Oral peptide and protein delivery: intestinal obstacles and commercial prospects

Influence of the surface properties of nanocapsules on their interaction with intestinal barriers

Despite the convenience of the oral route for drug administration, the existence of different physiological barriers associated with the intestinal tract greatly lowers the bioavailability of many active compounds. We have previously suggested the potential polymeric nanocapsules, consisting of an oily core surrounded by a polymer shell, as oral drug delivery carriers. Here we present a systematic study of the influence of the surface properties of these nanocapsules on their interaction with the intestinal barriers. Two different surfactants, Pluronic®F68 (PF68) and F127 (PF127), and two polymeric shells, chitosan (CS) and polyarginine (PARG) were chosen for the formulation of the nanocapsules. We analyzed nine different combinations of these polymers and surfactants, and studied the effect of each specific combination on their colloidal stability, enzymatic degradation, and mucoadhesion/mucodiffusion. Our results indicate that both, the polymer shell and the surfactants located at the oil/water interface, influence the interaction of the nanocapsules with the intestinal barriers. More interestingly, according to our observations, the shell components of the nanosystems may have either synergic or disruptive effects on their capacity to overcome the intestinal barriers.

Quantification of Multifunctional Dipeptide YA from Oyster Hydrolysate for Quality Control and Efficacy Evaluation

YA is an angiotensin-I-converting enzyme- (ACE-) inhibitory peptide from oyster hydrolysate with antihypertensive activity. Its antioxidant and anti-inflammatory activity were investigated in this study. YA can dose-dependently quench DPPH and ABTS radical and inhibit lipopolysaccharide-induced nitric oxide in RAW 264.7 cells. YA is a multifunctional peptide and was selected as an indicator for quality control and efficacy evaluation of oyster hydrolysate. A practical HPLC/UV assay for YA quantification was developed and validated. It was proved to be accurate and reliable, according to parameters such as specificity, linearity, precision, and accuracy. The quantity results of YA showed that the stage of enzymatic hydrolysis was a critical control point for quality control; the efficacy of oyster hydrolysate can be enhanced after digested in the gastrointestinal tract due to the release of YA by brush border peptidases. Therefore, YA from oyster hydrolysate is a potential bioactive ingredient for functional foods to combat hypertension.

An Evaluation of the Potential of NMR Spectroscopy and Computational Modelling Methods to Inform Biopharmaceutical Formulations

Protein-based therapeutics are considered to be one of the most important classes of pharmaceuticals on the market. The growing need to prolong stability of high protein concentrations in liquid form has proven to be challenging. Therefore, significant effort is being made to design formulations which can enable the storage of these highly concentrated protein therapies for up to 2 years. Currently, the excipient selection approach involves empirical high-throughput screening, but does not reveal details on aggregation mechanisms or the molecular-level effects of the formulations under storage conditions. Computational modelling approaches have the potential to elucidate such mechanisms, and rapidly screen in silico prior to experimental testing. Nuclear Magnetic Resonance (NMR) spectroscopy can also provide complementary insights into excipient–protein interactions. This review will highlight the underpinning principles of molecular modelling and NMR spectroscopy. It will also discuss the advancements in the applications of computational and NMR approaches in investigating excipient–protein interactions.

3D printed medicines: A new branch of digital healthcare

Three-dimensional printing (3DP) is a highly disruptive technology with the potential to change the way pharmaceuticals are designed, prescribed and produced. Owing to its low cost, diversity, portability and simplicity, fused deposition modeling (FDM) is well suited to a multitude of pharmaceutical applications in digital health. Favourably, through the combination of digital and genomic technologies, FDM enables the remote fabrication of drug delivery systems from 3D models having unique shapes, sizes and dosages, enabling greater control over the release characteristics and hence bioavailability of medications. In turn, this system could accelerate the digital healthcare revolution, enabling medicines to be tailored to the individual needs of each patient on demand. To date, a variety of FDM 3D printed medical products (e.g. implants) have been commercialised for clinical use. However, within pharmaceuticals, certain regulatory hurdles still remain. This article reviews the current state-of-the-art in FDM technology for medical and pharmaceutical research, including its use for personalised treatments and interconnection within digital health networks. The outstanding challenges are also discussed, with a focus on the future developments that are required to facilitate its integration within pharmacies and hospitals.

