Pyrrole-Based Macrocyclic Small-Molecule Inhibitors That Target Oocyte Maturation

Polo-like kinase 1 (PLK1) plays crucial roles in various stages of oocyte maturation. Recently, we reported that the peptidomimetic compound AB103-8, which targets the polo box domain (PBD) of PLK1, affects oocyte meiotic maturation and the resumption of meiosis. However, to overcome the drawbacks of peptidic compounds, we designed and synthesized a series of pyrrole-based small-molecule inhibitors and tested them for their effects on the rates of porcine oocyte maturation. Among them, the macrocyclic compound (E/Z)-3-(2,16-dioxo-19-(4-phenylbutyl)-3,19-diazabicyclo[15.2.1]icosa-1(20),6,17-trien-3-yl)propyl dihydrogen phosphate (4) showed the highest inhibitory activity with enhanced inhibition against embryonic blastocyst formation. Furthermore, the addition of this compound to culture media efficiently blocked the maturation of porcine and mouse oocytes, indicating its ability to penetrate the zona pellucida and cell membrane. We investigated mouse oocytes treated with compound 4, and the resulting impairment of spindle formation confirmed PLK1 inhibition. Finally, molecular modeling studies with PLK1 PBD also confirmed the presence of significant interactions between compound 4 and PLK1 PBD binding pocket residues, including those in the phosphate, tyrosine-rich, and pyrrolidine binding pockets. Collectively, these results suggest that the macrocyclic compound 4 may serve as a promising template for the development of novel contraceptive agents.