The use of low dose methotrexate in rheumatoid arthritis - are we entering a new era of therapeutic drug monitoring and pharmacogenomics?

Bioavailability, anti-inflammatory and anti-arthritic effect of Acetyl Keto Boswellic acid and its combination with methotrexate in an arthritic animal model

ETHNOPHARMACOLOGICAL RELEVANCE

Rheumatoid arthritis is one of the most common disabling chronic progressive autoimmune diseases affecting the adult world population. Boswellia serrata has been a known anti-inflammatory agent since ancient times. Therefore, research on Boswellia extract based on Acetyl Keto Boswellic Acid (AKBA) content evaluating its efficacy and safety is necessary. The study aimed to find a suitable Boswellia extract rich in AKBA to evaluate its bioavailability, anti-inflammatory, and anti-arthritic effect. In addition, the synergistic action of AKBA extract with methotrexate (MTX) was also assessed on an animal model.

MATERIALS AND METHODS

Oral bioavailability of AKBA and the anti-inflammatory activity of 10% AKBA (5, 10, 20, 40 mg/kg b.w) was assessed and compared with 2% AKBA (40 mg/kg) and diclofenac (10 mg/kg). The effect of 10% AKBA at 20 mg/kg and 40 mg/kg was evaluated in the FCA induced arthritis animal model alone and combined with methotrexate (MTX) at 2 mg/kg b.w. Subplantar injection of FCA produced edema within a few hours with progressive arthritis by the 9th day after injection. All the treatments were initiated from the 10th day until the 45th day. Oral administration of 10% AKBA was done daily and MTX by intraperitoneal route once a week from day 10 to day 45. Paw volume, erythrocyte sedimentation rate (ESR), serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), alkaline phosphatase (ALP), total bilirubin, oxidative markers (superoxide dismutase (SOD) levels, malondialdehyde (MDA), total proteins and liver histopathology were examined.

RESULTS

10% AKBA provided 8.48-fold, 24.22-fold, 47.36-fold, and 110.53-fold higher AUC (0-α) of AKBA at 5 mg/kg, 10 mg/kg, 20 mg/kg and 40 mg/kg, respectively compared to 2% AKBA at 40 mg/kg. Percentage paw edema inhibition of 10% AKBA at 20 mg/kg and 40 mg/kg were significantly higher than 2% regular AKBA (40 mg/kg) and diclofenac (10 mg/kg). 10% AKBA at a dose of 20 and 40 mg/kg significantly reduced ESR compared with FCA treated group. A combination of methotrexate with 10% AKBA showed the highest reduction in ESR. 10% AKBA at both dose levels significantly reduced hepatic marker enzymes and total bilirubin levels. Treatment with 10% AKBA showed a significant increase in total proteins, antioxidant enzymes and a decrease in malondialdehyde levels. Similarly, 10% AKBA protected the hepatocytes compared with the FCA and FCA + MTX treated group. 10% AKBA was capable of significantly minimizing FCA and FCA + MTX induced changes.

CONCLUSION

Anti-inflammatory activity of AKBA due to inhibition of lipoxygenase (LOX) enzymes supports the use of AKBA in inflammatory disorders. Combination therapy of 10% AKBA with MTX is effective in inhibiting arthritis and circumventing hepatotoxicity produced by MTX in arthritic animals.

Glycolysis aggravates methotrexate toxicity by fueling RFC1-controlled intestinal absorption in rheumatic rats

Methotrexate (MTX) is a first line anti-rheumatic drug. This study was designed to investigate the impact of rheumatoid arthritis (RA) conditions on its oral absorption, and clarify the relevance with changes of MTX absorption-related transporters in rheumatic models. MTX was orally administered to healthy, collagen-induced arthritis (CIA), and adjuvant-induced arthritis (AIA) rats. MTX plasma concentrations were determined by a validated liquid chromatography-mass spectrometry method. We found that intestinal MTX absorption was significantly increased in CIA/AIA rats versus healthy controls. This finding was supported by small intestine-based MTX uptake assay in vitro. Meanwhile, intestinal expression of both reduced folate carrier 1 (RCF1) and proton-coupled folate transporter (PCFT) remained unchanged. The everted intestinal sac assay confirms RFC1 is the key transporter accounting for intestinal MTX absorption, as its antagonist salicylazosulfapyridine showed potent capacity in reducing MTX uptake. No correlation between RA-related cytokines and RCF1 expression was observed in clinical samples. We further revealed that when cultured with AIA rat or RA patient serum, lactate and adenosine triphosphate (ATP) production as well as MTX uptake in MDCKII cells were significantly increased, and this increase was completely abrogated by ATP production-related metabolic inhibitors. Thanks to its inhibitory effects on MTX bioavailability, the glycolysis inhibitor shikonin diminished MTX-induced injuries of kidney and liver in AIA rats. These data demonstrate that glycolysis-driven high energy metabolism increases MTX absorption in rheumatic subjects, leading to the exacerbated toxicity. These findings will have important implications in optimizing MTX regimens for RA treatment with better efficacy and lower toxicity.

