Sci. Transl. Med. 12, eaax0876 (2020)

PDL-1 and CTLA-4 antagonists can be delivered to tumors by engineered bacteria that then release this therapeutic payload.

Targeting therapy to tumors could reduce their toxicity and increase the efficacy of the therapy. Bacteria are known to preferentially colonize tumors, and this tendency could be leveraged to deliver therapies.

Gurbatri et al. engineered probiotic bacteria that were able to produce anti-PDL-1 and anti-CTLA-4 nanobodies that are checkpoint-blockade inhibitors that are released only when they reach a critical quorum. The authors found that injecting these bacteria into genetically similar, tumor-bearing mice resulted in higher therapeutic efficacy than that of the therapy alone.