Epidermal growth factor fusion toxin(Ligand Pharmaceuticals)

Purpose: The novel fusion protein, DAB389EGF, is composed of both the catalytic and the translocation domains of diphtheria toxin that are fused to the human EGF, providing a targeting and a toxicity component. We tested DAB389EGF for antitumor activity in both in vitro and in vivo urinary bladder cancer models.Experimental Design: Human bladder cancer lines were treated with DAB389EGF and assessed for growth inhibition and clonogenic suppression. Using 6- to 8-week-old female athymic nude mice implanted orthotopically with HTB9 cells, DAB389EGF was administered intravesically twice weekly for 2 weeks. The response of the luciferase-expressing HTB9 cells was monitored via bioluminescence as the primary endpoint.Results: Treatment response with DAB389EGF was specific and robust, with an IC50 ranging from 0.5 to 15 ng/mL in eight tested bladder cancer cell lines, but greater than 50 ng/mL in the EGF receptor (EGFR)-negative H520 control cell line. Simulating short-duration intravesical therapy used clinically, a 2-hour treatment exposure of DAB389EGF (10 ng/mL) produced clonogenic suppression in three selected bladder cancer cell lines. In vivo, luciferase activity was suppressed in five of six mice treated with DAB389EGF [70 μL (1 ng/μL) per mouse], as compared with only one of six mice treated with a control diphtheria toxin (DT) fusion protein. Histologic assessment of tumor clearance correlated with the bioluminescent changes observed with DAB389EGF treatment. Immunocompetent mice treated with intravesical DAB389EGF did not show any nonspecific systemic toxicity.Conclusions: The intravesical delivery of targeted toxin fusion proteins is a novel treatment approach for non–muscle-invasive urinary bladder cancer. With appropriate targeting, the treatments are effective and well-tolerated in vivo. Clin Cancer Res; 19(1); 148–57. ©2012 AACR.

Purpose: The novel fusion protein, DAB389EGF, composed of the catalytic and translocation domains of diphtheria toxin (DAB389) fused with a His-Ala linker to human epidermal growth factor (EGF) was tested for antiglioma efficacy in an in vivo model of human glioma.Experimental Design: Female athymic nude mice (ages 4-6 weeks) were inoculated s.c. with 10 million U87MG human glioma cells in the right flank. When tumor volumes reached ∼100 mm3 (∼6-8 days), i.t. injections of saline, DAB389IL2, or DAB389EGF 1, 3, 5 or 10 μg in 50 μL were given every other day for three to six doses. Animals were monitored twice daily and tumor measurements were made by calipers.Results: The maximal tolerated dose (MTD) of DAB389EGF was 3 μg every other day. Above the MTD, animals experienced loss of activity, reduced oral intake, and dehydration. Blood chemistries confirmed elevated blood urea nitrogen, creatinine, aspartate transaminase, and alanine transaminase. Histopathology revealed renal tubular necrosis. At the MTD, tumor regression was seen in all animals. Relapses occurred in 4 of 16 (25%) of animals after 1 month. These tumors contained EGF receptor, were sensitive in vitro to DAB389EGF, and responded to a second course of i.t. DAB389EGF.Conclusions: DAB389EGF fusion protein shows in vivo antiglioma efficacy in a s.c. tumor model and warrants further preclinical testing in an i.c. tumor model for eventual treatment of patients with recurrent or refractory EGF receptor–positive glioblastoma multiforme.