Clinical pharmacology and pharmacogenetics of thiopurines

Xanthine oxidase activity in thiopurine curative Chinese inflammatory bowel disease patients

Xanthine oxidase (XO) competes with thiopurine S‐methyltransferase (TPMT) and hypoxanthine guanine phosphoribosyltransferase (HPRT) to metabolize azathioprine (AZA)/6‐mercaptopurine (6‐MP) in vivo. A retrospective investigation was performed to detect the activity of XO in thiopurine curative Chinese inflammatory bowel disease (IBD) patients. We also evaluated whether a relationship between XO activity and incidence of thiopurine‐induced adverse effects (AEs) existed. Clinical data and blood samples were collected from 140 IBD patients before receiving AZA/6‐MP therapy, and the erythrocyte XO activity was measured. The XO activities of all patients were 20.29 ± 4.43 U/g Hb. No sex difference in XO activity was observed (p = .728), and the XO activity showed no difference between the UC and CD patients (p = .082). AEs were observed in 41 (29.3%) patients including leukopenia (26, 18.57%), gastrointestinal intolerance (11, 7.86%), flu‐like symptom (5, 3.57%), alopecia (5, 3.57%), and hepatotoxicity (1, 0.71%). XO activity was significantly lower in the patients with AEs than in those without AEs (18.40 ± 3.73 vs. 21.07 ± 4.48 U/g Hb, p = .001), especially in the patients with leukopenia (18.29 ± 3.68 vs. 21.07 ± 4.48 U/g Hb, p = .004). However, no significant difference in XO activity was found between patients with and without other AEs. Decreased XO activity was observed in the patients who developed flu‐like symptoms (17.58 ± 3.50 U/g Hb) and alopecia (18.67 ± 2.91 U/g Hb) compared to those who did not, although the differences did not reach statistical significance. These findings suggested that patients with low XO expression might have a high risk of thiopurine‐induced toxicity.

Identification of the key target profiles underlying the drugs of narrow therapeutic index for treating cancer and cardiovascular disease

An appropriate therapeutic index is crucial for drug discovery and development since narrow therapeutic index (NTI) drugs with slight dosage variation may induce severe adverse drug reactions or potential treatment failure. To date, the shared characteristics underlying the targets of NTI drugs have been explored by several studies, which have been applied to identify potential drug targets. However, the association between the drug therapeutic index and the related disease has not been dissected, which is important for revealing the NTI drug mechanism and optimizing drug design. Therefore, in this study, two classes of disease (cancers and cardiovascular disorders) with the largest number of NTI drugs were selected, and the target property of the corresponding NTI drugs was analyzed. By calculating the biological system profiles and human protein–protein interaction (PPI) network properties of drug targets and adopting an AI-based algorithm, differentiated features between two diseases were discovered to reveal the distinct underlying mechanisms of NTI drugs in different diseases. Consequently, ten shared features and four unique features were identified for both diseases to distinguish NTI from NNTI drug targets. These computational discoveries, as well as the newly found features, suggest that in the clinical study of avoiding narrow therapeutic index in those diseases, the ability of target to be a hub and the efficiency of target signaling in the human PPI network should be considered, and it could thus provide novel guidance in the drug discovery and clinical research process and help to estimate the drug safety of cancer and cardiovascular disease.

A screen printed electrode modified with Fe3O4@polypyrrole-Pt core-shell nanoparticles for electrochemical detection of 6-mercaptopurine and 6-thioguanine

In this paper, Fe₃O₄@ppy-Pt core-shell nanoparticles (NPs) could be produced and utilized for the development of a novel electrochemical sensor to detect 6-mercaptopurine (6-MP). 6-MP determination was examined by cyclic voltammetry (CV), chronoamperometry (CHA), linear sweep voltammetry (LSV), and differential pulse voltammetry (DPV) at Fe₃O₄@ppy-Pt core-shell NPs modified screen printed electrode (Fe₃O₄@ppy-Pt/SPE) in phosphate buffered solution (PBS). The outcomes obtained from DPV demonstrated that the Fe₃O₄@ppy-Pt/SPE proved a linear concentration range among 0.04 and 330.0 μM having a detection limit of 10.0 nM for 6-MP. Also, modified electrode was satisfactorily utilized to detect 6-MP in the presence of 6-thioguanine (6-TG). This sensor showed two separate oxidative peaks at 530 mV for 6-MP and at 730 mV for 6-TG with a peak potential separation of 200 mV which was large enough for simultaneous detection of the two anticancer drugs. In addition, the proposed sensor presented long-term stability, good repeatability, and excellent reproducibility. Finally, the modified electrode demonstrated satisfactory outcomes while used in real samples, proposing the appropriate potential of Fe₃O₄@ppy-Pt/SPE in the case of clinical diagnosis, biological samples and pharmaceutical compounds analysis.

A MnO2 nanosheet-assisted ratiometric fluorescence probe based on carbon quantum dots and o-phenylenediamine for determination of 6-mercaptopurine

A MnO₂ nanosheet-assisted ratiometric fluorescence probe based on carbon quantum dots (CQDs) and o-phenylenediamine (OPD) has been developed for the detection of the anticancer drug 6-mercaptopurine (6-MP). CQDs with strong fluorescence are synthesized via the one-step hydrothermal method. MnO₂ nanosheets as an oxidase-mimicking nanomaterial directly oxidize OPD into 2,3-diaminophenazine (DAP) which has a fluorescence emission at 570 nm, whereas the fluorescence of CQDs at 445 nm is then reduced by the DAP through the inner filter effect (IFE) under a single excitation wavelength (370 nm). After adding 6-MP, MnO₂ nanosheets can be reduced to Mn²⁺ and lose their oxidase-like property, blocking the IFE with the fluorescence decrease of DAP and fluorescence increase of CQDs. The novel ratiometric fluorescence probe exhibits considerable sensitivity toward 6-MP and linear response is in the 0.46-100.0 μmol L^-1 concentration range with the detection limit of 0.14 μmol L^-1. Furthermore, the probe shows good selectivity when exposed to a series of interfering other organic and inorganic compounds, and biomolecules and can be applied to the detection for 6-MP in human serum samples and pharmaceutical tablets. Satisfactory recoveries of 6-MP in human serum samples are in the range 96.1-110.9% with the RSD of 1.4 to 3.2%. The amount of 6-MP is successfully estimated as 49.3 mg in pharmaceutical tablet with the RSD of about  2.2%.

Predictive value of blood concentration of biologics on endoscopic inactivity in inflammatory bowel disease: A systematic review

BACKGROUND

Although blood concentration of biologics is an important composition of disease management in inflammatory bowel disease (IBD) patients, complexity and uncertainty of biological management encourage many disputes in predicting the outcome of IBD patients through blood concentration of biologics.

AIM

To verify the predictive value of blood concentration of biologics on endoscopic inactivity in IBD patients under different situations.

METHODS

We searched PubMed/MEDLINE, Embase, and Web of Science up to May 2020 and identified IBD patients as the research cohort as well as the correlations between blood concentration of biologics and endoscopic inactivity in IBD patients as the research direction.

