Interferons are classed as immunomodulators although their exact mechanism of action in MS is unknown. Pegylation (attachment of a molecule to polyethylene glycol) prolongs the circulation time in the body, allowing less frequent dosing.
Plegridy is administed by subcutaneous injection every 2 weeks. To reduce the incidence and severity of adverse events, it is recommended that the dose be titrated up to the recommended level. Patients should initiate treatment with a dose of 63 microgram, followed by 94 microgram at week 2, then the full dose of 125 microgram at week 4 and every 2 weeks thereafter.
Prophylactic and concurrent use of anti-inflammatory, analgesic and/or antipyretic treatments can be considered to minimise flu-like symptoms associated with interferon treatment.
Reduced relapse rate
Peginterferon beta-1a was shown to reduce the rate of relapse in a double-blind, randomised trial (ADVANCE) in 1,516 patients with relapsing-remitting MS.
After 48 weeks of treatment with peginterferon beta-1a 125 microgram every 2 or 4 weeks, patients in the 2-weekly dosing group showed significantly fewer relapses than those given placebo, with an annualized relapse rate (primary endpoint) of 0.256 (95% CI 0.206-0.318) compared with 0.397 (95% CI 0.328-0.481; p=0.0007). This difference reflected a 36% reduction in annualized relapse rate.
The annualized relapse rate in the 4-weekly dosing group did not differ significantly from that in the placebo group (0.288, 95% CI 0.234-0.355, p=0.0114).
Post hoc analysis showed that the risk of sustained disability at 24 weeks was significantly reduced by 54% (p=0.0069) with 2-weekly dosing of peginterferon beta-1a.
The efficacy of peginterferon beta-1a was maintained over the second year of treatment.
The most commonly reported adverse effects of peginterferon beta-1a were injection site reactions, flu-like illness, pyrexia, headache, myalgia, chills and arthralgia.
Further information: Biogen