RESUMEN
Fluphenazine (FPZ) decanoate, an ester-type prodrug formulated as a long-acting injection (LAI), is used in the treatment of schizophrenia. FPZ enanthate was also developed as an LAI formulation, but is no longer in use clinically because of the short elimination half-life of FPZ, the parent drug, after intramuscular injection. In the present study, the hydrolysis of FPZ prodrugs was evaluated in human plasma and liver to clarify the reason for this difference in elimination half-lives. FPZ prodrugs were hydrolyzed in human plasma and liver microsomes. The rate of hydrolysis of FPZ enanthate in human plasma and liver microsomes was 15-fold and 6-fold, respectively, faster than that of FPZ decanoate. Butyrylcholinesterase (BChE) and human serum albumin (HSA) present in human plasma, and two carboxylesterase (CES) isozymes, hCE1 and hCE2, expressed in ubiquitous organs including liver, were mainly responsible for the hydrolysis of FPZ prodrugs. FPZ prodrugs may not be bioconverted in human skeletal muscle at the injection site because of lack of expression of BChE and CESs in muscle. Interestingly, although FPZ was a poor substrate for human P-glycoprotein, FPZ caproate was a good substrate. In conclusion, it is suggested that the shorter elimination half-life of FPZ following administration of FPZ enanthate compared with FPZ decanoate can be attributed to the more rapid hydrolysis of FPZ enanthate by BChE, HSA and CESs.
Asunto(s)
Flufenazina , Profármacos , Humanos , Flufenazina/uso terapéutico , Profármacos/metabolismo , Inyecciones Intramusculares , Butirilcolinesterasa , Decanoatos , HeptanoatosRESUMEN
BACKGROUND/AIM: Oral 5-fluorouracil (5-FU)-based prodrugs, used in cancer chemotherapeutic regimens, exhibit large inter- and intra-patient variability in plasma 5-FU concentrations, contributing to treatment failure. Although dosage determination criteria according to plasma drug concentrations are required, the relationship between pharmacokinetics and drug response after multiple oral 5-FU derivative administrations remain unknown. MATERIALS AND METHODS: We evaluated the pharmacokinetics and pharmacodynamics/toxicodynamics of uracil-tegafur (UFT) after multiple administrations in colorectal cancer (CRC) model rats, and applied a pharmacometric approach to describe the time-course alterations of plasma 5-FU concentrations and tumor shrinkage. CRC was induced in rats using 1,2-dimethylhydrazine and dextran sulfate sodium. UFT (30 mg/kg as tegafur) was administered to CRC rats for 14 days. RESULTS: Plasma 5-FU exposure levels increased with the dosing time, and large variations were observed in tumor 5-FU concentrations (32.0-125.8% with coefficient of variation). Although severe hematological toxicities were not observed, a weak correlation was observed between blood platelet count and the plasma 5-FU concentration (r=0.439, p=0.176). A simple pharmacokinetic-pharmacodynamic model was developed comprising of a small number of parameters and successfully describing plasma 5-FU levels and tumor shrinkage after multiple UFT administrations. CONCLUSION: A pharmacometric model approach can help establish the dose-determination criteria based on plasma 5-FU concentration of UFT-based regimens, and contribute to improvement of clinical outcomes.
Asunto(s)
Neoplasias Colorrectales , Tegafur , Animales , Ratas , Uracilo/farmacología , Fluorouracilo/farmacología , Administración Oral , Neoplasias Colorrectales/tratamiento farmacológicoRESUMEN
Development of prodrugs is a useful strategy to overcome some disadvantages of candidate drugs. Recently, we established a systematic approach to selecting appropriate prodrugs, and validated the utility of this approach using oseltamivir analogues. In this study, the utility of the approach was further examined using candesartan cilexetil and 20 kinds of its analogues having various types of side chain as model compounds. Log D values of analogues (2.5 to 4.7) were higher than that of candesartan (1.0), their active metabolite, and the results were reasonable for the purpose of improving permeability of candesartan. The analogues tended to be more soluble in artificial intestinal fluids than in artificial gastric fluid, owing to their acidic physicochemical characteristics. Their membrane permeabilities were not correlated with log D values, which can be attributed to the metabolism in Caco-2 cells used in this system. In human hepatocytes and enterocytes, 11 out of the 20 analogues were immediately hydrolyzed to candesartan, and species differences were observed in the hydrolysis efficiency. This study confirmed the utility of the systematic approach for selection of appropriate prodrugs that could be proceeded to in vivo pharmacokinetics study, with selection of suitable experimental animals.
