Randomized phase II trial of olaparib + pembrolizumab vs olaparib alone as maintenance therapy in patients with metastatic pancreatic cancer with germline BRCA1 or BRCA2 mutations: SWOG S2001 NCT04548752.

TPS793 Background: Olaparib was approved in 2019 as maintenance therapy for gBRCA1/2+ metastatic pancreatic cancer (mPDA) patients (pts). The POLO trial showed an improvement in median progression-free survival (mPFS) with olaparib compared to placebo (7.4 vs 3.8 months) for platinum sensitive gBRCA1/2+ mPDA pts. Preclinical studies have demonstrated that PARP inhibitors modulate the immune microenvironment by increasing genomic instability, PD-L1 expression and activating the immune inflammatory stimulator of interferon genes (STING) pathway. Results of the phase 2 pembrolizumab and olaparib (POLAR) maintenance trial in patients with germline or somatic BRCA1/2 or PALB2 mutations responding to platinum-based chemotherapy for at least 4 months was presented at ESMO 2024. In 33 patients, a 35% overall response rate with 90% disease control rate at 6 months was observed. S2001 is an important randomized study to better define the impact of the combination. Methods: S2001 was developed in collaboration with the Alliance and was activated in SWOG in October 2020. Key eligibility criteria include: mPDA pts with gBRCA1/2 mutations identified with standard of care germline genetic testing and progression-free after receiving at least 4 months of platinum-based chemotherapy (FOLFIRINOX, FOLFOX or gemcitabine/cisplatin +/- nab-paclitaxel). One cycle of gemcitabine and nab-paclitaxel is allowed while waiting for germline testing. Zubrod performance status (PS) 0 or 1 pts are eligible. Pts are stratified according to first line chemotherapy, PS 0 vs 1, and disease status after 1st line treatment. The primary objective of this study is to evaluate the PFS of mPDA pts treated with olaparib + pembrolizumab compared to olaparib alone as maintenance therapy. Based upon the POLO trial, we expect a mPFS of 7 months in the control arm. Targeting a mPFS of 11.7 months in the experimental arm (hazard ratio 0.6) and assuming 15 months follow-up, 80% power and a 1-sided alpha = 0.10, this design requires 78 evaluable pts with a total sample size of 88 pts. Prospective serial blood samples will be collected to bank DNA and RNA for future correlative studies. Support: NIH/NCI grants U10CA180888 and U10CA180819, U10CA180821 and U10CA180868. Clinical trial information: NCT04548752 .