Control of Dissolution and Supersaturation/Precipitation of Poorly Water-Soluble Drugs from Cocrystals Based on Solubility Products: A Case Study with a Ketoconazole Cocrystal.

This study demonstrates in vitro and in vivo control of cocrystal dissolution with drug supersaturation/precipitation based on the solubility product of a cocrystal. As a cocrystal model, KTZ-4ABA (ketoconazole, KTZ, a poorly water-soluble drug cocrystal, with 4-aminobenzoic acid, 4ABA, a coformer) was used. The presence of 4ABA in the dissolution media dramatically reduced the dissolution rate of KTZ-4ABA and regulated the supersaturation/precipitation of KTZ, supported by the solubility product of KTZ-4ABA. In the in vitro dissolution study, the combined solid form of KTZ-4ABA and a ten-fold amount of 4ABA significantly lowered the degree of KTZ supersaturation without precipitation and further cocrystal dissolution. To confirm cocrystal dissolution control in the gastrointestinal tract with the same composition as the in vitro study, an in vivo oral administration study with rats was conducted. When KTZ was coadministered to rats in the cocrystal form, an excess of 4ABA coadministered with KTZ-4ABA in the solid form reduced the maximum plasma KTZ concentration (Cmax), prolonged the time to reach the Cmax, but did not influence the area under the plasma concentration-time curve. These results demonstrate that both in vitro and in vivo cocrystal dissolution can be regulated by adding an appropriate amount of coformer based on the solubility product, which can be one of the promising strategies for the oral use of cocrystal formulations.

Development of Magnetocardiograph without Magnetically Shielded Room Using High-Detectivity TMR Sensors.

A magnetocardiograph that enables the clear observation of heart magnetic field mappings without magnetically shielded rooms at room temperatures has been successfully manufactured. Compared to widespread electrocardiographs, magnetocardiographs commonly have a higher spatial resolution, which is expected to lead to early diagnoses of ischemic heart disease and high diagnostic accuracy of ventricular arrhythmia, which involves the risk of sudden death. However, as the conventional superconducting quantum interference device (SQUID) magnetocardiographs require large magnetically shielded rooms and huge running costs to cool the SQUID sensors, magnetocardiography is still unfamiliar technology. Here, in order to achieve the heart field detectivity of 1.0 pT without magnetically shielded rooms and enough magnetocardiography accuracy, we aimed to improve the detectivity of tunneling magnetoresistance (TMR) sensors and to decrease the environmental and sensor noises with a mathematical algorithm. The magnetic detectivity of the TMR sensors was confirmed to be 14.1 pTrms on average in the frequency band between 0.2 and 100 Hz in uncooled states, thanks to the original multilayer structure and the innovative pattern of free layers. By constructing a sensor array using 288 TMR sensors and applying the mathematical magnetic shield technology of signal space separation (SSS), we confirmed that SSS reduces the environmental magnetic noise by -73 dB, which overtakes the general triple magnetically shielded rooms. Moreover, applying digital processing that combined the signal average of heart magnetic fields for one minute and the projection operation, we succeeded in reducing the sensor noise by about -23 dB. The heart magnetic field resolution measured on a subject in a laboratory in an office building was 0.99 pTrms and obtained magnetocardiograms and current arrow maps as clear as the SQUID magnetocardiograph does in the QRS and ST segments. Upon utilizing its superior spatial resolution, this magnetocardiograph has the potential to be an important tool for the early diagnosis of ischemic heart disease and the risk management of sudden death triggered by ventricular arrhythmia.

Liposomal Formulation for Oral Delivery of Cyclosporine A: Usefulness as a Semisolid-Dispersion System.

