Pfizer, Astellas rocket toward broader Xtandi use with FDA 'priority' tag

Pfizer and Astellas expect a decision from the FDA on Xtandi's potential new use in Q4. (Pfizer)

Pfizer and Astellas are chasing a new nod for prostate cancer drug Xtandi, and thanks to a new move from the FDA, they might not have to wait that long.

Wednesday, the agency bestowed its “priority review” designation on Xtandi's bid to treat metastatic, hormone-sensitive prostate cancer (mHSPC). With the review speed-up, the partners now expect a decision next quarter.

RELATED: Pfizer, Astellas chase new Xtandi nod with big survival numbers in prostate cancer

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The FDA will base its verdict on data from two phase 3 trials. The first, called Arches, showed that a combination of Xtandi and androgen deprivation therapy (ADT) slashed the risk of cancer worsening or death by 61% versus ADT alone.

In a second, investigator-sponsored study dubbed Enzamet, Xtandi pared down the risk of death by 33% compared with other non-steroidal androgen-fighting drugs. That data debuted at this year’s American Society of Clinical Oncology (ASCO) annual meeting.

“The submission is supported by a strong data package,” Chris Boshoff, M.D., Pfizer’s chief development officer for oncology, said in a statement. Andrew Krivoshik, M.D., Astellas SVP and head of oncology, called the data from the two trials “complementary.”

RELATED: ASCO: Pfizer, Astellas' Xtandi racks up more data for new prostate cancer approval

Right now, Xtandi is cleared in the U.S. only to treat patients with castration-resistant prostate cancer. A go-ahead in the mHSPC group would mean a big new market: The metastatic patient population grows by about 38,000 new patients per year, and those patients tend to stay on therapy the longest, Angela Hwang, president of Pfizer’s biopharmaceuticals group, said on Pfizer’s Q4 conference call earlier this year.

But Pfizer and Astellas aren't the only drugmakers targeting that patient population. The FDA is currently reviewing Johnson & Johnson's Erleada⁠—the follow-up drug to longtime Xtandi rival Zytiga⁠—under the FDA's Real-Time Oncology Review program. Green lights for both meds would mean yet another venue for head-to-head competition.

In the meantime, though, Pfizer and Astellas will have to wait to see what the FDA decides. They’ve also submitted the Arches and Enzamet data to regulators and Europe and Japan, the companies said.

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