Oral modified insulin (HIM2) in patients with type 1 diabetes mellitus: results from a phase I/II clinical trial

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.

Role of lipid nanocarriers for enhancing oral absorption and bioavailability of insulin and GLP-1 receptor agonists

Growing demand for insulin and glucagon-like peptide-1 receptor agonists (GLP-1 RA) is observed, considering the progressive nature of diabetes and the potential therapeutic role of peptides in its treatment. However, chronic parenteral administration is responsible for pain and rashes at the site of injection. Oral delivery of insulin and GLP-1 RA promises better patient compliance owing to their ease of administration and reduction in chances of peripheral hypoglycaemia and weight gain. The review article discusses the potential of lipid carriers in combination with different strategies such as absorption enhancers, PEGylation, lipidisation, etc. The lipid nanocarriers improve the membrane permeability and oral bioavailability of high molecular weight peptides. Additionally, the clinical status of different nanocarriers for anti-diabetic peptides is discussed. Previous research on nanocarriers showed significant hypoglycaemic activity and safety in animal studies; however, extrapolation of the same in human subjects is not validated. With the rising global burden of diabetes, the lipid nanocarriers show the potential to revolutionise treatment with oral delivery of insulin and GLP-1 RA.

Immense Insulin Intestinal Uptake and Lymphatic Transport Using Bile Acid Conjugated Partially Uncapped Liposome

We provide immense insulin absorption from the gastrointestinal tract, combining apical sodium-dependent bile acid transporter-mediated intestinal uptake and the lymphatic transport pathway. This strategy has proven to employ chondroitin sulfate- g-taurocholic acid coated, insulin-loaded partially uncapped liposome (IPUL-CST) for type 1 diabetes mellitus (T1DM) treatment. The loading efficiency of insulin in IPUL-CST increased significantly from 33% to 75% via the partially uncapped liposome preparation method. Moreover, the IPUL-CST revealed an improved insulin protection efficacy in GIT simulated pH and digestive enzyme conditions. The high dose of IPUL-CST in the small intestine was detected 4 h post-oral administration using ex vivo optical imaging and fluorescence intensity. The IPUL-CST exhibited significantly enhanced intestinal absorption (oral bioavailability, 34%; T_max, 9 h) and reduced blood glucose levels for 16 h in T1DM. The results demonstrated that the new investigated IPUL-CST is a promising carrier for oral insulin delivery.

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.

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.

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.

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.

Diabetes Mellitus: New Challenges and Innovative Therapies

Diabetes is a common chronic disease affecting an estimated 285 million adults worldwide. The rising incidence of diabetes, metabolic syndrome, and subsequent vascular diseases is a major public health problem in industrialized countries. This chapter summarizes current pharmacological approaches to treat diabetes mellitus and focuses on novel therapies for diabetes mellitus that are under development.

There is great potential for developing a new generation of therapeutics that offer better control of diabetes, its co-morbidities and its complications. Preclinical results are discussed for new approaches including AMPK activation, the FGF21 target, cell therapy approaches, adiponectin mimetics and novel insulin formulations. Gene-based therapies are among the most promising emerging alternatives to conventional treatments. Therapies based on gene silencing using vector systems to deliver interference RNA to cells (i.e. against VEGF in diabetic retinopathy) are also a promising therapeutic option for the treatment of several diabetic complications.

In conclusion, treatment of diabetes faces now a new era that is characterized by a variety of innovative therapeutic approaches that will improve quality of life in the near future.

New technologies for diabetes: a review of the present and the future

This review summarizes the technologies in use and in the pipeline for the management of diabetes. The review focuses on glucose meters, continuous glucose monitoring devices, insulin pumps, and getting clinicians connected to technologies. All information presented can be found in the public domain, and was obtained from journal articles, websites, product review tables in patient publications, and professional conferences. The technology concerns, ongoing development and future trends in this area are also discussed.

Peptide therapeutics: it's all in the delivery

Recent work has demonstrated that the route of administration affects the pharmacokinetics and biological activity of peptides. For example, the physiological profile of insulin consists of basal and prandial components with a small-scale oscillatory element. Insulin is used more efficiently when the pharmacokinetic profile mimics features of physiological release. Noninvasive administration of insulin by oral, transdermal, nasal and pulmonary routes resembles the relatively sharp peak and short duration of exposure of prandial release. The route of administration per se, can affect the response by avoiding first-pass metabolism or perhaps altering the timing in which the peptide reaches different sets of receptors. GLP-I delivered by injection and inhalation produces different side effect profiles. Nonclinical studies on two potential treatments for obesity, oxyntomodulin and PYY 3-36, are also presented to illustrate the relationship between exposure and effect as functions of route of administration.