RESULTS

A total of 23 articles with 30 clinical studies and 1939 IBD patients were included. The predictive cut-off value of blood concentration of infliximab on mucosal healing should be 2.7-10.6 μg/mL in IBD. Blood concentration of infliximab reaching 5.0-12.7 μg/mL or more increased the probability of fistula healing/closure in perianal fistulizing Crohn's disease. Blood concentration of adalimumab reaching 7.2-16.2 μg/mL or more could predict mucosal healing in IBD. The predictive cut-off value of blood concentration of adalimumab on fistula healing/closure should be 5.9-9.8 μg/mL in perianal fistulizing Crohn's disease. Blood concentration of vedolizumab surpassing 25.0 μg/mL indicated mucosal healing in ulcerative colitis patients under maintenance therapy and the predictive cut-off value of blood concentration on mucosal healing or endoscopic remission under induction therapy in IBD could be 8.0-28.9 μg/mL.

CONCLUSION

Blood concentration of biologics should not be utilized to predict endoscopic inactivity of IBD independently due to discrepancies in clinical studies, whereas conducting therapeutic drug monitoring intensively contributes to precise therapy.

TPMT Genetic Variability and Its Association with Hematotoxicity in Indonesian Children with Acute Lymphoblastic Leukemia in Maintenance Therapy

PURPOSE

Hematotoxicity monitoring in children with acute lymphoblastic leukemia (ALL) is critical to preventing life-threatening infections and drug discontinuation. The primary drug that causes hematotoxicity in ALL children is 6-mercaptopurine (6-MP). Genetic variability of the drug-metabolizing enzymes of 6-MP, thiopurine S-methyltransferase (TPMT), is one factor that might increase the susceptibility of children to hematotoxicity. The present study aimed to determine the variability in TPMT genotypes and phenotypes and its association with the occurrence of hematotoxicity in ALL children in maintenance therapy.

PATIENTS AND METHODS

A cross-sectional study was conducted at Cipto Mangunkusumo and Dharmais National Cancer Hospital, Jakarta, Indonesia, from June 2017 to October 2018. We included ALL patients, 1-18 years, who were receiving at least one month of 6-MP during maintenance therapy according to the Indonesian protocol for ALL 2013. Direct sequencing was used to determine TPMT*3A, *3B, and *3C genotypes, and LC-MS/MS analysis was performed to measure the plasma concentrations of 6-MP and its metabolites. Association analysis between the TPMT genotype and hematotoxicity was evaluated using the unpaired t-test or Mann-Whitney's test.

RESULTS

The prevalence of neutropenia, anemia, and thrombocytopenia in ALL children during maintenance therapy was 51.9%, 44.3%, and 6.6%, respectively. We found a low frequency of TPMT*3C, which is 0.95%. No association was found between hematotoxicity and TPMT genotypes or age, nutritional status, serum albumin levels, risk stratification, the daily dose of 6-MP, and cotrimoxazole co-administration. However, hematotoxicity was associated with 6-methylmercaptopurine (6-MeMP) plasma concentrations and the ratio 6-MeMP/6-thioguanine (6-TGN). We also found no association between TPMT genotypes and TPMT phenotypes.

CONCLUSION

The 6-MeMP/6-TGN ratio is associated with hematotoxicity in ALL children during maintenance therapy but is not strong enough to predict hematotoxicity.

Investigation of nanotubes as the smart carriers for targeted delivery of mercaptopurine anticancer drug

Mercaptopurine (MCP) is an anticancer drug that is used to treat acute lymphoblastic leukemia. The therapeutic effect of the mercaptopurine limits its severe side effects like other cytotoxic (anti-cancer) drugs. Nanostructures or nanoparticles can be widely used as potential drug carriers for diagnosis and treatment of cancer. In the current study, the boron nitride nanotube (BNNT) and carbon nanotube (CNT) were studied as the delivery carriers of MCP using the density functional theory (DFT) calculations and molecular dynamics (MDs) simulation studies. To further understand the electronic properties of mercaptopurine, the partial density of states (PDOS) was calculated. The PDOS results depicted that the electronic features of the MCP do not change after the adsorption on the surface of the nanotubes. More stability of the MCP/BNNT complexes may be attributed to the existence of the intermolecular hydrogen bonds (H-bonds) between the hydrogen atoms of the MCP molecule and the N atoms of the BNNT. The results of the quantum theory of atoms in molecules (QTAIM) confirmed the presence of H-bonds in these complexes. Moreover, MD simulation studies were done in the presence of five drug molecules. The results revealed that the strongest van der Waals (vdW) interaction energy was found between the BNNT and MCP among the studied nanotubes, indicating the BNNT is a better nanocarrier than carbon nanotube for delivery of the MCP drug within the biological systems. In general, the obtained results may present helpful information on the nature of the interactions between mercaptopurine anticancer drug with BNNT and/or CNT.Communicated by Ramaswamy H. Sarma.

The Identification of a Novel Thiopurine S-Methyltransferase Allele, TPMT*45, in Korean Patient with Crohn's Disease

Pediatric Crohn’s disease (CD) carries a higher genetic susceptibility and an increased risk of a more aggressive disease course than adult CD. Treatment of CD is based on immunomodulatory drugs, such as thiopurines. The enzyme mainly involved in drug metabolism is thiopurine S-methyltransferase (TPMT). An increased concentration of drug metabolites can cause adverse drug effects, such as myelosuppression and hepatotoxicity; therefore, assessing the activity of TPMT is essential both before and during treatment. TPMT genotyping result is not affected by previous thiopurine dose and currently is the primary component of TPMT activity and disease monitoring. Until now, more than 40 allelic variants of the TPMT gene have been reported, with most of them having an uncertain or no enzyme function. In this article, we report the first case of a novel TPMT allele, TPMT*45, that was identified in a Korean girl with CD whose findings suggested decreased TPMT activity. This newly observed variant is caused by a single nucleotide polymorphism resulting in nonsense mutation (c.676C>T, p.R226*) and the partial loss of amino acids in the TPMT protein. Initially, the patient began azathioprine at a standard dosage (1.5 mg/kg/day), and her laboratory results, including red blood cell (RBC) TPMT activity (6-methylmercaptopurine 2.68 nmol/mL/h and 6-methylmercaptopurine riboside 4.82 nmol/mL/h) along with thiopurine metabolite levels (6-thioguanine nucleotides 479.3 pmol/8×10⁸ RBC), suggested an enzyme deficiency. The thiopurine dose was reduced to half (0.7 mg/kg/day), and the follow-up metabolite results as well as the associated inflammatory markers were continuously within reference ranges. Along with an improvement in the patient’s subjective reports and clinical symptoms, the patient demonstrated a good treatment response to the adjusted dose. The results of our report illustrate the importance of TPMT genotyping and pharmacogenetic-based thiopurine dose adjustment. Further research should focus on the functional characterization and impact on this novel allele’s treatment effect.

