•ABCB1 (P-gp) played a major role in the efflux transport of Huperzine A in Caco-2 and transfected MDCKII cell lines.•Abcb1a was a limiting factor for Huperzine A's brain distribution in Abcb1a−/−, Abcg2−/−, and Abcb1a−/−/Abcg2−/− mice.•Modulation of ABCB1 activity may lead to changes in brain concentrations of Huperzine A, thus altering its safety profiles.Huperzine A has been used for improving symptoms of Alzheimer's disease. Its cholinergic side effect is thought to be an exaggerated pharmacological outcome linked to its high brain or CNS concentrations. Although Huperzine A is brain penetrable, its interaction with efflux transporters (ABCB1 and ABCG2) has not been fully investigated. The aim of the present study was to characterize roles of ABCB1 and ABCG2 in the transmembrane transport of Huperzine A and identify a rate limiting step in its brain distribution. Data obtained from stably transfected MDCK II cells showed that Huperzine A is a substrate of ABCB1 but not ABCG2. ABCB1 inhibitors significantly inhibited ABCB1 mediated efflux of Huperzine A. In Abcb1a−/− mice, the brain to plasma concentration ratio of Huperzine A was significantly increased as compared to the wild type mice, while there were no obvious differences between the wild type and Abcg2−/− mice. Taken together, the present study demonstrated that ABCB1 but not ABCG2 played a predominant role in the efflux of Huperzine A across BBB. The current finding is clinically relevant as changes in ABCB1 activity in the presence of ABCB1 inhibitors or genetic polymorphism may affect efficacy and safety of Huperzine A.Download high-res image (116KB)Download full-size image

Rhein is a major component of the many medicinal herbs such as rhubarb. Despite wide use, intoxication cases associated with rhein-containing herbs are often reported. The present work aimed to investigate if rhein was subject to metabolic activation leading to toxicity. Upon incubations with different species of liver microsomes, three monoglucuronides were identified, corresponding to two hydroxyl glucuronides and one acyl glucuronide via the carboxyl group, respectively. Further study revealed that rhein acyl glucuronide was chemically reactive, and showed cytotoxicity toward hepatocarcinoma cells. In addition, significant species differences in glucuronidation of rhein were observed between laboratory animals and humans. Reaction phenotyping experiments demonstrated that rhein acyl glucuronide was catalyzed predominantly by uridine 5′-diphospho-glucuronosyltransferase 1A1, 1A9, and 2B7. Taken together, the present study confirmed that rhein could be metabolically activated via the formation of acyl glucuronide, especially in human.

•Simultaneous quantitation of three hydrolytic products from the prodrug DW-3-15.•Excellent chromatographic resolution with a short run time.•Specific and sensitive MS detection of ARS, DHA and 10-OHPZQ.•Successful application to pharmacokinetic studies.•Utility in mechanistic investigations on in vivo hydrolysis of the prodrug.Schistosomiasis is an infectious disease that has been recognized as a severe health burden for some regions of the world. While praziquantel is the drug of choice, there is an unmet medical need for novel therapies with greater efficacy and resistant profile. DW-3-15 is a novel and promising prodrug possessing both adult and juvenile schistosomes killing capability. Its proposed hydrolytic products, artesunate (ARS), dihydroartemisinin (DHA) and 10-hydroxypraziquantel (10-OHPZQ), are all active in preventing schistosomal infection in relevant disease models. To support pharmacokinetic and PK-PD studies of DW-3-15, a simple, specific and rapid liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for the simultaneous determination of the three active components in rat plasma. Using a short C18 column (2.1 mm × 50 mm, 5 μm) with linear gradient, a baseline resolution of the three analytes and corresponding internal standards was achieved with a total run time of 6 min. Mass detection was carried out by electrospray ionization in positive MRM mode with ion transitions of m/z 402.2 → m/z 267.3 for ARS, m/z 302.2 → m/z 163.1 for DHA, and m/z 329.2 → m/z 219.4 for 10-OHPZQ. The method was linear over concentration ranges of 1.0–500 ng/mL for ARS, 5.0–2500 ng/mL for DHA, and 1.0–500 ng/mL for 10-OHPZQ. The accuracy was within ±10.0% for ARS, ±6.4% for DHA, and ±13.0% for 10-OHPZQ. The within-run and between-run precision of all three analytes at four concentrations tested were less than 15%, except at the LLOQ for DHA which was between 15 and 20%. The method was successfully applied to pharmacokinetic evaluation of DW-3-15 in rats following intravenous administration.

