A microbial-inspired antibody-drug conjugate for cancer immunotherapy

Generating antitumor immune responses requires the phagocytosis of tumor cells and subsequent cross-presentation of tumor-derived antigens by antigen-presenting cells. However, these processes are impeded by phagocytosis checkpoints and inefficient cytosolic transport of antigenic peptides from phagolysosomes. Here, using a microbial-inspired strategy, we engineered an antibody-drug conjugate (ADC) that targets the “don't eat me” signal CD47 linked to the bacterial toxin listeriolysin O from the intracellular bacterium Listeria monocytogenes via a cleavable linker (CD47-LLO). CD47-LLO promotes the phagocytosis of cancer cells followed by the release and activation of LLO to form pores on phagolysosomal membranes that allow cytosolic entry of tumor-derived contents, leading to enhanced antigen cross-presentation of tumor-derived peptides and activation of cytosolic immune sensors. CD47-LLO treatment in vivo significantly inhibited the growth of both localized and metastatic tumors and improved animal survival as monotherapy or in combination with checkpoint blockade. Together, these results demonstrate that designing ADCs to promote immune recognition of tumor cells represents a promising therapeutic strategy for treating multiple cancers. Overall design: To define the identities of innate and adaptive immune cells that accumulate in tumors upon CD47-LLO treatment, we performed single cell RNA (scRNA-seq) on CD45+ cells isolated from EO771 tumors. CD45+ cells were rare in IgG or anti-CD47 treated animals (Fig. 4a,b). In contrast, we observed a 30-fold increase in CD45+ cells upon CD47-LLO treatment. After rigorous quality control, we used our previously published methodsto annotate cells and interpret changes in their abundance and gene expression (n= 13,891 cells total).