Factors influencing methotrexate and methotrexate polyglutamate in patients with rheumatoid arthritis: a systematic review of population pharmacokinetics

Low dose methotrexate (MTX) is commonly used in the treatment of rheumatoid arthritis. The clinical effect is mediated by its metabolite, methotrexate polyglutamate (MTX-PGn). The drug exhibits high interindividual pharmacokinetic variability and the optimal MTX dose is different among individuals. Thus, several MTX population pharmacokinetic (PopPK) models were developed to characterize factors affecting MTX pharmacokinetic variability. This review summarizes significant predictors for MTX pharmacokinetics and identifies knowledge gaps to be further examined. A total of 359 articles were identified from a systematic search of four databases: PubMed, Science Direct, and CINAHL Complete. Of these eight studies were included. Most studies investigated influential factors on MTX pharmacokinetics, but information on MTX-PGn is limited, with only one study performing a parent-metabolite (MTX-PG3) model. MTX pharmacokinetics was described using a two-compartment model with first-order elimination in most studies, with the MTX clearance ranging from 6.94 to 12.39 L/h. Significant predictors influencing MTX clearance included weight, creatinine clearance, sex, OATP1B3 polymorphism, and MTX multiple dosing. While body mass index and red blood cell counts were significant predictors for MTX-PG3 clearance. Providing that MTX-PGn plays a crucial role in clinical effect, further studies should determine other factors affecting MTX-PGn as well as its relationship with clinical response.

Effect of total glucosides of paeony and Tripterygium wilfordii polyglycosides on erythrocyte methotrexate polyglutamates in rats, analysed using ultra-high-performance liquid chromatography-tandem mass spectrometry

OBJECTIVES

The aim of the study was to explore the effect of total glucosides of paeony (TGP) and Tripterygium wilfordii polyglycosides (TWP) on erythrocyte methotrexate polyglutamates (MTXPGs), the metabolites of methotrexate (MTX).

METHODS

An ultra-high-performance liquid chromatography (UPLC)-tandem mass spectrometry (MS/MS) method was developed to determine MTXPGs. The effects of MTXPGs were analysed using 24 male Sprague-Dawley rats that were randomly divided into the MTX alone, MTX-TGP combined, and MTX-TWP combined groups. Rats were administered MTX at a dose of 0.9 mg/kg once a week, TGP at 0.054 g/kg and TWP at 1.8 mg/kg three times a day. Venous blood (1.0 ml) was collected at weeks 2, 4, 6, 9, 12 and 15 and then analysed using the developed UPLC-MS/MS method.

KEY FINDINGS

Specificity, linear range, inter-and intra-day precision, recovery, matrix effect and stability of MTXPGs met the standard regulations. This method was successfully used for the detection of MTXPGs. After administration of MTX alone, erythrocyte MTXPGs increased and accumulated in a time- and dose-dependent manner. Compared to MTX alone, the combination with TGP significantly decreased the content of total MTXPGs and short-chain MTXPGs (Methotrexate [MTX/MTXPG1] and 4-amino-10-methylpteroyldiglutamic acid [MTXPG2], P < 0.05), but had no significant effect on long-chain MTXPGs (4-amino-10-methylpteroyltriglutamic acid [MTXPG3], P > 0.05) and very long-chain MTXPGs (4-amino-10-methylpteroyltetraglutamic acid [MTXPG4] and 4-amino-10-methylpteroylpentaglutamic acid [MTXPG5], P > 0.05) at week 15. The combination of MTX with TWP had no significant effect on the content of total MTXPGs, short-chain MTXPGs and long-chain MTXPGs (P > 0.05), but it significantly decreased the content of very long-chain MTXPGs (P < 0.05) at week 15.

CONCLUSIONS

The UPLC-MS/MS method was successfully used to determine MTXPGs in rat erythrocytes. TGP and TWP in combination with MTX affected the production of MTXPGs of different chain lengths in erythrocytes.

The effects of drug transporters on the efficacy of methotrexate in the treatment of rheumatoid arthritis

The ATP-binding cassette (ABC) and solute carrier (SLC) transporter families consist of common drug transporters that mediate the efflux and uptake of drugs, respectively, and play an important role in the absorption, distribution, metabolism and excretion of drugs in vivo. Rheumatoid arthritis (RA) is an autoimmune disease characterized by erosive arthritis, and there are many RA patients worldwide. Methotrexate (MTX), the first-choice treatment for RA, can reduce the level of inflammation, prevent joint erosion and functional damage, and greatly reduce pain in RA patients. However, many patients show resistance to MTX, greatly affecting the efficacy of MTX. Many factors, such as irrational drug use and heredity, are associated with drug resistance. Considering the effect of drug transporters on drugs, many studies have compared the expression of drug transporters in drug-resistant and drug-sensitive patients, and abnormal transporter expression and transport activity have been found in patients with MTX resistance. Thus, drug transporters are involved in drug resistance. This article reviews the effects of transporters on the efficacy of MTX in the treatment of RA.

