An antibody-drug conjugate (ADC) composed of an antibody directed against 5T4 and conjugated, via a non-cleavable linker, to a proprietary polymer carrying multiple auristatin analog molecules via a cleavable linker, with potential antineoplastic activity. Upon administration, the antibody moiety of ASN004 selectively binds to cells expressing the 5T4 oncofetal antigen. After internalization and cleavage within the tumor cell cytosol, free auristatin analog molecules binds to tubulin and inhibits its polymerization, which may result in G2/M phase arrest and tumor cell apoptosis. 5T4, a transmembrane glycoprotein, is overexpressed by a variety of cancer cell types; its expression is correlated with increased invasiveness.