An investigational drug has been shown to slow the progression of prostate cancer (PCa) and may increase survival among patients with minimally symptomatic metastatic disease.

An oral immunomodulatory, antiangiogenic, and antimetastatic agent, tasquinimod appears to affect the function of myeloid-derived suppressor cells, which are found in increased numbers in cancer patients. The drug’s mechanism of action is not fully understood, however.

Tasquinimod had already demonstrated an ability to delay progression of metastatic castration-resistant prostate cancer (mCRPC) in a randomized, placebo-controlled phase 2 trial funded by developer Active Biotech and reported in Journal of Clinical Oncology in October 2011. Now, Andrew J. Armstrong, MD, ScM, of the Duke Cancer Institute at Duke University Medical Center in Durham, N.C., and fellow investigators are sharing data on long-term survival among those patients, publishing their findings in Clinical Cancer Research.

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In the study, 134 men with mCRPC were randomized to tasquinimod therapy. Of the 67 men randomized to placebo, 41 crossed over to tasquinimod.  A total of 136 participants had bone metastases.

During a median follow-up of 37 months, 111 deaths occurred. Median overall survival was 33.4 months for tasquinimod versus 30.4 months for placebo overall, and 34.2 months with tasquinimod versus 27.1 months with placebo among men with bone metastases. Time to symptomatic progression also was improved with tasquinimod, particularly among those with bone metastases: Overall, men taking the drug experienced no cancer progression for 7.6 months, compared with 3.3 months for placebo. Men with bone metastasis remained progression-free for 8.8 months with tasquinomod, compared with 3.4 months with placebo.

Side effects, which included gastrointestinal issues, muscle and joint pains, and fatigue, tended to be mild.

Dr. Armstrong and colleagues also evaluated biomarkers. Their analyses suggested that tasquinimod had a favorable impact on bone alkaline phosphatase and lactate dehydrogenase over time. Baseline levels of thrombospondin-1 less than the median were predictive of treatment benefit. PSA level, PSA doubling time, and the presence of anemia also appeared to be important prognostic factors.

Tasquinimod is now being evaluated in an international phase 3 trial of men with mCRPC.