How mycophenolate works
LEMS is an autoimmune condition in which the body’s immune system mistakenly attacks the neuromuscular junction, the point where nerve cells and muscles meet.
Mycophenolate is an immunosuppressive agent, meaning that it works to suppress the immune system so as to prevent autoimmune attacks on the neuromuscular junction.
Mycophenolate dampens immune system reactions by blocking the function of inosine monophosphate dehydrogenase (IMPDH). IMPDH is an enzyme that is vital for the synthesis of guanosine nucleotides, especially in T- and B-cells of the immune system. Guanosine nucleotide is one of the building blocks of DNA and RNA molecules. Inhibiting the production of guanosine prevents DNA and RNA synthesis and arrests cell growth.
There are two forms of IMPDH: IMPDH1 and IMPDH2. IMPDH1 is primarily active in normal immune cells for housekeeping purposes, while IMPDH2 is active in immune cells that are dividing. Mycophenolate has a higher preference for blocking IMPDH2, rendering the enzyme nonfunctional to stop the growth and multiplication of the immune cells.
Another mechanism of action described for mycophenolate is the lysis (breaking down) of activated T-cells. Activated T-cells are immune cells programmed to attack a particular target, like nerve cell endings in the case of LEMS. The lysis of these cells prevents them from attacking — launching an immune response — at that specific site.
Mycophenolate in clinical trials
Mycophenolate is primarily used to prevent organ rejection, and its effectiveness has not been assessed in LEMS patients. However, several clinical trials have evaluated its safety and efficacy in treating people with other autoimmune conditions, such as kidney disease associated with systemic lupus erythematosus, Crohn’s disease, and dermatitis. Based on their results, mycophenolate is considered a viable therapeutic option and prescribed to patients with autoimmune conditions that include LEMS.
Multiple clinical studies looked at mycophenolate’s efficacy in preventing organ rejection after a transplant. Positive outcomes from these studies supported its approval (brand name CellCept, by Genentech) to help prevent organ rejection in people undergoing heart, liver or kidney transplants.
Some common side effects of mycophenolate use include:
- Muscle or joint pain
- Stomach pains
- Muscle stiffness
- Difficulty sleeping
- Burning, tingling, or prickling sensation on the skin
Mycophenolate functions by suppressing the immune system, and can lower the body’s ability to fight infection. Therefore, patients taking mycophenolate may develop serious infections.
Mycophenolate may also increase the risk of skin cancer and lymphoma, a cancer that starts in immune cells.
There is a high risk of miscarriage and birth defects due to mycophenolate. For this reason, mycophenolate must not be used by women who are pregnant or planning a pregnancy.
Last updated: July 23, 2019
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