Evaluation of Bioequivalence for Avapritinib Tablets in Chinese Participants Under Fasting Conditions Using a Reference-Scaled Average Bioequivalence Method.

This study aimed to assess the bioequivalence of 2 avapritinib tablets formulations. A randomized, open-label, single-center trial was conducted on fasting, healthy Chinese participants. The study utilized a partial replicated design with 3 sequences and 3 periods. Participants were assigned to 1 of 3 sequences, with each sequence receiving the reference formulation twice and the test formulation once. Plasma samples were collected and analyzed to determine pharmacokinetic parameters. The bioequivalence of the 2 avapritinib formulations was assessed using reference-scaled average bioequivalence for the maximum plasma concentration (Cmax) and the average bioequivalence analysis for the area under the concentration-time curve (AUC). Out of 39 participants, 38 completed the study. For Cmax, the 1-sided 95% upper confidence interval (CI) bound from the scaled approach was -0.035 (<0) and the point estimate value was 0.958, falling inside the acceptance range of 0.8-1.25. For both the AUC over all concentrations measured (AUC0-t) and the AUC from time 0 to infinity (AUC0-inf), the 90% CIs of geometric mean ratios (0.87-1.01) also met the bioequivalence criteria of 0.8-1.25. Consequently, the study demonstrated that the 2 avapritinib formulations were bioequivalent under fasting conditions.

Clinical pharmacokinetics and pharmacodynamics of ivosidenib in Chinese patients with relapsed or refractory IDH1-mutated acute myeloid leukemia.

PURPOSE: This study aimed to assess the pharmacokinetics (PK) and pharmacodynamics (PD) of ivosidenib in Chinese patients with relapsed or refractory acute myeloid leukemia (R/R AML) carrying the mIDH1 mutation. METHODS: A bridging study (NCT04176393) was conducted involving 29 Chinese patients who received a daily dose of ivosidenib 500 mg in 28-day cycles. Plasma concentrations of ivosidenib and D-2-hydroxyglutarate (2-HG) were measured before and after treatment. Non-compartmental analysis (NCA) was employed to evaluate the PK, and an established population pharmacokinetic (popPK) model developed from non-Chinese patients was externally validated. RESULTS: The findings revealed comparable PD effects of ivosidenib in Chinese patients with mIDH1 R/R AML. After adjusting for concomitant drug effects, PK characteristics were similar between Chinese and non-Chinese patients. Furthermore, the popPK model offered additional insights into the possible causes of the apparent ethnic difference in PK exposure. CONCLUSION: The study indicates that ivosidenib can be used effectively in Chinese patients, and the observed ethnic differences in PK exposure can be explained by concomitant drug effects. The popPK model contributes to a better understanding and optimization of personalized dosing in Chinese patients with mIDH1 R/R AML.

Tumor growth inhibition-overall survival modeling in non-small cell lung cancer: A case study from GEMSTONE-302.

Overall survival is vital for approving new anticancer drugs but is often impractical for early-phase studies. The tumor growth inhibition-overall survival (TGI-OS) model could bridge the gap between early- and late-stage development. This study aimed to identify an appropriate TGI-OS model for patients with non-small cell lung cancer from the GEMSTONE-302 study of sugemalimab. We used three TGI models to delineate tumor trajectories and investigated three OS model for linking TGI metric to OS. All three TGI models accurately captured tumor profiles at the individual level. The published atezolizumab-based TGI-OS model predicted survival time satisfactorily through simulation-based evaluation, whereas the other published model built from multi-treatment underestimated OS. Our study-specific TGI-OS model identified time-to-growth as the most significant metric with the number of metastatic sites and neutrophil-to-lymphocyte ratio at baseline as covariates and exhibited robust OS predictability. Our findings demonstrated the effectiveness of the TGI-OS models in predicting phase III outcomes, which underpins their value as a powerful tool for antitumor drug development.

Can a propensity score matching method be applied to assessing efficacy from single-arm proof-of-concept trials in oncology?

As a result of the escalating number of new cancer treatments being developed and competition among pharmaceutical companies, decisions regarding how to proceed with phase III trials are frequently based on findings from either single-arm phase I expansion cohorts or phase II studies that compare the efficacy of the study drug to a standard-of-care benchmark derived from historical data. However, even when eligibility criteria are matched, differences in the distribution of baseline patient features may influence the outcome of single-arm trials in real-world scenarios. Therefore, novel methods are needed to enhance the accuracy of efficacy prediction from current cohorts relative to historical data. In this study, we demonstrated the feasibility of using the propensity score matching (PSM) method to improve decision making by matching relevant baseline features between current and historical cohorts. According to our findings, utilizing the PSM method may provide a less biased means of comparing outcomes between current and historical cohorts relative to a naïve approach, which relies solely on differences in average outcomes between the cohorts.

