Prediction of metabolizing enzymemediated clinical drug interactions using in vitro information

Evaluation of drug interactions is an essential step in the new drug development process.Regulatory agencies, including U.S. Food and Drug Administrations and European Medicines Agency, have been published documents containing guidelines to evaluate potential drug interactions. Here, we have streamlined in vitro experiments to assess metabolizing enzymemediated drug interactions and provided an overview of the overall process to evaluate potential clinical drug interactions using v data. An experimental approach is presented when an investigational drug (ID) is either a victim or a perpetrator, respectively, and the general procedure to obtain in vitro drug interaction parameters is also described. With the in vitro inhibitory and/or inductive parameters of the ID, basic, static, and/or dynamic models were used to evaluate potential clinical drug interactions. In addition to basic and static models which assume the most conservative conditions, such as the concentration of perpetrators as C max , dynamic models including physiologically-based pharmacokinetic models take into account changes in in vivo concentrations and metabolizing enzyme levels over time.

Predicting human pharmacokinetics from preclinical data: clearance

We have streamlined known in vitro methods used to predict the clearance (CL) of small molecules in humans in this tutorial. There have been many publications on in vitro methods that are used at different steps of human CL prediction. The steps from initial intrinsic CL measurement in vitro to the final application of the well-stirred model to obtain predicted hepatic CL (CLH ) are somewhat complicated. Except for the experts on drug metabolism and PBPK, many drug development scientists found it hard to figure out the entire picture of human CL prediction. To help readers overcome this barrier, we introduce each method briefly and demonstrate its usage in the chain of related equations destined to the CLH . Despite efforts in the laboratory steps, huge in vitro (predicted CLH )-in vivo (observed CLH ) discrepancy is not rare. A simple remedy to this discrepancy is to correct human predicted CLH using the ratio of in vitro-in vivo CLH obtained from animal species.

Predicting human pharmacokinetics from preclinical data: absorption

Predicting the rate and extent of oral absorption of drugs in humans has been a challenging task for new drug researchers. This tutorial reviews in vivo and PBPK methods reported in the past decades that are widely applied to predicting oral absorption in humans. The physicochemical property and permeability (typically obtained using Caco-2 system) data is the first necessity to predict the extent of absorption from the gut lumen to the intestinal epithelium (Fa). Intrinsic clearance measured using the human microsome or hepatocytes is also needed to predict the gut (Fg) and hepatic (Fh ) bioavailability. However, there are many issues with the correction of the inter-laboratory variability, hepatic cell membrane permeability, CYP3A4 dependency, etc. The bioavailability is finally calculated as F = F h × Fg × Fh . Although the rate of absorption differs by micro-environments and locations in the intestine, it may be simply represented by ka . The ka , the first-order absorption rate constant, is predicted from in vitro and in vivo data. However, human PK-predicting software based on these PBPK theories should be carefully used because there are many assumptions and variances. They include differences in laboratory methods, inter-laboratory variances, and theories behind the methods. Thus, the user's knowledge and experiences in PBPK and in vitro methods are necessary for proper human PK prediction.

Predicting human pharmacokinetics from preclinical data: absorption

Predicting the rate and extent of oral absorption of drugs in humans has been a challenging task for new drug researchers. This tutorial reviews in vivo and PBPK methods reported in the past decades that are widely applied to predicting oral absorption in humans. The physicochemical property and permeability (typically obtained using Caco-2 system) data is the first necessity to predict the extent of absorption from the gut lumen to the intestinal epithelium (Fa). Intrinsic clearance measured using the human microsome or hepatocytes is also needed to predict the gut (Fg) and hepatic (Fh ) bioavailability. However, there are many issues with the correction of the inter-laboratory variability, hepatic cell membrane permeability, CYP3A4 dependency, etc. The bioavailability is finally calculated as F = F h × Fg × Fh . Although the rate of absorption differs by micro-environments and locations in the intestine, it may be simply represented by ka . The ka , the first-order absorption rate constant, is predicted from in vitro and in vivo data. However, human PK-predicting software based on these PBPK theories should be carefully used because there are many assumptions and variances. They include differences in laboratory methods, inter-laboratory variances, and theories behind the methods. Thus, the user's knowledge and experiences in PBPK and in vitro methods are necessary for proper human PK prediction.

