ASCO 2025: ARCHES and Australian-led ENZAMET prostate cancer trials to present XTANDI® (enzalutamide) data

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New data, to be presented at the American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago, USA, reveal longer-term follow-up results from an open-label extension of Astellas’ Phase 3 ARCHES study. Also being presented at ASCO are updated results from the Australian-led ENZAMET trial, highlighting long-term outcomes with XTANDI® (enzalutamide) in metastatic hormone-sensitive prostate cancer (mHSPC).

The Phase 3 ARCHES results demonstrate survival benefits across multiple patient subgroups with mHSPC, showing a 30% reduction in the risk of death over five years with enzalutamide plus androgen deprivation therapy (ADT), compared to placebo plus ADT.

Historically, the likelihood of survival at five years for men with mHSPC was low. However, advancements in initial treatment intensification, particularly with the use of enzalutamide, have improved outcomes.

In the five-year follow-up of the global ARCHES trial, two-thirds of men with this condition were found to be surviving at the five-year mark. This represents a 13% absolute and 30% relative improvement in survival compared to standard hormonal therapy alone. Notably, these benefits were observed in both high and low disease burden patients, offering clear and meaningful advantages.

Naseem Ali, Medical Affairs Lead, XTANDI, Astellas Australia, said: “Prostate cancer is currently the most diagnosed cancer in Australia and continues to be a major health burden, but these findings signal a meaningful step forward in improving outcomes for men facing the disease.”

“Clinical studies have demonstrated survival benefits of XTANDI in some men with advanced prostate cancer. The growing body of evidence continues to inform the use of enzalutamide in advanced prostate cancer, supporting its role in improving outcomes for some patients. This includes evidence of sustained treatment effects over time and indications of a meaningful impact on aspects of quality of life for some men living with the disease.”

In patients with high-volume disease (HR: 0.70; 95% CI: 0.56-0.88), a 36-month improvement in median survival was observed. Consistently improved survival outcomes were also seen across several clinically relevant subgroups, including patients with low-volume disease (HR: 0.71; 95% CI: 0.49-1.05), those who had previously received docetaxel therapy (HR: 0.67; 95% CI: 0.43-1.05), and those without prior docetaxel treatment (HR:0.71; 95% CI: 0.57-0.88). Safety data from the five-year follow-up aligned with prior ARCHES analyses, with no new safety signals identified.

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Australia-led ENZAMET trial highlights long-term patient outcomes.

In addition to five-year data from the follow-up ARCHES study, eight-year results from the ENZAMET study will also be presented at ASCO. ENZAMET is an international Phase 3, investigator-initiated trial led by the Australian and New Zealand Urogenital and Prostate Cancer Trials Group (ANZUP) and sponsored by the University of Sydney, comparing enzalutamide to non-steroidal anti-androgens (NSAAs) – both combined with testosterone suppression, with or without docetaxel – in patients with mHSPC4. The study demonstrates that upfront use of XTANDI® improves long-term survival, increasing the proportion of patients alive at eight years from 40% to 50%, compared to standard care with older anti-androgens. The median overall survival after 98 months in ENZAMET was eight years for those on XTANDI® compared to 5.8 years for those on the comparison arm.

Professor Christopher Sweeney, Director of the South Australian ImmunoGENomics Cancer Institute at the University of Adelaide, and Professor Ian Davis, Professor of Medicine at Monash University and Head of Eastern Health Clinical School, are two key leaders in the ENZAMET study. Professor Davis also serves as Chair of ANZUP.

Together, these two internationally recognised Australian clinicians have played pivotal roles in advancing the treatment landscape for men with mHSPC, contributing clinical insight to one of the most significant prostate cancer trials of the last decade.

“The ANZUP-led ENZAMET trial was the first to show that survival could be improved by the addition of enzalutamide to testosterone suppression for people with metastatic hormone-sensitive prostate cancer. Now we can show that this benefit persists out to more than eight years,” said Professor Davis.

“People with mHSPC have better outcomes if the PSA test becomes undetectable with treatment. ENZAMET has also shown that this is more likely to happen if people are treated with enzalutamide,” Professor Davis explains.

“This means, in 2025, we can now counsel people that they have a 50% chance that they’ll be alive at eight years with the new therapies that we have for metastatic hormone-sensitive prostate cancer, compared to 40% who received older types of treatment,” added Professor Sweeney.

With a median follow-up of 98 months, patients with mHSPC who were treated with XTANDI plus testosterone suppression with or without docetaxel showed an improvement in overall survival (OS) compared to those treated with NSAA plus testosterone suppression with or without docetaxel. The median OS in the XTANDI group (HR: 0.73; 95% CI, 0.63-0.86) was 8.0 years versus 5.8 years in the NSAA group. OS at 96 months was 50% with XTANDI versus 40% for NSAA; progression-free survival (PFS) also favoured XTANDI over NSAA (HR: 0.49; 95% CI, 0.42-0.57).

In total, prostate cancer accounted for 468 of all 622 deaths, however, this was less frequent among those assigned XTANDI than NSAA (207 versus 261). Deaths due to other causes accounted for a total of 154 deaths and were similarly frequent among those assigned XTANDI versus NSAA (78 vs 76).

The results from both the Phase 3 ARCHES and ENZAMET studies will be submitted for publication in a peer-reviewed journal shortly.


Source: ANZUP

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