Pharmacokinetic Research And Evaluation On New Lung-targeting Docetaxel Liposomes

Lung cancer is one of the most common malignancy.Currently the incidence and mortality of lung cancer are showing an astonishing increasing trends in the global and has replaced liver cancer to become the first cause of death in China,in which non-small cell lung cancer(NSCLC)accounts for about 80% of the total incidence of lung cancer.The main drugs currently used in clinical treatment of NSCLC,such as platinum,paclitaxel and docetaxel(DTX),etc.often induced greater toxicity and side effects because of their lack of lung-targeting,which limited their use.Therefore,the ideal treatment strategy is to develop the lung-targeting preparation.A new docetaxel liposome(DTX-LP)which was prepared by our team using a combination of solid dispersion and effervescent technology can deliver DTX mainly to the lung,which can significantly improve the DTX efficacy and reduce systemic toxicity,and basically the key scientific problem of the lung-targeting effect of liposome is solved.Then the pharmacokinetic study of DTX-LP were planned to carry out by our team in order to mainly explore the metabolism of the lung-targeting DTX-LP,when comparing with the docetaxel injection(DTX-IN).ObjectiveThis study used the comparison method and took the DTX-IN as control to inspect the differences of pharmacokinetic parameters,tissue distribution,metabolism and excretion between DTX-LP and DTX-IN,so as to evaluate the influence of its high lung-targeting effect on the pharmacokinetics of DTX,and carry out the biological evaluation about the efficacy and safety of DTX-LP.Method1.UPLC-MS/MS analysis method was established and validated for analysis of DTX in rabbit plasma,urine and feces samples.2.HPLC analysis method was established and validated for analysis of DTX in rabbit plasma and tissues samples.3.UPLC-MS/MS method was used to determine the rabbit plasma concentration of DTX at different time after administration and correlative pharmacokinetic parameters was obtained by using DASver2.0 software.4.HPLC method was used to determine the concentration of DTX in the main tissues and organs of rabbits at different time after administration and study the tissue distribution.5.The DTX-LP were incubated with rabbit liver homogenates,rabbit lung homogenates and rabbit liver Microsomes in vitro respectively and administrated to the rabbit to study the metabolism of DTX loaded in the new type of liposome.6.UPLC-MS/MS method was used to determine the concentration of DTX in rabbit urine and feces collected at different interval after administration and study the excretion amount and excretion rate.Results1.The selectivity of the UPLC-MS/MS method established was good.The relative recoveries were 88.3%~109.4% and the extraction recoveries were more than 81.3%.The precision values(expressed as RSD)of intraand inter-were below 11.3% for these biosamples.The LC-MS/MS method could meet biosamples analysis.2.The selectivity of the HPLC method established was good,samplepreparation method was appropriate,no significant interference peaks were observed in HPLC chromatogram.The relative recoveries were86.2%~118.0% and the extraction recoveries were more than 78.8%.The precision values(expressed as RSD)of intra-and inter-were below 10.9%for these biosamples.The HPLC method could meet biosamples analysis.3.After intravenous administration of DTX-LP and DTX-IN in rabbits,three-compartment model gave the best fit to the plasma drug concentration time curves.AUC(0-t),t1/2? and t1/2? were 1.009mg/L·h?0.024h?1.53 h vs1.963mg/L·h?0.057h?0.465 h respectively.The t1/2? of DTX-LP was about0.42 times that of DTX-IN,significantly shortened,which indicated DTX-LP could distribute quickly from the circulation to the target organ,and the t1/2? was about 3.3 times,significantly prolonged,which was conducive to play DTX anticancer effects in vivo.Meanwhile the clearance of DTX-LP was 1.64 times that of DTX-IN,which showed DTX-LP could be removed from the blood circulation and accumulated in the target organ more easily.4.The high lung-targeting effect of DTX-LP was confirmed.At 0.5h after intravenous administration of DTX-IN in rabbits,the drug concentrations order from high to low was kidney,spleen,liver,heart,lung,stomach and brain,in which the drug concentration in lung was only3.124?g/g.After administration of DTX-LP,the drug concentration in lung reached 58.657?g/g at the same time point,which was significantly higher than other tissues.And DTX-LP made the drug concentration in lung about19 times higher than that of DTX-IN,while significantly reduced its presence in the blood,heart,kidney,stomach,which is conductive to reduce the toxicity of DTX to these parts.In the term of lung-targeting evaluation,the values of TI was 11.77 for the lung of DTX-LP,and Te,TQe of lung tissue are 61.26%,52.83% respectively for DTX-LP,and9.03%,6.19% respectively for DTX-IN.All of above indicates that the DTX-LP has the characteristic of high lung-targeting effect.5.To meet the need of our study,the idea about researching the metabolism of DTX using rabbit lung homogenatesas was proposed.The study showed that both DTX-LP and DTX-IN were not metabolized in rabbit lung homogenatesas basically.And contrary to that,the DTX content in DTX-LP and DTX-IN decreased by 29.1% and 38.0% in liver homogenatesas respectively,in liver microsomes 23.7% and 23.9%,respectively.Two metabolites were found both in DTX-LP and DTX-IN incubated with rabbit liver homogenatesas including one known M-2 and one other metabolite Mun-1(Mol.Wt.821)which was not reported.Nine metabolites were found in vivo including the four known metabolites: M-1,M-2,M-3,M-4,and five new metabolites: Mun-1,Mun-2,Mun-3,Mun-4 and Mun-5 after DTX-LP and DTX-IN were administrated to the rabbits respectively.DTX-LP was not metabolized in lung.6.After administration of DTX-LP,excretion amount in feces and urine were 183.9?g and 7.21?g respectively,excretion rate were 9.2% and0.36% respectively.For DTX-IN,excretion amount in feces and urine were359.0?g and 13.0?g respectively,excretion rate were 17.9% and 0.65%respectively.No matter in feces or in urine,both the excretion amount and rate of DTX-LP were significantly lower than those of DTX-IN.ConclusionThe pharmacokinetics of the new DTX-LP developed in the laboratory was studied,its pharmacokinetic parameters and tissue distribution and excretion in the urine and feces were significantly different from the DTX-IN in rabbits.The new preparation of DTX-LP did not change the metabolism of DTX while changing the distribution of DTX,and the two preparations had the basically consistent metabolic profiles either in vivo orin vitro.Nine metabolites were found in vivo including the four known metabolites: M-1,M-2,M-3,M-4,and five new metabolites: Mun-1,Mun-2,Mun-3,Mun-4 and Mun-5 after DTX-LP and DTX-IN were administrated to the rabbits respectively.DTX-LP was not metabolized in lung.In conclusion,those above greatly improved DTX concentration in the lung,and reduced the drug concentration in other organs such as blood,heart,kidney,etc.,extended the cancellation process of DTX from the body,and could improve therapeutic index,while reducing the systemic toxicity of DTX,which are important for clinical application,and could be more conducive to maintain the activity of DTX and improve its efficacy.