Comprehensive analysis of CDK5 as a novel biomarker for progression in esophageal cancer.

BACKGROUND: Cyclin-dependent kinase 5 (CDK5) is a member of the cyclin-dependent kinase family, and unlike the rest of the members of the family, its kinase activity is independent of cyclins. Accumulating evidence has shown that CDK5 plays a significant role in the progress of tumorigenesis except in nervous system. In particular, the expression of CDK5 and its function in esophageal cancer (ESCA) remain unknown. METHODS: With TCGA and GEO databases, CDK5 was analyzed with the expression, predicted value, clinical relationship, functional enrichment, immune cell infiltration and immune molecules in ESCA. In addition, we explored the CDK5 expression with local datasets and the influence of CDK5 on proliferation, migration and invasion behaviors of the esophageal squamous cell carcinoma (ESCC) cells in vitro and in vivo experiments. RESULTS: CDK5 expression was upregulated in ESCA, and this regulation has been verified in cell lines of ESCC. Further analysis has found that the expression of CDK5 was correlated with race, weight, BMI, histological type and tumor central location in ESCA. KEGG analysis revealed that CDK5 was involved in the progress of cancers, innate immune system and PI3K-Akt signaling pathway. CDK5 was closely related to immune cells and immune molecules in ESCA. Functional experiments confirmed CDK5 was an oncogene in ESCC by in vivo and in vitro models. CONCLUSIONS: This study shows that CDK5 is a risk factor to promote tumor progression, and Roscovitine could be one of the effective tools in the therapy of ESCA.

Optimising intravenous salbutamol in children: a phase 2 study.

OBJECTIVE: The ß2-agonists such as salbutamol are the mainstay of asthma management. Pharmacokinetic-pharmacodynamic (PKPD) models to guide paediatric dosing are lacking. We explored the relationship between salbutamol dose, serum concentration, effectiveness and adverse effects in children by developing a PKPD model. DESIGN: A prospective cohort study of children admitted to hospital with acute asthma, who received intravenous salbutamol. SETTING: Children were recruited in two cohorts: the emergency departments of two London hospitals or those retrieved by the Children's Acute Transport Service to three London paediatric intensive care units. PATIENTS: Patients were eligible if aged 1-15 years, admitted for acute asthma and about to receive or receiving intravenous salbutamol. INTERVENTIONS: Treatment was according to local policy. Serial salbutamol plasma levels were taken. Effectiveness measurements were recorded using the Paediatric Asthma Severity Score (PASS). Toxicity measurements included lactate, pH, glucose, heart rate, blood pressure and arrhythmias. PKPD modelling was performed with non-linear mixed-effect models. MAIN OUTCOMES: Fifty-eight children were recruited with 221 salbutamol concentration measurements from 54 children. Median (range) age was 2.9 (1.1-15.2) years, and weight was 13.6 (8-57.3) kg. Ninety-five PASS measurements and 2078 toxicity measurements were obtained. RESULTS: A two-compartment PK model adequately described the time course of salbutamol-plasma concentrations. An EMAX (maximum drug effect) concentration-effect relationship described PASS and toxicity measures. PKPD simulations showed an infusion of 0.5 µg/kg/min (maximum 20 µg/min) for 4 hours after bolus achieves >90% maximal bronchodilation for 12 hours. CONCLUSIONS: A paediatric PKPD model for salbutamol is described. An infusion of 0.5 µg/kg/min after bolus achieves effective bronchodilation. Higher rates are associated with greater tachycardia and hyperglycaemia.

Evaluating the Taste Masking Ability of Two Novel Dispersible Tablet Platforms Containing Zinc Sulfate and Paracetamol Reconstituted in a Breast Milk Substitute.

