Absorption, Distribution and Excretion
Azaribine is well absorbed after oral admin ... After absorption, azaribine is almost entirely deacetylated to azur /azauridine/ in blood, with some monoacetyl deriv detectable. Peak plasma concn of azur are reached after 2 to 4 hr, and plasma disappearance curve with half-time of approx 6 to 8 hr is observed. /6-Azauridine triacetyl deriv/
Unlike azauracil, azur /azauridine/ does not cross blood-brain barrier and is not detectable in CSF. When neurotoxic manifestations have been encountered, significant concn of azauracil ... measured in CSF. Approx 95% of ingested dose of azaribine is excreted in urine as azur within 16 hr. /6-Azauridine triacetyl deriv/
2',3',5'-Triacetyl-6-azauridine was administered orally to eleven patients with far advanced neoplastic disease. The compound was absorbed rapidly from the gastrointestinal tract, in contrast to free 6-azauridine. Significant blood levels of 6-azauridine were maintained during the 8-hour period intervening between doses of the acetylated derivative. Depression of the conversion of orotic acid to uridine nucleotides was demonstrated in patients undergoing therapy, by studies of the fate of intravenously injected orotic acid-7-C14 and of the urinary excretion of orotidine and orotic acid. The metabolic effects and clinical changes observed were comparable to those produced by equivalent doses of intravenously administered 6-azauridine. /2',3',5'-Triacetyl-6-azauridine/
DISTRIBUTION OF (14)C WAS SIMILAR IN NORMAL RATS & RATS WITH ADJUVANT INDUCED POLYARTHRITIS, AFTER ADMIN OF (14)C-6-AZAURIDINE...EXCEPT THAT HEPATIC (14)C CONCN WERE TWOFOLD HIGHER IN LATTER GROUP OF ANIMALS. ABOUT 1 HR AFTER IV DOSE...TO PREGNANT RATS, FETAL CONCN OF (14)C WERE ONE-THIRD THOSE OF MATERNAL CIRCULATION.

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Metabolism / Metabolites
L1210 cells... incubated with /6-azauridine/ AzUrd contained a new 254 nm-absorbing component, not found in control cells. It appeared to be 6-azauridine-5'-triphosphate, since it was the only peak in the triphosphate region of the chromatogram which contained 3H after incubation of cells with [3H]AzUrd.
... Azauridine is metabolized to azauracil by intestinal micoorganism ...
Azauridine undergoes intracellular conversion to 6-azauridylic acid ... /6-Azauridine triacetyl deriv/
After oral administration about 45 per cent of 2',3',5'-tri-O-acetyl-6-azauridine (TA-6-azauridine) is eliminated in the urine of rats, as well as in man, in the form of its deacetylation products. In the urine of rats, TA-6-azauridine is excreted almost exclusively in the form of free 6-azauridine whereas in man a substantial amount of mono-O-acetyl-azauridine (MA-6-azauridine) also was found. Furthermore, about 35 per cent of the dose was found in the form of MA-6-azauridine in the feces of rats collected during 48 hr after the administration. Neither TA-6-azauridine nor its deacetylation products are excreted in the bile of rats. 6-Azauracil was not detected as a deribosylation product of 6-azauridine neither in the urine or feces nor in the bile of rats under study. /6-Azauridine triacetyl deriv/
For more Metabolism/Metabolites (Complete) data for 6-AZAURIDINE (7 total), please visit the HSDB record page.

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Biological Half-Life
After absorption, azaribine is almost entirely deacetylated to azur /azauridine/ in blood, with some monoacetyl deriv detectable. Peak plasma concn of azur are reached after 2 to 4 hr, and plasma disappearance curve with half-time of approx 6 to 8 hr is observed. /6-Azauridine triacetyl deriv/