A Review of Clinical Applications and Side Effects of Methotrexate in Ophthalmology

Methotrexate (MTX) is a folate analog widely used against a range of diseases including malignancies and autoimmune disorders. Its high effectiveness-price ratio also won extensive application in ophthalmology. On the other hand, although MTX has an excellent pharmacological efficacy, MTX associated side effects in clinical use, which vary from patient to patient, are nonnegligible. There is no comparatively systematic review on MTX associated side effects and its risk factors. This review aimed to reveal novel clinical approaches of MTX and its adverse effects in order to provide a reference for ophthalmic scholars in clinical application of MTX.

Curcumin ameliorates the targeted delivery of methotrexate intercalated montmorillonite clay to cancer cells

Montmorillonite Clay (MMT) is aimed to develop as an orally administrable drug delivery vehicle with enhanced efficacy. Aiming to enhance the therapeutic index of methotrexate, curcumin is concomitantly used with methotrexate in the present study. Being folate antagonist in nature, methotrexate is internalized into cells by folate receptor (FR); which is over-expressed in certain human cancer cells such as cervical carcinoma cells (HeLa). Firstly, montmorillonite Clay (MMT) is organically modified (OMMT) with cetyl trimethyl ammonium bromide (CTAB) and used to intercalate curcumin and methotrexate separately, designated as OMMT-Cur and OMMT-MTX, respectively. XRD pattern demonstrated successful intercalation of therapeutics and an increase in clay interlayer distance facilitated by CTAB. The dissolution kinetics of methotrexate follows Higuchi model for both Simulated Gastric Fluid (SGF) and Simulated Intestinal Fluid (SIF), while the release kinetics for curcumin fitted into Higuchi model for SGF and Hixson-Crowell model for SIF, respectively. OMMT-MTX are able to discriminate FR-positive HeLa cells from FR-negative breast cancer cells (MCF7); irrespective of alike cellular phenotypes. Further, the pre-treatment of HeLa cells with curcumin improves its sensitivity towards methotrexate causing a greater killing of the Hela cells. Together, the results propose the concomitant use of curcumin and methotrexate for successfully targeting highly invasive FR-positive carcinomas by means of folate receptor using MMTs.

Alpha lipoic acid exerts antioxidant effect via Nrf2/HO-1 pathway activation and suppresses hepatic stellate cells activation induced by methotrexate in rats

Hepatic injury is a major side effect associated with methotrexate (MTX) therapy resulting from inflammatory reactions and oxidative stress induction. Therefore, liver fibrosis incidence is augmented with long-term MTX therapy. Alpha lipoic acid (ALA) is a naturally occurring compound with potent antioxidant activity. This study explored the hepatoprotective mechanisms of ALA against MTX-induced hepatic injury in rats. Hepatic injury was induced in MTX group by 20 mg/kg body weight ip. injection of MTX. ALA group was pretreated with ALA 60 mmol/kg body weight ip. for five days followed by a single dose of MTX in the sixth day. Blood samples and liver tissues were then obtained to assess several biochemical parameters as serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), reduced glutathione (GSH), total antioxidant capacity (TAC) and lipid peroxidation. Nuclear factor E2-related factor 2/heme oxygenase-1 (Nrf2/HO-1) pathway was studied by determining the extent of mRNA Nrf2 expression and the level of HO-1. Hepatic stellate cells (HSCs) activation was evaluated by estimating the expression of α-smooth muscle actin (α-SMA) and hydroxyproline content. Also, tumor necrosis factor alpha (TNF-α), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and caspase-3 were assessed by ELISA in addition to histopathological examination of liver samples. Results showed that ALA pretreatment improved liver function since serum ALT, AST and ALP levels were reduced. Additionally, ALA restored GSH and TAC levels when compared to MTX group and decreased lipid peroxidation. ALA exerted its antioxidant effect via Nrf2/HO-1 pathway as well as it showed anti-inflammatory and antiapoptotic effects by reducing TNF-α, iNOS, COX-2 and caspase-3 levels in liver tissue homogenate. Finally, ALA suppressed HSCs activation by decreasing α-SMA expression and hydroxyproline content in liver. It was concluded that ALA has hepatoprotective effects against MTX-induced hepatic injury mediated by Nrf2/HO-1 pathway as well as anti-inflammatory and antiapoptotic properties.

