Biologic agents are different than drugs. While drugs are created chemically, biologics are created biologically. Hormones, insulin, and red blood cell-stimulating products are examples of biologic agents that have been used in medicine for decades. Recent technology has provided the means to create other very large, complex molecules that target specific parts of the immune system.
Keep in mind that all biologic agents used to treat myositis diseases suppress the immune system’s response to germs (bacteria, viruses, and other organisms), and therefore place the patient at an increased risk for serious infection. Biologic agents may also increase the risk of developing certain types of cancer, especially in older adults.
The following biologic agents are currently used to treat myositis diseases.
Rituximab (Rituxan) is a monoclonal antibody that targets B cells, a type of immune system cell that produce antibodies that destroy specific antigen cells. It was developed as a treatment for certain types of cancer, but B cells also play a role in inflammation, and it has been approved for use in rheumatoid arthritis and other autoimmune diseases. It has shown promise in treating myositis diseases, especially in those whose disease does not respond well to other treatments. Patients with anti-SRP necrotizing myopathy, for example, which can be refractory, are more likely to respond to rituximab.
Rituximab is not used as first- or second-line treatment, however, because it poses higher risks of severe side effects. Patients may have an acute infusion reaction that causes a rash, itchiness, low blood pressure, shortness of breath, and in rare cases, cardiac arrest. This medication may also cause severe long-term immunosuppression, which can cause life-threatening infections and other serious conditions. Patients considering this medication should be screened for tuberculosis (TB), hepatitis B and C, and HIV before starting it.
Rituximab is given intravenously at a dose of up to 1gm, with a second dose in two weeks. It can take up to three months for symptoms to respond to rituximab, and it continues to have an effect in the body for as long as six months. If rituximab does seem to be effective, these doses can be repeated every 6 to 18 months.
Tocilizumab (Actemra) is a monoclonal antibody against the interleukin-6 receptor (IL-6R), which plays an important role in immune response and is implicated in the pathogenesis of many autoimmune diseases. It is approved for use in rheumatoid arthritis.
The recommended dose of tocilizumab is 4-8 mg/kg administered as a single 60-minute intravenous infusion every 4 weeks. It can also be self-administered subcutaneously (under the skin).
Side effects include headache, runny nose and sneezing, high blood pressure, and possible liver complications.
Abatacept (Orencia) is a modified antibody that interferes with the immune activity of T cells. It is used to treat rheumatoid arthritis. In myositis, it is being tested for use in patients with refractory dermatomyositis and polymyositis.
Dosage of abatacept is based on weight, and the medication is administered by intravenous infusion over 30 minutes. I can also be self-administered subcutaneously (under the skin).
Ajulemic acid (Lenabasum) is a synthetic oral, non-psychoactive endocannabinoid-mimetic drug that provides pain relief and anti-inflammation effects. It is not an immune system suppressant, so it does not cause a higher risk for developing infection.
Ajulemic acid is being tested as a treatment for dermatomyositis patients with severe skin involvement. Initial clinical trials have shown promising results.
Side effects include dry mouth, tiredness, and dizziness.
Etanercept (Enbrel) is a tumor necrosis factor (TNF) inhibitor. It is approved for treating rheumatoid arthritis and other autoimmune diseases.
Etanercept can be self-administered by subcutaneous (under the skin) injection. It is usually injected once a week.
Side effects may include headache, nausea, vomiting, heartburn, stomach pain, weakness, or cough.
Infliximab (Remicade) is a chimeric monoclonal antibody that works against tumor necrosis factor alpha (TNF-α) and is approved to treat rheumatoid arthritis and other autoimmune diseases.
Infliximab is administered by intravenous infusion, usually every 6-8 week.
Side effects include stuffy nose, sinus pain, headache, mild stomach pain, skin rash, or flushing (warmth, redness, or tingly feeling).