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

Macrocycles and macrocyclization in anticancer drug discovery: Important pieces of the puzzle

Increasing disease-related proteins have been identified as novel therapeutic targets. Macrocycles are emerging as potential solutions, bridging the gap between conventional small molecules and biomacromolecules in drug discovery. Inspired by successful macrocyclic drugs of natural origins, macrocycles are attracting more attention for enhanced binding affinity and target selectivity. Due to the conformation constraint and structure preorganization, macrocycles can reach bioactive conformations more easily than parent acyclic compounds. Also, rational macrocyclization combined with sequent structural modification will help improve oral bioavailability and combat drug resistance. This review introduces various strategies to enhance membrane permeability in macrocyclization and subsequent modification, such as N-methylation, intramolecular hydrogen bonding modulation, isomerization, and reversible bicyclization. Several case studies highlight macrocyclic inhibitors targeting kinases, HDAC, and protein-protein interactions. Finally, some macrocyclic agents targeting tumor microenvironments are illustrated.

Oral Absorption of Middle-to-Large Molecules and Its Improvement, with a Focus on New Modality Drugs

To meet unmet medical needs, middle-to-large molecules, including peptides and oligonucleotides, have emerged as new therapeutic modalities. Owing to their middle-to-large molecular sizes, middle-to-large molecules are not suitable for oral absorption, but there are high expectations around orally bioavailable macromolecular drugs, since oral administration is the most convenient dosing route. Therefore, extensive efforts have been made to create bioavailable middle-to-large molecules or develop absorption enhancement technology, from which some successes have recently been reported. For example, Rybelsus® tablets and Mycapssa® capsules, both of which contain absorption enhancers, were approved as oral medications for type 2 diabetes and acromegaly, respectively. The oral administration of Rybelsus and Mycapssa exposes their pharmacologically active peptides with molecular weights greater than 1000, namely, semaglutide and octreotide, respectively, into systemic circulation. Although these two medications represent major achievements in the development of orally absorbable peptide formulations, the oral bioavailability of peptides after taking Rybelsus and Mycapssa is still only around 1%. In this article, we review the approaches and recent advances of orally bioavailable middle-to-large molecules and discuss challenges for improving their oral absorption.

Predominant genetic mutations leading to or predisposing diabetes progress: A Review

Diabetes mellitus (DM) arises following poor capacity to generate or secrete insulin or insulin resistance; hence insulin production impairment creates the illness. Individuals can control their weight, impulsivity, blood pressure, and blood lipids at the commencement of the disease. A single genetic mutation affects nearly 3% of people with diabetes. Surprisingly, beta cell function is regulated by more than 20 genes. Benefits of genetic diagnosis include improved therapy, better prediction of illness prognosis and progression, genetic counseling, and possibly prevention. Alpha HNF1 mutations in the early stages may respond to the regimen. Still, most patients need it because they control their blood glucose and will be subject to microvascular or macrovascular complications. In cases where insulin does not control sugar, using low-dose sulfonylureas would be beneficial and lower four times the glucose metabolism of metformin. These patients are susceptible to sulfonylureas and may be treated for years in case of no blood glucose attack complications. The drug will start at one-fourth of the adult dose: MODY1. It is caused by a mutation in the alpha-HNF 4 gene and is relatively uncommon. The same is true, but the threshold for renal excretion is not low, and the incidence of upward alpha-HNF 4 mutations in cases where there is a robust clinical panel for alpha HNF 1 but not confirmed by genetic sequencing should be considered. The disease is also susceptible to sulfonylureas: MODY4 with a mutation in the MODY6 gene, IPF1, with a mutation in MODY7, NeuroD1 is characterized by a carboxy sterilise mutation, which is not common: MODY2. In children and adolescents, an increment in fasting blood glucose of 100 to 150 mg/dl is not typical. The incidence of this condition is usually considered to be type 1 or 2 diabetes, but a large percentage of the above patients are heterozygote individuals, the glucokinase mutations. Specific mutations, including those rare variants in WFS1 and ABCC8 genes, insulin receptor (IR), fructose 6-phosphate aminotransferase (GFPT2), and nitric oxide synthase (eNOS), as well as mouse pancreatic β‐cell lines (Min6 and SJ cells), showed that the HDAC4 variant (p. His227Arg) had been directly linked with T2DM. Keywords: type-2 diabetes, genetic mutations, risk factors

