Oral insulin product hexyl-insulin monoconjugate 2 (HIM2) in type 1 diabetes mellitus: the glucose stabilization effects of HIM2

Insulin Tregopil: An Ultra-Fast Oral Recombinant Human Insulin Analog: Preclinical and Clinical Development in Diabetes Mellitus

Insulin therapy is indispensable for achieving glycemic control in all patients with type 1 diabetes mellitus and many patients with type 2 diabetes mellitus. Insulin injections are associated with negative connotations in patients owing to administration discomfort and adverse effects such as hypoglycemia and weight gain. Insulin administered orally can overcome these limitations by providing a convenient and effective mode of delivery with a potentially lower risk of hypoglycemia. Oral insulin mimics the physiologic process of insulin secretion, absorption into the portal circulation, and subsequent peripheral delivery, unlike the subcutaneous route that results in peripheral hyperinsulinemia. Insulin tregopil (IN-105), a new generation human recombinant insulin, methoxy (polyethylene glycol) hexanoyl human recombinant insulin, is developed by Biocon as an ultra-fast onset short-acting oral insulin analog. This recombinant oral insulin is a single short-chain amphiphilic oligomer modified with the covalent attachment of methoxy-triethylene-glycol-propionyl moiety at Lys-β29-amino group of the B-chain via an amide linkage. Sodium caprate, an excipient in the insulin tregopil formulation, is a permeation enhancer that increases its absorption through the gastrointestinal tract. Also, meal composition has been shown to non-significantly affect its absorption. Several global randomized, controlled clinical trials have been conducted in type 1 and type 2 diabetes patients towards the clinical development of insulin tregopil. The formulation shows post-prandial glucose control that is more effective than placebo throughout the meal period; however, compared with an active comparator insulin aspart, the post-prandial control is more effective mainly in the early post-meal period. It shows a good safety profile with a lower incidence of clinically significant hypoglycemia. This review covers the overall clinical development of insulin tregopil establishing it as an ultra-fast onset, short-acting oral insulin analog for optimizing post-prandial glucose.

Oral insulin delivery: Barriers, strategies, and formulation approaches: A comprehensive review

Diabetes Mellitus is characterized by a hyperglycemic condition which can either be caused by the destruction of the beta cells or by the resistance developed against insulin in the cells. Insulin is a peptide hormone that regulates the metabolism of carbohydrates, proteins, and fats. Type 1 Diabetes Mellitus needs the use of Insulin for efficient management. However invasive methods of administration may lead to reduced adherence by the patients. Hence there is a need for a non-invasive method of administration. Oral Insulin has several merits over the conventional method including patient compliance, and reduced cost, and it also mimics endogenous insulin and hence reaches the liver by the portal vein at a higher concentration and thereby showing improved efficiency. However oral Insulin must pass through several barriers in the gastrointestinal tract. Some strategies that could be utilized to bypass these barriers include the use of permeation enhancers, absorption enhancers, use of suitable polymers, use of suitable carriers, and other agents. Several formulation types have been explored for the oral delivery of Insulin like hydrogels, capsules, tablets, and patches which have been described briefly by the article. A lot of attempts have been made for developing oral insulin delivery however none of them have been commercialized due to numerous shortcomings. Currently, there are several formulations from the companies that are still in the clinical phase, the success or failure of some is yet to be seen in the future.

Advancements, challenges and future perspectives on peptide-based drugs: Focus on antimicrobial peptides

Among other health related issues, the rising concerns on drug resistance led to look for alternative pharmaceutical drugs that are effective both against infectious and noninfectious diseases. Antimicrobial peptides (AMPs) emerged as potential therapeutic molecule with wide range of applications. With their limitations, AMPs have gained reputable attentions in research as well as in the pharmaceutical industry. This review highlighted the historical background, research trends, technological advancements, challenges, and future perspectives in the development and applications of peptide drugs. Some vital questions related with the need for pharmaceutical production, factors for the slow and steady journey, the importance of oral bioavailability, and the drug resistance possibilities of AMPs were raised and addressed accordingly. Therefore, the current study is believed to provide a profound understanding in the past and current scenarios and future directions on the therapeutic impacts of peptide drugs.

Biopolymeric nanocarrier: an auspicious system for oral delivery of insulin

Subcutaneous administration of insulin has been practiced for the clinical supervision of diabetes pathogenesis but it is often ineffective to imitate the glucose homeostasis and is always invasive. Therefore, it causes patient discomfort and infection of local tissue. These issues lead to finding an alternative route for insulin delivery that could be effective, promising, and non-invasive. However, delivery of insulin orally is the most suitable route but the rapid breakdown of insulin by the gastrointestinal enzymes becomes a major barrier to this method. Therefore, nanocarriers (which guard insulin against degradation and facilitate its uptake) are preferred for oral insulin delivery. Among various categories of nanocarriers, bio-polymeric nanocarriers draw special attention owing to their hydrophilic, non-toxic, and biodegradable nature. This review provides a detailed overview of insulin-loaded biopolymer-based nanocarriers, which give future direction in the optimization and development of a clinically functional formulation for their effective and safe delivery.

Identifying signatures of proteolytic stability and monomeric propensity in O-glycosylated insulin using molecular simulation

Insulin has been commonly adopted as a peptide drug to treat diabetes as it facilitates the uptake of glucose from the blood. The development of oral insulin remains elusive over decades owing to its susceptibility to the enzymes in the gastrointestinal tract and poor permeability through the intestinal epithelium upon dimerization. Recent experimental studies have revealed that certain O-linked glycosylation patterns could enhance insulin's proteolytic stability and reduce its dimerization propensity, but understanding such phenomena at the molecular level is still difficult. To address this challenge, we proposed and tested several structural determinants that could potentially influence insulin's proteolytic stability and dimerization propensity. We used these metrics to assess the properties of interest from [Formula: see text] aggregate molecular dynamics of each of 12 targeted insulin glyco-variants from multiple wild-type crystal structures. We found that glycan-involved hydrogen bonds and glycan-dimer occlusion were useful metrics predicting the proteolytic stability and dimerization propensity of insulin, respectively, as was in part the solvent-accessible surface area of proteolytic sites. However, other plausible metrics were not generally predictive. This work helps better explain how O-linked glycosylation influences the proteolytic stability and monomeric propensity of insulin, illuminating a path towards rational molecular design of insulin glycoforms.