Population pharmacokinetics of azathioprine active metabolite in patients with inflammatory bowel disease and dosage regimens optimisation

Azathioprine is a first-line drug used to maintain the remission of inflammatory bowel disease (IBD). As a prodrug, azathioprine is metabolised to produce active 6-thioguanine nucleotides (6-TGN). There are large individual variations in the pharmacokinetics/pharmacodynamics of 6-TGN in patients with IBD. Here, we aimed to develop a model to quantitatively investigate factors that affect 6-TGN pharmacokinetics to formulate a dosage guideline for azathioprine. Data were collected prospectively from 100 adult patients with IBD who were receiving azathioprine. Patients were genotyped for two single-nucleotide polymorphisms (TPMT*3C c.719A > G and NUDT15 c.415C > T). Using high-performance liquid chromatography, we measured 156 steady-state trough concentrations of 6-TGN within the range 0.09 to 1.16 mg/L (ie 133-1733 pmol per 8 × 10⁸ RBC). The covariates analysed included sex, age, body-weight, laboratory tests and concomitant medications. A population pharmacokinetic model was established using "non-linear mixed-effects modelling" software and the "first-order conditional estimation method with interaction." Body-weight, TPMT*3C polymorphisms and co-therapy with mesalazine were found to be important factors influencing the clearance of 6-TGN. A dosage guideline for azathioprine was developed based on the PPK model that enables individualised azathioprine dosing in adult patients with different body-weights, TPMT*3C genotypes and co-administration with mesalazine.

Ratiometric fluorescent nanoprobe based on CdTe/SiO2/folic acid/silver nanoparticles core-shell-satellite assembly for determination of 6-mercaptopurine

A sensitive and robust fluorescent assay of 6-MP is described which relies on the facile assembly of a fluorescence nanoprobe by design of silica nanosphere encapsulated CdTe quantum dots (CdTe QDs) as scaffold, coupling with chemically tethered folic acid (FA)-protected silver nanoparticles (AgNPs) that function as responsive element. In this way a stable ternary core-shell-satellite nanostructure with dual-emission signals can be established. On binding to the target molecules, 6-MP, FA molecules initially occupied by AgNPs are liberated to give dose-dependent fluorescence emission, which can further form a self-calibration ratiometric fluorescence assay using CdTe QDs as an internal reference. The nanoprobe color vividly changes from red to blue, enabling the direct visual detection. The linear concentration range is 0.15~50 μM with the detection limit of 67 nM. By virtue of the favorable selectivity and robust assays, the nanoprobe was applied to 6-MP detection in urine samples, with recoveries from 97.3 to 106% and relative standard deviations (RSD) less than 5%. Graphical abstract.

Pharmacogenetic studies of thiopurine methyltransferase genotype-phenotype concordance and effect of methotrexate on thiopurine metabolism

The discovery and implementation of thiopurine methyltransferase (TPMT) pharmacogenetics has been a success story and has reduced the suffering from serious adverse reactions during thiopurine treatment of childhood leukaemia and inflammatory bowel disease. This MiniReview summarizes four studies included in Dr Zimdahl Kahlin's doctoral thesis as well as the current knowledge on this field of research. The genotype‐phenotype concordance of TPMT in a cohort of 12 663 individuals with clinically analysed TPMT status is described. Notwithstanding the high concordance, the benefits of combined genotyping and phenotyping for TPMT status determination are discussed. The results from the large cohort also demonstrate that the factors of gender and age affect TPMT enzyme activity. In addition, characterization of four previously undescribed TPMT alleles (TPMT*41, TPMT*42, TPMT*43 and TPMT*44) shows that a defective TPMT enzyme could be caused by several different mechanisms. Moreover, the folate analogue methotrexate (MTX), used in combination with thiopurines during maintenance therapy of childhood leukaemia, affects the metabolism of thiopurines and interacts with TPMT, not only by binding and inhibiting the enzyme activity but also by regulation of its gene expression.

Safety of Thiopurine Use in Paediatric Gastrointestinal Disease

Thiopurines, alone or in combination with other agents, have a pivotal role in the treatment of specific gastrointestinal and hepatological disorders. In inflammatory bowel disease and autoimmune hepatitis thiopurines have proven their value as steroid sparing agents for the maintenance of remission and may be considered for preventing postoperative Crohn disease recurrence where there is moderate risk of this occurring. Their use with infliximab therapy reduces antibody formation and increases biologic drug levels. The routine clinical use of thiopurines has, however, been questioned due to a number of potential adverse effects. The aim of this article is to provide information regarding the use, and in particular, safety of these agents in clinical practice in the light of such potentially severe, albeit rare, effects.

Elucidating the binding mechanism of thione-containing mercaptopurine and thioguanine drugs to small gold clusters

Density functional theory methods were employed to clarify the adsorption/desorption behaviors of the thione-containing mercaptopurine and thioguanine drugs on the gold surface using both small Au₆ and Au₈ clusters as model reactants. Structural features, thermodynamic parameters, bonding characteristics, and electronic properties of the resulting complexes were investigated using the Perdew-Burke-Ernzerhof (PBE) and LC-BLYP functionals along with correlation-consistent basis sets, namely cc-pVDZ-PP for gold and cc-pVTZ for non-metals. Computed results show that the drug molecules tend to anchor on the gold cluster at the S atom with binding energies around -34 to -40 kcal/mol (in vacuum) and - 28 to -32 kcal/mol (in aqueous solution). As compared to Au₈ , Au₆ undergoes a shorter recovery time and a larger change of energy gap that could be converted to an electrical signal for selective detection of the drugs. Furthermore, interactions between the drugs and gold clusters are reversible processes and a drug release mechanism was also proposed. Accordingly, the drugs are able to separate from the gold surface due to either a slight change of pH in tumor cells or the presence of cysteine residues in protein matrices.

Precision medicine for rheumatologists: lessons from the pharmacogenomics of azathioprine

Precision medicine aims to personalize treatment for both effectiveness and safety. As a critical component of this emerging initiative, pharmacogenomics seeks to guide drug treatment based on genetics. In this review article, we give an overview of pharmacogenomics in the setting of an immunosuppressant frequently prescribed by rheumatologists, azathioprine. Azathioprine has a narrow therapeutic index and a high risk of adverse events. By applying candidate gene analysis and unbiased approaches, researchers have identified multiple variants associated with an increased risk for adverse events associated with azathioprine, particularly bone marrow suppression. Variants in two genes, TPMT and NUDT15, are widely recognized, leading drug regulatory agencies and professional organizations to adopt recommendations for testing before initiation of azathioprine therapy. As more gene-drug interactions are discovered, our field will continue to face the challenge of balancing benefits and costs associated with genetic testing. However, novel approaches in genomics and the integration of clinical and genetic factors into risk scores offer unprecedented opportunities for the application of pharmacogenomics in routine practice. Key Points • Pharmacogenomics can help us understand how individuals' genetics may impact their response to medications. • Azathioprine is a success story for the clinical implementation of pharmacogenomics, particularly the effects of TPMT and NUDT15 variants on myelosuppression. • As our knowledge advances, testing and dosing recommendations will continue to evolve, with our field striving to balance costs and benefits to patients. • As we aim toward the goals of precision medicine, future research may integrate increasingly individualized traits-including clinical and genetic characteristics-to predict the safety and efficacy of particular medications for individual patients.

