Coadministration of cyclosporine strongly enhances the oral bioavailability of docetaxel

Oral delivery of paclitaxel nanocrystal (PNC) with a dual Pgp-CYP3A4 inhibitor: preparation, characterization and antitumor activity

Several molecular inheritances have severely restrained the peroral delivery of taxanes. The main objective of the present investigation was to develop a paclitaxel (PTX) formulation which can circumvent the hurdles of its extremely poor solubility and permeability, Pgp efflux and high pre-systemic metabolism. Positively charged PTX nanocrystals of 209 nm were prepared by sonoprecipitation with high pressure homogenization technique, wherein an arginine based surfactant was explored as a stabilizer. The BET surface area analysis revealed that the surface area of PNC was 8.53 m(2)/gm, reflecting significant rise in surface area with nanonization of PTX. The DSC and XRD pattern suggested that the PTX is in the form of the most stable dihydrate crystal. The PNC showed very rapid dissolution profile compared to plain PTX in both sinks and non-sink conditions. Clarithromycin (CLM) was evaluated as a better alternative to cyclosporin A in improving PTX permeability. The PNC-CLM showed remarkable enhancement of 453% in relative bioavailability along with maintaining the therapeutic concentration of PTX for 8h. Efficacy data in B16 F10 melanoma tumor bearing mice showed substantial reduction in tumor volume and improvement in percentage survival compared to the control group.

PEG-PCL based micelle hydrogels as oral docetaxel delivery systems for breast cancer therapy

In this study, a composite drug delivery system was developed and evaluated for oral delivery of docetaxel: docetaxel-loaded micelles in pH-responsive hydrogel (DTX-micelle-hydrogel). Docetaxel was successfully loaded in micelles with small particle size of 20 nm and high drug loading of 7.76%, which contributed to the drug absorption in the intestinal tract. The experiments of cytotoxicity on 4T1 cells demonstrated the effective antitumor activity of DTX micelles. Meanwhile, a pH-responsive hydrogel was synthesized and optimized for incorporating the docetaxel micelles. The pH-responsiveness and reversibility of the hydrogel were investigated under the pH conditions of the gastrointestinal tract. Furthermore, the DTX-micelle-hydrogel system showed much quicker diffusion of micelles in simulated intestinal fluid than in simulated gastric fluid, which was mainly caused by the change of pH value. The docetaxel released from the micelle-hydrogel system quite slowly, so it had little influence on the absorption of DTX micelles in small intestine. More important, the pharmacokinetic study revealed that the DTX-micelle-hydrogel significantly improved the oral bioavailability of docetaxel (75.6%) about 10 times compared to DTX micelles, and this increase in bioavailability was probably due to the small intestine targeting release of the pH-responsive hydrogel. Consequently, the oral DTX-micelle-hydrogel system was effective in inhibiting tumor growth in subcutaneous 4T1 breast cancer model, and decreased systemic toxicity compared with intravenous treatment. The apoptosis cells in the immunofluorescent studies and the proliferation-positive cells in the immunohistochemical studies were also consistent with the results. Therefore, the DTX-micelle-hydrogel system might be a promising candidate oral drug for breast cancer therapy.

The impact of sustained and intermittent docetaxel chemotherapy regimens on cognition and neural morphology in healthy mice

RATIONALE

A subset of cancer survivors demonstrates impairments in cognition long after chemotherapy completion. At present, it is unclear whether these changes are due to direct neurotoxic effects of chemotherapy.

OBJECTIVES

This study examined the impact of variable docetaxel (DTX) chemotherapy dosing on brain DTX exposure via analyses of neural morphology and changes in cognition.

METHODS

Male CD-1 mice were treated with DTX either intermittently (8 mg/kg i.p. weekly) or via a sustained delivery system (DTX-PoLigel), which continuously releases DTX. Both groups received total DTX doses of 32 mg/kg. Mice were assessed on the novel object recognition (NOR) task and the Morris water maze (MWM) shortly after treatment.

RESULTS

Post-treatment behavioral testing demonstrated impaired NOR in mice treated with either dosing schedule relative to controls. No differences were observed between groups in MWM training and initial testing, though control mice performed better than chance while DTX-treated mice did not. Appreciable amounts of DTX were found in the brain after both treatment regimens. DTX treatment did not significantly increase levels of apoptosis within the CNS. However, some elevation in neural autophagy was observed following DTX treatment. Analysis of astrocytic activation demonstrated that intermittent DTX treatment resulted in an elevation of GFAP-positive astrocytes for 48 h after administration. Sustained chemotherapy demonstrated prolonged but lower levels of astrocyte activation over 9 days following implantation.

CONCLUSIONS

DTX treatment induced cognitive impairment shortly after treatment. Further, these findings suggest an association between DTX dosing, neurotoxicity, and cognitive effects.

Dynamic disordering of liposomal cocktails and the spatio-temporal favorable release of cargoes to circumvent drug resistance

Multidrug resistance (MDR) has been a major impediment to the success of cancer chemotherapy. Extensive efforts have been devoted to the development of drug delivery systems using nanotechnology to reverse MDR in cancer. However, the spontaneous release of drug payloads was always a slow process, which leads to the low intracellular drug concentration resulting in consequent drug insensitivity. To circumvent this limitation, we described a liposomal cocktail (LMDHV) constructed by a pH-responsive molecule (i.e., malachite green carbinol base (MG)) and liposome conjugated with Her-2 antibody for codelivery of doxorubicin (DOX) and verapamil (VER) to suppress drug resistance in Her-2 positive breast cancer. MG inserted in the bilayer as pH responders greatly contributed to the destabilization of the vesicle membrane in low pH, followed by the rapid release of the payloads. LMDHV showed 6-fold reversal efficiency in DOX resistant breast cancer owing to the efficient tumor targeting delivery and rapid burst release of drug intracellularly. Compared to tumor inhibition ratio of treated groups by free DOX (32.4 ± 7.4%), our designed kinetically favorable drug release system exhibited significantly (P < 0.01) enhanced tumor inhibition ratio up to 83.9 ± 12.5%, which is attributed to the remarkably increased drug concentration in cells. The spatio-temporal favorable release of drugs resulted in synergistic inhibition of tumor growth in xenografts. We envision that this new type of liposomal cocktail might be potentially utilized to circumvent drug resistance in the future.

