First, findings from preclinical studies showed that treatment with a novel oral agent, PLX3397, a selective kinase inhibitor that down-modulates macrophages, microglia, osteoclasts and mast cells, re-programmed the tumor microenvironment, supporting further development of this single agent treatment for certain cancers and malignancies such as prostate cancer. Is scientific findings was presented during the AACR-NCI- EORTC International Conference on Molecular Targets and Cancer Therapeutics, taking place November 12-16, 2011 in the Moscone Center West, San Francisco, CA.

?We have generated a significant set of preclinical data supporting the advancement of PLX3397 as a potential treatment for cancers in which the tumor microenvironment plays an essential role. The new data underscores our plan to explore the utility of PLX3397 as a single agent in another malignancy?prostate cancer,? noted Gideon E. Bollag, Ph.D., senior vice president of Plexxikon.

Targeting macrophages and osteoclasts
New scientific findings were presented for Plexxikon?s novel agent, PLX3397, an oral drug candidate targeting macrophages and osteoclasts. These cells play an important role in the tumor microenvironment, particularly in enabling the metastases of cancer to bone which can result in significant pain and disability. PLX3397 was shown to alter the tumor microenvironment and even re-program certain immune cells involved in killing cancer cells. The findings showed significant tumor growth inhibition, reduction in cancer bone pain and prevention of pathologic bone remodeling in preclinical studies of prostate cancer, conducted by collaborators led by Dr. Pat Mantyh at the University of Arizona College of Medicine, Tucson, AZ. Furthermore, findings indicated an increased tumor cell death and decreased tumor burden by decreasing macrophage and increasing cytotoxic T-cell infiltration in preclinical studies of malignant mesothelioma, conducted by collaborators led by Dr. Lisa Coussens at the University of California, San Francisco, CA.

PLX3397 is currently in a Phase II study in Hodgkin lymphoma. Additional Phase II studies are planned in a number of other cancers, including glioblastoma, acute myelogenous leukemia, metastatic breast cancer and prostate cancer.

For more information:
– Safety Study of PLX108-01 in Patients With Solid Tumors (NCT01004861)
– Safety and Efficacy Study of PLX3397 in Adults With Relapsed or Refractory Hodgkin Lymphoma (NCT01217229)
– A Phase 2 Study of PLX3397 in Patients With Recurrent Glioblastoma (NCT01349036)
– Phase 1/2 Safety and Efficacy of PLX3397 in Adults With Relapsed or Refractory Acute Myeloid Leukemia (AML)(NCT01349049)

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