Background: Castration-resistant prostate cancer (CRPC) refers to patients who no longer respond to surgical or medical castration. Standard treatment options are limited. Objective: To review the concepts and rationale behind targeted agents currently in late-stage clinical testing for patients with CRPC. Methods: Novel targeted therapies in clinical trials were identified from registries. The Medline database was searched for all relevant reports published from 1996 to October 2009. Bibliographies of the retrieved articles and major international meeting abstracts were hand-searched to identify additional studies. Results: Advances in our understanding of the molecular mechanisms underlying prostate cancer (PCa) progression have translated into a variety of treatment approaches. Agents targeting androgen receptor activation and local steroidogenesis, angiogenesis, immunotherapy, apoptosis, chaperone proteins, the insulin-like growth factor (IGF) pathway, RANK ligand, endothelin receptors, and the Src family kinases are entering or have recently completed accrual to phase III trials for patients with CRPC. Conclusions: There has been an increase in the understanding of the mechanisms of progression of CRPC. A number of new agents targeting mechanisms of PCa progression with early promising results are in clinical trials and have the potential to provide novel treatment options for CRPC in the near future.

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