Surface-modified solid lipid nanoparticles for oral delivery of docetaxel: enhanced intestinal absorption and lymphatic uptake

Docetaxel is a potent anticancer drug, but development of an oral formulation has been hindered mainly due to its poor oral bioavailability. In this study, solid lipid nanoparticles (SLNs) surface-modified by Tween 80 or D-alpha-tocopheryl poly(ethylene glycol 1000) succinate (TPGS 1000) were prepared and evaluated in terms of their feasibility as oral delivery systems for docetaxel. Tween 80-emulsified and TPGS 1000-emulsified tristearin-based lipidic nanoparticles were prepared by a solvent-diffusion method, and their particle size distribution, zeta potential, drug loading, and particle morphology were characterized. An in vitro release study showed a sustained-release profile of docetaxel from the SLNs compared with an intravenous docetaxel formulation (Taxotere®). Tween 80-emulsified SLNs showed enhanced intestinal absorption, lymphatic uptake, and relative oral bioavailability of docetaxel compared with Taxotere in rats. These results may be attributable to the absorption-enhancing effects of the tristearin nanoparticle. Moreover, compared with Tween 80-emulsified SLNs, the intestinal absorption and relative oral bioavailability of docetaxel in rats were further improved in TPGS 1000-emulsified SLNs, probably due to better inhibition of drug efflux by TPGS 1000, along with intestinal lymphatic uptake. Taken together, it is worth noting that these surface-modified SLNs may serve as efficient oral delivery systems for docetaxel.

Oral anticancer drugs: mechanisms of low bioavailability and strategies for improvement

The use of oral anticancer drugs has increased during the last decade, because of patient preference, lower costs, proven efficacy, lack of infusion-related inconveniences, and the opportunity to develop chronic treatment regimens. Oral administration of anticancer drugs is, however, often hampered by limited bioavailability of the drug, which is associated with a wide variability. Since most anticancer drugs have a narrow therapeutic window and are dosed at or close to the maximum tolerated dose, a wide variability in the bioavailability can have a negative impact on treatment outcome. This review discusses mechanisms of low bioavailability of oral anticancer drugs and strategies for improvement. The extent of oral bioavailability depends on many factors, including release of the drug from the pharmaceutical dosage form, a drug's stability in the gastrointestinal tract, factors affecting dissolution, the rate of passage through the gut wall, and the pre-systemic metabolism in the gut wall and liver. These factors are divided into pharmaceutical limitations, physiological endogenous limitations, and patient-specific limitations. There are several strategies to reduce or overcome these limitations. First, pharmaceutical adjustment of the formulation or the physicochemical characteristics of the drug can improve the dissolution rate and absorption. Second, pharmacological interventions by combining the drug with inhibitors of transporter proteins and/or pre-systemic metabolizing enzymes can overcome the physiological endogenous limitations. Third, chemical modification of a drug by synthesis of a derivative, salt form, or prodrug could enhance the bioavailability by improving the absorption and bypassing physiological endogenous limitations. Although the bioavailability can be enhanced by various strategies, the development of novel oral products with low solubility or cell membrane permeability remains cumbersome and is often unsuccessful. The main reasons are unacceptable variation in the bioavailability and high investment costs. Furthermore, novel oral anticancer drugs are frequently associated with toxic effects including unacceptable gastrointestinal adverse effects. Therefore, compliance is often suboptimal, which may negatively influence treatment outcome.

Enhanced oral delivery of docetaxel using thiolated chitosan nanoparticles: preparation, in vitro and in vivo studies

The aim of this study was to evaluate a nanoparticulate system with mucoadhesion properties composed of a core of polymethyl methacrylate surrounded by a shell of thiolated chitosan (Ch-GSH-pMMA) for enhancing oral bioavailability of docetaxel (DTX), an anticancer drug. DTX-loaded nanoparticles were prepared by emulsion polymerization method using cerium ammonium nitrate as an initiator. Physicochemical properties of the nanoparticles such as particle size, size distribution, morphology, drug loading, and entrapment efficiency were characterized. The pharmacokinetic study was carried out in vivo using wistar rats. The half-life of DTX-loaded NPs was about 9 times longer than oral DTX used as positive control. The oral bioavailability of DTX was increased to 68.9% for DTX-loaded nanoparticles compared to 6.5% for positive control. The nanoparticles showed stronger effect on the reduction of the transepithelial electrical resistance (TEER) of Caco-2 cell monolayer by opening the tight junctions. According to apparent permeability coefficient (P(app)) results, the DTX-loaded NPs showed more specific permeation across the Caco-2 cell monolayer in comparison to the DTX. In conclusion, the nanoparticles prepared in this study showed promising results for the development of an oral drug delivery system for anticancer drugs.

Docetaxel-loaded thermosensitive liquid suppository: optimization of rheological properties

The main purpose of this work was to optimize the rheological properties of docetaxel (DCT)-loaded thermosensitive liquid suppositories for rectal administration. DCT-loaded liquid suppositories were prepared by a cold method and characterized in terms of physicochemical and viscoelastic properties. Major formulation parameters including poloxamer (P407) and Tween 80 were optimized to adjust the thermogelling and mucoadhesive properties for rectal administration. Notably, the gel strength and mucoadhesive force significantly increased with the increase in these variables. Furthermore, DCT incorporation did not alter the viscoelastic behavior, and the mean particle size of nanomicelles in it was approximately 16 nm with a distinct spherical shape. The formulation existed as liquid at room temperature and transformed into gel at physiological temperature through the reverse gelation phenomenon. Thus, DCT-loaded thermosensitive liquid suppositories [DCT/P407/P188/Tween 80 (0.25/11/15/10 %)] with optimal gel properties were easy to prepare and administer rectally, and might enable the gel to stay in the rectum without getting out from rectum.

