ESMO: Pfizer, Astellas' latest Xtandi survival data may shore up prostate cancer lead over J&J

The study showed Xtandi, used alongside the androgen deprivation therapy, slashed the risk of death by 34% compared with the therapy alone. (Pfizer)

Pfizer and Astellas have been in a toe-to-toe race with Johnson & Johnson in prostate cancer, managing to eke out slightly more indications and sales. Now, the pair is trumpeting key overall survival figures for Xtandi that could boost its prospects in men with a hard-to-treat type of the cancer. 

A final analysis of Pfizer and Astellas’ phase 3 ARCHES trial studying Xtandi paired with androgen deprivation (AD) therapy in men with metastatic hormone-sensitive prostate cancer found the med “significantly” prolonged their lives compared with the AD therapy alone, according to results presented at the European Society for Medical Oncology 2021 virtual congress.

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By Year 2, the 574-patient Xtandi arm reported a roughly 86% overall survival rate compared with 82.3% in the 576-person placebo group, according to the presentation. That gap widened by Year 3, with a survival rate of 77.8% in the Xtandi group and nearly 69% for placebo patients. 

By Year 4, the Xtandi group showed a 70.6% overall survival rate compared with just 57% for placebo. The study showed Xtandi, used alongside the AD therapy, slashed the risk of death by 34% compared with the AD therapy alone. 

Median treatment duration was 40.2 months in the Xtandi group, just about 14 months on placebo and nearly 24 months in a group that had crossed over from placebo to Xtandi. About 34.5%, or 397 patients, remained on the treatment at the May 28 cutoff point with a median follow-up of nearly 45 months. 

The data could help Pfizer and Astellas as they gun against J&J’s Erleada and Zytiga in prostate cancer. So far, however, Xtandi has managed to pull in more sales than its competitors. The drug raked in $4.39 billion last year, well above the $760 million Erleada reaped. Meanwhile, sales of Zytiga landed at $2.4 billion, a near 12% dip compared with 2019 amid copycat competition.

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Xtandi was granted an FDA fast track and later approved in metastatic castration-sensitive prostate cancer (mCSPC) by late 2019. In May, the oral treatment also scored a European nod for that indication, which carries a grim median survival of just three to four years, Astellas says. U.S. regulators already approved Xtandi in mCSPC and nonmetastatic CRPC (nmCRPC).

For its part, androgen receptor inhibitor Erleada, J&J's follow-up to aging Zytiga, was also approved in mCSPC in 2019 and in nmCRPC a year before that.

To the researchers, the overall survival readout—a key secondary endpoint from the 1,150-person ARCHES trial—is “a critical benchmark of clinical efficacy, which was immature at the time of primary analysis.” That readout, presented back in early 2019, showed that Xtandi managed to slash the risk of cancer worsening or death by 61% versus AD therapy alone.