Battle of GLP-1 delivery technologies

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) belong to an important therapeutic class for treatment of type 2 diabetes. Six GLP-1 RAs, each utilizing a unique drug delivery strategy, are now approved by the Food and Drug Administration (FDA) and additional, novel GLP-1 RAs are still under development, making for a crowded marketplace and fierce competition among the manufacturers of these products. As rapid elimination is a major challenge for clinical application of GLP-1 RAs, various half-life extension strategies have been successfully employed including sequential modification, attachment of fatty-acid to peptide, fusion with human serum albumin, fusion with the fragment crystallizable (Fc) region of a monoclonal antibody, sustained drug delivery systems, and PEGylation. In this review, we discuss the scientific rationale of the various half-life extension strategies used for GLP-1 RA development. By analyzing and comparing different approved GLP-1 RAs and those in development, we focus on assessing how half-life extending strategies impact the pharmacokinetics, pharmacodynamics, safety, patient usability and ultimately, the commercial success of GLP-1 RA products. We also anticipate future GLP-1 RA development trends. Since similar drug delivery strategies are also applied for developing other therapeutic peptides, we expect this case study of GLP-1 RAs will provide generalizable concepts for the rational design of therapeutic peptides products with extended duration of action.

Bioadhesive Chitosan-Coated Cationic Nanoliposomes With Improved Insulin Encapsulation and Prolonged Oral Hypoglycemic Effect in Diabetic Mice

Oral administration of insulin is hampered by the lack of carriers that can efficiently achieve high encapsulation, avoid gastric degradation, overcome mucosal barriers, and prolong the hypoglycemic effect. Chitosan (CS)-coated insulin-loaded cationic liposomes have been developed and optimized for improved oral delivery. Liposomes were prepared cationic to improve insulin encapsulation. CS was selected as a mucoadhesive coat to prolong the system's residence and absorption. The performance of CS-coated liposomes compared with uncoated liposomes was examined in vitro, ex vivo, and in vivo in streptozotocin-induced diabetic mice. Free uncoated liposomes showed high positive zeta potential of +58.8 ± 2.2 mV that reduced (+29.9 ± 1.4 mV) after insulin encapsulation, confirming the obtained high entrapment efficiency of 87.5 ± 0.6%. CS-coated liposomes showed nanosize of 439.0 ± 12.3 nm and zeta potential of +60.5 ± 1.9 mV. In vitro insulin release was limited to 18.9 ± 0.35% in simulated gastric fluid, whereas in simulated intestinal fluid, 73.33 ± 0.68% was released after 48 h from CS-coated liposomes. Ex vivo intestinal mucoadhesion showed increased tissue residence of CS-coated liposomes compared with uncoated liposomes. A striking reduction in the glucose level was observed 1 h after oral administration of CS-coated liposomes and maintained up to 8 h (p <0.01 vs. insulin solution or uncoated liposomes) within the normal value 129.29 ± 3.15 mg/dL. In conclusion, CS-coated insulin-loaded cationic liposomes improved loading efficiency with promising prolonged pharmacological effect.

Peptide chemistry toolbox - Transforming natural peptides into peptide therapeutics

The development of solid phase peptide synthesis has released tremendous opportunities for using synthetic peptides in medicinal applications. In the last decades, peptide therapeutics became an emerging market in pharmaceutical industry. The need for synthetic strategies in order to improve peptidic properties, such as longer half-life, higher bioavailability, increased potency and efficiency is accordingly rising. In this mini-review, we present a toolbox of modifications in peptide chemistry for overcoming the main drawbacks during the transition from natural peptides to peptide therapeutics. Modifications at the level of the peptide backbone, amino acid side chains and higher orders of structures are described. Furthermore, we are discussing the future of peptide therapeutics development and their impact on the pharmaceutical market.

The combination of endolysosomal escape and basolateral stimulation to overcome the difficulties of "easy uptake hard transcytosis" of ligand-modified nanoparticles in oral drug delivery

Ligand-modified nanoparticles (NPs) are an effective tool to increase the endocytosis efficiency of drugs, but these functionalized NPs face the drawback of "easy uptake hard transcytosis" in the oral delivery of proteins and peptides. Adversely, the resulting deficiency in transcytosis has not attracted much attention. Herein, NPs modified with the low-density lipoprotein receptor (LDLR) ligand NH₂-C6-[cMPRLRGC]c-NH₂, i.e., peptide-22 (P22NPs) were fabricated to investigate strategies related to the enhancement of transcytosis. By systematically studying the intracellular trafficking of NPs, it was found that reduced transcytosis might be associated with the entrapment of P22NPs in endosomes or lysosomes and limited basolateral exocytosis. On this basis, the prevention of the endolysosomal entrapment of NPs and the acceleration of basolateral exocytosis should be considered as strategies to enhance the transcytosis of NPs. By screening chemicals that could help the endosomal/lysosomal escape of chemicals related to LDLR-mediated transcytosis, it was shown that hemagglutinin-2 (HA₂) and metformin had higher abilities to enhance the exocytosis of P22NPs. The transcytosis efficiencies of insulin loaded in P22NPs were also investigated, and a 3.2-fold increase in transcytosis was observed in comparison with free insulin. The transcytosis efficiencies of insulin could be further increased by the addition of metformin or HA₂ (3.6-fold or 4.1-fold higher than that of free insulin). Inspiringly, the simultaneous addition of the abovementioned two chemicals led to the highest transcytosis efficiency of insulin, which was up to 5.1-fold higher than that of free insulin. These results demonstrated that endolysosomal entrapment and basolateral exocytosis are two of the most important limiting steps for the "easy uptake hard transcytosis" of orally administered ligand-modified NPs. Moreover, our work provides a new point of view for the design of novel oral drug delivery systems.