PURPOSE: This study aims to understand the process and mechanism of oral drug absorption from liposomes and to verify the usefulness of liposomal formulation for poorly soluble drugs. METHODS: Cyclosporine A (CsA) was used as a model drug and entrapped into Dipalmitoylphosphatidylcholine (DPPC) and distearoylphosphatidylcholine (DSPC) liposomes. Molecular state of CsA in the liposomes was analyzed using powder X-ray diffraction (PXRD) and polarized light microscopy (PLM). Release profiles of CsA from liposomes were observed in fasted state simulated intestinal fluid (FaSSIF). Oral absorption of CsA from liposomal formulations were investigated in rats. RESULTS: PXRD and PLM analyses suggested that CsA exists in the lipid layer of liposomes as a molecular dispersed state. Although both liposomes retained CsA stably in the simple buffer, DPPC liposomes quickly released CsA within 10 min in FaSSIF due to the interaction with bile acid. In contrast, effect of bile acid was negligible in DSPC, indicating a high resistivity to membrane perturbation. Oral bioavailability of CsA from liposomal formulations were almost comparable with that from a marketed product (Neoral). However, the absorption profiles were clearly different. CsA was absorbed quickly from DPPC liposomes and Neoral, while sustained absorption profile was observed from DSPC liposomes. Further study in which ritonavir was co-entrapped in the liposomes with CsA showed the higher efficacy of ritonavir to increase oral bioavailability of CsA. CONCLUSION: Liposomes allows the appropriate formulation design for oral delivery of poorly soluble drugs, not only to increase the extent but also to control the rate of absorption.

Discovery of benzyloxyphenyl- and phenethylphenyl-imidazole derivatives as a new class of ante-drug type boosters.

Although cytochrome P450 3A4 (CYP3A4) inhibitors are used as boosters to increase drug absorption, the inhibition of CYP3A4 activity may affect the metabolism of other co-administered drugs. Therefore, we screened for and developed a new class of boosters to improve the oral availability of drugs. We identified benzyloxyphenyl imidazole and phenethylphenyl imidazole derivatives as new types of CYP3A4 inhibitors. Among the compounds synthesized, an ester 5c was found to inhibit CYP activity and the compound 5c was gradually converted to an inactive metabolite 5d under physiological conditions, indicating that the ester 5c may represent a novel ante-drug type booster.

Effects of Ingested Water Volume on Oral Absorption of Fenofibrate, a BCS Class II Drug, from Micronized and Amorphous Solid Dispersion Formulations in Rats.

In this study, we investigated the effects of ingested water volume on the oral absorption of fenofibrate (FEN) with several formulations to confirm the applicability of rats for oral formulation screening. Oral absorption of suspended crystalline FEN was significantly improved by increasing ingested water volume (from 0.5 to 2 mL). FEN absorption improvement by particle size reduction and the linearity in oral absorption by dose escalation suggested that the rate-limiting step of FEN absorption in rats was the dissolution rate, consistent with that in humans. When FEN, as an amorphous solid dispersion (ASD) formulation, was suspended in water followed by immediate administration, oral FEN absorption was significantly higher than when administered in crystalline form and was not influenced by the differences in ingested water volume. Oral absorption of FEN from encapsulated ASD formulation in 1 or 2 mL of water was comparable with that of the suspension form. However, 0.5 mL of water significantly reduced the oral absorption of the solid ASD FEN formulation. These results indicate that to improve the oral absorption of poorly water-soluble drugs when performing a preclinical study with rats, 1 mL of water is the minimum preferable ingested volume to evaluate in vivo formulation performance.

In Vitro-In Vivo Correlation in Cocrystal Dissolution: Consideration of Drug Release Profiles Based on Coformer Dissolution and Absorption Behavior.