Pharmaceutical nanotechnology for oral delivery of anticancer drugs

Oral chemotherapy is an important topic in the 21st century medicine, which may radically change the current regimen of chemotherapy and greatly improve the quality of life of the patients. Unfortunately, most anticancer drugs, especially those of high therapeutic efficacy such as paclitaxel and docetaxel, are not orally bioavailable due to the gastrointestinal (GI) drug barrier. The molecular basis of the GI barrier has been found mainly due to the multidrug efflux proteins, i.e. P-type glycoproteins (P-gp), which are rich in the epithelial cell membranes in the GI tract. Medical solution for oral chemotherapy is to apply P-gp inhibitors such as cyclosporine A, which, however, suppress the body's immune system either, thus causing medical complication. Pharmaceutical nanotechnology, which is to apply and further develop nanotechnology to solve the problems in drug delivery, may provide a better solution and thus change the way we make drug and the way we take drug. This review is focused on the problems encountered in oral chemotherapy and the pharmaceutical nanotechnology solutions such as prodrugs, nanoemulsions, dendrimers, micelles, liposomes, solid lipid nanoparticles and nanoparticles of biodegradable polymers. Proof-of-concept in vitro and in vivo results for oral delivery of anticancer drugs by the various nanocarriers, which can be found so far from the literature, are provided.

Docetaxel-loaded thermosensitive and bioadhesive nanomicelles as a rectal drug delivery system for enhanced chemotherapeutic effect

PURPOSE

To investigate the potential of thermosensitive and biadhesive nanomicelles in improving the bioavailability of docetaxel (DCT) and its chemotherapeutic effect.

METHOD

DCT-loaded nanomicelles were prepared by emulsufication and characterized in terms of physico-chemical and visco-elastic parameters. The optimzed formulation was evaluated for in vivo localization, pharmacokinetic and anti-tumor efficacy.

RESULTS

The hydrodynamic size of DCT-loaded nanomicelles was approximately 13 nm and the nanomicelles exhibited a sufficient gelation strength (9250 mPa·s) and bioadhesive force (2100 dyn/cm²) to be retained in the upper part of rectum. We observed a high rectal bioavailability of 29% DCT compared to that following oral administration in rats, as it successfully evaded the multidrug efflux transporters and hepatic first-pass metabolism. Plasma concentration around ∼50 ng/mL was maintained throughout the study period (12 h) while Taxotere® attained subtherapeutic range within 4 h of drug administration. Results also revealed that the rectally administered DCT-loaded nanomicelles exhibited a significant anti-tumor effect (200 mm³) with a reduced toxicity profile when compared to orally administered DCT (950 mm³). Furthermore, histological study showed that the rectal mucosa was completely intact with no signs of irritation upon treatment with DCT-loaded nanomicelles.

CONCLUSIONS

Taken together, our novel thermosensitive and biadhesive nanomicelles demonstrated the ability to improve the bioavailability and chemotherapeutic potential of DCT in vivo. To the best of our knowledge, this is the first report describing the rectal delivery of DCT-loaded nanomicelles.

Thiolated chitosan-modified PLA-PCL-TPGS nanoparticles for oral chemotherapy of lung cancer

Oral chemotherapy is a key step towards 'chemotherapy at home', a dream of cancer patients, which will radically change the clinical practice of chemotherapy and greatly improve the quality of life of the patients. In this research, three types of nanoparticle formulation from commercial PCL and self-synthesized d-α-tocopheryl polyethylene glycol 1000 succinate (PLA-PCL-TPGS) random copolymer were prepared in this research for oral delivery of antitumor agents, including thiolated chitosan-modified PCL nanoparticles, unmodified PLA-PCL-TPGS nanoparticles, and thiolated chitosan-modified PLA-PCL-TPGS nanoparticles. Firstly, the PLA-PCL-TPGS random copolymer was synthesized and characterized. Thiolated chitosan greatly increases its mucoadhesiveness and permeation properties, thus increasing the chances of nanoparticle uptake by the gastrointestinal mucosa and improving drug absorption. The PLA-PCL-TPGS nanoparticles were found by FESEM that they are of spherical shape and around 200 nm in diameter. The surface charge of PLA-PCL-TPGS nanoparticles was reversed from anionic to cationic after thiolated chitosan modification. The thiolated chitosan-modified PLA-PCL-TPGS nanoparticles have significantly higher level of the cell uptake than that of thiolated chitosan-modified PLGA nanoparticles and unmodified PLA-PCL-TPGS nanoparticles. In vitro cell viability studies showed advantages of the thiolated chitosan-modified PLA-PCL-TPGS nanoparticles over Taxol® in terms of cytotoxicity against A549 cells. It seems that the mucoadhesive nanoparticles can increase paclitaxel transport by opening tight junctions and bypassing the efflux pump of P-glycoprotein. In conclusion, PLA-PCL-TPGS nanoparticles modified by thiolated chitosan could enhance the cellular uptake and cytotoxicity, which revealed a potential application for oral chemotherapy of lung cancer.

Pharmacologic modulation strategies to reduce dose requirements of anticancer therapy while preserving clinical efficacy

Drug interactions may be exploited to overcome pharmacokinetic issues in order to improve the therapeutic index of a drug, with clinical goals of reducing the dose of the active drug while preserving efficacy or reducing toxicity. This strategy has been used in infectious disease and transplant medicine, and, more recently, in oncology. Pharmacologic modulation strategies range from coadministration of either a drug that inhibits a metabolizing enzyme that would inactivate the drug of interest, a drug that induces an enzyme that activates the drug of interest or a drug that inhibits transporters that affect the uptake or elimination of the drug of interest. This review will discuss pharmacologic modulation strategies that have been tested clinically in order to increase systemic drug exposure. Important examples include ketoconazole inhibition of hepatic CYP3A4 in order to increase systemic exposure to docetaxel, irinotecan and etoposide, and cyclosporine inhibition of intestinal ATP-binding cassette transporters in order to decrease the toxicity of irinotecan and increase the bioavailability of oral docetaxel, paclitaxel and topotecan.

Interferon-alpha improves docetaxel antitumoral and antimetastatic efficiency in Lewis lung carcinoma bearing mice

AIMS

Interferon-alpha (IFN-α) was shown to reduce P-glycoprotein (P-gp) expression and activity in several tissues. The purpose of this study was to evaluate the impact of IFN-α pretreatment on the antitumoral and antimetastatic, Docetaxel (DTX, P-gp substrate), on Lewis Lung Cancer (3LL) bearing mice and to correlate it to DTX pharmacokinetics.