Twenty-Nail Dystrophy Treated with Hydroxychloroquine in a Patient with Alopecia Areata

No abstract available.

Physiologically-based pharmacokinetic predictions of intestinal BCRP-mediated drug interactions of rosuvastatin in Koreans

It was recently reported that the C(max) and AUC of rosuvastatin increases when it is coadministered with telmisartan and cyclosporine. Rosuvastatin is known to be a substrate of OATP1B1, OATP1B3, NTCP, and BCRP transporters. The aim of this study was to explore the mechanism of the interactions between rosuvastatin and two perpetrators, telmisartan and cyclosporine. Published (cyclosporine) or newly developed (telmisartan) PBPK models were used to this end. The rosuvastatin model in Simcyp (version 15)'s drug library was modified to reflect racial differences in rosuvastatin exposure. In the telmisartan–rosuvastatin case, simulated rosuvastatin C(maxI)/C(max) and AUC(I)/AUC (with/without telmisartan) ratios were 1.92 and 1.14, respectively, and the T(max) changed from 3.35 h to 1.40 h with coadministration of telmisartan, which were consistent with the aforementioned report (C(maxI)/C(max): 2.01, AUCI/AUC:1.18, T(max): 5 h → 0.75 h). In the next case of cyclosporine–rosuvastatin, the simulated rosuvastatin C(maxI)/C(max) and AUC(I)/AUC (with/without cyclosporine) ratios were 3.29 and 1.30, respectively. The decrease in the CL(int,BCRP,intestine) of rosuvastatin by telmisartan and cyclosporine in the PBPK model was pivotal to reproducing this finding in Simcyp. Our PBPK model demonstrated that the major causes of increase in rosuvastatin exposure are mediated by intestinal BCRP (rosuvastatin–telmisartan interaction) or by both of BCRP and OATP1B1/3 (rosuvastatin–cyclosporine interaction).

Tinea Versicolor Mimicking Pityriasis Rubra Pilaris caused by Malassezia globosa / 대한의진균학회지

Tinea versicolor (TV) is a common fungal skin disease caused by the Malassezia species. This disease usually presents as hypopigmented- or hyperpigmented coalescing scaly macules, papules, patches or plaques on the trunk and upper arms. Herein, we report a rare clinical manifestation of TV in a 29-year-old man presenting with marked follicular, erythematous, and hyperkeratotic papules on the trunk with erythematous scaly macules and patches on the upper extremities with intermittently spared skin. We initially suspected pityriasis rubra pilaris, however, skin biopsy results and mycological examination revealed TV. Polymerase chain reaction-based sequence analysis revealed Malassezia globosa. The patient was successfully treated with oral itraconazole and topical terbinafine.

GAB2 Amplification in Squamous Cell Lung Cancer of Non-Smokers

Lung squamous cell cancer (SCC) is typically found in smokers and has a very low incidence in non-smokers, indicating differences in the tumor biology of lung SCC in smokers and non-smokers. However, the specific mutations that drive tumor growth in non-smokers have not been identified. To identify mutations in lung SCC of non-smokers, we performed a genetic analysis using arrays comparative genomic hybridization (ArrayCGH). We analyzed 19 patients with lung SCC who underwent surgical treatment between April 2005 and April 2015. Clinical characteristics were reviewed, and DNA was extracted from fresh frozen lung cancer specimens. All of copy number alterations from ArrayCGH were validated using The Cancer Genome Atlas (TCGA) copy number variation (CNV) data of lung SCC. We examined the frequency of copy number changes according to the smoking status (non-smoker [n = 8] or smoker [n = 11]). We identified 16 significantly altered regions from ArrayCGH data, three gain and four loss regions overlapped with the TCGA lung squamous cell carcinoma (LUSC) patients. Within these overlapped significant regions, we detected 15 genes that have been reported in the Cancer Gene census. We also found that the proto-oncogene GAB2 (11q14.1) was significantly amplified in non-smokers patients and vice versa in both ArrayCGH and TCGA data. Immunohistochemical analyses showed that GAB2 protein was relatively upregulated in non-smoker than smoker tissues (37.5% vs. 9.0%, P = 0.007). GAB2 amplification may have an important role in the development of lung SCC in non-smokers. GAB2 may represent a potential biomarker for lung SCC in non-smokers.

