Interferon is a class of cytokines or cell signaling proteins with immune stimulating/modulating activity. Interferons have been found to have an antiviral effect and interfere with a virus' ability to replicate itself.
Type-1 interferons (alpha interferons) constitute a family of more than 25 types (species) including interferon alpha, interferon beta and interferon omega species.
Both natural (human cell-derived) and recombinant (synthetic) interferon products are available.
- The "natural" interferons contain multiple species and subspecies and are produced from human white blood cells (leukocytes).
Recombinant interferons are single subspecies proteins and are genetically engineered.
Recombinant alpha interferons
Approved: interferon alfa-2b or Intron A (Schering-Plough); interferon alfa-2a or Roferon A (Hoffman LaRoche); and interferon alfacon-1 or Infergen, a consensus interferon (Amgen)
In clinical trials: interferon alpha Mochida500 (Mochida). Available in Japan with phase 2 trials in the U.S. The company is also developing a Mochida interferon-beta for hepatitis C treatment.
In preclinical stages: Veldona Oral Alpha-Interferon (Amarillo Biosciences), an oral formula of interferon alpha that is being tested in Egypt; and albuferon, a new protein created by fusing the gene for interferon alpha, to the gene of albumin, producing a protein with properties of both interferon alpha and albumin.
Peglylated recombinant alpha interferon
Approved: peginterferon alfa-2b or Peg-Intron (Schering-Plough)
In clinical trials: peginterferon alfa-2a or Pegasys (Hoffmann-La Roche) is expected to be approved in the U.S. and Europe sometime in 2002. It is currently approved in several countries including Switzerland, Mexico and Venezuela.
Natural (human cell-derived) alpha interferon
In clinical trials: Omniferon Alpha-IF (Viragen) - Viragen believes that natural interferons posses several advantages over synthetic recombinant interferons, hopefully having fewer and less severe side effects. This anti-hepatitis C drug is now in phase 2 clinical trials in Europe. Omniferon will initially be produced in Viragen Europe (Scotland).
Interferon Alfa-n3 or Alferon (Interferon Sciences) -The FDA had recommended against approval for treatment for patients with hepatitis C. Additional phase 3 trials are in progress.
Interferon alfa-n1 (Lymphoblastoid or Wellferon) was approved in 1999 but was abandoned before market launch in the U.S.
Recombinant beta interferon
Approved: interferon beta-1b or Betaseron and interferon beta-1a or Avonex
In clinical trials: Interferon beta-1a or Rebif, received a positive review from FDA, but will not be eligible for FDA approval until 2003.
In clinical trials: Omega Interferon or Biomed 510 (BioMedicines) - The company is trying to develop a product that will target only the liver so that it will be more effective and have fewer side effects than present therapies. Phase 1 testing in has been completed in Germany. Phase 1b/2 clinical testing in patients with hepatitis C has begun at Scripps Clinic and at multiple clinical sites in Europe.
A number of new therapies for hepatitis C are emerging in clinical practice. The combination interferon and ribavirin has proved much more effective than interferon alone, and at this time is considered to be the standard treatment. Trials are being done with combinations of interferon and other substances.
Approved: interferon and ribavirin combined or Rebetron (Schering-Plough)
In clinical trials: Interferon and thymosin alpha-1 or Zadaxin (SciClone). Researchers believe that this synthetic polypeptide, works by boosting the ability of the body's immune system to produce T cells. A trial combining Pegasys with Zadaxin is in progress.
Interferon and granulocyte/monocyte colony stimulating factor (GM-CSF) available on a case-by-case, limited "compassionate use" basis from Schering-Plough.
Interferon and NAC. Oral NAC, although having little effect alone, may enhance the response to interferon.
Interferon and Ofloxacin. Ofloxacin is an antibiotic and is reported to lower ALTs but may not increase the primary virological response rate.
Interferon and VX-497 (Vertex) - An inosine monophosphate dehydrogenase (IMPDH) inhibitor, now in phase 2 clinical trials for the treatment of hepatitis C infection. Blocking IMPDH function prevents viruses from duplicating themselves within host cells.
Interferon triple therapy
In clinical trials: Interferon and ribavirin and amantadine. Amantadine is an antiviral used to prevent certain influenza infections has no effect by itself on viral load. When combined with interferon, it produces a virological response. It is now being used in triple therapy trials.
Histamine dihydrochloride or Ceplene (Maxim). Ceplene, based on the naturally occurring molecule histamine, is designed to prevent or inhibit oxidative stress, thereby reversing immune suppression and protecting critical immune cells. Ceplene is has been used in combination with interferon-alpha or interleukin-2 and ribavirin. In Europe, Mexico and Israel, a controlled, triple-drug phase 2 trial of Ceplene in underway. This study is evaluating the combination of Ceplene with pegylated interferon and ribavirin for the treatment of patients infected with hepatitis C who failed to respond to prior therapy.
Interferon trials are also being done with:
- Re-treatment and longer treatments.
- Different dosage including mega dosing.
- Maintenance dosing (long term).
- Induction dosing (high doses of interferon once a day)
Interferon and iron reduction therapy
One study suggests that using "iron reduction therapy" along with interferon can result in an improved effectiveness rate and that adding cytokines and antivirals such as ribavirin can improve effectiveness even further. The theory behind this is that viruses need iron to replicate, and by reducing the hepatic iron in the liver you prevent replication. This procedure is not FDA approved and trials have proved inconclusive.
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