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

Pharmacokinetics and oral bioavailability of ampicillin and its prodrug bacampicillin in chickens and turkeys

IMPORTANCE

Reports comparing the pharmacokinetics of ampicillin (AMP) and its prodrug bacampicillin (BAC) in poultry are scarce.

OBJECTIVE

This study evaluated the pharmacokinetic characteristics of AMP and BAC in chickens and turkeys after intravenous (i.v.) or oral administrations at a single dosage of 25 mg/kg body weight.

METHODS

Thirty chickens and 30 turkeys were divided into three groups (n = 10). Blood samples (0.5-0.7 mL) were collected from the subcutenea ulnar vein at pre-assigned times up to 12 h. The AMP and BAC plasma concentrations were analyzed using high-performance liquid chromatography with a fluorescence detector. The data were analyzed using noncompartmental methods.

RESULTS

The area under the curve from 0 to 12 h, apparent total systemic, the apparent volume of distribution, and mean residence time differed significantly according to the administration routes. The terminal elimination half-life values for the i.v. AMP, oral AMP, and oral BAC routes were 1.81, 3.64, and 5.39 h (p = 0.0249, p < 0.05), respectively, in chickens, and 2.44, 2.53, and 5.5 h (p < 0.0001), respectively, in turkeys. The bioavailability for the oral AMP and oral BAC groups in chickens was 25.9% and 44.6%, respectively. Similarly, in turkeys, the bioavailability was 19.1% and 44.2% for the oral AMP and oral BAC groups, respectively.

CONCLUSIONS AND RELEVANCE

The oral route of BAC with good bioavailability can be preferred for treating various conditions. On the other hand, further studies will be needed to determine the clinical efficacy of BAC during bacterial infections and the pharmacokinetics and safety of repeated administration in poultry.

Molecular Investigation of SNAC as an Oral Peptide Permeation Enhancer in Lipid Membranes via Solid-State NMR

Oral peptide therapeutics are increasingly favored in the pharmaceutical industry for their ease of use and better patient adherence. However, they face challenges with poor oral bioavailability due to their high molecular weight and surface polarity. Permeation enhancers (PEs) like salcaprozate sodium (SNAC) have shown promise in clinical trials, achieving about 1% bioavailability. One proposed mechanism for enhancing permeation is membrane perturbation or fluidization, though direct experimental proof and quantitative analysis of these effects are still needed. This study employs solid-state NMR (ssNMR) to investigate how SNAC interacts with hydrated DMPC liposomes, measuring enhancements in membrane fluidity across interfacial and transmembrane regions. The methodology involves analyzing phosphate lipid headgroups and acyl chains using static 31P chemical shift anisotropy and 2H quadrupolar coupling measurements alongside 1H and 13C magic angle spinning NMR for motional averaging of 1H-1H and 1H-13C dipolar couplings. Our findings indicate an overall increase in the uniaxial motion of phospholipids with SNAC in a PE concentration-dependent manner. It boosts lipid headgroup dynamics and enhancement plateaus at 25% between 24 and 72 mM concentrations. SNAC effectively enhances the fluidity of the hydrophobic center by 43% at 72 mM PE concentration, more significantly than the interfacial region. It is worth noting that the extent of liposome dissolution and conversion to micelles increases as SNAC concentration rises. Including a model peptide drug, octreotide, introduces a competitive equilibrium in this complex PE-lipid-peptide system, further influencing membrane dynamics for peptide permeation. Interestingly, the membrane enhancement does not show the expected plateau, and a less significant lipid mobility increase is observed in the presence of octreotide, suggesting a less substantial impact compared to peptide-free systems, which is likely due to peptide-PE interactions that consume monomeric SNAC, reducing its interaction with the lipid membrane. This study provides the first quantitative and site-specific ssNMR measurements of membrane mobility influenced by one representative PE as a snapshot of PE lipid interaction in a liposome model, demonstrating how peptide drugs modulate competitive equilibria and PE-induced lipid dynamics.

Spatiotemporal dynamics of microscopic biological barrier visualized by electric-double-layer modulation imaging

Live-cell label-free imaging of a microscopic biological barrier, generally referred to as 'tight junction', was realized by a recently developed electric-double-layer modulation imaging (EDLMI). The method allowed quantitative imaging of barrier integrity in real time, thus being an upper compatible of transepithelial electrical resistance (TEER) which is a conventional standard technique to evaluate spatially averaged barrier integrity. We demonstrate that the quantitative and real-time imaging capability of EDLMI unveils fundamental dynamics of biological barrier, some of which are totally different from conventional understandings.

Overcoming Challenges in Small-Molecule Drug Bioavailability: A Review of Key Factors and Approaches

The bioavailability of small-molecule drugs remains a critical challenge in pharmaceutical development, significantly impacting therapeutic efficacy and commercial viability. This review synthesizes recent advances in understanding and overcoming bioavailability limitations, focusing on key physicochemical and biological factors influencing drug absorption and distribution. We examine cutting-edge strategies for enhancing bioavailability, including innovative formulation approaches, rational structural modifications, and the application of artificial intelligence in drug design. The integration of nanotechnology, 3D printing, and stimuli-responsive delivery systems are highlighted as promising avenues for improving drug delivery. We discuss the importance of a holistic, multidisciplinary approach to bioavailability optimization, emphasizing early-stage consideration of ADME properties and the need for patient-centric design. This review also explores emerging technologies such as CRISPR-Cas9-mediated personalization and microbiome modulation for tailored bioavailability enhancement. Finally, we outline future research directions, including advanced predictive modeling, overcoming biological barriers, and addressing the challenges of emerging therapeutic modalities. By elucidating the complex interplay of factors affecting bioavailability, this review aims to guide future efforts in developing more effective and accessible small-molecule therapeutics.

The Bidirectional Relationship Between Cardiovascular Medications and Oral and Gut Microbiome Health: A Comprehensive Review

Cardiovascular diseases (CVDs) are a leading cause of widespread morbidity and mortality. It has been found that the gut and oral microbiomes differ in individuals with CVDs compared to healthy individuals. Patients with CVDs often require long-term pharmacological interventions. While these medications have been extensively studied for their cardiovascular benefits, emerging research indicates that they may also impact the diversity and composition of the oral and gut microbiomes. However, our understanding of how these factors influence the compositions of the oral and gut microbiomes in individuals remains limited. Studies have shown that statins and beta-blockers, in particular, cause gut and oral microbial dysbiosis, impacting the metabolism and absorption of these medications. These alterations can lead to variations in drug responses, highlighting the need for personalized treatment approaches. The microbiome's role in drug metabolism and the impact of CVD medications on the microbiome are crucial in understanding these variations. However, there are very few studies in this area, and not all medications have been studied, emphasizing the necessity for further research to conclusively establish cause-and-effect relationships and determine the clinical significance of these interactions. This review will provide evidence of how the oral and gut microbiomes in patients with cardiovascular diseases (CVDs) interact with specific drugs used in CVD treatment.

Alternative routes for parenteral nucleic acid delivery and related hurdles: highlights in RNA delivery

INTRODUCTION

Nucleic acid-based therapies are promising advancements in medicine. They offer unparalleled efficacy in treating previously untreatable diseases through precise gene manipulation techniques. However, the challenge of achieving targeted delivery to specific cells remains a significant obstacle.

AREAS COVERED

This review thoroughly examines the physicochemical properties of nucleic acids, focusing on their interaction with carriers and exploring various delivery routes, including oral, pulmonary, ocular, and dermal routes. It also examines the nonviral vector delivery efficiency of nucleic acids, focusing on RNA, and provides regulatory landscapes.

EXPERT OPINION

The role of carriers in improving the effectiveness of nucleic acid-based therapies is emphasized. The discussion of published results covers regulatory frameworks, including insights into European Medicines Agency guidelines. It highlights cutting-edge biotechnological innovations and a quality-by-design approach that could facilitate clinical translation and smooth regulatory obstacles.

Gastrointestinal Permeation Enhancers Beyond Sodium Caprate and SNAC - What is Coming Next?

