An orally bioavailable, 3-amidinophenylalanine-derived, second generation serine protease inhibitor prodrug targeting the human urokinase plasminogen activator (uPA) system with potential antineoplastic and antimetastatic activities. After oral administration, upamostat is converted to the active N alpha-(2,4,6-triisopropylphenylsulfonyl)-3-amidino-(L)-phenylalanine-4-ethoxycarbonylpiperazide (WX-UK1), which inhibits several serine proteases, particularly uPA; inhibition of uPA may result in the inhibition of tumor growth and metastasis. uPA is a serine protease involved in degradation of the extracellular matrix and tumor cell migration and proliferation.