Milk is often used as a dispersion medium for medicines administration in young children but its taste-masking ability is unknown. A human taste panel was conducted to assess the potential of infant formula milk (Aptamil® 1) to mask the taste of two model WHO priority medicines, zinc sulfate and paracetamol, manufactured as dispersible tablets. Simultaneously, the palatability of powder blends of the tablet platforms was assessed. Twenty healthy adult volunteers performed a swirl-and-spit assessment of placebos and API-containing blends in either a lactose-based or a mannitol-based dispersible tablet platform, reconstituted in 10 mL of either water or Aptamil® 1. Eighteen samples were rated for aversion using a 100-mm Visual Analogue Scale, grittiness using a 5-point Likert scale, and "acceptability-as-a-medicine" evaluated as: "Would you find this sample acceptable to swallow as a medicine?" with binary answers of Yes/No. The API-containing formulations were more aversive than the placebos; the paracetamol-containing samples being more aversive than zinc sulfate samples. The platforms themselves were not aversive. Non-gritty samples had four-fold greater odds of being acceptable as a medicine. Aptamil® 1 masked the taste of zinc sulfate in the mannitol-based formulation but did not mask the taste of paracetamol in either platform, suggesting a limited taste-masking ability, which may be API and formulation dependent.

Modelling item scores of Unified Parkinson's Disease Rating Scale Part III for greater trial efficiency.

AIMS: The multipart Unified Parkinson's Disease Rating Scale is the standard instrument in clinical trials. A sum of scores for all items in 1 or more parts of the instrument is usually analysed. Without accounting for relative importance of individual items, this sum of scores conceivably does not optimize the power of the instrument. The aim was to compare the ability to detect drug effect in slowing down motor function deterioration, as measured by Part III of the Scale-motor examinations-between the item scores and the sum of scores. METHODS: We used data from 423 patients in a Parkinson's disease progression trial to estimate the symptom severity by item response modelling; modelled symptom progression using the severity and the sum of scores; and conducted simulations to compare the sensitivity of detecting a broad range of hypothetical drug effects on progression using the severity and the sum of scores. RESULTS: The severity endpoint was far more sensitive than the sum of scores for detecting treatment effects, e.g. requiring 275 vs. 625 patients per arm to achieve 60% probability of trial success for detecting a range of potential effects in a 2-year trial. Nontremor items related to the left side of the body seemed most informative. The domain relevance of tremor items appeared questionable. CONCLUSION: This analysis generated clear evidence that longitudinal modelling of item scores can enhance trial efficiency and success. It also called for reassessing the placement of the tremor items in the instrument.

Misidentification Subtype of Alzheimer's Disease Psychosis Predicts a Faster Cognitive Decline.

The presence of psychosis is associated with a more rapid decline in Alzheimer's disease (AD), but the impact of paranoid (persecutory delusions) and misidentification (misperceptions and/or hallucinations) subtypes of psychosis on the speed of decline in AD is still unclear. We analyzed data on Alzheimer's Disease Neuroimaging Initiative 2 participants with late mild cognitive impairment or AD, and we described individual trajectories of Alzheimer's Disease Assessment Scale-Cognitive Subscale scores using a semimechanistic logistic model with a mixed effects-based approach, which accounted for dropout and adjusted for baseline Mini Mental State Examination scores. The covariate model included psychosis subtypes, age, gender, education, medications, and Apolipoprotein E epsilon 4 (Apo-e ε4 genotype). We found that the Alzheimer's Disease Assessment Scale-Cognitive Subscale rate of increase was doubled in misidentification (ßr,misid_subtype  = 0.63, P = 0.031) and mixed (both subtypes; ßr,mixed_subtype  = 0.70, P = 0.003) when compared with nonpsychotic (or paranoid) patients, suggesting that the misidentification subtype may represent a distinct AD sub-phenotype associated with an accelerated pathological process.

Pharmacokinetics of Single and Repeat Doses of Fluticasone Furoate/Umeclidinium/Vilanterol in Healthy Chinese Adults.

The pharmacokinetics (PK) and safety of single-inhaler fluticasone furoate/umeclidinium/vilanterol (FF/UMEC/VI) after single and repeat dosing in healthy Chinese adults were assessed. In this open-label study (NCT02837380), subjects received once-daily FF/UMEC/VI 100/62.5/25 µg on day 1 and repeat doses on days 2-7. PK parameters (days 1 and 7) included maximum observed concentration (Cmax ) and area under the plasma concentration-time curve (AUC) from time zero (predose) to last time of quantifiable concentration (AUC0-t ). Terminal phase half-life (t½ ) on day 1 was estimated. The primary objective was to assess systemic exposure of FF 100 µg, UMEC 62.5 µg, and VI 25 µg following single-inhaler triple therapy on days 1 and 7. On day 1, geometric mean t½ of UMEC and VI was 0.36 and 0.52 hours, respectively; t½ of FF was not representative because of nonquantifiable concentration data. On days 1 and 7, geometric mean Cmax of FF was 10.46 and 27.32 pg/mL, respectively; Cmax of UMEC was 144.14 and 241.35 pg/mL, respectively; and Cmax of VI was 120.42 and 196.78 pg/mL, respectively. AUC0-t of FF was 1.77 and 276.96 pg·h/mL, respectively; AUC0-t of UMEC was 28.44 and 117.19 pg·h/mL, respectively; and AUC0-t of VI, 42.46 and 101.12 pg·h/mL, respectively. The PK of FF/UMEC/VI was as expected for the individual-component PK previously reported in healthy Chinese adults. No new safety signals were observed.