MAIN METHODS

Six groups of C57/Bl6 mice received subcutaneous (s.c.) 2.10(6) 3LL cells, then IFN-α 4MIU/kg for 7days, then received or did not receive i.v. or oral DTX (30mg/kg). Pharmacokinetic studies were done on a part of the mice: DTX concentrations were assessed in plasma and tumors, where AUC were estimated with the Bailer method, and half-lives and MRT were determined with a non-compartmental analysis. Tumor growth was assessed more than 21days: animals were then sacrificed and lung metastases number was counted. Kaplan-Meier analysis was made to analyze survival data during the survey period.

KEY FINDINGS

DTX i.v. associated with IFN-α significantly improved mouse survival (19.6±0.6days vs. 17.1±0.8days for control mice, p=0.047) with greater antimetastatic effects (87.5% reduction in the number of metastases compared to control mice). The effect on tumor growth was not modified within the IFN-α/DTX i.v. treated groups when compared to mice receiving DTX i.v. alone. The pharmacokinetic analysis showed an increase of DTX concentrations in tumors at 30min after DTX i.v. administration and an increase in the oral bioavailability of orally given DTX following an IFN-α treatment.

SIGNIFICANCE

Our study established that IFN-α increases DTX uptake in tumors, improves its antitumoral efficiency and improves animals' survival.

Phase II study of oral docetaxel and cyclosporine in canine epithelial cancer

The goal of the current study was to determine the efficacy of oral docetaxel in combination with cyclosporine in the treatment of canine epithelial cancer. Requirements for eligibility were histological confirmation of epithelial neoplasia, measurable disease, no chemotherapy treatment within 2 weeks, and a life expectancy of ≥ 3 months. Fifty-one dogs were enrolled. All dogs received 1.625 mg kg(-1) of docetaxel with 5 mg kg(-1) of cyclosporine (DT/CSA) by gavage. Ten dogs had progressive disease at 2 weeks, one dog died, and one dog was withdrawn from the study. Thirty-nine dogs were given a second dose of DT/CSA, three each receiving a third or fourth dose. Eight dogs had a dose reduction (1.5 mg kg(-1)) and six dogs had treatment delays primarily for gastrointestinal toxicity. The overall response rate was 16.7% (8/48 had a partial response there were no complete responses). The highest response rate was seen in dogs with oral squamous cell carcinoma (50%; 6/12).

Intestinal permeation enhancement of docetaxel encapsulated into methyl-β-cyclodextrin/poly(isobutylcyanoacrylate) nanoparticles coated with thiolated chitosan

In this study we investigated the potential of mucoadhesive nanoparticles to enhance the intestinal permeability of docetaxel (Dtx). These nanoparticles were composed of methyl-β-cyclodextrin (Me-β-CD) combined with poly(isobutylcyanoacrylate) and coated with thiolated chitosan. In order to encapsulate the highest amount of Dtx into nanoparticles, the anionic emulsion polymerization of isobutylcyanoacrylate was carried out in a solution of Me-β-CD/Dtx inclusion complex. The resulting nanoparticles were spherical with diameters ranging from 200 to 400 nm, and positively charged. Depending on the formulation, the encapsulation efficiency of Dtx was 70-80%. In vitro experiments in simulated intestinal medium containing 1% w/v of pancreatin showed that Dtx was gradually released to reach 60% after 24h and 100% after 48 h. The capacity of these nanoparticles to enhance the flux of Dtx across the intestinal membrane was then investigated using the Ussing chamber technique. The intestinal permeation of Dtx loaded into nanoparticles was found to be higher than the ethanol control solution of Dtx. Interestingly, when mucoadhesive interactions between nanoparticles and the mucosa were avoided, the intestinal permeation of Dtx significantly decreased, confirming that the mucoadhesion of the nanoparticles was a mandatory condition to enhance the intestinal permeation of Dtx.

Tolerability and pharmacokinetics of a new P-glycoprotein inhibitor, HM30181, in healthy Korean male volunteers: single- and multiple-dose randomized, placebo-controlled studies

BACKGROUND

HM30181 is an oral P-glycoprotein (P-gp) inhibitor developed to enhance the oral bioavailability of P-gp substrate drugs.

OBJECTIVE

The objective of this study was to investigate the tolerability and pharmacokinetic properties of HM30181 after single and multiple oral administrations to healthy Korean male volunteers. The study was performed to meet regulatory criteria for marketing the test product in South Korea.

METHODS

A dose-block-randomized, double-blind, placebo-controlled, dose-escalation study was performed in 180-, 360-, 600-, and 900-mg single-dose groups and 60-, 180-, and 360-mg multiple-dose groups with 10 subjects (8 active; 2 placebo) per group. In the single-dose study, blood and urine samples were collected for up to 120 hours after drug administration. In the multiple-dose study, subjects received the study drug or placebo orally once daily for 5 days. Blood samples were collected up to 624 hours after the last dose, and up to 24 hours after the first dose to evaluate the accumulation index. Urine samples were collected up to 120 hours after the last dose. Pharmacokinetic analysis was performed using noncompartmental methods. Adverse events were collected by the spontaneous reporting of the subjects or when subjects were asked general health-related questions.

RESULTS

Thirty and 70 healthy male volunteers completed the single- and multiple-dose studies, respectively. Mean (SD) age and body weight of subjects in the single administration group were 24.0 (1.8) years and 68.8 (7.4) kg, respectively, and those of the multiple administration group were 24.5 (2.6) years and 67.6 (7.7) kg, respectively. The plasma concentrations peaked at 14 to 42 hours and declined with t(½) of 75.7 to 169.3 hours after single administration, and peaked at 5.5 to 8.0 hours and declined with t(½) of 153.5 to 215.2 hours after multiple administrations. C(max) and area under the concentration curve within dosing intervals (AUC(τ)) increased dose dependently after single administration; however, dose-dependent increases in C(max) and AUC(τ) were not observed after multiple administrations. The fraction of drug excreted unchanged in urine was minimal, with values <0.01% in all dose groups. HM30181 accumulated after multiple administrations with an accumulation index of 4.0 to 7.4. All adverse events reported were mild in intensity; there were no serious adverse events reported. The most frequently reported adverse event was gastrointestinal disorder.

