Synthesis and Discovery of <i>N</i>-Carbonylpyrrolidine- or <i>N</i>-Sulfonylpyrrolidine-Containing Uracil Derivatives as Potent Human Deoxyuridine Triphosphatase Inhibitors

Recently, deoxyuridine triphosphatase (dUTPase) has emerged as a potential target for drug development as part of a new strategy of 5-fluorouracil-based combination chemotherapy. We have initiated a program to develop potent drug-like dUTPase inhibitors based on structure–activity relationship (SAR) studies of uracil derivatives. <i>N</i>-Carbonylpyrrolidine- and <i>N</i>-sulfonylpyrrolidine-containing uracils were found to be promising scaffolds that led us to human dUTPase inhibitors (<b>12k</b>) having excellent potencies (IC₅₀ = 0.15 μM). The X-ray structure of a complex of <b>16a</b> and human dUTPase revealed a unique binding mode wherein its uracil ring and phenyl ring occupy a uracil recognition region and a hydrophobic region, respectively, and are stacked on each other. Compounds <b>12a</b> and <b>16a</b> markedly enhanced the growth inhibition activity of 5-fluoro-2′-deoxyuridine against HeLa S3 cells in vitro (EC₅₀ = 0.27–0.30 μM), suggesting that our novel dUTPase inhibitors could contribute to the development of chemotherapeutic strategies when used in combination with TS inhibitors

Discovery of Highly Potent Human Deoxyuridine Triphosphatase Inhibitors Based on the Conformation Restriction Strategy

Human deoxyuridine triphosphatase (dUTPase) inhibition is a promising approach to enhance the efficacy of thymidylate synthase (TS) inhibitor based chemotherapy. In this study, we describe the discovery of a novel class of human dUTPase inhibitors based on the conformation restriction strategy. On the basis of the X-ray cocrystal structure of dUTPase and its inhibitor compound <b>7</b>, we designed and synthesized two conformation restricted analogues, i.e., compounds <b>8</b> and <b>9</b>. These compounds exhibited increased in vitro potency compared with the parent compound <b>7</b>. Further structure–activity relationship (SAR) studies identified a compound <b>43</b> with the highest in vitro potency (IC₅₀ = 39 nM, EC₅₀ = 66 nM). Furthermore, compound <b>43</b> had a favorable oral PK profile and exhibited potent antitumor activity in combination with 5-fluorouracil (5-FU) in the MX-1 breast cancer xenograft model. These results suggested that a dUTPase inhibitor may have potential for clinical usage

1,2,3-Triazole-Containing Uracil Derivatives with Excellent Pharmacokinetics as a Novel Class of Potent Human Deoxyuridine Triphosphatase Inhibitors

Deoxyuridine triphosphatase (dUTPase) has emerged as a potential target for drug development as a 5-fluorouracil-based combination chemotherapy. We describe the design and synthesis of a novel class of human dUTPase inhibitors, 1,2,3-triazole-containing uracil derivatives. Compound <b>45a</b>, which possesses 1,5-disubstituted 1,2,3-triazole moiety that mimics the amide bond of <i>tert</i>-amide-containing inhibitor <b>6b</b> locked in a cis conformation showed potent inhibitory activity, and its structure–activity relationship studies led us to the discovery of highly potent inhibitors <b>48c</b> and <b>50c</b> (IC₅₀ = ∼0.029 μM). These derivatives dramatically enhanced the growth inhibition activity of 5-fluoro-2′-deoxyuridine against HeLa S3 cells in vitro (EC₅₀ = ∼0.05 μM). In addition, compound <b>50c</b> exhibited a markedly improved pharmacokinetic profile as a result of the introduction of a benzylic hydroxy group and significantly enhanced the antitumor activity of 5-fluorouracil against human breast cancer MX-1 xenograft model in mice. These data indicate that <b>50c</b> is a promising candidate for combination cancer chemotherapies with TS inhibitors

Discovery of a Novel Class of Potent Human Deoxyuridine Triphosphatase Inhibitors Remarkably Enhancing the Antitumor Activity of Thymidylate Synthase Inhibitors

Inhibition of human deoxyuridine triphosphatase (dUTPase) has been identified as a promising approach to enhance the efficacy of 5-fluorouracil (5-FU)-based chemotherapy. This study describes the development of a novel class of dUTPase inhibitors based on the structure–activity relationship (SAR) studies of uracil derivatives. Starting from the weak inhibitor <b>7</b> (IC₅₀ = 100 μM), we developed compound <b>26</b>, which is the most potent human dUTPase inhibitor (IC₅₀ = 0.021 μM) reported to date. Not only does compound <b>26</b> significantly enhance the growth inhibition activity of 5-fluoro-2′-deoxyuridine (FdUrd) against HeLa S3 cells in vitro (EC₅₀ = 0.075 μM) but also shows robust antitumor activity against MX-1 breast cancer xenograft model in mice when administered orally with a continuous infusion of 5-FU. This is the first in vivo evidence that human dUTPase inhibitors enhance the antitumor activity of TS inhibitors. On the basis of these findings, it was concluded that compound <b>26</b> is a promising candidate for clinical development