强生（JNJ）新一代前列腺癌口服药物Zytiga自2011年4月上市之后，一直统治市场，然而，该药将很快面临首次市场份额冲击。近日，FDA已批准Medivation和安斯泰来的前列腺癌药物Xtandi，用于前列腺癌患者化疗前治疗，剑锋直指强生Zytiga，可以预见，Zytiga霸主地位即将不保。
FDA根据III期PREVAIL研究的总生存期（OS）利益批准了Xtandi，数据显示，与安慰剂相比，Xtandi使放射学恶化或死亡风险降低83%，使死亡风险降低29%，同时也显著延迟了首次化疗时间及首次骨骼相关事件的发生。分析师预计，鉴于这些结果以及随后的标签扩展，Xtandi的患者群体将显著扩张。由于获批用于化疗前治疗，Xtandi的临床用药时间将翻番，化疗前治疗的患者群体将翻3倍。
尽管Xtandi的上市时间比强生Zytiga晚了近一年半时间，然而，Xtandi有其独特优势，即可单独用药，而强生Zytiga需联合强的松（prednisone）用药。因此，Xtandi自上市之初，便已经有能力挑战Zytiga。
Zytiga已收获的化疗前用药适应症，已助推该药在2014年上半年销售额达到10.7亿美元，而Xtandi今年第二季度在美国的销售额已达到1.44亿美元。业界认为，从强劲的市场接纳来看，早在化疗后用药适应症中，Xtandi就已经表现出抗衡Zytiga的能力。
在前列腺癌临床治疗中，Xtandi已被临床医生快速采纳，作为前列腺癌化疗后治疗的首选药物。因此，与Zytiga相比，鉴于Xtandi的单独用药优势及近期获批的化疗前适应症，该药有望颠覆Zytiga的霸主地位。
英文原文：Pre-chemo nod for Medivation's Xtandi sets up showdown with J&J's Zytiga
Johnson & Johnson's ($JNJ) next-gen prostate cancer pill, Zytiga, has been cruising since it hit the market back in April 2011, but now, it may be vulnerable to market share losses for the first time. The FDA has approved Medivation and Astellas' rival, Xtandi, for use in prostate cancer patients before chemo, giving the pill a head-to-head shot at J&J's blockbuster.
U.S. regulators based the new nod on Phase III trial data that showed that Xtandi posted an overall survival benefit, cutting the risk of death by 29% compared with placebo. It also reduced the risk of disease progression and delayed both skeletal problems and the need for chemo, the company said Wednesday.
Thanks to those results--and the subsequent label expansion--Medivation should now see its patient pool widen significantly, Sanford Bernstein analyst Geoffrey Porges told Reuters. "The average duration of treatment should double and the addressable patient population triple in the pre-chemo setting," he said.
And, for the first time since its rollout--nearly a year and a half after J&J's--it'll also be able to set its sights on a face-off with Zytiga. The J&J pill already boasts a pre-chemo indication, which helped it churn out $1.07 billion in first-half 2014 sales.
Xtandi, which netted $143.7 million in second-quarter U.S. sales, has the convenience factor on its side, as it's used solo; patients take Zytiga alongside prednisone. And according to Leerink Partners analyst Howard Liang, the solid uptake the drug has seen in post-chemo patients bodes well for its head-to-head chances, too.
"Strong adoption of Xtandi among oncologists as the preferred agent in the post-chemo setting, in our opinion, speaks to the preference for Xtandi's advantage that goes beyond lack of steroid co-administration and sets up potentially an even stronger launch following pre-chemo approval," he wrote in a recent note to clients.
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