An antibody-drug conjugate (ADC) composed of a humanized immunoglobulin (Ig) G1 monoclonal antibody directed against the T-cell checkpoint ligand B7-homologue 3 (B7-H3, CD276) covalently linked to a topoisomerase inhibitor (TOPOi), with potential antineoplastic activity. Upon administration of anti-B7-H3 ADC HS-20093, the anti-B7-H3 monoclonal antibody moiety targets and binds to B7-H3 expressed on tumor cells. Upon binding and internalization, the TOPOi is released, and inhibits DNA topoisomerase activity, thereby inhibiting DNA replication and resulting in cell cycle arrest and tumor cell apoptosis. This inhibits the proliferation of B7-H3-expressing tumor cells. B7-H3, a type I transmembrane protein and a member of the B7 co-stimulatory protein superfamily, is an immunoregulatory protein overexpressed on certain tumor cell types and on various immune cells. It is a negative regulator of the T-cell activation and its overexpression plays a key role in tumor cell invasion and metastasis.