JEFFREY GREENSTEIN, MD: It's very clear that the individual therapies that we use in multiple sclerosis have limitations. They're not completely effective for all patients, and so what we're looking at are different strategies for treating patients, particularly those who break through and have continued disease activity in spite of being on a single medication.

There are in essence two approaches that one can use. One is to use additional antiinflammatory medications. The other approach is to use drugs that have a totally different mode of action, potentially a neuroprotective agent, although this remains a somewhat theoretical possibility at this point. So the bottom line of it is that we're generally combining antiinflammatory agents to try and get as much benefit as we can with them.

FREDERICK MUNSCHAUER, MD: The medications that we have available now to treat multiple sclerosis, interferons and Copaxone, really represent a major advance, but they do not control the disease completely in many individuals. Therefore, the people who are on one of the interferons or Copaxone may have evidence clinically or by MRI of disease activity.

Over the last few years, we have developed a philosophy of having zero tolerance for disease activity. Like many other diseases, that leads us to the concept of combining medications in order to achieve more complete control of MS.