The use of polyion complex micelles to enhance the oral delivery of salmon calcitonin and transport mechanism across the intestinal epithelial barrier

The objective of the present study was to demonstrate the effect of polyanionic copolymer mPEG-grafted-alginic acid (mPEG-g-AA)-based polyion complex (PIC) micelles on enhancing the oral absorption of salmon calcitonin (sCT) in vivo and in vitro and identify the transepithelial transport mechanism of PIC micelles across the intestinal barrier. mPEG-g-AA was first successfully synthesized and characterized in cytotoxicity. The PIC micelles were approximately of 72 nm in diameter with a narrow distribution. The extremely significant enhancement of hypocalcemia efficacy of sCT-loaded PIC micelles in rats was evidenced by intraduodenal administration in comparison with sCT solution. The presence of mPEG-grafted-chitosan in PIC micelles had no favorable effect on this action in the referred content. In the Caco-2 transport studies, PIC micelles could significantly increase the permeability of sCT across Caco-2 monolayers without significantly affecting transepithelial electrical resistance values during the transport study. No evident alterations in the F-actin cytoskeleton were detected by confocal microscope observation following treatment of the cell monolayers with PIC micelles, which further certified the incapacity of PIC micelles to open the intercellular tight junctions. In addition, TEM observations showed that the intact PIC micelles were transported across the everted gut sac. These suggested that the transport of PIC micelles across Caco-2 cell monolayers involve a predominant transcytosis mechanism via endocytosis rather than paracellular pathway. Furthermore, PIC micelles were localized in both the cytoplasm and the nuclei observed by CLSM. Therefore, PIC micelles might be a potentially applicable tool for enhancing the oral absorption of cationic peptide and protein drugs.

Polymer-based oral peptide nanomedicines

Oral peptide delivery has been one of the major challenges of pharmaceutical sciences as it could lead to a great improvement of classical therapies, such as insulin, alongside making an important number of new therapies feasible. Successful oral delivery needs to fulfill two key tasks: to protect the macromolecules from degradation in the GI tract and to shuttle them across the intestinal epithelium in a safe and efficient fashion. Over the last decade, there have been numerous approaches based on the chemical modification of peptides and on the use of permeation enhancers, enzyme inhibitors and drug-delivery systems. Among the approaches developed to overcome these restrictions, the design of nanocarriers seems to be a particularly promising approach. This article is an overview on the state of the art of oral-peptide formulation strategies, with special attention to insulin delivery and the use of polymeric nanocarriers as delivery systems.

The oral delivery of proteins using interpolymer polyelectrolyte complexes

In spite of the numerous barriers inherent in the oral delivery of therapeutically active proteins, research into the development of functional protein-delivery systems is still intense. The effectiveness of such oral protein-delivery systems depend on their ability to protect the incorporated protein from proteolytic degradation in the GI tract and enhance its intestinal absorption without significantly compromising the bioactivity of the protein. Among these delivery systems are polyelectrolyte complexes (PECs) which are composed of polyelectrolyte polymers complexed with a protein via coulombic and other interactions. This review will focus on the current status of PECs with a particular emphasis on the potential and limitations of multi- or inter-polymer PECs used to facilitate oral protein delivery.

Design, synthesis, characterization and in-vivo activity of a novel salmon calcitonin conjugate containing a novel PEG-lipid moiety

Objectives

The aim of the study was to explore (1) the synthesis of a novel poly(ethylene glycol) modified lipid (PEG-lipid, PL) containing a chemically active tri-block linker, ε-maleimido lysine (Mal), and its conjugation with salmon calcitonin (sCT), and (2) the biophysical properties and activity of the resulting conjugate, Mal-PL-sCT, relative to the control, 2PEG-Mal-sCT, which comprises sCT conjugated with α-palmitoyl-N-ε-maleimido-l-lysine at cysteine 1 and cysteine 7, and PEG moieties at lysine 11 and lysine 18 via a conventional stepwise method.

Methods

The PEG-lipid was obtained by condensing palmitic acid derivative of ε-maleimido lysine with methoxy poly(ethylene glycol) amine. Under reductive conditions, the PEG-lipid readily reacted with sCT to yield the resultant compound, Mal-PL-sCT.

Key findings

Dynamic light scattering analyses suggested that Mal-PL-sCT and 2PEG-Mal-sCT exhibited robust helical structures with a high tendency to aggregate in water. Both compounds were more stable against intestinal degradation than sCT, although Mal-PL-sCT was less stable than 2PEG-Mal-sCT. However, 2PEG-Mal-sCT did not possess hypocalcaemic activity while Mal-PL-sCT retained the hypocalcaemic activity of sCT when it was subcutaneously injected in the rat model. Multiple functional groups may be conjugated to a peptide via a tri-block linker without the risk of obliterating the intrinsic bioactivity of the peptide.

Conclusions

The resultant novel PEG-lipid has a potential role to optimize protein and peptide delivery.

