# ARMOR3-SV

Source: https://onco.cc/trials/armor3-sv/  
OnCo record `armor3-sv` (Trial). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The only trial ever to pick men for prostate cancer treatment by a splice variant of the androgen receptor. It could not recruit, because the men who qualified were too ill to stay in it.

## Summary

AR-V7 is a splice variant of the androgen receptor that lacks the ligand-binding domain and is constitutively active, so abiraterone and enzalutamide, which act on that domain or on the hormones feeding it, should not work against it. Galeterone degrades androgen receptor protein, including AR-V7, so it should. ARMOR3-SV was the trial designed to prove it.

Of 953 men prescreened, 323 (34 percent) had detectable circulating tumour cells and 73 of the 953 had AR-V7 messenger RNA, a prevalence of 8 percent (95 percent confidence interval 6 to 10).

AR-V7 positivity marked out advanced, aggressive disease: higher PSA (p<0.001), more bone metastases (p<0.001), more previous docetaxel for hormone-sensitive disease (p<0.001), more previous first-generation androgen deprivation (p<0.001) and a shorter time from diagnosis to enrolment (p<0.001).

Of the 73 eligible men, 38 were randomised, 19 to galeterone and 19 to enzalutamide; 35 dropped out before randomisation. Because so many radiographic progression-free survival events were censored, the data monitoring committee recommended closure on interim evidence that the primary endpoint would not be met. PSA50 responses were 2 of 16 (13 percent) with galeterone and 8 of 19 (42 percent) with enzalutamide, difference -0.278 (95 percent confidence interval -0.490 to 0.097).

Development of galeterone stopped. The trial is a lesson about biomarker-selected trials in a disease that moves fast: if the biomarker marks men who are about to deteriorate, the trial will run out of patients before it runs out of endpoints.

## Fields

- Kind: Trial
- Status: negative
- Last checked: 2026-09-25
- Also known as: ARMOR3-SV; galeterone against enzalutamide in AR-V7 positive disease
- Registry id: NCT02438007
- Phase: 3
- Setting: Metastatic castration-resistant prostate cancer with AR-V7 messenger RNA detectable in circulating tumour cells, in men naive to enzalutamide, abiraterone and chemotherapy: galeterone against enzalutamide, open-label, with radiographic progression-free survival as the primary endpoint
- Sponsor: Tokai Pharmaceuticals
- Enrolled: 38
- Result: Closed early after 38 of a planned 148 men were randomised; AR-V7 prevalence 8 percent (95 percent confidence interval 6 to 10) among 953 prescreened men. PSA50 response 13 percent with galeterone against 42 percent with enzalutamide. Galeterone development stopped.
- Outcomes: AR-V7 prevalence in first-line metastatic castration-resistant prostate cancer: Men prescreened 8%; PSA50 response: Galeterone 13% vs Enzalutamide 42%

## Sources

- ClinicalTrials.gov NCT02438007: https://clinicaltrials.gov/study/NCT02438007
- ARMOR3-SV (European Urology 2019): https://doi.org/10.1016/j.eururo.2019.08.034

## Connected records

- cancers: [Metastatic castration-resistant prostate cancer](https://onco.cc/cancers/prostate-mcrpc/), [Prostate cancer](https://onco.cc/cancers/prostate/)
- targets: [Androgen receptor](https://onco.cc/targets/androgen-receptor/), [CYP17A1 (17-alpha-hydroxylase/17,20-lyase)](https://onco.cc/targets/cyp17a1/)
- drugs: [Enzalutamide](https://onco.cc/drugs/enzalutamide/), [Galeterone](https://onco.cc/drugs/galeterone/)
- terms: [Androgen receptor pathway inhibitor (ARPI)](https://onco.cc/terms/arpi/), [AR-V7 splice variant](https://onco.cc/terms/ar-v7/), [Castration-resistant prostate cancer (CRPC)](https://onco.cc/terms/castration-resistance/), [Prostate cancer programmes that failed, and what each failure taught](https://onco.cc/terms/prostate-failed-programmes/), [PSA50 / PSA90 response](https://onco.cc/terms/psa50/)
- trials: [AFFIRM](https://onco.cc/trials/affirm/), [PREVAIL](https://onco.cc/trials/prevail/)

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