Atezolizumab-MMAE is an anti-PD-L1 antibody-drug conjugate (ADC) with an EC50 of 1.1 nM. It consists of a humanized anti-PD-L1 antibody (Atezolizumab), a lysosome-cleavable dipeptide linker (valine-citrulline), and a tubulin inhibitor (MMAE), with the drug-linker conjugate being VcMMAE. This ADC exhibits potent cytotoxicity (EC50: 9.75-11.94 nM) and immune activation effects. In the MC38 xenograft humanized PD-1 immune system mouse model, Atezolizumab-MMAE demonstrates significant antitumor activity.

Atezolizumab-MMAE (Compound 3) at a concentration of 4 µg/mL over 0.5-24 hours binds to PD-L1 antigens on the cell membrane of MDA-MB-231 cells, becoming internalized and transported to lysosomes within 30 minutes. The compound (0.725-200,000 pmol/L, 3 days) exhibits potent tumor cell inhibitory activity with EC50 values of 10.33, 9.75, and 11.94 nM for PD-L1 positive MDA-MB-231, PC 9, and A431 cells, respectively, and shows weaker action on PD-L1 negative Romas cells with an EC50 of 129.4 nM. Additionally, Atezolizumab-MMAE (0.625-10 μg/mL, 48 hours) inhibits the PD1 and PD-L1 interaction and significantly increases IFN-γ levels when co-cultured with PBMCs.

Atezolizumab-MMAE (Compound 3) administered at 3 mg/kg via intraperitoneal injection twice weekly for 3 weeks exhibits superior antitumor effects compared to Atezolizumab alone in the MC38 xenograft PD-1 humanized immune system mouse model, achieving a 68% tumor inhibition rate and a 60% tumor regression rate.