Pancreatitis associated with azathioprine and 6-mercaptopurine use in Crohn's disease: a systematic review

Thiopurines are proven agents in the treatment of Crohn's disease. While pancreatitis is recognised as an adverse event associated with therapy, the effect size and morbidity of thiopurine-induced pancreatitis is not known. The aim of this systematic review and meta-analysis was to quantify the risk of pancreatitis with azathioprine and 6-mercaptopurine (6-MP) within Crohn's disease. We searched six electronic databases from inception to 29 October 2019. The primary outcomes measures were the occurrence of pancreatitis. We calculated pooled OR with corresponding 95% CIs for risk of pancreatitis. A number needed to harm analysis was performed. The search identified 4418 studies, of which 25 randomised controlled trials met the criteria for inclusion. The number of patients treated with azathioprine to cause an episode of pancreatitis was 36 (induction of remission) and 31 (maintenance of remission). The risk of pancreatitis in patients receiving azathioprine across all contexts was 3.80%, compared with a control risk of 0.2% (placebo) and 0.5% (5-aminosalicylic acid agents). There was no difference seen between 6-MP and placebo, although this was a low certainty result due to imprecision from very low event numbers and patient numbers. There is a probably increased occurrence of pancreatitis when azathioprine is used in Crohn's disease (moderate certainty), with incidence overall approximately 3.8%. Most cases are mild and resolve on cessation of therapy and no mortality was reported. There was no increased occurrence seen when using 6-MP, although this is a low certainty finding. PROSPERO prior to the study (CRD42019138065).

Review article: opportunities to improve and expand thiopurine therapy for autoimmune hepatitis

BACKGROUND

Thiopurines in combination with glucocorticoids are used as first-line, second-line and maintenance therapies in autoimmune hepatitis and opportunities exist to improve and expand their use.

AIMS

To describe the metabolic pathways and key factors implicated in the efficacy and toxicity of the thiopurine drugs and to indicate the opportunities to improve outcomes by monitoring and manipulating metabolic pathways, individualising dosage and strengthening the response.

METHODS

English abstracts were identified in PubMed by multiple search terms. Full-length articles were selected for review, and secondary and tertiary bibliographies were developed.

RESULTS

Thiopurine methyltransferase activity and 6-tioguanine (6-thioguanine) nucleotide levels influence drug efficacy and safety, and they can be manipulated to improve treatment response and prevent myelosuppression. Methylated thiopurine metabolites are associated with hepatotoxicity, drug intolerance and nonresponse and their production can be reduced or bypassed. Universal pre-treatment assessment of thiopurine methyltransferase activity and individualisation of dosage to manipulate metabolite thresholds could improve outcomes. Early detection of thiopurine resistance by metabolite testing, accurate estimations of drug onset and strength by surrogate markers and adjunctive use of allopurinol could improve the management of refractory disease. Dose-restricted tioguanine (thioguanine) could expand treatment options by reducing methylated metabolites, increasing the bioavailability of 6-tioguanine nucleotides and ameliorating thiopurine intolerance or resistance.

CONCLUSIONS

The efficacy and safety of thiopurines in autoimmune hepatitis can be improved by investigational efforts that establish monitoring strategies that allow individualisation of dosage and prediction of outcome, increase bioavailability of the active metabolites and demonstrate superiority to alternative agents.

Magnetite Fe3O4 surface as an effective drug delivery system for cancer treatment drugs: density functional theory study

In this paper, the magnetite Fe₃O₄ surface was studied as a drug delivery system for the two commercially famous cancer treatment drugs, including Cisplatin and Mercaptopurine, using the density functional theory (DFT) computations. Adsorption properties, magnetic and electronic properties were calculated. Results indicate that the adsorptions are thermodynamically favorable and binding energies were decreased by increasing the concentration of the ligands adsorption on the Fe₃O₄ surface. Our spin-polarized calculations determine that the magnetization of all systems is greater than the pristine magnetite Fe₃O₄ surface witch is vital for drug delivery and magnetic hyperthermia. This study provides a deep understanding of the interaction mechanism at the atomistic scale and proposed that magnetite Fe₃O₄ could be employed as an efficient drug carrier.Communicated by Ramaswamy H. Sarma.

Sulfonyl Group Dance: A Tool for the Synthesis of 6-Azido-2-sulfonylpurine Derivatives

9-Substituted 2-chloro-6-sulfonylpurines provide 6-azido-2-sulfonylpurine derivatives with 61-83% yields when treated with sodium azide. Under optimized reaction conditions, the title compounds are obtained in a one-pot process, which involves a sequential treatment of 2,6-dichloropurines with a selected sodium sulfinate and sodium azide. Such a sulfonyl group dance (functional group swap) results from a cascade of S_NAr reactions, which are facilitated by azidoazomethine-tetrazole (azide-tetrazole) tautomeric equilibrium. The formation of Meisenheimer-type intermediates as tetrazolopurine tautomers was supported by various spectroscopic methods, including ¹⁵N NMR.

Predict New Therapeutic Drugs for Hepatocellular Carcinoma Based on Gene Mutation and Expression

Hepatocellular carcinoma (HCC) is the fourth most common primary liver tumor and is an important medical problem worldwide. However, the use of current therapies for HCC is no possible to be cured, and despite numerous attempts and clinical trials, there are not so many approved targeted treatments for HCC. So, it is necessary to identify additional treatment strategies to prevent the growth of HCC tumors. We are looking for a systematic drug repositioning bioinformatics method to identify new drug candidates for the treatment of HCC, which considers not only aberrant genomic information, but also the changes of transcriptional landscapes. First, we screen the collection of HCC feature genes, i.e., kernel genes, which frequently mutated in most samples of HCC based on human mutation data. Then, the gene expression data of HCC in TCGA are combined to classify the kernel genes of HCC. Finally, the therapeutic score (TS) of each drug is calculated based on the kolmogorov-smirnov statistical method. Using this strategy, we identify five drugs that associated with HCC, including three drugs that could treat HCC and two drugs that might have side-effect on HCC. In addition, we also make Connectivity Map (CMap) profiles similarity analysis and KEGG enrichment analysis on drug targets. All these findings suggest that our approach is effective for accurate predicting novel therapeutic options for HCC and easily to be extended to other tumors.

Is there room for immunomodulators in ulcerative colitis?

Introduction: The management of patients with ulcerative colitis (UC) has evolved over the past few decades. While aminosalicylates remain the mainstay of induction and maintenance therapy in patients with mild-to-moderate UC, the advent of biologic agents and novel oral small molecules has substantively changed the treatment landscape for patients with moderate-to-severe disease and confounded the role of traditional immunomodulators (IMMs) such as thiopurines and methotrexate in the UC management algorithm.Areas covered: We summarize the mechanism of action of thiopurines and methotrexate, identify clinical parameters for their use, and appraise the evidence supporting the efficacy and safety of IMMs in UC as both monotherapy and in combination with other therapies, emphasizing on prospective, controlled data.Expert opinion: With the advent of several classes of highly effective treatments for UC, emergence of data demonstrating no benefit of IMMs over placebo, and concerns about the relative safety profile of long-term IMM exposure, we propose that the role of thiopurines or methotrexate be restricted to patients with milder disease failing to maintain corticosteroid-free remission on aminosalicylates alone or in combination therapy with tumor necrosis factor antagonists in patients with moderate-to-severe UC.

