How Does Xtandi Treat Advanced Prostate Cancer?

In up to 40 percent of men who are diagnosed with prostate cancer and undergo therapy, the disease spreads (metastasizes) and develops into advanced prostate cancer. For those who have tried and failed to respond to androgen-deprivation therapy (also known as failure to respond to castration-resistant prostate cancer), there are other treatment options, including Xtandi (enzalutamide). How does Xtandi treat advanced prostate cancer?

What is Xtandi?

Xtandi is an FDA-approved drug for the treatment of men with metastatic castration-resistant prostate cancer. It is in a drug class known as androgen receptor inhibitors, which means it blocks the androgen receptor signaling pathway in tumor cells. It does this in several ways. For example, preclinical research has shown that the drug can inhibit androgens from attaching to androgen receptors, block androgen receptor nuclear translocation, and interfere with interactions between androgen receptors with DNA.

How does Xtandi work?

Testosterone is known to stimulate the growth of prostate cancer, which is why one treatment approach is to block the formation of testosterone. This is the goal of hormone therapy for prostate cancer, aka androgen deprivation therapy. For some men, however, this therapeutic approach fails to stop the progression of the disease.

When that occurs, one option is Xtandi, which works by interfering with the connection between androgens and their receptors. The interaction of androgens and androgen receptors can cause prostate cancer cells to grow. Use of Xtandi can reduce how often androgens connect with receptors, which in turn can help slow the growth and spread of prostate cancer.

In a recent study, scientists compared the effects of enalutamide and bicalutamide (Casodex), an anti-androgen drug that is used to treat advanced (metastasized) prostate cancer. Typically bicalutamide is used along with another type of drug—a luteinizing hormone-releasing hormone agonist—but it was not in this study. A total of 396 men whose cancer continued to progress after failing androgen-deprivation therapy were treated with either enzalutamide or bicalutamide. At the end of the study:

Men who had received enzalutamide had a 76 percent reduced risk of prostate cancer progression or death when compared with men who had taken bicalutamide.

Median time from start of therapy to progression of prostate cancer among men who survived was 19.4 months for men who took enzalutamide compared with 5.7 months for men who received bicalutamide

Reference

Penson D et al. Enzalutamide versus bicalutamide in castration-resistance prostate cancer: the STRIVE Trial. Journal of Clinical Oncology 2016 Jan 25


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