Role of surface-exposed charged basic amino acids (Lys, Arg) and guanidination in insulin on the interaction and stability of insulin-insulin receptor complex

Naturally occurring proteins are emerging as novel therapeutics in the protein-based biopharmaceutical industry for the treatment of diabetes and obesity. However, proteins are not suitable for oral delivery due to short half-life, reduced physical and chemical stability and low permeability across the membrane. Chemical modification has been identified as a formulation strategy to enhance the stability and bioavailability of protein drugs. The present study aims to study the effect of charge-specific modification of basic amino acids (Lys, Arg) and guanidination on the interaction of insulin with its receptor using molecular modelling. Our investigation revealed that the guanidination of insulin (Lys-NHC = NHNH₂) enhanced and exerted stronger binding of the protein to its receptor through electrostatic interaction than native insulin (Lys-NH₃⁺). Point mutations of Lys and Arg (R22, K29; R22K, K29; R22, K29R; R22K, K29R) were attempted and the effects on the interaction and stability between insulin/modified insulins and insulin receptor were also analyzed in this study. The findings from the study are expected to provide a better understanding of the possible mechanism of action of the modified protein at a molecular level before advancing to real experiments.

An Update on Pharmaceutical Strategies for Oral Delivery of Therapeutic Peptides and Proteins in Adults and Pediatrics

While each route of therapeutic drug delivery has its own advantages and limitations, oral delivery is often favored because it offers convenient painless administration, sustained delivery, prolonged shelf life, and often lower manufacturing cost. Its limitations include mucus and epithelial cell barriers in the gastrointestinal (GI) tract that can block access of larger molecules including Therapeutic protein or peptide-based drugs (TPPs), resulting in reduced bioavailability. This review describes these barriers and discusses different strategies used to modify TPPs to enhance their oral bioavailability and/or to increase their absorption. Some seek to stabilize the TTPs to prevent their degradation by proteolytic enzymes in the GI tract by administering them together with protease inhibitors, while others modify TPPs with mucoadhesive polymers like polyethylene glycol (PEG) to allow them to interact with the mucus layer, thereby delaying their clearance. The further barrier provided by the epithelial cell membrane can be overcome by the addition of a cell-penetrating peptide (CPP) and the use of a carrier molecule such as a liposome, microsphere, or nanosphere to transport the TPP-CPP chimera. Enteric coatings have also been used to help TPPs reach the small intestine. Key efficacious TPP formulations that have been approved for clinical use will be discussed.

A comprehensive review of bioactive peptides obtained from animal byproducts and their applications

Livestock generates high quantities of residues, which has become a major socioeconomic issue for the meat industry. This review focuses on the identification of bioactive peptides (BPs) in animal byproducts and meat wastes. Firstly, the main bioactivities that peptides can have will be described and the methods for their evaluation will be discussed. Secondly, the various origins of these BPs will be studied. Then, the techniques and tools for the generation of BPs will be detailed in order to discuss, in the final part, how peptides could be used and assimilated. BPs possess diverse biological activities and can be strategic candidates for substituting synthetic molecules. In silico potentiality studies are a helpful tool to understand and predict BPs released from proteins and their potential activities. However, in vitro validation is often required. Although BP use is compelled by strict regulations in relation to the field of application, they are also limited by their low bioavailability and bioaccessibility. Therefore, it is important to test peptide stability during gastrointestinal digestion. Protective strategies have been discussed since their use could improve the stability and effectiveness of BPs.

Lipid nanoparticles as vehicles for oral delivery of insulin and insulin analogs: preliminary ex vivo and in vivo studies

AIMS

Subcutaneous administration of insulin in patients suffering from diabetes is associated with the distress of daily injections. Among alternative administration routes, the oral route seems to be the most advantageous for long-term administration, also because the peptide undergoes a hepatic first-pass effect, contributing to the inhibition of the hepatic glucose output. Unfortunately, insulin oral administration has so far been hampered by degradation by gastrointestinal enzymes and poor intestinal absorption. Loading in lipid nanoparticles should allow to overcome these limitations.

METHODS

Entrapment of peptides into such nanoparticles is not easy, because of their high molecular weight, hydrophilicity and thermo-sensitivity. In this study, this objective was achieved by employing fatty acid coacervation method: solid lipid nanoparticles and newly engineered nanostructured lipid carriers were formulated. Insulin and insulin analog-glargine insulin-were entrapped in the lipid matrix through hydrophobic ion pairing.

RESULTS

Bioactivity of lipid entrapped peptides was demonstrated through a suitable in vivo experiment. Ex vivo and in vivo studies were carried out by employing fluorescently labelled peptides. Gut tied up experiments showed the superiority of glargine insulin-loaded nanostructured lipid carriers, which demonstrated significantly higher permeation (till 30% dose/mL) compared to free peptide. Approximately 6% absolute bioavailability in the bloodstream was estimated for the same formulation through in vivo pharmacokinetic studies in rats. Consequently, a discrete blood glucose responsivity was noted in healthy animals.

CONCLUSIONS

Given the optimized ex vivo and in vivo intestinal uptake of glargine insulin from nanostructured lipid carriers, further studies will be carried out on healthy and diabetic rat models in order to establish a glargine insulin dose-glucose response relation.