Oral peptide delivery is trending again. Among the possible reasons are the recent approvals of two oral peptide formulations, which represent a huge stride in the field. For the first time, gastrointestinal (GI) permeation enhancers (PEs) are leveraged to overcome the main limitation of oral peptide delivery-low permeability through the intestinal epithelium. Despite some success, the application of current PEs, such as salcaprozate sodium (SNAC), sodium caprylate (C8), and sodium caprate (C10), is generally resulting in relatively low oral bioavailabilities (BAs)-even for carefully selected therapeutics. With several hundred peptide-based drugs presently in the pipeline, there is a huge unmet need for more effective PEs. Aiming to provide useful insights for the development of novel PEs, this review summarizes the biological hurdles to oral peptide delivery with special emphasis on the epithelial barrier. It describes the concepts and action modes of PEs and mentions possible new targets. It further states the benchmark that is set by current PEs, while critically assessing and evaluating emerging PEs regarding translatability, safety, and efficacy. Additionally, examples of novel PEs under preclinical and clinical evaluation and future directions are discussed.

LabrafacTM MC60 is an efficacious intestinal permeation enhancer for macromolecules: Comparisons with Labrasol® ALF in ex vivo and in vivo rat studies

Labrafac™ MC60 (glycerol monocaprylocaprate) is a lipid-based excipient used in oral formulations as a solubiliser. Due to the high proportions of established permeability enhancers, caprylate (C8) and caprate (C10), in Labrafac™ MC60, we hypothesised that it might behave as an intestinal permeation enhancer. We therefore evaluated this using two paracellular markers (ex vivo) and insulin (in vivo) as model molecules. Ex vivo studies were conducted in isolated muscle-stripped rat colonic mucosae mounted in Ussing chambers. Apical addition of Labrafac™ MC60 (8, 12, and 16 mg/ml) enhanced the apparent permeability coefficients (Papp) of [14C] mannitol and FITC-dextran 4 kDa (FD4) across colonic mucosae. Similar effects were observed in isolated jejunal mucosae, but at higher concentrations (40 mg/ml). The enhancing capacity of Labrafac™ MC60 was transient due to reversibility of reductions in transepithelial electrical resistance (TEER) upon wash-out and effects on fluxes were molecular weight-dependent (MW) as suggested by fluxes of a set of high MW FITC-dextrans. The permeability enhancing effects of Labrafac™ MC60 ex vivo were maintained in the presence of simulated intestinal fluids, FaSSIF and FaSSCoF, in both jejunal and colonic mucosae, respectively. Following intra-intestinal regional instillations to rats, the relative bioavailability of 50 IU/kg insulin ad-mixed with Labrafac™ MC60 was 5 % in jejunum (40 mg/ml) and 6 % in colon (8 mg/ml). When Labrafac™ MC60 was combined with PEG-60 hydrogenated castor oil (1 % v/v), this further increased the bioavailability of insulin to 8 % in jejunum. Absorption enhancement was also maintained in the presence of FaSSIF in jejunal instillations. Histology after 120 min exposure to Labrafac™ MC60 in vivo for both jejunum and colon was similar to untreated control. Labrafac™ MC60 therefore acts as a non-damaging intestinal permeation enhancer for macromolecules and can be considered as another excipient in screening programmes to develop orally administered macromolecules.

Validation of the Absorption-Enhancing Ability of Oligoarginines Grafted onto a Backbone of Hyaluronic Acid through Animal Studies from Rodents to Primates

The purpose of our research is to develop functional additives that enhance mucosal absorption of biologics, such as peptide/protein and antibody drugs, to provide their non-to-poor invasive dosage forms self-managed by patients. Our previous in vivo and in vitro studies demonstrated that the intranasal absorption of biologics in mice was significantly improved when coadministered with oligoarginines anchored chemically to hyaluronic acid via a glycine spacer, presumably through syndecan-4-mediated macropinocytosis under activation by oligoarginines. The present mouse experiments first revealed that diglycine-L-tetraarginine-linked hyaluronic acid significantly enhanced the intranasal absorption of sulpiride, which is a poor-absorptive organic compound with a low molecular weight. However, similar enhancement was not observed for levofloxacin, which has a similarly low molecular weight but is a well-absorptive organic compound, probably because its absorption was mostly dominated by passive diffusion. The subsequent monkey experiments revealed that there was no species difference in the absorption-enhancing ability of diglycine-L-tetraarginine-linked hyaluronic acid for not only organic compounds but also biologics. This was presumably because the expression levels of endocytosis-associated membrane proteins on the nasal mucosa in monkeys were almost equivalent to those in mice, and poorly membrane-permeable/membrane-impermeable drugs were mainly absorbed via syndecan-4-mediated macropinocytosis, regardless of animal species. Drug concentrations in the brain assessed in mice and monkeys and those in the cerebral spinal fluids (CSFs) assessed in monkeys indicated that drugs would be delivered from the systemic circulation to the central nervous system by crossing the blood-brain and the blood-CSF barriers under coadministration with the hyaluronic acid derivative. In line with our original hypothesis, this new set of data supported that our oligoarginine-linked hyaluronic acid would locally perform on the mucosal surface and enhance the membrane permeation of drugs under its colocalization.

Evaluating the oral delivery of GalNAc-conjugated siRNAs in rodents and non-human primates

Oral delivery is the most widely used and convenient route of administration of medicine. However, oral administration of hydrophilic macromolecules is commonly limited by low intestinal permeability and pre-systemic degradation in the gastrointestinal (GI) tract. Overcoming some of these challenges allowed emergence of oral dosage forms of peptide-based drugs in clinical settings. Antisense oligonucleotides (ASOs) have also been investigated for oral administration but despite the recent progress, the bioavailability remains low. Given the advancement with highly potent and durable trivalent N-acetylgalactosamine (GalNAc)-conjugated small interfering RNAs (siRNAs) via subcutaneous (s.c.) injection, we explored their activities after oral administration. We report robust RNA interference (RNAi) activity of orally administrated GalNAc-siRNAs co-formulated with permeation enhancers (PEs) in rodents and non-human primates (NHPs). The relative bioavailability calculated from NHP liver exposure was <2.0% despite minimal enzymatic degradation in the GI. To investigate the impact of oligonucleotide size on oral delivery, highly specific GalNAc-conjugated single-stranded oligonucleotides known as REVERSIRs with different lengths were employed and their activities for reversal of RNAi effect were monitored. Our data suggests that intestinal permeability is highly influenced by the size of oligonucleotides. Further improvements in the potency of siRNA and PE could make oral delivery of GalNAc-siRNAs as a practical solution.

Interactions of oral permeation enhancers with lipid membranes in simulated intestinal environments

The oral bioavailability of therapeutic peptides is generally low. To increase peptide transport across the gastrointestinal barrier, permeation enhancers are often used. Despite their widespread use, mechanistic knowledge of permeation enhancers is limited. To address this, we here investigate the interactions of six commonly used permeation enhancers with lipid membranes in simulated intestinal environments. Specifically, we study the interactions of the permeation enhancers sodium caprate, dodecyl maltoside, sodium cholate, sodium dodecyl sulfate, melittin, and penetratin with epithelial cell-like model membranes. To mimic the molecular composition of the real intestinal environment, the experiments are performed with two peptide drugs, salmon calcitonin and desB30 insulin, in fasted-state simulated intestinal fluid. Besides providing a comparison of the membrane interactions of the studied permeation enhancers, our results demonstrate that peptide drugs as well as intestinal-fluid components may substantially change the membrane activity of permeation enhancers. This highlights the importance of testing permeation enhancement in realistic physiological environments and carefully choosing a permeation enhancer for each individual peptide drug.

Recent Progress in the Oral Delivery of Therapeutic Peptides and Proteins: Overview of Pharmaceutical Strategies to Overcome Absorption Hurdles

Purpose

Proteins and peptides have secured a place as excellent therapeutic moieties on account of their high selectivity and efficacy. However due to oral absorption limitations, current formulations are mostly delivered parenterally. Oral delivery of peptides and proteins (PPs) can be considered the need of the hour due to the immense benefits of this route. This review aims to critically examine and summarize the innovations and mechanisms involved in oral delivery of peptide and protein drugs.

Methods

Comprehensive literature search was undertaken, spanning the early development to the current state of the art, using online search tools (PubMed, Google Scholar, ScienceDirect and Scopus).