Rats can predict aversiveness of Active Pharmaceutical Ingredients.

Taste is crucial for patient acceptability and compliance with prescribed medicines, in particular with pediatric patients. Evaluating the taste of new active pharmaceutical ingredients (APIs) is therefore essential to put in place adequate taste-masking techniques, if needed, which will lead to acceptable palatable formulations. Thus, there is an urgent need to develop and optimize taste assessment methods that could be used at different stages of the drug development process. The aim of this study was to investigate the suitability of the rat brief-access taste aversion (BATA) model as a screening tool for assessment of APIs aversiveness that could predict human taste responses. Presently, the taste intensity of nine marketed APIs known to have different levels of bitter intensity (quinine hydrochloride dihydrate, 6-n-propylthiouracil, sildenafil citrate, diclofenac sodium, ranitidine hydrochloride, caffeine citrate, isoniazid, telbivudine and paracetamol) was investigated at different overlapping concentrations with two in vivo taste assessment methods: the rat BATA model and human taste panels with the intention of determining the drugs' concentrations to produce half of the maximal rating. Overall there was a strong correlation (R2 = 0.896) between rats IC50 and humans EC50 values. This correlation verifies the BATA model as a rapid and reliable tool for quantitative assessment of API aversiveness. A comparable ranking order was obtained mainly for high and medium aversive compounds, whereas it was less aligned for weakly aversive compounds. It was nonetheless possible to propose a classification of poor taste intensity determined in rats that would predict human taste tolerability.

Acceptability of orodispersible films for delivery of medicines to infants and preschool children.

Orodispersible films (ODFs) possess potential to facilitate oral drug delivery to children; however, documentation of their acceptability in this age group is lacking. This study is the first to explore the initial perceptions, acceptability and ease of use of ODFs for infants and preschool children, and their caregivers through observed administration of the type of dosage form. Placebo ODFs were administered to children stratified into aged 6 to 12 months, 1 year, 2 years, 3 years, 4 years and 5 years old and into those with an acute illness or long-term stable condition in hospital setting. Acceptability of the dosage form and end-user views were assessed by (a) direct observation of administration, (b) questionnaires to caregivers and nurses, and (c) age-adapted questionnaires for children aged 3 years and over. The majority of children (78%) aged 3 years and over gave the ODF a positive rating both on verbal and non-verbal scales. Despite little prior experience, 78% of caregivers expressed positive opinion about ODFs before administration. After the ODFs were taken, 79% of infant caregivers and 86% caregivers of preschool children positively rated their child's acceptance of the ODF. The intraclass correlation coefficient value was 0.92 showing good agreement between ratings of caregivers and nurses. ODFs showed a high degree of acceptability among young children and their caregivers. If drug loading permits, pharmaceutical companies should consider developing pediatric medicines in this format. The methodology described here is useful in assessing the acceptability of active ODF preparations and other dosage forms to children.

The CLOSED trial; CLOnidine compared with midazolam for SEDation of paediatric patients in the intensive care unit: study protocol for a multicentre randomised controlled trial.

INTRODUCTION: Sedation is an essential part of paediatric critical care. Midazolam, often in combination with opioids, is the current gold standard drug. However, as it is a far-from-ideal agent, clonidine is increasingly being used in children. This drug is prescribed off-label for this indication, as many drugs in paediatrics are. Therefore, the CLOSED trial aims to provide data on the pharmacokinetics, safety and efficacy of clonidine for the sedation of mechanically ventilated patients in order to obtain a paediatric-use marketing authorisation. METHODS AND ANALYSIS: The CLOSED study is a multicentre, double-blind, randomised, active-controlled non-inferiority trial with a 1:1 randomisation between clonidine and midazolam. Both treatment groups are stratified according to age in three groups with the same size: <28 days (n=100), 28 days to <2 years (n=100) and 2-18 years (n=100). The primary end point is defined as the occurrence of sedation failure within the study period. Secondary end points include a pharmacokinetic/pharmacodynamic relationship, pharmacogenetics, occurrence of delirium and withdrawal syndrome, opioid consumption and neurodevelopment in the neonatal age group. Logistic regression will be used for the primary end point, appropriate statistics will be used for the secondary end points. ETHICS: Written informed consent will be obtained from the parents/caregivers. Verbal or deferred consent will be used in the sites where national legislation allows. The study has institutional review board approval at recruiting sites. The results will be published in a peer-reviewed journal and shared with the worldwide medical community. TRIAL REGISTRATION: EudraCT: 2014-003582-24; Clinicaltrials.gov: NCT02509273; pre-results.

