Molecular engineering of safe and efficacious oral basal insulin

Pharmacological and Benefit-Risk Profile of Once-Weekly Basal Insulin Administration (Icodec): Addressing Patients' Unmet Needs and Exploring Future Applications

Diabetes mellitus (DM) is a chronic metabolic disease affecting over 500 million people worldwide, which leads to severe complications and to millions of deaths yearly. When therapeutic goals are not reached with diet, physical activity, or non-insulin drugs, starting/adding insulin treatment is recommended by international guidelines. A novel recombinant insulin is icodec, a once-weekly insulin that successfully completed phase III trials and that has recently obtained the marketing authorization approval from the European Medicines Agency. This narrative review aims to assess icodec pharmacological and clinical features concerning evidence on benefit-risk profile, as compared to other basal insulins, addressing the potential impact on patients' unmet needs. Icodec is a full agonist, recombinant human insulin analogue characterized by an ultra-long half-life (196 h), enabling its use in once-weekly administration. Phase III randomized clinical trials involving more than 4000 diabetic patients, mostly type 2 DM, documented non-inferiority of icodec, as compared to currently available basal insulins, in terms of estimated mean reduction of glycated hemoglobin levels; a superiority of icodec, compared to control, was confirmed in insulin-naïve patients (ONWARDS 1, 3, and 5), and in patients previously treated with basal insulin (ONWARDS 2). Icodec safety profile was comparable to the currently available basal insulins. Once-weekly icodec has the potential to improve patients' adherence, thus positively influencing patients' treatment satisfaction as well as quality of life, especially in type 2 DM insulin-naïve patients. An improved adherence might positively influence glycemic target achievement, reduce overall healthcare costs and overcome some of the unmet patients' needs. Icodec has the potential to emerge as a landmark achievement in the evolution of insulin therapy, with a positive impact also for the National Health Services and the whole society.

Development and evaluation of C10 and SNAC erodible tablets for gastric delivery of a GIP/GLP1 peptide in monkeys

The permeation enhancers (PEs) sodium caprate (C10) and sodium N-[8-(2-hydroxybenzoyl) amino] caprylate (SNAC) have been utilized for the intestinal and gastric delivery of macromolecules, respectively. However, the potential of C10 for the gastric delivery of a peptide and the ability of SNAC to deliver other peptides to the stomach beyond semaglutide have not been investigated. In this study, we have developed and evaluated C10 and SNAC-containing erodible tablets for the gastricdelivery of a glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GIP/GLP1) dual agonist peptide (LY) in cynomolgus monkeys. We also evaluated the impact of release rates on the in vivo performance of C10 and SNAC. Furthermore, we compared the oral exposure of the LY peptide and semaglutide with different proteolytic stabilities using a SNAC erodible tablet. Additionally, we investigated the mechanism of action of SNAC for improving gastric absorption of the LY peptide via tissue distribution in monkey. C10 and SNAC tablets released the peptide and PE by erosion from the tablet surface with 100 % release within 60 min at pH 6.8. Following a single oral administration to monkeys, C10 and SNAC erodible tablets at 300 mg exhibited similar LY mean absolute oral bioavailability of 5.7 % and 4.2 %, respectively. The C10 immediate release capsule (500 mg) with faster dissolution profile (10 min) showed a decrease in the LY oral bioavailability; however, a faster dissolution profile (15 min) with erodible SNAC tablet resulted in a relatively higher LY oral bioavailability compared to the slow-release erodible tablets (60 min). Using SNAC as the PE, the combination of slow-release tablet design and LY peptide with higher pepsin stability resulted in about 4-fold higher mean oral bioavailability in the monkeys than semaglutide (4.2 % vs 1.2 %, respectively). In the monkey gastric tissue, SNAC was found to reduce tight junction protein levels and increase the peptide uptake into the gastric epithelium suggesting its permeation enhancing mechanism via both paracellular and transcellular pathways. Taking these data altogether, the enhanced proteolytic stability of the LY peptide combined with the optimal erodible tablets enabled the gastric delivery of the LY peptide with a higher oral bioavailability than semaglutide.