Results

Research in oral delivery of proteins and peptides has a rich history and the development of biologics has encouraged additional research effort in recent decades. Enzyme hydrolysis and inadequate permeation into intestinal mucosa are the major causes that result in limited oral absorption of biologics. Pharmaceutical and technological strategies including use of absorption enhancers, enzyme inhibition, chemical modification (PEGylation, pro-drug approach, peptidomimetics, glycosylation), particulate delivery (polymeric nanoparticles, liposomes, micelles, microspheres), site-specific delivery in the gastrointestinal tract (GIT), membrane transporters, novel approaches (self-nanoemulsifying drug delivery systems, Eligen technology, Peptelligence, self-assembling bubble carrier approach, luminal unfolding microneedle injector, microneedles) and lymphatic targeting, are discussed. Limitations of these strategies and possible innovations for improving oral bioavailability of protein and peptide drugs are discussed.

Conclusion

This review underlines the application of oral route for peptide and protein delivery, which can direct the formulation scientist for better exploitation of this route.

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.

Current Advancements on Oral Protein and Peptide Drug Delivery Approaches to Bioavailability: Extensive Review on Patents

Protein and peptide-based drugs have greater therapeutic efficacy and potential application and lower toxicity compared to chemical entities in long-term use within optimum concentration as they are easily biodegradable due to biological origin. While oral administration is preferable, most of these substances are currently administered intravenously or subcutaneously. This is primarily due to the breakdown and poor absorption in the GI tract. Hence, ongoing research is focused on investigating absorption enhancers, enzyme inhibitors, carrier systems, and stability enhancers as potential strategies to facilitate the oral administration of proteins and peptides. Investigations have been directed towards advancing novel technologies to address gastrointestinal (GI) barriers associated with protein and peptide medications. The current review intensifies formulation and stability approaches for oral protein & peptide drug delivery systems with all significant parameters intended for patient safety. Notably, certain innovative technologies have been patented and are currently undergoing clinical trials or have already been introduced into the market. All the approaches stated for the administration of protein and peptide drugs are critically discussed, having their current status, future directions, and recent patents published in the last decades.

Safety of surfactant excipients in oral drug formulations

Surfactants are a diverse group of compounds that share the capacity to adsorb at the boundary between distinct phases of matter. They are used as pharmaceutical excipients, food additives, emulsifiers in cosmetics, and as household/industrial detergents. This review outlines the interaction of surfactant-type excipients present in oral pharmaceutical dosage forms with the intestinal epithelium of the gastrointestinal (GI) tract. Many surfactants permitted for human consumption in oral products reduce intestinal epithelial cell viability in vitro and alter barrier integrity in epithelial cell monolayers, isolated GI tissue mucosae, and in animal models. This suggests a degree of mis-match for predicting safety issues in humans from such models. Recent controversial preclinical research also infers that some widely used emulsifiers used in oral products may be linked to ulcerative colitis, some metabolic disorders, and cancers. We review a wide range of surfactant excipients in oral dosage forms regarding their interactions with the GI tract. Safety data is reviewed across in vitro, ex vivo, pre-clinical animal, and human studies. The factors that may mitigate against some of the potentially abrasive effects of surfactants on GI epithelia observed in pre-clinical studies are summarised. We conclude with a perspective on the overall safety of surfactants in oral pharmaceutical dosage forms, which has relevance for delivery system development.

Systems Biology and Peptide Engineering to Overcome Absorption Barriers for Oral Peptide Delivery: Dosage Form Optimization Case Study Preceding Clinical Translation

Oral delivery of peptides and biological molecules promises significant benefits to patients as an alternative to daily injections, but the development of these formulations is challenging due to their low bioavailability and high pharmacokinetic variability. Our earlier work focused on the discovery of MEDI7219, a stabilized, lipidated, glucagon-like peptide 1 agonist peptide, and the selection of sodium chenodeoxycholate (Na CDC) and propyl gallate (PG) as permeation enhancer combinations. We hereby describe the development of the MEDI7219 tablet formulations and composition optimization via in vivo studies in dogs. We designed the MEDI7219 immediate-release tablets with the permeation enhancers Na CDC and PG. Immediate-release tablets were coated with an enteric coating that dissolves at pH ≥ 5.5 to target the upper duodenal region of the gastrointestinal tract and sustained-release tablets with a Carbopol bioadhesive polymer were coated with an enteric coating that dissolves at pH ≥ 7.0 to provide a longer presence at the absorption site in the gastrointestinal tract. In addition to immediate- and enteric-coated formulations, we also tested a proprietary delayed release erodible barrier layer tablet (OralogiKTM) to deliver the payload to the target site in the gastrointestinal tract. The design of tablet dosage forms based on the optimization of formulations resulted in up to 10.1% absolute oral bioavailability in dogs with variability as low as 26% for MEDI7219, paving the way for its clinical development.

Structural-Activity Relationship-Inspired the Discovery of Saturated Fatty Acids as Novel Colistin Enhancers

The emergence and prevalence of mobile colistin resistance gene mcr have dramatically compromised the clinical efficacy of colistin, a cyclopeptide antibiotic considered to be the last option for treating different-to-treat infections. The combination strategy provides a productive and cost-effective strategy to expand the lifespan of existing antibiotics. Structural-activity relationship analysis of polymyxins indicates that the fatty acyl chain plays an indispensable role in their antibacterial activity. Herein, it is revealed that three saturated fatty acids (SFAs), especially sodium caprate (SC), substantially potentiate the antibacterial activity of colistin against mcr-positive bacteria. The combination of SFAs and colistin effectively inhibits biofilm formation and eliminates matured biofilms, and is capable of preventing the emergence and spread of mobile colistin resistance. Mechanistically, the addition of SFAs reduces lipopolysaccharide (LPS) modification by simultaneously promoting LPS biosynthesis and inhibiting the activity of MCR enzyme, enhance bacterial membrane damage, and impair the proton motive force-dependent efflux pump, thereby boosting the action of colistin. In three animal models of infection by mcr-positive pathogens, SC combined with colistin exhibit an excellent therapeutic effect. These findings indicate the therapeutic potential of SFAs as novel antibiotic adjuvants for the treatment of infections caused by multidrug-resistant bacteria in combination with colistin.

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.

Current screening, design, and delivery approaches to address low permeability of chemically synthesized modalities in drug discovery and early clinical development

A drug's permeability across biological membranes is a key property associated with the successful development of an orally absorbed drug candidate. Although a variety of methods are available for predicting and assessing permeability, some are more preferred than others at specific stages of drug discovery and development across the pharmaceutical industry. Permeability measurements may be interpreted differently depending on the chosen method. Herein, we present a refreshed perspective on the screening approaches and philosophy in permeability evaluation, from early drug discovery to early clinical development. Additionally, we review and discuss chemical design and drug delivery technologies that can be leveraged to overcome permeability challenges, which are increasingly being used with emerging modalities.

SNAC for Enhanced Oral Bioavailability: An Updated Review

The delivery of proteins and peptides via an oral route poses numerous challenges to improve the oral bioavailability and patient compliance. To overcome these challenges, as well as to improve the permeation of proteins and peptides via intestinal mucosa, several chemicals have been studied such as surfactants, fatty acids, bile salts, pH modifiers, and chelating agents, amongst these medium chain fatty acid like C10 (sodium caprate) and Sodium N-[8-(2-hydroxybenzoyl) amino] caprylate (SNAC) and its derivatives that have been well studied from a clinical perspective. This current review enumerates the challenges involved in protein and peptide delivery via the oral route, i.e., non-invasive routes of protein and peptide administration. This review also covers the chemistry behind SNAC and toxicity as well as mechanisms to enhance the oral delivery of clinically proven molecules like simaglutide and other small molecules under clinical development, as well as other permeation enhancers for efficient delivery of proteins and peptides.

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.