Juvenile-onset systemic lupus erythematosus: Update on clinical presentation, pathophysiology and treatment options

Juvenile-onset systemic lupus erythematosus (jSLE) accounts for up to 20% of all SLE patients. Key differences between juvenile- and adult-onset (aSLE) disease include higher disease activity, earlier development of damage, and increased use of immunosuppressive treatment in jSLE suggesting (at least partial) infectivity secondary to variable pathomechanisms. While the exact pathophysiology of jSLE remains unclear, genetic factors, immune complex deposition, complement activation, hormonal factors and immune cell dysregulation are involved to variable extents, promising future patient stratification based on immune phenotypes. Though less effective and potentially toxic, jSLE patients are treated based upon evidence from studies in aSLE cohorts. Here, age-specific clinical features of jSLE, underlying pathomechanisms, treatment options and disease outcomes will be addressed. Future directions to improve the care of jSLE patients, including implementation of the Single Hub and Access point for pediatric Rheumatology in Europe (SHARE) recommendations, biomarkers, treat to target and personalized medicine approaches are discussed.

Clinical Pharmacokinetic and Pharmacodynamic Considerations in the Treatment of Inflammatory Bowel Disease

According to recent clinical consensus, pharmacotherapy of inflammatory bowel disease (IBD) is, or should be, personalized medicine. IBD treatment is complex, with highly different treatment classes and relatively few data on treatment strategy. Although thorough evidence-based international IBD guidelines currently exist, appropriate drug and dose choice remains challenging as many disease (disease type, location of disease, disease activity and course, extraintestinal manifestations, complications) and patient characteristics [(pharmaco-)genetic predisposition, response to previous medications, side-effect profile, necessary onset of response, convenience, concurrent therapy, adherence to (maintenance) therapy] are involved. Detailed pharmacological knowledge of the IBD drug arsenal is essential for choosing the right drug, in the right dose, in the right administration form, at the right time, for each individual patient. In this in-depth review, clinical pharmacodynamic and pharmacokinetic considerations are provided for tailoring treatment with the most common IBD drugs. Development (with consequent prospective validation) of easy-to-use treatment algorithms based on these considerations and new pharmacological data may facilitate optimal and effective IBD treatment, preferably corroborated by effectiveness and safety registries.

Purine-Metabolising Enzymes and Apoptosis in Cancer

The enzymes of both de novo and salvage pathways for purine nucleotide synthesis are regulated to meet the demand of nucleic acid precursors during proliferation. Among them, the salvage pathway enzymes seem to play the key role in replenishing the purine pool in dividing and tumour cells that require a greater amount of nucleotides. An imbalance in the purine pools is fundamental not only for preventing cell proliferation, but also, in many cases, to promote apoptosis. It is known that tumour cells harbour several mutations that might lead to defective apoptosis-inducing pathways, and this is probably at the basis of the initial expansion of the population of neoplastic cells. Therefore, knowledge of the molecular mechanisms that lead to apoptosis of tumoural cells is key to predicting the possible success of a drug treatment and planning more effective and focused therapies. In this review, we describe how the modulation of enzymes involved in purine metabolism in tumour cells may affect the apoptotic programme. The enzymes discussed are: ectosolic and cytosolic 5'-nucleotidases, purine nucleoside phosphorylase, adenosine deaminase, hypoxanthine-guanine phosphoribosyltransferase, and inosine-5'-monophosphate dehydrogenase, as well as recently described enzymes particularly expressed in tumour cells, such as deoxynucleoside triphosphate triphosphohydrolase and 7,8-dihydro-8-oxoguanine triphosphatase.

Assessment of dynamical properties of mercaptopurine on the peptide-based metal-organic framework in response to experience of external electrical fields: a molecular dynamics simulation

In this work, the effect of the external electric field (EF) on the drug delivery performance of peptide-based metal-organic framework (MPF) for 6-mercaptopurine (6-MP) drug is investigated by means of the molecular dynamics (MD) simulations. It is found that the strength interaction of drug molecule with MPF is decreased under the influence of the electric field. In other words, the adsorbed drug molecules have more tendencies for the interaction with the porous nanostructure in the absence of EF. According to the radial distribution function (RDF) patterns, the probability of finding drug molecules in terms of the intermolecular distance with respect to the MPF surface is lowest during the high field strength. As the EF strength increases, the spread of drug molecules around MPF results in high dynamics movement and further more diffusion coefficient of drug molecule in the simulation system. This result emphasizes the weak intermolecular interaction of drug molecules with MPF with the application of EF. Assessment of dynamical properties of 6-mercaptopurine in the presence of EF with various strengths reveals that the applied electric field can act as a trigger on liberation behavior of drug from the porous nanostructure.

Azathioprine and 6-mercaptopurine for maintenance of surgically-induced remission in Crohn's disease

BACKGROUND

Crohn's disease (CD) is a chronic relapsing inflammatory condition and maintenance of remission is a major issue as many patients fail to achieve remission with medical management and require surgical interventions. Purine analogues such as azathioprine (AZA) and 6-mercaptopurine (6-MP) have been used to maintain surgically-induced remission in CD, but the effectiveness, tolerability and safety of these agents remains controversial.

OBJECTIVES

To assess the efficacy and safety of purine analogues (AZA and 6-MP) for maintenance of surgically-induced remission in CD.

SEARCH METHODS

We searched PubMed, MEDLINE, Embase, CENTRAL, and the Cochrane IBD Group Specialized Register from inception to 26 July 2018 (and from inception to 31 July 2019). In addition, we searched reference lists of all included studies and relevant reviews, conference proceedings and trials registers.

SELECTION CRITERIA

Randomised controlled trials (RCTs) with a duration of at least three months that enrolled adults and children with surgically-induced remission of CD and compared AZA or 6-MP to no treatment, placebo or any other active intervention were considered for inclusion.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial eligibility, extracted data, assessed the risk of bias and assessed the certainty of the evidence using GRADE. The primary outcome was clinical relapse. Secondary outcomes included endoscopic relapse, radiologic and surgical relapse, adverse events (AEs), serious adverse events (SAEs), withdrawal due to AEs and health-related quality of life.