Interactions
Sixteen unselected patients with non-resectable hepatocellular carcinoma were treated in a phase I study with 261 cycles of D-galactosamine and 6-azauridine prior to 5-fluorouridine. Thirty % of the patients survived for more than 1 yr without signs of tumor progression and with an unchanged performance status. The compatibility of this chemotherapeutical method was quite satisfactory. The only extrahepatic side effect was a leukcopenia and/or thrombocytopenia which was reversible upon reduction of the 5-fluorouridine dose. The heterogeneity of the 16 patients treated to date does not allow a definite statistical evaluation of the reported clinical observations and results.
The effect of pyridoxine on 6-azauridine triacetate (6-AzUrd-TA) induced hyper beta-alaninemia was studied in New Zealand albino rabbits in three experiments. In each of the three experiments the animals were admin by gavage: Group 1 (Control), drinking water; Group 2, 6-AzUrd-TA; and Group 3, 6-AzUrd-TA with pyridoxine. While no beta-alanine was found in the control group or in pretreatment samples of the 6-AzUrd-Ta and 6-AzUrd-TA plus pyridoxine treated animals, high concn of this amino acid (191.0 + or - 91.6, 220.2 + or - 116.3, 103.2 + or - 64.4 nmol/ml) were found on the fourth and seventh days of 6-AzUrd-TA treatment with daily doses of 1.0 g/kg and 0.5 g/kg body weight, respectively. The drug induced hyper beta-alaninemia was significantly (p < or = 0.05) reduced in all three experiments by simultaneous pyridoxine admin in daily doses of 50 mg/kg body weight. These results indicate that daily repeated oral admin of 6-AzUrd-Ta causes elevation of serum beta-alanine, which can be partially prevented by oral admin of pyridoxine. They also indirectly support the hypothesis that 6-AzUrd-TA induced hyper beta-alaninemia is at least partially caused by the inhibition of beta-alanine degrading enzymes, that use pyridoxal phosphate as a coenzyme. /6-Azauridine triacetate/
Twenty-five metabolites (purines, pyrimidines, nucleosides and nucleosides) were tested for their simultaneous action with 6-azauridine (AzUrd) in inhibition of Newcastle disease virus (NDV) replication. With the exception of deoxyadenosine and cyclic AMP all natural adenine derivatives exerted a synergic effect with AzUrd like ATP. Glutamine in combination with AzUrd did not inhibit NDV replication. The inhibitory effect of the combination of AzUrd and adenine derivatives was reversible by guanosine, uridine and cytidine but not by orotic acid or orotidylic acid.

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Non-Human Toxicity Values
LD50 Cat ip 2400 mg/kg
LD50 Dog ip 3400 mg/kg
LD50 Mouse ip 11250 mg/kg
LD50 Rat ip 9400 mg/kg
For more Non-Human Toxicity Values (Complete) data for 6-AZAURIDINE (6 total), please visit the HSDB record page.

[1]. Robak T, Robak P. Purine nucleoside analogs in the treatment of rarer chronic lymphoid leukemias. Curr Pharm Des. 2012;18(23):3373-88.

6-azauridine is a N-glycosyl-1,2,4-triazine. It has a role as an antineoplastic agent, an antimetabolite and a drug metabolite.
6-Azauridine is a synthetic triazine analogue of uridine with antimetabolite activity. 6-azauridine inhibits de novo pyrimidine synthesis and DNA synthesis and is converted intracellularly into mono, di, and triphosphate derivatives, which incorporate into RNA and inhibit protein synthesis.
A triazine nucleoside used as an antineoplastic antimetabolite. It interferes with pyrimidine biosynthesis thereby preventing formation of cellular nucleic acids. As the triacetate, it is also effective as an antipsoriatic.

