Pharmacokinetic Perspective Research Articles

Developing Computer Algorithms for Optimization of Drug Delivery: A Pharmacokinetic Perspective

Developing Computer Algorithms for Optimization of Drug Delivery: A Pharmacokinetic Perspective

Clinical Pharmacokinetic Characteristics of Cebranopadol, a Novel First-in-Class Analgesic.

Background and ObjectivesCebranopadol is a novel first-in-class analgesic acting as a nociceptin/orphanin FQ peptide and opioid peptide receptor agonist with central analgesic activity. It is currently in clinical development for the treatment of chronic pain conditions. This trial focuses on the clinical pharmacokinetic (PK) properties of cebranopadol after oral single- and multiple-dose administration.MethodsThe basic PK properties of cebranopadol were assessed by means of noncompartmental methods in six phase I clinical trials in healthy subjects and patients. A population PK analysis included two further phase I and six phase II clinical trials.ResultsAfter oral administration of the immediate-release (IR) formulation, cebranopadol is characterized by a late time to reach maximum plasma concentration [C max] (4–6 h), a long half-value duration [HVD] (14–15 h), and a terminal phase half-life in the range of 62–96 h. After multiple once-daily dosing in patients, an operational half-life (the dosing interval resulting in an accumulation factor [AF] of 2) of 24 h was found to be the relevant factor to describe the multiple-dose PKs of cebranopadol. The time to reach steady state was approximately 2 weeks, the AF was approximately 2, and peak-trough fluctuation (PTF) was low (70–80%). Dose proportionality at steady state was shown for a broad dose range of cebranopadol 200–1600 µg. A two-compartment disposition model with two lagged transition compartments and a first-order elimination process best describes cebranopadol data in healthy subjects and patients after single- and multiple-dose administration.ConclusionsCebranopadol formulated as an IR product can be used as a once-daily formulation; it reaches C max after only 4–6 h, and has a long HVD and a low PTF. Therefore, from a PK perspective, cebranopadol is an attractive treatment option for patients with chronic pain.

A Physiologically Based Pharmacokinetic Perspective on the Clinical Utility of Albumin-Based Dose Adjustments in Critically Ill Patients.

In hypo-albuminemia, the extent of albumin binding of a drug decreases. The resulting change in plasma protein binding only rarely leads to clinically relevant changes in unbound drug exposure. Nevertheless, in the critically ill, a tendency to increase dosing of anti-infective therapy is seen in patients experiencing hypo-albuminemia. To reconcile basic pharmacological principles with current clinical practice, this work presents a pharmacologically-based pharmacokinetic simulation study to emphasize the (lack of) effect of altered plasma protein binding on a drug's concentration-time profile and associated pharmacokinetic parameters. Four virtual compounds, representing a broad chemical space (low/high clearance/volume of distribution), were created and administered to a virtual population of normal patients and three types of hypo-albuminemic patients in Simcyp®. The influence of decreased plasma protein binding in hypoalbuminemia on the pharmacokinetic parameters and profiles of these four compounds was investigated. Simulation results showed that while high-clearance compounds suffer from increased unbound exposure with decreased plasma protein binding, the unbound exposure of low-clearance compounds was unaffected. However, for the subset of low-clearance compounds with a small volume of distribution, it appeared that there were still alterations in their plasma concentration-time profiles. Since this may lead to different times above a minimum inhibitory concentration value, this might affect the bacterial killing for some anti-infective drugs. Overall, for any compound involved in the simulations, the unbound exposure did not decrease in plasma protein binding subjects relative to normal plasma protein binding subjects. This finding is in line with the few case-controlled studies in the literature. Hence, increasing the dose/dosing frequency seems futile and might reduce the benefit-risk ratio for narrow therapeutic index drugs. Moreover, these simulations indicate that when only total plasma concentrations and derived pharmacokinetic parameters are considered, incorrect conclusions will be drawn.