MAIN RESULTS

Ten RCTs with a total of 928 participants were included. Study participants were adults recruited from university clinics and gastroenterology hospitals who received interventions post-surgery for a duration between 12 to 36 months. Most study participants were recruited less than three months after surgery in all except one study where participants were recruited between 6 to 24 months post-surgery. One study was rated as low risk of bias, six studies were rated high risk of bias and three were rated unclear risk of bias.There was moderate certainty evidence that purine analogues are more efficient for preventing clinical relapse than placebo. At 12 to 36 months, 51% (109/215) of AZA/6-MP participants relapsed compared to 64% (124/193) of placebo participants (RR 0.79; 95% CI 0.67 to 0.92; 408 participants; 3 studies; I² = 0%; moderate certainty evidence). The certainty of the evidence regarding the efficacy of AZA or 6-MP for maintaining postoperative clinical remission compared to 5-ASA compounds was low. At 12 to 24 months , 64% (113/177) of purine analogue participants relapsed compared to 59% (101/170) of 5-ASA participants (RR 1.05; 95% CI 0.89 to 1.24; 347 participants; 4 studies; I² = 8%; low certainty evidence). The certainty of evidence that purine analogues are inferior for preventing postsurgical clinical relapse compared to tumour necrosis factor alpha agents (anti-TNF-α) was very low. At 12 to 24 months, 43% (29/67) of AZA participants relapsed compared to 14% (10/72) of anti-TNF-α participants (RR 2.89; 95% CI 1.50 to 5.57; 139 participants; 3 studies; I² = 0%; very low certainty evidence).The effect of purine analogues compounds on AEs compared to placebo or any active treatment was uncertain, as the quality of evidence ranged from very low to low. After 12 to 24 months, 14% (12/87) of purine analogue participants experienced an AE compared to 10% (8/81) of placebo participants (RR 1.36; 95% CI 0.57 to 3.27; 168 participants; 2 studies; I² = 0%; low certainty evidence). The effect of purine analogues on AEs compared to 5-ASA agents was uncertain. After 12 to 24 months, 41% (73/176) of purine analogue participants had an AE compared to 47% (81/171) of 5-ASA participants (RR 0.89; 95% CI 0.74 to 1.07; 346 participants; 4 studies; I² = 15%; low certainty evidence). The effect of purine analogues on AEs in comparison to anti TNF-α agents was uncertain. At 12 to 24 months, 57% (32/56) of AZA participants had an AE compared to 51% (31/61) of anti-TNF-α participants (RR 1.13; 95% CI 0.83 to 1.53; 117 participants; 2 studies; I² = 0%; low certainty evidence). Purine analogue participants were more like than 5-ASA participants to have a SAE (RR 3.39, 95% CI 1.26 to 9.13, 311 participants; 3 studies; I² = 9%; very low certainty evidence), or to withdraw due to an AE (RR 2.21, 95% CI 1.28 to 3.81; 425 participants; 5 studies; I² = 0%; low certainty evidence). Commonly reported AEs across all studies included leucopenia, arthralgia, abdominal pain or severe epigastric intolerance, elevated liver enzymes, nausea and vomiting, pancreatitis, anaemia, nasopharyngitis and flatulence.

AUTHORS' CONCLUSIONS

Moderate certainty evidence suggests that AZA and 6-MP may be superior to placebo for maintenance of surgically-induced remission in participants with CD. There was no clear difference in the number of clinical relapses when purine analogues were compared with 5-ASA agents, however this is based on low certainty evidence. There was very low certainty evidence that AZA and 6-MP are more likely to result in more serious adverse events (SAEs) and withdrawals due to an AE (low certainty) when compared to 5-ASA agents. Very low certainty evidence suggests that purine analogues may be inferior to anti-TNF-α agents, however, no firm conclusions can be drawn. Further research investigating the efficacy and safety of AZA and 6-MP in comparison to other active medications in surgically-induced remission of CD is warranted.

Immunosuppressive therapies adversely affect blood biochemical parameters in patients with inflammatory bowel disease: a meta-analysis

Objective

This study was performed to investigate whether a definite correlation exists between alteration of blood biochemical parameters and immunosuppressive therapies in patients with inflammatory bowel disease (IBD).

Methods

A comprehensive search of PubMed, EMBASE, MEDLINE, and the Cochrane Library was conducted. Data on alterations in white blood cells, platelets, hemoglobin, serum creatinine, and liver enzymes in patients with IBD treated with immunomodulators were extracted.

Results

Data from 1141 patients were included. The relative risk (RR) of leukopenia was significantly higher in the immunosuppressive therapies group than in the placebo group (RR, 12.91; 95% confidence interval [CI], 5.28–31.57). A statistically significant risk of leukocytosis during immunosuppressive therapies was observed (RR, 1.53; 95% CI, 1.05–2.23). Patients taking immunomodulators had increased risks of serum creatinine elevation (RR, 10.68; 95% CI, 2.07–55.12) and serum aminotransferase elevation (RR, 3.18; 95% CI, 1.24–8.17).

Conclusion

Immunosuppressive therapies might have an impact on variations in blood biochemical parameters in patients with IBD. Although the conclusion regarding leukopenia was reliable in this study, some confounding factors might reduce the reliability of the conclusions about leukocytosis, creatinine elevation, and aminotransferase elevation. Close monitoring is recommended during immunosuppressive therapies for IBD.

The stilbene derivatives, nucleosides, and nucleosides modified by stilbene derivatives

In this short review, including 187 references, the issues of biological activity of stilbene derivatives and nucleosides and the biological and medicinal potential of fusion of these two classes are discussed. The stilbenes, especially the stilbenoids, and nucleosides are both biologically active. Hybrids formed from binding of these compounds have not yet been broadly studied. However, those that have been investigated exhibit desirable medicinal properties. The review is divided in such parts: I. Derivative of stilbene (biomedical investigations, biological activities in cells, enzymes and hazard), parts II. naturally occurred nucleoside and its derivatives: uridine, thymidine and 5-methyluridine, cytidine, adenosine, guanosine and part III. hybrid molecules- drugs and hybrid molecules- nucleoside - stilbene and its derivative.

Efficacy and tolerability of azathioprine for neuromyelitis optica spectrum disorder: A systematic review and meta-analysis

BACKGROUND

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory and autoimmune disorder of the central nervous system that typically presents with optic neuritis and myelitis. Azathioprine (AZA) is one of the available immunotherapies with purported beneficial effects for patients with NMOSD. At present, there are no systematic reviews that extensively pooled the effects of AZA compared to other interventions for this condition. The objective of this study, therefore, is to determine the efficacy and safety of AZA in patients with NMOSD using systematic review of relevant studies.

METHODS

Major health electronic databases, which included CENTRAL, MEDLINE, EMBASE, Scopus, LILACS, ClinicalTrials.gov, and HERDIN, were searched from May 2017 to November 2018 for relevant studies involving adult and pediatric patients with NMOSD. Randomized controlled trials, and either prospective or retrospective cohort designs that assessed the reduction or prevention of relapse or disability and the occurrence of adverse events related to AZA use compared to placebo or to other active drugs were considered. Assessment of risk of bias was performed using the Cochrane Collaboration tool and Newcastle-Ottawa Scale.

RESULTS

From a total of 273 records, 9 relevant studies (1 randomized controlled trial (RCT), 3 prospective cohort studies, 5 retrospective studies) which involved a total of 977 patients, were included. One RCT and several observational studies revealed that AZA regimen may be inferior to rituximab in terms of annualized relapse rate, reduction of disability as measured by the expanded disability status scale (EDSS), risk for relapse and relapse-free rate. Efficacy data were very limited in the comparison of AZA to mycophenolate mofetil (MMF), to cyclophosphamide, and to interferon-β for patients with NMOSD. Occurrence of any adverse event, elevated liver enzymes/hepatoxicity, leukopenia and hair loss associated with AZA use were significantly greater compared to MMF, which may lead to medication noncompliance.

CONCLUSION

AZA improves relapses and disability in patients with NMOSD but this regimen is associated with relatively frequent adverse events based on limited published evidences. More well-conducted clinical trials are necessary to establish with certainty the beneficial and harmful effects of AZA in patients with NMOSD.