The Current and Promising Oral Delivery Methods for Protein- and Peptide-Based Drugs

Drugs based on peptides and proteins (PPs) have been widely used in medicine, beginning with insulin therapy in patients with diabetes mellitus over a century ago. Although the oral route of drug administration is the preferred one by the vast majority of patients and improves compliance, medications of this kind due to their specific chemical structure are typically delivered parenterally, which ensures optimal bioavailability. In order to overcome issues connected with oral absorption of PPs such as their instability depending on digestive enzymes and pH changes in the gastrointestinal (GI) system on the one hand, but also their limited permeability across physiological barriers (mucus and epithelium) on the other hand, scientists have been strenuously searching for novel delivery methods enabling peptide and protein drugs (PPDs) to be administered enterally. These include utilization of different nanoparticles, transport channels, substances enhancing permeation, chemical modifications, hydrogels, microneedles, microemulsion, proteolytic enzyme inhibitors, and cell-penetrating peptides, all of which are extensively discussed in this review. Furthermore, this article highlights oral PP therapeutics both previously used in therapy and currently available on the medical market.

Oral Drug Delivery Systems Applied to Launched Products: Value for the Patients and Industrial Considerations

Drug delivery systems (DDS) control the amount, rate, and site of administration of drug substances in the body as well as their release and ADME (absorption, distribution, metabolism, excretion). Among the various types of DDS, amount-controlled DDS for solubilization and absorption increase the bioavailability. Time- and amount-controlled DDS are controlled release formulations classified as (1) membrane-type, (2) matrix-type, (3) osmotic-type, and (4) ion-exchange type. Timed-release formulations also control the time and amount of release and the absorption of drugs. Site- and amount-controlled DDS are characterized by colonic delivery and intestinal lymph-targeting to improve release and ADME of drug substances. Finally, site-, time-, and amount-controlled DDS are gastroretentive formulations and local delivery in the oral cavity to improve site retention, release, and ADME of drugs. DDS can enhance efficacy, reduce adverse effects, and optimize the dosing frequency of various drug products to increase patient value. This review focuses on patient value and industrial considerations of launched oral DDS. We provide a technological overview of candidate and marketed DDS, as well as the pros/cons of the technologies for industrialization with consideration to excipients, manufacturing, and storage stability. Moreover, to demonstrate the usefulness of the technology and support the selection and development of the best technologies for patients, we also describe patient value from clinical studies and analyses, particularly with regard to increased new medical options, higher efficacy, reduced adverse effects, reduced number of doses and clinic visits, easier administration, higher quality of life, greater adherence, and satisfaction.

Helical-Like Assembly of Nateglinide as Coating for Oral Delivery of Insulin and Their Synergistic Prevention of Diabetes Mellitus

Oral delivery of antidiabetic active components promises to free millions of people from daily suffering who require routine injections. However, oral insulin (Ins) and other short-acting compounds such as nateglinide (NG) in harsh gastrointestinal tract still face great challenging, including low bioavailability, and rapid elimination. In this study, inspired by the self-assembly of phenylalanine-based peptides in nature, it is showed that NG a small phenylalanine derivative, assembles into left-handed helical nanofibers in the presence of Ca2+ . These helical NG nanofibers functioned as a coating layer on the surface of Ca2+ -linked alginate (Alg) microgels for the effective encapsulation of Ins. As expected, the sustained release and prolonged circulation of Ins and NG from the Ins-loading Alg/NG microgels (Ins@Alg/NG) in the intestinal tract synergistically maintain a relatively normal blood glucose level in streptozotocin-induced diabetic mice after oral administration of Ins@Alg/NG. This further confirms that Ins@Alg/NG ameliorated Ins resistance mainly through activating Insreceptor substrate 1 (IRS1), protein kinase B (AKT), and AMP-activated protein kinase (AMPK), as well as by repressing glycogen synthase kinase-3β (GSK-3β). The strategy of using the assembly of NG as a coating achieves the oral delivery of insulin and showcases a potential for the treatment of diabetes.

Material design for oral insulin delivery

Frequent insulin injections remain the primary method for controlling the blood glucose level of individuals with diabetes mellitus but are associated with low compliance. Accordingly, oral administration has been identified as a highly desirable alternative due to its non-invasive nature. However, the harsh gastrointestinal environment and physical intestinal barriers pose significant challenges to achieving optimal pharmacological bioavailability of insulin. As a result, researchers have developed a range of materials to improve the efficiency of oral insulin delivery over the past few decades. In this review, we summarize the latest advances in material design that aim to enhance insulin protection, permeability, and glucose-responsive release. We also explore the opportunities and challenges of using these materials for oral insulin delivery.