Pharmacokinetics of Bispecific Antibody

This article provides a brief overview of bispecific antibody (BsAb) mechanisms of action, structures, and pharmacokinetic (PK) properties, including absorption, distribution, and elimination. Recent trend in BsAb development is also introduced from a PK perspective. Advances in biotechnology have led to the development of diverse BsAb formats, which provide a wide range of options to tailor the design of BsAbs to match the proposed mechanisms of action and to optimize the intended therapies. Understanding the PK properties of BsAbs and the important factors influencing PK is critical for the rationale design and development of BsAb therapeutics. PK behavior of a BsAb is dependent on its format and could be governed by molecular weight, physicochemical properties, interaction with Fc receptors, and binding to target, etc. Due to their multi-binding properties, BsAbs may have superior target tissue deliveries (e.g., brain, solid tumors) and additional unique PK properties compared to conventional mAbs, which may offer therapeutic advantages. Despite the many unknowns about BsAb disposition, it is generally believed that an ideal BsAb should have a balance between favorable systemic exposure (typically a long half-life is preferred) and appropriate distribution and tissue penetration. BsAb has unique mechanisms of action, structures, and PK properties when compared to conventional monoclonal antibody (mAb) and also shares similar pathways that contribute to PK characteristics of conventional mAb. Understanding the PK of BsAbs and the important factors influencing the PK is critical for the rationale design and development of BsAb therapeutics.

The Effects of Sweet Foods on the Pharmacokinetics of Glycyrrhizic Acid by icELISA.

The effect of sweet foods, such as honey, was investigated from the perspective of pharmacokinetics on the absorption of glycyrrhizic acid (GA). Due to the unique properties of indirect competitive enzyme-linked immunosorbent assay (icELISA), namely, its: specificity, sensitivity, repeatability, simple pretreatment of samples, fast and simple operation, and because it is economic and non-polluting, it has received increased attention. In this study, we used the advantages of this method to see how honey affected the pharmacokinetics of GA. The effects of honey on the pharmacokinetics of GA by ELISA were investigated for the first time. The results indicate that honey can postpone the peak concentration of GA in mouse blood, and this effect correlates well with fructose. As a representative of sweet foods, the result provides the valuable information that honey, or fructose, may act as sustained-releasing drugs in clinical scenarios; and that sweet foods may have some influences on drugs when taken together.

Rational application of fructose-1,6-diphosphate: From the perspective of pharmacokinetics.

Fructose-1,6-diphosphate (FDP), a glycolytic metabolite, has been reported to protect susceptible organs during hypoxia or ischemia. However, there is paucity of human data on its pharmacokinetics after being exogenously administered. In the current study, the preliminary pharmacokinetics of FDP given orally to humans was investigated, and no typical peak was observed in the serum drug-time curve. Then, the pharmacokinetic studies were performed following multiple doses of FDP in rats, and the Caco-2 monolayer model was used to study the absorption of FDP in vitro. The results suggested that plasma FDP concentration was significantly increased after oral multiple doses of 180 mg kg(-1) but not 90 mg kg(-1) of FDP, and FDP was partly depleted during the absorption, which was supposed to be consumed by the intestinal epithelium cells. Thus, we conclude that a high dose of FDP should be orally administered in order to get an effective plasma level.

Determination of naturally occurring resveratrol analog trans-4,4'-dihydroxystilbene in rat plasma by liquid chromatography-tandem mass spectrometry: application to a pharmacokinetic study.

trans-4,4'-Dihydroxystilbene (DHS) is a naturally occurring resveratrol analog that displayed promising anti-cancer activities in pre-clinical studies. To further probe its therapeutic potential, a sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the measurement of DHS in rat plasma using electrospray ionization and multiple reaction monitoring in its negative ion mode. This analytical method demonstrated excellent linearity (R(2) > 0.99), selectivity, sensitivity (with a lower limit of quantification of 2.0 ng/mL), accuracy (both intra- and inter-day analytical recovery within 100 ± 15%) and precision (both intra- and inter-day relative standard deviation within 10%). The pharmacokinetic profiles of DHS were subsequently assessed in Sprague-Dawley rats. Following intravenous injection (4 mg/kg), DHS had a moderate apparent volume of distribution of the central compartment (V(c) = 887 ± 297 mL/kg), clearance (Cl = 44.7 ± 5.1 mL/min/kg) and a relatively short mean transit time (MTT = 24.1 ± 8.8 min). When it was given as an oral suspension (10 mg/kg), DHS was absorbed slowly (t max 180 or 300 min) with very limited plasma exposure and absolute oral bioavailability (F = 2.22 ± 0.72%). On the other hand, when DHS was fully solubilized by hydroxypropyl-β-cyclodextrin, it was absorbed rapidly (t(max) 30 or 45 min) with more than 15-fold increase in maximal plasma concentration (C(max)), plasma exposure (AUC(0→last)) and bioavailability (F = 36.3 ± 4.8%). Statistical comparison provided clear evidence that DHS was better than resveratrol from the perspective of pharmacokinetics. In conclusion, further explorations of DHS as an anti-cancer agent are warranted.