Dietary Apostichopus japonicus Alleviates Diabetes Symptoms and Modulates Genes Expression in Kidney Tissues of db/db Mice

The effects of Apostichopus japonicus enzymatic hydrolysate on the regulation of dyslipidemia, pathoglycemia, and transcription changes in kidney tissues of db/db mice were evaluated. In this study, the symptoms of diabetes in db/db mice were alleviated after 10 weeks of treatments with low (db/db + LD group) and high dose (db/db + HD group) of Apostichopus japonicus enzymatic hydrolysate, and the high dose treatment showed a better antidiabetic effect. Compared with the db/db group, the fasting blood glucose levels (36.84 ± 7.82 vs 25.18 ± 6.84 mmol/L, P < 0.01), the urine glucose levels (45.44 ± 3.93 vs 22.66 ± 5.58 mmol/L, P < 0.01), and the serum insulin sensitivity index (-4.65 ± 0.43 vs -4.74 ± 0.75, P > 0.05) in the db/db + HD group were decreased, whereas the fasting plasma insulin (3.12 ± 1.08 vs 5.54 ± 1.82 μg/L, P < 0.01) and the serum insulin resistance index (5.01 ± 2.02 vs 5.96 ± 2.49, P < 0.05) were increased. Subsequently, the kidney transcription profiles were measured in the db/db group and db/db + HD group via microarray, and the results show that Apostichopus japonicus hydrolysate induced differential expression of 77 genes. Among these genes, the down-regulation of genes ntrK1 and ptpN5 played vital roles, as this effect induced the further down-regulation of neurotrophin tyrosine kinase, protein tyrosine phosphatase, and other transcription factors, which are involved in the classical mitogen-activated protein kinases (MAPK) and p38MAPK signaling pathways. The inhibited MAPK and p38MAPK signaling pathways are involved in glycometabolism and the control of lipid metabolism, and they regulate the occurrence and development of diabetic nephropathy.

Design and intestinal mucus penetration mechanism of core-shell nanocomplex

The objective of this study was to design intestinal mucus-penetrating core-shell nanocomplex by functionally mimicking the surface of virus, which can be used as the carrier for peroral delivery of macromolecules, and further understand the influence of nanocomplex surface properties on the mucosal permeation capacity. Taking insulin as a model drug, the core was formed by the self-assembly among positively charged chitosan, insulin and negatively charged sodium tripolyphosphate, different types of alginates were used as the shell forming material. The nanocomplex was characterized by dynamic light scattering (DLS), atomic force microscopy (AFM) and FTIR. Nanocomplex movement in mucus was recorded using multiple particle tracking (MPT) method. Permeation and uptake of different nanocomplex were studied in rat intestine. It was demonstrated that alginate coating layer was successfully formed on the core and the core-shell nanocomplex showed a good physical stability and improved enzymatic degradation protection. The mucus penetration and MPT study showed that the mucus penetration capacity of the nanocomplex was surface charge and coating polymer structure dependent, nanocomplex with negative alginate coating had 1.6-2.5 times higher mucus penetration ability than that of positively charged chitosan-insulin nanocomplex. Moreover, the mucus penetration ability of the core-shell nanocomplex was alginate structure dependent, whereas alginate with lower G content and lower molecular weight showed the best permeation enhancing ability. The improvement of intestine permeation and intestinal villi uptake of the core-shell nanocomplex were further confirmed in rat intestine and multiple uptake mechanisms were involved in the transport process. In conclusion, core-shell nanocomplex composed of oppositely charged materials could provide a strategy to overcome the mucus barrier and enhance the mucosal permeability.