SNPs affecting the clinical outcomes of regularly used immunosuppressants

Recent studies have suggested that genomic diversity may play a key role in different clinical outcomes, and the importance of SNPs is becoming increasingly clear. In this article, we summarize the bioactivity of SNPs that may affect the sensitivity to or possibility of drug reactions that occur among the signaling pathways of regularly used immunosuppressants, such as glucocorticoids, azathioprine, tacrolimus, mycophenolate mofetil, cyclophosphamide and methotrexate. The development of bioinformatics, including machine learning models, has enabled prediction of the proper immunosuppressant dosage with minimal adverse drug reactions for patients after organ transplantation or for those with autoimmune diseases. This article provides a theoretical basis for the personalized use of immunosuppressants in the future.

Association of 63/91 length polymorphism in the DHFR gene major promoter with toxicity of methotrexate in patients with rheumatoid arthritis

Aim: Our aim was to explore the influence of 9-bp insertion/deletion and variable number of 9 bp elements (63/91) length polymorphism in noncoding interfering RNA and major promoter of DHFR gene on methotrexate (MTX) efficacy and toxicity in patients with rheumatoid arthritis (RA). Patients & methods: Response to the MTX therapy and adverse effects were estimated in 243 RA patients genotyped for the selected polymorphism. Results: The presence of allele 1 of analyzed polymorphism had significant protective effect against MTX toxicity (odds ratio: 0.37 [95% CI: 0.19–0.70]; p = 0.002). Results remained significant in multiple logistic regression analysis with the inclusion of disease and treatment features in the model (p = 0.03). Conclusion: Polymorphism 63/91 in DHFR gene promoter can modulate the onset of MTX-related adverse effects in RA patients.

Autoimmune hepatitis as an adverse effect of long-term methotrexate therapy

Methotrexate (MTX) is one of the most commonly used medicines in the treatment of psoriatic arthritis. The drug can produce steatosis and cirrhosis. Autoimmune hepatitis is a rare and serious adverse effect. We describe the case of a 53-year-old woman who developed autoimmune hepatitis after a long-term use of MTX for psoriatic arthritis. Hepatitis was completely resolved 4 months after stopping this drug. The pathophysiologic mechanisms of a drug-induced autoimmunity are unclear and complex. This report confirms the need to monitor liver enzymes carefully in patients using long-term treatment with MTX for psoriasis or rheumatoid arthritis.

Assessment of the relationship between methotrexate polyglutamates in red blood cells and clinical response in patients commencing methotrexate for rheumatoid arthritis

BACKGROUND AND OBJECTIVES

Therapeutic drug monitoring in patients with rheumatoid arthritis (RA) receiving methotrexate (MTX, MTXGlu1) has not been established. In this study, we aim to explore the relationship between red blood cell (RBC) concentrations of MTX and its polyglutamate metabolites (MTXGlu(n); n = 2, 3, 4, 5) and clinical response in RA patients commencing MTX.

METHODS

The binding activity of MTXGlu(n) to three putative enzymes involved in the MTX mechanism of action—dihydrofolate reductase, thymidylate synthase, and 5-aminoimidazole-4-carboxamide ribonucleotide transformylase—was simulated. RBC MTXGlu(n) concentrations that gave the highest inhibition activity across all three enzymes were linked with the disease activity score DAS28-3v (C-reactive protein [CRP]). A population pharmacokinetic-pharmacodynamic model was developed to describe the relationship between RBC MTX polyglutamate concentrations and clinical response in 12 RA patients commencing MTX.

RESULTS

The highest inhibition activity was with RBC MTXGlu(3-5). These polyglutamates were further evaluated for their relationship with DAS28-3v (CRP). Three of the 12 patients had a high DAS28-3v (CRP) at baseline (mean = 6.1) and showed a delayed response to MTX treatment. The remaining nine patients with a lower DAS28-3v (CRP) baseline (mean = 3.6) showed an immediate response. The developed MTX pharmacokinetic-pharmacodynamic model provided an acceptable description of the observed DAS28-3v (CRP) across all patients.

CONCLUSIONS

The developed model describes a longitudinal relationship between RBC MTXGlu(3-5) concentrations and DAS28-3v (CRP) in patients with RA commencing MTX. Further work is required to determine whether measurement of RBC MTX polyglutamates might be useful for dose individualisation in patients with RA.

Individualization of leflunomide dosing in rheumatoid arthritis patients

Leflunomide is largely considered to be a second-line treatment option for rheumatoid arthritis (RA). Those who fail to respond, tend to progress to treatment with expensive biological agents, which can also be associated with serious toxicities. Optimizing leflunomide treatment to meet the needs of individuals would hence be beneficial in terms of patient outcomes and health care expenditure. In this respect, therapeutic drug monitoring (TDM) may be useful, as plasma concentrations of leflunomide's active metabolite, teriflunomide, correlate with response to treatment, but are highly variable between patients. A number of pharmacogenetic markers have also been identified that influence response and toxicity. Incorporation of these findings into clinical practice could facilitate more efficient use of leflunomide.

