Astellas and Medivation are trying to extend the uses of their prostate cancer drug Xtandi in the US to include newly-diagnosed patients who have not been treated with chemotherapy before.
Xtandi (enzalutamide) was first approved in the US in 2012 as a treatment for late-stage, castration-resistant prostate cancer (CRPC) who have previously received therapy with docetaxel, and chalked up an impressive $445m in sales in its first full-year on the market, helped by approval in Europe mid-year.
The new filing in treatment-naïve patients is based on the results of the PREVAIL trial, which enrolled more than 1,700 men CRPC, whose symptoms had progressed following treatment with androgen blocker drugs, such as AbbVie’s Lupron (leuprolide acetate) and AstraZeneca’s Casodex (bicalutamide).
Interim results from that study were reported last November when – based on a favourable risk:benefit profile and 29 per cent reduction in the risk of death versus placebo – the independent data monitoring committee recommended that it be stopped early and all patients offered Xtandi.
Astellas and Medivation say that the study is the first to demonstrate statistically significant reductions in both risk of death and risk of radiographic progression or death in pre-chemo metastatic CRPC patients. The data is due to be filed in Europe later this year.
If approved, that profile bodes well for Xtandi as it competes in the marketplace against Johnson & Johnson’s CRPC therapy Zytiga (abiraterone acetate), which reached the market a few months earlier and has grown quickly to reach $1.7bn in turnover last year.
Zytiga was approved for use in chemotherapy-naïve patients last year, but was already reported to have been extensively used off-label in this setting in 2012.
Medivation has previously predicted that – assuming the treatment-naïve indication is added to Xtandi’s label sometime in the third-quarter of 2014 – full-year sales of the drug in the US could top $500m, up from $392m in 2013.
Medivation shares Xtandi sales and profits with Astellas in the US, while the latter books all revenue from the product outside the US and pays Medivation royalties on sales.
Meanwhile, Astellas and Daiichi Sankyo have created a compound library sharing partnership in a bid to boost their searches for innovative new drugs. The two Japanese companies will share around 400,000 compounds for use in high-throughput screening (HTS) programmes over the course of the three-year agreement.