Pharmacokinetics/pharmacodinamic (PK/PD) evaluation of a short course of oral administration of metronidazole for the management of infections caused by Bacteroides fragilis

Metronidazole is the antibiotic of choice for the management of infections caused by anaerobes. Its administration requires multiple daily doses causing increased medication errors. Due to its high post-antibiotic effect and rapid concentration-dependent bactericidal activity, administration of this antibiotic in an extended dosing interval would achieve PK/PD parameters effectively. To assess the probability of achieving effective PK/PD relationship with the administration of 1,000 mg every 24 hours of metronidazole for Bacteroides fragilis infections. A clinical trial was conducted in a group of volunteers who received a single oral dose of 500 or 1,000 mg of metronidazole. Determinations of values of Cmax, t max, and AUCC0-24 h. determined using the trapezoidal method, were obtained for a Markov simulation that would allow for determining the likelihood of achieving a AUC0-24 h/MIC ratio above 70 for infections caused by susceptible B. fragilis. Cmax (24,03 ± 6,89 mg/L) and t max (1,20 ± 0.80 hrs) and the value of AUC0-24 h (241.91 ± 48.14 mg * h/L) were determined. The probability of obtaining a AUC0-24 h/MIC ratio greater than 70 was greater than 99%. From a pharmacokinetic perspective, with the administration of a daily dose of 1,000 mg of metronidazole, it is possible to achieve a therapeutic goal of AUC0-24 h/MIC ratio above 70 for the treatment of anaerobic infections.

Are capecitabine and the active metabolite 5-Fu CNS penetrable to treat breast cancer brain metastasis?

Brain metastasis (BM) is increasingly diagnosed in Her2 positive breast cancer (BC) patients. Lack of effective treatment to breast cancer brain metastases (BCBMs) is probably due to inability of the current therapeutic agents to cross the blood-brain barrier. The central nervous system (CNS) response rate in BCBM patients was reported to improve from 2.6%-6% (lapatinib) to 20%-65% (lapatinib in combination with capecitabine). Lapatinib is a poor brain penetrant. In this study, we evaluated the CNS penetration of capecitabine and hoped to interpret the mechanism of the improved CNS response from the pharmacokinetic (PK) perspective. Capecitabine does not have antiproliferative activity and 5-fluorouracil (5-FU) is the active metabolite. Capecitabine was orally administered to mouse returning an unbound brain-to-blood ratio (Kp,uu,brain) at 0.13 and cerebrospinal fluid (CSF)-to-unbound blood ratio (Kp,uu,CSF) at 0.29 for 5-FU. Neither free brain nor CSF concentration of 5-FU can achieve antiproliferative concentration for 50% of maximal inhibition of cell proliferation of 4.57 µM. BCBM mice were treated with capecitabine monotherapy or in combination with lapatinib. The Kp,uu,brain value of 5-FU increased to 0.17 in the brain tumor in the presence of lapatinib, which is still far below unity. The calculated free concentration of 5-FU and lapatinib in the brain tumor did not reach the antiproliferative potency and neither treatment showed antitumor activity in the BCBM mice. The CNS penetration of 5-FU in human was predicted based on the penetration in preclinical brain tumor, CSF, and human PK and the predicted free CNS concentration was below the antiproliferative potency. These results suggest that CNS penetration of 5-FU and lapatinib are not desirable and development of a true CNS penetrable therapeutic agent will further improve the response rate for BCBM.