Hydrogels For Peptide Hormones Delivery: Therapeutic And Tissue Engineering Applications

Peptides are the most abundant biological compounds in the cells that act as enzymes, hormones, structural element, and antibodies. Mostly, peptides have problems to move across the cells because of their size and poor cellular penetration. Therefore, a carrier that could transfer peptides into cells is ideal and would be effective for disease treatment. Until now, plenty of polymers, e.g., polysaccharides, polypeptides, and lipids were used in drug delivery. Hydrogels made from polysaccharides showed significant development in targeted delivery of peptide hormones because of their natural characteristics such as networks, pore sizes, sustainability, and response to external stimuli. The main aim of the present review was therefore, to gather the important usages of the hydrogels as a carrier in peptide hormone delivery and their application in tissue engineering and regenerative medicine.

Materials and methods for delivery of biological drugs

Biological drugs generated via recombinant techniques are uniquely positioned due to their high potency and high selectivity of action. The major drawback of this class of therapeutics, however, is their poor stability upon oral administration and during subsequent circulation. As a result, biological drugs have very low bioavailability and short therapeutic half-lives. Fortunately, tools of chemistry and biotechnology have been developed into an elaborate arsenal, which can be applied to improve the pharmacokinetics of biological drugs. Depot-type release systems are available to achieve sustained release of drugs over time. Conjugation to synthetic or biological polymers affords long circulating formulations. Administration of biological drugs through non-parenteral routes shows excellent performance and the first products have reached the market. This Review presents the main accomplishments in this field and illustrates the materials and methods behind existing and upcoming successful formulations and delivery strategies for biological drugs.

Challenges in the local delivery of peptides and proteins for oral mucositis management

Oral mucositis, a common inflammatory side effect of oncological treatments, is a disorder of the oral mucosa that can cause painful ulcerations, local motor disabilities, and an increased risk of infections. Due to the discomfort it produces and the associated health risks, it can lead to cancer treatment restrains, such as the need for dose reduction, cycle delays or abandonment. Current mucositis management has low efficiency in prevention and treatment. A topical drug application for a local action can be a more effective approach than systemic routes when addressing oral cavity pathologies. Local delivery of growth factors, antibodies, and anti-inflammatory cytokines have shown promising results. However, due to the peptide and protein nature of these novel agents, and the several anatomic, physiological and environmental challenges of the oral cavity, their local action might be limited when using traditional delivering systems. This review is an awareness of the issues and strategies in the local delivery of macromolecules for the management of oral mucositis.

Peptide Lipidation - A Synthetic Strategy to Afford Peptide Based Therapeutics

Peptide and protein aberrant lipidation patterns are often involved in many diseases including cancer and neurological disorders. Peptide lipidation is also a promising strategy to improve pharmacokinetic and pharmacodynamic profiles of peptide-based drugs. Self-adjuvanting peptide-based vaccines commonly utilise the powerful TLR2 agonist Pam_nCys lipid to stimulate adjuvant activity. The chemical synthesis of lipidated peptides can be challenging hence efficient, flexible and straightforward synthetic routes to access homogeneous lipid-tagged peptides are in high demand. A new technique coined Cysteine Lipidation on a Peptide or Amino acid (CLipPA) uses a 'thiol-ene' reaction between a cysteine and a vinyl ester and offers great promise due to its simplicity, functional group compatibility and selectivity. Herein a brief review of various synthetic strategies to access lipidated peptides, focusing on synthetic methods to incorporate a Pam_nCys motif into peptides, is provided.

Oral insulin delivery: existing barriers and current counter-strategies

Objectives

The chronic and progressive nature of diabetes is usually associated with micro- and macrovascular complications where failure of pancreatic β-cell function and a general condition of hyperglycaemia is created. One possible factor is failure of the patient to comply with and adhere to the prescribed insulin due to the inconvenient administration route. This review summarizes the rationale for oral insulin administration, existing barriers and some counter-strategies trialled.

Key findings

Oral insulin mimics the physiology of endogenous insulin secreted by pancreas. Following the intestinal absorption of oral insulin, it reaches the liver at high concentration via the portal vein. Oral insulin on the other hand has the potential to protect pancreatic β-cells from autoimmune destruction. Structural modification, targeting a particular tissue/receptor, and the use of innovative pharmaceutical formulations such as nanoparticles represent strategies introduced to improve oral insulin bioavailability. They showed promising results in overcoming the hurdles facing oral insulin delivery, although delivery is far from ideal.

Summary

The use of advanced pharmaceutical technologies and further research in particulate carrier system delivery predominantly nanoparticle utilization would offer useful tools in delivering insulin via the oral route which in turn would potentially improve diabetic patient compliance to insulin and the overall management of diabetes.

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.

A review on the strategies for oral delivery of proteins and peptides and their clinical perspectives

In the modern world, a number of therapeutic proteins such as vaccines, antigens, and hormones are being developed utilizing different sophisticated biotechnological techniques like recombinant DNA technology and protein purification. However, the major glitches in the optimal utilization of therapeutic proteins and peptides by the oral route are their extensive hepatic first-pass metabolism, degradation in the gastrointestinal tract (presence of enzymes and pH-dependent factors), large molecular size and poor permeation. These problems can be overcome by adopting techniques such as chemical transformation of protein structures, enzyme inhibitors, mucoadhesive polymers and permeation enhancers. Being invasive, parenteral route is inconvenient for the administration of protein and peptides, several research endeavors have been undertaken to formulate a better delivery system for proteins and peptides with major emphasis on non-invasive routes such as oral, transdermal, vaginal, rectal, pulmonary and intrauterine. This review article emphasizes on the recent advancements made in the delivery of protein and peptides by a non-invasive (peroral) route into the body.

