Neo-adjuvant PARP inhibition prior to prostatectomy: A phase II biomarker-driven trial for men with high-risk, localized prostate cancer and alterations in DNA repair genes.

TPS401 Background: Many men with localized prostate cancer will experience recurrence and progression after radical prostatectomy. While radiation therapy for high-risk prostate cancer is routinely given with systemic androgen therapy, peri-operative systemic therapy is not part of the standard of care with prostatectomy. Defective DNA repair pathways represent a non-hormonal target for PARP inhibitors which have proven efficacy in the metastatic, castrate resistant setting. We designed a novel biomarker driven neoadjuvant trial with niraparib prior to prostatectomy for men with clinically localized high risk prostate cancer and alterations in DNA repair genes (NCT04030559). Methods: We instituted a phase II trial for men with NCCN high and very high-risk prostate cancer. All men who met inclusion by clinical variables underwent targeted genomic sequencing for somatic and/or germline alterations in genes involved in DNA repair pathways. Enrolled patients are treated with oral Niraparib 300mg/day for 90 days before surgery. The primary endpoint is pathologic response at prostatectomy defined as complete response or minimal residual disease (<0.5 cc3) of histological viable cancer. The secondary endpoint is biochemical free survival as well as molecular endpoints including disease responses stratified by mutational status. We have screened 37 men and 10 have met genomic criteria. We have enrolled 8 out of planned 30 men to date, 7 have undergone prostatectomy. Enrolled men have alterations in BRCA2 (germline), MSH6, ZMYM3, MUTYH, ATM, CDK12, ERCC3 and KMT2c. Clinical trial information: NCT04030559 .