Poly(epsilon-caprolactone)/eudragit nanoparticles for oral delivery of aspart-insulin in the treatment of diabetes

Nanoparticles prepared with a blend of a biodegradable polyester (poly(epsilon-caprolactone)) and a polycationic nonbiodegradable acrylic polymer (Eudragit RS) have been used as a drug carrier for oral administration of a short-acting insulin analogue, aspart-insulin. Insulin-loaded nanoparticles, about 700 nm in diameter, encapsulated 97.5% of insulin and were able to release about 70% of their content in vitro in a neutral medium over 24 h. When administered orally to diabetic rats, insulin-loaded nanoparticles (50 IU/kg) decreased fasted glycemia for a prolonged period of time and improved the glycemic response to glucose in a time-dependent manner, with a maximal effect between 12 and 24 h after their administration. In parallel, plasma insulin levels increased. However, higher (100 IU/kg) and lower (25 IU/kg) doses of insulin did not exert any biological effect. It is concluded that polymeric nanoparticles composed of poly(epsilon-caprolactone)/Eudragit RS are able to preserve the biological activity of the insulin analogue aspart-insulin; however, the postprandial peak suppression was prolonged more than 24 h by comparison with regular insulin working only 6-8 h. This effect may be explained by the monomeric configuration of aspart-insulin, which is probably better taken up by the intestinal mucosa than regular insulin.

Diabetes mellitus: new challenges and innovative therapies

Diabetes mellitus is a widespread disease prevalence and incidence of which increases worldwide. The introduction of insulin therapy represented a major breakthrough in type 1 diabetes; however, frequent hyper- and hypoglycemia seriously affects the quality of life of these patients. New therapeutic approaches, such as whole pancreas transplant or pancreatic islet transplant, stem cell, gene therapy and islets encapsulation are discussed in this review. Regarding type 2 diabetes, therapy has been based on drugs that stimulate insulin secretion (sulphonylureas and rapid-acting secretagogues), reduce hepatic glucose production (biguanides), delay digestion and absorption of intestinal carbohydrate (alpha-glucosidase inhibitors) or improve insulin action (thiazolidinediones). This review is also focused on the newer therapeutically approaches such as incretin-based therapies, bariatric surgery, stem cells and other emerging therapies that promise to further extend the options available. Gene-based therapies are among the most promising emerging alternatives to conventional treatments. Some of these therapies rely on genetic modification of non-differentiated cells to express pancreatic endocrine developmental factors, promoting differentiation of non-endocrine cells into β-cells, enabling synthesis and secretion of insulin in a glucose-regulated manner. Alternative therapies based on gene silencing using vector systems to deliver interference RNA to cells (i.e. against VEGF in diabetic retinopathy) are also a promising therapeutic option for the treatment of several diabetic complications. In conclusion, treatment of diabetes faces now a new era that is characterized by a variety of innovative therapeutic approaches that will improve quality-life and allow personalized therapy-planning in the near future.

Safety and efficacy of sodium caprate in promoting oral drug absorption: from in vitro to the clinic

A major challenge in oral drug delivery is the development of novel dosage forms to promote absorption of poorly permeable drugs across the intestinal epithelium. To date, no absorption promoter has been approved in a formulation specifically designed for oral delivery of Class III molecules. Promoters that are designated safe for human consumption have been licensed for use in a recently approved buccal insulin spray delivery system and also for many years as part of an ampicillin rectal suppository. Unlike buccal and rectal delivery, oral formulations containing absorption promoters have the additional technical hurdle whereby the promoter and payload must be co-released in high concentrations at the small intestinal epithelium in order to generate significant but rapidly reversible increases in permeability. An advanced promoter in the clinic is the medium chain fatty acid (MCFA), sodium caprate (C(10)), a compound already approved as a food additive. We discuss how it has evolved to a matrix tablet format suitable for administration to humans under the headings of mechanism of action at the cellular and tissue level as well as in vitro and in vivo efficacy and safety studies. In specific clinical examples, we review how C(10)-based formulations are being tested for oral delivery of bisphosphonates using Gastro Intestinal Permeation Enhancement Technology, GIPET (Merrion Pharmaceuticals, Ireland) and in a related solid dose format for antisense oligonucleotides (ISIS Pharmaceuticals, USA).

Serum insulin aspart concentrations following high-dose insulin aspart administered directly into the duodenum of healthy subjects: an open-labeled, single-blinded, and uncontrolled exploratory trial

OBJECTIVE

The goal of this study was to determine the bioavailability of high-dose insulin aspart administered directly into the duodenum of healthy subjects.

METHODS

In a pilot study, four subjects each received four escalating doses of a 1-ml solution of insulin aspart (100, 300, 600, and 1000 IU, respectively) directly into the duodenum. In the following main study, eight subjects each received two identical doses of insulin aspart of 1000 IU, in 4- and 8-ml solutions, respectively, directly into the duodenum. Subjects in the main study also received an intravenous and a subcutaneous injection of 4 to 6 IU of insulin aspart.

