Locally constrained xylene-based cyclic mimetics of SOCS3 protein
Alessia Cugudda, Sara La Manna, Francesco Cozzolino, Iogann Tolbatov, Alessandro Marrone, Daniela Marasco · European Journal of Medicinal Chemistry · 2025
ABSTRACT The development of SOCS3 peptidomimetics targeting the JAK2 signaling pathway presents a promising strategy for modulating cytokine-driven diseases. In this study, we designed four novel monocyclic analogues of a previously reported linear lead compound (KIRCONG chim PEG), introducing local conformational constraints via regioselective thioether cyclization of either the KIR (thio-monoleft) or CONG (thio-monoright) regions. Each variant was synthesized with one or two PEG moieties (PEG 1 or PEG 2 ) to modulate solubility and flexibility. Microscale Thermophoresis (MST) revealed that thio-monoright PEG 1 exhibited the highest affinity for the JAK2 catalytic domain, and inhibition assays further confirmed its superior ability to suppress JAK2-mediated phosphorylation. Circular dichroism and metadynamics simulations indicated enhanced structural organization and intramolecular hydrogen bonding in cyclic analogues, especially thio-monoright PEG 1 , as supported by Natural Bond Orbital (NBO) and Second Order Perturbation Theory (SOPT) analyses. Conversely, PEG 2 -analogues showed reduced activity and solubility, likely due to increased flexibility and aggregation arising from hydrophobic surface exposure, as demonstrated by fluorescence spectroscopy and solvent-accessibility calculations. Overall, thio-monoright PEG 1 represents a promising conformationally stabilized SOCS3 mimetic with improved bioactivity, providing a rational foundation for further optimization of JAK2-targeting peptide therapeutics.