Deoxycytidine and Deoxythymidine Treatment for Thymidine Kinase 2 Deficiency
Carlos Lopez-Gomez, Rebecca J Levy, Maria J Sanchez-Quintero, Martí Juanola-Falgarona, Emanuele Barca, Beatriz Garcia-Diaz, Saba Tadesse, Caterina Garone, Michio Hirano, Carlos Lopez-Gomez, Rebecca J Levy, Maria J Sanchez-Quintero, Martí Juanola-Falgarona, Emanuele Barca, Beatriz Garcia-Diaz, Saba Tadesse, Caterina Garone, Michio Hirano
Abstract
Objective: Thymidine kinase 2 (TK2), a critical enzyme in the mitochondrial pyrimidine salvage pathway, is essential for mitochondrial DNA (mtDNA) maintenance. Mutations in the nuclear gene, TK2, cause TK2 deficiency, which manifests predominantly in children as myopathy with mtDNA depletion. Molecular bypass therapy with the TK2 products, deoxycytidine monophosphate (dCMP) and deoxythymidine monophosphate (dTMP), prolongs the life span of Tk2-deficient (Tk2-/- ) mice by 2- to 3-fold. Because we observed rapid catabolism of the deoxynucleoside monophosphates to deoxythymidine (dT) and deoxycytidine (dC), we hypothesized that: (1) deoxynucleosides might be the major active agents and (2) inhibition of deoxycytidine deamination might enhance dTMP+dCMP therapy.
Methods: To test these hypotheses, we assessed two therapies in Tk2-/- mice: (1) dT+dC and (2) coadministration of the deaminase inhibitor, tetrahydrouridine (THU), with dTMP+dCMP.
Results: We observed that dC+dT delayed disease onset, prolonged life span of Tk2-deficient mice and restored mtDNA copy number as well as respiratory chain enzyme activities and levels. In contrast, dCMP+dTMP+THU therapy decreased life span of Tk2-/- animals compared to dCMP+dTMP.
Interpretation: Our studies demonstrate that deoxynucleoside substrate enhancement is a novel therapy, which may ameliorate TK2 deficiency in patients. Ann Neurol 2017;81:641-652.
Conflict of interest statement
Potential Conflict of Interest: Dr. Hirano and Columbia University Medical Center (CUMC) have filed patent applications covering the potential use of deoxynucleoside treatment for TK2 deficiency in humans. CUMC has licensed pending patent applications related to the technology to Meves Pharmaceuticals, Inc. and CUMC may be eligible to receive payments related to the development and commercialization of the technology. Any potential licensing fees earned will be paid to CUMC and are shared with Dr. Hirano through CUMC distribution policy. Dr. Hirano will serve as a paid consultant to Meves Pharmaceutical, Inc.
© 2017 American Neurological Association.
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Source: PubMed