Efficacy and safety of oral insulin compared to subcutaneous insulin: a systematic review and meta-analysis

INTRODUCTION

A systematic review and meta-analysis of interventional studies was conducted to compare the efficacy and safety of oral insulin versus subcutaneous (SC) insulin in diabetic patients.

METHODS

Medline, Scopus, ISI Web of Knowledge and Cochrane Central Register of Controlled Trials were searched. Two independent reviewers evaluated studies for eligibility and quality and extracted the data. The primary outcomes were fasting blood glucose (FBG), 1h and 2h postprandial blood glucose, HbA1c, AUC of insulin, C max and T max of insulin, and T max of glucose infusion rate. Secondary outcomes were adverse events.

RESULTS

Eleven studies (n = 373) met the inclusion criteria. Meta-analyses showed that there is no significant difference between oral and SC insulin in controlling HbA1c, FBG, 1 and 2 h postprandial blood glucose and producing C max of insulin (P > 0.05); however oral insulin had faster action as indicated by the shorter T max, compared to SC insulin (P < 0.05). The most included studies were varied in their methodological quality.

CONCLUSION

This systematic review and meta-analysis showed that oral insulin is comparable to SC insulin with regard to glycemic efficacy and safety. However, is necessary to conduct additional studies in which oral insulin administered to large number of patients for long enough periods of time.

Stabilization challenges and formulation strategies associated with oral biologic drug delivery systems

Delivery of proteins to mucosal tissues of GI tract typically utilize formulations which protect against proteolysis and target the mucosal tissues. Using case studies from literature and the authors' own work, the in-process stability and solid state storage stability of biopharmaceuticals formulated in delivery systems designed for oral delivery to the GI tract will be reviewed. Among the range of delivery systems, biodegradable polymer systems for protection and controlled release of proteins have been the most studied; hence these systems will be covered in greater depth. These delivery systems include polymeric biodegradable microspheres or nanospheres that contain proteins or vaccines, which are designed to reduce the number of administrations/inoculations and the total protein dose required to achieve the desired biological effect. Specifically, this review will include a landscape survey of the systems that have been studied, the manufacturing processes involved, stability through the manufacturing process, key pharmaceutical formulation parameters that impact stability of the encased proteins, and storage stability of the encapsulated proteins in these delivery systems.

The plant decapeptide OSIP108 prevents copper-induced apoptosis in yeast and human cells

We previously identified the Arabidopsis thaliana-derived decapeptide OSIP108, which increases tolerance of plants and yeast cells to oxidative stress. As excess copper (Cu) is known to induce oxidative stress and apoptosis, and is characteristic for the human pathology Wilson disease, we investigated the effect of OSIP108 on Cu-induced toxicity in yeast. We found that OSIP108 increased yeast viability in the presence of toxic Cu concentrations, and decreased the prevalence of Cu-induced apoptotic markers. Next, we translated these results to the human hepatoma HepG2 cell line, demonstrating anti-apoptotic activity of OSIP108 in this cell line. In addition, we found that OSIP108 did not affect intracellular Cu levels in HepG2 cells, but preserved HepG2 mitochondrial ultrastructure. As Cu is known to induce acid sphingomyelinase activity of HepG2 cells, we performed a sphingolipidomic analysis of OSIP108-treated HepG2 cells. We demonstrated that OSIP108 decreased the levels of several sphingoid bases and ceramide species. Moreover, exogenous addition of the sphingoid base dihydrosphingosine abolished the protective effect of OSIP108 against Cu-induced cell death in yeast. These findings indicate the potential of OSIP108 to prevent Cu-induced apoptosis, possibly via its effects on sphingolipid homeostasis.

Systemic delivery of biotherapeutics through the lung: opportunities and challenges for improved lung absorption

The development of Exubera(®) (inhaled insulin) has paved the way for consideration of future inhaled biotherapeutic products for systemic delivery. This route of drug delivery favors highly potent small peptides without self-association and large proteins resistant to enzymatic degradation for high bioavailability, while likely resulting in transient therapeutic effects. Improved therapeutic benefits with a needle-free delivery, such as inhaled insulin, are also rational pursuits. Molecules and their formulations must be carefully chosen and designed to optimize the rates of lung absorption and nonabsorptive loss. Novel molecular or formulation approaches, for example, Technosphere(®), Fc-/scFv-fusion protein, PEGylation, polymeric or lipid-based micro/nanoparticles and liposomes, offer opportunities to improve lung absorption and therapeutic duration of some biotherapeutics. Critical assessments are now essential as to their therapeutic benefits, safety, patient acceptance and market competition, as carried out for Exubera.

Oral drug delivery systems using chemical conjugates or physical complexes

Oral delivery of therapeutics is extremely challenging. The digestive system is designed in a way that naturally allows the degradation of proteins or peptides into small molecules prior to absorption. For systemic absorption, the intact drug molecules must traverse the impending harsh gastrointestinal environment. Technologies, such as enteric coating, with oral dosage formulation strategies have successfully provided the protection of non-peptide based therapeutics against the harsh, acidic condition of the stomach. However, these technologies showed limited success on the protection of therapeutic proteins and peptides. Importantly, inherent permeability coefficient of the therapeutics is still a major problem that has remained unresolved for decades. Addressing this issue in the context, we summarize the strategies that are developed in enhancing the intestinal permeability of a drug molecule either by modifying the intestinal epithelium or by modifying the drug itself. These modifications have been pursued by using a group of molecules that can be conjugated to the drug molecule to alter the cell permeability of the drug or mixed with the drug molecule to alter the epithelial barrier function, in order to achieve the effective drug permeation. This article will address the current trends and future perspectives of the oral delivery strategies.