Structure-activity relationship of a peptide permeation enhancer

The pentapeptide L-R5 has previously been shown to transiently increase the permeability of nasal epithelial cell layers in vitro, allowing paracellular transport of molecules of up to 4 kDa. Protein kinase C zeta (PKC ζ), a member of a family of serine/threonine kinases was shown to be involved in tight junction modulation induced by L-R5. We show here that the ability of L-R5 to modulate tight junctions is comparable to other permeability enhancers such as bilobalide, latrunculin A or C₁₀. Interaction of the peptide with the target protein occurs via electrostatic interaction, with the presence of positive charges being essential for its functionality. L-R5 is myristoylated to allow quick cell entry and onset of activity. While no epithelial cytotoxicity was detected, the hydrophobic myristoyl rest was shown to cause haemolysis. Taken together, these data show that a structural optimization of L-R5 may be possible, both from a toxicological and an efficacy point of view.

Evaluation in pig of an intestinal administration device for oral peptide delivery

The bioavailability of peptides co-delivered with permeation enhancers following oral administration remains low and highly variable. Two factors that may contribute to this are the dilution of the permeation enhancer in the intestinal fluid, as well as spreading of the released permeation enhancer and peptide in the lumen by intestinal motility. In this work we evaluated an Intestinal Administration Device (IAD) designed to reduce the luminal dilution of drug and permeation enhancer, and to minimize movement of the dosage form in the intestinal lumen. To achieve this, the IAD utilizes an expanding design that holds immediate release mini tablets and places these in contact with the intestinal epithelium, where unidirectional drug release can occur. The expanding conformation limits movement of the IAD in the intestinal tract, thereby enabling drug release at a single focal point in the intestine. A pig model was selected to study the ability of the IAD to promote intestinal absorption of the peptide MEDI7219 formulated together with the permeation enhancer sodium caprate. We compared the IAD to intestinally administered enteric coated capsules and an intestinally administered solution. The IAD restricted movement of the immediate release tablets in the small intestine and histological evaluation of the mucosa indicated that high concentrations of sodium caprate were achieved. Despite significant effect of the permeation enhancer on the integrity of the intestinal epithelium, the bioavailability of MEDI7219 was of the same order of magnitude as that achieved with the solution and enteric coated capsule formulations (2.5-3.8%). The variability in plasma concentrations of MEDI7219 were however lower when delivered using the IAD as compared to the solution and enteric coated capsule formulations. This suggests that dosage forms that can limit intestinal dilution and control the position of drug release can be a way to reduce the absorptive variability of peptides delivered with permeation enhancers but do not offer significant benefits in terms of increasing bioavailability.

Long-term daily oral administration of intestinal permeation enhancers is safe and effective in mice

Although protein drugs are powerful biologic therapeutics, they cannot be delivered orally because their large size and hydrophilicity limit their absorption across the intestinal epithelium. One potential solution is the incorporation of permeation enhancers into oral protein formulations; however, few have advanced clinically due to toxicity concerns surrounding chronic use. To better understand these concerns, we conducted a 30-day longitudinal study of daily oral permeation enhancer use in mice and resultant effects on intestinal health. Specifically, we investigated three permeation enhancers: sodium caprate (C10), an industry standard, as well as 1-phenylpiperazine (PPZ) and sodium deoxycholate (SDC). Over 30 days of treatment, all mice gained weight, and none required removal from the study due to poor health. Furthermore, intestinal permeability did not increase following chronic use. We also quantified the gene expression of four tight junction proteins (claudin 2, claudin 3, ZO-1, and JAM-A). Significant differences in gene expression between untreated and permeation enhancer-treated mice were found, but these varied between treatment groups, with most differences resolving after a 1-week washout period. Immunofluorescence microscopy revealed no observable differences in protein localization or villus architecture between treated and untreated mice. Overall, PPZ and SDC performed comparably to C10, one of the most clinically advanced enhancers, and results suggest that the chronic use of some permeation enhancers may be therapeutically viable from a safety standpoint.

Gastrointestinal Permeation Enhancers for the Development of Oral Peptide Pharmaceuticals

Recently, two oral-administered peptide pharmaceuticals, semaglutide and octreotide, have been developed and are considered as a breakthrough in peptide and protein drug delivery system development. In 2019, the Food and Drug Administration (FDA) approved an oral dosage form of semaglutide developed by Novo Nordisk (Rybelsus^®) for the treatment of type 2 diabetes. Subsequently, the octreotide capsule (Mycapssa^®), developed through Chiasma's Transient Permeation Enhancer (TPE) technology, also received FDA approval in 2020 for the treatment of acromegaly. These two oral peptide products have been a significant success; however, a major obstacle to their oral delivery remains the poor permeability of peptides through the intestinal epithelium. Therefore, gastrointestinal permeation enhancers are of great relevance for the development of subsequent oral peptide products. Sodium salcaprozate (SNAC) and sodium caprylate (C8) have been used as gastrointestinal permeation enhancers for semaglutide and octreotide, respectively. Herein, we briefly review two approved products, Rybelsus^® and Mycapssa^®, and discuss the permeation properties of SNAC and medium chain fatty acids, sodium caprate (C10) and C8, focusing on Eligen technology using SNAC, TPE technology using C8, and gastrointestinal permeation enhancement technology (GIPET) using C10.

Intestinal absorption pathways of lisinopril: Mechanistic investigations

Lisinopril is an antihypertensive drug with poor intestinal permeability. Enhancement of intestinal absorption depends on a clear understanding of the permeation pathways and absorption mechanisms. Unfortunately, these are not fully elucidated for lisinopril. Accordingly, the aim was to determine lisinopril permeation pathways and obstacles limiting membrane transport with subsequent nomination of appropriate permeation enhancers. This employed an in situ rabbit intestinal perfusion technique, which revealed site-dependent absorptive clearance (PeA/L) from a lisinopril simple solution (5 μg/ml), with paracellular absorption playing a role. Regional drug permeability ranked as colon> duodenum> jejunum> ileum opposing intestinal expression rank of P-glycoprotein (P-gp) efflux transporters. Duodenal and jejunal perfusion of a higher lisinopril concentration (50 μg/ml) reflected saturable absorption, suggesting carrier-mediated transport. The effect of piperine and verapamil as P-gp inhibitors on intestinal absorption of lisinopril was investigated. Coperfusion with either piperine or verapamil significantly enhanced lisinopril absorption, with enhancement being dominant in the ileum segment. This supported the contribution of P-gp transporters to poor lisinopril permeability. On the other hand, coperfusion of lisinopril with zinc acetate dihydrate significantly multiplied lisinopril PeA/L by 2.3- and 6.6-fold in duodenum and ileum segments, respectively, through magnifying intestinal water flux. The study explored the barriers limiting lisinopril intestinal absorption. Moreover, the study exposed clinically relevant lisinopril interactions with common coadministered cargos that should be considered for an appropriate lisinopril regimen. However, this requires further in vivo verification.

Nutraceutical Approaches to Dyslipidaemia: The Main Formulative Issues Preventing Efficacy

Currently, the nutraceutical approach to treat dyslipidaemia is increasing in use, and in many cases is used by physicians as the first choice in the treatment of patients with borderline values. Nutraceuticals represent an excellent opportunity to treat the preliminary conditions not yet showing the pathological signs of dyslipidaemia. Their general safety, the patient's confidence, the convincing proof of efficacy and the reasonable costs prompted the market of new preparations. Despite this premise, many nutraceutical products are poorly formulated and do not meet the minimum requirements to ensure efficacy in normalizing blood lipid profiles, promoting cardiovascular protection, and normalizing disorders of glycemic metabolism. In this context, bioaccessibility and bioavailability of the active compounds is a crucial issue. Little attention is paid to the proper formulations needed to improve the overall bioavailability of the active molecules. According to these data, many products prove to be insufficient to ensure full enteric absorption. The present review analysed the literature in the field of nutraceuticals for the treatment of dyslipidemia, focusing on resveratrol, red yeast rice, berberine, and plant sterols, which are among the nutraceuticals with the greatest formulation problems, highlighting bioavailability and the most suitable formulations.

