Research On The Nano-pharmacokinetics Of PEGlyatea Paclitaxel

Paclitaxel(PTX)is a kind of broad spectrum antitumor drug,it is the first chemicals from natural plants approved by the FDA.But the poor water solubility and bad absorption limite its clinical application.Polyethleneglycol(PEG)has good biocompatibility,it is one of the fewest polymer for injection approved by the FDA.PEG has the minimum immunogenicity and the strongest ability to cover immune system among much water-soluble polymer.So it plays a decisive role in the history of the polymer drug.At present multiple PEGylated drugs and PEGylated drug delivery systems have been commercialized or entering in the clinical trial.PEGylated drugs must have obvious changes in vivo pharmacokinetics process.So it is urgent for us to explore a series of problems about pharmacokinetics closely related to the pharmacology and toxicology caused by PEGylated drugs and PEGylated drug delivery system.When evaluating the pharmacokinetics of nanoparticles(NP),the concentration of released free drug should be considered as the basic element.With the comprehensive understanding of the absorbtion,distribution,metabolism and excretion of released free drug in vivo,the pharmacokinetic resultsof NP could provide a more powerful gist for the clinical research of NP.The nano-bonding typed drug-PEGylated paclitaxel(PEG-PTX)was selected as the model drugto evaluate its pharmacokinetic properties in rats.Results of this study verified the feasibility of nano-pharmacokinetics on theory,as well as provided abundant data for the nano-pharmacokinetics of PEG-PTX and a new insight for the evaluation of NP.(1)Quantitative methods of PEG-PTXThere were two difficulties of quantifying PEG-PTX: one was PEGylated drugs having polydisperse MWs,complicated patent ions distribution and tending to produce multiply charged ions.So it was limited to the multiple reaction monitoring(MRM)scanning mode which could only quantitatively analyze the limited and definite molecular weight compounds.Another one was that drug must be changing in vivo pharmacokinetics process as soon as it was PEGylated,such as prolonging the circulation time,reducing intake of the reticuloendothelial system(RES),decreasing the drug release rate and so on.PEGylated small molecule drugs were equivalent to “prodrug”,after the dose of PEG-PTX,it may exist in three forms: PEG,PEG-PTX and PTX.MSAll scan of quadrupole time-of-flight(Q-TOF)MS brought us the solution of quantifying PEG-PTX.All precursor ions in Q1 are transmitted to Q2 and subjected to dissociation through in-quadrupole CID.The fragments are synchronously transmitted into TOF mass analyzer,which ensures it can achieve high resolution,excellent quality accuracy and superior sensitivity under the condition of total quantitation and fully efficient fragmentation of all analytes.We realized the simultaneous determination of PEG,PEG-PTX and PTX in rat biological matrix with liquid chromatography-quadrupole time of flight-tandem mass spectrometry(LC-Q-TOF-MS/MS)and validated in rat blood,tissue,urine and faeces.The results showed that it had good reproducibility,high extraction recovery and low matrix effect.Biological samples were stable in the entire analysis cycle.(2)Pharmacokinetics study of PEG-PTX in rat plasmaA sample prepatation method for the separation of released paclitaxel(R-PTX)in rat plasma was developed.A new liquid chromatography-quadrupole time of flight-tandem mass spectrometry(LC-Q-TOF-MS/MS)method for the simultaneous quantitation of PEG,PEG-PTX and PTX has been also developed and validated.The results showed that the half-life of PEG-PTX was three times higher than that of the common parpatarion;the half-life of R-PTX was two times higher than that of the common parpatarion.PEG-PTX exhibites a prolonged half-life compared to the parent free drug and a long-term effectibe antitumor effect.The area under the concentration-time curve(AUC)of R-PTX was the half of the common parpatarion,which illustrated that PEG-PTX might reduce the side effects caused by PTX itself.The plasma clearance was 18.79 m L/kg and 12.83 m L/kg of the common parpatarion and PEG-PTX,repectively,which revealed that PEG-PTX might decreas the clearance of PTX in body,and prolong the action time.Finally,results showed that PEG-PTX exhibits a prolonged half-life,decreases the concentration of free drug in rat plasma and reduces the side effects of PTX.(3)Tissue distribution study of PEG-PTX in ratWe developed a new sample preparation method for the separation of R-PTX in rat tissues and the method for simultaneous quantitation of PEG,PEG-PTX and PTX.Compared to the common preparation,PEG-PTX reduced the concentration of R-PTX in spleen which illustrated that PEG-PTX might not be recognized and cleared easily by reticuloendothelial system or the immune system.The concentration of free drug from PEG-PTX in stomach,small intestine and muscle was lower than those of commom preparation,indicating that PEG-PTX could reduce the side effect such as gastrointestinal reaction and the pain of joint and muscel.(4)Metabolism study of PEG-PTX in ratThe metabolism study of PEG-PTX in rats was performed by LC-Q-TOF-MS/MS method.The results showed that PEG-PTX and PTX undergo extensive metabolism in vivo.Some metabolites were identified in urine and faeces: PEG-PTX,PTX and PTX-carboxylic derivative;PTX was oxidized to 6α-hydroxypaclitaxel and 3’-p-hydroxypaclitaxel.(5)Excretive study of PEG-PTX in ratWe developed a LC-Q-TOF-MS/MS method for the simultaneous determination of PEG,PEG-PTX and PTX in rat urine and faeces.After a single intravenous injection of common preparation,7.18% of the drug has been excreted through urine and 10.61% of the drug has been excreted through faeces within 120 h.After a single intravenous injection of PEG-PTX,2.47% of R-PTX has been excreted through urine and 4.94% of R-PTX excreted through faeces within 120 h.The results indicated that the process of glomerular filtration function out of the body is blocked after PEGylation of PTX and the filtration rate of PEG-PTX became slow,which might be one of the primary reasons the prolong the half-life of PEG-PTX.