Phase 2 trial of pembrolizumab and olaparib (POLAR) maintenance for patients (pts) with metastatic pancreatic cancer (mPDAC): Two cohorts B non-core homologous recombination deficiency (HRD) and C exceptional response to platinum-therapy.
Wungki Park, Catherine O’Connor, Joanne F. Chou, Carly Schwartz, Anna M. Varghese, Mary Pat Larsen, Fiyinfolu Balogun, Robin Brenner, Kenneth H. Yu, Erin Diguglielmo, Shigeaki Umeda, Elias Karnoub, Fergus Keane, Haochen Zhang, Smita S. Joshi, Nadeem Riaz, David P. Kelsen, Marinela Capanu, Christine A. Iacobuzio–Donahue, Eileen M. O’Reilly
Abstract
4140 Background: Maintenance olaparib improves PFS in g BRCA1/2m (core HRD) in mPDAC (Golan, NEJM 2019). Whether other HRD indicators, such as gene mutations other than g BRCA1/2m (non-Core HRD, Cohort B) and exceptional platinum responders (Cohort C, response > 6 months) may benefit from PARPi in mPDAC remains unanswered. We hypothesized that pembrolizumab and olaparib (POLAR) combination may improve outcome by immunogenic cell death. Methods: We conducted an open-label, non-randomized, phase 2 trial of POLAR as maintenance therapy for pts with mPDAC whose disease had not progressed for 4 months (m) in Cohort B or 6 m in C. Herein, we report on Cohorts B & C. Eligibility: ECOG 0-1, mPDAC meeting eligibility of B or C. POLAR (Pembrolizumab 200mg IV Q3W+ OLApaRib 300mg BID) until disease progression or limiting toxicity. Objective response rate (ORR), median PFS (mPFS), median overall survival (mOS), disease control rate (DCR), CA 19-9, cfDNA and baseline HRD mutational signature were analyzed. Results: Cohorts B and C enrolled N=15 each. N=25 pts evaluable by RECIST 1.1. Median follow-up 9.9 (1.3-22.8) and 11.3 (5.8-23) m, respectively. Efficacy details are shown. G3-5 AEs related to treatment: 5/14 (36%): 1 diarrhea (7%), 1 hyperglycemia (7%), 2 anemia (14%), 1 lipase increased (7%). Cohort B: 9/15 (60%) ATM, 3 CHEK2, 2 MUTYH, 1 BLM, 1 FANCC. Canonical gene mutations for mPDAC were less common for pts in Cohort B, especially in ATM PA group (n=9) vs C. Median genomic instability score (GIS) was computed and higher 28 (0-38) vs 9 (0-24) in Cohort B vs C, p=0.052. Median tumor mutation burden (TMB) was not different between B and C (3.3 and 4.1). Conclusions: Clinical activity of POLAR maintenance observed in select pts in B and C. Although PFS was modest (mPFS of 4m [2.1-5.4] in B + C), an intriguing survival signal (mOS at 14m [10-NR] from first POLAR dose) was seen in select patients without chemotherapy. Extensive correlative analyses underway to evaluate response and resistance (SPORE: 1P50CA257881-01A1). Cohort A (core HRD) actively accruing. Clinical trial information: NCT04666740 . [Table: see text]