Pterostilbene surpassed resveratrol for anti-inflammatory application: Potency consideration and pharmacokinetics perspective

This study aimed to evaluate the suitability of pterostilbene for anti-inflammatory application. The in vitro anti-inflammatory activities of pterostilbene were assessed using resveratrol, piceatannol and resveratrol trimethyl ether as comparators while its pharmacokinetics was examined in rats. All tested compounds displayed concentration-dependent anti-proliferative effect in E11 human rheumatoid arthritic synovial fibroblasts. They also suppressed LPS-induced NF-κB p65 nuclear translocation, down-regulated the secretions of IL-6, IL-18, VEGF, nitric oxide, MMP-2 and MMP-9 in E11 cells and attenuated E11-driven migration of THP-1 and U937 monocytes. Similarly, they inhibited LPS-induced pro-inflammatory cytokines in THP-1 cells. Interestingly, pterostilbene usually displayed in vitro anti-inflammatory potencies stronger than resveratrol. In vivo studies revealed that pterostilbene was extensively distributed to major drug target organs like liver, kidney, heart, lung as well as brain and repeated oral dosing did not significantly alter its pharmacokinetics. In conclusion, pterostilbene appears to be a promising candidate for further development.

Improving Brain Drug Targeting Through Exploitation of The Nose-to- Brain Route: A Physiological and Pharmacokinetic Perspective

With an ageing population and increasing prevalence of central-nervous system (CNS) disorders new approaches are required to sustain the development and successful delivery of therapeutics into the brain and CNS. CNS drug delivery is challenging due to the impermeable nature of the brain microvascular endothelial cells that form the blood-brain barrier (BBB) and which prevent the entry of a wide range of therapeutics into the brain. This review examines the role intranasal delivery may play in achieving direct brain delivery, for small molecular weight drugs, macromolecular therapeutics and cell-based therapeutics, by exploitation of the olfactory and trigeminal nerve pathways. This approach is thought to deliver drugs into the brain and CNS through bypassing the BBB. Details of the mechanism of transfer of administrated therapeutics, the pathways that lead to brain deposition, with a specific focus on therapeutic pharmacokinetics, and examples of successful CNS delivery will be explored.

The development and validation of an LC-MS/MS method for the determination of a new anti-malarial compound (TK900D) in human whole blood and its application to pharmacokinetic studies in mice.

BackgroundMalaria is one of the most lethal and life-threatening killer infectious diseases in the world, and account for the deaths of more than half a million people annually. Despite the remarkable achievement made in preventing and eradicating malaria, it still remains a threat to the public health and a burden to the global economy due to the emergence of multiple-drug resistant malaria parasites. Therefore, the need to develop new anti-malarial drugs is crucial. The chemistry department at the University of Cape Town synthesized a number of new CQ-like derivatives (TK-series), and evaluated them for in vitro activity against both CQ-sensitive and -resistant Plasmodium falciparum strains, and for general cytotoxicity against a Chinese Hamster Ovarian (CHO) mammalian cell line. The lead compounds from the TK-series were selected for a comprehensive pharmacokinetic (PK) evaluation in a mouse model.MethodsA sensitive LC-MS/MS assay was developed for the quantitative determination of TK900D. Multiple reaction monitoring (MRM) in the positive ionization mode was used for detection. The analyte and the internal standard (TK900E) were isolated from blood samples by liquid-liquid extraction with ethyl acetate. Chromatographic separation was achieved with a Phenomenex® Kinetex C18 (100 × 2.0 mm id, 2.6 μm) analytical column, using a mixture of 0.1% formic acid and acetonitrile (50:50; v/v) as the mobile phase. The method was fully validated over concentrations that ranged from 3.910 to 1000 ng/ml, and used to evaluate the PK properties of the lead compounds in a mouse model.ResultsThe assay was robust, with deviation not exceeding 11% for the intra- and inter-run precision and accuracy. Extraction recovery was consistent and more than 60%. PK evaluation showed that TK900D and TK900E have moderate oral bioavailability of 30.8% and 25.9%, respectively. The apparent half-life ranged between 4 to 6 h for TK900D and 3.6 to 4 h for TK900E.ConclusionThe assay was sensitive and able to measure accurately low drug levels from a small sample volume (20 μl). PK evaluation showed that the oral bioavailability was moderate. Therefore, from a PK perspective, the compounds look promising and can be taken further in the drug development process.

