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.