RESULTS

A considerable number of samples and, in some cases, consecutive samples revealed significantly increased concentrations of serum insulin aspart. Despite the significant serum insulin aspart concentrations, no significant changes of plasma glucose were measured. Moreover, no significant suppression of endogenous insulin secretion was detected, as assessed by the levels of serum human insulin.

CONCLUSIONS

Administration of high-dose insulin aspart directly into the duodenum of healthy subjects resulted in significantly increased serum insulin aspart concentrations in a high number of consecutive samples using a specific enzyme-linked immunosorbent assay. However, no significant changes in the levels of plasma glucose or serum human insulin were observed. Thus, the study did not provide any evidence of biological activity of the original insulin aspart molecule after high-dose administration directly into the duodenum.

Past, present, and future technologies for oral delivery of therapeutic proteins

Biological drugs are usually complex proteins and cannot be orally delivered due to problems related to degradation in the acidic and protease-rich environment of the gastrointestinal (GI) tract. The high molecular weight of these drugs often results in poor absorption into the periphery when administered orally. The most common route of administration for these therapeutic proteins is injection. Most of these proteins have short serum half-lives and need to be administered frequently or in high doses to be effective. So, difficulties in the administration of protein-based drugs provides the motivation for developing drug delivery systems (DDSs) capable of maintaining therapeutic drug levels without side effects as well as traversing the deleterious mucosal environment. Employing a polymer as an entrapment matrix is a common feature among the different types of systems currently being pursued for protein delivery. Protein release from these matrices can occur through various mechanisms, such as diffusion through or erosion of the polymer matrix, and sometimes a combination of both. Encapsulation of proteins in liposomes has also been a widely investigated technology for protein delivery. All of these systems have merit and our worthy of pursuit.

The movement of proteins across the insect and tick digestive system

The movement of intact proteins across the digestive system was shown in a number of different blood-feeding and non-blood-feeding insects in the orders Blattaria, Coleoptera, Diptera, Hemiptera, Lepidoptera, Orthoptera, Neuroptera and Siphonaptera, as well as in two tick families Ixodidae and Argasidae. Protein movement was observed for both normal dietary and xenobiotic proteins, which suggest that the mechanism for transfer is not substrate specific. The number of studies on the mechanism of movement is limited. The research so far suggests that movement can occur by either a transcellular or an intercellular pathway in the ventriculus with most of the research describing the former. Transfer is by continuous diffusion with no evidence of pinocytosis or vesicular transport common in mammalian systems. Proteins can move across the digestive system without modification of their primary or multimeric structure and with retention of their functional characteristics. Accumulation in the hemolymph is the result of the protein degradation rate in the gut and hemolymph and transfer rate across the digestive system and can be highly variable depending on species. Research on the development of delivery systems to enhance protein movement across the insect digestive system is in its infancy. The approaches so far considered with some success include the use of lipophilic-polyethylene glycol (PEG) polymers, the development of fusion proteins with lectins, reduced gut protease activity and the development of amphiphilic peptidic analogs. Additional research on understanding the basic mechanisms of protein delivery across the insect digestive system, the importance of structure activity in this transfer and the development of technology to improve movement across the gut could be highly significant to the future of protein and nucleic acid-based insecticide development as well as traditional chemical insecticidal technologies.

Comparison of oral insulin spray and subcutaneous regular insulin at mealtime in type 1 diabetes

BACKGROUND

The aim of this study was to compare the glucose pharmacodynamics after oral spray insulin (Oral-lyn , Generex Biotechnology, Toronto, ON, Canada) and subcutaneous (sc) injection of regular insulin in 10 subjects with type 1 diabetes mellitus (T1DM).

METHODS

Basal therapy was twice-daily insulin glargine. Preprandial (30 min) regular insulin was given for 3 days, followed by 9 days of Oral-lyn, eight to 12 puffs immediately pre- and postprandially. Adjustments for glycemia were made using standard snacks and additional regular insulin or Oral-lyn. Peripheral glucose measurements were self-monitored in duplicate. Serum concentrations of fructosamine and hemoglobin A1c (HbA1c) were determined at the start and the end of the study period.

RESULTS

Average glucose concentrations (in mmol/L) for the 3-day regular insulin and 9-day Oral-lyn periods, respectively, were: pre-breakfast (B), 5.06 and 3.89; 1-h post-B, 8.39 and 7.67; post-B, 6.00 and 6.33; pre-lunch (L), 5.50 and 4.72; 1-h post-L, 7.83 and 7.89; 2-h post-L, 5.89 and 6.33; pre-dinner (D), 5.61 and 5.17; 1-h post-D, 7.22 and 7.83; and 2-h post-D, 6.11 and 6.67. Areas under the curve for both treatments were not significantly different (P = 0.6875). Fructosamine (mean +/- SD, 338.7 +/- 77.4 micromol/L and 321.7 +/- 63.4 micromol/L), and HbA1c (mean +/- SD, 7.5 +/- 1.5% and 7.2 +/- 1.2%) did not change significantly.

