Johnson & Johnson: Zytiga gains expanded prostate cancer indication in the US.
Zytiga’s indication expansion for the treatment of pre-chemotherapy castration-resistant metastatic prostate cancer significantly increases its commercial potential. However, potential competition from Xtandi may restrict sales.
On December 10, the FDA approved Zytiga to treat men with metastatic castration-resistant prostate cancer (mCRPC) prior to receiving chemotherapy. The indication expansion was based on the results of the Phase III COU-AA-302 study.
The COU-AA-302 study included 1,088 men with mCRPC that had not received prior chemotherapy treatment and had failed androgen deprivation therapy. The patients were randomized 1:1 to receive Zytiga plus prednisone or placebo plus prednisone. An Independent Data Monitoring Committee unblinded the study after a planned interim analysis found a statistically significant improvement in radiographic progression-free survival for the patients in the Zytiga arm. There was also an improvement in median overall survival for patients receiving Zytiga of 35.3 months compared with 30.1 months for those receiving placebo.
Zytiga is a small molecule oral irreversible inhibitor of the CYP17 enzyme which catalyzes the hydroxylation of intermediates involved in testosterone synthesis. In 2011, Zytiga was approved for the treatment of mCRPC patients who had received prior treatment with docetaxel. Since Zytiga’s approval in 2011 it has been used to treat more than 40,000 men worldwide. Zytiga was already being used extensively off-label in the pre-chemotherapy setting but it will be used to a greater extent now that the FDA had added this indication to its label.
Zytiga is on course to generate sales of $500m dollars in the US in 2012. There are an estimated 35,000 new cases of metastatic prostate cancer each year and this indication expansion will significantly increase Zytiga’s sales. However, Johnson & Johnson’s drug is likely to face competition in the pre-chemotherapy setting from Xtandi (enzalutamide; Medivation/Astellas). The results of the Phase III PREVAIL study, which is investigating Xtandi in this setting, are anticipated in 2014. While Zytiga has first-mover advantage, Xtandi may present significant competition in the mCRPC setting if the PREVAIL results are positive.