Strategies for enhanced peptide and protein delivery

Recent advances in the fields of molecular biology and biotechnology have allowed for the large-scale production and subsequent exploitation of the therapeutic potential of protein- and peptide-based drugs. The facilitation of delivery of this class of drugs must be tailored to meet the requirements and often the limitations dictated by the route of delivery chosen. The aim of this review is to comprehensively discuss several routes of drug delivery, detailing the uses and exploitation of each, from origins to present day approaches. Specific reference is made to the compatibility or incompatibility of each approach in the facilitation of the delivery of drugs of protein origin. Additionally, the physiological nature of the delivery route and the inherent physiological obstacles that must be considered when determining the most suitable approach to drug design and delivery enhancement are also addressed. Examples of novel protein-based drug designs and delivery methodologies that illustrate such enhancement strategies are explored.

Approaches for enhancing oral bioavailability of peptides and proteins

Oral delivery of peptide and protein drugs faces immense challenge partially due to the gastrointestinal (GI) environment. In spite of considerable efforts by industrial and academic laboratories, no major breakthrough in the effective oral delivery of polypeptides and proteins has been accomplished. Upon oral administration, gastrointestinal epithelium acts as a physical and biochemical barrier for absorption of proteins resulting in low bioavailability (typically less than 1-2%). An ideal oral drug delivery system should be capable of (a) maintaining the integrity of protein molecules until it reaches the site of absorption, (b) releasing the drug at the target absorption site, where the delivery system appends to that site by virtue of specific interaction, and (c) retaining inside the gastrointestinal tract irrespective of its transitory constraints. Various technologies have been explored to overcome the problems associated with the oral delivery of macromolecules such as insulin, gonadotropin-releasing hormones, calcitonin, human growth factor, vaccines, enkephalins, and interferons, all of which met with limited success. This review article intends to summarize the physiological barriers to oral delivery of peptides and proteins and novel pharmaceutical approaches to circumvent these barriers and enhance oral bioavailability of these macromolecules.

Opportunities and challenges for oral delivery of hydrophobic versus hydrophilic peptide and protein-like drugs using lipid-based technologies

Peptide and protein-like drugs are macromolecules currently produced in increasing numbers by the pharmaceutical biotechnology industry. The physicochemical properties of these molecules pose barriers to oral administration. Lipid-based drug-delivery systems have the potential to overcome these barriers and may be utilized to formulate safe, stable and efficacious oral medicines. This review outlines the design of such lipid-based technologies. The mechanisms whereby these formulations enhance the absorption of lipophilic versus hydrophilic peptide and protein-like drugs are discussed. In the case of lipophilic compounds, the advantages of lipid-based drug-delivery systems including increased solubilization, decreased intestinal efflux, decreased intracellular metabolism and possible lymphatic transport are well established as is evident from the success of Neoral® and other drug products on the market. In contrast, with respect to hydrophilic compounds, the situation is more complex and, while promising formulation approaches have been studied, issues including reproducibility of response, intersubject variability and duration of response require further optimization before commercially viable products are possible.

Hydrophobic ion pairing of an insulin-sodium deoxycholate complex for oral delivery of insulin

Insulin was complexed with sodium deoxycholate to form an insulin-sodium deoxycholate complex (Ins-SD-Comp) using an hydrophobic ion pairing method in aqueous phase to enhance the liposolubility of insulin. In order to obtain the maximal complexation efficiency, the molar ratio of sodium deoxycholate to insulin was found. The zeta potential method was used to confirm the optimal ratio for formation of Ins-SD-Comp. The structural characteristics of Ins-SD-Comp were assessed using the Fourier transform infrared method. The apparent partition coefficient of insulin increased upon the formation of Ins-SD-Comp. Based on the preliminary study, Ins-SD-Comp was encapsulated into poly(lactide-co-glycolide) (PLGA) nanoparticles using an emulsion solvent diffusion method. The maximal encapsulation efficiency of Ins-SD-Comp into PLGA nanoparticles was 93.6% ± 2.81%, drug loading was about 4.8% ± 0.32%, and the mean diameter of the nanoparticles was 278 ± 13 nm. Biological activity and in vivo results revealed that the bioactivity of insulin was not destroyed during the preparation process. Ins-SD-Comp-loaded PLGA nanoparticles have the potential to reduce serum glucose levels and increase the oral bioavailability of insulin.

Effect of camel milk on glycemic control and insulin requirement in patients with type 1 diabetes: 2-years randomized controlled trial

BACKGROUND/OBJECTIVES

Hypoglycemic effect of camel milk supplementation in experimental rat model and significant reduction in doses of insulin in type 1 diabetic patients have been observed in our previous studies. This long-term study was undertaken to assess the efficacy, safety and acceptability of camel milk as an adjunct to insulin therapy in type 1 diabetics.

SUBJECTS/METHODS

In this 2-year randomized clinical, parallel design study, 24 type 1 diabetics were enrolled and divided into two groups. Group I (n=12) received usual care, that is, diet, exercise and insulin and Group II (n=12) received 500 ml camel milk in addition to the usual care. Insulin requirement was titrated weekly by blood glucose estimation. Results were analyzed by using the regression technique.

RESULTS

In camel milk group, there was decrease in mean blood glucose (118.58±19-93.16±17.06 mg/dl), hemoglobin A1c levels (7.81±1.39-5.44±0.81%) and insulin doses (32.50±9.99-17.50±12.09 U/day, P<0.05). Out of 12 subjects receiving camel milk, insulin requirement in 3 subjects reduced to zero. There was nonsignificant change in plasma insulin and anti-insulin antibodies in both the groups.

CONCLUSION

It may be stated that camel milk is safe and efficacious in improving long-term glycemic control, with a significant reduction in the doses of insulin in type 1 diabetic patients.

A discrete choice experiment evaluation of patients' preferences for different risk, benefit, and delivery attributes of insulin therapy for diabetes management

OBJECTIVE

To evaluate patients' preferences for various attributes of insulin treatment, including route of insulin delivery.

