Adding niraparib to abiraterone acetate/prednisone (AAP) improves radiographic progression-free survival (rPFS) in patients with BRCA-mutated, metastatic castration-resistant prostate cancer (mCRPC), according to updated results from the phase 3 MAGNITUDE trial.

Niraparib reduced the risk of progression or death by 45% and extended rPFS by more than 8 months, said Eleni Efstathiou MD, PhD, of The University of Texas MD Anderson Cancer Center in Houston, when presenting these results at the 2023 ASCO Genitourinary Cancers Symposium.

The MAGNITUDE trial ( Identifier: NCT03748641) enrolled 423 patients with mCRPC and HRR gene alterations. Patients were randomly assigned to receive niraparib plus AAP or placebo plus AAP. Baseline characteristics were generally well balanced between the arms.

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There were 113 patients in the niraparib arm and 112 in the placebo arm who had BRCA1/2 alterations. At a median follow-up of 26.8 months, the median treatment duration was 17.9 months in the niraparib arm and 15.2 months in the placebo arm.

Among the patients with BRCA mutations, the median rPFS was 19.5 months with niraparib and 10.9 months with placebo (HR, 0.55; 95% CI, 0.39-0.78; P =.0007). The median time to symptomatic progression was not reached in the niraparib arm and was 23.6 months in the placebo arm (HR, 0.54; 95% CI, 0.35-0.85; P =.0071).

The median time to initiation of cytotoxic chemotherapy was not reached with niraparib and was 27.3 months with placebo (HR, 0.56; 95% CI, 0.35-0.90; P =.0152). The median overall survival was 29.3 months in the niraparib arm and 28.6 months in the placebo arm (HR, 0.88; 95% CI, 0.58-1.34; P =.5505).

The safety profile of niraparib plus AAP was consistent with the safety profile in the primary analysis, Dr Efstathiou said.

Disclosures: This research was supported by Janssen Research & Development, LLC. Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.


Efstathiou E, Smith MR, Sandhu S, et al. Niraparib (NIRA) with abiraterone acetate and prednisone (AAP) in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) and homologous recombination repair (HRR) gene alterations: Second interim analysis (IA2) of MAGNITUDE. ASCO GU 2023. February 16-18, 2023. Abstract 170.