An Overview of the Pharmacokinetics of Polymer-Based Nanoassemblies and Nanoparticles

Advancements in the design and synthesis of polymer-based nanoassemblies and nanoparticles, combined with achievements in nanotechnology and medicine, have resulted in remarkable applications of polymer nanosystems in the areas of nanomedicine and pharmaceutical sciences. However, a complete understanding of the absorption, distribution, metabolism, and elimination (ADME) processes of such polymer nanosystems in living systems has not been achieved. The influences of the pharmacokinetic parameters of polymer nanomaterials on the ADME processes are reviewed in this article, with discussions of the absorption and transportation of polymer nanoparticles across biological barriers, the factors affecting the bodily distribution of polymer nanocarriers, the transformation of polymer nanomaterials in vivo, the elimination pathway of polymer nanoparticles from biological systems, and perspectives of future pharmacokinetics and safety investigations of polymer-based nanoassemblies. A full and better understanding of the pharmacokinetic parameters of polymer-based nanomaterials is of vital importance in developing polymer nanosystems with optimal pharmacokinetics and biological safety for applications in nanomedicine and the pharmaceutical industry.

Short cationic antimicrobial peptides bind to human alpha-1 acid glycoprotein with no implications for thein vitrobioactivity

Several drugs interact with the major plasma proteins serum albumin and alpha-1 acid glycoprotein. Such binding may be either beneficial or disadvantageous from a pharmacokinetic perspective. In the present paper, we investigate the thermodynamics involved in the binding of a series of promising cationic antimicrobial peptides to the alpha-1 acid glycoprotein using isothermal titration calorimetry. The drug-like peptides are able to effectively destroy multiresistant bacterial strains, and members of this peptide class are currently in clinical phase II trials. Similar peptides, in a previous study, have been shown to bind to serum albumin resulting in a 10-fold reduction in the peptides ability to kill bacteria in vitro. Here, it is shown that the peptides also are ligands for alpha-1 glycoprotein with moderate binding affinities. The binding mode is investigated in detail using molecular docking, which maps the interaction to sub-pockets I, II and III of the binding site. Despite this interaction, protein binding is shown to have little or no effect on the ability of the peptides to kill bacteria in vitro, either at normal physiological or acute phase concentrations. The results show that although the peptides interact with the binding pocket of alpha-1 acid glycoprotein, the low stoichiometric binding ratio ensures that the interaction is not an obstacle for further development of these promising peptides as antimicrobial therapies.

Pharmacokinetic Interactions of Valsartan and Hydrochlorothiazide: An Open-Label, Randomized, 4-Period Crossover Study in Healthy Egyptian Male Volunteers

BackgroundCo-administration of valsartan (VAL) and hydrochlorothiazide (HCT) has been used to regulate blood pressure. Compliance with a multiple medication regimen can be difficult for some patients; therefore, a combination of VAL + HCT tablets may be a suitable alternative. ObjectiveThis study was conducted to compare the rate and extent of absorption of VAL and HCT after oral administration as a fixed-dose combination (FDC) tablet and concomitant administration of the individual drugs under fasting conditions in healthy Egyptian subjects. The study was extended to investigate any potential interaction between VAL and HCT. MethodsThis study was conducted as an open-label, randomized study with 2 parts (parts I and II), with each part consisting of 4 single-dose treatment periods with a crossover design and 2-week washout periods. Blood samples were collected up to 48 hours postdose, and plasma was analyzed for VAL and HCT concentrations by using HPLC. The pharmacokinetic properties of each drug after co-administration of VAL and HCT were compared with those of each drug administered alone. Tolerability was assessed by physical examination and verbally questioning subjects regarding their well-being and any feelings of discomfort. All events reported by the subjects were recorded in adverse-event forms. ResultsForty-eight healthy subjects were enrolled (24 in each part), and all subjects completed the study. None of the participants showed any sign of adverse drug reactions during or after the completion of the study. Statistical analysis confirmed that the 90% CIs for AUC and Cmax of VAL/HCT FDC and VAL + HCT were within the commonly accepted bioequivalence range of 0.8 to 1.25. As a result, from an in vivo pharmacokinetic perspective, 1 FDC tablet could be considered interchangeable in medical practice with the 2 individual reference tablets. However, the 90% CIs between VAL alone and when administered with HCT, either as FDC or concomitantly, indicated the presence of an interaction between VAL and HCT, which would significantly decrease the systemic exposure and intensity of VAL absorption. The co-administration of HCT with VAL decreased the AUC and Cmax of HCT nonsignificantly compared with administration of HCT alone. ConclusionsBoth VAL/HCT FDC and VAL + HCT were well tolerated. The safety/efficacy profile of VAL + HCT co-administration therapy could be extended to the VAL/HCT FDC tablet. The interaction of HCT with other angiotensin-receptor blockers should be investigated to determine whether this interaction is limited to VAL or if other angiotensin-receptor blockers have the same pharmacokinetic interactions. Further studies are necessary to determine the role of efflux and influx transporters on VAL and HCT disposition and pharmacokinetics.