This study assessed the in vitro-in vivo correlation in cocrystal dissolution based on the coformer behavior. 4-Aminobenzoic acid (4ABA) was used as a coformer. Cocrystals of poorly water-soluble drugs with 4ABA, ketoconazole cocrystal (KTZ-4ABA), posaconazole cocrystal (PSZ-4ABA), and itraconazole cocrystal (ITZ-4ABA) were used. These three cocrystals generated supersaturated solutions in fasted state simulated intestinal fluid (FaSSIF) in a small-scale, 8 mL dissolution vessel. The time profile of the dissolved amount of 4ABA, an indicator of cocrystal dissolution, was significantly different among the three cocrystals. Under the conditions utilized, half of the KTZ-4ABA cocrystal solid rapidly dissolved within 5 min and the dissolved amount (% of applied amount) of KTZ and 4ABA was the same. Then, even though the residual solid cocrystal gradually dissolved, KTZ precipitated with time. The PSZ-4ABA cocrystal dissolved in a linear fashion with time but the dissolved concentration of PSZ reached a plateau in the supersaturated state and was maintained for at least 2 h. The dissolution rate of ITZ-4ABA was very slow compared to those of the other cocrystals, but a similar tendency was observed between cocrystal dissolution and the dissolved amount of ITZ. The rank order of the cocrystal dissolution rate based on the conformer concentration was KTZ-4ABA > PSZ-4ABA > ITZ-4ABA. Furthermore, cocrystallization of the three drugs with 4ABA significantly enhanced the oral drug absorption in rats. The rank order of the in vivo cocrystal dissolution rate by a deconvolution analysis with the plasma concentration-time profile of 4ABA was KTZ-4ABA > PSZ-4ABA > ITZ-4ABA, which corresponded well with the in vitro dissolution profiles of the cocrystals. These results indicate that analysis of cocrystal dissolution based on the coformer behavior may be useful to evaluate the in vitro and in vivo cocrystal dissolution.

Maximizing the Oral Bioavailability of Poorly Water-Soluble Drugs Using Novel Oil-Like Materials in Lipid-Based Formulations.

Lipid-based formulations, such as self-microemulsifying drug-delivery systems (SMEDDSs), are promising tools for the oral delivery of poorly water-soluble drugs. However, failure to maintain adequate aqueous solubility after coming into contact with gastrointestinal fluids is a major drawback. In this study, we examined the use of a novel cinnamic acid-derived oil-like material (CAOM) that binds drugs with a high affinity through π-π stacking and hydrophobic interactions, as an oil core in a SMEDDS for the oral delivery of fenofibrate in rats. The use of the CAOM in the SMEDDS resulted in an unprecedented enhancement in fenofibrate bioavailability, which exceeded the bioavailability values obtained using SMEDDSs based on corn oil, a conventional triglyceride oil, or Labrasol, an enhancer of intestinal permeation. Further characterization revealed that the CAOM SMEDDS does not alter the intestinal permeability and has no inhibitory activity on P-glycoprotein-mediated drug efflux. The results reported herein demonstrate the strong potential of CAOM formulations as new solubilizers for the efficient and safe oral delivery of drugs that have limited water solubility.

In Vitro Sensitivity Analysis of the Gastrointestinal Dissolution Profile of Weakly Basic Drugs in the Stomach-to-Intestine Fluid Changing System: Explanation for Variable Plasma Exposure after Oral Administration.

An in vitro methodology for simulating the change in the pH and composition of gastrointestinal fluid associated with the transition of orally administered drugs from the stomach to the small intestine was developed (the stomach-to-intestine fluid changing system (the SIFC system)). This system was applied to in vitro sensitivity analysis on the dissolution of weakly basic drugs, and the obtained results were discussed in relation to the intrasubject variability in the plasma exposure in human bioequivalence (BE) study. Three types of protocols were employed (steep pH change: pH 1.6 FaSSGF → pH 6.5 FaSSIF, gradual pH change: pH 1.6 FaSSGF → pH 6.5 FaSSIF, and high gastric pH: pH 4.0 FaSSGF → pH 6.5 FaSSIF). Regardless of the protocols and the forms of drug applied in active pharmaceutical ingredient powder or formulation, dissolution profiles of pioglitazone after fluid shift were similar and the final concentrations in FaSSIF were approximately equal to the saturation solubility in FaSSIF, supporting its small intrasubject variance in human BE study. In contrast, dissolved concentration of terbinafine in the SIFC system became less than half in the high gastric pH protocol than that in other protocols, suggesting the fluctuation of gastric pH as one of the factors of high intrasubject variance of terbinafine in human. Plasma exposure of telmisartan was highly variable especially at the high dose. Although the dissolution of telmisartan in the SIFC system was greatly improved by formulation, it considerably fluctuated during fluid shift especially at the high dose, which corresponds well to in vivo results.

