Chemistry of Fluorinated Pyrimidines in the Era of Personalized Medicine

We review developments in fluorine chemistry contributing to the more precise use of fluorinated pyrimidines (FPs) to treat cancer. 5-Fluorouracil (5-FU) is the most widely used FP and is used to treat > 2 million cancer patients each year. We review methods for 5-FU synthesis, including the incorporation of radioactive and stable isotopes to study 5-FU metabolism and biodistribution. We also review methods for preparing RNA and DNA substituted with FPs for biophysical and mechanistic studies. New insights into how FPs perturb nucleic acid structure and dynamics has resulted from both computational and experimental studies, and we summarize recent results. Beyond the well-established role for inhibiting thymidylate synthase (TS) by the 5-FU metabolite 5-fluoro-2′-deoxyuridine-5′-O-monophosphate (FdUMP), recent studies have implicated new roles for RNA modifying enzymes that are inhibited by 5-FU substitution including tRNA methyltransferase 2 homolog A (TRMT2A) and pseudouridylate synthase in 5-FU cytotoxicity. Furthermore, enzymes not previously implicated in FP activity, including DNA topoisomerase 1 (Top1), were established as mediating FP anti-tumor activity. We review recent literature summarizing the mechanisms by which 5-FU inhibits RNA- and DNA-modifying enzymes and describe the use of polymeric FPs that may enable the more precise use of FPs for cancer treatment in the era of personalized medicine.

Synthesis of 4-amino-5-fluoropyrimidines and 5-amino-4-fluoropyrazoles from a β-fluoroenolate salt

A synthesis of fluorinated pyrimidines under mild conditions from amidine hydrochlorides and the recently described potassium 2-cyano-2-fluoroethenolate was developed. A broad substrate scope was tested and mostly excellent yields were obtained. The synthesis of fluorinated aminopyrazoles from the same fluorinated precursor could be demonstrated but proceeded with lower efficiency.

Deletion of the Uracil Permease Gene Confers Cross-Resistance to 5-Fluorouracil and Azoles in Candida lusitaniae and Highlights Antagonistic Interaction between Fluorinated Nucleotides and Fluconazole

ABSTRACTWe characterized two additional membrane transporters (Fur4p and Dal4p) of the nucleobase cation symporter 1 (NCS1) family involved in the uptake transport of pyrimidines and related molecules in the opportunistic pathogenic yeastCandida lusitaniae. Simple and multiple null mutants were constructed by gene deletion and genetic crosses. The function of each transporter was characterized by supplementation experiments, and the kinetic parameters of the uptake transport of uracil were measured using radiolabeled substrate. Fur4p specifically transports uracil and 5-fluorouracil. Dal4p is very close to Fur4p and transports allantoin (glyoxyldiureide). Deletion of theFUR4gene confers resistance to 5-fluorouracil as well as cross-resistance to triazoles and imidazole antifungals when they are used simultaneously with 5-fluorouracil. However, the nucleobase transporters are not involved in azole uptake. Only fluorinated pyrimidines, not pyrimidines themselves, are able to promote cross-resistance to azoles by both the salvage and thede novopathway of pyrimidine synthesis. A reinterpretation of the data previously obtained led us to show that subinhibitory doses of 5-fluorocytosine, 5-fluorouracil, and 5-fluorouridine also were able to trigger resistance to fluconazole in susceptible wild-type strains ofC. lusitaniaeand of differentCandidaspecies. Our results suggest that intracellular fluorinated nucleotides play a key role in azole resistance, either by preventing azoles from targeting the lanosterol 14-alpha-demethylase or its catalytic site or by acting as a molecular switch for the triggering of efflux transport.

SAMIT: A phase III randomized clinical trial of adjuvant paclitaxel followed by oral fluorinated pyrimidines for locally advanced gastric cancer.

LBA4002 Background: Adjuvant chemotherapy with tegafur/uracil (UFT) used to be a tentative Japanese standard treatment and has been replaced by S-1 according to the result of the ACTS-GC trial, although there has been no direct comparison. Paclitaxel (PTX) has been widely used as one of the key drugs for unresectable GC. A randomized phase III trial with a two-by-two factorial design was planned to assess the survival benefit of sequential use of PTX and oral fluorinated pyrimidines (FPs) in comparison with FPs alone, and to compare UFT and S-1. Methods: Patients with serosa-invading GC who underwent R0/1 resection with extended (D2) lymph node dissection were randomized to receive either UFT 267mg/m2 daily (arm A), S-1 80mg/m2 daily for 2 weeks every 3 weeks (B), weekly PTX 80 mg/m2 followed by UFT (C), or PTX followed by S-1 (D) for 24 weeks. The primary endpoint was disease-free survival (DFS). 708 patients per groups were necessary to detect a hazard ratio of 0.8 with 90% power for superiority of the sequential arms, C+D, vs. A+B (two-sided 5.0% significance level). The number of patients was set to 370 per arm (total 1480) with an 88% power for noninferiority (1.33 as the margin) of UFT vs. S-1. Results: Between August 2004 and October 2007, 1,495 patients from 232 centers were randomized with the full analysis set of 1,433. Demographics were well balanced among arm A (n=359), B (n=364), C (n=355), and D (n=355); mean age was 64, 86% were PS 0, 68% of tumors were 8 cm or greater and 85% were clinically node positive. Grade 3-4 neutropenia or anorexia occurred in 11% or 6%, 13% or 7%, 13% or 2%, and 23% or 5% for arm A, B, C, and D, respectively. Other % grade 3-4 toxicities were less than 5%. Median follow-up was 1,875 days and 728 events occurred. Difference in DFS between C+D and A+B were not statistically significant (HR=0.92, 95%CI 0.80-1.07, p= 0.273). HR of A+C vs. B+D was 1.23 (95%CI 1.07-1.43) and hence the null hypothesis was not rejected. Conclusions: There was a trend for better DFS for sequential use of PTX followed by FPs. Comparison between the FPs demonstrated that UFT was inferior to S-1. Sequential PTX/S-1 is safe and effective for locally advanced GC in an adjuvant setting. Clinical trial information: C000000082.

SAMIT: A phase III randomized clinical trial of adjuvant paclitaxel followed by oral fluorinated pyrimidines for locally advanced gastric cancer.

LBA4002 The full, final text of this abstract will be available at abstract.asco.org at 7:30 AM (EDT) on Monday, June, 3, 2013, and in the Annual Meeting Proceedings online supplement to the June 20, 2013, issue of Journal of Clinical Oncology. Onsite at the Meeting, this abstract will be printed in the Monday edition of ASCO Daily News.