The Brennen laboratory takes a rigorous, multi-disciplinary, team-based approach towards developing innovative therapeutic and prognostic strategies for prostate cancer with an emphasis on exploiting vulnerabilities within the tumor microenvironment towards this goal. To accomplish this goal, we are strategically pursuing novel therapeutic platforms, including stromal-targeted prodrugs, protoxins, and radiolabeled antibodies, in addition to cell-based therapy and drug delivery; all of which are designed to reduce toxicity to peripheral non-target tissue (i.e. side effects) while maximizing anti-tumor efficacy (i.e. therapeutic benefit). Currently, many of these strategies are focused on overcoming stromal barriers to anti-tumor immune responses such that men suffering from prostate cancer can share in the immense, revolutionary power of immunotherapy that is transforming care for many with advanced disease in other tumor types previously thought to be unmanageable using conventional approaches. Unfortunately, prostate cancer has largely proven refractory to these powerful approaches thus far and requires novel mono- or combinatorial treatment strategies to unleash the full potential of the immune system and generate personalized anti-tumor responses with the capability of producing long-term durable responses or even cures in these men.

The main research goals of my laboratory are: (1) to identify and study the biology of novel cancer selective targets whose enzymatic function can be exploited for therapeutic and diagnostic purposes; (2) to develop methods to target novel agents for activiation by these cancer selective targets while avoiding or minimizing systemic toxicity; (3) to develop novel agents for imaging cancer sites at earliest stages. To accomplish these objectives the lab has originally focused on the development of prodrugs or protoxins that are inactive when given systemically via the blood and only become activated by tumor or tissue specific proteases present within sites of tumor. Using this approach, we are developing therapies targeted for activation by the serine proteases prostate-specific antigen (PSA), human glandular kallikrein 2 (hK2) and fibroblast activation protein (FAP) as well as the membrane carboxypeptidase prostate-specific membrane antigen (PSMA). One such approach developed in the lab consists of a potent bacterial protoxin that we have reengineered to be selectively activated by PSA within the Prostate. This PSA-activated toxin is currently being tested clinically as treatment for men with recurrent prostate cancer following radiation therapy. In a related approach, a novel peptide-cytotoxin prodrug candidate that is activated by PSMA has been identified and is this prodrug candidate is now entering early phase clinical development. In addition, we have also identified a series of potent inhibitors of PSA that are now under study as drug targeting and imaging agents to be used in the treatment and detection of prostate cancer.