Definition

An antibody-drug conjugate (ADC) composed of a human immunoglobulin (Ig) G1 monoclonal antibody directed against the T-cell checkpoint ligand B7-homologue 3 (B7-H3, CD276) linked to an as of yet undefined cytotoxic agent, 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, internalization and linker cleavage, the cytotoxic agent is release and induces apoptosis specifically in B7-H3-expressing tumor cells through an as of yet undefined mechanism of action (MoA). 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.