Cell based therapies - hematopoietic stem cells

January 4, 2016 James D. Bowen, M.D.

I was fortunate to be able to attend the International Conference on Cell-based Therapies for MS in November. This conference brought together about 70 of the world’s experts on using cells to treat multiple sclerosis. These cells are actually stem cells, and the treatments fall into three categories: hematopoietic, mesenchymal and pleuripotent stem cells.

Stem cells are able to reproduce themselves indefinitely, or they are able to reproduce into many other types of cells. Our bodies use stem cells to renew tissues that are constantly being replaced (skin, blood cells, etc). Unfortunately, the brain has few stem cells so damage from diseases like multiple sclerosis does not get repaired very effectively.

In this blog, I am going to talk about hematopoietic stem cells. These cells are present in small numbers in everybody’s blood and bone marrow. These are the cells that replace our white blood cells, which usually live for only a few days or weeks. We are able to use these cells to give very high doses of immunosuppressive medications to MS patients.

Immunosuppressive medications are medicines that kill rapidly reproducing cells, including lymphocytes. Lymphocytes are believed to be the major part of the immune system that attacks the brain in MS. Lymphocytes are also the cells that help us fight off infections. We are able to give high doses of these immunosuppressive medications to decrease the immune attack on the nervous system in MS.

However, these doses of immunosuppressants can permanently remove almost all the white blood cells from the body. Of course, this would put the patient at high risk of serious infections. What is done to avoid this is to collect hematopoietic stem cells from the blood and store them before the immunosuppressive medication is given. Then, following the immunosuppressive medication, the stem cells can be given back to the patient to repopulate his or her body with white blood cells.

At the conference, leading groups that have done high-dose immunosuppressive therapy followed by stem cell transplantation in MS presented their findings. This included our group at Swedish, Fred Hutchinson Cancer Research Center, University of Washington and other research partners.

These studies all indicate that this therapy may be helpful in MS. It seems to be most useful in those with relapsing disease, being less effective in primary or secondary progressive disease. One problem with these studies is that there is no control arm, so we don’t truly know how well this high-dose immunosuppressive therapy does compared to other treatments.

A workshop at the conference made considerable progress in planning a larger study of this type of high-dose immunosuppressive therapy. The design of this study is quite complicated because of the need to include multiple countries in North America and Europe and the challenges of selecting treatments for the control arm. A control arm with some other treatment is needed in order to determine whether high-dose immunosuppressive therapy is better that other available treatments.

This treatment has potential side effects and it is often not covered by insurance. If we are able to design and conduct a larger trial that has a comparison arm, then we will be able to determine how the treatment stacks up against other existing treatments in both effectiveness and side effects. This will be needed if this treatment is to become more widely available.

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