CONCLUSIONS

Regular insulin and Oral-lyn had similar glucodynamic effects in subjects with T1DM receiving twice-daily insulin analogue as baseline therapy. Intensive monitoring and timely corrections with additional snacks, additional sc regular insulin, or Oral-lyn puffs resulted in appropriate glycemic control as assessed by individual daily glycemic responses and, especially, normal preprandial glycemia. Protein glycation decreased, but not significantly.

Oral absorption and in vivo biodistribution of alpha-conotoxin MII and a lipidic analogue

Conotoxins are highly constrained peptide toxins that exhibit pharmaceutically relevant biological activities. We herein report the extent of absorption and profile of distribution of a native alpha-conotoxin, MII and a lipophilic analogue of MII (N-LaaMII) after intravenous (iv) and oral administration to male Sprague-Dawley rats. N-LaaMII is formed by coupling 2-amino-D,L-dodecanoic acid (Laa) to the N-terminus of MII and has previously been shown to exhibit significantly improved permeability across Caco-2 cell monolayers compared to the native MII while maintaining the potency in inhibition of nAChRs of the parent peptide. Both peptides crossed the GI tract after oral administration (approximately 6% after 30 m). While Laa conjugation did not significantly improve absorption, it did greatly increase the accumulation of the compound in the liver after iv administration. Neither peptide crossed the blood-brain barrier to any significant extent. This is the first study of the in vivo biodistribution of an alpha-conotoxin after oral administration.

Oral delivery of insulin associated to polymeric nanoparticles in diabetic rats

Nanoparticles prepared with a blend of a biodegradable polyester (poly(-epsilon-caprolactone)) and a polycationic non-biodegradable acrylic polymer (Eudragit RS) have been used as a drug carrier for oral administration of insulin. The rate of encapsulation of insulin was around 96%. The therapeutic efficiency of oral insulin nanoparticles (25, 50 and 100 IU/kg) in diabetic rats and the intestinal uptake of fluorescein isothiocyanate (FITC) labelled insulin were studied. When administered orally by force-feeding to diabetic rats, insulin nanoparticles decreased fasted glycemia in a dose dependant manner with a maximal effect observed with 100 IU/kg. These insulin nanoparticles also increased serum insulin levels and improved the glycemic response to an oral glucose challenge for a prolonged period of time. FITC-Insulin-loaded nanoparticles strongly adhered to the intestinal mucosa and labeled insulin, either released and/or still inside nanoparticles, was mainly taken up by the Peyer's patches. It is concluded that polymeric nanoparticles allows the preservation of insulin's biological activity. In addition, the antidiabetic effect can be explained by the mucoadhesive properties of the polycationic polymer (Eudragit) RS) allowing the intestinal uptake of insulin.

Alternatives routes of insulin delivery

Optimal glycaemic control is necessary to prevent diabetes-related complications. An intensive treatment, which could mimic physiological insulin secretion, would be the best one. However subcutaneous insulin treatment is not physiologic and represents a heavy burden for patients with type 1 and type 2 diabetes mellitus. Consequently, more acceptable, at least as effective, alternative routes of insulin delivery have been developed over the past years. Up to now, only pulmonary administration of insulin (inhaled insulin) has become a feasible alternative to cover mealtime insulin requirements and one of the various administration systems was recently approved for clinical use in Europe and the United States. But, due to advances in technology, other routes, such as transdermal or oral (buccal and intestinal) insulin administration, could become feasible in a near future, and they could be combined together to offer non-invasive, efficacious and more physiological way of insulin administration to patients with diabetes.

Non-invasive routes for insulin administration: current state and perspectives

Diabetes mellitus is a chronic disease that usually requires multiple insulin injections to achieve adequate glycaemic control. This represents a major cause of reduced compliance to treatment. Consequently, other routes for insulin administration have been explored. During recent years, much progress in the development of inhaled insulin has been made. Inhaled insulin has shown favourable properties, such as a rapid onset of action, improved bioavailability and good tolerability; thereby providing satisfaction and ease of administration. However, long-term safety of inhaled insulin needs to be assessed, and the cost would be higher than injectable insulin. Nasal, oral and transdermal insulins are undergoing early phases of pharmacological development. The purpose of this review is to describe the latest developments in the area of non-invasive routes for insulin delivery.

Commercial challenges of protein drug delivery

The discovery of insulin in 1922 marked the beginning of research and development to improve the means of delivering protein therapeutics to patients. From that period forward, investigators have contemplated every possible route of delivery. Their research efforts have followed two basic pathways: one path has focused on non-invasive means of delivering proteins to the body; and the second path has been primarily aimed at increasing the biological half-life of the therapeutic molecules. Thus far, the commercial successes of protein delivery by the nasal, oral and pulmonary routes have been more opportunistic rather than the application of platform technologies applicable to every protein or peptide. In several limited cases, sustained delivery of peptides and proteins has employed the use of polymeric carriers. More successes have been achieved by chemical modification using amino acid substitutions, protein pegylation or glycosylation to improve the pharmacodynamic properties of certain macromolecules. Today, commercial successes for protein and peptide delivery systems remain limited. The needle and syringe remain the primary means of protein delivery. Major hurdles remain in order to overcome the combined natural barriers of drug permeability, drug stability, pharmacokinetics and pharmacodynamics of protein therapeutics.

