Description
Launched in the US for relapsing forms of multiple sclerosis (MS), interferon
β-1a is the second compound to be marketed for MS next to interferon p-lb
(Betaseron). This form of p-interferon is a glycosylated polypeptide of 166 amino
acids (sequence identical to human) produced from cultured Chinese hamster ovary
cells containing the engineered human gene for interferon β-1a. The difference in
structure to interferon β-1b lies in the substitution of a cysteine for a serine and in the
fact it is glycosylated. The I b form requires reconstitution and subcutaneous
injection every other day, while the l a form is an intramuscular injection once a week.
The exact mode of action for the β-interferons has not been delineated, however, it is
thought that they reverse a suppressor cell defect and favor the generation of T
helper-2 type responses. It is presumed that the immunoregulatory and antiviral
actions, in addition to the antagonistic effect they have on γ-interferon (γ-interferon
has been shown to exacerbate the symptoms of MS), provide an overall beneficial
effect.
General Description
Interferon beta-1a (recombinant), Avonex, is a glycoproteinwith 166 amino acids. It has a molecular mass of approximately22,000 Da.Interferon beta-1a is indicated for the treatment of relapsingforms of MS. Patients treated with interferon beta-1ademonstrate a slower progression to disability and a less noticeablebreakdown of the blood-brain barrier as observed ingadolinium-enhanced magnetic resonance imaging (MRI). Although the exact mechanism of action of interferonbeta-1a in MS has not been elucidated, it is known that thedrug exerts its biological effects by binding to specific receptorson the surface of human cells. This binding initiatesa cascade of intracellular events that lead to the expressionof interferon-induced gene products.
Adverse effects include flulike syndrome at the start oftherapy that decreases in severity as treatment progresses.Interferon beta-1a is a potential abortifacient and an inhibitorof cytochrome P450.The dosage form is a powder for solution that is reconstitutedin sterile water. Excipients are human albumin,sodium chloride, and phosphate buffer.