CONCLUSIONS

HM30181 was well tolerated after oral administration within the dose range evaluated, with the exception of the repeated administration of 360 mg, for which gastrointestinal disorders were frequently reported. The systemic exposure of HM30181 was relatively low, and dose proportional properties of HM30181 were not observed.

Effect of dose and dosage interval on the oral bioavailability of docetaxel in combination with a curcumin self-emulsifying drug delivery system (SEDDS)

The present study investigated the effects of a curcumin self-emulsifying drug delivery systems (SEDDS) on the pharmacokinetics of orally administered docetaxel in rats. A single dose of docetaxel was orally administered (30 mg/kg) alone or after oral curcumin SEDDS (25, 50, 100 and 150 mg/kg) administration with time intervals of 0, 15 and 30 min, respectively. After oral administration, the C (max) and the area under the plasma concentration-time curve (AUC) of docetaxel were significantly increased (0 min, p < 0.05; 15 and 30 min, p < 0.01) by 2.2, 4.7 and 4.6 times and 2.0, 3.8 and 4.1 times compared to that of control group, respectively, after treatment with curcumin SEDDS (100 mg/kg) for each interval. Moreover, The C (max) of docetaxel was increased by 2.6 and 4.4 times in response to 25 and 50 mg/kg curcumin SEDDS treatment, respectively, the corresponding AUC was increased by about 2.4 and 3.1 times, and consequently the absolute bioavailabilities of docetaxel in these two treatment groups were 7.9 and 10.4%, respectively, which showed a significant increase of about 2.4- and 3.2-fold in comparison to the control value (3.3%). However, no further increase in either AUC or C (max) values of docetaxel was observed as the curcumin SEDDS dose was increased from 50 to 150 mg/kg. It is worth noting that the presence of curcumin SEDDS did not significantly decrease the systemic clearance, which was shown by the almost unchanged terminal half-life (t (1/2)) of docetaxel in all treatment groups. Thus, the enhanced bioavailability of oral docetaxel by curcumin SEDDS seemed to be likely due to an inhibition function of cytochrome P450 (CYP) 3A and P-glycoprotein (Pgp) in the intestines of the rats. However, further in vivo studies are needed to verify these hypotheses.

Improving cancer chemotherapy with modulators of ABC drug transporters

ATP-binding cassette (ABC) transporters, P-glycoprotein (P-gp, ABCB1) and ABCG2, are membrane proteins that couple the energy derived from ATP hydrolysis to efflux many chemically diverse compounds across the plasma membrane, thereby playing a critical and important physiological role in protecting cells from xenobiotics. These transporters are also implicated in the development of multidrug resistance (MDR) in cancer cells that have been treated with chemotherapeutics. One approach to blocking the efflux capability of an ABC transporter in a cell or tissue is inhibiting the activity of the transporters with a modulator. Since ABC transporter modulators can be used in combination with chemotherapeutics to increase the effective intracellular concentration of anticancer drugs, the possible impact of modulators of ABC drug transporters is of great clinical interest. Another possible clinical use of modulators that has recently attracted attention is their ability to increase oral bioavailability or increase tissue penetration of drugs transported by the transporters. Several preclinical and clinical studies have been performed to evaluate the feasibility and the safety of this approach. The primary focus of this review is to discuss progress made in recent years in the identification and applicability of compounds that may serve as ABC transporter modulators and the possible role of these compounds in altering the pharmacokinetics and pharmacodynamics of therapeutic drugs used in the clinic.

Preparation and characterization of emulsified solid dispersions containing docetaxel

An emulsified solid dispersion of docetaxel was prepared and characterized in vitro. In contrast to conventional solid dispersions, emulsifying pharmaceutical excipients and hydroxypropyl methylcellulose (HPMC) as a supersaturation promoter were introduced into the PEG6000-based solid dispersion to further improve its solubilizing capability. The solubility, dissolution in vitro and stability of the prepared emulsified solid dispersions were studied taking into consideration of the effects of different emulsifying excipients, preparation methods and the media. Results of the emulsified solid dispersion of docetaxel showed that the solubility and dissolution at 2 h were 34.2- and 12.7-fold higher than the crude powder. The type of emulsifying excipient used had a significant influence on the dissolution of the emulsified solid dispersion. The dissolution of the emulsified solid dispersion prepared by the solvent-melting method or the solvent method was higher than the melting method. There were no apparent differences among the dissolution media utilized. The status of the drug in the emulsified solid dispersion was observed in an amorphous or a molecular dispersion state by differential thermal analysis and powder Xray diffraction. In conclusion, the incorporation of emulsifying pharmaceutical excipients and HPMC with polymers into a solid dispersion could be a new and useful tool to greatly increase the solubility and dissolution of poorly water-soluble drugs.

Oral Delivery of DMAB-Modified Docetaxel-Loaded PLGA-TPGS Nanoparticles for Cancer Chemotherapy

Three types of nanoparticle formulation from biodegradable PLGA-TPGS random copolymer were developed in this research for oral administration of anticancer drugs, which include DMAB-modified PLGA nanoparticles, unmodified PLGA-TPGS nanoparticles and DMAB-modified PLGA-TPGS nanoparticles. Firstly, the PLGA-TPGS random copolymer was synthesized and characterized. DMAB was used to increase retention time at the cell surface, thus increasing the chances of particle uptake and improving oral drug bioavailability. Nanoparticles were found to be of spherical shape with an average particle diameter of around 250 nm. The surface charge of PLGA-TPGS nanoparticles was changed to positive after DMAB modification. The results also showed that the DMAB-modified PLGA-TPGS nanoparticles have significantly higher level of the cellular uptake than that of DMAB-modified PLGA nanoparticles and unmodified PLGA-TPGS nanoparticles. In vitro, cytotoxicity experiment showed advantages of the DMAB-modified PLGA-TPGS nanoparticle formulation over commercial Taxotere(®) in terms of cytotoxicity against MCF-7 cells. In conclusion, oral chemotherapy by DMAB-modified PLGA-TPGS nanoparticle formulation is an attractive and promising treatment option for patients.

