Secreted effector that interacts with and inhibits the pathogenesis-related P69B subtilisin-like serine protease of host tomato (PubMed:15096512). Inhibition of host proteases by a pathogen extracellular protease inhibitor forms a specific type of defense-counterdefense mechanism between plants and microbial pathogens (PubMed:15096512). Interacts with host subtilisin-like protease P69B. Localizes to host apoplast where it targets defense proteases for inhibition. Expressed during host infection with the highest mRNA levels 3 days post-inoculation (PubMed:15096512). EPI1 and its host target P69B are concurrently expressed during infection of tomato by P.infestans (PubMed:15096512).