An IL-17 inhibitor is a type of biologic medication engineered to target a specific part of the immune system. Instead of broadly suppressing immune function, these drugs selectively calm a pathway involved in inflammation. This targeted approach allows for precise intervention in the inflammatory processes that drive certain autoimmune diseases.
The Role of Interleukin-17 in Inflammation
Interleukin-17 (IL-17) is a cytokine, a signaling protein that immune cells use to communicate. IL-17 helps protect the body against certain pathogens, like fungi and bacteria. It recruits specific immune cells to the site of an infection to help clear it.
In certain autoimmune diseases, the immune system becomes dysregulated and produces an excess amount of IL-17. The constant presence of high IL-17 levels sends a continuous signal for inflammation, even without an infection. This chronic signaling leads to persistent inflammation that can damage the body’s own tissues.
An IL-17 inhibitor interrupts this faulty communication. These medications are monoclonal antibodies, which are lab-created proteins designed to bind to a specific target. Some inhibitors bind directly to the IL-17A protein, while others block the receptor on cells that IL-17 attaches to. By blocking this connection, the drug stops the inflammatory message from being delivered, reducing chronic inflammation.
Conditions Treated with IL-17 Inhibitors
IL-17 inhibitors are prescribed for several autoimmune conditions characterized by chronic inflammation.
- Moderate to severe plaque psoriasis: In this condition, excess IL-17 drives the rapid growth of skin cells, leading to thick, red, scaly patches. Inhibitors slow skin cell production and reduce the severity of these lesions.
- Psoriatic arthritis: This form of inflammatory arthritis attacks the joints, causing pain, stiffness, and swelling that can lead to permanent damage. These drugs alleviate joint symptoms by reducing the underlying inflammation.
- Ankylosing spondylitis: This is a type of arthritis that primarily affects the spine, where inflammation can lead to chronic pain and stiffness. In severe cases, parts of the spine can fuse, and these inhibitors help improve pain and maintain flexibility.
- Non-radiographic axial spondyloarthritis: Patients experience inflammatory back pain similar to ankylosing spondylitis, but joint damage is not yet visible on X-rays. IL-17 inhibitors are used to control inflammation and symptoms.
Available IL-17 Inhibitor Medications
Several IL-17 inhibitor medications are available, including Cosentyx (secukinumab) and Taltz (ixekizumab). Both of these drugs work by binding directly to and neutralizing the IL-17A cytokine. Another medication, Siliq (brodalumab), functions differently by blocking the IL-17 receptor on cells.
Potential Side Effects
Because IL-17 inhibitors modulate the immune system, the most common side effects are related to a tempered immune response. These include an increased frequency of upper respiratory infections like the common cold. Headaches and reactions at the injection site, such as redness or swelling, are also common.
A specific risk of targeting the IL-17 pathway is an increased susceptibility to certain infections. Since IL-17 helps defend against fungi, patients taking these inhibitors have a higher risk of developing fungal infections. These are often candidiasis (yeast infections) of the mouth, throat, or skin, requiring careful monitoring.
These medications have been linked to new or worsening inflammatory bowel disease (IBD), like Crohn’s disease or ulcerative colitis. Patients are screened for a history of IBD before starting treatment and must report new gastrointestinal symptoms.
The medication Siliq (brodalumab) carries a black box warning, the FDA’s most serious, for an observed risk of suicidal ideation and behavior. Patients prescribed Siliq must be enrolled in a Risk Evaluation and Mitigation Strategy (REMS) program. This ensures they are aware of and monitored for this risk.
Administration and Medical Monitoring
IL-17 inhibitors are biologic drugs made from large proteins and cannot be taken as an oral pill. They are administered as a subcutaneous injection into the fatty tissue just under the skin. Patients are often trained to perform these injections at home using a prefilled syringe or auto-injector pen. The frequency of these injections varies depending on the specific medication and the initial loading dose schedule.
Before beginning treatment, medical monitoring is required to ensure safety. Screening for latent tuberculosis (TB) is necessary, as suppressing the immune system can activate a dormant infection. This screening is done with a skin or blood test.
Once treatment starts, ongoing follow-up with a healthcare provider is necessary. These appointments allow the doctor to assess the treatment’s effectiveness and monitor for potential side effects. This includes watching for signs of infection and ordering periodic blood work to check for any issues.