Discovery of Novel PTP1B Inhibitors with Once-Weekly Therapeutic Potential for Type 2 Diabetes: Design, Synthesis, and In Vitro and In Vivo Investigations of BimBH3 Peptide Analogues

Fatty acid conjugated BimBH3 analogues with d‑amino acid substitution as PTPN1 inhibitors with enhanced activity, biostability and orally available potency for the treatment of diabetes

Protein tyrosine phosphatase non-receptor type 1 (PTPN1) is a crucial regulator of insulin and leptin signaling pathways, positioning it as a promising therapeutic target for the development of insulin sensitizers in the treatment of type 2 diabetes mellitus (T2DM). Our previous studies demonstrated that lipidated/acylated BimBH3 core peptide analogues function as potent PTPN1 inhibitors with potential for once-weekly hypoglycemic efficacy. Additionally, alanine scanning identified specific residues that could be modified without compromising inhibitory activity. In this study, we designed and synthesized 14 lipidated BimBH3 analogues incorporating d-amino acids through site-specific modifications to enhance peptide stability and activity. Among these, analogues D-1, D-9, D-10, D-11, D-12, and D-14 exhibited potent PTPN1 inhibitory activity, demonstrated significant resistance to proteolytic degradation, and showed good stability in mouse plasma. Notably, in glucose tolerance tests, subcutaneous administration of D-14 led to a significant 26.2 % reduction in blood glucose (AUC0-120 min), while oral administration achieved a 15.4 % reduction (AUC0-180 min), indicating promising oral bioavailability. Further analysis using molecular docking and kinetic studies confirmed the strong binding affinity of d-amino acid-containing BimBH3 analogues for PTPN1, supporting their potential for sustained hypoglycemic effects. Overall, our findings demonstrate that the dual modifications of d-amino acid substitution and lipid conjugation significantly enhance the inhibitory activity, bio-stability, and oral availability of BimBH3 analogues, highlighting their potential as novel, long-acting therapeutics for T2DM management.

Glycosylation Modification Balances the Aqueous Solubility of Lipidated Peptides and Facilitates Their Biostability

Protein tyrosine phosphatase N1 (PTPN1) is a key regulator of insulin and leptin signaling pathways, making it an attractive therapeutic target for type 2 diabetes. Recent studies have identified fatty acid conjugated BimBH3 analogues as promising PTPN1 inhibitors with antidiabetic potential. Peptide therapeutics have proven successful in the treatment of a wide range of medical conditions, yet challenges such as poor aqueous solubility, proteolytic degradation, and limited bioavailability still hinder their clinical application. In this study, we developed a series of novel BimBH3 peptide analogues through dual modifications involving fatty acid lipidation and glycosylation to address these limitations. These modifications significantly improved the peptides' solubility, proteolytic stability, and plasma half-life while preserving potent PTPN1 inhibitory activity, which is essential for enhancing insulin signaling in type 2 diabetes treatment. Among the analogues, compound L3 exhibited the most balanced profile, with an aqueous solubility increase over 10-fold, a half-life extension in rat plasma of 9.92-fold compared to the lead compound, and an IC50 of 0.78 μM against PTPN1. In vivo studies further demonstrated L3's efficacy in lowering blood glucose levels in mice. This study demonstrates the utility of glycosylation in overcoming the solubility and stability challenges associated with lipidated peptides. The optimized analogue L3 could serve as a proof of concept for developing novel long-acting PTPN1 inhibitors.

Protein tyrosine phosphatase 1B in metabolic diseases and drug development

Protein tyrosine phosphatase 1B (PTP1B), a non-transmembrane phosphatase, has a major role in a variety of signalling pathways, including direct negative regulation of classic insulin and leptin signalling pathways, and is implicated in the pathogenesis of several cardiometabolic diseases and cancers. As such, PTP1B has been a therapeutic target for over two decades, with PTP1B inhibitors identified either from natural sources or developed throughout the years. Some of these inhibitors have reached phase I and/or II clinical trials in humans for the treatment of type 2 diabetes mellitus, obesity and/or metastatic breast cancer. In this Review, we summarize the cellular processes and regulation of PTP1B, discuss evidence from in vivo preclinical and human studies of the association between PTP1B and different disorders, and discuss outcomes of clinical trials. We outline challenges associated with the targeting of this phosphatase (which was, until the past few years, viewed as difficult to target), the current state of the field of PTP1B inhibitors (and dual phosphatase inhibitors) and future directions for manipulating the activity of this key metabolic enzyme.

