 pmol/8 x 108 RBCs has been reported to be associated with myelotoxicity. A 6-MMP level of >5,700 pmol/8 x 108 RBCs has been reported to be associated with an increased frequency of abnormal results of liver function tests (LFTs).

GOALS

To report our experience with 6-MMP and 6-TGN levels in a clinical practice setting.

STUDY

Using outpatient clinic medical records, we identified 53 measurements. Indications for measurement, 6-MP dose, and subsequent adjustments were documented.

RESULTS

Indications for measurements included the following: persistent symptoms, 31 cases (58.5%); abnormal LFT results, 7 (13.2%); steroid dependency, 6 (11.3%); anemia, 4 (7.5%); and leukopenia, 2 (3.8%). Of the 31 cases with persistent symptoms, 12 had "therapeutic" 6-TGN levels and other interventions were undertaken. 6-TGN levels were "subtherapeutic" in 19. The 6-MP dose was increased, and remission was achieved in 10 cases after a mean period of 3.6 weeks. Among the cases with abnormal LFT results, 6-MMP levels were high in five and low in two. Among the steroid dependency cases, 6-TGN levels were "subtherapeutic" in five. The dose was increased and steroids were weaned in three cases. The 6-TGN level was high in one of the leukopenia cases and the 6-MP dose was decreased. 6-TGN levels were not above the "target range" in any of the anemia cases.

CONCLUSION

Measuring levels of 6-MP metabolites may have a role in customizing 6-MP dosing. This role is not completely clear and needs to be explored in larger well-controlled studies.

Population pharmacokinetics of cisplatin after 120-h infusion: application to routine adaptive control with feedback

OBJECTIVE

A Bayesian population pharmacokinetics study of data from routine therapeutic drug monitoring cisplatin during a 5-day infusion of cisplatin.

METHODS

A total of 95 kinetics data sets (58 patients) were available to perform this study. Individual pharmacokinetic parameters, estimated from 20 courses of treatment in 18 patients, were used to calculate the population parameters (cl: 0.175 +/- 0.034 L/h; t(1/2): 327 +/- 91 h). The accuracy of Bayesian forecasting was tested by comparing in 40 other patients the clearance values calculated either from a complete kinetics profile (eight sampling times) or from three early samples and the new population parameters. Finally, drug monitoring efficacy was assessed by comparing the target Cmax values with the Cmax obtained after dose adjustment based upon early Bayesian estimation of the individual pharmacokinetic parameters.

RESULTS

: No significant difference was found between Bayesian and experimental clearances. Besides, dose-individualization proved to successfully adjust Cmax values around their respective target.

CONCLUSION

The new reference pharmacokinetic population parameters lead to accurate estimation of individual pharmacokinetic parameters from a limited number of samples, thus allowing efficient therapeutic drug monitoring during 5-day infusion regimens of cisplatin.

Actividad de la tiopurina metiltransferasa en pacientes con hepatitis autoinmune

BACKGROUND AND OBJECTIVE

The measurement of the activity of thiopurine methyltransferase (TPMT) is useful to monitor, on an individual basis, the dose of azathioprine in order to identify patients at risk of myelotoxicity. However, the distribution of the enzymatic activity in patients with autoimmune hepatitis is unknown. Our objective was to analyze the activity of TPMT in a group of 200 patients with autoimmune hepatitis and to evaluate the possible effect of some variables such as the treatment with azathioprine on this activity.

PATIENTS AND METHOD

The activity of TPMT was determined by a radiochemical method; the activity was determined in the erythrocytes of patients with autoimmune hepatitis from 31 Spanish hospitals. We studied the relationship between TPMT levels and several demographic variables as well as its correlation with azathioprine treatment.

RESULTS

We included 209 patients (80% females, mean age 50 years, 39% on azathioprine). The mean value of TPMT was 20.7 U/ml erythrocytes (from 0 to 39). TPMT levels were adjusted to a normal distribution. 1%, 9% and 90% patients had low (< 5 U/ml), intermediate (5-13.7 U/ml) and high (>= 13.8 U/ml) TPMT levels, respectively. In the multivariate analysis, there were no differences when comparing the mean TPMT values according to age, gender or previous azathioprine treatment.

CONCLUSIONS

TPMT activity in patients with autoimmune hepatitis displays a similar distribution to that reported in other populations (approximately 1% of patients have low levels and 9% have intermediate levels) and it does not depend on the age, gender or simultaneous azathioprine treatment.

Bayesian population model of methotrexate to guide dosage adjustments for folate rescue in patients with breast cancer

BACKGROUND

Methotrexate (MTX) infusions may induce severe side-effects, and alkaline hydration along with folinic acid rescue is a common way to reduce such toxic risks. The purpose of this study was to develop an adaptive rescue strategy based upon the early detection of patients with impaired MTX elimination.

METHODS AND RESULTS

In this study, we propose a simple population-based Bayesian approach for predicting MTX plasma concentration from a limited number of samples, so as to adapt both duration and dosage of the rescue agent to be used next. Ten kinetic profiles obtained after 10 courses of MTX (1.5 g/m2) in seven patients with inflammatory breast cancer were used to establish the population pharmacokinetic parameters (Cl, 8.16 L/h; t1/2, 12.7 h). This population was next involved in the Bayesian estimation of MTX individual pharmacokinetic parameters from only two blood samples (T24 and T36 h), thus allowing one to forecast the elimination of this drug by predicting MTX levels at 48 h. According to the MTX concentrations predicted during the elimination phase, folinic acid rescue was then prolonged in patients likely to be overexposed.

CONCLUSION

The Bayesian estimation presented in this study was an easy and convenient method to efficiently detect patients with impaired MTX elimination in routine clinical practice. This information enabled the introduction of strategies for minimizing the risk of severe drug toxicity.

Pharmacogenetic tactics and strategies: implications for paediatrics

Genetic diversity exerts profound effects on variation in human drug response in adults, but comparatively little research that specifically relates to genetically abnormal responses in infancy and childhood has been reported. Specific genetic changes in human enzymes, receptors and other proteins that are implicated in drug response and their associated phenotypic correlates provide needed data for construction of profiles individualised to predict susceptibility to adverse drug reactions. If therapy adheres to such guidelines, failure to respond to drug therapy and drug toxicity among genetically susceptible persons can be greatly minimised or averted.