Total Chemical Synthesis of Palmitoyl-Conjugated Insulin

Commercially available insulins are manufactured by recombinant methods for the treatment of diabetes. Long-acting insulin drugs (e.g., detemir and degludec) are obtained by fatty acid conjugation at LysB29 ε-amine of insulin via acid-amide coupling. There are three amine groups in insulin, and they all react with fatty acids in alkaline conditions. Due to the lack of selectivity, such conjugation reactions produce non-desired byproducts. We designed and chemically synthesized a novel thiol-insulin scaffold (CysB²⁹-insulin II), by replacing the Lys^B29 residue in insulin with the Cys^B29 residue. Then, we conjugated a fatty acid moiety (palmitic acid, C16) to CysB²⁹-insulin II by a highly efficient and selective thiol-maleimide conjugation reaction. We obtained the target peptide (palmitoyl-insulin) rapidly within 5 min without significant byproducts. The palmitoyl-insulin is shown to be structurally similar to insulin and biologically active both in vitro and in vivo. Importantly, unlike native insulin, palmitoyl-insulin is slow and long-acting.

Oral Delivery of Therapeutic Antibodies with a Transmucosal Polymeric Carrier

Therapeutic proteins are playing increasingly important roles in treating numerous types of diseases. However, oral administration of proteins, especially large ones (e.g., antibodies), remains a great challenge due to their difficulties in penetrating intestinal barriers. Herein, fluorocarbon-modified chitosan (FCS) is developed for efficient oral delivery of different therapeutic proteins, in particular large ones such as immune checkpoint blockade antibodies. In our design, therapeutic proteins are mixed with FCS to form nanoparticles, lyophilized with appropriate excipients, and then filled into enteric capsules for oral administration. It has been found that FCS could promote transmucosal delivery of its cargo protein via inducing transitory rearrangement of tight junction associated proteins between intestinal epithelial cells and subsequently release free proteins into blood circulation. It is shown that at a 5-fold dose oral delivery of anti-programmed cell death protein-1 (αPD1) or its combination with anti-cytotoxic T-lymphocyte antigen 4 (αCTLA4) using this method could achieve comparable antitumor therapeutic responses to that achieved by intravenous injection of corresponding free antibodies in various types of tumor models and, more excitingly, result in significantly reduced immune-related adverse events. Our work successfully demonstrates the enhanced oral delivery of antibody drugs to achieve systemic therapeutic responses and may revolutionize the future clinical usage of protein therapeutics.

Factors Affecting Performance of Insulin Pen Injector Technology: A Narrative Review

BACKGROUND

Insulin treatment is an essential hormone replacement therapy for the survival of people with type 1 diabetes and is often used for treatment in type 2 diabetes, particularly as the disease progresses. Advances in insulin therapy have been made since its discovery, including production of human insulin and development of insulin analogs with improved efficacy and safety profiles. The different types of available insulin formulations allow health care professionals to personalize treatment to an individual's needs. Generally, insulin requires parenteral administration via subcutaneous injection owing to very low oral bioavailability.

METHODS

This article reviews the human, technological, economical, and regulatory factors affecting the performance of insulin pens and the relationship between them. Opportunities and challenges that insulin pen injections may encounter in the future are also considered.

RESULTS

Insulin delivery devices, together with other factors, influence dose accuracy, convenience, and quality of life, contributing to easier medication administration with high efficacy and safety. For patients, ease of use, fast and accurate drug delivery, and painless injection are the most valuable features of an insulin injection device. For manufacturers, technological feasibility and economic viability also need to be considered when developing injection devices.

CONCLUSION

Insulin pen injectors are generally preferred over vial and syringe, although access may be limited in some health care systems. Insulin pen injectors can adapt to different insulin regimens and formulations and have the potential to acquire dosing data in real time.

Recent Advances in Oral and Transdermal Protein Delivery Systems

Protein and peptide drugs are predominantly administered by injection to achieve high bioavailability, but this greatly compromises patient compliance. Oral and transdermal drug delivery with minimal invasiveness and high adherence represent attractive alternatives to injection administration. However, oral and transdermal administration of bioactive proteins must overcome biological barriers, namely the gastrointestinal and skin barriers, respectively. The rapid development of new materials and technologies promises to address these physiological obstacles. This review provides an overview of the latest advances in oral and transdermal protein delivery, including chemical strategies, synthetic nanoparticles, medical microdevices, and biomimetic systems for oral administration, as well as chemical enhancers, physical approaches, and microneedles in transdermal delivery. We also discuss challenges and future perspectives of the field with a focus on innovation and translation.

