Definition

An antibody-drug conjugate (ADC) consisting of a monoclonal antibody directed against leukocyte immunoglobulin-like receptor subfamily B member 4 (LILRB4; ILT3; ILT-3) conjugated to monomethyl auristatin E (MMAE), an auristatin derivative and potent microtubule disrupting agent, with potential antineoplastic activity. Upon administration of anti-LILRB4/MMAE ADC SG2918, the monoclonal antibody moiety targets and binds to LILRB4. After internalization of the agent, the MMAE moiety is released, binds to tubulin and inhibits its polymerization, which results in G2/M phase cell cycle arrest and apoptosis. This inhibits the proliferation of LILRB4-expressing tumor cells and may re-activate the immune system. LILRB4, an inhibitory immune receptor highly expressed on tumor-associated myeloid cells, primarily tolerogenic dendritic cells (DCs), myeloid-derived suppressor cells (MDSCs) and M2 macrophages, functions as an immune checkpoint that negatively regulates DC- and T-cell activation. It is upregulated in several tumor types and plays an important role in tumor infiltration, immunosuppression and immune tolerance.