DOUBLE-TARGETED MACROMOLECULAR THERAPEUTICS FOR THE TREATMENT OF PROSTATE CANCER

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ABSTRACT Prostate cancer is the most common lethal cancer diagnosed and second leading cause of cancer death in American men. In 2007, the American Cancer Society estimates that in the USA there will be about 218,000 new cases and about 27,000 men will die of prostate cancer. The purpose of this project is to draw on the advances made in molecular biology, polymer science, and chemotherapy to develop a novel therapeutic modality, which will be potentially more effective than existing therapeutic agents in the treatment of prostate cancer. Clinical data indicate that the therapeutic use of nanosized (5-20 nm) water-soluble polymer-drug conjugates appears to be a novel and successful strategy for cancer treatment. The advantages of polymer- bound drugs (in contrast to low-molecular weight drugs) are: a) active uptake by fluid-phase pinocytosis (non- targeted polymer-bound drug) or receptor-mediated endocytosis (targeted polymer-bound drug), b) increased active accumulation of the drug at the tumor site by targeting, c) increased passive accumulation of the drug at the tumor site due to the enhanced permeability and retention effect, d) long-lasting circulation in the bloodstream, e) decreased non-specific toxicity of the conjugated drug, f) decreased immunogenicity of the targeting moiety, f) immunoprotecting and immunomobilizing activities, and g) potential for the design of double-targeted conjugates. The main aim of the proposed studies is to design new water-soluble polymer ¿ anticancer drug conjugates that are more effective than existing therapeutic regimens in the treatment of androgen-independent prostate cancer. We propose to design and synthesize novel double-targeted macromolecular therapeutics containing a water-soluble N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer backbone, a targeting moiety (monoclonal antibody or targeting peptide, selected by combinatorial approaches) against prostate-specific membrane antigen (PSMA), and a mitochondrial apoptosis inducer, ((E)-4-[3-(1-adamantyl)-4-hydroxyphenyl]- 3-chlorocinnamic acid (3Cl-AHPC)) as a therapeutic drug. We hypothesize that this conjugate will demonstrate a dramatically improved therapeutic index in androgen-independent prostate cancer (AIPC). The superior efficacy of targeted HPMA copolymer ¿ 3Cl-AHPC conjugates is based on their double-targeting capacity, i.e. targeting to prostate cancer cells mediated by the targeting moiety and the inherent mitochondriotropism of the apoptosis inducer (3Cl-AHPC), as mediated by Nur77, an orphan nuclear receptor. In addition, the combination of a targeted HPMA copolymer-bound apoptosis inducer (3Cl-AHPC) with targeted HPMA copolymer-bound docetaxel (the first-line therapeutic agent for metastatic AIPC) is an innovative therapeutic paradigm with the potential to provide tumor cures that cannot be reached by other therapeutic approaches. Criteria will be established for the design of a new, targeted drug delivery system for the treatment of androgen-independent prostate cancer in humans based on the in vitro and in vivo animal data. NARRATIVE The proposal addresses one of the main problems in prostate cancer treatment ¿ the lack of specificity of low molecular weight anticancer drugs. The concept of double-targeted macromolecular therapeutics provides a new paradigm for the design of efficient anticancer drug delivery systems for the treatment of prostate cancer. The active agent will be directed not only to the cancer cell, but into a specific subcellular compartment as well.