Here's a fascinating article about off-label use of Campath (from Cambridge Pathology), a monoclonal antibody developed for CLL which was repackaged as Lemtrada, (also known as Campath-1H or alemtuzumab) for the treatment of Multiple Sclerosis. It was approved for that purpose by European regulators in September 2013, but has just been rejected by the FDA in the United States! How often do you hear a doctor say “This deprives people with multiple sclerosis in the United States of an important treatment option that is available throughout Europe, Canada, and Australia.” (Dr. Coles, the first author of two papers describing phase 3 trials of alemtuzumab for Multiple Sclerosis.)
Also note: "The drug (Campath) has several side effects, including nausea, fatigue, fever, and a reduction in white blood cells, which weakens the immune system and makes patients more vulnerable to infections." (my emphasis)
Interesting to observe that what is a side effect in the use of Campath when treating Multiple Sclerosis, is in fact the wanted effect when treating CLL.
Anyone interested in why monoclonal antibodies can help some Multiple Sclerosis patients, may find this rather technical paper "Targeting B Cells in the Treatment of Multiple Sclerosis" of interest. Obviously there is an overlap in the understanding of how B-cells and T-cells interact via cytokines to cause auto-immune diseases like Multiple Sclerosis and how our immunity is impaired by cancerous B-cells in CLL.