Cabozantinib Active against Advanced Prostate Cancer

The investigational drug cabozantinib is showing promise in the treatment of metastatic, hormone-refractory prostate cancer, with particularly notable results among patients with bone metastases. These results were presented at the 2011 annual meeting of the American Society of Clinical Oncology.

Prostate cancer is a hormonally sensitive disease that can be controlled for long periods with androgen deprivation therapy (ADT). When prostate cancer stops responding to this treatment is it referred to as hormone-refractory prostate cancer. Advances have been made in the treatment of hormone-refractory cancer, but challenges remain and new drugs continue to be developed.

Cabozantinib is an investigational drug that targets two proteins—MET and VEGFR2—that play a role in the development and progression of many types of cancer.

To evaluate cabozantinib in the treatment of hormone-refractory, metastatic prostate cancer, researchers conducted a Phase II clinical trial among 171 patients with progressive (worsening) cancer. More than three-quarters of the men had bone metastases.

All patients were initially treated with 12 weeks of cabozantinib. Treatment after 12 weeks depended on how the patients had responded to initial treatment.

  • Among the patients with bone metastases, 76% had partial or complete disappearance of the bone metastases on bone scan. Among patients who had been taking narcotics for bone pain, 67% had a reduction in pain and 56% decreased or stopped their narcotic use.
  • More than two-thirds of patients had some reduction in metastases outside of the bone.
  • Side effects of cabozantinib included fatigue, gastrointestinal symptoms, and high blood pressure.

These results suggest that cabozantinib is active against hormone-refractory prostate cancer, and may be particularly beneficial for patients with bone metastases. Additional studies of the drug are underway; cabozantinib has not yet been approved by the U.S. Food and Drug Administration.

Reference: Hussain M, Smith MR, Sweeney C et al. Cabozantinib (XL184) in metastatic castration-resistant prostate cancer (mCRPC): results from a phase II randomized discontinuation trial. Paper presented at: 2011 Annual Meeting of the American Society of Clinical Oncology; June 3-7, 2011; Chicago, IL. Abstract 4516.

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