For the treatment of chronic hepatitis C and for respiratory syncytial virus (RSV).
Ribavirin is an anti-viral drug active against a number of DNA and RNA viruses. It is a member of the nucleoside antimetabolite drugs that interfere with duplication of the viral genetic material. The drug inhibits the activity of the enzyme RNA dependent RNA polymerase, due to it's resemblence to building blocks of the RNA molecules. The oral form is used in the treatment of hepatitis C, in combination with interferon drugs. The aerosol form is used to treat respiratory syncytial virus-related diseases in children. The primary serious adverse effect of ribavirin is hemolytic anemia, which may worsen preexisting cardiac disease.
Mode of Action:
Ribavirin is readily phosphorylated intracellularly by adenosine kinase to ribavirin mono-, di-, and triphosphate metabolites. Ribavirin triphosphate (RTP) is a potent competitive inhibitor of inosine monophosphate (IMP) dehydrogenase, viral RNA polymerase and messenger RNA (mRNA) guanylyltransferase (viral) and can be incorporated into RNA in RNA viral species.. Guanylyltranserase inhibition stops the capping of mRNA. These diverse effects result in a marked reduction of intracellular guanosine triphosphate (GTP) pools and inhibition of viral RNA and protein synthesis. Ribavirin is also incorporated into the viral genome causing lethal mutagenesis and a subsequent decrease in specific viral infectivity.
Hepatic. Results of in vitro studies using both human and rat liver microsome preparations indicated little or no cytochrome P450 enzyme-mediated metabolism of ribavirin, with minimal potential for P450 enzyme-based drug interactions. Ribavirin has two pathways of metabolism: (1) a reversible phosphorylation pathway in nucleated cells; and (2) a degradative pathway involving deribosylation and amide hydrolysis to yield a triazole carboxylic acid metabolite.
Side effects include "flu-like" symptoms, such as headache, fatigue, myalgia, and fever. The LD50 in mice is 2 g/kg orally and is associated with hypoactivity and gastrointestinal symptoms (estimated human equivalent dose of 0.17 g/kg, based on body surface area conversion).
Sidwell RW, Bailey KW, Wong MH, Barnard DL, Smee DF: In vitro and in vivo influenza virus-inhibitory effects of viramidine. Antiviral Res. 2005 Oct;68(1):10-7. Pubmed Sidwell RW, Huffman JH, Khare GP, Allen LB, Witkowski JT, Robins RK: Broad-spectrum antiviral activity of Virazole: 1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide. Science. 1972 Aug 25;177(50):705-6. Pubmed Alvarez D, Dieterich DT, Brau N, Moorehead L, Ball L, Sulkowski MS: Zidovudine use but not weight-based ribavirin dosing impacts anaemia during HCV treatment in HIV-infected persons. J Viral Hepat. 2006 Oct;13(10):683-9. Pubmed Bani-Sadr F, Carrat F, Pol S, Hor R, Rosenthal E, Goujard C, Morand P, Lunel-Fabiani F, Salmon-Ceron D, Piroth L, Pialoux G, Bentata M, Cacoub P, Perronne C: Risk factors for symptomatic mitochondrial toxicity in HIV/hepatitis C virus-coinfected patients during interferon plus ribavirin-based therapy. J Acquir Immune Defic Syndr. 2005 Sep 1;40(1):47-52. Pubmed
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