Comprehensive study of thiopurine methyltransferase genotype, phenotype, and genotype-phenotype discrepancies in Sweden

Thiopurines are widely used in the treatment of leukemia and inflammatory bowel diseases. Thiopurine metabolism varies among individuals because of differences in the polymorphic enzyme thiopurine methyltransferase (TPMT, EC 2.1.1.67), and to avoid severe adverse reactions caused by incorrect dosing it is recommended that the patient's TPMT status be determined before the start of thiopurine treatment. This study describes the concordance between genotyping for common TPMT alleles and phenotyping in a Swedish cohort of 12,663 patients sampled before or during thiopurine treatment. The concordance between TPMT genotype and enzyme activity was 94.5%. Compared to the genotype, the first measurement of TPMT enzyme activity was lower than expected for 4.6% of the patients. Sequencing of all coding regions of the TPMT gene in genotype/phenotype discrepant individuals led to the identification of rare and novel TPMT alleles. Fifteen individuals (0.1%) with rare or novel genotypes were identified, and three TPMT alleles (TPMT*42, *43, and *44) are characterized here for the first time. These 15 patients would not have been detected as carrying a deviating TPMT genotype if only genotyping of the most common TPMT variants had been performed. This study highlights the benefit of combining TPMT genotype and phenotype determination in routine testing. More accurate dose recommendations can be made, which might decrease the number of adverse reactions and treatment failures during thiopurine treatment.

Fe@(Au/Ag)n (n=1,12,54) core-shell nanoparticles as effective drug delivery vehicles for anti-cancer drugs: The computational study

In this paper, we study magnetic and structural properties of silver and gold-coated iron nanoparticle as novel drug delivery systems for the two commercially famous cancer treatment drugs, using the density functional theory (DFT) computations. Our calculations show that silver and gold-coated iron nanoparticle have magnetization and the magnetic moment of the Fe atom in the Fe@(Ag/Au)_n core-shells saturated to a value of about 3 μ_B. Thus the Fe@(Ag/Au)_n core-shells are very promising to be functionalized for targeted drug delivery. Drug adsorption on the Gold coated iron show higher adsorption energy than Fe@Ag₁₂ core-shell, Also, Mercaptopurine molecules showed higher adsorption energy than the Cisplatin. The Fe@Ag₁₂ core-shells can deliver the drug into the cells while their properties are not significantly changed in the delivering process. Simulation results also have shown that in the low pH of tissue of a malignant tumor, the drug can be separated from the carrier which indicating the potential delivery vehicle of iron core-shells. Results of the calculations for core-shell structure of iron nanoparticle are very promising in biomedical applications and will contribute to the discovery of its novel applications in nanomedicine.

Vaccinations in kidney transplant recipients: Clearing the muddy waters

Vaccine preventable diseases account for a significant proportion of morbidity and mortality in transplant recipients and cause adverse outcomes to the patient and allograft. Patients should be screened for vaccination history at the time of pre-transplant evaluation and vaccinated at least four weeks prior to transplantation. For non-immune patients, dead-vaccines can be administered starting at six months post-transplant. Live attenuated vaccines are contraindicated after transplant due to concern for infectious complications from the vaccine and every effort should be made to vaccinate prior to transplant. Since transplant recipients are on life-long immunosuppression, these patients may have lower rates of serological conversion, lower mean antibody titers and waning of protective immunity over shorter period as compared to general population. Recommendations regarding booster dose in kidney transplant recipients with sub-optimal serological response are lacking. Travel plans should be part of routine post-transplant assessment and pre-travel vaccines and counseling should be provided. More studies are needed on vaccination schedules, serological response, need for booster doses and safety of live attenuated vaccines in this special population.

Mitochondrial neurogastrointestinal encephalopathy: a clinicopathological mimic of Crohn's disease

Background

Mitochondrial neurogastrointestinal encephalopathy (MNGIE), due to mutations in TYMP, often presents with gastrointestinal symptoms. Two sisters, initially managed for Crohn’s disease based upon clinical, imaging and pathological findings, were later found to have MNGIE. The cases provide novel clinicopathological insight, for two further reasons: both sisters remain ambulant and in employment in their late 20s and 30s; diagnosis in one sister was made after a suspected azathioprine-precipitated acute illness.

Case presentation

A 25-year-old female presented with diarrhoea, vomiting, abdominal pain, and bloating. Faecal calprotectin, colonic biopsies and magnetic resonance enterography were consistent with a diagnosis of Crohn’s disease. Azathioprine initiation preceded admission with a sore throat, headache, myalgia, and pyrexia. Withdrawal led to rapid clinical improvement. MRI brain revealed persistent, extensive white matter changes. Elevated plasma and urine thymidine and deoxyuridine, and genetic testing for TYMP variants, confirmed MNGIE. Testing of the patient’s sister, also diagnosed with Crohn’s disease, revealed identical variants. In this context, retrospective review of colonic biopsies identified histological findings suggestive of MNGIE.

Conclusions

Azathioprine interference in nucleic acid metabolism may interact with the mitochondrial DNA depletion of MNGIE. Nucleotide supplementation, proposed for treatment by manipulating mitochondrial nucleoside pools, may require caution. The late onset and mild phenotype observed confirms presentation can occur later in life, and may reflect residual thymidine phosphorylase activity. Clinicians should consider measuring plasma thymidine levels in suspected Crohn’s disease to rule out MNGIE, particularly if white matter abnormalities are identified on neuroimaging.

A Concise History of Thiopurines for Inflammatory Bowel Disease: From Anecdotal Reporting to Treat-to-Target Algorithms

BACKGROUND

The need for immune suppressive strategies in the control of chronic inflammatory bowel diseases originated in the 1960s following the perception of a relative inefficacy of salazopyrin and its derivatives. In some 50 years upon an anecdotal claim, the indication for thiopurines in the management of inflammatory bowel diseases has come of age.

OBJECTIVE

The aim of this minireview is to give an overview, after the historical premises, of the current use of thiopurines in the context of inflammatory bowel diseases.

METHOD

Through MEDLINE searches, we reviewed the literature of the last two decades.

RESULTS

For Crohn's disease, the 1980 trial of 6-mercaptopurine for steroid sparing and fistula closure proved pivotal. The analysis of withdrawal experiments and of numerous open trials has established the efficacy of thiopurines for ulcerative colitis. In this indication, cutting-edge data are now showing that because targeting dysplasia, thiopurines can induce mucosal/histological healing, thus abolishing or delaying the need for pre-emptive (tumor prophylactic) colectomy.

CONCLUSION

In UC thiopurines may be recognized to effect a treat-to-target strategy, joining the modern algorithms of rheumatologic disorders.

Photochemical and Photodynamical Properties of Sulfur-Substituted Nucleic Acid Bases

Sulfur-substituted nucleobases (a.k.a., thiobases) are among the world's leading prescriptions for chemotherapy and immunosuppression. Long-term treatment with azathioprine, 6-mercaptopurine and 6-thioguanine has been correlated with the photoinduced formation of carcinomas. Establishing an in-depth understanding of the photochemical properties of these prodrugs may provide a route to overcoming these carcinogenic side effects, or, alternatively, a basis for developing effective compounds for targeted phototherapy. In this review, a broad examination is undertaken, surveying the basic photochemical properties and excited-state dynamics of sulfur-substituted analogs of the canonical DNA and RNA nucleobases. A molecular-level understanding of how sulfur substitution so remarkably perturbs the photochemical properties of the nucleobases is presented by combining experimental results with quantum-chemical calculations. Structure-property relationships demonstrate the impact of site-specific sulfur substitution on the photochemical properties, particularly on the population of the reactive triplet state. The value of fundamental photochemical investigations for driving the development of ultraviolet-A chemotherapeutics is showcased. The most promising photodynamic agents identified thus far have been investigated in various carcinoma cell lines and shown to decrease cell proliferation upon exposure to ultraviolet-A radiation. Overarching principles have been elucidated for the impact that sulfur substitution of the carbonyl oxygen has on the photochemical properties of the nucleobases.

