蛋白多肽类降糖药物口服递送载体的研究现状与临床应用进展

糖尿病是一种常见的慢性疾病,严重影响着人类健康和生活质量。与皮下注射相比,口服递送蛋白多肽类降糖药物如胰岛素是更理想的糖尿病治疗方案。然而,体内存在着多重生理屏障,极大地限制了药物的口服吸收。近年来,基于载体材料和制剂技术的快速发展,多种口服药物递送载体被开发出来,有望解决上述问题。总结口服药物载体在体内面临的共性递药屏障,重点阐述限制蛋白多肽类降糖药物口服递送的特殊屏障;进一步综述目前相关领域的研究现状以及临床应用进展,并对其发展进行展望,以期为蛋白多肽类降糖药物口服递送载体的理性化设计提供新的视角和思路。     

Current Status and Future Prospects of Transdermal Drug Delivery

Pharmaceutical Research -     

Controlled Release Technologies: Current Status and Future Prospects

Pharmaceutical Research -     

口服多肽和蛋白质药物的研究进展

多肽和蛋白质药物由于其特异性高、安全性高的特点已广泛应用于各种疾病的临床治疗,但其主要给药途径是注射给药,降低了患者的依从性。口服作为一种安全性高、依从性强的给药途径逐渐成为研究焦点,但胃肠道的结构组织和生理功能使得多肽和蛋白质药物口服后生物利用度低、半衰期短。口服后多肽和蛋白质药物的吸收成为此类药物口服给药途径开发的瓶颈,但随着技术的发展,近年来对促进多肽和蛋白质药物口服吸收的研究在临床前和临床试验方面均取得较大进展。综述多肽和蛋白质药物口服吸收途径、影响因素、提高多肽和蛋白质药物口服吸收的方法以及相关临床试验的研究进展。     

Esterase-Sensitive Cyclic Prodrugs of Peptides: Evaluation of an Acyloxyalkoxy Promoiety in a Model Hexapeptide

Purpose. To evaluate a cyclic acyloxyalkoxycarbamate prodrug of a model hexapeptide (H-Trp-Ala-Gly-Gly-Asp-Ala-OH) as a novel approach to enhance the membrane permeation of the peptide and stabilize it to metabolism. Methods. Conversion to the linear hexapeptide was studied at 37°C in aqueous buffered solutions and in various biological milieus having measurable esterase activities. Transport and metabolism characteristics were assessed using the Caco-2 cell culture model. Results. In buffered solutions the cyclic prodrug degraded chemically to the linear hexapeptide in stoichiometric amounts. Maximum stability was observed between pH 3–4. In 90% human plasma (t _1/2 = 100 ± 4 min) and in homogenates of the rat intestinal mucosa (t _- = 136 ± 4 min) and rat liver (t _- = 65 ± 3 min), the cyclic prodrug disappeared faster than in buffered solution, pH 7.4 (t _- = 206 ± 11 min). Pretreatment of these media with paraoxon significantly decreased the degradation rate of the prodrug. When applied to the apical side of Caco-2 cell monolayers, the cyclic prodrug (t _- = 282 ± 25 min) was significantly more stable than the hexapeptide (t _- = 14 min) and at least 76-fold more able to permeate (P _app = 1.30 ± 0.15 × 10^–7 cm/ s) than the parent peptide (P _app 0.17 × 10^–8 cm/s). Conclusions. Preparation of a cyclic peptide using an acyloxyalkoxy promoiety reduced the lability of the peptide to peptidase metabolism and substantially increased its permeation through biological membranes. In various biological media the parent peptide was released from the prodrug by an apparent esterase-catalyzed reaction, sensitive to paraoxon inhibition.     