Novel route of insulin delivery using an implant-mediated drug delivery system

Patients with diabetes mellitus (DM) frequently require multiple painful injections of insulin to manage their blood glucose level. A newly introduced, modified titanium implant, the implant-mediated drug delivery system (IMDDS), has the advantage of sustained, needle-free drug delivery. We evaluated the feasibility of the IMDDS as an alternative route of insulin delivery in an alloxan-induced rabbit DM model. Among a total of 30 rabbits with IMDDSs, 25 survived the induction and had a blood glucose level (BGL) higher than 300 mg/dl. The animals were divided into two groups: 13 in the test group to which insulin was administered via the IMDDS and 12 in the untreated control group. The BGL was monitored and measured at 0, 2, 4, 6, 8, 12, and 24 hours on the first day and every 12 hours thereafter for a total of 2 weeks. Marked hypoglycemic effects of insulin in the test rabbits were detected from the 2-h time point, and the mean BGL fell below the normal range from 12 h after insulin administration via the IMDDS. The effects lasted the entire 2-week period. Control rabbits did not show a pronounced decrease in BGL except for three animals who exhibited spontaneous recovery. The mean body weight of the test group was significantly higher than that of the control group at the end of the observation period. Although this implant requires several improvements, the IMDDS exhibited promise as an alternative route of insulin delivery with the advantages of being a sustained, needle-free insulin delivery system.

Development of Potent, Protease-Resistant Agonists of the Parathyroid Hormone Receptor with Broad β Residue Distribution

The parathyroid hormone receptor 1 (PTHR1) is a member of the B-family of GPCRs; these receptors are activated by long polypeptide hormones and constitute targets of drug development efforts. Parathyroid hormone (PTH, 84 residues) and PTH-related protein (PTHrP, 141 residues) are natural agonists of PTHR1, and an N-terminal fragment of PTH, PTH(1-34), is used clinically to treat osteoporosis. Conventional peptides in the 20-40-mer length range are rapidly degraded by proteases, which may limit their biomedical utility. We have used the PTHR1-ligand system to explore the impact of broadly distributed replacement of α-amino acid residues with β-amino acid residues on susceptibility to proteolysis and agonist activity. This effort led us to identify new PTHR1 agonists that contain α → β replacements throughout their sequences, manifest potent agonist activity in cellular assays, and display remarkable resistance to proteolysis, in cases remaining active after extended exposure to simulated gastric fluid. The strategy we have employed suggests a path toward identifying protease-resistant agonists of other B-family GPCRs.

A Multiparticulate Delivery System for Potential Colonic Targeting Using Bovine Serum Albumin as a Model Protein : Theme: Formulation and Manufacturing of Solid Dosage Forms Guest Editors: Tony Zhou and Tonglei Li

PURPOSE

There are many important diseases whose treatment could be improved by delivering a therapeutic protein to the colon, for example, Clostridium difficile infection, ulcerative colitis and Crohn's Disease. The goal of this project was to investigate the feasibility of colonic delivery of proteins using multiparticulate beads.

METHODS

In this work, bovine serum albumin (BSA) was adopted as a model protein. BSA was spray layered onto beads, followed by coating of an enteric polymer EUDRAGIT® FS 30 D to develop a colonic delivery system. The secondary and tertiary structure change and aggregation of BSA during spray layering process was examined. The BSA layered beads were then challenged in an accelerated stability study using International Council for Harmonization (ICH) conditions. The in vitro release of BSA from enteric coated beads was examined using United States Pharmacopeia (USP) dissolution apparatus 1.

RESULTS

No significant changes in the secondary and tertiary structure or aggregation profile of BSA were observed after the spray layering process. Degradation of BSA to different extents was detected after storing at 25°C and 40°C for 38 days. Enteric coated BSA beads were intact in acidic media while released BSA in pH 7.4 phosphate buffer.

CONCLUSION

We showed the feasibility of delivering proteins to colon in vitro using multiparticulate system.

Atomization of denatured whey proteins as a novel and simple way to improve oral drug delivery system properties

In the sphere of drug delivery, denatured whey protein (DWP) has in recent times gained press. However, to date, no scalable and affordable dosage form has been developed. The objective of our study was to evaluate the potential use of spray-dried DWP as a ready to use excipient for oral drug delivery. Therefore, solid state, FTIR spectra and wettability were studied. Dissolution, mucoadhesion and the effect on paracellular permeability were also evaluated. The spray-dried DWP particles were spherical with 4μm mean diameter. Further, relative to native WP, the spray-dried DWP particles bore reduced wettability, and their structure was characterized by the exposure of a high amount of free thiol and by the formation of intermolecular β-sheets. The DWP powders were mucoadhesive, enzymatic inhibitors, biocompatible and they induced the opening of tight junctions. Our study shows great potential for the use of spray-drying as a technique to modify the dissolution rate of drugs and enhance the oral bioavailability of molecules. That is, the use of spray drying as a single step ready to use DWP excipient.

