# COU-AA-301

Source: https://onco.cc/trials/cou-aa-301/  
OnCo record `cou-aa-301` (Trial). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Proved that prostate cancer which has stopped responding to standard hormone therapy is still driven by androgens, by blocking the enzyme that makes them and adding about four months of life.

## Summary

The premise of castration-resistant prostate cancer used to be that the disease had escaped hormonal control. COU-AA-301 tested the opposite hypothesis, that androgens made outside the testes, in the adrenal glands and the tumour itself, keep driving it, and that blocking CYP17 would work.

It randomised 1,195 men who had already received docetaxel 2:1 to abiraterone acetate 1000 mg daily with prednisone (797) or placebo with prednisone (398). At a median 12.8 months, overall survival was 14.8 against 10.9 months, hazard ratio 0.65 (95 percent confidence interval 0.54 to 0.77, p<0.001). The data were unblinded at the interim analysis because the result exceeded the preplanned stopping criteria. Time to PSA progression was 10.2 against 6.6 months (p<0.001), radiographic progression-free survival 5.6 against 3.6 months (p<0.001) and PSA response 29 against 6 percent (p<0.001).

The side effects follow from the mechanism: blocking CYP17 raises mineralocorticoids, so fluid retention, hypertension and hypokalaemia were more common with abiraterone, which is why it is given with a steroid.

In England NICE TA259 recommends abiraterone with prednisone or prednisolone after one docetaxel-containing regimen, subject to the commercial access arrangement.

## Fields

- Kind: Trial
- Status: positive
- Last checked: 2026-09-25
- Also known as: COU-AA-301; abiraterone after docetaxel
- Registry id: NCT00638690
- Phase: 3
- Setting: Metastatic castration-resistant prostate cancer after docetaxel: prednisone 5 mg twice daily for everyone, with abiraterone acetate 1000 mg daily or placebo, randomised 2:1, with overall survival as the primary endpoint
- Sponsor: Cougar Biotechnology, later Janssen
- Enrolled: 1195
- Result: Median overall survival 14.8 against 10.9 months (hazard ratio 0.65, 95 percent confidence interval 0.54 to 0.77) with abiraterone after docetaxel; PSA response 29 against 6 percent.
- Outcomes: Overall survival (median): Abiraterone acetate with prednisone 14.8 months vs Placebo with prednisone 10.9 months, HR 0.65; Radiographic progression-free survival (median): Abiraterone acetate with prednisone 5.6 months vs Placebo with prednisone 3.6 months
- Replication: AFFIRM found the same in the same setting with enzalutamide (18.4 against 13.6 months); COU-AA-302 moved abiraterone before chemotherapy.

## Sources

- ClinicalTrials.gov NCT00638690: https://clinicaltrials.gov/study/NCT00638690
- COU-AA-301 (New England Journal of Medicine 2011): https://doi.org/10.1056/NEJMoa1014618
- NICE TA259: abiraterone for castration-resistant metastatic prostate cancer previously treated with a docetaxel-containing regimen: https://www.nice.org.uk/guidance/ta259

## Connected records

- cancers: [Metastatic castration-resistant prostate cancer](https://onco.cc/cancers/prostate-mcrpc/), [Prostate cancer](https://onco.cc/cancers/prostate/)
- technologies: [Androgen deprivation & AR pathway inhibitors](https://onco.cc/technologies/androgen-deprivation/)
- targets: [Androgen receptor](https://onco.cc/targets/androgen-receptor/)
- drugs: [Abiraterone acetate](https://onco.cc/drugs/abiraterone/), [Prednisone](https://onco.cc/drugs/prednisone/)
- companies: [Johnson & Johnson](https://onco.cc/companies/johnson-johnson/)
- terms: [Androgen receptor pathway inhibitor (ARPI)](https://onco.cc/terms/arpi/), [Castration-resistant prostate cancer (CRPC)](https://onco.cc/terms/castration-resistance/), [PSA50 / PSA90 response](https://onco.cc/terms/psa50/), [What follows what in castration-resistant prostate cancer](https://onco.cc/terms/prostate-crpc-sequencing/)
- trials: [AFFIRM](https://onco.cc/trials/affirm/), [COU-AA-302](https://onco.cc/trials/cou-aa-302/), [TAX 327](https://onco.cc/trials/tax-327/)

---
JSON: https://onco.cc/api/v1/entities/cou-aa-301.json