Effects of morin on the pharmacokinetics of docetaxel in rats with 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumors

Docetaxel is a P-glycoprotein (P-gp) substrate and metabolized via cytochrome P450 (CYP) 3A subfamily in rats. Morin is an inhibitor of both CYPs and P-gp. Hence, the effects of morin on the intravenous and oral pharmacokinetics of docetaxel were investigated using 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumor rats (DMBA rats) as an animal model of human breast cancer. Docetaxel was administered intravenously (4 mg/kg) and orally (20 mg/kg) without and with morin (15 mg/kg) in DMBA rats. After the intravenous administration of docetaxel in control and DMBA rats with and without morin, the values of non-renal clearance and area under the plasma concentration-time (AUC) for docetaxel were comparable. Morin did not increase AUC or the absolute oral bioavailability (F) for docetaxel after the oral administration of docetaxel in control and DMBA rats with and without morin. The inhibition of hepatic and intestinal metabolism of docetaxel by morin and/or DMBA and the effect of intestinal P-gp inhibition by morin on the pharmacokinetics of docetaxel did not seem to be considerable in DMBA-induced mammary tumor rats.

Isolation of modulators of the liver-specific organic anion-transporting polypeptides (OATPs) 1B1 and 1B3 from Rollinia emarginata Schlecht (Annonaceae)

Organic anion-transporting polypeptides 1B1 and 1B3 (OATP1B1 and OATP1B3) are liver-specific transporters that mediate the uptake of a broad range of drugs into hepatocytes, including statins, antibiotics, and many anticancer drugs. Compounds that alter transport by one or both of these OATPs could potentially be used to target drugs to hepatocytes or improve the bioavailability of drugs that are cleared by the liver. In this study, we applied a bioassay-guided isolation approach to identify such compounds from the organic extract of Rollinia emarginata Schlecht (Annonaceae). Fractions of the plant extract were screened for effects on OATP1B1- and OATP1B3-mediated transport of the model substrates estradiol-17β-glucuronide and estrone-3-sulfate. We isolated three compounds, ursolic acid, oleanolic acid, and 8-trans-p-coumaroyloxy-α-terpineol, which inhibited estradiol-17β-glucuronide uptake by OATP1B1 but not OATP1B3. In addition, a rare compound, quercetin 3-O-α-l-arabinopyranosyl(1→2) α-L-rhamnopyranoside, was identified that had distinct effects on each OATP. OATP1B1 was strongly inhibited, as was OATP1B3-mediated transport of estradiol-17β-glucuronide. However, OATP1B3-mediated uptake of estrone-3-sulfate was stimulated 4- to 5-fold. Kinetic analysis of this stimulation revealed that the apparent affinity for estrone-3-sulfate was increased (decreased K(m)), whereas the maximal rate of transport (V(max)) was significantly reduced. These results demonstrate a mechanism through which the hepatic uptake of drug OATP substrates could be stimulated.

Interactions of dietary phytochemicals with ABC transporters: possible implications for drug disposition and multidrug resistance in cancer

Common foods, such as fruits and vegetables, contain a large variety of secondary metabolites known as phytochemicals, many of which have been associated with health benefits. However, there is a limited knowledge of the processes by which these, mainly charged, phytochemicals (and/or their metabolites) are absorbed into the body, reach their biological target, and how they are eliminated. Recent studies have indicated that some of these phytochemicals are substrates and modulators of specific members of the superfamily of ABC transporting proteins. In this review, we present the reported interactions between the different classes of phytochemicals and ABC transporters and the mechanism by which they modulate the activity of these transporters. We also discuss the implications that such interactions may have on the pharmacokinetics of xenobiotics and the possible role of phytochemicals in the reversal of multidrug resistance in cancer chemotherapy.

A critical analysis of the interplay between cytochrome P450 3A and P-glycoprotein: recent insights from knockout and transgenic mice

CYP3A is one of the most important drug-metabolizing enzymes, determining the first-pass metabolism, oral bioavailability, and elimination of many drugs. It is also an important determinant of variable drug exposure and is involved in many drug-drug interactions. Recent studies with CYP3A knockout and transgenic mice have yielded a number of key insights that are important to consider during drug discovery and development. For instance, studies with tissue-specific CYP3A-transgenic mice have highlighted the importance of intestinal CYP3A-dependent metabolism. They also revealed that intestinal CYP3A plays an important role in the regulation of various drug-handling systems in the liver. Intestinal CYP3A activity can thus have far-reaching pharmacological effects. Besides CYP3A, the active drug efflux transporter P-glycoprotein also has a strong effect on the pharmacokinetics of numerous drugs. CYP3A and P-glycoprotein have an extensive overlap in their substrate spectrum. It has been hypothesized that for many drugs, the combined activity of CYP3A and P-glycoprotein makes for efficient intestinal first-pass metabolism of orally administered drugs as a result of a potentially synergistic collaboration. However, there is only limited in vitro and in vivo evidence for this hypothesis. There has also been some confusion in the field about what synergy actually means in this case. Our recent studies with Cyp3a/P-glycoprotein combination knockout mice have provided further insights into the CYP3A-P-glycoprotein interplay. We here present our view of the status of the synergy hypothesis and an attempt to clarify the existing confusion about synergy. We hope that this will facilitate further critical testing of the hypothesis and improve communication among researchers. Above all, the recent findings and insights into the interplay between CYP3A and P-glycoprotein may have implications for improving oral drug bioavailability and reducing adverse side effects.

Population pharmacokinetics of intravenously and orally administered docetaxel with or without co-administration of ritonavir in patients with advanced cancer

AIM

Docetaxel has a low oral bioavailability due to affinity for P-glycoprotein and cytochrome P450 (CYP) 3A4 enzymes. Inhibition of the CYP3A4 enzymes by ritonavir resulted in increased oral bioavailability. The aim of this study was to develop a population pharmacokinetic (PK) model and to evaluate and quantify the influence of ritonavir on the PK of docetaxel.