Effect of age on the performance of bispectral and entropy indices during sevoflurane pediatric anesthesia: a pharmacometric study.

BACKGROUND: Bispectral index (BIS) and entropy monitors have been proposed for use in children, but research has not supported their validity for infants. However, effective monitoring of young children may be even more important than for adults, to aid appropriate anesthetic dosing and reduce the chance of adverse consequences. This prospective study aimed to investigate the relationships between age and the predictive performance of BIS and entropy monitors in measuring the anesthetic drug effects within a pediatric surgery setting. METHODS: We concurrently recorded BIS and entropy (SE/RE) in 48 children aged 1 month-12 years, undergoing general anesthesia with sevoflurane and fentanyl. Nonlinear mixed effects modeling was used to characterize the concentration-response relationship independently between the three monitor indicators with sevoflurane. The model's goodness-of-fit was assessed by prediction-corrected visual predictive checks. Model fit with age was evaluated using absolute conditional individual weighted residuals (|CIWRES|). The ability of BIS and entropy monitors to describe the effect of anesthesia was compared with prediction probabilities (PK ) in different age groups. Intraoperative and awakening values were compared in the age groups. The correlation between BIS and entropy was also calculated. RESULTS: |CIWRES| vs age showed an increasing trend in the model's accuracy for all three indicators. PK probabilities were similar for all three indicators within each age group, though lower in infants. The linear correlations between BIS and entropy in different age groups were lower for infants. Infants also tended to have lower values during surgery and at awakening than older children, while toddlers had higher values. CONCLUSIONS: Performance of both monitors improves as age increases. Our results suggest a need for the development of new monitor algorithms or calibration to better account for the age-specific EEG dynamics of younger patients.

Development of a model for robust and exploratory analysis of the rodent brief-access taste aversion data.

The rodent brief-access taste aversion (BATA) model is an efficient in vivo screening tool for taste assessment. A new E(max) (maximum effect attributable to the drug) model was developed and further investigated in comparison with three previously published models for analysing the rodent BATA data; the robustness of all the models was discussed. The rodent BATA data were obtained from a series of experiments conducted with a bitter reference compound, quinine hydrochloride dihydrate (QHD). A new E(max) model that could be applied to both "lick numbers" and "lick ratios" was built and three published models that used lick ratios were employed for analysing the BATA data. IC50, the concentration that inhibits 50% of the maximum lick numbers, quantified the oral aversiveness of QHD. One thousand bootstrap datasets were generated from the original data. All models were applied to estimate the confidence intervals of the IC50s without symmetric assumption. The IC50 value obtained from the new E(max) model was 0.0496 mM (95% CI 0.0297-0.0857) using the lick numbers for analysis, while an IC50 of 0.0502 mM (95% CI 0.0267-0.0859) was acquired with the lick ratios. Except one published model, the IC50 values have a similar range for the 95% CI. The new E(max) model enabled the analysis of both "lick numbers" and "lick ratios" whereas other models could only handle data presented as "lick ratios". IC50s obtained with these two types of datasets showed similarity among all models thereby justified the robustness of the new E(max) model.

Random sparse sampling strategy using stochastic simulation and estimation for a population pharmacokinetic study.

The purpose of this study was to use the stochastic simulation and estimation method to evaluate the effects of sample size and the number of samples per individual on the model development and evaluation. The pharmacokinetic parameters and inter- and intra-individual variation were obtained from a population pharmacokinetic model of clinical trials of amlodipine. Stochastic simulation and estimation were performed to evaluate the efficiencies of different sparse sampling scenarios to estimate the compartment model. Simulated data were generated a 1000 times and three candidate models were used to fit the 1000 data sets. Fifty-five kinds of sparse sampling scenarios were investigated and compared. The results showed that, 60 samples with three points and 20 samples with five points are recommended, and the quantitative methodology of stochastic simulation and estimation is valuable for efficiently estimating the compartment model and can be used for other similar model development and evaluation approaches.

