Screening and evaluation of the hit compound from a DNA-encoded library derived from natural products based on...

The enormous growing demand for drug candidates binding to endothelin receptor A (ET_A) has made it necessary to continuously pursue new strategies for ligand screening and early evaluation. This work achieved the one-step immobilization of ET_A based on the bioorthogonal chemistry between the epidermal growth factor receptor tag (EGFR-tag) and ibrutinib. Comprehensive characterizations including Western blot analysis are performed to realize the morphology, antibody/ligand recognition activity, and specificity of the immobilized ET_A. Taking macitentan, ambrisentan, and bosentan as an example, we utilized the immobilized ET_A to construct a thermodynamic model for the evaluation of the specific ligands binding to ET_A. Using this model, we screened the potential compound NP845 from a DNA-encoded library with 10,686 members derived from natural products and calculated the association constant as (2.24 ± 0.15) × 10⁵ M^-1 at 37 °C, thereby demonstrating the good pharmacological activity of NP845. The entropy change (∆S^θ), enthalpy change (∆H^θ), and Gibbs free energy (∆G^θ) were 1.75 J/mol·K, -31.1 kJ/mol, and -31.6 kJ/mol at 37 °C, whereby we recognized the electrostatic force was the driving force of the interaction between NP845 and ET_A. In vitro cell tests proved that NP845 can downregulate the expression level of PKA, B-Raf, MEK, and ERK1 in VSMC. Our results indicated that NP845 was a potential lead compound for fighting the ailments mediated by ET_A.