Impact of Dietary Intake of Medium-Chain Triacylglycerides on the Intestinal Absorption of Poorly Permeable Compounds.

The present study sought to demonstrate the effect of dietary intake of medium-chain triacylglycerides (MCTs) on the intestinal absorption of a poorly permeable compound of intermediate molecular weight (FITC-dextran 4000 [FD-4]). As a model of MCTs, C8-C12 fatty acid triacylglyceride (COCONAD ML) was mainly used, and the dose strength of each triglyceride was set with consideration of the dietary ingestion dose (12.5 mg/rat). When FD-4 with MCTs dispersed in fasted state simulated intestinal fluid containing surfactants was administered into the rat jejunum, the intestinal absorption of FD-4 was significantly higher than when administered with a similar solution with or without corn oil (long-chain triglycerides). The effects of pretreatment by MCT lipolysis, inhibition of endogenous lipases, and different dose timings of MCTs and FD-4 on the intestinal absorption of FD-4 indicated that medium-chain fatty acids, such as caprylic acid and capric acid, released from MCTs by lipolysis in the small intestine significantly enhanced the intestinal absorption of FD-4, but the effect was transient. In addition, a similar effect was observed when MCTs were dispersed in soymilk, although large interindividual variation was detected. These findings suggested that dietary intake of MCTs might affect the intestinal absorption of poorly permeable compounds.

Advantage of the Dissolution/Permeation System for Estimating Oral Absorption of Drug Candidates in the Drug Discovery Stage.

In order to increase the success rate in the development of oral drugs, an in vitro method, which can accurately estimate human oral absorption of a large variety of compounds from solid formulations, is required in the drug discovery stage. A dissolution/permeation (D/P) system is an in vitro system that simultaneously evaluates dissolution and permeation processes of drugs administered orally. In this study, we have investigated the advantages of a D/P system for use in the provisional estimation of human oral absorption of a drug (absorbed fraction, Fa) by applying it in its solid state. The D/P system mounted with a Madin-Darby canine kidney (MDCK) II cell monolayer was used to simultaneously evaluate the dissolved and the permeated amounts (% of dose) of 48 marketed drugs. Slightly modified, fasted-state simulated intestinal fluid (FaSSIFmod, 8 mL) was used as the apical medium of the D/P system. Each test drug was applied to the apical side of the D/P system as a suspension at one-hundredth of the clinical dose. The apparent permeability coefficient across the MDCK II cell monolayer was estimated in a buffer solution (pH 6.5). The octanol/water distribution coefficient (Log D) was measured at pH 6.5 by a flask shaking method. Transport medium (TM, pH 6.5), a buffer solution removing lecithin and taurocholate from FaSSIFmod, was used to determine the solubility at 24 h after applying drugs. The solubility in TM was used as a free drug concentration in FaSSIFmod. A good correlation was obtained between observed human Fa and the permeated amount in the D/P system. When the sigmoidal curve was obtained by the curve fitting to the data, the determination coefficient was R(2) = 0.79 and the 95% interval of the predicted Fa values was about ±24% for all drugs tested in the present study. For comparison, the permeated amount was calculated by multiplying the permeability of each drug (in vitro Papp) by the solubility in FaSSIFmod. However, the calculated permeated amount showed a lower correlation with the observed human Fa compared to the observed permeated amount in the D/P system. The ratio of the observed permeated amount to the calculated permeated amount was in inverse proportion to the ratio of solubility in FaSSIFmod to solubility in TM. This finding suggests the necessity of determining the free fraction of the dissolved drug in the gastrointestinal (GI) tract when calculating the human Fa. In the case of the D/P system, since applied drugs dissolved in FaSSIFmod first, and then only the free fraction permeated the membrane, an accurate estimation of the human Fa was possible from only the observed permeated amount. This in vitro system is expected to contribute to the selection of better compounds for oral use during the lead- and formulation-optimization processes in the drug discovery stage.