Anti-inflammatory therapy in chronic disease: challenges and opportunities

A number of widespread and devastating chronic diseases, including atherosclerosis, type 2 diabetes, and Alzheimer's disease, have a pathophysiologically important inflammatory component. In these diseases, the precise identity of the inflammatory stimulus is often unknown and, if known, is difficult to remove. Thus, there is interest in therapeutically targeting the inflammatory response. Although there has been success with anti-inflammatory therapy in chronic diseases triggered by primary inflammation dysregulation or autoimmunity, there are considerable limitations. In particular, the inflammatory response is critical for survival. As a result, redundancy, compensatory pathways, and necessity narrow the risk:benefit ratio of anti-inflammatory drugs. However, new advances in understanding inflammatory signaling and its links to resolution pathways, together with new drug development, offer promise in this area of translational biomedical research.

Measurement of methotrexate polyglutamates in human erythrocytes by ion-pair UPLC-MS/MS

BACKGROUND

Low-dose methotrexate is used for the treatment of rheumatoid arthritis and juvenile idiopathic arthritis, but its effectiveness greatly varies between individuals. Therapeutic drug monitoring of intracellular methotrexate metabolites, the γ-polyglutamates (MTXGlu(n)), in human erythrocytes has shown promise in providing a basis for individualization of therapy.

RESULTS

This work presents expedient methodology for the analysis of MTXGlu(1-7) in human erythrocytes by ion-pair UPLC with detection by tandem MS (UPLC-ESI-MS/MS). The use of N,N-dimethylheptylamine as an ion-pair agent was found to be favorable over others. Thermal extraction of erythrocyte lysates provides a simple one-step extraction procedure. The entire chromatographic run time is 6 min and the assay was validated within the therapeutic range of these metabolites

CONCLUSION

The developed sample preparation procedure in combination with ion-pair UPLC-ESI-MS/MS analysis allowed for expedient quantitation of MTXGlu(1-7) in human erythrocytes. The rapid analysis time would enable therapeutic drug monitoring of MTXGlu(1-7) in the clinic.

Pharmacogenetics of drug-metabolizing enzymes: the prodrug hypothesis

The hope of individualized drug therapy has been bolstered by the knowledge that drug-metabolizing enzymes can be affected by genetic polymorphisms. The initial flurry of potential examples has been muted somewhat by the failure of most predictions to be translated into clinical practice. Perhaps the only real example with reasonable evidence is that of azathioprine/6-mercaptopurine and thiopurine methyl-transferase. A few other examples such as tamoxifen, clopidogrel, irinotecan and warfarin warrant further discussion. An interesting feature of these drugs is that all except warfarin are prodrugs. We propose the hypothesis that prodrugs are over-represented in drugs that may be affected by genetic polymorphisms. Understanding this may assist our efforts to advance the field.

Evaluation of the concomitant use of methotrexate and curcumin on Freund's complete adjuvant-induced arthritis and hematological indices in rats

Objective:

To evaluate the concomitant administration of methotrexate and curcumin for antiarthiritic activity in rats.

Materials and Methods:

Arthritis was induced in rats following a single subplantar injection of Freund's complete adjuvant (0.1 ml). Rats were divided into six groups of six animals each. Group I and II were control injected with saline and Freund's complete adjuvant (0.1 ml), respectively. Group III arthritic rats were treated with curcumin (100 mg/kg, i.p.) on alternate days. Group IV received methotrexate (MTX) (2 mg/kg, i.p.) once in a week. Group-V and VI were treated with MTX (1 mg/kg, i.p.) once in a week and after 30 min received curcumin (30 mg/kg and 100 mg/kg, thrice a week, i.p.) from 10^th to 45^th days, respectively. Body weight and the paw volume was measured on 9^th, 16^th, 23^rd, 30^th, 37^th, and 45^th days. Determination of complete blood cell counts, hemoglobin concentration, hematocrit, mean corpuscular volume, and mean corpuscular hemoglobin concentration was determined on the 46^th day.

Results:

An improvement in body weight and a significant (P < 0.05) reduction in arthritis was observed with the combination treatment as compared to the positive control. A significant improvement in the hematological profile was also observed in rats treated with curcumin and methotrexate.

Conclusion:

The study showed a significant anti-arthritic action and protection from hematological toxicity with the combination treatment of methotrexate and curcumin.

