Phase 2 study of azacitidine plus pembrolizumab as second-line treatment in patients with locally advanced or metastatic pancreatic ductal adenocarcinoma.

[BACKGROUND] Epigenetic regulators represent a novel strategy to modulate the tumor immune microenvironment in pancreatic ductal adenocarcinoma (PDAC). In preclinical models, DNA hypomethylating agents enhance cytotoxic T-cell infiltration, synergize with PD-1 blockade, and improve survival when combined with immune checkpoint blockade. This single-institution, phase II study evaluated the safety, efficacy, and biomarkers of azacitidine plus pembrolizumab in patients with previously treated PDAC.

[METHODS] Patients with locally advanced or metastatic PDAC after one prior regimen received 50 mg/m2 subcutaneous azacitidine on days 1-5 of a 28-day cycle, starting week 1, and pembrolizumab 200 mg intravenously every 3 weeks starting week 3. Baseline and on-treatment blood and tumor was collected for exploratory biomarker analysis.

[RESULTS] Thirty-six patients enrolled between October 2017 and September 2021 (median age: 62.5 years); 34 were evaluable for safety; 31 for efficacy. Treatment was generally well-tolerated, with Grade 1-2 fatigue and diarrhea most common AEs. Three patients (9.7%) had a partial response, and the disease control rate was 35.5%. Median progression-free and overall survival was 1.51 and 4.83 months, respectively. Exploratory analysis suggested higher baseline CD8+ T cells and lower tumor Ki-67 was associated with response, whereas low baseline CD8+ T cell and Granzyme B infiltration correlated with higher exponential tumor growth rate. PD-L1 and CD68 expression were not predictive of benefit.

[CONCLUSION] Azacitidine plus pembrolizumab demonstrated limited clinical activity in second line, locally advanced or metastatic PDAC. Biomarker analysis suggests higher baseline CD8+ T-cell infiltration and lower proliferative index may identify patients more likely to benefit. Clinical trial registration number: NCT03264404.