Systematic approach to optimize a pretreatment method for ultrasensitive liquid chromatography with tandem mass spectrometry analysis of multiple target compounds in biological samples.

In current approaches for new drug development, highly sensitive and robust analytical methods for the determination of test compounds in biological samples are essential. These analytical methods should be optimized for every target compound. However, for biological samples that contain multiple compounds as new drug candidates obtained by cassette dosing tests, it would be preferable to develop a single method that allows the determination of all compounds at once. This study aims to establish a systematic approach that enables a selection of the most appropriate pretreatment method for multiple target compounds without the use of their chemical information. We investigated the retention times of 27 known compounds under different mobile phase conditions and determined the required pretreatment of human plasma samples using several solid-phase and liquid-liquid extractions. From the relationship between retention time and recovery in a principal component analysis, appropriate pretreatments were categorized into several types. Based on the category, we have optimized a pretreatment method for the identification of three calcium channel blockers in human plasma. Plasma concentrations of these drugs in a cassette-dose clinical study at microdose level were successfully determined with a lower limit of quantitation of 0.2 pg/mL for diltiazem, 1 pg/mL for nicardipine, and 2 pg/mL for nifedipine.

Analysis of Intra- and Intersubject Variability in Oral Drug Absorption in Human Bioequivalence Studies of 113 Generic Products.

In this study, the data of 113 human bioequivalence (BE) studies of immediate release (IR) formulations of 74 active pharmaceutical ingredients (APIs) conducted at Sawai Pharmaceutical Co., Ltd., was analyzed to understand the factors affecting intra- and intersubject variabilities in oral drug absorption. The ANOVA CV (%) calculated from area under the time-concentration curve (AUC) in each BE study was used as an index of intrasubject variability (Vintra), and the relative standard deviation (%) in AUC was used as that of intersubject variability (Vinter). Although no significant correlation was observed between Vintra and Vinter of all drugs, Vintra of class 3 drugs was found to increase in association with a decrease in drug permeability (P(eff)). Since the absorption of class 3 drugs was rate-limited by the permeability, it was suggested that, for such drugs, the low P(eff) might be a risk factor to cause a large intrasubject variability. To consider the impact of poor water solubility on the variability in BE study, a parameter of P(eff)/Do (Do; dose number) was defined to discriminate the solubility-limited and dissolution-rate-limited absorption of class 2 drugs. It was found that the class 2 drugs with a solubility-limited absorption (P(eff)/Do < 0.149 × 10(-4) cm/s) showed high intrasubject variability. Furthermore, as a reason for high intra- or intersubject variability in AUC for class 1 drugs, effects of drug metabolizing enzymes were investigated. It was demonstrated that intrasubject variability was high for drugs metabolized by CYP3A4 while intersubject variability was high for drugs metabolized by CYP2D6. For CYP3A4 substrate drugs, the Km value showed the significant relation with Vintra, indicating that the affinity to the enzyme can be a parameter to predict the risk of high intrasubject variability. In conclusion, by analyzing the in house data of human BE study, low permeability, solubility-limited absorption, and high affinity to CYP3A4 are identified as risk factors for high intrasubject variability in oral drug absorption. This information is of importance to design the human BE study for oral drug products containing APIs with a risk of large intrasubject variability in oral absorption.