The Frequency of A1298C and C677T Polymorphisms of the Methylentetrahydrofolate Gene in Turkish Patients with Rheumatoid Arthritis: Relationship with Methotrexate Toxicity

The C677T and A1298C polymorphisms of methylenetatrahydrofolate reductase (MTHFR) gene are reported to have a relationship to methotrexate (MTX) metabolism, with conflicting results. The aim of this study was to determine the frequency of MTHFR C677 T and A1298C gene polymorphisms in a group of Turkish RA patients and evaluate its association with MTX toxicity.

Sixty-four patients with RA and 31 control subjects with a mean age of 48.7 ±12.5 and 46.2 ± 13.4 years, were enrolled to the study. Demographic characteristics were obtained and MTX-related adverse effects were recorded in the patient group. The A1298C and C677T polymorphisms of the MTHFR gene were analyzed and the distribution of genotypes according side effects, were determined.

The frequency of MTHFR C677T and A1298C polymorphisms were similar in the patient and control groups. Folic acid supplementation with a mean dose of 5mg folic acid/week, was present in all patients. Thirty-six of the 64 patients showed adverse effects to MTX treatment, and MTX had been discontinued in 12 (18.8%) patients due to side effects and/or inefficacy. MTHFR C677T and A1298C gene polymorphisms were found to be similar in patients with and without MTX-related adverse events.

In conclusion, A1298C and C677T polymorphisms in the MTHFR gene, were not related with MTX-related toxicity in RA patients receiving folate supplementation. Further studies are needed to illuminate the polymorphisms in other enzymes that might be responsible from the MTX toxicity in patients suffering from RA.

Optimization of conventional therapy in patients with IBD

The majority of patients with IBD use conventional therapy (namely, aminosalicylates, antibiotics, corticosteroids and immunomodulatory agents) for prolonged periods of time, to both induce and maintain remission. Treatment paradigms in IBD have evolved towards a rapid escalation of therapy to achieve stringent goals, including mucosal healing and a reduction in the need for hospital admission and surgery. In this context, the failure to optimize conventional therapy can lead to a potentially effective treatment being abandoned too early, which is undesirable when only a limited number of drugs are effective in the management of IBD, and could also lead to patients being unnecessarily exposed to potentially toxic and/or expensive biologic drugs. This Review provides an overview of the many ways in which conventional therapy can be optimized, and describes strategies to improve adherence to drug regimens, such as simplifying the dosing regimen, optimizing drug delivery and dose, and tailoring medication on the basis of metabolite levels.

Significant species difference in amide hydrolysis of GDC-0834, a novel potent and selective Bruton's tyrosine kinase inhibitor

(R)-N-(3-(6-(4-(1,4-dimethyl-3-oxopiperazin-2-yl)phenylamino)-4-methyl-5-oxo-4,5-dihydropyrazin-2-yl)-2-methylphenyl)-4,5,6,7-tetrahydrobenzo[b]thiophene-2-carboxamide (GDC-0834) is a potent and selective inhibitor of Bruton's tyrosine kinase (BTK), investigated as a potential treatment for rheumatoid arthritis. In vitro metabolite identification studies in hepatocytes revealed predominant formation of an inactive metabolite (M1) via amide hydrolysis in human. The formation of M1 appeared to be NADPH-independent in human liver microsomes. M1 was found in only minor to moderate quantities in plasma from preclinical species dosed with GDC-0834. Human clearance predictions using various methodologies resulted in estimates ranging from low to high. In addition, GDC-0834 exhibited low clearance in PXB chimeric mice with humanized liver. Uncertainty in human pharmacokinetic prediction and high interest in a BTK inhibitor for clinical evaluation prompted an investigational new drug strategy, in which GDC-0834 was rapidly advanced to a single-dose human clinical trial. GDC-0834 plasma concentrations in humans were below the limit of quantitation (<1 ng/ml) in most samples from the cohorts dosed orally at 35 and 105 mg. In contrast, substantial plasma concentrations of M1 were observed. In human plasma and urine, only M1 and its sequential metabolites were identified. The formation kinetics of M1 was evaluated in rat, dog, monkey, and human liver microsomes in the absence of NADPH. The maximum rate of M1 formation (V(max)) was substantially higher in human compared with that in other species. In contrast, the Michaelis-Menten constant (K(m)) was comparable among species. Intrinsic clearance (V(max)/K(m)) of GDC-0834 from M1 formation in human was 23- to 169-fold higher than observed in rat, dog, and monkey.

Low dosages: new chemotherapeutic weapons on the battlefield of immune-related disease

Chemotherapeutic drugs eliminate tumor cells at relatively high doses and are considered weapons against tumors in clinics and hospitals. However, despite their ability to induce cellular apoptosis, chemotherapeutic drugs should probably be regarded more as a class of cell regulators than cell killers, if the dosage used and the fact that their targets are involved in basic molecular events are considered. Unfortunately, the regulatory properties of chemotherapeutic drugs are usually hidden or masked by the massive cell death induced by high doses. Recent evidence has begun to suggest that low dosages of chemotherapeutic drugs might profoundly regulate various intracellular aspects of normal cells, especially immune cells. Here, we discuss the immune regulatory roles of three kinds of chemotherapeutic drugs under low-dose conditions and propose low dosages as potential new chemotherapeutic weapons on the battlefield of immune-related disease.