Pharmacokinetic of berberine, the main constituent of Berberis vulgaris L.: A comprehensive review

Barberry (Berberis vulgaris L.) is a medicinal plant and its main constituent is an isoquinoline alkaloid named berberine that has multiple pharmacological effects such as antioxidant, anti-microbial, antiinflammatory, anticancer, anti-diabetes, anti-dyslipidemia, and anti-obesity. However, it has restricted clinical uses due to its very poor solubility and bioavailability (less than 1%). It undergoes demethylenation, reduction, and cleavage of the dioxymethylene group in the first phase of metabolism. Its phase two reactions include glucuronidation, sulfation, and methylation. The liver is the main site for berberine distribution. Berberine could excrete in feces, urine, and bile. Fecal excretion of berberine (11-23%) is higher than urinary and biliary excretion routes. However, a major berberine metabolite is excreted in urine greater than in feces. Concomitant administration of berberine with other drugs such as metformin, cyclosporine A, digoxin, etc. may result in important interactions. Thus, in this review, we gathered and dissected any related animal and human research articles regarding the pharmacokinetic parameters of berberine including bioavailability, metabolism, distribution, excretion, and drug-drug interactions. Also, we discussed and gathered various animal and human studies regarding the developed products of berberine with better bioavailability and consequently, better therapeutic effects.

Identification of a Multi-Component Formulation for Intestinal Delivery of a GLP-1/Glucagon Co-agonist Peptide

PURPOSE

Oral delivery of therapeutic peptides has been challenging due to multiple physiological factors and physicochemical properties of peptides. We report a systematic approach to identify formulation compositions combining a permeation enhancer and a peptidase inhibitor that minimize proteolytic degradation and increase absorption of a peptide across the small intestine.

METHODS

An acylated glucagon-like peptide-1/glucagon co-agonist peptide (4.5 kDa) was selected as a model peptide. Proteolytic stability of the peptide was investigated in rat and pig SIF. Effective PEs and multiple component formulations were identified in rats. Relative bioavailability of the peptide was determined in minipigs via intraduodenal administration (ID) of enteric capsules.

RESULTS

The peptide degraded rapidly in the rat and pig SIF. Citric acid, SBTI, and SBTCI inhibited the enzymatic degradation. The peptide self-associated into trimers in solution, however, addition of PEs monomerized the peptide. C10 was the most effective PE among tested PEs (DPC, LC, rhamnolipid, C12-maltosides, and SNAC) to improve intestinal absorption of the peptide in the rat IJ-closed loop model. A combination of C10 and SBTI or SBTCI increased the peptide exposure 5-tenfold compared to the exposure with the PE alone in the rat IJ-cannulated model, and achieved 1.06 ± 0.76% bioavailability in minipigs relative to subcutaneous via ID administration using enteric capsules.

CONCLUSION

We identified SBTI and C10 as an effective peptidase inhibitor and PE for intestinal absorption of the peptide. The combination of SBTI and C10 addressed the peptide physiochemical properties and provides a formulation strategy to achieve intestinal delivery of this peptide.

Characterization of the physicochemical interactions between exenatide and two intestinal permeation enhancers: sodium caprate (C10) and salcaprozate sodium (SNAC)

A common approach to tackle the poor intestinal membrane permeability of peptides after oral administration is to formulate them with a permeation enhancer (PE). Increased oral bioavailability for oral peptide candidates has been reported from clinical trials when either salcaprozate sodium (SNAC) or sodium caprate (C₁₀) is incorporated in the formulation. However, little is known about how they physically interact with peptides in solution. Our objective was to compare the biophysical interactions between the GLP-1 analogue exenatide (Byetta®, Lilly), and C₁₀ or SNAC using a variety of advanced analytical techniques. First, critical micelle concentration was measured in different buffers for both PEs. Dynamic light scattering (DLS) measurements revealed specific supramolecular structures arising from exenatide-PE association. Surface plasmon resonance (SPR) indicated the formation of exenatide-PE complexes with a high contribution from non-specific interactions and rapid binding kinetics, resulting in overall low affinities. DLS and isothermal titration calorimetry (ITC) were used to examine the supramolecular organization of the PEs, and revealed thermodynamic signatures characterized by unfavourable enthalpic contributions compensated by favourable entropic ones, but with low-affinity estimates in water (K_D in the 10-100 µM range). With affinity capillary electrophoresis (ACE), weak interactions between exenatide and SNAC or C₁₀ were confirmed in saline, with a dissociation constant around 10 µM and 30 µM respectively. In biorelevant intestinal media, the bile salts in FaSSIF and FeSSIF further reduced the binding of both agents to exenatide (K_D ≈ 100 µM), indicating that the interaction between the PEs and exenatide might be inhibited by bile salts in the GI lumen. This study suggests that the interactions of both PEs with exenatide follow a similar non-covalent mechanism and are of low affinity.

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.

Transepithelial delivery of insulin conjugated with phospholipid-mimicking polymers via biomembrane fusion-mediated transcellular pathways

Epithelial barriers that seal cell gaps by forming tight junctions to prevent the free permeation of nutrients, electrolytes, and drugs, are essential for maintaining homeostasis in multicellular organisms. The development of nanocarriers that can permeate epithelial tissues without compromising barrier function is key for establishing a safe and efficient drug delivery system (DDS). Previously, we have demonstrated that a water-soluble phospholipid-mimicking random copolymer, poly(2-methacryloyloxyethyl phosphorylcholine₃₀-random-n‑butyl methacrylate₇₀) (PMB30W), enters the cytoplasm of live cells by passive diffusion manners, without damaging the cell membranes. The internalization mechanism was confirmed to be amphiphilicity-induced membrane fusion. In the present study, we demonstrated energy-independent permeation of PMB30W through the model epithelial barriers of Madin-Darby canine kidney (MDCK) cell monolayers in vitro. The polymer penetrated epithelial MDCK monolayers via transcellular pathways without breaching the barrier functions. This was confirmed by our unique assay that can monitor the leakage of the proton as the smallest indicator across the epithelial barriers. Moreover, energy-independent transepithelial permeation was achieved when insulin was chemically conjugated with the phospholipid-mimicking nanocarrier. The bioactivity of insulin as a growth factor was found to be maintained even after translocation. These fundamental findings may aid the establishment of transepithelial DDS with advanced drug efficiency and safety. STATEMENT OF SIGNIFICANCE: A nanocarrier that can freely permeate epithelial tissues without compromising barrier function is key for successful DDS. Existing strategies mainly rely on paracellular transport associated with tight junction breakdown or transcellular transport via transporter recognition-mediated active uptake. These approaches raise concerns about efficiency and safety. In this study, we performed non-endocytic permeation of phospholipid-mimicking polymers through the model epithelial barriers in vitro. The polymer penetrated via transcytotic pathways without breaching the barriers of biomembrane and tight junction. Moreover, transepithelial permeation occurred when insulin was covalently attached to the nanocarrier. The bioactivity of insulin was maintained even after translocation. The biomimetic design of nanocarrier may realize safe and efficient transepithelial DDS.

Oral delivery of therapeutic peptides and proteins: Technology landscape of lipid-based nanocarriers

The oral administration of therapeutic peptides and proteins is favoured from a patient and commercial point of view. In order to reach the systemic circulation after oral administration, these drugs have to overcome numerous barriers including the enzymatic, sulfhydryl, mucus and epithelial barrier. The development of oral formulations for therapeutic peptides and proteins is therefore necessary. Among the most promising formulation approaches are lipid-based nanocarriers such as oil-in-water nanoemulsions, self-emulsifying drug delivery systems (SEDDS), solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC), liposomes and micelles. As the lipophilic character of therapeutic peptides and proteins can be tremendously increased such as by the formation of hydrophobic ion pairs (HIP) with hydrophobic counter ions, they can be incorporated in the lipophilic phase of these carriers. Since gastrointestinal (GI) peptidases as well as sulfhydryl compounds such as glutathione and dietary proteins are too hydrophilic to enter the lipophilic phase of these carriers, the incorporated therapeutic peptide or protein is protected towards enzymatic degradation as well as unintended thiol/disulfide exchange reactions. Stability of lipid-based nanocarriers towards lipases can be provided by the use to excipients that are not or just poorly degraded by these enzymes. Nanocarriers with a size <200 nm and a mucoinert surface such as PEG or zwitterionic surfaces exhibit high mucus permeating properties. Having reached the underlying absorption membrane, lipid-based nanocarriers enable paracellular and lymphatic drug uptake, induce endocytosis and transcytosis or simply fuse with the cell membrane releasing their payload into the systemic circulation. Numerous in vivo studies provide evidence for the potential of these delivery systems. Within this review we provide an overview about the different barriers for oral peptide and protein delivery, highlight the progress made on lipid-based nanocarriers in order to overcome them and discuss strengths and weaknesses of these delivery systems in comparison to other technologies.