In Vivo Mechanism of Action of Sodium Caprate for Improving the Intestinal Absorption of a GLP1/GIP Coagonist Peptide

Sodium caprate (C10) has been widely evaluated as an intestinal permeation enhancer for the oral delivery of macromolecules. However, the effect of C10 on the intestinal absorption of peptides with different physicochemical properties and its permeation-enhancing effect in vivo remains to be understood. Here, we evaluated the effects of C10 on intestinal absorption in rats with a glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GIP-GLP1) dual agonist peptide (LY) and semaglutide with different enzymatic stabilities and self-association behaviors as well as the oral exposure of the LY peptide in minipigs. Furthermore, we investigated the mechanism of action (MoA) of C10 for improving the intestinal absorption of the LY peptide in vivo via live imaging of the rat intestinal epithelium and tissue distribution of the LY peptide in minipigs. The LY peptide showed higher proteolytic stability in pancreatin and was a monomer in solution compared to that in semaglutide. C10 increased in vitro permeability in the minipig intestinal organoid monolayer to a greater extent for the LY peptide than for semaglutide. In the rat jejunal closed-loop model, C10 increased the absorption of LY peptide better than that of semaglutide, which might be attributed to higher in vitro proteolytic stability and permeability of the LY peptide. Using confocal live imaging, we observed that C10 enabled the rapid oral absorption of a model macromolecule (FD4) in the rat intestine. In the duodenum tissues of minipigs, C10 was found to qualitatively reduce the tight junction protein level and allow peptide uptake to the intestinal cells. C10 decreased the transition temperature of the artificial lipid membrane, indicating an increase in membrane fluidity, which is consistent with the above in vivo imaging results. These data indicated that the LY's favorable physicochemical properties combined with the effects of C10 on the intestinal mucosa resulted in an ∼2% relative bioavailability in minipigs.

Derivatization with fatty acids in peptide and protein drug discovery

Peptides and proteins are widely used to treat a range of medical conditions; however, they often have to be injected and their effects are short-lived. These shortcomings of the native structure can be addressed by molecular engineering, but this is a complex undertaking. A molecular engineering technology initially applied to insulin - and which has now been successfully applied to several biopharmaceuticals - entails the derivatization of peptides and proteins with fatty acids. Various protraction mechanisms are enabled by the specific characteristics and positions of the attached fatty acid. Furthermore, the technology can ensure a long half-life following oral administration of peptide drugs, can alter the distribution of peptides and may hold potential for tissue targeting. Due to the inherent safety and well-defined chemical nature of the fatty acids, this technology provides a versatile approach to peptide and protein drug discovery.

Preclinical pharmacology of RA15127343: In vitro and in vivo activity of a novel ultralong-acting basal insulin

AIM

To report the in vitro and in vivo preclinical pharmacokinetic (PK) and pharmacodynamic (PD) properties of RA15127343, a novel ultralong-acting insulin analogue targeting once-weekly administration, in female Göttingen minipigs.

METHODS

In vitro binding and activation of human insulin receptor isoforms (IR-A/IR-B), glucose uptake in rat myocytes, as well as mitogenic activity of RA15127343 were evaluated. In vivo, the PK and PD activities of RA15127343 were assessed in female, normoglycaemic Göttingen minipigs. The half-life (t_1/2 ) and time to maximum plasma concentration (T_max ) of subcutaneously (SC) administered RA15127343 (10/30/45/60 nmol/kg) were estimated. In vivo blood glucose and endogenous plasma C-peptide concentrations after single SC administration (10/30/45/60 nmol/kg) or repeated dosing (15 nmol/kg) were analysed.

RESULTS

In comparison to human insulin, RA15127343 showed lower in vitro binding affinity (19.9/6.31 μM vs. 1.10/1.14 nM) and activation (2.054 μM/669.6 nM vs. 26.04/18.24 nM) of IR-A/IR-B, lower potency to activate glucose uptake (855.2 vs. 3.37 nM) and lower mitogenic activity (17.92 μM vs. 10.78 nM; proliferation in MCF7 cells). In vivo, the mean t_1/2 and T_max of RA15127343 after SC administration ranged from 48 to 59 and 30 to 39 hours, respectively. Blood glucose and plasma C-peptide concentrations were significantly lower with RA15127343 (single/repeated doses) versus vehicle.

CONCLUSIONS

RA15127343 showed an ultra-long t_1/2 with a slow onset of action. The preclinical pharmacological outcomes suggest RA15127343 could be a potential ultralong-acting insulin analogue with low risk of hypoglycaemia in humans.

