Background

Effective therapies for pts with treatment-refractory mCRPC are an important unmet medical need. Niraparib is a highly selective poly ADP-ribose polymerase (PARP) inhibitor of PARP-1 and PARP-2 DNA-repair polymerases.

Methods

GALAHAD is an ongoing open-label phase II study assessing niraparib (300 mg daily) in pts with mCRPC and DRD with disease progression on taxane and androgen receptor-targeted therapy. DRD status was evaluated by a plasma or tissue-based test and defined as having biallelic alterations in BRCA1/2 (BRCA), ATM, FANCA, PALB2, CHEK2, BRIP1, or HDAC2. Primary endpoint was objective response rate (ORR) by RECIST 1.1 with no evidence of bone progression as per the PCWG3 criteria. Composite response rate (CRR) was defined as ORR, conversion of circulating tumor cells to < 5/7.5 mL blood, or ≥ 50% decline in prostate specific antigen.

Results

As of 23 May 2019, 165 pts were enrolled, of whom 81 had biallelic DRD (46 BRCA and 35 non-BRCA) and had a minimum of 16 weeks of follow up. 51/81 had measurable disease at baseline (29 BRCA and 22 non-BRCA); 47% of pts had visceral metastases. Median follow-up in BRCA and non-BRCA was 7.3 and 6.4 mo, respectively. In BRCA, ORR was 41% and CRR was 63% (table); median duration of objective response was 5.5 mo (range: 3.5–9.2). 7/12 BRCA responses were ongoing. Median rPFS and OS in BRCA were 8.2 and 12.6 mo, respectively. In non-BRCA, objective response was noted in 2/22 pts (both had FANCA) and CRR was 17%; durations of objective response were 3.8 and 6.5 mo, respectively. Grade 3/4 treatment-emergent adverse events were mostly hematologic—anemia (29%), thrombocytopenia (15%) and neutropenia (7%)—and managed with dose interruption or modification.Table:

LBA50

Conclusions

Niraparib demonstrates clinical activity in pts with treatment-refractory mCRPC with durable responses particularly in biallelic BRCA mutation carriers.

Clinical trial identification

NCT02854436.

Editorial acknowledgement

Writing assistance was provided by Ramji Narayanan of SIRO Clinpharm Pvt Ltd and funded by Janssen Global Services, LLC.

Legal entity responsible for the study

Janssen Research & Development, LLC.

Funding

Janssen Research & Development, LLC.