Interaction with Mixed Micelles in the Intestine Attenuates the Permeation Enhancing Potential of Alkyl-Maltosides.

The purpose of the present study was to investigate the interaction of intestinal permeation enhancers with lipid and surfactant components present in the milieu of the small intestine. Maltosides of different chain lengths (decyl-, dodecyl-, and tetradecyl-maltoside; DM, DDM, TDM, respectively) were used as examples of nonionic, surfactant-like permeation enhancers, and their effect on the permeation of FD4 across Caco-2 monolayers was monitored. To mimic the environment of the small intestine, modified versions of fasted and fed state simulated intestinal fluid (FaSSIFmod, FeSSIFmod6.5, respectively) were used in addition to standard transport media (TM). Compared to the buffer control, 0.5 mM DDM led to a 200-fold permeation enhancement of FD4 in TM. However, this was dramatically decreased in FaSSIFmod, where a concentration of 5 mM DDM was necessary in order to elicit a moderate, 4-fold, permeation enhancement. Its capacity to promote permeation was diminished further when FeSSIFmod6.5 was employed. Even when cells were exposed to a concentration of 5 mM, no significant permeation enhancement of FD4 was observed. Analogous effects were observed in the case of DM and TDM, with slight deviations on account of differences in their critical micelle concentration (CMC). This observation was corroborated by calculating the amount of maltoside monomer versus micellar bound maltoside in FaSSIFmod and FeSSIFmod6.5, which demonstrated a reduced amount of free monomer in these fluids. To evaluate the in vivo significance of our findings, DDM solutions in TM, FaSSIFmod, and FeSSIFmod6.5 were used for closed intestinal loop studies in rats. Consistent with the results found in in vitro permeation studies, these investigations illustrated the overwhelming impact of sodium taurocholate/lecithin micelles on the permeation enhancing effect of DDM. While DDM led to a 20-fold increase in FD4 bioavailability when it was applied in TM, no significant permeation enhancement was seen in FaSSIFmod/FeSSIFmod6.5. Collectively, these investigations highlight the importance of using biorelevant media when evaluating the potency of permeation enhancers. In doing so, this ensures improved correlations between in vitro and in vivo studies and thus enables an early and more accurate assessment of promising permeation enhancers.

In vitro-in vivo correlation of the effect of supersaturation on the intestinal absorption of BCS Class 2 drugs.

The aim of this study was to establish an in vitro method for evaluating the effect of supersaturation on oral absorption of poorly water-soluble drugs in vivo. Albendazole, dipyridamole, gefitinib, and ketoconazole were used as model drugs. Supersaturation of each drug was induced by diluting its stock solution by fasted state simulated intestinal fluid (FaSSIF) (solvent-shift method), then dissolution and precipitation profile of the drug was observed in vitro. The crystalline form of the precipitate was checked by differential scanning calorimetry (DSC). For comparison, control suspension was prepared by suspending a drug powder directly into FaSSIF (powder-suspending method). In vivo intestinal absorption of the drug was observed in rats by determined the plasma concentration after intraduodenal administration of drug suspensions. For all drugs, suspensions prepared by solvent-shift method showed significantly higher dissolved concentration in vitro than that prepared by powder-suspending method, clearly indicated the induction of supersaturation. DSC analysis revealed that crystalline form of the precipitate profoundly affects the extent and the duration of supersaturation. A rat in vivo study confirmed that the supersaturation of these drugs increased the fraction absorbed from the intestine, which corresponded well to the in vitro dissolution and precipitation profile of drugs except for ketoconazole. For ketoconazole, an in vivo absorption study was performed in rats pretreated with 1-aminobenzotriazole, a potent inhibitor of CYP mediated metabolism. CYP inhibition study suggested that the high luminal concentration of ketoconazole caused by supersaturation saturated the metabolic enzymes and further increased the systemic exposure of the absorbed drug. The additional effects of supersaturation on the absorption of ketoconazole are consistent with previous studies in humans under differing gastric pH conditions. In conclusion, effects of supersaturation on the intestinal absorption of poorly water-soluble drugs could be predicted from in vitro dissolution and a precipitation study. However if supersaturation affects the pharmacokinetic profiles of drugs, such as a first-pass metabolism, a combination with in vivo study should be required to evaluate its impact on oral bioavailability.