Characterization and impact of peptide physicochemical properties on oral and subcutaneous delivery

Peptides, an emerging modality within the biopharmaceutical industry, are often delivered subcutaneously with evolving prospects on oral delivery. Barrier biology within the subcutis or gastrointestinal tract is a significant challenge in limiting absorption or otherwise disrupting peptide disposition. Aspects of peptide pharmacokinetic performance and ADME can be mitigated with careful molecular design that tailors for properties such as effective size, hydrophobicity, net charge, proteolytic stability, and albumin binding. In this review, we endeavor to highlight effective techniques in qualifying physicochemical properties of peptides and discuss advancements of in vitro models of subcutaneous and oral delivery. Additionally, we will delineate empirical findings around the relationship of these physicochemical properties and in vivo (animal or human) impact. We conclude that robust peptide characterization methods and in vitro techniques with demonstrated correlations to in vivo data are key routines to incorporate in the drug discovery and development to improve the probability of technical and commercial success of peptide therapeutics.

On the Utility of Chemical Strategies to Improve Peptide Gut Stability

Inherent susceptibility of peptides to enzymatic degradation in the gastrointestinal tract is a key bottleneck in oral peptide drug development. Here, we present a systematic analysis of (i) the gut stability of disulfide-rich peptide scaffolds, orally administered peptide therapeutics, and well-known neuropeptides and (ii) medicinal chemistry strategies to improve peptide gut stability. Among a broad range of studied peptides, cyclotides were the only scaffold class to resist gastrointestinal degradation, even when grafted with non-native sequences. Backbone cyclization, a frequently applied strategy, failed to improve stability in intestinal fluid, but several site-specific alterations proved efficient. This work furthermore highlights the importance of standardized gut stability test conditions and suggests defined protocols to facilitate cross-study comparison. Together, our results provide a comparative overview and framework for the chemical engineering of gut-stable peptides, which should be valuable for the development of orally administered peptide therapeutics and molecular probes targeting receptors within the gastrointestinal tract.

An integrated platform approach enables discovery of potent, selective and ligand-competitive cyclic peptides targeting the GIP receptor

In any drug discovery effort, the identification of hits for further optimisation is of crucial importance. For peptide therapeutics, display technologies such as mRNA display have emerged as powerful methodologies to identify these desired de novo hit ligands against targets of interest. The diverse peptide libraries are genetically encoded in these technologies, allowing for next-generation sequencing to be used to efficiently identify the binding ligands. Despite the vast datasets that can be generated, current downstream methodologies, however, are limited by low throughput validation processes, including hit prioritisation, peptide synthesis, biochemical and biophysical assays. In this work we report a highly efficient strategy that combines bioinformatic analysis with state-of-the-art high throughput peptide synthesis to identify nanomolar cyclic peptide (CP) ligands of the human glucose-dependent insulinotropic peptide receptor (hGIP-R). Furthermore, our workflow is able to discriminate between functional and remote binding non-functional ligands. Efficient structure-activity relationship analysis (SAR) combined with advanced in silico structural studies allow deduction of a thorough and holistic binding model which informs further chemical optimisation, including efficient half-life extension. We report the identification and design of the first de novo, GIP-competitive, incretin receptor family-selective CPs, which exhibit an in vivo half-life up to 10.7 h in rats. The workflow should be generally applicable to any selection target, improving and accelerating hit identification, validation, characterisation, and prioritisation for therapeutic development.

Progress and limitations of oral peptide delivery as a potentially transformative therapy

INTRODUCTION

The oral delivery of peptides offers advantages over the injectable route of administration due to patient convenience. However, oral delivery remains challenging due to physiological barriers. Numerous formulation technologies have been developed to overcome these challenges, and understanding the advantages and limitations of each technology is important for the development of new delivery systems to enable oral delivery of peptides designed for parenteral administration.

AREAS COVERED

This review summarizes key learnings from the use of permeation enhancers (PEs) for oral peptide delivery associated with solid dosage form optimization to maximize the PE effect. Furthermore, we will highlight the most recent emerging delivery strategies to improve oral peptide bioavailability such as nanoparticles, self-emulsifying drug delivery systems, gut shuttles, and ingestible devices. In addition, advantages and limitations of these technologies will be compared with the permeation enhancer technology.