Protein and Peptide Drug Delivery: Oral Approaches

Till recent, injections remained the most common means for administering therapeutic proteins and peptides because of their poor oral bioavailability. However, oral route would be preferred to any other route because of its high levels of patient acceptance and long term compliance, which increases the therapeutic value of the drug. Designing and formulating a polypeptide drug delivery through the gastro intestinal tract has been a persistent challenge because of their unfavorable physicochemical properties, which includes enzymatic degradation, poor membrane permeability and large molecular size. The main challenge is to improve the oral bioavailability from less than 1% to at least 30-50%. Consequently, efforts have intensified over the past few decades, where every oral dosage form used for the conventional small molecule drugs has been used to explore oral protein and peptide delivery. Various strategies currently under investigation include chemical modification, formulation vehicles and use of enzyme inhibitors, absorption enhancers and mucoadhesive polymers. This review summarizes different pharmaceutical approaches which overcome various physiological barriers that help to improve oral bioavailability that ultimately achieve formulation goals for oral delivery.     

Esterase-Sensitive Cyclic Prodrugs of Peptides: Evaluation of a Phenylpropionic Acid Promoiety in a Model Hexapeptide

Purpose. To evaluate a cyclic phenylpropionic acid prodrug of a model hexapeptide (H-Trp-Ala-Gly-Gly-Asp-Ala-OH) as a novel approach to enhance the membrane permeation of a peptide and stabilize it to metabolism. Methods. Conversion to the linear hexapeptide was studied at 37°C in HBSS, pH 7.4, and in various biological milieus having measurable esterase activities. Transport and metabolism characteristics were assessed using the Caco-2 cell culture model. Results. In aqueous buffered solution, pH 7.4, the cyclic prodrug degraded quantitatively (t _1/2 = 1795 ± 289 min) to the linear hexapeptide and the lactone. Substantially faster degradation of the cyclic prodrug was observed in 90% human plasma (t _1/2 = 508 ± 24 min), and in homogenates of Caco-2 cells (t _1/2 = 940 ± 13 min), the rat intestinal mucosa (t _1/2 = 1286 ± 32 min), and rat liver (t _1/2 = 840 ± 42 min). Pretreatment of these biological media with paraoxon significantly decreased the degradation rate of the prodrug. When applied to the apical side of Caco-2 cell monolayers, the cyclic prodrug was significantly more stable than the hexapeptide and at least 71-fold more able to permeate (P_app = 1.21 ± 0.12 × 10^–7 cm/s) than was the parent peptide (P_app 0.17 × 10^–8 cm/s). In the presence of 0.1 mM palmitoyl-DL-carnitine, the transport rate of the cyclic prodrug (P_app = 2.19 × 10^–6 cm/s) was 1250-fold greater than that of the linear hexapeptide. Conclusions. Preparation of a cyclic peptide using a phenylpropionic acid promoiety reduced the lability of the peptide to peptidase metabolism and substantially increased its permeation through biological membranes. In various biological media the parent peptide was released from the prodrug by an apparent esterase-catalyzed reaction, sensitive to paraoxon inhibition.     

Design of Virus-Mimicking Polyelectrolyte Complexes for Enhanced Oral Insulin Delivery

The viscous and elastic mucus layer is still an undesirable barrier for oral insulin delivery. To solve the problem, virus-mimicking nanosized polyelectrolyte complex (PEC) was designed and their capacity in enhancing peroral insulin absorption in combination with bifunctional material sodium dodecyl sulfate (SDS) coating was investigated. Inspired by nature, virus-mimicking chitosan (CS)-modified L-Phe derivatives were synthesized to simulate the components of viral envelopes and then PECs between CS-g-N-Phe copolymers and insulin were prepared to achieve both structure and composition simulation of virus envelope. Based on the results from both in vitro and in vivo studies, it was concluded that in vitro mucodiffusion and in vivo hypoglycemic effect were dependent on L-Phe graft ratio, with CS-g-N-Phe_20.2%/insulin PECs presenting 2.0- to 2.2-fold higher relative pharmacological bioavailability than nonmodified CS/insulin PECs. Thereafter, SDS solution was applied as outer layer coating on the surface of virus-mimicking PECs. The coated PECs showed improved enzymatic stability, enhanced transport across mucus layer as well as intestinal epithelium in an SDS concentration–dependent manner, with 0.6% SDS coating presenting the best effect, with further enhanced relative pharmacological bioavailability in healthy rats and prolonged therapeutic effect up to 9 h.     