Near-infrared imaging of in vivo performance of orally administered solid forms to rats: Feasibility study with indocyanine green.

This study demonstrates the applicability of near-infrared (NIR) imaging to evaluating in vivo oral formulation performance. As a NIR probe and model drug, indocyanine green (ICG) and acetaminophen (ACE) were selected, respectively. The fluorescence intensity of ICG greatly increased upon dissolution, with the dissolved ICG passing through the gastrointestinal tract over time. Both compounds (0.05 mg of ICG and 0.5 mg of ACE) were encapsulated in gelatin and hydroxypropyl methylcellulose (HPMC) capsules in the solid form. In vitro, the HPMC capsules showed a disintegration lag time, a feature that was not observed for the gelatin capsules. After oral administration of each capsule to rats, blood samples were collected, followed by fluorescent imaging of the abdominal region. At 0.25 h after HPMC capsule administration, the fluorescence area and intensity were significantly small and relatively weak compared to that of the gelatin capsule. These tendencies resulted from the difference in capsule disintegration times, leading to a change in gastric emptying, which corresponded well with the initial time profile of the plasma concentration of ACE. These results indicate that possibility of NIR imaging with ICG to evaluate in vivo performance of orally administered formulations.

In vitro demonstration of antedrug mechanism of a pharmacokinetic booster to improve CYP3A4 substrates by CYP3A4-mediated metabolism inhibition.

We previously reported novel benzyl-ether derivatives with an imidazole ring and a hydroxyl group (A-01) or carboxyl group (B-01) and esters (2 esters of A-01, and 7 esters of B-01) as pharmacokinetics (PK) boosters. This study demonstrates how these ester compounds embody the concept of a safe pharmacokinetic booster, with potent and transient inhibition of CYP3A4-mediated drug metabolism. As a model CYP3A4 substrate and CYP3A4 enzyme, midazolam (MDZ) and rat liver microsomes were used. A-01 inhibited MDZ metabolism significantly, while B-01 induced only slight inhibition. Although rat liver microsomes hydrolyzed the ester compounds over time, several ester compounds strongly inhibited MDZ metabolism. Due to the significant activity of A-01, A-01 esters affected MDZ metabolism, irrespective of hydrolysis state. Time-dependent inhibition evaluation indicated that the B-01 ester inhibition is not mechanism-based, as hydrolysis eliminated MDZ metabolism inhibition. We report that the B-01 esters significantly inhibit CYP3A4-mediated drug metabolism, and upon hydrolysis this property is eliminated. In conclusion, B-01 ester compounds may be safe PK boosters with antedrug characteristics.

Multifunctional nanobeacon for imaging Thomsen-Friedenreich antigen-associated colorectal cancer.

This research aimed to validate the specificity of the newly developed nanobeacon for imaging the Thomsen-Friedenreich (TF) antigen, a potential biomarker of colorectal cancer. The imaging agent is comprised of a submicron-sized polystyrene nanosphere encapsulated with a Coumarin 6 dye. The surface of the nanosphere was modified with peanut agglutinin (PNA) and poly(N-vinylacetamide (PNVA) moieties. The former binds to Gal-ß(1-3)GalNAc with high affinity while the latter enhances the specificity of PNA for the carbohydrates. The specificity of the nanobeacon was evaluated in human colorectal cancer cells and specimens, and the data were compared with immunohistochemical staining and flow cytometric analysis. Additionally, distribution of the nanobeacon in vivo was assessed using an "intestinal loop" mouse model. Quantitative analysis of the data indicated that approximately 2 µg of PNA were detected for each milligram of the nanobeacon. The nanobeacon specifically reported colorectal tumors by recognizing the tumor-specific antigen through the surface-immobilized PNA. Removal of TF from human colorectal cancer cells and tissues resulted in a loss of fluorescence signal, which suggests the specificity of the probe. Most importantly, the probe was not absorbed systematically in the large intestine upon topical application. As a result, no registered toxicity was associated with the probe. These data demonstrate the potential use of this novel nanobeacon for imaging the TF antigen as a biomarker for the early detection and prediction of the progression of colorectal cancer at the molecular level.

