"Exelixis Incs cabozantinib experimental drug shrank bone malignancies from prostate cancer in  percent of patients interim results from a midstage trial show.  Of  patients so far evaluated by bone scan  had complete resolution and  had partial shrinkage of metastatic bone lesions which can lead to bone fractures severe pain and eventual death.  The disease remained stable in  other patients or  percent and worsened in three.  The study results were reported on Monday at the American Society of Clinical Oncologys annual meeting.  For the first time cabo is showing dramatic activity against both soft tissue and metastatic bone lesions said Exelixis Chief Executive Officer Michael Morrissey. Men with latestage prostate cancer usually die from bone disease.  After  weeks of treatment  patients were randomly selected to receive either a placebo or cabozantinib. The drug reduced by  percent the risk of disease progression or death.  Excluding patients on placebo the median survival without disease progression was  weeks.  Side effects of cabozantinib included fatigue high blood pressure and hemorrhage.  Morrissey said Exelixis planned to start a Phase  prostate cancer trial in the second half of this year with a combined goal of reducing pain and bone malignancies.  Cabozantinib also known as XL is an oral drug designed to limit blood supply to tumors and to block two segments of a pathway used by cancer cells to grow and spread.  Other Phase  data presented over the weekend showed that treatment with cabozantinib led to significant tumor shrinkage in  percent of patients with metastatic ovarian cancer.  But two ovarian cancer patients died from cabozantinibrelated side effects  one from bowel fistula and one from intestinal perforation.  Exelixis expects to have initial results around midyear from a pivotal trial of the drug as a treatment for thyroid cancer. Our StandardsThe Thomson Reuters Trust Principles. httpthomsonreuters.comenaboutustrustprinciples.html"