Bacterial delivery of pro-apoptotic proteins in advanced hepatocellular carcinoma.

Summary There are no curative treatments for patients with unresectable hepatocellular carcinoma (HCC) at this time. The prognosis for these patients is dismal. With current standard of care treatment methods, the median survival time is, at best, 20 months. We propose to develop a safe and effective therapy for HCC that employs Salmonella to deliver active caspase-3 selectively to tumors. Activating executioner caspases, the final committed steps of apoptosis, circumvent the mechanisms that cancers acquire to avoid cell death. Systemic delivery of active caspases is unfeasible because it would induce severe side effects and be poorly taken up into cells. In contrast, Salmonella accumulate in HCC in ratios of 100,000 to 1 compared to healthy tissues and, as a result, can deliver proteins with high specificity to cancer cells with minimal systemic side effects. The proof of concept for this study has been established by demonstrating that 1) a bacterial delivery system can delivery proteins specifically into cancer cells and 2) bacterial delivery of active casp-3 induces cell death in cancer cells and reduces tumor volume in subcutaneous HCC in mice. In this proposal, we want to determine the safety and efficacy of bacterially delivered active casp-3 (EBT-002) in mice compared to standard of care and investigate the combination with immune checkpoint blockade. In Aim 1, we will quantify the effect of EBT-002 on the activation of apoptosis in subcutaneous HCC tumors and on tumor volume in an orthotopic liver tumor model. In Aim 2, we will determine the maximum tolerated dose (MTD) of EBT-002 and study acute toxicity in a dose-escalation study as well as liver toxicity in a cirrhotic liver background. We will measure the biodistribution of this therapy in mice with tumors to determine off-target bacterial accumulation. We will also determine the maximum effective dose. We hypothesize that at high bacterial dosage, efficacy is independent of dose. This would enable a reduction of dose, while maintaining the same efficacy measured at MTD. In Aim 3, we will determine the effect of EBT-002 on T-cell infiltration and tumor proliferation in tumors with high and low PD-L1 expression. This will be tested in combination with anti-PD-L1 antibodies, to evaluate if this combination can increase efficacy of both therapies in tumors that are responsive and non-responsive to checkpoint inhibitors. The successful outcome of this proposal is the first step in the development of EBT-002 as a new therapy for HCC. Further development of this therapy will be pursued in a Phase II SBIR to obtain the necessary data for an IND application. This research will establish a platform technology to directly deliver proteins into cells at critical points in signaling pathways and will be effective in a wide array of cancers.Narrative The experimental plan describes the generation of a bacterial therapy that activates apoptosis in advanced hepatocellular carcinoma (EBT-002). The research plan measures the efficacy of EBT-002 in an orthotopic liver cancer models and determines the safety profile in mice with tumors and cirrhosis.