Bispecific Targeted Toxin DTATEGF Against Metastatic NSCLC Brain Tumors

Chemotherapy and radiotherapy of metastatic brain tumors can cause serious side effects that result from toxicity to the normal neural tissue that is adjacent to the tumor. Surgery and stereotactic radiosurgery represent focal therapies that do not address the micrometastases that are not demonstrated on magnetic resonance imaging (MRI). For that reason, the bispecific targeted toxin (DTATEGF) was developed to treat non-small cell lung cancer (NSCLC). DTATEGF is a diphtheria toxin (DT)-based immunotoxin that targets the epidermal growth factor (EGF) receptor (EGFR) found on tumor cells and the urokinase-type plasminogen activator (uPA) receptor (uPAR) located on both tumors and their blood vessels. The drug was tested against a human metastatic NSCLC cell line (PC9-BrM3) both in vitro and in vivo. Using an implanted osmotic minipump, DTATEGF was infused directly into the intracerebral tumor over 7 days by convection-enhanced delivery (CED) in a mouse xenograft model in vivo. Various concentrations of bispecific DTATEGF, monospecific DTAT and DTEGF, and control DT were tested for their ability to inhibit PC9-BrM3 cell proliferation in an MTT assay in vitro. The human NSCLC PC9-BrM3 cell line was genetically labeled with a firefly luciferase reporter gene which allowed for bioluminescent imaging (BLI) at 7 days, 14 days, 1 month, 2 months, and 3 months after intracerebral tumor implantation. The treatment group received 1 microgram (μg) of DTATEGF and the control group received 1. μg of DT. Kaplan-Meier survival curves were generated and brain tissue samples were stained with hematoxylin and eosin for histopathological analysis. In vitro results showed that the IC50 for DTATEGF was less than 0.001. nM which is 100-1000-fold more active that either DTAT or DTEGF. In mice treated with DTATEGF via CED there was a survival benefit compared to control animals that was statistically significant; 87 vs 63 days, p=0.006. These results indicate that DTATEGF is effective both in vitro and in vivo against metastatic PC9-BrM3 NSCLC cells or tumors, respectively. Further development of this agent for the treatment of NSCLC is warranted based on this work.