Asunto(s)
Profármacos , Animales , Humanos , Profármacos/farmacocinética , Ésteres , Células CACO-2 , IntestinosRESUMEN
Fosamprenavir is a phosphate ester prodrug that, upon dissolution, is cleaved to the poorly soluble yet readily absorbable parent drug amprenavir. In this study, a novel cell-free in vitro setup with quasi-continuous monitoring of the dynamic dissolution/bio-conversion/permeation of fosamprenavir was designed and tested. It consists of side-by-side diffusion cells, where the donor and acceptor compartments are separated by the biomimetic barrier PermeaPad®, and sampling from the donor compartment is accomplished via a microdialysis probe. Externally added bovine alkaline phosphatase induced bioconversion in the donor compartment. Microdialysis sampling allowed to follow the enzymatic conversion of fosamprenavir to amprenavir by the bovine alkaline phosphatase in an (almost) real-time manner eliminating the need to remove or inactivate the enzyme. Biomimetic conversion rates in the setup were established by adding appropriate amounts of the alkaline phosphatase. A substantial (6.5-fold) and persistent supersaturation of amprenavir was observed due to bioconversion at lower (500 µM) concentrations, resulting in a substantially increased flux across the biomimetic barrier, nicely reflecting the situation in vivo. At conditions with an almost 10-fold higher dose than the usual human dose, some replicates showed premature precipitation and collapse of supersaturation, while others did not. In conclusion, the proposed novel tool appears very promising in gaining an in-depth mechanistic understanding of the bioconversion/permeation interplay, including transient supersaturation of phosphate-ester prodrugs like fosamprenavir.
Asunto(s)
Profármacos , Animales , Bovinos , Humanos , Fosfatasa Alcalina , Biomimética , Ésteres , Microdiálisis , Organofosfatos , Fosfatos , Profármacos/metabolismo , SolubilidadRESUMEN
Drug delivery to the lymphatic system is gaining increasing attention, particularly in fields such as immunotherapy where drug access to lymphocytes is central to activity. We have previously described a prodrug strategy that facilitates the lymphatic delivery of a model immunomodulator, mycophenolic acid (MPA) via incorporation into intestinal triglyceride transport pathways. The current study explored a series of structurally related glyceride and phospholipid mimetic prodrugs of MPA in an attempt to enhance lymph targeting and to better elucidate the design criteria for lipid mimetic prodrugs. MPA was conjugated to a glyceride or phospholipid backbone at various positions using different spacers employing ester, ether, carbonate and amide bonds. Patterns of prodrug hydrolysis were evaluated in rat digestive fluid, and lymphatic transport and plasma pharmacokinetics were assessed in lymph duct cannulated rats. Prodrugs with different spacers between MPA and the glyceride backbone resulted in up to 70-fold differences in gastrointestinal stability. MPA conjugation at the 2 position of the glyceride backbone and via an ester bond were most effective in promoting lymphatic transport. Phospholipid prodrug derivatives, or glyceride derivatives with MPA attached at the 1 position or when linked via ether, carbonate or amide bonds were poorly incorporated into lymphatic transport pathways.
Asunto(s)
Profármacos , Animales , Sistemas de Liberación de Medicamentos , Glicéridos , Linfa , Fosfolípidos , RatasRESUMEN
Prodrug development is a common approach in drug development. In a recent study, we established a systematic strategy for selecting prodrugs with improved membrane permeability or solubility based on log D value, solubility in artificial intestinal fluids, membrane permeability, and metabolic instability. The purpose of this study was to evaluate the utility of this strategy using oseltamivir and 23 kinds of oseltamivir analogues having various types of side chain as well as their active metabolite, oseltamivir acid. Log D values of oseltamivir and analogues (2.0 to 4.9) were higher than that of oseltamivir acid (0.7), supporting the previous development of oseltamivir to improve permeability of oseltamivir acid. Solubilities of analogues in artificial intestinal fluids were over 80%, except the compound with the highest lipophilicity. Positive correlation was observed between membrane permeability and log D values of analogues. In metabolic profiles, species differences in the hydrolysis efficiency were observed depending on analogues. Using our strategy, it was demonstrated that oseltamivir and some analogues are appropriate prodrugs that could be advanced to in vivo pharmacokinetic studies, with selection of suitable animals. This study confirmed the utility of our strategy for narrowing down of candidate compounds to proceed into in vivo study.