Zinc insulin hexamer loaded alginate zinc hydrogel: preparation, characterization and in vivo hypoglycemic ability

Alginate zinc hydrogel loaded with zinc insulin hexamer was prepared and characterized for oral insulin administration. The hydrogel was fabricated by dripping zinc insulin hexamer into sodium alginate solution and followed by crosslinking by zinc chloride. SEM image reveals the zinc insulin hexamer was integrated into the matrix of hydrogel. Zinc insulin hexamer loaded hydrogel shows no obvious cytotoxicity to both HT29 and Caco-2 cells. The developed hydrogel retards the burst release of insulin in simulated gastric fluid but promotes the release when in simulated intestinal fluid. In the diabetic mice, zinc insulin hexamer loaded alginate hydrogel demonstrates significant and prolonged hypoglycemic effect.

Cell-Penetrating d-Peptides Retain Antisense Morpholino Oligomer Delivery Activity

Cell-penetrating peptides (CPPs) can cross the cell membrane to enter the cytosol and deliver otherwise nonpenetrant macromolecules such as proteins and oligonucleotides. For example, recent clinical trials have shown that a CPP attached to phosphorodiamidate morpholino oligomers (PMOs) resulted in higher muscle concentration, increased exon skipping, and dystrophin production relative to another study of the PMO alone in patients of Duchenne muscular dystrophy. Therefore, effective design and the study of CPPs could help enhance therapies for difficult-to-treat diseases. So far, the study of CPPs for PMO delivery has been restricted to predominantly canonical l-peptides. We hypothesized that mirror-image d-peptides could have similar PMO delivery activity as well as enhanced proteolytic stability, facilitating their characterization and quantification from biological milieu. We found that several enantiomeric peptide sequences could deliver a PMO-biotin cargo with similar activities while remaining stable against serum proteolysis. The biotin label allowed for affinity capture of fully intact PMO-peptide conjugates from whole-cell and cytosolic lysates. By profiling a mixture of these constructs in cells, we determined their relative intracellular concentrations. When combined with PMO activity, these concentrations provide a new metric for delivery efficiency, which may be useful for determining which peptide sequence to pursue in further preclinical studies.

Advances in oral peptide drug nanoparticles for diabetes mellitus treatment

Peptide drugs play an important role in diabetes mellitus treatment. Oral administration of peptide drugs is a promising strategy for diabetes mellitus because of its convenience and high patient compliance compared to parenteral administration routes. However, there are a series of formidable unfavorable conditions present in the gastrointestinal (GI) tract after oral administration, which result in the low oral bioavailability of these peptide drugs. To overcome these challenges, various nanoparticles (NPs) have been developed to improve the oral absorption of peptide drugs due to their unique in vivo properties and high design flexibility. This review discusses the unfavorable conditions present in the GI tract and provides the corresponding strategies to overcome these challenges. The review provides a comprehensive overview on the NPs that have been constructed for oral peptide drug delivery in diabetes mellitus treatment. Finally, we will discuss the rational application and give some suggestions that can be utilized for the development of oral peptide drug NPs. Our aim is to provide a systemic and comprehensive review of oral peptide drug NPs that can overcome the challenges in GI tract for efficient treatment of diabetes mellitus.

•Oral administration of peptide drugs is a promising strategy for diabetes mellitus treatment

•A series of formidable unfavorable conditions in gastrointestinal tract result in the low oral bioavailability of peptide drugs