Form and Function in Cyclic Peptide Natural Products: A Pharmacokinetic Perspective

The structural complexity of many natural products sets them apart from common synthetic drugs, allowing them to access a biological target space that lies beyond the enzyme active sites and receptors targeted by conventional small molecule drugs. Naturally occurring cyclic peptides, in particular, exhibit a wide variety of unusual and potent biological activities. Many of these compounds penetrate cells by passive diffusion and some, like the clinically important drug cyclosporine A, are orally bioavailable. These natural products tend to have molecular weights and polar group counts that put them outside the norm based on classic predictors of "drug-likeness". Because of their size and complexity, cyclic peptides occupy a chemical "middle space" in drug discovery that may provide useful scaffolds for modulating more challenging biological targets such as protein-protein interactions and allosteric binding sites. However, the relationship between structure and pharmacokinetic (PK) behavior, especially cell permeability and metabolic clearance, in cyclic peptides has not been studied systematically, and the generality of cyclic peptides as orally bioavailable scaffolds remains an open question. This review focuses on cyclic peptide natural products from a "structure-PK" perspective, outlining what we know and don't know about their properties in the hope of uncovering trends that might be useful in the design of novel "rule-breaking" molecules.

Form and Function in Cyclic Peptide Natural Products: A Pharmacokinetic Perspective

Form and Function in Cyclic Peptide Natural Products: A Pharmacokinetic Perspective

Investigation of the Safety of Topical Metronidazole from a Pharmacokinetic Perspective

Metronidazole (MTZ) ointment has been used widely as a hospital preparation against cancerous malodor. Although cancerous tissue with ulcer-like symptoms is likely to have a higher capacity to absorb drugs than normal skin, the extent to which MTZ is absorbed when a topical preparation is applied to cancerous tissue remains unclear. Furthermore, few studies have investigated the drug interactions involving MTZ despite its long use in clinical practice. In the present study, plasma concentration of MTZ was measured in a breast cancer patient using MTZ ointment for cancerous malodor and basic research was also conducted with the objective of investigating the safety of topical MTZ from a pharmacokinetic perspective. 4.75 µg/mL (27.8 µM) of MTZ was detected in the patient's plasma, which was close to the plasma concentration after oral dosage of MTZ. In a metabolic inhibition study using human liver microsomes, cytochrome P450 (CYP) 2C9-mediated hydroxylation of S-warfarin was almost unaffected by MTZ at the corresponding concentrations. In addition, 3-d repeated oral administration of MTZ (200 mg/kg/d) to rats did not show any significant effects on the hepatic mRNA levels of various CYP isozymes and CYP2C protein levels. These results suggest that the reported interaction of oral MTZ and S-warfarin was not due to CYP2C9 inhibition and that drug interactions via inhibition of CYP2C9 is unlikely to occur when MTZ ointment is applied to ulcerous skin. This information should be valuable for assessing the safety of MTZ ointment used for mitigating cancerous malodor.

Hypomania Associated With Adjunctive Aripiprazole in an Elder Female With Recurrent Major Depressive Disorder

Hypomania Associated With Adjunctive Aripiprazole in an Elder Female With Recurrent Major Depressive Disorder

Potential Factors Influencing Regional Differences and Similarities in Multiregional Clinical Trials

In a multiregional clinical trial (MRCT), determining whether regional differences occur by chance or whether they are due to differences in pharmacokinetics, pharmacodynamics, or other prognostic factors is important to accurately evaluate the true efficacy of a drug in patients of each region. The general probability that regional results will differ from total results has been studied using statistical simulation. Consideration from the pharmacokinetic perspective is necessary as well to investigate the causes of regional differences. Patient characteristics may vary among regions, and differences in medical environment such as commonly used drugs and treatment guidelines can affect regional efficacy and safety results. Moreover, bias may be introduced in the data collected due to differences such as in diagnosis, assessment criteria, and reporting conditions. In this research, the factors and mechanism potentially influencing results by region in MRCT are examined, referring to the results of MRCTs already published.