A signal-seeking trial of olaparib and durvalumab in homologous repair-deficient tumors: A sub-study of the cancer molecular screening and therapeutics (MoST) program.

Abstract

3073 Background: Data on the utility of a PARP inhibitor in combination with a checkpoint inhibitor remain limited, particularly in the histology agnostic setting with homologous recombination deficiency (HRD). This study evaluated the clinical activity of the combination of olaparib and durvalumab with the primary study endpoint of progression-free survival (PFS) at 6 months (PFS6m). Methods: This was a phase II, single-arm, signal-seeking study of the MoST program. Patients were recruited into two cohorts based on HRD genes, agnostic to histology: (1) BRCA 1/2 deficient tumours, excluding breast, prostate, ovarian cancers, and (2) other HRD related genes. Molecular testing was performed using in-house and commercial panels on archival tumour tissue centrally adjudicated by a molecular tumour board. All patients were treated with olaparib 300mg bid for 1 month, followed by combination with durvalumab 1500mg q4 weekly for 13 cycles. Olaparib treatment was then continued until disease progression. Results: Between Nov 2017-Feb 2019, 48 patients were enrolled (16 to BRCA 1/2 cohort 1 and 32 to HRD related genes cohort 2). Most common tumour sites were bone/soft tissue (15%, N=7), pancreas (13%, N=6) and stomach (8%, N=4). Overall best response in cohort 1 was PR (25%, N=4) and SD 4 (25%, N=4), and cohort 2 was PR (6%, N=2) and SD (56%, N=18). Median PFS was 3.65m (Cohort 1) and 3.56m (Cohort 2) respectively. PFS6m was 35% (Cohort 1) and 38% (Cohort 2) respectively. PDL1 status was not predictive of olaparib and durvalumab benefit. The most common grade 3/4 adverse events were anemia (11%%, N=4), abdominal pain (9%, N=3), increased lipase (9%,N=3), increased amylase (9%, N=3), dyspnea (6%, N=2), Hyperglycemia dyspnea (6%, N=2), Pancreatitis dyspnea (6%, N=2) and hematuria (6%, N=2). Conclusions: Olaparib and durvalumab show promising activity in a histology agnostic setting, particularly in BRCA deficient tumours. Further research is needed to identify biomarkers that correlate with treatment benefit. Results from longer clinical follow-up and additional biomarker analyses will be presented. Clinical trial information: ACTRN12617001000392 .