A Phase 2 clinical trial conducted at the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins has explored the efficacy of combining entinostat, a histone deacetylase (HDAC) inhibitor, with nivolumab, an anti-PD-1 immune checkpoint inhibitor, in patients with previously treated metastatic pancreatic ductal adenocarcinoma. The open-label, single-arm trial, registered under NCT03250273, enrolled patients between November 2017 and November 2020.
Study Design and Patient Population
Eligible patients were at least 18 years old with histologically confirmed pancreatic adenocarcinoma that had progressed after one or two lines of prior therapy. They also needed to have an ECOG performance status of 0 or 1, adequate hematologic, renal, and hepatic function, and measurable disease. Exclusion criteria included prior epigenetic therapy or immune checkpoint inhibitors, active autoimmune diseases, active infections, and other factors that could interfere with the study.
Patients received entinostat 5 mg orally once a week. After a 14-day lead-in with entinostat monotherapy, nivolumab 240 mg was administered intravenously every two weeks. After 4 months, nivolumab was given at a fixed dose of 480 mg every 4 weeks as maintenance therapy. Treatment continued until disease progression, unacceptable toxicity, or withdrawal. Patients underwent fresh tumor biopsies and blood draws at baseline, after two weeks of entinostat lead-in therapy, and on week 6 following combination therapy.
Efficacy and Safety
The primary endpoint of the trial was the objective response rate (ORR) assessed by RECIST 1.1. Secondary endpoints included safety, progression-free survival (PFS), and overall survival (OS). Exploratory objectives included biomarker and immunological analysis of serial tumor biopsies and peripheral blood samples.
The study utilized a Simon’s two-stage, minimax design. The null hypothesis that the true ORR is 5% or less was rejected if 4 or more responses were observed in 27 subjects. The trial was designed to have 80% power at a one-sided type I error rate of 5% when the true response rate was 20%.
Correlative Science and Biomarker Analysis
Correlative science analyses included CyTOF data acquisition and analysis, multiplex IHC (mIHC), RNA-seq, and cytokine analysis. These analyses aimed to identify potential biomarkers associated with treatment response and to understand the immunological changes induced by the combination therapy.
RNA sequencing experiments were conducted on tumor biopsies collected at baseline, after entinostat lead-in, and after combination therapy. Differential expression analysis was performed using the DESeq2 package, and gene set enrichment analysis was conducted using fgsea with MSigDb pathways.
Cytokine and chemokine concentrations were assessed using Luminex bead-based immunoassays to detect multiple target proteins in serum/plasma specimens.
Clinical Implications
This study suggests that the combination of entinostat and nivolumab may offer a potential therapeutic strategy for patients with previously treated metastatic pancreatic ductal adenocarcinoma. Further research is warranted to validate these findings and to identify predictive biomarkers that can help guide treatment decisions.
