April 05, 2021
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Clofazimine is an antibacterial drug that was developed in the 1950s to treat tuberculosis. It failed for that use; but a few years later, it, in combination with other drugs, showed effectiveness against leprosy.

In 1954, clofazimine was synthesized by Vincent C. Barry and co-workers at Trinity College, Dublin. While it was under investigation as a tuberculosis treatment, Y. T. Chang and colleagues at the National Institutes of Health (Bethesda, MD) found that it had activity against Mycobacterium leprae, the bacterium that causes leprosy. Novartis (Basel, Switzerland) launched it as a leprosy treatment in 1969 under the brand name Lamprene. The US Food and Drug Administration approved it as an “orphan drug” in 1986, but it is no longer available in the United States.

In the age of COVID-19, clofazimine may have a new life. Ren Sun, Sumit K. Chanda, Kwok-Yung Yuen, and numerous collaborators at the University of Hong Kong and the Sanford Burnham Prebys Medical Discovery Institute (San Diego), discovered that it kills the SARS-CoV-2 virus in hamster cells. They also showed that the drug reduces the virus’ effects when given before infection.

Clofazimine can be taken as a pill and thus given in outpatient settings. It, in combination with an interferon drug, is currently in Phase 2 trials on patients hospitalized with COVID-19.

Clofazimine hazard information

Hazard class*Hazard statement

Not a hazardous substance or mixture


*Globally Harmonized System of Classification and Labeling of Chemicals.  

Clofazimine fast facts

CAS Reg. No.2030-63-9
2-Phenazinamine, N,5-bis(4-chlorophenyl)-3,5-dihydro-3-[(1-methylethyl)imino]-
Empirical formulaC27H22Cl2N4
Molar mass473.40 g/mol
AppearanceDark red crystals
Melting point210–212 ºC
Water solubility≈0.2 mg/L

MOTW update

Ethyl 2-cyanoacrylate (ECA) was the Molecule of the Week for January 20, 2020. It is the primary active ingredient in most superglues. Recently, a new joint venture between Arkema (Colombes, France) and Cartell Chemical (Minxiong Township, Taiwan) was formed to develop other cyanoacrylate esters that may be useful as engineering adhesives. The first step is to build a plant to make 2-methoxyethyl 2-cyanoacrylate, a derivative that avoids ECA’s deficiencies for industrial use.

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