- Biogen and AbbVie last week won FDA approval for their new multiple sclerosis treatment Zinbryta (daclizumab), but safety risks prompted the regulator to require a boxed warning and restrict distribution.
- Administered by the patient once a month, Zinbryta is a monoclonal antibody which binds to a subunit of the IL-2 receptor on activated lymphocytes—cells believed to be involved in the biology of MS.
- But the drug can cause severe liver injury and immune conditions and the FDA recommended monitoring of patient liver function prior to, during, and after treatment with Zinbryta. Zinbryta will carry a black-box warning for these risks.
Zinbryta will add to Biogen's portfolio of MS treatments, which is headlined by the blockbusters Tecfidera and Avonex. The two drugs combined to account for 68% of Biogen's revenue last year, although that share declined from 2014.
Biogen recently decided to spin off its hemophilia business into a separate company—a move Biogen described as enabling it to better focus on its neurological treatments.
Zinbryta's efficacy in reducing annualized relapse rates was shown to be comparable, or slightly better, than standard-of-care Avonex in two late-stage studies.
The two trials collectively included 2,400 subjects with relapsed MS. In one 144-week trial, patients were randomized to receive either Avonex or Zinbryta. Overall, patients on Zynbryta had fewer clinical relapses than Avonex-treated patients. In the second 52-week study, Zynbryta was tested against a placebo and also demonstrated fewer relapses.
But the safety risks could limit uptake. The FDA recommended Zinbryta only for patients who have had inadequate responses to two or more MS drugs and mandated a boxed warning detailing the liver and immune condition risks.
Additionally, Zinbryta will only be available through a restricted distribution program as part of a risk evaluation and mitigation process.