Polyarginine nanocapsules: A versatile nanocarrier with potential in transmucosal drug delivery

The objective of this work was to investigate the potential utility of nanocapsules composed of an oily core decorated with a single polyarginine (PARG), or double PARG/polyacrylic acid (PAA) layer as oral peptide delivery carrier. A step-by-step formulation optimization process was designed, which involved the study of the influence of the surfactants, oils and polymer shells (PARG of different molecular weight and PAA) on the nanocapsules physicochemical properties, peptide loading efficiency, stability in simulated intestinal fluids (SIF) and capacity to enhance the permeability of the intestinal epithelium. Despite the lipophilic nature of the nanocapsules, it was possible to achieve a moderate loading of the hydrophilic model peptide salmon calcitonin and control its release in SIF, by adjusting the formulation conditions. Finally, studies in the Caco-2 epithelial cell line showed the capacity of the nanocapsules to reduce the transepithelial electric resistance of the monolayer, without compromising their viability. Overall, these properties suggest the capacity of polyarginine nanocapsules for enhancing the transport of peptides across epithelia.

Novel strategies in the oral delivery of antidiabetic peptide drugs - Insulin, GLP 1 and its analogs

As diabetes is a complex disorder being a major cause of mortality and morbidity in epidemic rates, continuous research has been done on new drug types and administration routes. Up to now, a large number of therapeutic peptides have been produced to treat diabetes including insulin, glucagon-like peptide-1 (GLP-1) and its analogs. The most common route of administration of these antidiabetic peptides is parenteral. Due to several drawbacks associated with this invasive route, delivery of these antidiabetic peptides by the oral route has been a goal of pharmaceutical technology for many decades. Dosage form development should focus on overcoming the limitations facing oral peptides delivery as degradation by proteolytic enzymes and poor absorption in the gastrointestinal tract (GIT). This review focuses on currently developed strategies to improve oral bioavailability of these peptide based drugs; evaluating their advantages and limitations in addition to discussing future perspectives on oral peptides delivery. Depending on the previous reports and papers, the area of nanocarriers systems including polymeric nanoparticles, solid lipid nanoparticles, liposomes and micelles seem to be the most promising strategy that could be applied for successful oral peptides delivery; but still further potential attempts are required to be able to achieve the FDA approved oral antidiabetic peptide delivery system.

Overview and Future Potential of Buccal Mucoadhesive Films as Drug Delivery Systems for Biologics

The main route of administration for drug products is the oral route, yet biologics are initially developed as injectables due to their limited stability through the gastrointestinal tract and solubility issues. In order to avoid injections, a myriad of investigations on alternative administration routes that can bypass enzymatic degradation and the first-pass effect are found in the literature. As an alternative site for biologics absorption, the buccal route presents with a number of advantages. The buccal mucosa is a barrier, providing protection to underlying tissue, but is more permeable than other alternative routes such as the skin. Buccal films are polymeric matrices designed to be mucoadhesive properties and usually formulated with permeability enhancers to improve bioavailability. Conventionally, buccal films for biologics are manufactured by solvent casting, yet recent developments have shown the potential of hot melt extrusion, and most recently ink jet printing as promising strategies. This review aims at depicting the field of biologics-loaded mucoadhesive films as buccal drug delivery systems. In light of the literature available, the buccal epithelium is a promising route for biologics administration, which is reflected in clinical trials currently in progress, looking forward to register and commercialize the first biologic product formulated as a buccal film.

Nanocarrier fabrication and macromolecule drug delivery: challenges and opportunities

Macromolecules (proteins/peptides) have the potential for the development of new therapeutics. Due to their specific mechanism of action, macromolecules can be administered at relatively low doses compared with small-molecule drugs. Unfortunately, the therapeutic potential and clinical application of macromolecules is hampered by various obstacles including their large size, short in vivo half-life, phagocytic clearance, poor membrane permeability and structural instability. These challenges have encouraged researchers to develop novel strategies for effective delivery of macromolecules. In this review, various routes of macromolecule administration (invasive/noninvasive) are discussed. The advantages/limitations of novel delivery systems and the potential role of nanotechnology for the delivery of macromolecules are elaborated. In addition, fabrication approaches to make nanoformulations in different shapes and sizes are also summarized.

Oral delivery of diabetes peptides - Comparing standard formulations incorporating functional excipients and nanotechnologies in the translational context

While some orally delivered diabetes peptides are moving to late development with standard formulations incorporating functional excipients, the demonstration of the value of nanotechnology in clinic is still at an early stage. The goal of this review is to compare these two drug delivery approaches from a physico-chemical and a biopharmaceutical standpoint in an attempt to define how nanotechnology-based products can be differentiated from standard oral dosage forms for oral bioavailability of diabetes peptides. Points to consider in a translational approach are outlined to seize the opportunities offered by a better understanding of both the intestinal barrier and of nano-carriers designed for oral delivery.

