Preclinical Pharmacokinetic Study Of AKBA

AKBA is a pentacyclic triterpenoid compounds, extracted from Boswelliaserrata, used for the treatment of inflammatory diseases. This paper focuses on thepreclinical pharmacokinetics of AKBA, including pharmacokinetics in rats and dogsafter p.o. and i.v. administration determined by LC-MS/MS analysis; distribution andexcretion characteristics of AKBA in rats after p.o. administration; metaboliteidentification of AKBA in rats using QTRAP LC-MS/MS analysis; evaluation ofinhibition of AKBA on recombinant human CYP450enzymes using high-throughputscreening kits; investigation of transmembrane transport mechanism of AKBA byCaco-2and MDCK-MDR1cell model.A rapid, sensitive and specific LC-MS/MS method was developed and validatedfor determination of AKBA in biological matrixes. The method showed goodselectivity and sensitivity, and was successfully applied to characterize the preclinicalpharmacokinetics of AKBA both in vivo and in vitro. After p.o. administration at doseof7.5,15,30mg/kg in rats, CL and t1/2showed no significant difference, andAUC(0-t)was proportional to dose, exihibiting first-order kinetics; when dose wasincreased to60mg/kg, elimination of AKBA was accelerated, CL and Vdwassignificantly increased, showing the characteristics of nonlinear pharmacokinetics;bioavailability of AKBA in rats was21.4%; AKBA belongs to second class of drugsin BCS, therefore, the dissolution rate is the limiting factor for absorption; comparedto single oral dose of AKBA in rats, AUC and Cmaxafter multi-dose showed nosignificant difference, indicating no drug accumulation after multi-dosing. After p.o.administration at dose of7.5,15,30mg/kg in dogs, CL and t1/2showed no significantdifference, and AUC(0-t)was proportional to dose, exihibiting first-order kinetics;bioavailability of AKBA in dogs was44.6%, which was higher than rats; compared tomulti-dose in dogs on day1, AUC and Cmaxof multi-dose on day6showed nosignificant difference, indicating no drug accumulation after multi-dosing.After p.o. administration in rats, AKBA was widely distributed in tissues, andtmaxof tissue concentration was reached at3h. Concentration of AKBA in liver,stomach, intestine, kidney, and brain was higher than other tissues.Concentration ofAKBA in all tissues was decreased remarkably at12h postdosing, implying thatAKBA was not accumulated in tissues. After p.o. administration in rats, AKBA wasnot detected in urine; the accumulative excretion percentage of AKBA in bile was only0.0193%of dosage. AKBA was mainly excreted through the intestinal tract, withthe acccumulative fecal excretion percentage of81.0%. The major metabolicpathways of AKBA were deacetylation to KBA, hydroxylation of AKBA and KBA,dehydrogenation of KBA, hydroxylation and desaturation of KBA. All these phase Imetabolites was detected in the form of glucuronide conjugates in bile. Twometabolites (dehydrogenation of KBA, hydroxylation and desaturation of KBA) werenot detected in feces, probably due to the lack of sensitivity. No metabolites werefound in urine. AKBA might have inhibition on CYA3A4, and did not exhibitinhibition of the other four major recombinant human CYP450enzymes, CYP1A2,2C9,2C19, and2D6. AKBA was not a P-gp substrate, and passive diffusion wasinvolved in its transmembrane transport mechanism. In addition, uptake transportermediated absorption of AKBA may exist in the intestinal epithelial cells.