Type 2 diabetes mellitus (T2DM) continues to be a substantial medical problem due to its increasing global prevalence and because chronic hyperglycemic states are closely linked with obesity, liver disease and several cardiovascular diseases. Since the early discovery of insulin, numerous antihyperglycemic drug therapies to treat diabetes have been approved, and also discontinued, by the United States Food and Drug Administration (FDA). To provide an up-to-date account of the current trends of antidiabetic pharmaceuticals, this review offers a comprehensive analysis of the main classes of antihyperglycemic compounds and their mechanisms: insulin types, biguanides, sulfonylureas, meglitinides (glinides), alpha-glucosidase inhibitors (AGIs), thiazolidinediones (TZD), incretin-dependent therapies, sodium-glucose cotransporter type 2 (SGLT2) inhibitors and combinations thereof. The number of therapeutic alternatives to treat T2DM are increasing and now there are nearly 60 drugs approved by the FDA. Beyond this there are nearly 100 additional antidiabetic agents being evaluated in clinical trials. In addition to the standard treatments of insulin therapy and metformin, there are new drug combinations, e.g., containing metformin, SGLT2 inhibitors and dipeptidyl peptidase-4 (DPP4) inhibitors, that have gained substantial use during the last decade. Furthermore, there are several interesting alternatives, such as lobeglitazone, efpeglenatide and tirzepatide, in ongoing clinical trials. Modern drugs, such as glucagon-like peptide-1 (GLP-1) receptor agonists, DPP4 inhibitors and SGLT2 inhibitors have gained popularity on the pharmaceutical market, while less expensive over the counter alternatives are increasing in developing economies. The large heterogeneity of T2DM is also creating a push towards more personalized and accessible treatments. We describe several interesting alternatives in ongoing clinical trials, which may help to achieve this in the near future.

Compounds that contain (R)-3-amino-4-(2,4,5-trifluorophenyl)butanoic acid substituted with bicyclic amino moiety (2-aza-bicyclo[2.2.1]heptane) were designed using molecular modelling methods, synthesised, and found to be potent DPP-4 (dipeptidyl peptidase-4) inhibitors. Compound 12a (IC50 = 16.8 ± 2.2 nM), named neogliptin, is a more potent DPP-4 inhibitor than vildagliptin and sitagliptin. Neogliptin interacts with key DPP-4 residues in the active site and has pharmacophore parameters similar to vildagliptin and sitagliptin. It was found to have a low cardiotoxic effect compared to sitagliptin, and it is superior to vildagliptin in terms of ADME properties. Moreover, compound 12a is stable in aqueous solutions due to its low intramolecular cyclisation potential. These findings suggest that compound 12a has unique properties and can act as a template for further type 2 diabetes mellitus drug development.

Background: The renin-angiotensin system involves many more enzymes, receptors and biologically active peptides than originally thought. With this study, we investigated whether angiotensin-(1-5) [Ang-(1-5)], a 5-amino acid fragment of angiotensin II, has biological activity, and through which receptor it elicits effects. Methods: The effect of Ang-(1-5) (1µM) on nitric oxide release was measured by DAF-FM staining in human aortic endothelial cells (HAEC), or Chinese Hamster Ovary (CHO) cells stably transfected with the angiotensin AT ₂ -receptor (AT ₂ R) or the receptor Mas. A potential vasodilatory effect of Ang-(1-5) was tested in mouse mesenteric and human renal arteries by wire myography; the effect on blood pressure was evaluated in normotensive C57BL/6 mice by Millar catheter. These experiments were performed in the presence or absence of a range of antagonists or inhibitors or in AT ₂ R-knockout mice. Binding of Ang-(1-5) to the AT ₂ R was confirmed and the preferred conformations determined by in silico docking simulations. The signaling network of Ang-(1-5) was mapped by quantitative phosphoproteomics. Results: Key findings included: (1) Ang-(1-5) induced activation of eNOS by changes in phosphorylation at ^Ser1177 eNOS and ^Tyr657 eNOS and thereby (2) increased NO release from HAEC and AT ₂ R-transfected CHO cells, but not from Mas-transfected or non-transfected CHO cells. (3) Ang-(1-5) induced relaxation of preconstricted mouse mesenteric and human renal arteries and (4) lowered blood pressure in normotensive mice – effects which were respectively absent in arteries from AT ₂ R-KO or in PD123319-treated mice and which were more potent than effects of the established AT ₂ R-agonist C21. (5) According to in silico modelling, Ang-(1-5) binds to the AT ₂ R in two preferred conformations, one differing substantially from where the first five amino acids within angiotensin II bind to the AT ₂ R. (6) Ang-(1-5) modifies signaling pathways in a protective RAS-typical way and with relevance for endothelial cell physiology and disease. Conclusions: Ang-(1-5) is a potent, endogenous AT ₂ R-agonist.

Small tripeptides composed entirely of β³-amino acids have been shown to self-assemble into fibres following acylation of the N-terminus. Given the use of Fmoc as a strategy to initiate self-assembly in α-peptides, we hypothesized that the acyl cap can be replaced by an Fmoc without perturbation to the self-assembly and enable simpler synthetic protocols. We therefore replaced the N-acyl cap for an Fmoc group and herein we show that these Fmoc-protected β³-peptides produce regular spherical particles, rather than fibrous structures, that are stable and capable of encapsulating cargo. We then demonstrated that these particles were able to deliver cargo to cells without any obvious signs of cytotoxicity. This is the first description of such regular nanoparticles derived from Fmoc-protected β³-peptides.

Background: Type 2 diabetes mellitus (T2DM) is a prevalent metabolic disease with global implications, necessitating effective management strategies. Dipeptidyl peptidase IV (DPP-4) inhibitors have shown promise as potent agents for T2DM treatment. Methods: This study combines chemical synthesis, molecular modelling, and inhibitory activity assays to characterise the structure–activity relationship of novel isomeric 1,2,4-oxadiazole-substituted derivatives of the 2-azabicyclo[2.2.1]heptane scaffold acylated with (R)-3-amino-4-(2,4,5-trifluorophenyl)butanoic acid. Results: In this article, we demonstrate the efficacy of new compounds as robust inhibitors of DPP-4. The attempts to further modify neogliptin (our lead compound described previously) resulted in a more potent DPP-4 inhibitor 9a (IC₅₀ = 4.3 nM), which did not mediate any substantial inhibition of DPP-8 and DPP-9. Conclusions: This study demonstrates that pseudo peptides incorporating (R)-3-amino-4-(2,4,5-trifluorophenyl)butanoic acid, a 2-aza-bicyclo[2.2.1]heptane moiety, and 1,2,4-oxadiazole substituents act as potent and selective DPP-4 inhibitors. By the stereochemical refinement of oxadiazole derivatives of neogliptin, we discovered compound 9a, a strong candidate for further development in T2DM treatment.