Safe and Effective Permeation Enhancers for Oral Drug Delivery

PURPOSE: The use of intestinal permeation enhancers to overcome the absorption challenges associated with oral drug delivery has been hampered by the notion that enhancer efficacy is directly linked to toxicity. This study attempts to gain insight into the principles governing the potency and toxicity behavior of enhancers. METHODS: Fifty-one enhancers were selected from 11 chemical categories and their potency and toxicity were analyzed in Caco-2 monolayers at concentrations spanning three orders of magnitude. RESULTS: A small but significant fraction of the 153 enhancer formulations studied demonstrated unexpected but desired behavior, that is, substantial efficacy without marked toxicity. Our results revealed that both chemical category and concentration proved critical in determining the usefulness of many enhancers, and the concept of an enhancer's 'therapeutic window' is discussed. Several of the most promising enhancers identified by the study were tested for their effect on the transport of the marker molecules mannitol and 70 kDa dextran across Caco-2 cells and were capable of increasing permeability more than 10-fold. CONCLUSIONS: The results presented here underscore the potential of chemical permeation enhancers while providing valuable direction as to what classes and concentrations of compounds are of interest when searching for safe and effective additions to oral formulations.     

胰岛素口服制剂的研究进展

综述了近年来国内外关于胰岛素口服剂型的制剂技术发展和生物利用度提高情况，特别对胰岛素纳米微粒，微乳，复乳、脂质体以及结肠定位给药制剂的进展进行了分析。指出目前研究中尚待解决的问题。     

Push-Pull Controlled Drug Release Systems: Effect of Molecular Weight of Polyethylene Oxide on Drug Release

First, an elementary osmotic pump (EOP) with a simple structure was prepared using polyethylene oxide (PEO) and NaCl as an excipient, and the influence of the molecular weight (Mw) of PEO on drug release was investigated. In the dissolution test of EOP, it was observed that the gelated core tablet was pushed out through the orifice. The dissolution profile of EOP was sigmoidal, and despite the short time, a zero-order release region was observed. The gel swelling rate in the zero-order region was independent of the Mw of PEO. It was also found that higher the Mw of PEO, the larger the saturated swelling amount. Next, a push-pull pump (PPP) with almost identical formulation to that of EOP was prepared, and its drug release characteristics were investigated. PPPs were prepared by varying the combination of Mws of PEO in both layers, and their dissolution profiles were compared. It was found that PPP using a low-Mw PEO for the drug layer and PEO with a high-Mw in the push layer showed the longest dissolution profile of the linear region. The obtained findings suggested that the properties of PEO and its hydrogel play a crucial role in the drug release of PPP.     

口服脉冲控释给药系统的释药机制及其应用

口服脉冲控释给药系统因具有定时或定位释放的特点而成为当前药剂研究领域的热点.本文介绍了其释药机制,包括有机酸诱导、渗透压调节、pH依赖、时间依赖、酶依赖、pH-时间依赖及各释药机制应用实例.提出了该给药系统在应用中,尤其是对中药复方制剂所存在的一些问题,期望为口服中药脉冲控释给药系统的研究提供思路.     

口服缓/控释药物制剂技术研究进展

目的:介绍口服缓/控释药物制剂技术的研究进展.方法:查阅近几年国内外文献报道,进行分析、归纳.结果:该技术正发展成为3种各具特点又相互结合的技术,即定位释放技术、定时释放技术和定速释放技术.结论:研究口服缓/控释药物制剂技术,对提高药物疗效、开展临床药学研究、推动医药科研和制药工业的发展具有重要的意义.     