EXPERT OPINION

Despite the success of permeation enhancer technology in the FDA approved oral peptide products for gastric and intestinal delivery, oral peptide delivery is still facing the immense challenge of low-to-single digit oral bioavailability and the impact of food and water intake on oral absorption. Optimization of drug product attributes such as dissolution kinetics is critical to overcome spreading and dilution effects in vivo to improve permeation enhancer efficacy. The next frontiers to substantially increase oral bioavailability and transform injectable peptides to oral deliverables may be ingestible devices and gut shuttles. In addition, ingestible devices may have potential to overcome the impact of food on oral bioavailability. However, clinical studies are necessary to inform the safety and efficacy of these emerging technologies.

Molecular Engineering of Efficacious Mono-Valent Ultra-Long Acting Two-Chain Insulin-Fc Conjugates

Here, we describe molecular engineering of monovalent ultra-long acting two-chain insulin-Fc conjugates. Insulin-Fc conjugates were synthesized using trifunctional linkers with one amino reactive group for reaction with a lysine residue of insulin and two thiol reactive groups used for re-bridging of a disulfide bond within the Fc molecule. The ultra-long pharmacokinetic profile of the insulin-Fc conjugates was the result of concertedly slowing insulin receptor-mediated clearance by (1) introduction of amino acid substitutions that lowered the insulin receptor affinity and (2) conjugating insulin to the Fc element. Fc conjugation leads to recycling by the neonatal Fc receptor and increase in the molecular size, both contributing to the ultra-long pharmacokinetic and pharmacodynamic profiles.

One-hundred year evolution of prandial insulin preparations: From animal pancreas extracts to rapid-acting analogs

The first insulin preparation injected in humans in 1922 was short-acting, extracted from animal pancreas, contaminated by impurities. Ever since the insulin extracted from animal pancreas has been continuously purified, until an unlimited synthesis of regular human insulin (RHI) became possible in the '80s using the recombinant-DNA (rDNA) technique. The rDNA technique then led to the designer insulins (analogs) in the early '90s. Rapid-acting insulin analogs were developed to accelerate the slow subcutaneous (sc) absorption of RHI, thus lowering the 2-h post-prandial plasma glucose (PP-PG) and risk for late hypoglycemia as comparing with RHI. The first rapid-acting analog was lispro (in 1996), soon followed by aspart and glulisine. Rapid-acting analogs are more convenient than RHI: they improve early PP-PG, and 24-h PG and A1C as long as basal insulin is also optimized; they lower the risk of late PP hypoglycemia and they allow a shorter time-interval between injection and meal. Today rapid-acting analogs are the gold standard prandial insulins. Recently, even faster analogs have become available (faster aspart, ultra-rapid lispro) or are being studied (Biochaperone lispro), making additional gains in lowering PP-PG. Rapid-acting analogs are recommended in all those with type 1 and type 2 diabetes who need prandial insulin replacement.

Future directions in insulin therapy

Insulin therapy has a long history at the cutting edge of technological development through purification, extended-action, molecular chemistry, and devices, and in support technologies including self-measurement and patient education. But unmet needs remain large. Today's therapy cannot deliver minute-to-minute control of glucose levels, and cannot imitate the reflex/incretin driven physiological insulin delivery at mealtimes. Further it depends on a raft of devices for administration several times a day, devices liked for their functionality, but disliked as an intrusive reminder of the condition, several times a day. Approaches to overcoming these barriers include closed-loop systems and further modification of insulin formulations, but are limited by fundamental underlying difficulties. While clinical studies of oral insulin are in progress, the barriers to success look daunting. Development of small-molecule approaches (insulin-mimetic tablets) appears to have stalled, while concepts for glucose-responsive insulin as yet fail to deliver the necessary insulin-to-glucose gradient. Gene therapy, feasible in animals in preliminary studies, is not capable of providing feedback control. Transplantation of cultured islets and islet B-cells from stem cells thus looks to the be the best long-term prospect for insulin delivery in terms of overcoming the above barriers, but is a true biotechnological tour-de-force which will take time to mature.

Molecular and pharmacological characterization of insulin icodec: a new basal insulin analog designed for once-weekly dosing

INTRODUCTION

Insulin icodec is a novel, long-acting insulin analog designed to cover basal insulin requirements with once-weekly subcutaneous administration. Here we describe the molecular engineering and the biological and pharmacological properties of insulin icodec.

RESEARCH DESIGN AND METHODS

A number of in vitro assays measuring receptor binding, intracellular signaling as well as cellular metabolic and mitogenic responses were used to characterize the biological properties of insulin icodec. To evaluate the pharmacological properties of insulin icodec in individuals with type 2 diabetes, a randomized, double-blind, double-dummy, active-controlled, multiple-dose, dose escalation trial was conducted.

