Oomycete-IN-1 (Compound X4) is a selective inhibitor targeting the PH domain of the PcORP1 protein in Phytophthora. It exhibits EC50 values ranging from 1-4 µg/mL against six oomycetes. Oomycete-IN-1 disrupts lipid transport and metabolism, leading to hyphal overgrowth and membrane folding in P. capsici. This compound is useful for research on controlling oomycete diseases, such as P. capsici infections.