METHODS

We used a discrete choice experiment (DCE) to quantify patients' preferences. The attributes (and levels) included in the DCE questionnaire were: glucose control, frequency of hypoglycemic events, weight gain, route of administration for the long-acting and the short-acting insulin, and out-of-pocket cost. Data were analyzed using conditional logit regression and segmented models were also developed to evaluate differences in preferences between subgroups.

RESULTS

Two hundred and seventy-four questionnaires were completed. The mean age (SD) of participants was 56.7 (12.9) years. Forty-nine percent of participants were insulin users, and 17% had type 1 diabetes. Overall, patients' ideal insulin treatment would provide better glucose control, result in fewer adverse reactions, have the lowest cost, and be administered orally. Overall, there was a strong positive preference for better glucose control relative to the other attributes. Segmented analyses by insulin use and type of diabetes suggest that there may be an important psychosocial barrier to initiating insulin therapy but that patients tend to adjust to subcutaneous administration once they initiate therapy.

CONCLUSIONS

This study illustrates the importance that patients with diabetes place on glucose control and how preferences for insulin therapy differ between subgroups. Specifically, efforts need to be made to overcome the psychosocial barriers to initiating insulin therapy which may lead to improved control through improved treatment acceptance and ultimately improve patients' quality of life and reduce the economic burden of the disease.

Oral insulin

Oral insulin is an exciting area of research and development in the field of diabetology. This brief review covers the various approaches used in the development of oral insulin, and highlights some of the recent data related to novel oral insulin preparation.

Exploring patients' perceptions for insulin therapy in type 2 diabetes: a Brazilian and Canadian qualitative study

Objective:

To explore which attributes of insulin therapy drive patients’ preferences for management in Canada and Brazil.

Methods:

A qualitative design was implemented in which a total of 32 patients with type 2 diabetes from Canada and Brazil, were interviewed in one of the 4 focus groups, or 16 individual interviews. Eighteen participants (56%) were women and fourteen participants (44%) were men (15 insulin nonusers and 17 insulin users). Two focus groups of 4 participants each and 9 individual interviews were conducted in Brazil. In Canada, 2 focus groups of 4 participants each and 7 individual interviews were conducted. A framework analysis was used to analyse all data.

Results:

Brazilian participants, when considering two insulin treatments, would prefer the one that had fewer side-effects (specially hypoglycemia events), was noninjectable, had the lowest cost and was most effective. Meanwhile, Canadian participants would prefer a treatment that had fewer side-effects (specially weight gain), was less invasive, was more convenient and was most effective.

Conclusions:

Finding the insulin-delivery system and the attributes of insulin therapy that best meet patients’ preferences may lead to improved control, through improved compliance, which may ultimately reduce the financial burden of the disease and improve quality of life.

Oral insulin - a review of current status

Oral insulin is one of the most exciting areas of development in the treatment of diabetes because of its potential benefit in patient convenience, rapid insulinization of liver, adequate insulin delivery avoiding peripheral hyperinsulinaemia while potentially avoiding adverse effects of weight gain and hypoglycaemia. Growing evidence that earlier initiation of intensive insulin therapy produces sustained tight glycaemic control resulting in substantial delay in complications makes an effective oral insulin product even more vital for the management of patients with diabetes. Despite knowledge of this unmet medical need, oral delivery of insulin has been unsuccessful because of several barriers. For several decades, researchers have tried to develop oral insulin using various technologies without much clinical or commercial success. This review summarizes the development status of oral insulins which are publicly reported to be undergoing clinical studies. Currently, two oral insulin products are in an advanced stage of clinical development and first data from long-term therapy are expected to be available in the second half of 2010.

A valuation of patients' willingness-to-pay for insulin delivery in diabetes

OBJECTIVES

The aim of this study was to determine the insulin-delivery system and the attributes of insulin therapy that best meet patients' preferences, and to estimate patients' willingness-to-pay (WTP) for them.

METHODS

This was a cross-sectional discrete choice experiment (DCE) study involving 378 Canadian patients with type 1 or type 2 diabetes. Patients were asked to choose between two hypothetical insulin treatment options made up of different combinations of the attribute levels. Regression coefficients derived using conditional logit models were used to calculate patients' WTP. Stratification of the sample was performed to evaluate WTP by predefined subgroups.

RESULTS

A total of 274 patients successfully completed the survey. Overall, patients were willing to pay the most for better blood glucose control followed by weight gain. Surprisingly, route of insulin administration was the least important attribute overall. Segmented models indicated that insulin naïve diabetics were willing to pay significantly more for both oral and inhaled short-acting insulin compared with insulin users. Surprisingly, type 1 diabetics were willing to pay $C11.53 for subcutaneous short-acting insulin, while type 2 diabetics were willing to pay $C47.23 to avoid subcutaneous short-acting insulin (p < .05). These findings support the hypothesis of a psychological barrier to initiating insulin therapy, but once that this barrier has been overcome, they accommodate and accept injectable therapy as a treatment option.

CONCLUSIONS

By understanding and addressing patients' preferences for insulin therapy, diabetes educators can use this information to find an optimal treatment approach for each individual patient, which may ultimately lead to improved control, through improved compliance, and better diabetes outcomes.