The prodrug strategy has been explored frequently for a number of marked drugs to obtain better pharmaceutical properties and efficacy and safety profiles. For gemcitabine, a nucleoside analog that has been used widely as a chemotherapeutic agent for the treatment of a variety of cancers, the protection of the amino group from extensive deamination and increase of permeability have been used for oral prodrug development. In the present study, several novel and proprietary monophosphate ester prodrugs of gemcitabine representing different “tail” structures were evaluated for their antiproliferation activities in various tumor cell lines. As compared to LY2334737, a prototype oral prodrug of gemcitabine, the monophosphate ester prodrugs exhibited superior in vitro antiproliferation activity. Among those, compound-3 emerged as a promising prodrug candidate. Data revealed that cellular concentrations of compound-3 were correlated well with its antiproliferation activity and its cellular uptake did not involve human equilibrative nucleoside transporter, suggesting a potential to treat gemcitabine resistant tumors. Compound-3 demonstrated equal or better antitumor efficacy after oral administration as compared to intraperitoneally injected gemcitabine. Taken together, compound-3 has the potential for further development as an orally active antitumor agent.

The prodrug strategy has been explored frequently for a number of marked drugs to obtain better pharmaceutical properties and efficacy and safety profiles. For gemcitabine, a nucleoside analog that has been used widely as a chemotherapeutic agent for the treatment of a variety of cancers, the protection of the amino group from extensive deamination and increase of permeability have been used for oral prodrug development. In the present study, several novel and proprietary monophosphate ester prodrugs of gemcitabine representing different “tail” structures were evaluated for their antiproliferation activities in various tumor cell lines. As compared to LY2334737, a prototype oral prodrug of gemcitabine, the monophosphate ester prodrugs exhibited superior in vitro antiproliferation activity. Among those, compound-3 emerged as a promising prodrug candidate. Data revealed that cellular concentrations of compound-3 were correlated well with its antiproliferation activity and its cellular uptake did not involve human equilibrative nucleoside transporter, suggesting a potential to treat gemcitabine resistant tumors. Compound-3 demonstrated equal or better antitumor efficacy after oral administration as compared to intraperitoneally injected gemcitabine. Taken together, compound-3 has the potential for further development as an orally active antitumor agent.

•Steviol glucuronide (SVG) was the major metabolite of steviol, the aglycone of steviol glycosides.•SVG was not a substrate of efflux transporters such as BCRP, MRP2, MATE1 and P-gp.•Among uptake transporters, OAT3 played a predominant role in the cellular uptake of SVG.•OTA3-mediated uptake of SVG was inhibited by quercetin, telmisartan, diclofenac, and mulberrin.•Inhibition of OAT3 activity by drugs and natural compounds may alter SVG's renal clearance. Steviol glucuronide (SVG) is the major metabolite derived from steviol, the aglycone of stevioside and rebaudioside A. After the ingestion of stevioside and rebaudioside A, SVG is formed and excreted into the urine in humans. In the present study, transporter mediated efflux and uptake of SVG was investigated in order to understand molecular mechanisms underlying its renal clearance. Results showed that SVG was not a substrate of efflux transporters BCRP, MRP2, MATE1 or P-gp. In contrast, OAT3 played a predominant role in the uptake of SVG in comparison to OATP1B1, OATP1B3, or OATP2B1. Quercetin, telmisartan, diclofenac, and mulberrin displayed a relatively strong inhibition against OAT3 mediated uptake of SVG with IC50 values of 1.8, 2.9, 8.0, and 10.0 μM, respectively. Because OAT3 is a major uptake transporter in the kidney, inhibition of OAT3 activity may alter SVG's renal clearance by drugs and natural compounds that are used concomitantly with stevia leaf extracts.Proposed mechanism and involvement of uptake transporters in the transmembrane transport of steviol glucuronide.Download full-size image