Population pharmacokinetics and inter-laboratory variability of sildenafil and its metabolite after oral administration in Korean healthy male volunteers

This study was to clarify population pharmacokinetics (PK) of sildenafil and its metabolite, N-desmethyl sildenafil (NDS) in Korean healthy male population using a pooled data from multiple clinical trials in consideration of inter-institution and inter-laboratory difference. A population PK analysis was performed with data of 243 healthy volunteers from five single-center (4 centers) comparative PK trials. The dataset included 7,376 sildenafil and NDS concentration (3,688 for each analyte) observed during 24 hours after the single dose of original sildenafil (either 50 mg or 100 mg of Viagra®). The plasma concentration was assayed in two laboratories. Various model structure was tested and the final model was evaluated using visual predictive checks. Demographic and clinical variables were assessed as potential covariates for PK parameters. A one-compartment first-order elimination model with proportional error was selected for the dispositional characteristics of sildenafil, and two-compartment model was chosen for NDS. Three transit compartments with Erlang-type absorption for fast absorption pathway and one compartment for slow absorption pathway constructed overall absorption model. The first-pass effect was rejected since it does not improve the model. The difference of NDS level by the bioanalysis laboratory was selected as the only covariate. Even though a direct comparison was difficult, the general trend in PK of sildenafil and NDS for Korean healthy male was considered similar to that of the other populations reported previously. It is recommended that the laboratory effect should be explored and evaluated when dataset is built using results from several laboratories.

Periungual Abscess Caused by Citrobacter braakii in a Patient with Chronic Paronychia

No abstract available.

A Case of Secondary Syphilis Presenting as a "Leukoplakia-like" Plaque on the Tongue in a HIV Patient / 대한피부과학회지

"Leukoplakia-like" plaque on the tongue is an uncommon skin manifestation of secondary syphilis. Skin lesions of secondary syphilis usually have numerous presentations, which mimic many other skin diseases, especially in the presence of HIV co-infection. Oral hairy leukoplakia (OHL) is characterized by corrugated whitish patches and plaques on the lateral border of the tongue. It is frequently and strongly associated with HIV but may appear in other diseases. A 47-year-old man with HIV and receiving HAART therapy developed a leukoplakia-like plaque on the tongue, which was first suggestive of OHL but was eventually diagnosed as secondary syphilis.

Establishment and Significance of Bioequivalence Recommendations for Individual Products-Drugs Acting on Circulatory System and Others

Along with the enactment of a law separating the prescribing and dispensing of drugs in Korea in 2000, attempts at reducing medical expenses by generic substitution have been allowed since August 2001 so long as generic products are bioequivalent to the original products. In the pharmaceutical industry, the required development and investment to make generic products are much less in terms of time and money. Thus, the number of bioequivalence studies in Korea has increased. This has resulted in the need for bioequivalence recommendations (guidelines), taking into account the circumstances of the Korean pharmaceutical industry. In this paper, we provide procedures for making bioequivalence determinations for individual products acting on the circulatory system (30 drugs, 2011), the components of which are widely accepted for the development of generic products in Korea. These recommendations correspond with international guidelines, such as those of the US FDA and EMEA. For the 30 drugs that act on the circulatory system, we examined each in terms of subject selection (healthy volunteers vs. patients), dosage strength, dosage route, analytes to measure, and evaluation parameters, and prepared bioequivalence recommendations for individual products through an analysis of many published papers, US FDA and EMEA guidelines, and clinical trial websites. Based on the bioequivalence recommendations for individual products, we had several meetings in which KFDA officers (members of the New Drug Research team and the Office of Generic Drugs), three pharmacy professors with expertise in drug analysis and pharmacokinetics, and three professors of medicine with extensive experience in clinical trials participated to confirm and discuss the contents. Finally, the bioequivalence recommendations for individual products were provided on the KFDA website. The individual bioequivalence recommendations have been used by KFDA officers in drug evaluations and bioequivalency testing to improve consistency, clarity, and professionalism in the drug evaluation process. These recommendations will be useful for domestic pharmaceutical companies by shortening the time and cost associated with bioequivalence studies, especially in terms of standardized trial designs, dosage forms, and analytical methods.