Clinical experience of optimising thiopurine use through metabolite measurement in inflammatory bowel disease

INTRODUCTION

Thiopurine therapy can be optimised by determining the concentration of the drug's metabolites.

PATIENTS AND METHODS

Retrospective analysis on a prospective database of 31 patients with inflammatory bowel disease who failed therapy with thiopurines. Thiopurine metabolites (6-thioguanine, 6-TGN and 6-methylmercaptopurine, 6-MMP) were measured by high-performance liquid chromatography (Laboratorios Cerba, Barcelona) and treatment was duly adjusted in accordance with the results. Clinical response was reassessed after six months.

RESULT

Despite the appropriate theoretical dose of thiopurines being administered, the dose was insufficient in 45.6% of patients (nonadherence to treatment suspected in 6.45%) and 16.2% received an excessive dose or the drug was metabolised by other metabolic pathways. After treatment was optimised based on metabolite levels, only 25.8% (8/31) were prescribed a biological agent, while 74.2% of cases (23/31) were managed through dose optimisation alone.

DISCUSSION

Monitoring thiopurine metabolite levels may help clinicians to assess non-responsive patients before adding or switching to another drug (generally a biological agent), thereby avoiding any additional costs or potential toxicity. This strategy may also help to identify patients receiving an insufficient dose and those with an alternative metabolic pathway, who could be candidates for low-dose AZA with allopurinol, as well as patients who are suspected of being non-adherent. In three out of four patients, switching to a biological agent can be avoided.

Evaluation of Stability of Thiopurine Metabolites Using a Validated LC-MS/MS Method

Measurement of thiopurine metabolites is helpful to monitor adverse effects and assess compliance in patients on thiopurine treatment. The purpose of this study was to develop and validate an analytical method for measurement of thiopurine metabolites, thioguanine nucleotides (6-TGN) and 6-methylmercaptopurine nucleotide (6-MMPN), in RBCs. We developed and validated a liquid chromatography–tandem mass spectrometry (LC-MS/MS) method for the quantification of 6-TGN and 6-MMPN and evaluated the stability of the thiopurine metabolites in RBC and whole blood states without any preprocessing at various storage conditions. The linear range was 0.1–10 µmol/L and 0.5–100 µmol/L for 6-TGN and 6-MMPN, respectively. The mean extraction recovery at the two concentrations was 71.0% and 75.0% for 6-TGN, and 102.2% and 96.4% for 6-MMPN. Thiopurine metabolites in preprocessed RBC samples were stable at 25℃ and 4℃ after storage for 4 hours and at −70℃ for up to 6 months. However, 6-TGN decreased by 30% compared with the initial concentration when stored at −20℃ for 180 days. In whole blood states, 6-TGN decreased by about 20% at four days after storage at 4℃. We validated a reliable LC-MS/MS method and recommend that the patient's whole blood sample be preprocessed as soon as possible.

pH- and GSH-Sensitive Hyaluronic Acid-MP Conjugate Micelles for Intracellular Delivery of Doxorubicin to Colon Cancer Cells and Cancer Stem Cells

A dual-sensitive polymeric drug conjugate (HA-SS-MP) was synthesized by conjugating hydrophobic 6-mercaptopurine (MP) to thiolated hyaluronic acid (HA) as the carrier and ligand to deliver doxorubicin (Dox) to parental colon cancer and colon cancer stem cells. Because of the amphiphilic nature of HA-SS-MP, it was self-assembled in the aqueous media, and Dox was physically encapsulated in the core of the micelles. The particle size and the zeta potential of the micelle were analyzed by dynamic light scattering (DLS), and the morphology of the micelle was investigated using transmission electron microscopy (TEM). Drug release study results revealed more drug release at pH 5.0 in the presence of GSH than that at the physiological pH value. The cytotoxicity of free Dox was slightly greater than that of Dox-loaded HA-SS-MP micelles. In vitro cytotoxicity of HA-SS-MP and Dox-loaded HA-SS-MP micelles was greater for cancer stem cells (HCT116-CSCs) than for parental HCT116 colon cancer cells and L929 normal fibroblast cells. The MTT and flow cytometry results confirmed that free HA competitively inhibited Dox-loaded HA-SS-MP uptake. Similarly, flow cytometry results revealed anti-CD44 antibody competitively inhibited cellular uptake of Rhodamine B isothiocyanate conjugated micelles, which confirms that the synthesized micelle is uptaken via CD44 receptor. Cell cycle analysis revealed that free drugs and Dox-loaded HA-SS-MP arrested parental HCT116 colon cancer cells at the S phase, while cell arrest was observed at the G0G1 phase in HCT116-CSCs. In addition, ex vivo biodistribution study showed that Dox-loaded HA-SS-MP micelles were accumulated more in the tumor region than in any other organ. Furthermore, the in vivo results revealed that Dox-loaded HA-SS-MP micelles exhibited more therapeutic efficacy than the free drugs in inhibiting tumor growth in BALB/C nude mice. Overall, the results suggested that the synthesized micelles could be promising as a stimuli carrier and ligand for delivering Dox to colon cancer cells and also to eradicate colon cancer stem cells.

Unveiling "Musica Universalis" of the Cell: A Brief History of Biological 12-Hour Rhythms

"Musica universalis" is an ancient philosophical concept claiming the movements of celestial bodies follow mathematical equations and resonate to produce an inaudible harmony of music, and the harmonious sounds that humans make were an approximation of this larger harmony of the universe. Besides music, electromagnetic waves such as light and electric signals also are presented as harmonic resonances. Despite the seemingly universal theme of harmonic resonance in various disciplines, it was not until recently that the same harmonic resonance was discovered also to exist in biological systems. Contrary to traditional belief that a biological system is either at stead-state or cycles with a single frequency, it is now appreciated that most biological systems have no homeostatic "set point," but rather oscillate as composite rhythms consisting of superimposed oscillations. These oscillations often cycle at different harmonics of the circadian rhythm, and among these, the ~12-hour oscillation is most prevalent. In this review, we focus on these 12-hour oscillations, with special attention to their evolutionary origin, regulation, and functions in mammals, as well as their relationship to the circadian rhythm. We further discuss the potential roles of the 12-hour clock in regulating hepatic steatosis, aging, and the possibility of 12-hour clock-based chronotherapy. Finally, we posit that biological rhythms are also musica universalis: whereas the circadian rhythm is synchronized to the 24-hour light/dark cycle coinciding with the Earth's rotation, the mammalian 12-hour clock may have evolved from the circatidal clock, which is entrained by the 12-hour tidal cues orchestrated by the moon.