Xtandi (enzalutamide) and Zytiga (abiraterone acetate) are both drugs that are used in the treatment of prostate cancer. Results from various analyses indicate that Xtandi is more effective than Zytiga in patients with castration-resistant prostate cancer that has spread or metastasized, although it’s more commonly associated with fatigue.
| Xtandi (enzalutamide) | Zytiga (abiraterone acetate) | |
| Company | Astella Pharma | Janssen Biotech |
| Approval date | First approved in the US in 2012 | First approved in the US in 2011 |
| Indication/usage |
For the treatment of:
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For the treatment of:
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| Dosage form | Capsules (40mg) and tablets (80mg, 40mg) | Tablets (uncoated 250mg, film-coated 500mg) |
| Generic available | Generic capsules only available | Generics available |
| Administration | Orally | Orally |
| Dosing schedule |
Capsules and tablets should be swallowed whole. |
Tablets must be swallowed whole and taken on an empty stomach. |
| Drug type | Small molecule | Small molecule |
| Mechanism of action | Androgen receptor inhibitor | CYP17 inhibitor |
| Side effects / adverse effects |
The most common adverse reactions (≥ 10%) are:
Results from a systematic review and meta-analysis showed that Xtandi was associated with a significantly elevated risk of side effects (730 patients, odds ratio 0.35, 95% CI 0.13-0.92, p=0.03), especially fatigue (2477 patients, odds ratio 0.46, 95% CI 0.34-0.63, p<0.00001), compared with Zytiga in patients with metastatic castration-resistant prostate cancer. However, a separate systematic review and meta-analysis comparing Xtandi with Zytiga in patients with metastatic castration-resistant prostate cancer did not find a significant difference between the two groups in terms of overall adverse events (730 patients, relative risk 0.42, 95% CI 0.14-1.31, p=0.14), but Xtandi was associated with a higher risk of fatigue (2555 patients, relative risk 0.45, 95% CI 0.24-0.85, p=0.01). |
The most common adverse reactions (≥ 10%) are:
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| Efficacy |
Results from three systematic reviews and meta-analyses show that Xtandi is more effective than Ztygia for treating metastatic castration-resistant prostate cancer.
In two reviews prostate-specific antigen responses were higher for people receiving Xtandi than Zytiga (790 patients, odds ratio 0.47, 95% CI 0.29-0.77, p=0.003 and 867 patients, risk ratio 0.69, 95% CI 0.61-0.79, p<0.00001). In a third review, Xtandi was more effective than Zytiga at improving radiographic progression-free survival (hazard ratio=0.516, 95% CI 0.438-0.608) and time to prostate-specific antigen progression (hazard ratio 0.365, 95% CI 0.303-0.441), but not overall survival (p=0.21), although more work was noted to be needed to confirm these findings.Other studies have found Xtandi to be associated with an overall survival benefit compared with Zytiga in patients with metastatic castration-resistant prostate cancer, especially in older patients with more comorbidities who are not candidates for docetaxel (median overall survival 18.9 months vs 13.6 months, respectively (p<0.001). |
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| Drug interactions |
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| Warnings and precautions |
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| Special patient populations | Do not use in patients with existing severe hepatic impairment (Child-Pugh Class) |