Oral insulin and buccal insulin: a critical reappraisal

Despite the availability of modern insulin injection devices with needles that are so sharp and thin that practically no injection pain takes place, it is still the dream of patients with diabetes to, for example, swallow a tablet with insulin. This is not associated with any pain and would allow more discretion. Therefore, availability of oral insulin would not only ease insulin therapy, it would certainly increase compliance. However, despite numerous attempts to develop such a "tablet" in the past 85 years, still no oral insulin is commercially available. Buccal insulin is currently in the last stages of clinical development by one company and might become available in the United States and Europe in the coming years (it is already on the market in some other countries). The aim of this review is to critically describe the different approaches that are currently under development. Optimal coverage of prandial insulin requirements is the aim with both routes of insulin administration (at least with most approaches). The speed of onset of metabolic effect seen with some oral insulin approaches is rapid, but absorption appears to be lower when the tablet is taken immediately prior to a meal. With all approaches, considerable amounts of insulin have to be applied in order to induce therapeutically relevant increases in the metabolic effect because of the low relative biopotency of buccal insulin. Unfortunately, the number of publications about clinical-experimental and clinical studies is surprisingly low. In addition, there is no study published in which the variability of the metabolic effect induced (with and without a meal) was studied adequately. In summary, after the failure of inhaled insulin, oral insulin and buccal insulin are hot candidates to come to the market as the next alternative routes of insulin administration.

Improved intestinal delivery of salmon calcitonin by Lys18-amine specific PEGylation: stability, permeability, pharmacokinetic behavior and in vivo hypocalcemic efficacy

Peptides like salmon calcitonin (sCT) are subjected to aggressive proteolytic attack by various intestinal enzymes, and fractions that enter the systemic circulation via the intestinal route are rapidly inactivated by tissue accumulation and glomerular filtration. Here, we describe the beneficial effects of the Lys(18)-amine specific PEGylation of sCT on the intestinal delivery of sCT. Two key properties were enhanced by the PEGylation process: (i) the resistance of sCT to intestinal enzymes and (ii) the systemic clearance of sCT that had entered the circulation. Initially, we evaluated the cAMP-secreting activities of PEG(2K)-sCT isomers substituted at Cys(1)-, Lys(11)- or Lys(18)-amine position in T47D cells, and found that sCT PEGylated at Lys(18)-amine (Lys(18)-PEG(2K)-sCT) had the highest bioactivity. We then investigated the stability of Lys(18)-PEG(2K)-sCT in the presence of intestinal enzymes, its abilities to traverse the intestinal membrane, its pharmacokinetic behavior and in vivo hypocalcemic efficacy. Results show that Lys(18)-PEG(2K)-sCT has significantly increased resistance to pancreatic peptidases and brush-border peptidases. Despite the molecular size increase caused by PEGylation, Lys(18)-PEG(2K)-sCT was found to have an intestinal permeability similar to that of unmodified sCT (p>0.59) over an apical concentration range 12.5-100 microM in a Caco-2 cell monolayer transport system. In particular, tissue distribution results showed that (125)I-labeled Lys(18)-PEG(2K)-sCT markedly resists liver accumulation and glomerular filtration; levels were reduced by 75% and 50% vs. sCT. Finally, the hypocalcemic efficacy of intestinally administered Lys(18)-PEG(2K)-sCT, measured as total serum calcium in a rat model, was 5.8 and 3.0 times that of sCT at 100 and 200 IU/kg (p<0.025). Our findings suggest that this site-specific conjugation of peptides with PEG of proper size enhances pharmacokinetic properties by increasing their abilities to resist both proteolysis and systemic clearance without significantly reducing their membrane permeabilities or bioactivities. We believe that this concept, namely, dual effects by PEGylation, has great potential value because it presents a practical means of enhancing the efficacies of the peroral/intestinal pharmacologic route.

Strategies to improve oral drug bioavailability

Efforts to improve oral drug bioavailability have grown in parallel with the pharmaceutical industry. As the number and chemical diversity of drugs has increased, new strategies have been required to develop orally active therapeutics. The past two decades have been characterised by an increased understanding of the causes of low bioavailability and a great deal of innovation in oral drug delivery technologies, marked by an unprecedented growth of the drug delivery industry. The advent of biotechnology and consequent proliferation of biopharmaceuticals have brought new challenges to the drug delivery field. In spite of the difficulties associated with developing oral forms of this type of therapeutics, significant progress has been made in the past few years, with some oral proteins, peptides and other macromolecules currently advancing through clinical trials. This article reviews the approaches that have been successfully applied to improve oral drug bioavailability, primarily, prodrug strategies, lead optimisation through medicinal chemistry and formulation design. Specific strategies to improve the oral bioavailability of biopharmaceuticals are also discussed.

Insulin Therapy: Current Alternatives

In normal humans, blood glucose and insulin are maintained within a narrow range despite wide variations in physical activity and dietary intake. At present, reproducing this pattern is an impossible task in type 1 diabetes and extremely difficult in type 2 DM. New approaches using novel insulin analogs and routes of administration, attempting to replicate physiological insulin secretion in diabetic patients, are improving the profiles of glucose levels and, thus, the quality of life. Ultra-short-acting insulin analogues and ultra-long-acting analogues are being used for prandial and basal effects with better results, lower prevalence of hypoglycemia, and, hopefully, fewer chronic complications. Non-invasive routes of administration are being developed. The most promising appears to be inhaled insulin according to studies demonstrating excellent control, apparently without significant side effects, although in relatively short-term trials. Longer-term studies to assure the safety are still necessary before recommending its extended use. This is an extensive, up-to-date review of recent advances in insulin therapy.

