Inhibitors Of Mitochondrial Thymidine Kinase Research Articles

Synthesis, modeling and evaluation of 3′-(1-aryl-1H-tetrazol-5-ylamino)-substituted 3′-deoxythymidine derivatives as potent and selective human mitochondrial thymidine kinase inhibitors

Based on the presumed binding mode of an earlier identified inhibitor, we herein report new 3'-modified nucleosides as potent and selective inhibitors of mitochondrial thymidine kinase (TK2). A series of thirteen 3'-amino-, 3'-guanidino- and 3'-tetrazole-containing nucleosides were synthesized and evaluated for their TK2 inhibitory activity. Within the tetrazole series, compounds with nanomolar inhibitory activity were identified. A homology model of TK2 allowed to elucidate the observed activities. Introduction of a 2-bromovinyl group on C-5 of the pyrimidine base of the most promising 3'-derivative further improved the inhibitory activity, and caused a significant increase in the selectivity for TK2 versus TK1. Interestingly, for the current series of analogues, a strong correlation was observed between TK2 and Drosophila melanogaster dNK inhibition, further substantiating the phylogenetic relationship between these two nucleoside kinases.

3′-[4-Aryl-(1,2,3-triazol-1-yl)]-3′-deoxythymidine Analogues as Potent and Selective Inhibitors of Human Mitochondrial Thymidine Kinase

In an effort to increase the potency and selectivity of earlier identified substrate-based inhibitors of mitochondrial thymidine kinase 2 (TK-2), we now describe the synthesis of new thymidine analogues containing a 4- or 5-substituted 1,2,3-triazol-1-yl substituent at the 3'-position of the 2'-deoxyribofuranosyl ring. These analogues were prepared by Cu- and Ru-catalyzed cycloadditions of 3'-azido-3'-deoxythymidine and the appropriate alkynes, which produced the 1,4- and 1,5-triazoles, respectively. Selected analogues showed nanomolar inhibitory activity for TK-2, while virtually not affecting the TK-1 counterpart. Enzyme kinetics indicated a competitive and uncompetitive inhibition profile against thymidine and the cosubstrate ATP, respectively. This behavior is rationalized by suggesting that the inhibitors occupy the substrate-binding site in a TK-2-ATP complex that maintains the enzyme's active site in a closed conformation through the stabilization of a small lid domain.

Molecules

The use of inhibitors of mitochondrial thymidine kinase might help resolve fundamental questions regarding the physiological role of this enzyme and its contribution to the mitochondrial toxicity of antiviral drugs.

Novel ribofuranosylnucleoside lead compounds for potent and selective inhibitors of mitochondrial thymidine kinase-2.

The ribonucleoside analogues (E)-5-(2-bromovinyl)uridine (5-BV-Urd) and 3'-spiro-(4'-amino-1',2'-oxathiole-2',2'-dioxide)-5-methyluridine (3'-AOD-5-MeUrd) emerged as potent and selective competitive inhibitors of mitochondrial thymidine kinase (TK)-2 with respect to thymidine (K(i)/K(m) values of 9.0 and 1.2 respectively). Cytosolic TK-1 did not show measurable affinity for these compounds. [(32)P]Phosphate transfer studies from [gamma-(32)P]ATP to 5-BV-Urd and 3'-AOD-5-MeUrd revealed extremely poor substrate activity but potent inhibitory potential of the compounds. It was concluded that the ribonucleosides 5-BV-Urd and 3'-AOD-5-MeUrd represent two new lead compounds for potent and selective inhibitors of mitochondrial TK-2.

Novel ribofuranosylnucleoside lead compounds for potent and selective inhibitors of mitochondrial thymidine kinase-2

The ribonucleoside analogues (E)-5-(2-bromovinyl)uridine (5-BV-Urd) and 3´-spiro-(4´-amino-1´,2´-oxathiole-2´,2´-dioxide)-5-methyluridine (3´-AOD-5-MeUrd) emerged as potent and selective competitive inhibitors of mitochondrial thymidine kinase (TK)-2 with respect to thymidine (Ki/Km values of 9.0 and 1.2 respectively). Cytosolic TK-1 did not show measurable affinity for these compounds. [32P]Phosphate transfer studies from [γ-32P]ATP to 5-BV-Urd and 3´-AOD-5-MeUrd revealed extremely poor substrate activity but potent inhibitory potential of the compounds. It was concluded that the ribonucleosides 5-BV-Urd and 3´-AOD-5-MeUrd represent two new lead compounds for potent and selective inhibitors of mitochondrial TK-2.