Nasal clearance in health and disease

This paper reviews the anatomical and physiological factors of importance for nasal drug delivery and discusses in particular the influence of the nasal mucociliary clearance mechanism on the nasal absorption of drugs. The effect of nasal pathological conditions on the mucociliary clearance mechanism and the possible effect of such disease states on nasal drug transport are also discussed. Strategies for the exploitation of bioadhesive drug delivery systems and especially nasal absorption enhancers for the improvement of nasal drug delivery are evaluated to include considerations of the mechanism of action and correlation between the degree of bioadhesion and absorption enhancement and transport of drugs across the nasal membrane. A range of studies involving bioadhesive/absorption enhancer systems are detailed. A selected bioadhesive material, chitosan, which has been shown to have excellent absorption enhancer properties for a variety of drugs is discussed in some detail.

Nanoscale analysis of protein and peptide absorption: insulin absorption using complexation and pH-sensitive hydrogels as delivery vehicles

Recent advances in the discovery and delivery of drugs to cure chronic diseases are achieved by combination of intelligent material design with advances in nanotechnology. Since many drugs act as protagonists or antagonists to different chemicals in the body, a delivery system that can respond to the concentrations of certain molecules in the body is invaluable. For this purpose, intelligent therapeutics or "smart drug delivery" calls for the design of the newest generation of sensitive materials based on molecular recognition. Biomimetic polymeric networks can be prepared by designing interactions between the building blocks of biocompatible networks and the desired specific ligands and by stabilizing these interactions by a three-dimensional structure. These structures are at the same time flexible enough to allow for diffusion of solvent and ligand into and out of the networks. Synthetic networks that can be designed to recognize and bind biologically significant molecules are of great importance and influence a number of emerging technologies. These synthetic materials can be used as unique systems or incorporated into existing drug delivery technologies that can aid in the removal or delivery of biomolecules and restore the natural profiles of compounds in the body.

Chitosan–PEG nanocapsules as new carriers for oral peptide delivery

We have previously reported the ability of chitosan nanocapsules to enhance and prolong the oral absorption of peptides. In the present work, our goal was to design a new type of nanocapsules, using chitosan chemically modified with poly(ethylene glycol) (PEG) (0.5% and 1% pegylation degree) and to investigate the consequences of this modification on the in vitro and in vivo behaviour of the nanocapsules. Chitosan-PEG nanocapsules and the control PEG-coated nanoemulsions were obtained by the solvent displacement technique. Their size was in the range of 160-250 nm. Their zeta potential was greatly affected by the nature of the coating, being positive for chitosan-PEG nanocapsules and negative in the case of PEG-coated nanoemulsions. The presence of PEG, whether alone or grafted to chitosan, improved the stability of the nanocapsules in the gastrointestinal fluids. Using the Caco-2 model cell line it was observed that the pegylation of chitosan reduced the cytotoxicity of the nanocapsules. In addition, these nanocapsules did not cause a significant change in the transepithelial resistance of the monolayer. Finally, the results of the in vivo studies showed the capacity of chitosan-PEG nanocapsules to enhance and prolong the intestinal absorption of salmon calcitonin. Additionally, they indicated that the pegylation degree affected the in vivo performance of the nanocapsules. Therefore, by modulating the pegylation degree of chitosan, it was possible to obtain nanocapsules with a good stability, a low cytotoxicity and with absorption enhancing properties.

Amphiphilic Conjugates of Human Brain Natriuretic Peptide Designed for Oral Delivery: In Vitro Activity Screening

Congestive heart failure (CHF) is a complex syndrome involving altered neurohormonal levels and impaired cardiac and renal function. In recent years, intravenous administration of exogenous human brain-type natriuretic peptide (hBNP) has become an important therapy in treating patients with acutely decompensated CHF. However, reports during the past year suggest that hBNP could play a prominent role in the chronic treatment of CHF patients as well. We are currently developing conjugates of hBNP suitable for oral delivery to provide a patient-friendly treatment option for chronic heart failure patients. In this report, we present in vitro activity results obtained from hBNP conjugates featuring a variety of rationally designed amphiphilic oligomers. Mapping studies revealed that the hydrophobic/hydrophilic balance of the oligomer impacted the regioselectivity of conjugation. Additionally, the regiochemistry and extent of conjugation had a significant impact on activity. Many monoconjugates retained activity comparable to native peptide and are currently under evaluation in subsequent in vivo screens.