A Practical Strategy for Exploring the Pharmacological Mechanism of Luteolin Against COVID-19/Asthma Comorbidity: Findings of System Pharmacology and Bioinformatics Analysis

Asthma patients may increase their susceptibility to SARS-CoV-2 infection and the poor prognosis of coronavirus disease 2019 (COVID-19). However, anti-COVID-19/asthma comorbidity approaches are restricted on condition. Existing evidence indicates that luteolin has antiviral, anti-inflammatory, and immune regulation capabilities. We aimed to evaluate the possibility of luteolin evolving into an ideal drug and explore the underlying molecular mechanisms of luteolin against COVID-19/asthma comorbidity. We used system pharmacology and bioinformatics analysis to assess the physicochemical properties and biological activities of luteolin and further analyze the binding activities, targets, biological functions, and mechanisms of luteolin against COVID-19/asthma comorbidity. We found that luteolin may exert ideal physicochemical properties and bioactivity, and molecular docking analysis confirmed that luteolin performed effective binding activities in COVID-19/asthma comorbidity. Furthermore, a protein–protein interaction network of 538 common targets between drug and disease was constructed and 264 hub targets were obtained. Then, the top 6 hub targets of luteolin against COVID-19/asthma comorbidity were identified, namely, TP53, AKT1, ALB, IL-6, TNF, and VEGFA. Furthermore, the enrichment analysis suggested that luteolin may exert effects on virus defense, regulation of inflammation, cell growth and cell replication, and immune responses, reducing oxidative stress and regulating blood circulation through the Toll-like receptor; MAPK, TNF, AGE/RAGE, EGFR, ErbB, HIF-1, and PI3K–AKT signaling pathways; PD-L1 expression; and PD-1 checkpoint pathway in cancer. The possible “dangerous liaison” between COVID-19 and asthma is still a potential threat to world health. This research is the first to explore whether luteolin could evolve into a drug candidate for COVID-19/asthma comorbidity. This study indicated that luteolin with superior drug likeness and bioactivity has great potential to be used for treating COVID-19/asthma comorbidity, but the predicted results still need to be rigorously verified by experiments.

Impact of Intestinal Concentration and Colloidal Structure on the Permeation-Enhancing Efficiency of Sodium Caprate in the Rat

In this work, we set out to better understand how the permeation enhancer sodium caprate (C10) influences the intestinal absorption of macromolecules. FITC-dextran 4000 (FD4) was selected as a model compound and formulated with 50–300 mM C10. Absorption was studied after bolus instillation of liquid formulation to the duodenum of anesthetized rats and intravenously as a reference, whereafter plasma samples were taken and analyzed for FD4 content. It was found that the AUC and C_max of FD4 increased with increasing C10 concentration. Higher C10 concentrations were associated with an increased and extended absorption but also increased epithelial damage. Depending on the C10 concentration, the intestinal epithelium showed significant recovery already at 60–120 min after administration. At the highest studied C10 concentrations (100 and 300 mM), the absorption of FD4 was not affected by the colloidal structures of C10, with similar absorption obtained when C10 was administered as micelles (pH 8.5) and as vesicles (pH 6.5). In contrast, the FD4 absorption was lower when C10 was administered at 50 mM formulated as micelles as compared to vesicles. Intestinal dilution of C10 and FD4 revealed a trend of decreasing FD4 absorption with increasing intestinal dilution. However, the effect was smaller than that of altering the total administered C10 dose. Absorption was similar when the formulations were prepared in simulated intestinal fluids containing mixed micelles of bile salts and phospholipids and in simple buffer solution. The findings in this study suggest that in order to optimally enhance the absorption of macromolecules, high (≥100 mM) initial intestinal C10 concentrations are likely needed and that both the concentration and total dose of C10 are important parameters.

In Silico-Based Experiments on Mechanistic Interactions between Several Intestinal Permeation Enhancers with a Lipid Bilayer Model

Oral administration of drugs is generally considered convenient and patient-friendly. However, oral administration of biological drugs exhibits low oral bioavailability (BA) due to enzymatic degradation and low intestinal absorption. A possible approach to circumvent the low BA of oral peptide drugs is to coformulate the drugs with permeation enhancers (PEs). PEs have been studied since the 1960s and are molecules that enhance the absorption of hydrophilic molecules with low permeability over the gastrointestinal epithelium. In this study, we investigated the impact of six PEs on the structural properties of a model membrane using molecular dynamics (MD) simulations. The PEs included were the sodium salts of the medium chain fatty acids laurate, caprate, and caprylate and the caprylate derivative SNAC─all with a negative charge─and neutral caprate and neutral sucrose monolaurate. Our results indicated that the PEs, once incorporated into the membrane, could induce membrane leakiness in a concentration-dependent manner. Our simulations suggest that a PE concentration of at least 70-100 mM is needed to strongly affect transcellular permeability. The increased aggregation propensity seen for neutral PEs might provide a molecular-level mechanism for the membrane disruptions seen at higher concentrations in vivo. The ability for neutral PEs to flip-flop across the lipid bilayer is also suggestive of possible intracellular modes of action other than increasing membrane fluidity. Taken together, our results indicate that MD simulations are useful for gaining insights relevant to the design of oral dosage forms based around permeability enhancer molecules.

Influence of release rate, dose and co-administration on pharmacokinetics, pharmacodynamics and PK-PD relationship of tanshinone IIA and tanshinol

The present study aims to investigate the influence of release rate, dose and co-administration on pharmacokinetics (PK) and pharmacodynamics (PD) of tanshinone IIA (TA) and tanshinol (TS), and reveal the changes in their PK-PD relationships. Sustained and immediate release pellets of TS and TA were prepared respectively, and oral administrated to angina model rabbits according to the experimental design. The administration dose of TS was 50, 35 or 20 mg/kg and that of TA was 30 mg/kg. Then, plasma concentrations of TS and TA were measured to evaluate the pharmacokinetics. Pharmacodynamic biomarkers including cardiac troponin (cTn-I), creatine kinase (CK-MB), superoxide dismutase (SOD) and nitric oxide (NO) were measured to evaluated the effects of cardioprotection, amelioration of oxidative stress and vasorelaxation of TS and TA. Parameters such as maximum plasma concentration (C_max), maximum effect (E_max), time to C_max or E_max (TC_max or TE_max), areas under the plasma concentration or effect curves (AUC_0-∞ or AUEC) and pharmacodynamic efficiency (EFF) were calculated based on non-compartmental analysis. Beside, PK-PD relationship/hysteresis was evaluated. The TE_max was less sensitive than TC_max to changes in release rate. The E_max, AUEC and EFF showed increasing trend as the decrease of release rate even that the AUC_0-∞ showed no significant difference. In addition, slow drug release decreased the magnitude of hysteresis of TS and TA. The sensitivities of E_max and AUEC of four biomarkers to changes in dose were varied and relatively lower than those of C_max and AUC_0-∞. The EFF decreased and the magnitude of hysteresis increased for high dose. The C_max and AUC_0-∞ of TS and TA showed little difference after co-administration. The E_max and AUEC of four biomarkers increased for immediate release pellets (P < 0.05 or P < 0.01) and generally decreased for sustained release pellets (P < 0.05 or P < 0.01) after co-administration. In addition, the magnitudes of hysteresis of four biomarkers decreased for immediate release pellets and generally increased for sustained release pellets after co-administration. In summary, the dissociated and unstable PK-PD relationship should be considered during optimization of dosage forms and regimens to make sure the rationality, safety and efficacy. These findings could also provide some valuable information for the development and clinical therapy of other drugs.