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Mechanism of Action
6-Azauridine (AzUrd) is a broad-spectrum antimetabolite that inhibits both DNA and RNA virus multiplication. Prior work indicated that several AzUrd-sensitive viruses induced an increase in the level of uridine kinase, and this might explain the selective activity of AzUrd on such viruses. Present studies compared AzUrd sensitive and resistant viruses with respect to their orotic acid pathways by labeling cells with [14C]-orotic acid during the latent period of viral infection. No differences were detected by this method with either vaccinia, Newcastle disease, or vesicular stomatitis viruses. AzUrd inhibits transport of orotic acid into the cell by 30%, while incorporation of orotic acid into cellular RNA is inhibited by 50% (taking into consideration the 30% already noted) when the highest concentration of antimetabolite is used. This suggests that, in addition to blocking orotidylic acid decarboxylase, AzUrd may act on some other site (sites) of action in the inhibition of virus multiplication.
... pyrazofurin and 6-azauridine, two nucleoside analogues that are assumed to interfere with OMP decarboxylase, another enzyme involved in the biosynthesis of pyrimidine ribonucleotides, potentiate the cytocidal activity of Ce-Cyd.
Azacitidine is readily deaminated to azauridine and further degraded. It is incorporated into DNA and alters gene expression. ... Azacitidine causes hypomethylation of DNA both in vivo and in vitro.

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Therapeutic Uses
A triazine nucleoside used as an antineoplastic antimetabolite. It interferes with pyrimidine biosynthesis thereby preventing formation of cellular nucleic acids. As the triacetate, it is also effective as an antipsoriatic.
Anti-metabolite used in psoriasis & mycosis fungoides /6-Azauridine triacetate/
/Former Use/ Azauridine (azur) and its triacetyl deriv, azaribine, have proven of ... value in treatment of psoriasis.
/Former Use/ The combination of 6-azauridine, 6-mercaptopurine, and vincristine was effective for remission induction of acute myelocytic leukemia in children.
For more Therapeutic Uses (Complete) data for 6-AZAURIDINE (17 total), please visit the HSDB record page.

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Drug Warnings
The antimetabolite 6-azauridine blocks the de novo synthesis of pyrimidines and causes increased serum levels of several amino acids including homocystine. 6-Azauridine was withdrawn from clinical use for the treatment of psoriasis because of the occurence of arterial and venous thromboembolic episodes in some psoriatic patients. Utilizing a standard animal model for the recognition of venous and arterial thrombosis, 6-azauridine was demonstrated in this study to cause thrombosis without producing homocystinemia when administered orally or intravenously.
Although the drug may be of considerable benefit in treating acute manifestations of psoriatic arthritis, it has caused unexplained exacerbations in patients with rheumatoid arthritis. /6-Azauridine triacetyl deriv/
Prepn must be of high quality, because presence of even small quantities of unacetylated azur /azauridine/ results in catabolism, by intestinal microorganisms, to azauracil, a neurotoxic metabolite. /6-Azauridine triacetyl deriv/
Azaribine used in high doses of 200 mg/kg a day is an effective agent in inducing temporary remissions in patients with severe psoriasis but potentially serious neurotoxicity may occur... /6-Azauridine triacetate/
6-Azauridine triacetate (6-AzUrd-TA) administration causes changes in amino acid metabolism both in experimental animals and in man. This effect is dose-related. Amino acid changes caused by 6-AzUrd-TA resemble those in inborn homocystinuria, beta-alaninemia, and hyperhistidinemia. Inhibition of certain enzymes using pyridoxal phosphate as a coenzyme appears to be the common denominator for these changes. There is supportive evidence suggesting that homocystinemia and thrombotic episodes, both caused by 6-AzUrd-TA, are related... /6-Azauridine triacetate/

C8H11N3O6

245.19

245.064

54-25-1

5901

White to off-white solid powder

2.1±0.1 g/cm3

157-159 °C(lit.)

1.795

-1.96

4

7

2

17

372

4

C1=NN(C(=O)NC1=O)[C@H]2[C@@H]([C@@H]([C@H](O2)CO)O)O

WYXSYVWAUAUWLD-SHUUEZRQSA-N

InChI=1S/C8H11N3O6/c12-2-3-5(14)6(15)7(17-3)11-8(16)10-4(13)1-9-11/h1,3,5-7,12,14-15H,2H2,(H,10,13,16)/t3-,5-,6-,7-/m1/s1

2-[(2R,3R,4S,5R)-3,4-dihydroxy-5-(hydroxymethyl)oxolan-2-yl]-1,2,4-triazine-3,5-dione

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : 25 mg/mL (101.96 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (10.20 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (10.20 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (10.20 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)