Dynamic analysis of fluid distribution in the gastrointestinal tract in rats: positron emission tomography imaging after oral administration of nonabsorbable marker, [(18)F]Deoxyfluoropoly(ethylene glycol).

To develop potent drugs for oral use, information on their pharmacokinetic (PK) properties after oral administration is of great importance. We have recently reported the utility of positron emission tomography (PET) for the analysis of gastrointestinal (GI) absorption of radiolabeled compounds. In this study, PET image analysis was performed in rats using a novel PET probe, [(18)F]deoxyfluoropoly(ethylene glycol)s, with an average molecular weight of 2 kDa ([(18)F]FPEG), as a nonabsorbable marker to elaborate the GI physiology in more detail, such as segmental transition of the administered water, and fluid volume and distribution in the intestine. After oral administration of [(18)F]FPEG solution to rats, a 90 min PET scan with continuous blood sampling was performed, and then the disposition of radioactivity in each part of GI tract was investigated. From blood PK analysis, it was confirmed that the bioavailability of [(18)F]FPEG was quite low in rats. PET image analysis showed that the radioactivity after oral administration of [(18)F]FPEG solution rapidly passed through the stomach, spread into the proximal small intestine, and then transited toward the distal region of the small intestine without decreasing the radioactivity during GI transition. Radiometabolite analysis revealed that the radioactivity in intestinal mucosal tissues, blood, and urine was mainly derived from unchanged [(18)F]FPEG. It was also found that the volume of interest (VOI) after oral administration of the radiotracer enables an understanding of the time-dependent manner of effective fluid volume changes in the stomach and the small intestine. In addition, the rate constant of the intestinal transition of radioactivity in each intestinal segment was calculated by kinetic model analysis, which revealed that PET analysis enables us to determine the GI transit from the same individuals and that it is applicable to determine site-specific intestinal absorption. In conclusion, we demonstrated the high potency of PET imaging technique to elucidate the distribution of orally administered solution in the GI tract in vivo.

Measurement of drug concentration in the stomach after intragastric administration of drug solution to healthy volunteers: analysis of intragastric fluid dynamics and drug absorption.

PURPOSE: To evaluate the time-profile of intragastric fluid volume in humans after intragastric administration of drug solution. METHODS: Eight healthy volunteers were intragastrically administered 150 mL of drug solution containing atenolol (non-absorbable marker) and salicylic acid, then, aliquots of gastric fluid (ca. 2 mL) were sampled for 2 h through the catheter. Rate constants for secretion and emptying of the fluid were obtained by fitting the time-course of atenolol concentration to the simple gastric fluid transit model. Absorption of salicylic acid from the stomach was estimated by comparing its gastric concentration with that of atenolol. RESULTS: Kinetic analysis of atenolol concentration in the stomach indicated a rapid emptying of the fluid with an average half-life of 4.2 min. Steady-state intragastric fluid volume in 8 volunteers was estimated as 4-133 mL with an average of 42 mL. Intragastric concentration (normalized by dose) of salicylic acid was always lower than that of atenolol, showing approximately 40% of salicylic acid was absorbed from the stomach before emptying to the intestine. CONCLUSIONS: This study provided valuable information on intragastric fluid dynamics and gastric drug absorption in humans to establish a better in vitro-in vivo correlation in oral drug absorption.