Design of potent, proteolytically stable stapled lipopeptide analogues of BimBH3 as PTP1B inhibitors for diabetes therapy.

Protein tyrosine phosphatase 1B (PTP1B) serves as a key negative regulator of both insulin and leptin signaling pathways, and its inhibition represents a potential dual-mechanism therapeutic strategy for type 2 diabetes and obesity by simultaneously improving insulin sensitivity and leptin signaling. However, the clinical translation of peptide-based therapeutics is often hindered by poor proteolytic stability and short in vivo half-life. To address these challenges, we implemented a rational dual-modification strategy combining fatty acid conjugation and lactam stapling. Specifically, N-terminal fatty acid conjugation was introduced to prolong systemic circulation through reversible albumin binding, while intramolecular lactam stapling at i+3 positions was employed to constrain the peptide backbone, and improve resistance to enzymatic degradation and target binding affinity. In the present study, 19 lactam-stapled lipopeptide analogues of BimBH3 were designed and synthesized aiming to find potent, proteolytically stable peptide PTP1B inhibitors for diabetes therapy. Structure-activity relationship (SAR) studies identified compounds G4 and G14 as the most potent analogues, exhibiting IC50 values of 459.3 nM and 381.5 nM against PTP1B, respectively. Stability studies further demonstrated that the dual-modification strategy significantly improved metabolic stability. In a DPP-IV degradation assay, G4 and G14 displayed extended half-lives of approximately 11 h, corresponding to a 3.5-fold increase compared to the lead compound SM-6 (t1/2 = 3.195 h). Moreover, these compounds showed prolonged in vitro plasma stability with half-lives reaching 96.47 h for G4 and 112.1 h for G14, highlighting their potential for sustained in vivo potency. In cellular assays and in vivo oral glucose tolerance tests, both G4 and G14 showed promising cellular glucose tolerance and glycemic control efficacy in mice. These results highlight the potential of fatty acid conjugation and lactam stapling dual-modification strategy for the development of proteolytically stable, long-acting peptide drugs.