US prostate cancer patients may soon be able to get access to Xtandi (enzalutamide) earlier in the treatment pathway, as its manufacturers have handed regulators a supplemental New Drug Application seeking to widen the drug's scope.

Astellas and Medivation said they are looking for approval from the US Food and Drug Administration to market Xtandi for patients with metastatic castration-resistant prostate cancer (mCRPC) who have not yet received prior treatment with chemotherapy.

A green light from the FDA would mean that patients could get treatment with the drug at a much earlier stage, as its current approval is only for use in those who have previously received docetaxel chemotherapy.

The application is based on results from the Phase III PREVAIL trial, which assessed Xtandi and a placebo in more than 1,700 chemotherapy-naïve mCRPC patients.

Data showed that the drug was linked with a statistically significant overall survival benefit compared with placebo, reducing the risk of death by 29%.

The drug was also shown to significantly cut the risk of radiographic progression or death by 81% compared with placebo treatment and, also importantly, caused a 17-month delay in the time to the start of chemotherapy. 

Also, in another show of its potential benefit, almost four out of five patients taking Xtandi experienced a decline in PSA of 50% or more compared to less than 4% in the placebo group. 

An application to extend the drug's use to pre-chemo patients will also be submitted to European regulators later this year, the firms said.