Bioequivalence Study For Topical Glucocorticoids Based On Skin Blanching Response Using Chinese Skin

1 Research background and purposeTopical glucocorticoids are the first-line symptomatic treatment drugs for non-destructive inflammatory skin diseases（such as eczema and psoriasis）,and play an extremely important role in clinical medication.The systemic absorption of these drugs is poor and has no obvious dependence on the curative effect.Therefore,the consistency of the quality and curative effect cannot be assessed by the conventional pharmacokinetics method.The curative effect is closely related to the local concentration and maintenance time of the drug.The United States and the European Union recommend the"skin blanching assay"to evaluate the bioequivalence of such preparations,whose basic principle is that the drugs can constrict the microvessels in the microvasculature of the skin,resulting in visible skin blanching.The degree of blanching is affected by the dose of the drug and directly related to the clinical efficacy.At present,a variety of products have been approved for marketing through the"skin blanching assay".However,the reliability of the method depends on the sensitivity of the skin color to vasoconstriction.Exploring the realization conditions of"skin blanching assay"in east Asian can significantly shorten the clinical evaluation process of such drugs,which has important significance.In this study,the methods of population selection and administration of"skin blanching assay"in Chinese population were established.Then,the dose-effect relationship of strong,moderate and weak glucocorticoids was studied and the the proportion of who met the"detector"criteria was preliminarily evaluated to provide reference for the design of bioequivalence study.Therefore,the bioequivalence evaluation method of"skin blanching assay"for topical glucocorticoids for east Asian was established,and the bioequivalence of two desonide creams was systematically evaluated by this method.2 Methods and results2.1 Establishment of method of"vasoconstriction assay"Taking weak glucocorticoid 0.05%desonide cream as the research object,the subjects selection method of"skin blanching assay"was established.The judgment standard of"responders"（subjects with obvious vasoconstriction to the drug）was determined.The administration method was established,including the ventral forearm was selected as the test site,and the dose adjustment was realized by"staggered application with staggered removal",the administration area was 1 cm²,the administration weight was 3 mg,and the administration area was sealed.It was found that detectable skin blanching occurred when the drug-skin contact time（dose-duration）was 2 h under the above study conditions,and the degree of skin blanching did not increase significantly within the dose duration of 8-16 h.It is suggested that the first dose-duration site of the dose-response study should be set to be less than 2 h,and it is recommended that the termination dose-duration be 8 h,and the maximum duration should not exceed 16 h.2.2 Dose duration-response study of strong,moderate and weak drugsThe potency of drugs affects the onset time and maximum vasoconstriction intensity,which affects the linear interval of dose-response,and finally affects the dose duration ED₅₀.Generally,the ED₅₀should be controlled within the range of 1-2 h,at this time,the variability of the test is low and the operability is strong.In this study,36 subjects were selected and divided into 3 groups on average,namely mometasone furoate cream（strong effect）group,fluticasone propionate cream（moderate effect）group,and desonide cream（weak effect）group.The dosages were 5 mg,10 mg,and 3 mg,respectively,and the weak group was sealed with polyethylene film.According to the above research methods,the ED₅₀ of strong,moderate and weak drugs were 1.07 h,1.33h,and 1.46 h,respectively,all within the range of 1-2 h.Differences in skin penetration can lead to different dose-response linear intervals for individuals.ED₅₀ is the population value.The dose-response relationship of some subjects actually deviated from this range.This part of the population could not be included in the statistics because the degree of skin blanching was unrelated to the dose.Subjects that met the linear relationship were"detector"subjects,and the proportion of"detector"subjects in the population is an important basis for the design of BE study.Through the statistics of the dose-response study,there were 6,5,and 6 subjects in the strong,moderate,and weak groups met the"detector"standard,accounting for 41.7%-50.0%.In order to meet the evaluable number of 40-60 in the BE study,100-120 subjects need to be enrolled.2.3 Bioequivalence study of desonide creamTaking self-developed desonide cream as the test preparation,and desonide cream produced by Perrigo New York Inc as the reference preparation,a single-center,randomized,open-label,two-dose preparation,single-cycle bioequivalence study was carried out.100 subjects participated in the study.The study set up two comparison groups:different formulations and self-control group,the latter used to verify the scientificity of the method.47 subjects met the"detector"criteria,and their data were included in the statistics.Using Locke’s method to calculate the90%confidence interval of the AUEC_0-24 geometric mean ratio of the"detector"subjects,the results of the comparison of the same preparation and different preparations were:95.43%-109.32%and 96.30%-108.01%.It is proved that the developed bioequivalence method based on"vasoconstriction assay"is scientifically feasible,and the two desonide creams are bioequivalent.3 ConclusionThe study proved for the first time that the"skin blanching assay"can be applied to evaluate the bioequivalence of two topical glucocorticoids using Chinese skin.The key design of the trial was successfully explored:the number of subjects was 100-120,the administration area was 1 cm²,the administration dose was 2-10 mg.For strong,moderate and weak glucocorticoids,the ED₅₀ suitable for BE research can be obtained by adjusting the administration weight of drugs.This study provides an important reference for bioequivalence study of topical glucocorticoid by using"skin blanching assay"in China,and is of great significance to accelerate the clinical evaluation process of such drugs.There are 17 figures,21 tables and 55references in this article.