March 02, 2020
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Baricitinib, a rheumatoid arthritis drug, is under development by Incyte (Wilmington, DE) and Eli Lilly (Indianapolis). It was approved for use under some conditions by the European Union in 2017 and by the US Food and Drug Administration in 2018. Its mechanism of action against rheumatoid arthritis is inhibition of janus kinase enzymes, specifically subtypes JAK1 and JAK2.

Because of current events, baricitinib may have a more urgent application. About a month ago, Justin Stebbing and colleagues at Imperial College London and the artificial intelligence drug discovery company BenevolentAI (London) reported that their AI software turned up an existing drug—baricitinib—that may limit the effects of COVID-19, the coronavirus that is rapidly spreading worldwide.

The researchers used available information about COVID-19 to identify the enzyme adaptor-associated protein kinase 1 (AAK1) as a possible coronavirus target. The AI software then canvassed known AAK1 inhibitors for possible leads to a COVID-19 drug. Baricitinib stood out for its strong affinity for the kinase and its low toxicity.

The authors believe that baricitinib may be able to reduce the ability of the virus to infect lung cells. But they cautioned that their findings should not be considered medical advice; rather, baricitinib could be a clue for other researchers to find treatments for the virus.

Baricitinib hazard information

Hazard class*Hazard statement
Acute toxicity, oral, category 4   H302—Harmful if swallowed.Chemical Safety Warning
Reproductive toxicity, category 1BH360—May damage fertility or the unborn childChemical Safety Warning
Specific target organ toxicity, repeated exposure, category 2H373—May cause damage to organs through prolonged or repeated exposureChemical Safety Warning

*Globally Harmonized System of Classification and Labeling of Chemicals.
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Baricitinib fast facts

CAS Reg. No.1187594-09-7
3-Azetidineacetonitrile, 1-(ethylsulfonyl)-3-[4-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-1H-pyrazol-1-yl]-
Empirical formulaC16H17N7O2S
Molar mass371.42 g/mol
AppearanceWhite crystals or powder
Melting point213–215 ºC
Water solubility<1 g/L

MOTW update: December 7, 2020

Baricitinib is a janus kinase inhibitor that initially showed promise against rheumatoid arthritis. This past February, researchers reported that it may limit the effects of COVID-19 by attacking a specific enzyme in the virus. On November 19, the US Food and Drug Administration issued an emergency use authorization for the combination and remdesivir (MOTW for April 6, 2020) “for the treatment of suspected or laboratory-confirmed COVID-19 in hospitalized adults and pediatric patients two years of age or older requiring supplemental oxygen, invasive mechanical ventilation, or extracorporeal membrane oxygenation.”

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