The potential of chitosan for the oral administration of peptides

Over recent years, a major challenge in drug delivery has been the design of appropriate vehicles for the oral administration of macromolecular drugs (peptides and proteins). Indeed, despite the increasing market value of these complex molecules, their clinical use has been highly limited by their reduced oral bioavailability. Among the different delivery approaches explored so far, those based on the use of the polysaccharide chitosan have opened promising alternatives towards this ambitious goal. This is due to the interesting physicochemical and biopharmaceutical properties of this polymer. This article describes the advances that have been made in the design of chitosan-based systems specially adapted for the oral administration of peptides. These systems include solutions, microspheres, nanoparticles, nanocapsules and liposomes. More specifically, this article discusses the efficacy of the different delivery approaches for improving the absorption of peptides, and analyses the various mechanisms that have been proposed for the understanding of their efficacy.

Blood glucose-lowering activity of a hyaluronan-insulin complex after oral administration to rats with diabetes

BACKGROUND

Several covalently modified insulin derivatives or formulations with absorption enhancers have been shown to decrease the blood glucose concentration after oral administration in animals with diabetes. The aim of this study was to investigate the biological activity of a novel hyaluronan-insulin complex.

METHODS

The efficacy of the complexed insulin after oral and subcutaneous administration was evaluated by analysis of blood glucose concentrations in rats with streptozotocin-induced diabetes.

RESULTS

The complexed insulin significantly decreased blood glucose concentrations within 1 h after oral administration in eight of 10 rats in the dose interval 1.5-4.7 mg (3.1-14.5 mg/kg). Oral administration of native insulin or non-complexed insulin plus hyaluronan using similar doses failed to decrease blood glucose concentrations. The lowest oral dose of complexed insulin achieving a statistically significant decrease in blood glucose concentrations was 1.2-1.5 mg (about 4 mg/kg), and the threshold dose after subcutaneous administration was 0.08-0.12 mg (0.25 mg/kg).

CONCLUSIONS

The hyaluronan-insulin complex was active after oral administration and decreased blood glucose concentrations in rats with streptozotocin-induced diabetes. The ratio between the oral and subcutaneous threshold doses was about 16.

Synthesis and biological properties of insulin-deoxycholic acid chemical conjugates

Bile acids have been considered very useful in the preparation of new pharmaceuticals, and more recently in the preparation of peptide and protein drugs because of their natural chemical and biological properties. In this study, we modified recombinant human insulin by covalently attaching deoxycholic acid (DOCA) derivatives in order to synthesize orally active insulin analogues. DOCA derivatives, namely succinimido deoxycholate and succinimido bisdeoxycholyl-L-lysine were prepared and site specifically conjugated at Lys(B29) of insulin. The resultant insulin conjugates, [N(B29)-deoxycholyl] insulin (Ins-DOCA) and [N(B29)-bisdeoxycholyl-L-lysil] insulin (Ins-bisDOCA), were studied for their chemical, structural, and biological properties. Their chemical properties were determined by HPLC, MALDI-TOF mass spectroscopy, and dynamic light scattering. Lipophilicity and self-aggregation behavior of insulin conjugates were enhanced with increasing number of labeled bile acid. The far-ultraviolet region of circular dichroism spectra showed no significant change of the tertiary structure of insulin in aqueous solution due to conjugation. Competitive insulin binding assay with HepG2 cells revealed that monosubstituted insulin conjugates still retained high binding affinity to the insulin receptor. When the insulin conjugates were intravenously administered (0.33 IU/kg) to streptozotocin (STZ)-induced diabetic rats, the conjugates showed sustained biological activity for a longer period with the similar lowest blood glucose level (glucose nadir), compared to native insulin. In further studies, the resulting new insulin conjugates will be investigated for their oral efficiency as a long-acting insulin formulation for the treatment of diabetic patients.

Simulated first-phase insulin release using Humulin or insulin analog HIM2 is associated with prolonged improvement in postprandial glycemia

We examined the extent to which priming the liver with a pulse of Humulin or the insulin analog hexyl-insulin monoconjugate 2 (HIM2) reduces postprandial hyperglycemia. Somatostatin (0.5 microg.kg(-1).min(-1)) was given with basal intraportal insulin and glucagon for 4.5 h into three groups of 42-h-fasted conscious dogs. From 0-5 min, group 1 (BI, n = 6) received saline, group 2 (HI, n = 6) received a Humulin pulse (10 mU.kg(-1).min(-1)), and group 3 (HIM2, n = 6) received a HIM2 pulse (10 mU.kg(-1).min(-1)). Duodenal glucose was infused (5.0 mg.kg(-1).min(-1)) from 15 to 270 min. Arterial insulin in BI remained basal (6 +/- 1 microU/ml) and peaked at 52 +/- 15 (HI) and 164 +/- 44 microU/ml (HIM2) and returned to baseline by 30 and 60 min, respectively. Arterial plasma glucose plateaued at 265 +/- 20, 214 +/- 15, and 193 +/- 14 mg/dl in BI, HI, and HIM2. Glucose absorption was similar in all groups. Significant net hepatic glucose uptake occurred at 85, 55, and 25 min in BI, HI, and HIM2, respectively. Nonhepatic glucose clearance at 270 min differed among groups (BI, HI, HIM2): 0.62 +/- 0.11, 0.76 +/- 0.26, and 1.61 +/- 0.29 ml.kg(-1).min(-1) (P < 0.05). A brief (5-min) insulin pulse improved postprandial glycemia, stimulating hepatic glucose uptake and prolonging enhancement of nonhepatic glucose clearance. HIM2 was more effective than Humulin, perhaps because its lowered clearance caused higher levels at the liver and periphery and its biological activity was not reduced proportionally to its decreased clearance.

