Deoxycytidine

FDA approved drugs -> Active ingredient

FDA approved drugs -> Active ingredient

White powder; [Sigma-Aldrich MSDS]

Solid

158.41 Ų [M+Na]+ [CCS Type: DT; Method: stepped-field]

146.84 Ų [M-H]- [CCS Type: DT; Method: single field calibrated with Agilent tune mix (Agilent)]

155.2 Ų [M+Na]+ [CCS Type: DT; Method: single field calibrated with ESI Low Concentration Tuning Mix (Agilent)]

149.1 Ų [M-H]-

This chemical does not meet GHS hazard criteria for 92.3% (12 of 13) of all reports.

Not Classified

Aggregated GHS information provided per 13 reports by companies from 2 notifications to the ECHA C&L Inventory.

Doxecitine's primary action is a substrate enhancement therapy that corrects the nucleoside imbalance caused by TK2d deficiency. The goal is to provide a high systemic concentration of deoxycytidine and deoxythymidine that can be utilized by unaffected salvage pathways. This action restores the synthesis of mitochondrial DNA (mtDNA) precursors, leading to the restoration of mtDNA copy number and subsequent improvement in respiratory chain enzyme (RCE) activities in affected tissues. This systemic correction counteracts the relentless muscle weakness and respiratory failure characteristic of TK2d, resulting in the amelioration of myopathy, delay of disease onset, and significantly prolonged survival in both preclinical models and patients.

The progressive, often fatal myopathy seen in Thymidine Kinase 2 deficiency (TK2d) is caused by mutations in the nuclear TK2 gene, leading to a dysfunctional or deficient mitochondrial TK2 enzyme. This enzyme is essential for phosphorylating the pyrimidine nucleosides doxecitine (dC) and thymidine (dT) into dCMP and dTMP, which are precursors for the deoxyribonucleotide triphosphates (dNTPs) required for mitochondrial DNA (mtDNA) maintenance and replication. The resulting metabolic block causes severe mtDNA depletion and dysfunction of the mitochondrial respiratory chain.[] Doxecitine, in combination with doxribtimine, functions as a nucleoside substrate enhancement therapy that successfully bypasses the defective mitochondrial pathway. The high concentrations of exogenous dC and dT are primarily phosphorylated by intact cytosolic salvage enzymes, specifically Deoxycytidine Kinase (dCK) and Thymidine Kinase 1 (TK1). The nucleosides are actively transported into cells and across the blood-brain barrier via equilibrative nucleoside transporters. The resulting phosphorylated dNTP precursors are then made available to the mitochondria. This replenishes the critically depleted dNTP pools, which facilitates the replication of mtDNA by the mitochondrial DNA Polymerase gamma.

Doxecitine is primarily degraded by cytidine deaminase to its nucleobases and the 2-deoxy-α-D-ribose 1-phosphate moiety. Intermediate products of doxecitine catabolism are deoxyuridine, uracil, and dihydrouracil with the end products β-alanine, ammonia, and carbon dioxide (CO2).

Doxecitine is administered orally, with rapid absorption and plasma concentrations returning to near baseline within 8 to 12 hours. The absolute bioavailability of doxecitine following oral administration has not been determined. The median time to peak plasma concentration (Tmax) was approximately two hours for doxecitine.

Urinary excretion of intact doxecitine and doxribtimine was <1% of the dose in healthy subjects following an oral administration of doxecitine and doxribtimine.