Site-Specifically Modified Peptide Inhibitors of Protein Tyrosine Phosphatase 1B and T-Cell Protein Tyrosine Phosphatase with Enhanced Stability and Improved In Vivo Long-Acting Activity

Protein tyrosine phosphatase 1B (PTP1B) and TC-PTP can function in a coordinated manner to regulate diverse biological processes including insulin and leptin signaling, T-cell activation, and tumor antigen presentation, which makes them potential targets for several therapeutic applications. We have previously demonstrated that the lipidated BimBH3 peptide analogues were a new class of promising PTP1B inhibitors with once-weekly antidiabetic potency. Herein, we chemically synthesized two series of BimBH3 analogues via site-specific modification and studied their structure-activity relationship. The screened analogues S2, S6, A2-14, A2-17, A2-20, and A2-21 exhibited an improved PTP1B/TC-PTP dual inhibitory activity and achieved good stability in the plasma of mice and dogs, which indicated long-acting potential. In mouse models of type 2 diabetes mellitus (T2DM), the selected analogues S6, S7, A2-20, and A2-21 with an excellent target activity and plasma stability generated once-weekly therapeutic potency for T2DM at lower dosage (0.5 μmol/kg). In addition, evidence was provided to confirm the cell permeability and targeted enrichment of the BimBH3 analogues. In summary, we report here that site-specific modification and long fatty acid conjugation afforded cell-permeable peptidomimetic analogues of BimBH3 with enhanced stability, in vivo activity, and long-acting pharmacokinetic profile. Our findings could guide the further optimization of BimBH3 analogues and provide a proof-of-concept for PTP1B/TC-PTP targeting as a new therapeutic approach for T2DM, which may facilitate the discovery and development of alternative once-weekly anti-T2DM drug candidates.

Bifunctionality of dirhodium tetracarboxylates in metallaphotocatalysis

Metallaphotocatalysis has been recognized as a pivotal catalysis enabling new reactivities. Traditional metallaphotocatalysis often requires two or more separate catalysts and exhibits flaw in cost and substrate-tolerance, thus representing an await-to-solve issue in catalysis. We herein realize metallaphotocatalysis with a bifunctional dirhodium tetracarboxylate ([Rh2]) alone. The [Rh2] shows an photocatalytic activity of promoting singlet oxygen (1O2) oxidation. By harnessing its photocatalytic activity, the [Rh2] catalyzes a photochemical cascade reaction (PCR) via combination of carbenoid chemistry and 1O2 chemistry. The PCR is characterized by high atom-efficiency, excellent stereoselectivities, mild conditions, scalable synthesis, and pharmaceutically interesting products. DFT calculations-aided mechanistic study rationalizes the reaction pathway and interprets the origin of stereoselectivities of the PCR. The products show inhibitory activity against PTP1B, being promising in the treatment of type II diabetes and cancers. Overall, here we show the bifunctional [Rh2] merges Rh-carbenoid chemistry and 1O2 chemistry.

Influence of Fatty Acid Modification on the Anticancer Activity of the Antimicrobial Peptide Figainin 1

Antimicrobial peptides derived from the skin secretions of amphibians have made important progress in tumor therapy due to their unique mechanism of destroying cell membranes. Figainin 1 (F1) is an 18-amino acid antimicrobial peptide from the skin secretions of Boana raniceps frogs. In a previous study, F1 was shown to inhibit cancer cell proliferation. F1 is composed entirely of natural amino acids; therefore, it is easily degraded by a variety of proteases, resulting in poor stability and a short half-life. In the present study, we used a fatty acid modification strategy to improve the stability of Figainin 1. Among the 8 peptides synthesized, A-10 showed the strongest antiproliferative activity against K562 cells and the other four tumor cell lines, and its stability against serum and proteinase K was improved compared with F1. We found that A-10 works through two mechanisms, cell membrane destruction and apoptosis, and can arrest the cell cycle in the G0/G1 phase. Moreover, A-10 exhibited self-assembly behavior. Overall, it is necessary to select a fatty acid with a suitable length for modification to improve the stability and antiproliferative activity of antimicrobial peptides. This study provides a good reference for the development of antimicrobial peptides as effective anticancer compounds.