Oral Solid Controlled Release Dosage Forms: Role of GI-Mechanical Destructive Forces and Colonic Release in Drug Absorption Under Fasted and Fed Conditions in Humans

Purpose. This study was undertaken to examine the effects of mechanical destructive forces on drug release from controlled release (CR) dosage forms in vitro and in vivo and their colonic release, using two CR tablets of acetaminophen A and B, showing slower and faster erosion rates, respectively. Methods. In vitro release rates were determined by several official methods. Tablets were administered to healthy volunteers under fasting and fed conditions. Results. Both tablets showed similar release rates under mild destructive conditions (e.g., paddle method at 10 rpm) but CR-B showed faster release under highly destructive conditions (e.g., rotating basket method at 150 rpm), where the tablet was eroded. The in vivo release from CR-B was faster than from CR-A, possibly because of enhanced erosion. The variable in vivo release from CR-B indicated large inter-subject differences in destructive GI forces. The fastest in vivo release from CR-B among individuals was approximated by the in vitro dissolution determined by destructive methods such as the rotating basket at 150 rpm. The slowest in vivo release from tablets A and B was lower than the dissolution by the paddle method at 10 rpm. The release from both tablets was markedly reduced at 3–4 hrs after dosing irrespective of feeding conditions which can be attributed to release inhibition in the colon. Conclusions. Effects of GI destructive forces on the tablet erosion and the release inhibition in the colon must be considered in the development of CR dosage forms.     

Oral Delivery of Heparin in Combination with Sodium N-[8-(2-Hydroxybenzoyl)amino]caprylate: Pharmacological Considerations

Pharmaceutical Research -     

Synthesis and In Vitro Evaluation of Chitosan-EDTA-Protease-Inhibitor Conjugates Which Might Be Useful in Oral Delivery of Peptides and Proteins

Purpose. To develop a novel mucoadhesive polymer that protects peptide drugs from degradation by secreted as well as membrane-bound proteases in the intestine, and to evaluate this polymer in vitro. Methods. The serine protease inhibitors antipain, chymostatin and elastatinal were covalently linked to chitosan (poly-[l 4]--D-glucosamine). Thereafter, the complexing agent ethylenediaminete-traacetic acid (EDTA) was bound to the remaining primary amino groups of the polymer. The inhibitory effect of the resulting polymer-conjugate towards trypsin (EC 3.4.21.4), chymotrypsin (EC 3.4.21.1), elastase (3.4.21.36), carboxypeptidase A (EC 3.4.17.1), carboxypeptidase B (EC 3.4.17.2) and aminopeptidase N (EC 3.4.11.2) as well as its mucoadhesive properties were evaluated in vitro. Results. Whereas the novel polymer-conjugate exhibited excellent swelling properties, its adhesive force was under our assay conditions 42% lower than that of unmodified chitosan. However, the polymer-conjugate showed a strong inhibitory activity towards all tested serine proteases. Due to its additional high binding affinity towards bivalent metal ions, it also inhibited the Zn²⁺-dependent exopeptidases carboxypeptidase A, B and aminopeptidase N. Conclusions. The novel mucoadhesive polymer-conjugate described in this study seems to be a useful tool in overcoming the enzymatic barrier to perorally administered therapeutic peptides and proteins.     

The Potential of Exosomes From Cow Milk for Oral Delivery

Many pharmaceuticals must be administered intravenously due to their poor oral bioavailability. In addition to issues associated with sterility and inconvenience, the cost of repeated infusion over a 6-week course of therapy costs the health care system tens of billions of dollars per year. Attempts to improve oral bioavailability have traditionally focused on enhancing drug solubility and membrane permeability, and the use of synthetic nanoparticles has also been investigated. As an alternative strategy, some recent reports have clearly demonstrated that exosomes from cow milk are absorbed from the gastrointestinal tract in humans and could potentially be used for oral delivery of drugs that are traditionally administered intravenously. Our previous work has shown that antibodies are present in exosome preparations, and the current work with milk exosomes suggests that absorption from the gastrointestinal tract occurs via the “neonatal” Fc receptor, FcRn. Furthermore, our results demonstrate that milk exosomes are absorbed from the gut as intact particles that can be modified with ligands to promote retention in target tissues.