Inflammatory bowel disease: exploring gut pathophysiology for novel therapeutic targets

Ulcerative colitis and Crohn's disease are the 2 major phenotypes of inflammatory bowel disease (IBD), which are influenced by a complex interplay of immunological and genetic elements, though the precise etiology still remains unknown. With IBD developing into a globally prevailing disease, there is a need to explore new targets and a thorough understanding of the pathophysiological differences between the healthy and diseased gut could unearth new therapeutic opportunities. In this review, we provide an overview of the major aspects of IBD pathogenesis and thereafter present a comprehensive analysis of the gut pathophysiology leading to a discussion on some of the most promising targets and biologic therapies currently being explored. These include various gut proteins (CXCL-10, GATA-3, NKG2D, CD98, microRNAs), immune cells recruited to the gut (mast cells, eosinophils, toll-like receptors 2, 4), dysregulated proinflammatory cytokines (interleukin-6, -13, -18, -21), and commensal microbiota (probiotics and fecal microbiota transplantation). We also evaluate some of the emerging nonconventional therapies being explored in IBD treatment focusing on the latest developments in stem cell research, oral targeting of the gut-associated lymphoid tissue, novel anti-inflammatory signaling pathway targeting, adenosine deaminase inhibition, and the beneficial effects of antioxidant and nutraceutical therapies. In addition, we highlight the growth of biologics and their targets in IBD by providing information on the preclinical and clinical development of over 60 biopharmaceuticals representing the state of the art in ulcerative colitis and Crohn's disease drug development.

Emerging delivery platforms for mucosal administration of biopharmaceuticals: a critical update on nasal, pulmonary and oral routes

INTRODUCTION

Protein and peptide-based drugs are preferred therapeutics due to their specificity but are mainly administered by injection. Alternative routes for peptide delivery are preferred because of their ease of administration and increased patient compliance. Areas covered: This review provides a critical overview of current strategies for non-invasive mucosal delivery routes of therapeutic proteins and peptides, with emphasis on their advantages and limitations. Selected new trends and interesting novel formulations in advanced preclinical and clinical development stages for the pulmonary, nasal and the oral route are discussed for the most relevant peptide and protein drugs in terms of their specific requirements and intended therapeutic applications. Expert opinion: Despite the low frequency of clinical breakthroughs with non-invasive routes, these remain an active research area not only due to their improved therapeutic potential, but also due to the attractive commercial outcomes they offer. Currently, a number of technologies are adopted, including combinations of penetration enhancers with protease inhibitors and/or nanotechnology-based products and a few candidates are anticipated to be approved in the near future.

Nanoparticles for oral delivery: Design, evaluation and state-of-the-art

The oral route is a preferred method of drug administration, though achieving effective drug delivery and minimizing off-target side effects is often challenging. Formulation into nanoparticles can improve drug stability in the harsh gastrointestinal (GI) tract environment, providing opportunities for targeting specific sites in the GI tract, increasing drug solubility and bioavailability, and providing sustained release in the GI tract. However, the unique and diverse physiology throughout the GI tract, including wide variation in pH, mucus that varies in thickness and structure, numerous cell types, and various physiological functions are both a barrier to effective delivery and an opportunity for nanoparticle design. Here, nanoparticle design aspects to improve delivery to particular sites in the GI tract are discussed. We then review new methods for evaluating oral nanoparticle formulations, including a short commentary on data interpretation and translation. Finally, the state-of-the-art in preclinical targeted nanoparticle design is reviewed.

Chemically modified peptides and proteins - critical considerations for oral delivery

Numerous approaches have been explored to date in the pursuit of delivering peptides or proteins via the oral route. One such example is chemical modification, whereby the native structure of a peptide or protein is tailored to provide a more efficient uptake across the epithelial barrier of the gastrointestinal tract via incorporation of a chemical motif or moiety. In this regard, a diverse array of concepts have been reported, ranging from the exploitation of endogenous transport mechanisms to incorporation of physicochemical modifications in the molecule, which promote more favorable interactions with the absorptive membrane at the cell surface. This review provides an overview of the modification technologies described in the literature and offers insights into some pragmatic considerations pertaining to their translation into clinically viable concepts.

Effective Delivery of Male Contraceptives Behind the Blood-Testis Barrier (BTB) - Lesson from Adjudin

The blood-testis barrier (BTB) is one of the tightest blood-tissue barriers in the mammalian body. It divides the seminiferous epithelium of the seminiferous tubule, the functional unit of the testis, where spermatogenesis takes place, into the basal and the adluminal (apical) compartments. Functionally, the BTB provides a unique microenvironment for meiosis I/II and post-meiotic spermatid development which take place exclusively in the apical compartment, away from the host immune system, and it contributes to the immune privilege status of testis. However, the BTB also poses major obstacles in developing male contraceptives (e.g., adjudin) that exert their effects on germ cells in the apical compartment, such as by disrupting spermatid adhesion to the Sertoli cell, causing germ cell exfoliation from the testis. Besides the tight junction (TJ) between adjacent Sertoli cells at the BTB that restricts the entry of contraceptives from the microvessels in the interstitium to the adluminal compartment, drug transporters, such as P-glycoprotein and multidrug resistance-associated protein 1 (MRP1), are also present that actively pump drugs out of the testis, limiting drug bioavailability. Recent advances in drug formulations, such as drug particle micronization (<50 μm) and co-grinding of drug particles with ß-cyclodextrin have improved bioavailability of contraceptives via considerable increase in solubility. Herein, we discuss development in drug formulations using adjudin as an example. We also put emphasis on the possible use of nanotechnology to deliver adjudin to the apical compartment with multidrug magnetic mesoporous silica nanoparticles. These advances in technology will significantly enhance our ability to develop effective non-hormonal male contraceptives for men.

