Engineered probiotics for local tumor delivery of checkpoint blockade nanobodies

Abstract

Checkpoint inhibitors have revolutionized cancer therapy but only work in a subset of patients and can lead to a multitude of toxicities, suggesting the need for more targeted delivery systems. Because of their preferential colonization of tumors, microbes are a natural platform for the local delivery of cancer therapeutics. Here, we engineer a probiotic bacteria system for the controlled production and intratumoral release of nanobodies targeting programmed cell death–ligand 1 (PD-L1) and cytotoxic T lymphocyte–associated protein-4 (CTLA-4) using a stabilized lysing release mechanism. We used computational modeling coupled with experimental validation of lysis circuit dynamics to determine the optimal genetic circuit parameters for maximal therapeutic efficacy. A single injection of this engineered system demonstrated an enhanced therapeutic response compared to analogous clinically relevant antibodies, resulting in tumor regression in syngeneic mouse models. Supporting the potentiation of a systemic immune response, we observed a relative increase in activated T cells, an abscopal effect, and corresponding increases in systemic T cell memory populations in mice treated with probiotically delivered checkpoint inhibitors. Last, we leveraged the modularity of our platform to achieve enhanced therapeutic efficacy in a poorly immunogenic syngeneic mouse model through effective combinations with a probiotically produced cytokine, granulocyte-macrophage colony-stimulating factor (GM-CSF). Together, these results demonstrate that our engineered probiotic system bridges synthetic biology and immunology to improve upon checkpoint blockade delivery.

Engineering microrobots for targeted cancer therapies from a medical perspective

“…A second pathway relies on microrobots eradicating cancer cells indirectly via their ability to activate or stimulate the patient's immune system against the targeted cancer. For example, bacteria-based strategies can help boost the overall therapeutic response not only to the originally injected cancer, but also to tumours occurring in other locations of the body 151 . This abscopal effect is particularly attractive for eliminating metastases and establishing a durable systemic anticancer response.…”

“…The early bacterial cancer therapies performed by William Coley in the late 19 th century highlight the issue of uncontrolled proliferation of bacteria, which is still limiting their clinical use. Thus, integrating self-destruction switches 184 as well as extending bacterial therapies to probiotic/commensal strains used as food supplements are being explored 151 , although part of the efficiency of some bacterial therapies seems to depend on their intrinsic toxicity. Further understanding of the precise mechanism-of-action of these cellular microrobots is therefore required to address these issues.…”

Nanobodies: Next Generation of Cancer Diagnostics and Therapeutics

“…Notably, “programmable” bacteria that release CD47-targeting nanobodies in the TME increased tumor regression and metastatic inhibition in vivo ( 214 ). Similarly, Gurbatri et al ( 215 ) engineered a probiotic system that could release anti-PD-L1 and anti-CTLA-4 nanobodies intratumorally, and a single dose reported efficacy comparable to mAbs in vivo , a potentiated systemic immune response, and synergistic potential with granulocyte-macrophage CSF (GM-CSF).…”

Diagnostic and Therapeutic Microbial Circuit with Application to Intestinal Inflammation

“…Engineering microbes for gut diagnostics and therapeutics is a growing field in synthetic biology, owing to the tractability and relative safety of genome engineering in microbes. Recent examples include inhibition of pathogenic Pseudomonas aeruginosa via antimicrobial peptides [4] and delivery of checkpoint blockade nanobodies to tumors [5]. Due to the presence of bacteria in a wide variety of ecological niches, there exists a wide variety of evolved sensors for therapeuticallyrelevant molecules [6].…”