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.

Current strategies used to enhance the paracellular transport of therapeutic polypeptides across the intestinal epithelium

The intent of this paper is to update the reader on various strategies which have been utilized to increase the paracellular permeability of protein and polypeptide drugs across the intestinal epithelium. Structural features of protein and polypeptide drugs, together with the natural anatomical and physiological features of the gastrointestinal (GI) tract, have made oral delivery of this class of compounds extremely challenging. Interest in the paracellular route for the transport of therapeutic proteins and polypeptides following oral administration has recently intensified and continues to be explored. The assumption that molecules with a large molecular weight are not able to diffuse through the tight junctions of the intestinal membrane has been challenged by current research, along with an increased understanding of tight junction physiology.

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.

Transmucosal macromolecular drug delivery

Mucosal surfaces are the most common and convenient routes for delivering drugs to the body. However, macromolecular drugs such as peptides and proteins are unable to overcome the mucosal barriers and/or are degraded before reaching the blood stream. Among the approaches explored so far in order to optimize the transport of these macromolecules across mucosal barriers, the use of nanoparticulate carriers represents a challenging but promising strategy. The present paper aims to compare the characteristics and potential of nanostructures based on the mucoadhesive polysaccharide chitosan (CS). These are CS nanoparticles, CS-coated oil nanodroplets (nanocapsules) and CS-coated lipid nanoparticles. The characteristics and behavior of CS nanoparticles and CS-coated lipid nanoparticles already reported [A. Vila, A. Sanchez, M. Tobio, P. Calvo, M.J. Alonso, Design of biodegradable particles for protein delivery, J. Control. Rel. 78 (2002) 15-24; R. Fernandez-Urrusuno, P. Calvo, C. Remunan-Lopez, J.L. Vila-Jato, M.J. Alonso, Enhancement of nasal absorption of insulin using chitosan nanoparticles, Pharm. Res. 16 (1999) 1576-1581; M. Garcia-Fuentes, D. Torres, M.J. Alonso, New surface-modified lipid nanoparticles as delivery vehicles for salmon calcitonin (submitted for publication).] are compared with those of CS nanocapsules originally reported here. The three types of systems have a size in the nanometer range and a positive zeta potential that was attributed to the presence of CS on their surface. They showed an important capacity for the association of peptides such as insulin, salmon calcitonin and proteins, such as tetanus toxoid. Their mechanism of interaction with epithelia was investigated using the Caco-2 model cell line. The results showed that CS-coated systems caused a concentration-dependent reduction in the transepithelial resistance of the cell monolayer. Moreover, within the range of concentrations investigated, these systems were internalized in the monolayer in a concentration-dependent manner. This uptake was slightly enhanced by the presence of the CS coating but, as compared with previously published results [M. Garcia-Fuentes, C. Prego, D. Torres, M.J. Alonso, Triglyceride-chitosan nanostructures for oral calcitonin delivery: evaluation in the Caco-2 cell model and in vivo (submitted for publication)], highly dependent on the nature of the lipid core. Nevertheless, these differences in the uptake of the CS-coated systems (solid lipid core or oily core) by the Caco-2 cells did not have a consequence in the in vivo behaviour. Indeed, both CS-coated systems (nanocapsules and CS-coated nanoparticles) showed an important capacity to enhance the intestinal absorption of the model peptide, salmon calcitonin, as shown by the important and long-lasting decrease in the calcemia levels observed in rats.

Therapeutic insulins and their large-scale manufacture

Biotechnological innovations over the past 25 years have underpinned the rapid development of a thriving biopharmaceutical sector. Therapeutic insulin remains one of the most commonly used products of pharmaceutical biotechnology and insulin-based products command annual global sales in excess of $4.5 billion. Innovations in its method of production and in particular the advent of engineered insulin analogues provide a fascinating insight into how scientific and technological advances have impacted upon the pharmaceutical biotechnology sector as a whole. Current insulin-based diabetes research is increasingly focused not on the insulin molecule per se, but upon areas such as the development of non-parenteral insulin delivery systems, as well as organ-/cell-based and gene therapy-based approaches to controlling the disease.