Immunotherapy Drugs for Myasthenia Gravis
Myasthenia gravis (MG) is a chronic autoimmune disorder that causes certain muscles to become weak, especially after use. There is no cure for MG, but there are several drugs to help treat its symptoms.
Acetylcholinesterase inhibitors are the first type of drug prescribed for people with MG. Acetylcholinesterase inhibitors quickly improve how the nerves transmit signals to the muscles. Some people with MG do not need to take another medicine to keep their symptoms under control.
However, many people with MG also need to take a drug that targets the immune system. These drugs can change how the immune system acts.1
How do immunotherapy drugs work?
Immunosuppressants calm, or suppress, an overactive immune system. There are different forms of immunosuppressant drugs, including steroids and nonsteroidal immunosuppressants.1
Another type of immunosuppressant drug are called immunomodulators. Immunomodulators activate, or change, how the body’s immune system is working.1
Steroids (also called glucocorticoids) are usually the first add-on medicine a doctor will try if a person’s MG symptoms are not well-controlled by an acetylcholinesterase inhibitor. Prednisone is a common steroid often prescribed for people with MG. However, there are dozens of steroids on the market.
Steroids reduce inflammation by suppressing the immune system. This means that the body produces fewer harmful antibodies that attack healthy tissue, but also helpful antibodies needed to fight infections.1
Many people with generalized MG need to take both an acetylcholinesterase inhibitor and a low-dose immunosuppressant long-term. Doctors try to prescribe the lowest steroid dose possible due to the many side effects of long-term use. However, large doses of steroids may be needed to quickly reduce severe symptoms. Large doses of steroids are often given in the hospital so the person can be watched closely.1
Steroids are an old and effective class of drugs used to calm the immune system. However, steroids often have many side effects when used long-term at high doses. That is why many people with MG transition to taking other immunotherapies.
Nonsteroidal immunosuppressants take longer than steroids to control symptoms. Thus, steroids are often combined with another immunotherapy until the immunosuppressant therapy starts working.
Examples of nonsteroidal immunosuppressants include:1
- Azathioprine (brand names Azasan®, Imuran®)
- Cyclosporine (brand names Gengraf®, Neoral®, Sandimmune®)
- Methotrexate (brand names Rheumatrex®, Trexall®)
- Mycophenolate mofetil (brand name Cellcept®)
- Tacrolimus (brand names Astragraf®, Envarsus®, Prograf®)
Biologics are drugs made from living cells. These cells can come from parts of the body including the blood or other tissues. The process of making biologics turns these cells into drugs that can prevent, treat, and cure disease like MG. Examples of some biologics used to treat MG include:
- Eculizumab (brand name Soliris®)
- Rituximab (brand names Rituxan®, Ruxience®, Truxima®)
Possible side effects
Side effects can vary depending on the specific drug you are taking. The most common side effects of immunosuppressants in general include:1
- Increased risk of infection
Other side effects may be more common to one type of immunosuppressant than another, and include:1
- Cushing’s syndrome (redistribution of body fat)
- Avascular necrosis (bone tissue death) in the hips and knees
- High blood pressure
- Osteoporosis (weakening of bones)
- Skin thinning and easy bruising
- Weight gain due to increased appetite
None of these drugs is likely to cause all of these side effects. The chance of a side effect depends on many factors, including the dose you take and the type of immunosuppressant you take.
These are not all the possible side effects of MG treatments. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with immunosuppressant drugs.
When are they prescribed
Immunotherapies are sometimes used in combination with steroids. Other times they are used to replace steroids. Generally these drugs are given to people with MG who:1
- Need more symptom control than steroids are providing
- Need to lower the amount or stop taking steroids altogether due to side effects
Nonsteroidal immunotherapies are more difficult to give to the patient and are more expensive than steroids. Each has different potential benefits and side effects.
Certain immunosuppressants are known to work better in some types of people with myasthenia gravis than others. For example:1
- Azathioprine may be used in pregnant women with MG if her acetylcholinesterase inhibitor and a steroid do not fully control muscle weakness
- Older adults, especially those with kidney issues, may be given azathioprine or mycophenolate mofetil, instead of steroids
- Cyclosporine is usually not given to older adults with kidney issues due to potential kidney issues
- Rituximab and eculizumab may be used in people with refractory MG or severe disease
There are many other immune system drugs that may be prescribed off-label to people with MG. The theory is that these other immunosuppressants work for other autoimmune conditions and may also work for people with MG.1
Things to note
Most people with MG need to take a combination of an acetylcholinesterase inhibitor, a steroid, an immunotherapy drug, and/or a biologic. This is partly because these drugs attack muscle weakness in different ways and work at different speeds. And like everything else about myasthenia gravis, every person responds to a different combination of medicines.1
For example, an acetylcholinesterase inhibitor begins to improve muscle weakness in 10 to 15 minutes, while plasma exchange takes days. A steroid begins to take effect in 2 to 3 weeks, and an immunosuppressant takes 6 months to a year. Thymectomy surgery improves symptoms after years.1
While taking immunosuppressants, it is important to avoid crowds and people with contagious diseases and wash your hands often.1
Other immune system treatments for MG
Two other treatments that help suppress the immune system include plasma exchange and IVIG (intravenous immune globulin). Plasma exchange is also called plasmapheresis. These treatments may be used to give steroids and other immune system drugs time to begin working.1
Before beginning treatment for myasthenia gravis, tell your doctor about any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.