Maturation-promoting factor (MPF) is well-known as cell cycle regulator during oocyte maturation and fertilization. MPF activity maintains high levels and arrest the cell cycle progression until fertilization. After fertilization, Anaphase-promoting complex/cyclosome (APC/C) mediated degradation of cyclin B causes decrease of MPF activity. One of the cytostatic factor (CSF), Emi2 inhibits APC/C activity by binding to APC/C-cdc20, therefore blocks the proteolysis of cyclin B. Degradation of Emi2 requires phosphorylation by Polo-like kinase 1 (Plk1). Thus recognition and phosphorylation of Emi2 by Plk1 are essential step for meiotic cell cycle resumption. In our previous research, we found that two phosphorylated threonine regions at amino acid position 152 and 176 in Emi2 are respectively contributed for recognition by polo-box domain of Plk1. Peptidomimetics 103-8 can block the interaction between Plk1-PBD and Emi2, and therefore meiotic maturation and meiosis resumption via parthenogenetic activation were impaired. However, major drawback of 103-8 was the limitation of penetration through the cell membrane. We synthesized the new peptidomimetics and checked bioavailability in mammalian oocyte by injection and media treatment. Medium treatment with peptidomimetics C-4, meiotic maturation has significantly decreased and meiotic resumption via parthenogenetic activation has perfectly impaired. For the next experiment, we are preparing X-ray crystallography to identify the binding modes between Plk1-PBD and peptidomimetics C-4.