General Information

Xtandi (enzalutamide) is an androgen receptor inhibitor.

Xtandi is specifically indicated for the treatment of patients with metastatic castration-resistant prostate cancer who have previously received docetaxel.

Xtandi is supplied as a capsule for oral administration. The recommended dose of Xtandi is 160 mg (four 40 mg capsules) administered orally once daily. Xtandi can be taken with or without food. The capsules should be swallowed whole.

Clinical Results

FDA Approval
The FDA approval of Xtandi was based on a randomized, placebo-controlled, multicenter trial in 1,199 subjects. The subjects were randomized to receive either Xtandi orally at a dose of 160 mg once daily (n=800) or placebo orally once daily (n=399). All subjects continued androgen deprivation therapy. The primary endpoint was overall survival. The pre-specified interim analysis at the time of 520 events showed a statistically significant improvement in overall survival in subjects on the Xtandi arm compared to those on the placebo arm. The number of deaths was 308 (38.5%) in the Xtandi arm versus 212 (53.1%) in the placebo arm. The median survival was 18.4 months in the Xtandi arm versus 13.6 months in the placebo arm (p< 0.0001).

Side Effects

Adverse events associated with the use of Xtandi may include, but are not limited to, the following:

• asthenia/fatigue
• back pain
• diarrhea
• arthralgia
• hot flush
• peripheral edema
• musculoskeletal pain
• headache
• upper respiratory infection
muscular weakness
• dizziness
• insomnia
• lower respiratory infection
• spinal cord compression and cauda equina syndrome
• hematuria
• paresthesia
• anxiety
• hypertension

Mechanism of Action

Xtandi (enzalutamide) is an androgen receptor inhibitor that acts on different steps in the androgen receptor signaling pathway. Enzalutamide has been shown to competitively inhibit androgen binding to androgen receptors and inhibit androgen receptor nuclear translocation and interaction with DNA.

Literature References

Scher HI, Fizazi K, Saad F, Taplin ME, Sternberg CN, Miller MD, de Wit R, Mulders P, Chi KN, Shore ND, Armstrong AJ, Flaig TW, Fléchon A, Mainwaring P, Fleming M, Hainsworth JD, Hirmand M, Selby B, Seely L, de Bono JS; the AFFIRM Investigators Increased Survival with Enzalutamide in Prostate Cancer after Chemotherapy. New England Journal of Medicine 2012 Aug 15

Additional Information

For additional information regarding Xtandi or prostate cancer, please visit the Medivation web page.