Phase II trial of the ribonucleotide reductase inhibitor 3-aminopyridine-2-carboxaldehydethiosemicarbazone plus gemcitabine in patients with advanced biliary tract cancer

Abstract

Background: 3-Aminopyridine-2-carboxaldehydethiosemicarbazone (3-AP) is a novel small molecule ribonucleotide reductase (RR) inhibitor which is more potent than hydroxyurea, the prototype of RR inhibitors. 3-AP enhances the cellular uptake and DNA incorporation of gemcitabine in tumor cell lines. We evaluated the combination of 3-AP plus gemcitabine in advanced biliary tract adenocarcinoma.

Methods: Thirty-three patients with advanced adenocarcinoma of the gall bladder or biliary tract received gemcitabine (1,000 mg/m(2) on days 1, 8, and 15 every 28 days) 1 h after completing a 4-h infusion of 3-AP given at a dose of 105 mg/m(2) in patients with normal liver function (stratum A) or 80 mg/m(2) if abnormal liver function (stratum B). The trial was designed to determine whether the response rate was at least 30% in stratum A and 20% in stratum B.

Results: Objective response occurred in 3 of 23 patients (13%, 95% confidence intervals [CI] 3, 34%) with normal liver function, and in 0 of 10 patients with abnormal liver function. The most common grade 3-4 adverse events in all patients included neutropenia (42%), infection (33%), thrombocytopenia (27%), anemia (18%), and fatigue (15%). Fine needle aspiration of tumor samples obtained before and 24 h after 3-AP therapy showed increased R2 mRNA expression by in situ RT-PCR, suggesting RR inhibition.

Conclusions: Despite evidence for RR inhibition in vivo, the 3-AP plus gemcitabine combination is not likely to be associated with a response rate exceeding 30% in patients with adenocarcinoma of the biliary tract.

Trial registration: ClinicalTrials.gov NCT00075504.

Figures

Fig. 1

a–d In situ RT–PCR analysis of RRM2 expression in fine needle tumor aspirate of tumor samples pre-treatment (a, c) and 24-h post-treatment (b, d) with gemcitabine and 3-AP in patients 4 (a, b) and 6 (c, d). Black arrows indicate nuclear staining, while gray arrows indicate cytoplasmic staining. There was qualitatively increased RRM2 mRNA expression when compared with pre-treatment samples in both patients, suggesting in vivo inhibition of ribonucleotide reductase

Fig. 2

QRT-PCR analysis of RRM1, RRM2, and RRM2b represents fold change in RRM1, RRM2, and RRM2b mRNA expression in peripheral blood mononuclear cells 24-h post-treatment with 3-AP plus gemcitabine in patients 4, 16, 27 and 31. Fold change is relative to pre-treatment sample, and all samples were normalized to TATA-binding protein (TBP). There was a quantitative decrease in PBMC RRM2 mRNA expression after 3-AP/gemcitabine therapy in 3 of 4 patients evaluated, and variable effects observed in RRM1 and RRM2b

Fig. 3

Deoxynucleotide cytidine triphosphate pools (dCTP) in peripheral blood mononuclear cells (PBMCs) before and 24-h post-treatment with 3-AP plus gemcitabine in patients 30 and 31. dCTP pool assays were performed in triplicate and repeated 3 times. There was a significant decrease after 3-AP/gemcitabine therapy in PBMC dCTP pools in patient 30 (P = 0.012), whereas a significant increase was seen in patient 31 (P = 0.044)