Olaparib combined with abiraterone in HRR-mutated metastatic hormone-sensitive prostate cancer: a single-arm phase II trial.

PURPOSE: Although olaparib plus abiraterone and prednisone has significantly prolonged radiographic progression-free survival (rPFS) in metastatic castration resistant prostate cancer patients (mCRPC), little is known about the effects of this combination therapy on metastatic hormone-sensitive prostate cancer (mHSPC), especially for those with homologous recombination repair (HRR) genes. We conducted a phase II clinical trial to evaluate the efficacy and safety of olaparib plus abiraterone for mHSPC with HRR gene mutations.

METHODS

Thirty patients with mHSPC who had at least one HRR gene mutation were enrolled. Patients were administered Olaparib 300 mg BID plus abiraterone 1000 mg QD and prednisone 5 mg QD. The primary endpoint was 1-year rPFS rate per PCWG3-modified RECIST 1.1 by investigator assessment, and the secondary endpoints included median rPFS, PSA response rate, PSA-PFS, ORR.

RESULTS

A total of 30 patients administered combination therapy with mutations in 7 HRR genes. All the patients had de novo mHSPC. The median follow-up was 19.0 months. The 1-year rPFS rate was 77.7% (95% CI: 63.4-95.3%). All patients achieved PSA50 response. Among the 13 patients who had measurable disease at baseline, the confirmed ORR was 84.6% (n = 11). One patient achieved a complete response, ten patients obtained a partial response, and two had progressive disease. The treatment was well tolerated, with 8(26.6%) patients experienced≥ grade 3 treatment-related adverse events (TRAEs). Common TRAE was anemia (13 patients, 43.3%).

CONCLUSION

In this phase II single-arm study, olaparib plus abiraterone and ADT showed preliminary activity and a manageable safety profile in patients with HRR-mutated mHSPC, but these findings need to be confirmed in larger phase III studies.

TRIAL REGISTRATION: This trial is registered with ClinicalTrials.gov, number NCT05167175.