METHODS

Data from two clinical trials were included in the data analysis, in which docetaxel (75 mg m(-2) or 100 mg) had been administered intravenously or orally (10 mg or 100 mg) with or without co-administration of oral ritonavir (100 mg). Population modelling was performed using non-linear mixed effects modelling. A three-compartment model was used to describe the i.v. data. PK data after oral administration, with or without co-administration of ritonavir, were incorporated into the model.

RESULTS

Gut bioavailability of docetaxel increased approximately two-fold from 19 to 39% (CV 13%) with ritonavir co-administration. The hepatic extraction ratio and the elimination rate of docetaxel were best described by estimating the intrinsic clearance. Ritonavir was found to inhibit in a concentration dependent manner the intrinsic clearance of docetaxel, which was described by an inhibition constant of 0.028 microg ml(-1) (CV 36%). A maximum inhibition of docetaxel clearance of more then 90% was reached.

CONCLUSIONS

A PK model describing both the PK of orally and intravenously administered docetaxel in combination with ritonavir, was successfully developed. Co-administration of ritonavir lead to increased oral absorption and reduced elimination rate of docetaxel.

High plasma levels and effective lymphatic uptake of docetaxel in an orally available nanotransporter formulation

Docetaxel, an efficient chemotherapeutic drug, exhibits low and variable oral bioavailability due to the active efflux by P-glycoprotein (P-gp) and more so to CYP3A4 gut metabolism. Using a spray-drying technique, docetaxel was incorporated in PLGA [poly(lactic-co-glycolic acid)] nanocapsules (NC) which were embedded in entero-coated microparticles. An oral administration of the NC formulation elicited a higher absolute bioavailability than both a docetaxel solution (276%) and a free docetaxel NC formulation (400%) injected intravenously, a 5-mg/kg dose. The batches (B) I and II NC formulations elicited C(max) values that were 1,735% and 2,254%, respectively; higher than the C(max) value of the oral docetaxel solution combined with blank microparticles, a 10-mg/kg dose. No significant difference in AUC (area under curve) was observed between the batches. These unexpected results can be explained only if the pharmacokinetics of docetaxel had been modified. It was shown that NCs released from the microparticles penetrated the enterocytes, bypassing P-gp; apparently circumventing gut metabolism and accumulating within the lymphatic system from where both intact or biodegraded NCs and free docetaxel were progressively released into the circulation as plausibly supported by the fluorescent imaging results. Furthermore, the circulating docetaxel in plasma was unencapsulated and circulated either in free form or bound to albumin. Both free docetaxel NCs and microparticles exhibited in vitro efficacy on WRC 256 cells suggesting that the activity of docetaxel was not altered. This delivery concept has potential for clinical translation, perhaps allowing docetaxel chemotherapy to be switched from intravenous to oral delivery.

Physiologically based predictions of the impact of inhibition of intestinal and hepatic metabolism on human pharmacokinetics of CYP3A substrates

The first objective of the present study was to predict the pharmacokinetics of selected CYP3A substrates administered at a single oral dose to human. The second objective was to predict pharmacokinetics of the selected drugs in presence of inhibitors of the intestinal and/or hepatic CYP3A activity. We developed a whole-body physiologically based pharmacokinetics (WB-PBPK) model accounting for presystemic elimination of midazolam (MDZ), alprazolam (APZ), triazolam (TRZ), and simvastatin (SMV). The model also accounted for concomitant administration of the above-mentioned drugs with CYP3A inhibitors, namely ketoconazole (KTZ), itraconazole (ITZ), diltiazem (DTZ), saquinavir (SQV), and a furanocoumarin contained in grape-fruit juice (GFJ), namely 6',7'-dihydroxybergamottin (DHB). Model predictions were compared to published clinical data. An uncertainty analysis was performed to account for the variability and uncertainty of model parameters when predicting the model outcomes. We also briefly report on the results of our efforts to develop a global sensitivity analysis and its application to the current WB-PBPK model. Considering the current criterion for a successful prediction, judged satisfied once the clinical data are captured within the 5th and 95th percentiles of the predicted concentration-time profiles, a successful prediction has been obtained for a single oral administration of MDZ and SMV. For APZ and TRZ, however, a slight deviation toward the 95th percentile was observed especially for C(max) but, overall, the in vivo profiles were well captured by the PBPK model. Moreover, the impact of DHB-mediated inhibition on the extent of intestinal pre-systemic elimination of MDZ and SMV has been accurately predicted by the proposed PBPK model. For concomitant administrations of MDZ and ITZ, APZ and KTZ, as well as SMV and DTZ, the in vivo concentration-time profiles were accurately captured by the model. A slight deviation was observed for SMV when coadministered with ITZ, whereas more important deviations have been obtained between the model predictions and in vivo concentration-time profiles of MDZ coadministered with SQV. The same observation was made for TRZ when administered with KTZ. Most of the pharmacokinetic parameters predicted by the PBPK model were successfully predicted within a two-fold error range either in the absence or presence of metabolism-based inhibition. Overall, the present study demonstrated the ability of the PBPK model to predict DDI of CYP3A substrates with promising accuracy.

Effects of tesmilifene, a substrate of CYP3A and an inhibitor of P-glycoprotein, on the pharmacokinetics of intravenous and oral docetaxel in rats

OBJECTIVES

It has been reported that docetaxel is a P-glycoprotein substrate and is metabolized via the cytochrome P450 (CYP) 3A subfamily in rats. Tesmilifene is a substrate of the CYP3A subfamily and is an inhibitor of P-glycoprotein. Thus, the effects of various doses of tesmilifene on the pharmacokinetics of intravenous and orally administered docetaxel have been investigated in rats.

METHODS

Docetaxel (20 mg/kg as base) was administered intravenously and orally without and with tesmilifene (5, 10, and 20 mg/kg) in rats.

KEY FINDINGS

After intravenous administration of docetaxel with tesmilifene, the values of nonrenal clearance (CL(NR)) and area under the plasma concentration-time (AUC) for docetaxel were comparable with those without tesmilifene. Tesmilifene did not increase the values of AUC or of absolute oral bioavailability (F) for docetaxel after oral administration of docetaxel with tesmilifene.