What's Next for Gastrointestinal Disorders: No Needles?

A myriad of pathologies affect the gastrointestinal tract, citing this affected area as a significant target for therapeutic intervention. One group of therapeutic agents, antisense and oligonucleotides and small interfering RNAs, offer a promising platform for treating a wide variety of diseases ranging from cancer to auto-immune diseases. Current delivery methods are carried out either systemically or locally into diseased areas, both of which involve needles. The challenge in orally administering this type of treatment lies in the complications that arise due to the vast environmental extremes found within the gastrointestinal tract, owing to the fact that, as the drug travels down the gastrointestinal tract, it is subjected to pH changes and interactions with bacteria and a variety of digestive and protective enzymes including proteases, DNAses, and RNAses. Overcoming these challenges to allow the practical application of these drugs is a priority that has invoked a multitude of research in the chemical, biological, and material sciences. In this review, we will address common gastrointestinal pathologies, the barriers to oral-based therapies and antisense-interfering technologies, the approaches that have already been applied for their delivery, and the current status of antisense drug therapy clinical trials for gastrointestinal-related disorders.

Stability, toxicity and intestinal permeation enhancement of two food-derived antihypertensive tripeptides, Ile-Pro-Pro and Leu-Lys-Pro

Two food-derived ACE inhibitory peptides, Ile-Pro-Pro (IPP) and Leu-Lys-Pro (LKP), may have potential as alternative treatments for treatment of mild- or pre-hypertension. Lack of stability to secretory and intracellular peptidases and poor permeability across intestinal epithelia are typical limiting factors of oral delivery of peptides. The stability of IPP and LKP was confirmed in vitro in rat intestinal washes, and intestinal and liver homogenates over 60min. A positive protein control for peptidases, insulin, was significantly digested in each format over the same period. Neither tripeptide showed cytotoxic activity on Caco-2 and Hep G2 cells using the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay, even after chronic exposure. The basal Papp of fluorescein isothiocyanate (FITC)-labeled IPP and FITC-LKP across isolated rat jejunal and colonic mucosae were low, but were significantly increased in each tissue type by the medium chain fatty acids (MCFA) permeation enhancers, sodium caprate (C10) and the sodium salt of 10-undecylenic acid (uC11). IPP and LKP were therefore stable against intestinal and liver peptidases and were non-cytotoxic; their Papp values across rat intestinal mucosae were low, but could be increased by MCFA. There is potential to make on oral dosage form once in vivo pharmacology is confirmed.

An endostatin-derived peptide orally exerts anti-fibrotic activity in a murine pulmonary fibrosis model

OBJECTIVE

Pulmonary fibrosis causes high morbidity and mortality in affected individuals. Recently, we showed that parenteral or intratracheal administration of a peptide derived from endostatin, called E4, prevents and ameliorates fibrosis using different models of dermal and pulmonary disease. No marketed orally delivered peptide drugs are currently available for progressive pulmonary fibrosis; however oral delivery of drugs is the preferred route for treating most chronic diseases. Thus, we investigated whether oral administration of E4 peptide exerted anti-fibrotic activity in a murine pulmonary fibrosis model.

METHODS

Bleomycin (1.2mU/g body weight) was intratracheally administrated to male 6-8-week-old C57BL/6J mice. E4 peptide (20, 10, 5, and 1 μg/mouse) or scrambled control peptide (20 μg/mouse) was orally administered on the same day as bleomycin. In some experiments, E4 peptide (10 and 5 μg/mouse) was orally administered three times on days 0, 3, and 6 post-bleomycin treatment. Lungs were harvested on day 21 for histological analysis and hydroxyproline assay.

RESULTS

Histological analysis and hydroxyproline assay revealed that bleomycin successfully induced pulmonary fibrosis, and that 20 μg of oral E4 peptide ameliorated the fibrosis. The lower doses of E4 peptide (10, 5, and 1 μg) were insufficient to exert anti-fibrotic activity when given as a single dose. Multiple doses of E4 peptide efficiently exerted anti-fibrotic activity even at lower doses.

