A recombinant form of Pseudomonas exotoxin A containing transforming growth factor alpha near its carboxyl terminus for the treatment of bladder cancer.

The epidermal growth factor receptor (EGFR) is overexpressed on the superficial layers of malignant urothelium and is suspected of playing a role in tumor progression. TP40 is a chimeric protein composed of transforming growth factor-alpha (TGF alpha) fused to a modified form of Pseudomonas exotoxin A (PE) that is selectively cytotoxic to EGFR-bearing cells and is currently undergoing clinical study for the intravesical therapy of bladder cancer. We constructed a recombinant toxin PE35/TGF alpha-KDEL as an improved agent for the local therapy of EGFR-bearing bladder cancer. PE35/TGF alpha-KDEL does not require intracellular proteolysis to generate a carboxyl-terminal fragment capable of reaching the target cell cytosol and contains a modified carboxyl-terminal sequence KDEL, that increases toxin activity. These features make PE35/TGF alpha-KDEL from 10- to 700-fold more potent than TP40 on four human bladder cancer cell lines. PE35/TGF alpha-KDEL may be a useful agent for treatment of EGFR-bearing cancers.