Pharmacogenetics of psoriasis

Psoriasis is an inflammatory hyperproliferative skin disorder with a strong genetic predisposition. While many effective modalities are currently available for treating psoriasis, response to therapy is quite variable among patients. The genetic component underlying the response to pharmacotherapy in psoriasis is slowly beginning to emerge and represents a specialized field of genetics referred to as pharmacogenetics. The identification of genetic variants has the potential to improve the management of patient care by identifying which patients should avoid a specific drug and which patients should be administered a modified dose. A suitable approach in implementing such a strategy could potentially reduce medical costs and improve success of drug therapy. This article summarizes the clinical aspects of psoriasis, its genetic susceptibility and highlights the current landscape of genetic targets for psoriasis pharmacotherapy.

Assessment and management of methotrexate hepatotoxicity in psoriasis patients: report from a consensus conference to evaluate current practice and identify key questions toward optimizing methotrexate use in the clinic

Experts in psoriasis, hepatology, pharmacokinetics and pharmacogenetics convened to discuss the safety and monitoring of methotrexate with respect to hepatotoxicity when used in the treatment of psoriasis. Methotrexate is an efficacious and cost-effective treatment for psoriasis, but is associated with significant safety issues, particularly relating to hepatotoxicity. Current British, Dutch, German, EU and US guidelines for baseline evaluations, monitoring and prevention of hepatotoxicity in patients with psoriasis receiving methotrexate were evaluated. Liver safety monitoring is currently reliant upon multiple methods, including biopsy, serological tests for biomarkers such as type III procollagen amino terminal propeptide (PIIINP), and liver function tests based on liver enzymes. Monitoring of patients receiving long-term therapy is expected to be improved by the utilization of serum biomarkers currently in development such as the Enhanced Liver Fibrosis (ELF) panel and other non-invasive tests of hepatic architecture, such as fibroelastography, microbubbles and magnetic resonance imaging. Appropriate studies to determine optimal dosing to maximize efficacy and minimize toxicity, potentially utilizing pharmacogenetic principles, are clearly needed. Key questions for future research are identified including needs for optimal screening and monitoring, identification of appropriate biomarkers, assessment of relationships between dosing and safety, utility of liver biopsy, optimal dosing regimens (including route of administration), methods to measure methotrexate levels in blood, and use of methotrexate as a standardized active comparator in trials of experimental drugs used to treat psoriasis.

Changes in liver biochemistry during methotrexate use for inflammatory bowel disease

OBJECTIVES

We aimed to characterize the spectrum of liver enzyme test (LET) abnormalities that occur while using methotrexate for inflammatory bowel disease (IBD).

METHODS

A retrospective review was undertaken of subjects using methotrexate for IBD at a single center. The clinical and epidemiological parameters, and hepatotoxicity risk factors, were recorded. Subjects were excluded if cumulative methotrexate doses could not be ascertained, if they had a diagnosis of rheumatoid arthritis or psoriasis, or if baseline and follow-up LETs were not available. Also noted were the cumulative methotrexate dose during the peak LET increase, severity of LET increase, and whether normalization occurred.

RESULTS

Eighty-seven subjects were included (Crohn's disease, n=67; UC, n=17; indeterminate colitis n=3). The mean therapy duration was 81 weeks (3- to 364-week range), and the cumulative average dose was 1,813 mg (25-8,255-mg range). Thirty-seven (43%) subjects received a cumulative dose >1,500 mg. Sixty-seven (77%) had normal LETs, and in 51 (76%) LETs remained normal throughout methotrexate therapy. In the 16 (24%) who developed LET abnormalities, seven (44%) had underlying risk factor(s) for liver disease. Normalization (without dose reduction) occurred in 14 (88%) while continuing methotrexate. Of 20 subjects with abnormal LETs at baseline, nine (45%) subsequently normalized while continuing methotrexate, whereas nine (45%) worsened. Seventeen liver biopsies were performed in 11 and were classified as Roenigk's grade I in 15 (88%) subjects. Roenigk IIIb or IV was not seen.

CONCLUSIONS

Methotrexate is commonly associated with LET abnormalities, but these frequently normalize while still on therapy, and in only 5% will drug discontinuation be necessary. Liver biopsies rarely have substantive abnormalities.

