Development of bifunctional anti-PD-L1 antibody MMAE conjugate with cytotoxicity and immunostimulation

In recent years, tumor immunotherapy, especially the combination of PD1/PD-L1 inhibitors and chemotherapy, has developed rapidly. However, the systemic side effects induced by chemotherapy remain a crucial problem that needs to be addressed. Antibody drug conjugates (ADCs) are exceptional target-specific prodrugs that greatly improve the therapeutic window of chemotherapy drugs. Therefore, designing PD-L1-targeting ADCs is an interesting research project. In this study, we confirmed for the first time that the commercial anti-PD-L1 antibody Atezolizumab has better endocytosis efficiencies than Avelumab, and was more suitable for ADC design. Then, the most popular cytotoxic payload MMAE was conjugated to Atezolizumab via a classical dipeptide (valine-alanine) linker to generate a bifunctional PD-L1 ADC (ADC 3). An in vitro cytotoxicity test indicated the potent tumor cell inhibitory activity of ADC 3, with EC50 values of 9.75 nM to 11.94 nM. In addition, a co-culture of PBMCs in vitro proved that ADC 3 retained the immune activation effect of the Atezolizumab antibody. Moreover, ADC 3 exhibited a higher tumor inhibition rate and tumor regression rate in humanized immune system mice. To the best of our knowledge, this is the most active PD-L1-ADC reported thus far, which may promote the development of immunotherapy and novel ADCs.

Automated summary

The study confirmed for the first time that Atezolizumab is more suitable for designing ADCs compared to Avelumab, with the generated ADC 3 exhibiting potent tumor cell inhibitory activity and immune activation effects. These findings have positive implications for cancer therapy.