[medical citation needed] Azacitidine and its deoxy derivative, decitabine (also known as 5-aza-2′-deoxycytidine) were first synthesized in Czechoslovakia as potential chemotherapeutic agents for cancer.

[10] The most common adverse reactions in children with juvenile myelomonocytic leukemia include pyrexia, rash, upper respiratory tract infection, and anemia.

[9] Azacitidine is indicated for the treatment of myelodysplastic syndrome,[4] for which it received approval by the U.S. Food and Drug Administration (FDA) on 19 May 2004.

Azacytosine-guanine dinucleotides are recognized as substrate by the DNA methyltransferases, which catalyze the methylation reaction by a nucleophilic attack.

[4] Based on animal studies and its mechanism of action, azacitidine can cause severe fetal damage.

[4] A study undertaken to evaluate the immediate and long-term effects of a single-day exposure to Azacytidine (5-AzaC) on neurobehavioral abnormalities in mice found, that the inhibition of DNA methylation by 5-AzaC treatment causes neurodegeneration and impairs extracellular signal-regulated kinase (ERK1/2) activation and the activity-regulated cytoskeleton-associated (Arc) protein expression in neonatal mice and induces behavioral abnormalities in adult mice, as DNA methylation-mediated mechanisms appear to be necessary for the proper maturation of synaptic circuits during development, and disruption of this process by 5-AzaC could lead to abnormal cognitive function.

[21] Azacitidine can also cause nausea, vomiting, fevers, diarrhea, redness at its injection sites, constipation, bruising, petechiae, rigors, weakness, abnormally low potassium levels in the bloodstream, and many other side effects, some of which can be severe or even fatal.

[4] The efficacy of azacitidine to treat juvenile myelomonocytic leukemia was evaluated in AZA-JMML-001 (NCT02447666), an international, multicenter, open-label study to evaluate the pharmacokinetics, pharmacodynamics, safety, and activity of azacitidine prior to hematopoietic stem cell transplantation in 18 pediatric patients with juvenile myelomonocytic leukemia.