Study On The Druggability Of PEGylated Mesalazine And Its Preparation

5-ASA is the active ingredients in the treatment of ulcerative colitis;Its role is expressed in two aspects: on the one hand,it reduce the production of prostaglandins which induced inflammation;on the other hand,it inhibit the formation of inflammatory mediators leukotrienes,Thus generate a significant therapeutic effect on inflammation of the intestinal wall.For nearly 30 years,5-ASA has been used as the preferred drug for the treatment of inflammatory bowel disease(IBD).However,when 5-ASA is administrated orally,a large of drug is absorbed and metabolize from the upper gastrointestinal tract,that can not produce the desired effect.What’s worse,these absorbed drug will causes nephrotoxicity.Moreover,5-ASA also has some shortcoming,such as poor water solubility,low bioavailability,short half-life,unreasonable tissue distribution and high toxic side effects.Therefore,it has become the focus of current research to develop a 5-ASA Colon-targeted preparation that are non-toxic and good biocompatibility.PEG is a neutral linear polymer with low cost,non-toxic and good water solubility.Besides improving its water-soluble,bioavailability and half-life,the drugs after modified by polyethylene glycol(PEG)will have a different intestinal absorption.Our laboratory previously take a series of different molecular weight(350-5000 Da)monomethoxypolyethylene glycol(mPEG)as carrier to preparation of5-ASA colon-targeted preparations(That is 5-ASA-mPEG350,5-ASA-mPEG1000,5-ASA-mPEG2000 and 5-ASA-mPEG5000).The purpose of this paper is to study its druggability,including characteristics of intestinal absorption,pharmacological activity,absorption and transportation characteristics in vitro,and processing of its corresponding preparation.The ultimate goal of researching the druggability is to confirmed the pharmacological activity of these prodrug and the inhibitory effect on intestinal absorption,and laying the foundation for further clinical research.In situ single pass intestinal perfusion model was performed to study the intestinal absorption characteristics of this series of derivatives,and investigated the intestinal absorption of 5-ASA derivatives as well as the influence of molecular weight on absorption.At last,the intestinal absorption mechanism and its dynamic characteristics of this derivatives was revealed.The results show that the drugconcentration and the site of intestine segments had little effect on the drug absorption constant(Ka)and apparent absorption coefficient(Papp).The perfusion flow rate and the variable molecular weight of 5-ASA-mPEG could significantly affect the Ka and Papp.The conclusion is 5-ASA-mPEG can be absorbed at all segments of the intestine of rats and has no specific absorption site.It is preliminarily inferred that the absorption mechanism of 5-ASA-mPEG is passive transportation.The intestinal absorption of 5-ASA-mPEG showed a downward trend with the increase in molecular weight.The results showed that the modification of 5-ASA by PEG can effective inhibit the intestinal absorption of mesalazine.Caco-2 cell model is an important means of studying drug absorption in vitro.It has become the most representative method.This research adopts the Caco-2 cell monolayer model to study the absorption and transportation of 5-ASA-mPEG prodrug,prejudging the absorption of the prodrug in the human intestinal tract,nd investigated its intestinal absorption mechanism.The results show that there are some correlation between the transportation in vitro and in vivo intestinal absorption in rats.The effect of molecular weight change on transportation is similar to the rat intestinal absorption in situ.The drug is absorbed mainly in the form of passive transport,the P-glycoprotein(P-gp)efflux mechanism performance is not obvious in the process of absorption.The model of the mice ulcerative colitis(UC)was established by using Dextran sulfate sodium(DSS).These C57BL/6 mice were randomly divided into blank group,model group and experimental group,and were given 5% dextran sulfate sodium(DSS)solution to drink for 6 days,while the blank mice were fed by water.The experimental mice received the treatment daily by intragastric administration corresponding 5-ASA series derivatives,while the other two groups were given the same dose of normal saline.Finally we investigate the pharmacological activities of5-ASA series derivatives by observing the daily activity in mice and the histopathology.The results show that the model group had significant difference between the normal group in disease activity index,colon length,colonic histopathology,colonic tissue MPO value and serum TNF-α level,indicating that the model was copied successfully.This series of compounds of 5-ASA-mPEG can reduce the MPO level and serum TNF-α value in colonic tissue,indicating that it has the effect of inhibiting inflammatory factors and reducing the formation of oxygenfree radicals.Histopathological examination showed that these prodrug compounds have the effect of ulcerative colitis.According to 2015 edition of Chinese Pharmacopoeia,the quality criteria of5-ASA-mPEG1000 tablets was studied on the basis of its physical and chemical property and the feature of tablets.First,using the method of single factor investigation,the types of prescription accessories were preliminarily screened considering synthetically several evaluation quotas.Then,the optimization formulation were selected by orthogonal experiment.Finally,the optimal prescription and preparation technology of 5-ASA-mPEG1000 tablets were determined.The corresponding preparation quality standard(draft)was formulated by investigating the quality standard of the tablet.By investigating the druggability of series prodrug,the effect of molecular weight on drug absorption and its absorption mechanism were elucidated.The inhibitory effect of molecular weight on absorption and the pharmacological activities of the series prodrug was confirmed.We prepared tablets using prodrug with relatively optimal molecular weight,and the corresponding quality standard(draft)was established,which laid the foundation for further clinical study of prodrug.