Pharmacogenetics of rheumatoid arthritis: Potential targets from susceptibility genes and present therapies

Rheumatoid arthritis (RA) is a chronic heterogeneous autoimmune disorder of unknown etiology resulting in inflammation in the synovium, cartilage, and bone. Genetic factors play an important role in susceptibility to RA as the heritability of RA is between 50% and 60%, with the human leukocyte antigen (HLA) locus accounting for at least 30% of overall genetic risk. Outside the major histocompatibility complex (MHC) region, six additional risk loci have been identified and validated including PTPN22, STAT4, PADI4, CTLA4, TNFAIP3-OLIG3, and TRAF1/C5. Genetic factors are also important in RA pharmacotherapy due to the gene-dependent activity of enzymes involved in the pharmacokinetics and/or pharmacodynamics of RA medications. Indeed, there is great variability in drug efficacy as well as adverse events associated with any anti-rheumatic therapy and genetics is thought to contribute significantly to this inter-individual variability in response. This review will summarize the genetic factors that have been implicated in the pathogenesis of RA, and how these determinants may factor into the potential pharmacogenetics of this disease. We will also review the therapeutic agents that are currently being utilized or presently being evaluated in the treatment of RA, along with potential pharmacogenetic markers that have been proposed for such medications.

Optimizing conventional therapies for inflammatory bowel disease

Conventional therapies remain the mainstay of treatment for most patients with inflammatory bowel disease (IBD), with only a minority of patients requiring biologic therapies. Recently, attention has focused on optimizing dosing strategies for biologic agents; however, of equal importance are recent advances in the optimization of conventional IBD therapies. Newer aminosalicylate formulations demonstrate similar efficacy with a reduced pill burden and less frequent dosing, while new corticosteroid preparations may retain efficacy with a significantly improved safety profile. The limited indications for antibiotics and probiotics have been further refined by recent data, although uncertainties remain. Advances in the understanding of thiopurine metabolism continue to improve dose optimization and the potential for deliberate therapeutic manipulation with adjunctive therapies. An improved knowledge of intracellular methotrexate metabolism may translate to similar opportunities in the future. This article discusses recent advances relevant to clinical practice today.

A novel high-performance liquid chromatography/mass spectrometry method for improved selective and sensitive measurement of methotrexate polyglutamation status in human red blood cells

The folate antagonist methotrexate is commonly used in low dose for treatment of rheumatoid arthritis and juvenile idiopathic arthritis. Therapeutic effects are attributed to intracellular levels of various methotrexate polyglutamates. The present methodology, combining a simple preparation step with ion-pairing reversed-phase liquid chromatography and electrospray ionization mass spectrometry, is suitable for the measurement of methotrexate and its polyglutamates(2-7), in human red blood cells. Sample preparation consists of perchloric acid protein precipitation followed by solid-phase extraction. Baseline separation of all analytes was achieved within 10 min using a Phenomenex Synergy C18 column together with a gradient solvent program obtained from blending acetonitrile with pH 7.5, 5 mM aqueous dimethylhexylamine. Seven methotrexate polyglutamates were detected using multiple reaction monitoring, with the mass spectrometer operating in positive ion mode. Using 20 microL injection volumes, limits of detection were 2.5 nM for individual methotrexate polyglutamates, while large volume (100 microL) injections led to detection limits of 0.5 nM and linear calibration from 0.5 to 100 nM for individual analytes. Finally, the presented methodology was applied for the analysis of methotrexate and its polyglutamates in red blood cells obtained from patients being treated for juvenile idiopathic arthritis with methotrexate. Significantly, the methodology proved suitable for determination of long-chain methotrexate polyglutamates(5-7) and further, appears to be superior with respect to sensitivity, selectivity and speed as compared to all previously described approaches.

Genetic Polymorphism of C452T (T127I) in Human .GAMMA.-Glutamyl Hydrolase in a Japanese Population

We investigated the genotype distribution and allele frequency of C452T polymorphism of gamma-glutamyl hydrolase (GGH) gene, which causes the decreased enzymatic activity affecting the efficacy of methotrexate (MTX), in a Japanese population. The polymerase chain reaction-restriction fragment length polymorphism assay was applied to determine the genotype of C452T polymorphism in 269 Japanese healthy individuals. The genotype distribution was as follows: C/C, 89.2% (n=240); C/T, 10.4% (n=28); T/T, 0.4% (n=1). The frequency of C and T allele was 0.944 and 0.056, respectively. The obtained genotype distribution was well agreed with those expected by Hardy-Weinberg equilibrium. The genotype distribution and allele frequency in a Japanese population were found to be similar to those of African-Americans but significantly different from Caucasians. Although the frequency of variant T allele in a Japanese population is not so high as compared to Caucasians, determination of C452T polymorphism of GGH may be useful for monitoring of efficacy and side-effects of MTX for treatment of diseases such as rheumatoid arthritis or childhood acute leukemia. To our knowledge, this is the first report about the examination of C452T polymorphism of GGH in a Japanese population.