CONCLUSION

E4 peptide shows oral bioavailability and exerts anti-fibrotic activity in a bleomycin-induced pulmonary fibrosis model. We suggest that E4 peptide is a novel oral drug for fibroproliferative disorders.

N-trimethyl chitosan chloride-coated PLGA nanoparticles overcoming multiple barriers to oral insulin absorption

Although several strategies have been applied for oral insulin delivery to improve insulin bioavailability, little success has been achieved. To overcome multiple barriers to oral insulin absorption simultaneously, insulin-loaded N-trimethyl chitosan chloride (TMC)-coated polylactide-co-glycoside (PLGA) nanoparticles (Ins TMC-PLGA NPs) were formulated in our study. The Ins TMC-PLGA NPs were prepared using the double-emulsion solvent evaporation method and were characterized to determine their size (247.6 ± 7.2 nm), ζ-potential (45.2 ± 4.6 mV), insulin-loading capacity (7.8 ± 0.5%) and encapsulation efficiency (47.0 ± 2.9%). The stability and insulin release of the nanoparticles in enzyme-containing simulated gastrointestinal fluids suggested that the TMC-PLGA NPs could partially protect insulin from enzymatic degradation. Compared with unmodified PLGA NPs, the positively charged TMC-PLGA NPs could improve the mucus penetration of insulin in mucus-secreting HT29-MTX cells, the cellular uptake of insulin via clathrin- or adsorption-mediated endocytosis in Caco-2 cells and the permeation of insulin across a Caco-2 cell monolayer through tight junction opening. After oral administration in mice, the TMC-PLGA NPs moved more slowly through the gastrointestinal tract compared with unmodified PLGA NPs, indicating the mucoadhesive property of the nanoparticles after TMC coating. Additionally, in pharmacological studies in diabetic rats, orally administered Ins TMC-PLGA NPs produced a stronger hypoglycemic effect, with 2-fold higher relative pharmacological availability compared with unmodified NPs. In conclusion, oral insulin absorption is improved by TMC-PLGA NPs with the multiple absorption barriers overcome simultaneously. TMC-PLGA NPs may be a promising drug delivery system for oral administration of macromolecular therapeutics.

Stability of peptide drugs in the colon

This study was the first to investigate the colonic stability of 17 peptide molecules (insulin, calcitonin, glucagon, secretin, somatostatin, desmopressin, oxytocin, Arg-vasopressin, octreotide, ciclosporin, leuprolide, nafarelin, buserelin, histrelin, [D-Ser(4)]-gonadorelin, deslorelin, and goserelin) in a model of the large intestine using mixed human faecal bacteria. Of these, the larger peptides - insulin, calcitonin, somatostatin, glucagon and secretin - were metabolized rapidly, with complete degradation observed within 5 min. In contrast, a number of the smaller peptides - Arg-vasopressin, desmopressin, oxytocin, gonadorelin, goserelin, buserelin, leuprolide, nafarelin and deslorelin - degraded more slowly, while octreotide, histrelin and ciclosporin were seen to be more stable as compared to the other small peptides under the same conditions. Peptide degradation rate was directly correlated to peptide lipophilicity (logP); those peptides with a higher logP were more stable in the colonic model (R(2)=0.94). In the absence of human faecal bacteria, all peptides were stable. This study highlights the impact of the colonic environment - in particular, the gut microbiota - on the metabolism of peptide drugs, and identifies potential peptide candidates for drug delivery to the colon.

Lessons learned from the clinical development of oral peptides

The oral delivery of peptides and proteins has been hampered by an array of obstacles. However, several promising novel oral delivery systems have been developed. This paper reviews the most advanced oral formulation technologies, and highlights key lessons and implications from studies undertaken to date with these oral formulations. Special interest is given to oral salmon calcitonin (CT), glucagon-like peptide-1 (GLP-1), insulin, PYY-(3-36), recombinant human parathyroid hormone (rhPTH(1-31)-NH2) and PTH(1-34), by different technologies. The issues addressed include (i) interaction with water, (ii) interaction with food, (iii) diurnal variation, (iv) inter- and intra-subject variability, (v) correlation between efficacy and exposure and (vi) key deliverables of different technologies. These key lessons may aid research in the development of other oral formulations.

Protein aggregation and its impact on product quality

Protein pharmaceutical products are typically active as folded monomers that are composed of one or more protein chains, such as the heavy and light chains in monoclonal antibodies that are a mainstay of current drug pipelines. There are numerous possible aggregated states for a given protein, some of which are potentially useful, while most of which are considered deleterious from the perspective of pharmaceutical product quality and performance. This review provides an overview of how and why different aggregated states of proteins occur, how this potentially impacts product quality and performance, fundamental approaches to control aggregate formation, and the practical approaches that are currently used in the pharmaceutical industry.