Cell-Penetrating Peptides as Carriers for Transepithelial Drug Delivery

This chapter describes the use of cell-penetrating peptides (CPPs) as carriers for transepithelial delivery of therapeutic peptides. Assessment of transepithelial peptide permeation and the mechanisms of action that permeability enhancing drug carriers exert on the epithelium requires subtle sample preparation and analysis by orthogonal methods. Here, the preparation and use of CPP-insulin physical mixture samples including the quantification of insulin by enzyme-linked immunosorbent assay (ELISA) is described. In addition, effects of CPPs on the epithelium and its barrier properties immediately upon exposure and after a recovery period are evaluated by epithelial cell viability, transepithelial electrical resistance, immunostaining of the tight junction associated zonula occludens (ZO-1) protein, and actin cytoskeleton staining.

Oral drug delivery for immunoengineering

The systemic pharmacotherapeutic efficacy of immunomodulatory drugs is heavily influenced by its route of administration. A few common routes for the systemic delivery of immunotherapeutics are intravenous, intraperitoneal, and intramuscular injections. However, the development of novel biomaterials, in adjunct to current progress in immunoengineering, is providing an exciting area of interest for oral drug delivery for systemic targeting. Oral immunotherapeutic delivery is a highly preferred route of administration due to its ease of administration, higher patient compliance, and increased ability to generate specialized immune responses. However, the harsh environment and slow systemic absorption, due to various biological barriers, reduces the immunotherapeutic bioavailability, and in turn prevents widespread use of oral delivery. Nonetheless, cutting edge biomaterials are being synthesized to combat these biological barriers within the gastrointestinal (GI) tract for the enhancement of drug bioavailability and targeting the immune system. For example, advancements in biomaterials and synthesized drug agents have provided distinctive methods to promote localized drug absorption for the modulation of local or systemic immune responses. Additionally, novel breakthroughs in the immunoengineering field show promise in the development of vaccine delivery systems for disease prevention as well as combating autoimmune diseases, inflammatory diseases, and cancer. This review will discuss current progress made within the field of biomaterials and drug delivery systems to enhance oral immunotherapeutic availability, and how these new delivery platforms can be utilized to deliver immunotherapeutics for resolution of immune-related diseases.

Explicit-pH Coarse-Grained Molecular Dynamics Simulations Enable Insights into Restructuring of Intestinal Colloidal Aggregates with Permeation Enhancers

Permeation enhancers (PEs) can increase the bioavailability of drugs. The mechanisms of action of these PEs are complex, but, typically, when used for oral administration, they can transiently induce the alteration of trans- and paracellular pathways, including increased solubilization and membrane fluidity, or the opening of the tight junctions. To elucidate these mechanistic details, it is important to understand the aggregation behavior of not only the PEs themselves but also other molecules already present in the intestine. Aggregation processes depend critically on, among other factors, the charge state of ionizable chemical groups, which is affected by the pH of the system. In this study, we used explicit-pH coarse-grained molecular dynamics simulations to investigate the aggregation behavior and pH dependence of two commonly used PEs—caprate and SNAC—together with other components of fasted- and fed-state simulated intestinal fluids. We also present and validate a coarse-grained molecular topology for the bile salt taurocholate suitable for the Martini3 force-field. Our results indicate an increase in the number of free molecules as a function of the system pH and for each combination of FaSSIF/FeSSIF and PEs. In addition, there are differences between caprate and SNAC, which are rationalized based on their different molecular structures and critical micelle concentrations.

Intestinal permeation enhancers enable oral delivery of macromolecules up to 70 kDa in size

The decades-long effort to deliver peptide drugs orally has resulted in several clinically successful formulations. These formulations are enabled by the inclusion of permeation enhancers that facilitate the intestinal absorption of peptides. Thus far, these oral peptide drugs have been limited to peptides less than 5 kDa, and it is unclear whether there is an upper bound of protein size that can be delivered with permeation enhancers. In this work, we examined two permeation enhancers, 1-phenylpiperazine (PPZ) and sodium deoxycholate (SDC), for their ability to increase intestinal transport of a model macromolecule (FITC-Dextran) as a function of its size. Specifically, the permeability of dextrans with molecular weights of 4, 10, 40, and 70 kDa was assessed in an in vitro and in vivo model of the intestine. In Caco-2 monolayers, both PPZ and SDC significantly increased the permeability of only FD4 and FD10. However, in mice, PPZ and SDC behaved differently. While SDC improved the absorption of all tested sizes of dextrans, PPZ was effective only for FD4 and FD10. This work is the first report of PPZ as a permeation enhancer in vivo, and it highlights the ability of permeation enhancers to improve the absorption of macromolecules across a broad range of sizes relevant for protein drugs.

Modulating the Blood-Brain Barrier: A Comprehensive Review

The highly secure blood-brain barrier (BBB) restricts drug access to the brain, limiting the molecular toolkit for treating central nervous system (CNS) diseases to small, lipophilic drugs. Development of a safe and effective BBB modulator would revolutionise the treatment of CNS diseases and future drug development in the area. Naturally, the field has garnered a great deal of attention, leading to a vast and diverse range of BBB modulators. In this review, we summarise and compare the various classes of BBB modulators developed over the last five decades-their recent advancements, advantages and disadvantages, while providing some insight into their future as BBB modulators.

Future Perspectives of Oral Delivery of Next Generation Therapies for Treatment of Skin Diseases

Gene therapies have conspicuously bloomed in recent years as evidenced by the increasing number of cell-, gene-, and oligo-based approved therapies. These therapies hold great promise for dermatological disorders with high unmet need, for example, epidermolysis bullosa or pachyonychia congenita. Furthermore, the recent clinical success of clustered regularly interspaced short palindromic repeats (CRISPR) for genome editing in humans will undoubtedly contribute to defining a new wave of therapies. Like biologics, naked nucleic acids are denatured inside the gastrointestinal tract and need to be administered via injections. For a treatment to be effective, a sufficient amount of a given regimen needs to reach systemic circulation. Multiple companies are racing to develop novel oral drug delivery approaches to circumvent the proteolytic and acidic milieu of the gastrointestinal tract. In this review, we provide an overview of the evolution of the gene therapy landscape, with a deep focus on gene and oligonucleotide therapies in clinical trials aimed at treating skin diseases. We then examine the progress made in drug delivery, with particular attention on the peptide field and drug-device combinations that deliver macromolecules into the gastrointestinal tract. Such novel devices could potentially be applied to administer other therapeutics including genes and CRISPR-based systems.

Formulation strategies to improve the efficacy of intestinal permeation enhancers. Adv Drug Deliv Rev 2021;177:113925. [PMID: 34418495 DOI: 10.1016/j.addr.2021.113925]

The use of chemical permeation enhancers (PEs) is the most widely tested approach to improve oral absorption of low permeability active agents, as represented by peptides. Several hundred PEs increase intestinal permeability in preclinical bioassays, yet few have progressed to clinical testing and, of those, only incremental increases in oral bioavailability (BA) have been observed. Still, average BA values of ~1% were sufficient for two recent FDA approvals of semaglutide and octreotide oral formulations. PEs are typically screened in static in vitro and ex-vivo models where co-presentation of active agent and PE in high concentrations allows the PE to alter barrier integrity with sufficient contact time to promote flux across the intestinal epithelium. The capacity to maintain high concentrations of co-presented agents at the epithelium is not reached by standard oral dosage forms in the upper GI tract in vivo due to dilution, interference from luminal components, fast intestinal transit, and possible absorption of the PE per se. The PE-based formulations that have been assessed in clinical trials in either immediate-release or enteric-coated solid dosage forms produce low and variable oral BA due to these uncontrollable physiological factors. For PEs to appreciably increase intestinal permeability from oral dosage forms in vivo, strategies must facilitate co-presentation of PE and active agent at the epithelium for a sustained period at the required concentrations. Focusing on peptides as examples of a macromolecule class, we review physiological impediments to optimal luminal presentation, discuss the efficacy of current PE-based oral dosage forms, and suggest strategies that might be used to improve them.