Asunto(s)
Oseltamivir , Profármacos , Animales , Hidrólisis , Permeabilidad , SolubilidadRESUMEN
Circadian fluctuations in the plasma concentration of 5-fluorouracil impede the accurate estimation of target therapeutic concentrations in the long-term infusion or oral 5-fluorouracil-based prodrug regimen. We evaluated the circadian patterns of plasma 5-fluorouracil concentrations in rats using population pharmacokinetic model. Rats were divided into 2 groups, and a continuous infusion (50 mg/m2/h) for 48 h was initiated with or without a bolus injection of 60 mg/kg 5-fluorouracil. In the group not administered a loading dose, significant circadian variation of plasma 5-fluorouracil concentration was observed. In contrast, in the loading dose group, this circadian variation disappeared. Additionally, decreased hepatic dihydropyrimidine dehydrogenase activity was observed. Population model analysis revealed that the concentrations of 5-fluorouracil followed a 24-h cosine circadian curve, representing an overall 1.8-fold increase from a nadir to a peak, with a relative amplitude (% of mesor) of 28%. The circadian 5-fluorouracil clearance pattern in the infusion-regimen was consistent with previously reported pattern for capecitabine and uracil-tegafur. In the recently modified regimen omitting the bolus injection of 5-fluorouracil, the circadian variations should be considered for blood sampling time points in therapeutic drug monitoring. The chronomodulated chemotherapy using oral prodrug administration could be established based on accumulating evidence in the infusion-regimen.
Asunto(s)
Profármacos , Administración Oral , Animales , Fluorouracilo , Ratas , Tegafur , UraciloRESUMEN
To increase the success rate in development of prodrugs, we sought to establish a systematic in vitro method to appropriately select candidate prodrugs. Physicochemical/biopharmaceutical properties of 21 commercially available prodrugs (16 with improved membrane permeability of pharmacologically active metabolites and 5 with improved solubility) and their active metabolites were characterized in terms of solubility in artificial intestinal fluids and membrane permeability using Caco-2 cells. Their in vitro metabolic profiles were also evaluated, using human and animal enterocytes, hepatocytes, and sera. Log D values of prodrugs with improved membrane permeability were higher than those of their active metabolites, whereas those of prodrugs with improved aqueous solubility were lower than those of active metabolites. The prodrugs with improved aqueous solubility were highly soluble in artificial intestinal fluids. All prodrugs were efficiently converted to active metabolites with human matrices, whereas some were not with dog or monkey matrices. This study demonstrated that physicochemical/biopharmaceutical properties could be useful information to facilitate design of prodrugs and for selection of candidate prodrugs. Moreover, the in vitro evaluation of conversion efficiency to active metabolites would be helpful for selecting ideal prodrugs as well as appropriate animals for in vivo PK studies.
Asunto(s)
Profármacos , Animales , Células CACO-2 , Permeabilidad de la Membrana Celular , Perros , Humanos , Absorción Intestinal , Intestinos , SolubilidadRESUMEN
Hydrogen sulfide (H2S) has been recently recognized as a gaseous signaling molecule that controls various biological activities. In the present study, we developed sulfo-albumin as a macromolecular H2S prodrug for therapeutic use, in which multisulfide groups (source of H2S) were conjugated with bovine serum albumin through a covalent linkage. In an in vitro study on H2S release in phosphate buffered saline solution, we found that H2S was released from sulfo-albumin in the presence of 5-mM glutathione but not in its absence. Furthermore, sulfo-albumin was taken up by RAW 264.7 cells, and it released H2S in cells but not in plasma. These results indicate that H2S can be selectively released from sulfo-albumin in cells. 111In-labeled sulfo-albumin predominantly accumulated in the liver, dependent upon the number of sulfide groups, after intravenous injection in mice. In a carbon tetrachloride-induced acute liver injury mouse model, sulfo-albumin significantly suppressed the increase in plasma aspartate aminotransferase and alanine aminotransferase activities, which are indicators of hepatocyte injury, after intravenous injection. These findings indicate that sulfo-albumin is a promising compound for the treatment of hepatic injuries.