Novel pharmacologic agents for type 2 diabetes

After many decades of relative therapeutic stagnation since the initial discovery of insulin, followed by some modifications on its structure and only having sulfonylureas and biguanides for many years, the last decade has seen a surge in new therapeutic options for the management of diabetes. The results of the United Kingdom Prospective Diabetes Study and Kumamoto study indicate the need for aggressive glycemic control and the slow inexorable clinical deterioration associated with type 2 diabetes overtime. The propensity for weight gain and hypoglycemia are the two major limitations that subcutaneous insulin and sulfonylureas have been particularly prone to. The newer antidiabetic medications and those on the horizon attempt to address these limitations. GLP-1 agonists and the DPP-IV inhibitors exploit the innate incretin system to improve glycemia while promoting satiety and weight management. Like GLP-1 related compounds, pramlintide offers the potential to address postprandial hyperglucagonemia associated with type 2 diabetes only limited by the multiple injections and gastrointestinal side effects. The glitazars offer the hope ofa new approach to diabetes care addressing not just glycemia, but dyslipidemia and other components of the metabolic syndrome, though the side effect profile remains a major unknown. The INGAP peptide represents the holy grail of diabetes care as it offers the potential of a new paradigm: that of islet regeneration and potential for a cure. But at this stage, with no human data available, it remains highly speculative. Beyond these and other novel agents being developed to meet the challenge of the worldwide epidemic of diabetes, the central place of insulin in diabetes care cannot be forgotten. In view of this the continued efforts of improvement in insulin delivery, kinetics and action have spurred such innovations as the various inhaled insulins and new insulin analogues. There is cause for guarded optimism and excitement about the years ahead. There is reason to expect that despite the growing burden of diabetes worldwide, we will be better equipped to manage it and its comorbidities and prevent its onset and possibly even cure it.

A new drug carrier, Nalpha-deoxycholyl-L: -lysyl-methylester, for enhancing insulin absorption in the intestine

AIMS/HYPOTHESIS

The development of an orally active insulin formulation will offer great advantages over conventional injectable insulin therapy in the treatment of patients with diabetes mellitus. Since insulin absorption in the intestine is restricted by the natural physiological characteristics of insulin, we developed a small synthetic compound, Nalpha-deoxycholyl-L: -lysyl-methylester (DCK), as an insulin carrier to enhance oral delivery.

METHODS

Streptozotocin-induced diabetic rats orally received single doses of insulin (42 U/kg) or insulin/DCK formulation (10, 21, 30 and 42 U/kg) under fasting conditions. Blood glucose levels and plasma insulin concentrations were measured for 6 h following the administration of the agents. An OGTT was also performed immediately after the administration of the oral insulin/DCK formulation.

RESULTS

The administration of 21, 30 and 42 U/kg (based on insulin activity) of insulin/DCK formulation reduced plasma glucose levels by up to 33.0% (median; range 30.6-70.2%), 78.5% (39.4-86.8%) and 75.2% (67.0-87.4%), respectively, compared with baseline levels. Furthermore, plasma insulin concentrations were observed to rapidly increase. In the OGTT, the insulin/DCK formulation reduced the AUC0-240 for glucose by 30.8% (22.3-54.9%) (p<0.01), and stabilized glycaemia for up to 4 h.

CONCLUSIONS/INTERPRETATION

The results of this study demonstrate that the insulin/DCK formulation can be absorbed in the intestine and that it is biologically efficacious. We therefore suggest that this oral formulation could be used as an alternative to injectable insulin with enhanced clinical effects.

A Critical Appraisal of the Role of Insulin Analogues in the Management of Diabetes Mellitus

Insulin is one of the oldest and best studied treatments for diabetes mellitus. Despite many improvements in the management of diabetes, the nonphysiological time-action profiles of conventional insulins remain a significant obstacle. However, the advent of recombinant DNA technology made it possible to overcome these limitations in the time-action profiles of conventional insulins. Used as prandial (e.g. insulin lispro or insulin aspart) and basal (e.g. insulin glargine) insulin, the analogues simulate physiological insulin profiles more closely than the older conventional insulins. If rapid-acting insulin analogues are used in the hospital, healthcare providers will need a new mind-set. Any error in coordination between timing of rapid-acting insulin administration and meal ingestion may result in hypoglycaemia. However, guidelines regarding in-hospital use of insulin analogues are few. The safety profile of insulin analogues is still not completely established in long-term clinical studies. Several studies have shown conflicting results with respect to the tumourigenic potential of this new class of agents. The clinical implications of these findings are not clear. Although novel insulin analogues are promising 'designer drugs' in our armamentarium to overcome some of the limitations of conventional insulin therapy, cost may be a limiting factor for some patients.

Future therapy of diabetes mellitus

For reaching near normal glycemic control, multiple daily insulin injections are necessary, although subcutaneous insulin therapy cannot get the physiological profile, results in hypoglycemia, weight gain, peripheral hyperinsulinemia, and may not be accepted for painful injections. Glucagon-like peptide 1(GLP-1) analogs and alternative routes of insulin, especially oral (enteric-gastrointestinal, inhaled) route, are most promising and attractive now. Biotechnology and biochemistry will make it possible to overcome several disadvantages of low absorption, short half-life, low bioavailability, and many clinical trials are now in progress. We will show the review of these drugs and another candidate for the treatment of diabetic complications, protein kinase C inhibitor.

Reducing injection pain in children and adolescents with diabetes: a review of indwelling catheters

Most children and adolescents find the pain when injecting insulin quite minimal but still significantly more painful than a placebo injection. However, injection pain and needle phobia are major problems for a small number of patients, even after many years of diabetes. Needle diameter is of less importance for the experienced pain. The use of indwelling catheters (Insuflon, Unomedical, Lynge, Denmark) for introducing insulin injections at the onset of diabetes results in an evident relief of preinjection anxiety, injection problems, and the procedural pain of repeated injections. The average indwelling time is 3-5 d. Fixation problems and local redness at the insertion site are the most frequent side effects. However, the frequency is low and they can be dealt with effectively. Needles of 8-10 mm should be used for injecting to avoid penetration of the tubing of the catheter. Using indwelling catheters for up to 4-5 d does not affect the absorption of insulin, when the catheter is inserted in an area free from lipohypertrophies. The long-term (measured by hemoglobin A1c) and short-term metabolic control (measured by blood glucose profiles and serum-free insulin) is not altered. Using this type of injection aid may decrease the risk of future injection problems, such as needle phobia, in very select patients. In conclusion, indwelling catheters can safely be used from the onset of diabetes to lessen injection pain in children and adolescents, and may facilitate the use of intensive insulin therapy in this age group.