CONCLUSIONS

The inhibition for the metabolism of docetaxel via hepatic and intestinal CYP3A subfamily, and inhibition of P-glycoprotein-mediated efflux of docetaxel in the intestine by tesmilifene were almost negligible. The extremely low value of F for docetaxel was due to the incomplete absorption from the gastrointestinal tract and considerable first-pass metabolism of docetaxel in rats.

Loperamide modifies the tissue disposition kinetics of ivermectin in rats

Ivermectin (IVM) is a broad-spectrum antiparasitic drug extensively used in human and veterinary medicine that is largely excreted in bile and faeces. Loperamide (LPM) is an opioid derivative that reduces gastrointestinal secretions and motility. Both IVM and LPM have been reported to act as P-glycoprotein substrates (P-GP). The goal of the present work was to study the LPM-induced modifications to the pattern of tissue distribution for IVM. Thirty-six Wistar male rats were randomly allocated to two groups (n = 18) and treated subcutaneously with IVM alone or co-administered with LPM. Rats were killed at different times post-treatment and samples (blood and tissues) were collected and analyzed by HPLC. The presence of LPM induced a marked enhancement in the IVM plasma concentrations, resulting in a significantly higher area under concentration time curve (AUC) value (P &lt; 0.01) than that obtained after the administration of IVM alone. Significantly higher IVM availabilities in the liver tissue and small intestine wall (P &lt; 0.05) were obtained in the presence of LPM. There were no statistically significant differences in drug availability in the large intestinal wall after both treatments. However, LPM induced a marked decrease in the amount of IVM recovered in the large intestinal lumen content. The ratio between IVM concentrations in the large intestinal luminal content and plasma at day 1 post-treatment was 4.64-fold higher in the absence of LPM. The delayed intestinal transit time caused by LPM accounting for an extended plasma–intestine recycling time, and a potential competition between IVM and LPM for the P-GP-mediated bile–intestinal secretion processes, may account for the enhanced IVM systemic availability reported in the current study.

Effect of P-glycoprotein inhibition on methadone analgesia and brain distribution in the rat

Methadone is an opiate drug that has been identified as an in-vitro substrate of the efflux pump P-glycoprotein (P-gp), active in the intestinal epithelium and in the blood–brain barrier (BBB), among other sites. The objective of this study was to test in vivo, in the rat model, the role of P-gp modulation on the analgesic effect and brain uptake of methadone, as well as identify the most relevant site via dual oral and intravenous (i.v.) experiments. The P-gp specific inhibitor (valspodar or PSC833) was preadministered (10 mg kg−1 i.v.) to test groups. Analgesia was measured using the tailflick test. The ED50 for oral methadone (2, 3, 6 and 8 mg kg−1) decreased three-fold in valspodar groups compared with controls (2.23 + 0.002 mg kg−1 and 6.07 + 0.07 mg kg−1; P &lt; 0.0001). The overall analgesic effect (% antinociception) was elevated 3.1 times in pretreated compared with control rats (90.65% + 0.22 vs 29.23% + 14.0; P &lt; 0.01) after 6 mg kg−1 oral methadone and 2.8 times after i.v. (0.35 mg kg−1) administration (91.75% + 4.27 vs 32.45% + 9.0; P &lt; 0.01). The brain:plasma distribution ratio was higher in pretreated animals and AUCbrain (overall brain concentration) was 6 times higher after oral methadone and 4 times higher after i.v. compared with controls, disproportionally increased relative to plasma, implying an active process at the BBB. P-gp, and hence substrate comedication, plays a critical role in the evolution of the methadone analgesic effect and in its brain uptake, independent of the administration route.

Expression and function of p-glycoprotein in normal tissues: effect on pharmacokinetics

ATP-binding cassette (ABC) drug efflux transporters limit intracellular concentration of their substrates by pumping them out of cell through an active, energy dependent mechanism. Several of these proteins have been originally associated with the phenomenon of multidrug resistance; however, later on, they have also been shown to control body disposition of their substrates. P-glycoprotein (Pgp) is the first detected and the best characterized of ABC drug efflux transporters. Apart from tumor cells, its constitutive expression has been reported in a variety of other tissues, such as the intestine, brain, liver, placenta, kidney, and others. Being located on the apical site of the plasma membrane, Pgp can remove a variety of structurally unrelated compounds, including clinically relevant drugs, their metabolites, and conjugates from cells. Driven by energy from ATP, it affects many pharmacokinetic events such as intestinal absorption, brain penetration, transplacental passage, and hepatobiliary excretion of drugs and their metabolites. It is widely believed that Pgp, together with other ABC drug efflux transporters, plays a crucial role in the host detoxication and protection against xenobiotic substances. On the other hand, the presence of these transporters in normal tissues may prevent pharmacotherapeutic agents from reaching their site of action, thus limiting their therapeutic potential. This chapter focuses on P-glycoprotein, its expression, localization, and function in nontumor tissues and the pharmacological consequences hereof.

Oral cyclosporin A inhibits CD4 T cell P-glycoprotein activity in HIV-infected adults initiating treatment with nucleoside reverse transcriptase inhibitors

PURPOSE

P-glycoprotein limits the tissue penetration of many antiretroviral drugs. The aim of our study was to characterize the effects of the P-glycoprotein substrate cyclosporin A on T cell P-glycoprotein activity in human immunodeficiency virus-infected participants in the AIDS Clinical Trials Group study A5138.

METHODS

We studied P-glycoprotein activity on CD4 and CD8 T cells in 16 participants randomized to receive oral cyclosporin A (n=9) or not (n=7) during initiation antiretroviral therapy (ART) that did not include protease or non-nucleoside reverse transcriptase inhibitors.

RESULTS

CD4 T cell P-glycoprotein activity decreased by a median of 8 percentage points with cyclosporin A/ART (difference between cyclosporin A/ART vs. ART only, P= 0.001). Plasma trough cyclosporin A concentrations correlated with the change in P-glycoprotein activity in several T cell subsets.

CONCLUSIONS

Oral cyclosporin A can inhibit peripheral blood CD4 T cell P-glycoprotein activity. Targeted P-glycoprotein inhibition may enhance the delivery of ART to T cells.