Purpose: Gemcitabine requires transporter proteins to cross cell membranes. Low expression of human equilibrative nucleoside transporter-1 (hENT1) may result in gemcitabine resistance in pancreatic ductal adenocarcinoma (PDAC). CO-101, a lipid-drug conjugate of gemcitabine, was rationally designed to enter cells independently of hENT1. We conducted a randomized controlled trial to determine whether CO-101 improved survival versus gemcitabine in patients with metastatic PDAC (mPDAC) with low hENT1. The study also tested the hypothesis that gemcitabine is more active in patients with mPDAC tumors with high versus low hENT1 expression.
Patients and methods: Patients were randomly assigned to CO-101 or gemcitabine, after providing a metastasis sample for blinded hENT1 assessment. An immunohistochemistry test measuring tumor hENT1 was developed. To dichotomize the population, an hENT1 cutoff value was defined using primary PDAC samples from an adjuvant trial, and a high/low cutoff was applied. The primary end point was overall survival (OS) in the low hENT1 subgroup.
Results: Of 367 patients enrolled, hENT1 status was measured in 358 patients (97.5%). Two hundred thirty-two (64.8%) of 358 patients were hENT1 low. There was no difference in OS between treatments in the low hENT1 subgroup or overall, with hazard ratios (HRs) of 0.994 (95% CI, 0.746 to 1.326) and 1.072 (95% CI, 0.856 to 1.344), respectively. The toxicity profiles in both arms were similar. Within the gemcitabine arm, there was no difference in survival between the high and low hENT1 subgroups (HR, 1.147; 95% CI, 0.809 to 1.626).
Conclusion: CO-101 is not superior to gemcitabine in patients with mPDAC and low tumor hENT1. Metastasis hENT1 expression did not predict gemcitabine outcome.