RESULTS

The long half-life of insulin icodec was achieved by introducing modifications to the insulin molecule aiming to obtain a safe, albumin-bound circulating depot of insulin icodec, providing protracted insulin action and clearance. Addition of a C20 fatty diacid-containing side chain imparts strong, reversible albumin binding, while three amino acid substitutions (A14E, B16H and B25H) provide molecular stability and contribute to attenuating insulin receptor (IR) binding and clearance, further prolonging the half-life. In vitro cell-based studies showed that insulin icodec activates the same dose-dependent IR-mediated signaling and metabolic responses as native human insulin (HI). The affinity of insulin icodec for the insulin-like growth factor-1 receptor was proportionately lower than its binding to the IR, and the in vitro mitogenic effect of insulin icodec in various human cells was low relative to HI. The clinical pharmacology trial in people with type 2 diabetes showed that insulin icodec was well tolerated and has pharmacokinetic/pharmacodynamic properties that are suited for once-weekly dosing, with a mean half-life of 196 hours and close to even distribution of glucose-lowering effect over the entire dosing interval of 1 week.

CONCLUSIONS

The molecular modifications introduced into insulin icodec provide a novel basal insulin with biological and pharmacokinetic/pharmacodynamic properties suitable for once-weekly dosing.

TRIAL REGISTRATION NUMBER

NCT02964104.

Prevention of diabetes-associated fibrosis: Strategies in FcRn-targeted nanosystems for oral drug delivery

Diabetes mellitus is a chronic disease with an elevated risk of micro- and macrovascular complications, such as fibrosis. To prevent diabetes-associated fibrosis, the symptomatology of diabetes must be controlled, which is commonly done by subcutaneous injection of antidiabetic peptides. To minimize the pain and distress associated with such injections, there is an urgent need for non-invasive oral transmucosal drug delivery strategies. However, orally administered peptide-based drugs are exposed to harsh conditions in the gastrointestinal tract and poorly cross the selective intestinal epithelium. Thus, targeting of drugs to receptors expressed in epithelial cells, such as the neonatal Fc receptor (FcRn), may therefore enhance uptake and transport through mucosal barriers. This review compiles how in-depth studies of FcRn biology and engineering of receptor-binding molecules may pave the way for design of new classes of FcRn-targeted nanosystems. Tailored strategies may open new avenues for oral drug delivery and provide better treatment options for diabetes and, consequently, fibrosis prevention.

Commemorating insulin's centennial: engineering insulin pharmacology towards physiology

The life-saving discovery of insulin in Toronto in 1921 is one of the most impactful achievements in medical history, at the time being hailed as a miracle treatment for diabetes. The insulin molecule itself, however, is poorly amenable as a pharmacological intervention, and the formidable challenge of optimizing insulin therapy has been ongoing for a century. We review early academic insights into insulin structure and its relation to self-association and receptor binding, as well as recombinant biotechnology, which have all been seminal for drug design. Recent developments have focused on combining genetic and chemical engineering with pharmaceutical optimization to generate ultra-rapid and ultra-long-acting, tissue-selective, or orally delivered insulin analogs. We further discuss these developments and propose that future scientific efforts in molecular engineering include realizing the dream of glucose-responsive insulin delivery.

Molecular Engineering of Insulin Icodec, the First Acylated Insulin Analog for Once-Weekly Administration in Humans

Here, we describe the molecular engineering of insulin icodec to achieve a plasma half-life of 196 h in humans, suitable for once-weekly subcutaneously administration. Insulin icodec is based on re-engineering of the ultra-long oral basal insulin OI338 with a plasma half-life of 70 h in humans. This systematic re-engineering was accomplished by (1) further increasing the albumin binding by changing the fatty diacid from a 1,18-octadecanedioic acid (C18) to a 1,20-icosanedioic acid (C20) and (2) further reducing the insulin receptor affinity by the B16Tyr → His substitution. Insulin icodec was selected by screening for long intravenous plasma half-life in dogs while ensuring glucose-lowering potency following subcutaneous administration in rats. The ensuing structure-activity relationship resulted in insulin icodec. In phase-2 clinical trial, once-weekly insulin icodec provided safe and efficacious glycemic control comparable to once-daily insulin glargine in type 2 diabetes patients. The structure-activity relationship study leading to insulin icodec is presented here.