Disclosure

S.K. Sandhu: Honoraria (self), Advisory / Consultancy: Amgen; Honoraria (self), Speaker Bureau / Expert testimony: Bristol-Myers Squibb; Honoraria (self), Speaker Bureau / Expert testimony: Merck. W.K. Kelly: Honoraria (self), Advisory / Consultancy, Research grant / Funding (institution): Sanofi; Research grant / Funding (institution): Janssen; Research grant / Funding (institution): Novartis. H.I. Scher: Leadership role, Travel / Accommodation / Expenses, Shareholder / Stockholder / Stock options: Asterias Biotherapeutics; Advisory / Consultancy: Ambry Genetics Corporation; Advisory / Consultancy: Konica Minolta,Inc; Advisory / Consultancy: Janssen Biotech, Inc; Advisory / Consultancy, Research grant / Funding (institution): Janssen Research & Development; Advisory / Consultancy, Travel / Accommodation / Expenses: OncLive Insights; Advisory / Consultancy: Physician Education Resource; Advisory / Consultancy, Travel / Accommodation / Expenses: Sanofi; Advisory / Consultancy, Travel / Accommodation / Expenses: WIRB-Copernicus Group; Research grant / Funding (institution): Illumina ; Research grant / Funding (institution): Innocrin Pharma; Travel / Accommodation / Expenses: Physician Education Resource. E. Efstathiou: Honoraria (self), Advisory / Consultancy, Speaker Bureau / Expert testimony, Research grant / Funding (institution): Janssen-Cilag; Honoraria (self), Research grant / Funding (institution): Sanofi; Honoraria (self), Advisory / Consultancy: Takeda; Advisory / Consultancy, Research grant / Funding (institution): Astellas Pharma; Advisory / Consultancy: AstraZeneca; Advisory / Consultancy: Bayer; Advisory / Consultancy: Innocrin Pharma; Advisory / Consultancy: MSD; Advisory / Consultancy: Tolmar. P.N. Lara: Honoraria (self), Advisory / Consultancy: Pfizer; Advisory / Consultancy: AbbVie; Advisory / Consultancy: AstraZeneca; Advisory / Consultancy: Bayer; Advisory / Consultancy: Bristol-Myers Squibb; Advisory / Consultancy: CellMax Life; Advisory / Consultancy: Exelixis; Advisory / Consultancy: Foundation Medicine; Advisory / Consultancy: Genentech/Roche; Advisory / Consultancy: Janssen; Advisory / Consultancy, Research grant / Funding (institution): Merck; Advisory / Consultancy: Nektar; Advisory / Consultancy: Turnstone Bio; Research grant / Funding (institution): Aragon Pharmaceuticals; Research grant / Funding (institution): Genentech ; Research grant / Funding (institution): GlaxoSmithKline ; Research grant / Funding (institution): Heat Biologics; Research grant / Funding (institution): Incyte ; Research grant / Funding (institution): Janssen Biotech; Research grant / Funding (institution): Millennium, Pharmacyclics, Polaris,TRACON Pharma . E.Y. Yu: Advisory / Consultancy: Amgen; AstraZeneca; Bayer; Churchill Pharmaceuticals; EMD Serono; Incyte; Janssen; Merck; QED; Tolmar; Research grant / Funding (institution): Agensys; Astellas Pharma; Bayer; Dendreon; Genentech/Roche; Merck; Seattle Genetics. D.J. George: Honoraria (self): Bayer; Exelixis; Sanofi; Advisory / Consultancy: Astellas Pharma; Bayer; Bristol-Myers Squibb; Exelixis; Genentech; Innocrin Pharma; Janssen; Merck Sharp & Dohme; Myovant Sciences; Pfizer; Sanofi; Speaker Bureau / Expert testimony: Bayer; Exelixis; Sanofi; Research grant / Funding (institution): Acerta Pharma ; Astellas Pharma ; Bayer ; Bristol-Myers Squibb ; Dendreon ; Exelixis ; Innocrin Pharma ; Janssen Oncology ; Novartis ; Pfizer ; Travel / Accommodation / Expenses: Bayer; Exelixis; Merck; Pfizer; Sanofi. K.N. Chi: Honoraria (self): Astellas Pharma; Bayer; Janssen; Sanofi; Advisory / Consultancy: Amgen; Astellas Pharma; Bayer; ESSA; Janssen; Lilly/ImClone; Sanofi; Research grant / Funding (institution): Astellas Pharma ; Bayer ; Bristol-Myers Squibb ; Janssen ; Lilly/ImClone ; Merck ; Roche ; Sanofi ; Tokai Pharmaceuticals . F. Saad: Honoraria (self): Astellas Pharma; AstraZeneca; Bayer; Janssen Oncology; Sanofi; Advisory / Consultancy: Astellas Pharma; AstraZeneca/MedImmune; Bayer; Janssen Oncology; Sanofi; Research grant / Funding (institution): Astellas Pharma ; AstraZeneca ; Bayer ; Janssen Oncology ; Sanofi . J. Summa: Shareholder / Stockholder / Stock options, Full / Part-time employment: Janssen. J.M. Freedman: Shareholder / Stockholder / Stock options, Full / Part-time employment: Janssen. G.E. Mason: Shareholder / Stockholder / Stock options, Full / Part-time employment: Janssen. E. Zhu: Full / Part-time employment: Janssen. D. Ricci: Shareholder / Stockholder / Stock options, Full / Part-time employment: Janssen. J.S. Simon: Shareholder / Stockholder / Stock options, Full / Part-time employment: Janssen. S. Cheng: Shareholder / Stockholder / Stock options, Full / Part-time employment: Janssen. All other authors have declared no conflicts of interest.