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.

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.

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

Dosing/Administration

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 Trial 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 end point was overall survival. The prespecified 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 percent) in the Xtandi arm versus 212 (53.1 percent) 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).