Purpose: Metastasis to the brain from breast cancer remains a significant clinical challenge, and may be targeted with CAR-based immunotherapy. CAR design optimization for solid tumors is crucial due to the absence of truly restricted antigen expression and potential safety concerns with “on-target off-tumor” activity. Here, we have optimized HER2-CAR T cells for the treatment of breast to brain metastases, and determined optimal second-generation CAR design and route of administration for xenograft mouse models of breast metastatic brain tumors, including multifocal and leptomeningeal disease. Experimental Design: HER2-CAR constructs containing either CD28 or 4-1BB intracellular costimulatory signaling domains were compared for functional activity in vitro by measuring cytokine production, T-cell proliferation, and tumor killing capacity. We also evaluated HER2-CAR T cells delivered by intravenous, local intratumoral, or regional intraventricular routes of administration using in vivo human xenograft models of breast cancer that have metastasized to the brain. Results: Here, we have shown that HER2-CARs containing the 4-1BB costimulatory domain confer improved tumor targeting with reduced T-cell exhaustion phenotype and enhanced proliferative capacity compared with HER2-CARs containing the CD28 costimulatory domain. Local intracranial delivery of HER2-CARs showed potent in vivo antitumor activity in orthotopic xenograft models. Importantly, we demonstrated robust antitumor efficacy following regional intraventricular delivery of HER2-CAR T cells for the treatment of multifocal brain metastases and leptomeningeal disease. Conclusions: Our study shows the importance of CAR design in defining an optimized CAR T cell, and highlights intraventricular delivery of HER2-CAR T cells for treating multifocal brain metastases. Clin Cancer Res; 24(1); 95–105. ©2017 AACR.

An effective combination immunotherapy using oncolytic viruses delivers de novo CD19 to promote CD19-CAR T cell therapy against solid tumors in mice.

Advancing chimeric antigen receptor (CAR)-engineered adoptive T cells for the treatment of solid cancers is a major focus in the field of immunotherapy, given impressive recent clinical responses in hematological malignancies. Prostate cancer may be amenable to T cell-based immunotherapy since several tumor antigens, including prostate stem-cell antigen (PSCA), are widely over-expressed in metastatic disease. While antigen selectivity of CARs for solid cancers is crucial, it is problematic due to the absence of truly restricted tumor antigen expression and potential safety concerns with “on-target off-tumor” activity. Here, we show that the intracellular co-stimulatory signaling domain can determine a CAR's sensitivity for tumor antigen expression. A 4-1BB intracellular co-stimulatory signaling domain in PSCA-CARs confers improved selectivity for higher tumor antigen density, reduced T cell exhaustion phenotype, and equivalent tumor killing ability compared to PSCA-CARs containing the CD28 co-stimulatory signaling domain. PSCA-CARs exhibit robust in vivo anti-tumor activity in patient-derived bone-metastatic prostate cancer xenograft models, and 4-1BB-containing CARs show superior T cell persistence and control of disease compared with CD28-containing CARs. Our study demonstrates the importance of co-stimulation in defining an optimal CAR T cell, and also highlights the significance of clinically relevant models in developing solid cancer CAR T cell therapies.

Pancreatic ductal adenocarcinoma (PDAC) has been increasing by 0.5% per year in the United States. PDAC portends a dismal prognosis and novel therapies are needed. This study describes the generation and characterization of a novel oncolytic chimeric orthopoxvirus for the treatment of pancreatic cancer. After chimerization and high-throughput screening, CF33 was chosen from 100 new chimeric orthopoxvirus isolates for its ability to kill pancreatic cancer cells. In vitro cytotoxicity was assayed in six pancreatic cancer cell lines. In vivo efficacy and toxicity were evaluated in PANC-1 and MIA PaCa-2 xenograft models. CF33 caused rapid killing of six pancreatic cancer cells lines in vitro, releasing damage-associated molecular patterns, and regression of PANC-1 injected and non-injected distant xenografts in vivo after a single low intratumoral dose of 103 plaque-forming units. Using luciferase imaging, CF33 was noted to preferentially replicate in tumors which corresponds to the low viral titers found in solid organs. The low dose of CF33 required to treat pancreatic cancer in this preclinical study may ease the manufacturing and dosing challenges currently facing oncolytic viral therapy.

Peritoneal carcinomatosis (PC) from pancreatic ductal adenocarcinoma (PDAC) is fatal. Our preclinical study presents an effective treatment against PDAC PC using a novel oncolytic viral agent, CF33-hNIS-antiPDL1. CF33-hNIS-antiPDL1 is a genetically engineered chimeric orthopoxvirus, CF33, armed with the human Sodium Iodide Symporter (hNIS) and anti-PD-L1 antibody (anti-PD-L1). The in vitro cytotoxic ability of this virus against 5 PDAC cell lines was tested at various doses (multiplicity of infection [MOI] = 0.01, 0.1, 1, 10). Production and blockade function of virus-encoded anti-PD-L1 antibody were verified using immunoblot, immunoprecipitation, and PD-1/PD-L1 bioassay. In vivo mouse models of PC, with or without subcutaneous (SC) tumors, created by injecting AsPC-1-ffluc cells into nude mice, were treated with PBS or a single dose (1×10⁵ plaque-forming units) of either intraperitoneal (IP) or IV injection of CF33-hNIS-antiPDL1. Mice with PC tumors were treated on days 0, 2, or 14 after tumor implantation. CF33-hNIS-antiPDL1 killed PDAC cells in a dose-dependent manner, achieving >90% cell killing by day 8. Cells infected with CF33-hNIS-antiPDL1 produced bioactive anti-PD-L1 antibody, which blocked PD-1/PD-L1 interaction. In vivo, a single dose of virus reduced tumor burden and prolonged survival of treated mice. It was observed that IP administration of CF33-hNIS-antiPDL1 was more effective than IV administration. CF33-hNIS-antiPDL1 virus is effective in infecting and killing human PDACs and producing functional anti-PD-L1 antibody. Intraperitoneal delivery of CF33-hNIS-antiPDL1 effectively reduces peritoneal tumor burden and improves survival after only 1 dose and is superior to IV delivery.

This study hypothesizes that a novel oncolytic chimeric orthopoxvirus CF33-Fluc is imageable and targets colorectal cancer cells (CRCs). A novel chimeric orthopoxvirus (CF33) was constructed. The thymidine kinase locus was replaced with firefly luciferase (Fluc) to yield a recombinant virus-CF33-Fluc. In vitro cytotoxicity and viral replication assays were performed. In vivo CRC flank xenografts received single doses of intratumoral or intravenous CF33-Fluc. Viral biodistribution was analyzed via luciferase imaging and organ titers. CF33-Fluc infects, replicates in, and kills CRCs in vitro in a dose-dependent manner. CF33 has superior secretion of extracellular-enveloped virus versus all but one parental strain. Rapid tumor regression or stabilization occurred in vivo at a low dose over a short time period, regardless of the viral delivery method in the HCT-116 colorectal tumor xenograft model. Rapid luciferase expression in virus-infected tumor cells was associated with treatment response. CRC death occurs via necroptotic pathways. CF33-Fluc replicates in and kills colorectal cancer cells in vitro and in vivo regardless of delivery method. Expression of luciferase enables real-time tracking of viral replication. Despite the chimerism, CRC death occurs via standard poxvirus-induced mechanisms. Further studies are warranted in immunocompetent models.