Phase Ib/II study of gemcitabine, nab-paclitaxel, and pembrolizumab in metastatic pancreatic adenocarcinoma.

Background A single center phase Ib/II study of gemcitabine, nab-paclitaxel, and pembrolizumab (GNP) to evaluate the safety and efficacy in metastatic pancreatic adenocarcinoma (PDAC) was conducted (NCT02331251). Methods PDAC patients (pts) with measurable disease, biopsy proven metastasis, adequate laboratory tests, and KPS ≥ 70% received GNP until progression or toxicity. Safety monitoring, RECIST 1.1, and irRECIST assessments were conducted. Response imaging was performed prior to cycle 4, then every 3 months. Changes in tumor cell-free DNA copy number instability (CNI) was retrospectively evaluated. Results 17 pts. with a median age of 56 were treated. 11 were women and all had a KPS of at least 80%. Grade 3 events occurred in 53% of patients. The phase II portion was completed for chemotherapy naïve PDAC pts. Of the 11 evaluable chemotherapy naïve PDAC, the disease control rate (partial response [PR] + stable disease[SD]) was 100%. There were 3 with PR on treatment for 8+, ~11, and 15 months; respectively. The primary endpoint of >15% complete response was not met. The median progression-free survival (PFS) and overall survival (OS) was 9.1 and 15.0 months for chemotherapy naïve treated patients. Of 9 patients evaluable for CNI change, a greater reduction in CNI correlated with longer PFS and improved OS. Conclusions GNP can be safely given to chemotherapy naïve PDAC patients. Efficacy appears to be slightly improved over previously reported results for standard weekly × 3 every 28 day gemcitabine and nab-paclitaxel dosing. CNI change may be prognostic for OS.