•Nanoparticles can improve the oral bioavailability of peptide drugs

Evolution of drug delivery systems: From 1950 to 2020 and beyond

Modern drug delivery technology began in 1952 with the advent of the Spansule® sustained-release capsule technology, which can deliver a drug for 12 h after oral administration through an initial immediate dose followed by the remaining released gradually. Until the 1980s, oral and transdermal formulations providing therapeutic durations up to 24 h for small molecules dominated the drug delivery field and the market. The introduction of Lupron Depot® in 1989 opened the door for long-acting injectables and implantables, extending the drug delivery duration from days to months and occasionally years. Notably, the new technologies allowed long-term delivery of peptide and protein drugs, although limited to parenteral administration. The introduction of the first PEGylated protein, Adagen®, in 1990 marked the new era of PEGylation, resulting in Doxil® (doxorubicin in PEGylated liposome) in 1995, Movantik® (PEGylated naloxone - naloxegol) in 2014, and Onpattro® (Patisiran - siRNA in PEGylated lipid nanoparticle) in 2018. Drug-polymer complexes were introduced, e.g., InFed® (iron-dextran complex injection) in 1974 and Abraxane® (paclitaxel-albumin complex) in 2005. In 2000, both Mylotarg™ (antibody-drug conjugate - gemtuzumab ozogamicin) and Rapamune® (sirolimus nanocrystal formulation) were introduced. The year 2000 also marked the launching of the National Nanotechnology Initiative by the U.S. government, which was soon followed by the rest of the world. Extensive work on nanomedicine, particularly formulations designed to escape from endosomes after being taken by tumor cells, along with PEGylation technology, ultimately resulted in the timely development of lipid nanoparticle formulations for COVID-19 vaccine delivery in 2020. While the advances in drug delivery technologies for the last seven decades are breathtaking, they are only the tip of an iceberg of technologies that have yet to be utilized in an approved formulation or even to be discovered. As life expectancy continues to increase, more people require long-term care for various diseases. Filling the current and future unmet needs requires innovative drug delivery technologies to overcome age-old familiar hurdles, e.g., improving water-solubility of poorly soluble drugs, overcoming biological barriers, and developing more efficient long-acting depot formulations. The lessons learned from the past are essential assets for developing future drug delivery technologies implemented into products. As the development of COVID-19 vaccines demonstrated, meeting the unforeseen crisis of the uncertain future requires continuous cumulation of failures (as learning experiences), knowledge, and technologies. Conscious efforts of supporting diversified research topics in the drug delivery field are urgently needed more than ever.

[A novel way of modification of AT1 angiotensin receptors to alleviate neonatal and infantile heart failure]

Heart failure is an important cause of death of children. Especially, overt one within the preweaning period is fulminant and severe. However, there are no drugs with evidence for it. We recently found that angiotensin II (AngII) activates L-type Ca²⁺ channels through AT₁ receptors (AT₁R) and β-arrestin 2 in murine cardiac myocytes only in the preweaning period, indicating that AT₁R/β-arrestin 2 pathway mediates positive inotropic effects before weaning. Indeed, β-arrestin-bias AT₁R agonist (BBA), TRV027 caused significant long-lasting positive inotropic effects in preweaning mice without increasing serum aldosterone concentrations or inducing tachycardia, arrhythmias, increased cardiac oxygen consumption, and reactive oxygen species generation. TRV027 increased the peak amplitude of twitch Ca²⁺ transients not only in preweaning mouse cardiac myocytes but in human iPS cell-derived cardiac myocytes exhibiting the fetal to neonatal phenotype. Moreover, TRV027 also increased contraction of the compromised heart of the model knock-in mice mimicking human congenital dilated cardiomyopathy. Although ~80% of these mice died before weaning, TRV027 significantly increased their survival rate. TRV027 did not cause any obvious adverse effects on their preweaning wildtype littermates. Thus, we reason in this review that BBA can be important therapeutics for preweaning heart failure.

Biotherapeutic effect of cell-penetrating peptides against microbial agents: a review

Selective permeability of biological membranes represents a significant barrier to the delivery of therapeutic substances into both microorganisms and mammalian cells, restricting the access of drugs into intracellular pathogens. Cell-penetrating peptides usually 5-30 amino acids with the characteristic ability to penetrate biological membranes have emerged as promising antimicrobial agents for treating infections as well as an effective delivery modality for biological conjugates such as nucleic acids, drugs, vaccines, nanoparticles, and therapeutic antibodies. However, several factors such as antimicrobial resistance and poor drug delivery of the existing medications justify the urgent need for developing a new class of antimicrobials. Herein, we review cell-penetrating peptides (CPPs) used to treat microbial infections. Although these peptides are biologically active for infections, effective transduction into membranes and cargo transport, serum stability, and half-life must be improved for optimum functions and development of next-generation antimicrobial agents.