Review: Glucose-sensitive insulin

BACKGROUND

Hypoglycemia, the condition of low blood sugar, is a common occurance in people with diabetes using insulin therapy. Protecting against hypoglycaemia by engineering an insulin preparation that can auto-adjust its biological activity to fluctuating blood glucose levels has been pursued since the 1970s, but despite numerous publications, no system that works well enough for practical use has reached clinical practise.

SCOPE OF REVIEW

This review will summarise and scrutinise known approaches for producing glucose-sensitive insulin therapies. Notably, systems described in patent applications will be extensively covered, which has not been the case for earlier reviews of this area.

MAJOR CONCLUSIONS

The vast majority of published systems are not suitable for product development, but a few glucose-sensitive insulin concepts have recently reached clinical trials, and there is hope that glucose-sensitive insulin will become available to people with diabetes in the near future.

The Chemical Synthesis of Insulin: An Enduring Challenge

The pancreatic peptide hormone insulin, first discovered exactly 100 years ago, is essential for glycemic control and is used as a therapeutic for the treatment of type 1 and, increasingly, type 2 diabetes. With a worsening global diabetes epidemic and its significant health budget imposition, there is a great demand for new analogues possessing improved physical and functional properties. However, the chemical synthesis of insulin's intricate 51-amino acid, two-chain, three-disulfide bond structure, together with the poor physicochemical properties of both the individual chains and the hormone itself, has long represented a major challenge to organic chemists. This review provides a timely overview of the past efforts to chemically assemble this fascinating hormone using an array of strategies to enable both correct folding of the two chains and selective formation of disulfide bonds. These methods not only have contributed to general peptide synthesis chemistry and enabled access to the greatly growing numbers of insulin-like and cystine-rich peptides but also, today, enable the production of insulin at the synthetic efficiency levels of recombinant DNA expression methods. They have led to the production of a myriad of novel analogues with optimized structural and functional features and of the feasibility for their industrial manufacture.

Oral Coadministration of Zn-Insulin with d-Form Small Intestine-Permeable Cyclic Peptide Enhances Its Blood Glucose-Lowering Effect in Mice

Oral delivery of insulin remains a challenge owing to its poor permeability across the small intestine and enzymatic digestion in the gastrointestinal tract. In a previous study, we identified a small intestine-permeable cyclic peptide, C-DNPGNET-C (C-C disulfide bond, cyclic DNP peptide), which facilitated the permeation of macromolecules. Here, we showed that intraintestinal and oral coadministration of insulin with the cyclic DNP derivative significantly reduced blood glucose levels by increasing the portal plasma insulin concentration following permeation across the small intestine of mice. We also found that protecting the cyclic DNP derivative from enzymatic digestion in the small intestine of mice using d-amino acids and by the cyclization of DNP peptide was essential to enhance cyclic DNP derivative-induced insulin absorption across the small intestine. Furthermore, intraintestinal and oral coadministration of insulin hexamer stabilized by zinc ions (Zn-insulin) with cyclic D-DNP derivative was more effective in facilitating insulin absorption and inducing hypoglycemic effects in mice than the coadministration of insulin with the cyclic D-DNP derivative. Moreover, Zn-insulin was more resistant to degradation in the small intestine of mice compared to insulin. Intraintestinal and oral coadministration of Zn-insulin with cyclic DNP derivative also reduced blood glucose levels in a streptozotocin-induced diabetes mellitus mouse model. A single intraintestinal administration of the cyclic D-DNP derivative did not induce any cytotoxicity, either locally in the small intestine or systemically. In summary, we demonstrated that coadministration of Zn-insulin with cyclic D-DNP derivative could enhance oral insulin absorption across the small intestine in mice.

Engineering of Orally Available, Ultralong-Acting Insulin Analogues: Discovery of OI338 and OI320

Recently, the first basal oral insulin (OI338) was shown to provide similar treatment outcomes to insulin glargine in a phase 2a clinical trial. Here, we report the engineering of a novel class of basal oral insulin analogues of which OI338, 10, in this publication, was successfully tested in the phase 2a clinical trial. We found that the introduction of two insulin substitutions, A14E and B25H, was needed to provide increased stability toward proteolysis. Ultralong pharmacokinetic profiles were obtained by attaching an albumin-binding side chain derived from octadecanedioic (C18) or icosanedioic acid (C20) to the lysine in position B29. Crucial for obtaining the ultralong PK profile was also a significant reduction of insulin receptor affinity. Oral bioavailability in dogs indicated that C18-based analogues were superior to C20-based analogues. These studies led to the identification of the two clinical candidates OI338 and OI320 (10 and 24, respectively).