Generic name: enzalutamide
Companies: Astellas Pharma; Pfizer
2015 sales: $2.10 billion
2022 sales: $4.71 billion
Current indication: prostate cancer
Eyebrows were raised when Pfizer offered $14 billion to buy Medivation last year to get control of fast-growing prostate cancer drug Xtandi, which was sold by Astellas. With that deal done, Pfizer has a stake in a drug that is growing at an impressive lick despite staunch competition from Johnson & Johnson's incumbent blockbuster Zytiga (abiraterone).
Zytiga outsold Xtandi last year—just barely—with sales above $2.2 billion, but Xtandi has a few advantages that are helping it compete against its rival. Firstly, it is given as a monotherapy, while Zytiga needs to be dosed alongside the steroid prednisone to balance side effects. Generally, doctors like to avoid use of steroids if at all possible. Secondly, patients on Zytiga need regular monitoring for liver enzyme levels, and the FDA required stronger warnings of potential liver toxicity to be added to the drug's label in June.
Those differences are having an impact in the market. Medivation claims that Xtandi has now surpassed Zytiga in market share, helped by earlier use, which means patients are staying on the drug for longer. And in the U.K., cost-effectiveness agency NICE gave its blessing for the use of Xtandi as a prechemotherapy regimen last year but turned down Zytiga. The agency changed its tune this March, agreeing to fund Zytiga as long as J&J delivers some discounts.
Results of the 500-patient Plato trial on the Xtandi-plus-Zytiga combo came in December 2016, and the pair proved no better at keeping cancer at bay than the Zytiga-only regimen did. But Xtandi is predicted to have a healthy lead in the prostate cancer market in 2022. It could also pick up additional approvals in breast and ovarian cancers that will crack open some big new markets for the drug.
It likely won't all be smooth sailing for Xtandi, however. The drug has been facing pricing pressure in the U.S., while health insurer CVS Health banned the drug from its 2017 formulary on cost grounds. It could also face competition from Bayer Healthcare's fast-growing Xofigo and possibly a resurgent Provenge if Valeant can inject some momentum into the troubled prostate cancer vaccine.