Systematic evaluation of non-inferiority and equivalence randomized trials of anti-infective drugs.

The non-inferiority (NI) and equivalence (EQ) design is used widely in the clinical trials of anti-infective drugs, but still many arguments for, and against, conducting active control NI/EQ trials rather than simple placebo controlled trials. We searched Pubmed database and conducted a systematic literature review (1992-2011) to assess the methodological aspects of NI and EQ randomized trials of anti-infective drugs. A total of 335 publications with 337 trials were included. Of them, 235 trials reported a pre-specified margin of 10-15%. A proportion (e.g., cure, successful, failure) was used as the primary outcome in 316 trials (93.8%). Test treatments were non-inferior or equivalent to the control treatment in 325 trials (93.4%). The historical evidence for the effect of the control drug was specified in 38 trials (11.3%). For the literature of NI/EQ trials in anti-infective treatment, aspects that need improvement include the description of study participation, trial implementation, historical evidence and endpoint for the efficacy of control, inclusion of flow diagrams and figures that present margins and confidence intervals according to CONSORT criteria.

A cyclic fluctuation model for 24-h ambulatory blood pressure monitoring in Chinese patients with mild to moderate hypertension.

AIM: The conventional method for analyzing 24-h ambulatory blood pressure monitoring (24-h ABPM) is insufficient to deal with the large amount of data collected. The aim of this study was to develop a novel cyclic fluctuation model for 24-h ABPM in Chinese patients with mild to moderate hypertension. METHODS: The data were obtained from 4 independent antihypertensive drug clinical trials in Chinese patients with mild to moderate hypertension. The measurements of 24-h ABPM at the end of the placebo run-in period in study 1 were used to develop the cyclic fluctuation model. After evaluated, the structural model was used to analyze the measurements in the other 3 studies. Models were fitted using NONMEM software. RESULTS: The cyclic fluctuation model, which consisted of 2 cosine functions with fixed-effect parameters for rhythm-adjusted 24-h mean blood pressure, amplitude and phase shift, successfully described the blood pressure measurements of study 1. Model robustness was validated by the bootstrap method. The measurements in the other 3 studies were well described by the same structural model. Moreover, the parameters from all the 4 studies were very similar. Visual predictive checks demonstrated that the cyclic fluctuation model could predict the blood pressure fluctuations in the 4 studies. CONCLUSION: The cyclic fluctuation model for 24-h ABPM deepens our understanding of blood pressure variability, which will be beneficial for drug development and individual therapy in hypertensive patients.

Systematic evaluation of dose accumulation studies in clinical pharmacokinetics.

The amount of drug remaining after previous doses, or drug accumulation, is closely related to drug efficacy and safety. An accurate calculation of the accumulation index or ratio (R(ac)) is crucial for dose finding. However, in drug accumulation studies little consensus exists with regard to experimental design or data analysis. We conducted a systematic review of the literature to produce a detailed profile of drug accumulation studies of the last 30 years (1980-2011). Ninety-six articles comprising 122 studies were analyzed. A typical drug accumulation study enrolled 10 to 20 subjects randomly assigned into treatment groups of 1 or 2 dose levels to observe pharmacokinetic behaviors. The median washout period between single and multiple dosing was 7 days, and the dose interval was 1-2 elimination half-lives in non- or one-compartmental models. Generally, the number of repeated times of administration for multiple dosing was 7-14, and the median number of sampling time points was 11. Eight different methods were used to calculate R(ac). The most frequently used method, in 72.9% of the studies, was to set R(ac) equal to the ratio of the area under a plasma concentration-time curve (AUC) during a dosage interval at steady state to the AUC of a dosage interval after the first dose, i.e., R(ac) = AUC(0-τ,ss) / AUC(0-τ,1). The values of R(ac) in the included studies ranged from 0.85 to 18.8, and 68.03% were <2. We suggest that sample size estimation for an accumulation study should be similar to that of a bioequivalence study, and in most studies, 18-24 subjects will be needed. Appropriate calculation methods for R(ac) should be selected based on the experimental design and data characteristics. The crucial values for non-, weak, moderate, and strong accumulation can be set at R(ac) < 1.2, 1.2 ≤ R(ac) < 2, 2 ≤ R(ac) < 5, and R(ac) ≥ 5, respectively. Accumulations studies should also give more regard to drug metabolism and increased accumulation in kidney or liver damaged patients.