MS Explained - Future researchThe immune system
Initial experimental therapies for modifying the course of MS were based on attempts to control the activity of the immune system.
The first drug to be licensed was beta interferon - a commercially produced version of a substance that occurs naturally in the immune system. The role of beta interferon is to calm down the immune system once an infection has been dealt with. As a drug it was hoped that this would limit the effect of the immune cells that mistakenly attack the myelin surrounding nerves. Several different beta interferon drugs are now available.
Another drug called glatiramer acetate was developed at the same time as beta interferon. This is a synthetic combination of four molecules that resembles the myelin protein surrounding nerve fibres.
Studies showed that on average both the beta interferon drugs and glatiramer acetate helped to slow the relapse rate of someone with MS by a third and to reduce the severity of those relapses that did still occur.
Attempts to produce more powerful drugs that reduce the immune response further have come up against the problem that this approach is not focussed on any specific part of the system. As a result these drugs can attack aspects of the immune system needed to fight infections as well as the elements that might be involved in MS.
Research has also looked at ways of targeting specific elements within the immune system that play a role in MS, while leaving the remaining immune system intact.
This approach has led to the development of a new class of drugs called monoclonal antibodies. Antibodies are proteins in the immune system that bind onto an invading cell and help to destroy it. Although the body will make millions of copies of an antibody during the immune response, each antibody is targeted at a single type of cell. This means that if antibodies can be identified that bind to cells involved in attacking nerve cells and causing disease activity in MS, maybe drugs can be developed that will only affect those cells.
Monoclonal antibodies are created by cloning a single antibody and this has led to the creation of several new drugs that may be used to treat MS. Examples of monoclonal antibodies include:
- natalizumab (Tysabri), which binds to and disables the area of white blood cells that allows them to cross the blood brain barrier, effectively keeping cells that might attack myelin from coming into contact with the brain or spinal cord
- alemtuzumab (Campath), which binds to proteins on the surface of the white blood cells associated with attacking the myelin on nerves (this drug is still at an experimental stage)
The World Health Organisation's standards for naming drugs means that all monoclonal antibodies end with -mab.
Research into these drugs suggest that they will be more effective than existing treatments at reducing the number of relapses. The research has however shown that there are also more serious side effects and any treatment with these drugs will need to include monitoring for and treatment of these effects.
Future drug development
All of the drugs available so far have to be injected or given intravenously. If taken as tablets, the active ingredients would be digested before they could work. A number of drugs are currently being researched that may be able to provide a disease modifying effect in tablet form.
All of the current drugs treat the relapsing type of MS. Increasingly, research suggests that early, aggressive treatment of MS, effectively before someone is showing any signs of disability, may prevent or greatly reduce subsequent damage from occurring. If treatment is carried out once MS has started to attack and destroy nerve cells, then drugs are much less effective in controlling progression.
The disease modifying drugs work by altering some of the processes within the body that cause MS relapses to happen and thus protect nerves from damage. Unfortunately, the processes that cause MS to become progressive, once nerves have been damaged or destroyed, are less well understood. As yet there are not the same opportunities for drugs to alter or prevent this. A number of different drugs have been, and continue to be, studied as treatments for progressive MS, but any positive results so far have been very modest. Alternative approaches will probably be needed to protect existing nerves and to repair or replace those that have been lost.
- More information from the MS Trust
- Disease Modifying Drug Therapy
- Alemtuzumab (Campath) factsheet
- Natalizumab (Tysabri) - A to Z of MS
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