Phase 2 CHOICE Study Reports Positive Effects with Daclizumab

Biogen Idec and Facet Biotech Corporation, developers of daclizumab, report that when added to an interferon regimen, this drug reduces the number of new or enlarged MS lesions in patients with active, relapsing forms of MS. Additionally, daclizumab showed an increase in the number of a certain type of cell that helps to regulate the immune system. These results were published in the online edition of The Lancet Neurology and in the April 2010 issue of The Lancet Neurology.

The Phase 2 CHOICE study enrolled 230 patients with “active” relapsing MS (those having at least one relapse or one MS lesion during the past year while on interferon treatment), and who were currently taking an interferon treatment for at least six months prior to enrollment. Participants continued taking their interferon throughout the 24-week study and were given one of three add-on treatments: high-dose daclizumab every two weeks; low-dose daclizumab every four weeks; or placebo. The daclizumab and placebo add-on treatments were administered via subcutaneous injection.

In the high-dose group receiving both daclizumab and interferon treatment, new or enlarged gadolinium contrast-enhancing lesions (those enhanced on MRI with a dye) were reduced by 72 percent, compared to those taking interferon alone. The low-dose group experienced a 25-percent reduction. Daclizumab also resulted in a significant increase (seven-to-eight times the amount) in one type of “natural killer” (or NK) cells, which help to regulate the immune system and are associated with a decrease in disease activity.

Daclizumab is a humanized monoclonal antibody that binds to CD25. This is a receptor that is expressed at high levels on certain immune system cells (non-resting T cells) which may be activated with MS. This experimental treatment is thought to work by selectively targeting immune-system cells which play an important role in the MS process, without depleting “healthy” immune cells needed to help protect against other infections or illnesses.

Common adverse events (or side effects) were similar for individuals taking daclizumab with interferon and those taking a placebo with interferon. The most frequent, more serious adverse events were infections, occurring in 7 percent of the treated patients and 3 percent of the placebo group. All of these infections were resolved with standard therapies.

The developers of daclizumab are conducting a Phase 2b SELECT trial to evaluate the effectiveness and safety of monthly subcutaneous injections of this drug as a single therapy versus a placebo (no other disease-modifying therapies would be given). A Phase 3 DECIDE trial is planned to begin in mid-2010.