Soybean oil and coconut oil enhance the absorption of chlorogenic acid in humans

The effect of a mainly polyunsaturated oil (soybean oil) and a mainly medium chain triglyceride oil (coconut oil) on the absorption of the phenolic antioxidant chlorogenic acid (5-caffeoylquinic acid) was investigated using 90 healthy volunteers. Serum concentrations and the absorbed percentages of chlorogenic acid of volunteers who received chlorogenic acid without oils (0.006 ± 0.001 mg/ml, 5.7 ± 0.2%), chlorogenic acid with soybean oil (0.012 ± 0.001 mg/ml, 11.8 ± 1.3%), and chlorogenic acid with coconut oil (0.067 ± 0.014 mg/ml, 65.6 ± 18.1%) were significantly different from each other (p < .05). There was a strong positive correlation between the increase in serum and plasma antioxidant capacity and the absorption of chlorogenic acid. The major fatty acid of each of soybean oil and coconut oil also improved the permeability of chlorogenic acid in Caco-2 cell monolayers. The results suggest that the tested edible oils may improve the nutritional value of chlorogenic acid-containing foods by improving the absorption of chlorogenic acid. PRACTICAL APPLICATIONS: Small polar antioxidants such as phenolic acids and flavonoids are poorly absorbed through the intestinal epithelium. Chlorogenic acid was used in the present study as a model for small polar phenolic antioxidants. According to the present study, soybean oil with mainly polyunsaturated fatty acids and coconut oil with mainly medium chain fatty acids improve the absorption of these antioxidants. These findings suggest that proper planning of diets or food supplements containing phenolic antioxidants with medium chain or polyunsaturated fatty acid-rich edible oils may enhance the nutritional benefits expected from phenolic antioxidants.

Target specific tight junction modulators

Intercellular tight junctions represent a formidable barrier against paracellular drug absorption at epithelia (e.g., nasal, intestinal) and the endothelium (e.g., blood-brain barrier). In order to enhance paracellular transport of drugs and increase their bioavailability and organ deposition, active excipients modulating tight junctions have been applied. First-generation of permeation enhancers (PEs) acted by unspecific interactions, while recently developed PEs address specific physiological mechanisms. Such target specific tight junction modulators (TJMs) have the advantage of a defined specific mechanism of action. To date, merely a few of these novel active excipients has entered into clinical trials, as their lack in safety and efficiency in vivo often impedes their commercialisation. A stronger focus on the development of such active excipients would result in an economic and therapeutic improvement of current and future drugs.

DSPE-PEG polymers for improving pulmonary absorption of poorly absorbed macromolecules in rats and relative mechanism

OBJECTIVE

This study aims to investigate the potential of DSPE-PEG polymers (DSPE-PEG-OH and DSPE-PEG-SH) on improving absorption of poorly absorbable macromolecules via intrapulmonary administration and underlying mechanism.

METHODS

In situ pulmonary absorption experiments were performed to investigate the absorption of model compounds after intrapulmonary administration to rats. The local membrane damage induced by these DSPE-PEG polymers were evaluated based on morphological observation of lung tissues and measurement of biological toxic markers in bronchoalveolar lavage fluid (BALF) postintrapulmonary delivery of DSPE-PEG polymers to rats. The underlying enhancement mechanism of these polymers was explored by investigating their effects on the pulmonary membrane fluidity and gene expression of tight junction associated proteins with fluorescence polarization and western blotting, respectively.

RESULTS

Intrapulmonary delivery of these DSPE-PEG polymers significantly enhanced absorptions of poorly absorbed model drugs and did not induce serious damage to the pulmonary membranes of rats. Mechanistic studies demonstrated unaffected pulmonary membrane fluidity and up-regulated expression levels of tight junction-associated proteins by DSPE-PEG polymers, thus indicating that paracellular pathways might be included in the underlying mechanisms by which DSPE-PEG polymers exerted their enhancing actions on drug absorption.

CONCLUSIONS

These findings suggested that these DSPE-PEG polymers are potential for promoting absorptions of poorly absorbable macromolecules with no evidence of damage to the local pulmonary membranes of rats.Novelty statementIn this study, DSPE-PEG-OH and DSPE-PEG-SH polymers, two DSPE-PEG2000 conjugates with different terminal groups demonstrated significant promoting effects on the absorption of poorly absorbed macromolecular drugs after intrapulmonary delivery to rats, and did not induce serious damage to the pulmonary membranes of rats. These DSPE-PEG polymers could statistically downregulate expression levels of tight junction-associated proteins (ZO-1 and occludin), indicating the underlying mechanism by which these polymers exerted their absorption enhancing actions through pulmonary epithelial paracellular pathways. Thus, this study exhibited prospective potential of these DSPE-PEG polymers in developing into dosage forms with the aim to improve the poor bioavailability of some poorly absorbed macromolecular drugs.

Development of technetium-99m labeled ultrafine gold nanobioconjugates for targeted imaging of folate receptor positive cancers

INTRODUCTION

Strategic design and synthesis of nanoparticle based preparations could improve diagnostic screening of several cancer types, thereby facilitating better clinical management of the disease. Towards this, the present work aims to develop and evaluate a radioactive technetium-99m (99mTc) labeled gold nanoparticle (NP) preparation modified with folic acid, so as to diagnose folate receptor positive cancers viz. ovarian, breast, etc. METHODS: 11-Bromoundecanoic acid (UA) was synthetically modified both with folic acid and Hydrazinonicotinic acid (HYNIC) chelate at the carboxylic acid end and subsequently converted to thiol functionality at the bromo terminal to yield folic acid-UA-SH and HYNIC-UA-SH ligands respectively. Gold NPs modified with folic acid and HYNIC chelator were obtained on direct addition of folic acid-UA-SH and HYNIC-UA-SH to chloroauric acid in polysorbate 80 solution under reducing conditions. These NPs were then radiolabeled with 99mTc following HYNIC labeling approach. Both the inactive and 99mTc-labeled gold NPs were then tested for their biological efficacy in folate receptor (FR) positive KB cancer cell lines. Also, biodistribution studies of 99mTc-labeled gold NPs were carried in KB tumor xenografts to ascertain the efficacy towards FR in in vivo system.

RESULTS

Polysorbate 80 could stabilize the gold NP preparation with average size <10 nm as determined by TEM. Inhibition of [3H]folic acid with functionalized gold nanoparticle revealed affinity towards FR positive KB cell lines with an IC50 ~ 9 μM. Biodistribution studies of 99mTc-labeled gold NP preparation in SCID mice bearing KB tumor showed an uptake of 1.39 ± 0.18%ID/g in tumor and 5.48 ± 0.72%ID/g in kidneys at 3 h post-injection. In vivo distribution in folic acid pre-treated animals could not establish the specificity towards folate receptors.

CONCLUSIONS

Biological evaluation of functionalized gold NP showed affinity towards FR positive cancer cell lines. 99mTc-labeled NP exhibited target uptake in both in vitro and in vivo models, but folic acid inhibition could not establish the target specificity. Nevertheless, in vivo pharmacokinetics envisaged in the present design was achieved using the present gold functionalized NP preparation.

Enhancing Intestinal Absorption of a Model Macromolecule via the Paracellular Pathway using E-Cadherin Peptides

Membrane permeation enhancers have received significant attention in recent years for enabling the oral absorption of poorly permeable drug molecules. In this study, we investigated the ability of His-Ala-Val (HAV) and Ala-Asp-Thr (ADT) peptides derived from the extracellular-1 (EC1) domain of E-cadherin proteins to increase the paracellular permeation and intestinal bioavailability of the poorly permeable model macromolecule, fluorescein-isothiocyanate dextran with average molecular weight 4000 (FD4). The in vitro enzymatic stability of linear and cyclic E-cadherin peptides was characterized under simulated gastric and intestinal conditions, and the cyclic E-cadherin peptides, HAVN1 and ADTC5, which demonstrated excellent stability in vitro, were advanced to in vivo intestinal instillation studies and compared against the established surfactant membrane permeation enhancer, sodium caprate (C₁₀). Cyclic HAVN1 and ADTC5 peptides increased FD4 bioavailability by 7.2- and 4.4-fold compared to control, respectively (not statistically significant). In contrast, C₁₀ provided a statistically significant 10.7-fold relative bioavailability enhancement for FD4. Importantly, this study represents the first report of cyclic E-cadherin peptides as intestinal membrane permeation enhancers. The findings described herein demonstrate the potential of enzymatically stabilized cyclic E-cadherin peptides for increasing poorly permeable drug absorption via the oral route.