Rilonacept, marketed under the brand name ARCALYST®, is a biologic medication designed to manage specific inflammatory conditions. It is a targeted therapy, meaning it does not broadly suppress the immune system but instead focuses on a particular component involved in generating inflammation. This medication is prescribed for rare and persistent autoinflammatory diseases that are driven by a specific type of protein overproduction.
Conditions Treated by Rilonacept
Rilonacept is approved by the U.S. Food and Drug Administration (FDA) for a select group of inflammatory conditions. One of its primary uses is for the treatment of Cryopyrin-Associated Periodic Syndromes (CAPS). CAPS are a group of rare, inherited autoinflammatory diseases that cause uncontrolled inflammation. Rilonacept is indicated for two conditions within the CAPS spectrum: Familial Cold Autoinflammatory Syndrome (FCAS) and Muckle-Wells Syndrome (MWS). It is approved for use in adults and children 12 years and older.
In patients with FCAS, exposure to cold temperatures can trigger episodes of fever, rash, and joint pain. Those with MWS experience similar symptoms that may be more chronic and can lead to hearing loss and kidney damage over time. Rilonacept helps manage the underlying inflammation that drives these debilitating symptoms.
The other main indication for rilonacept is the treatment of recurrent pericarditis (RP) for patients aged 12 and older. Pericarditis is the inflammation of the pericardium, the thin, sac-like membrane that surrounds the heart. When this inflammation returns after an initial episode has resolved, it is considered recurrent. Rilonacept is used not only to treat the active inflammation of an RP episode but also to reduce the risk of future episodes, helping to maintain remission.
Mechanism of Action
The way rilonacept works involves targeting a specific signaling protein, or cytokine, called Interleukin-1 (IL-1). In a healthy immune system, IL-1 plays a part in the body’s normal inflammatory response to infection or injury. It acts like a messenger, binding to receptors on various cells to signal the start of an inflammatory cascade. This process helps protect the body, but when it becomes dysregulated, it can cause harm.
In conditions like CAPS and recurrent pericarditis, the body produces an excessive amount of IL-1. This overproduction leads to the chronic and recurrent inflammation that characterizes these diseases. Specifically, rilonacept is designed to block both IL-1 alpha and IL-1 beta, the two forms of this cytokine.
Rilonacept functions as a decoy receptor, intercepting IL-1 before it can deliver its inflammatory message. The medication is a fusion protein that effectively traps IL-1 molecules, neutralizing them. By binding to IL-1 alpha and IL-1 beta, rilonacept prevents these cytokines from attaching to their true cellular receptors, thereby blocking the downstream inflammatory signaling.
Administration and Dosing
Rilonacept is administered as a subcutaneous injection, meaning it is injected into the fatty tissue just under the skin. Patients or their caregivers are trained by a healthcare professional on how to properly prepare and administer the injection at home. This includes learning the correct technique for injection and how to rotate injection sites to avoid irritation.
The dosing schedule for rilonacept begins with a higher “loading dose” to quickly establish a therapeutic level of the medication in the body. For adults with CAPS or recurrent pericarditis, this involves a one-time dose of 320 mg. Following the initial dose, treatment continues with a smaller weekly maintenance dose of 160 mg.
Dosages can be adjusted based on the specific condition and the patient’s age and weight. For pediatric patients between 12 and 17 years old, both the loading and weekly maintenance doses are calculated based on their body weight, with a maximum dose limit. Proper storage of rilonacept is also important; it must be refrigerated and protected from light.
Side Effects and Safety Information
The most frequently reported side effects associated with rilonacept treatment are reactions at the injection site and upper respiratory tract infections. Injection site reactions may include redness, swelling, itching, or pain where the drug was administered. These reactions are mild to moderate and decrease over time as the body adjusts to the medication. Upper respiratory infections, such as the common cold, may also occur more often.
A more significant consideration with rilonacept is its effect on the immune system. Because the medication works by blocking IL-1, a component of the immune response, it can lower the body’s ability to fight infections. This can increase a patient’s susceptibility to developing serious infections. Therefore, treatment with rilonacept should not be started in individuals who have an active or chronic infection. If a serious infection develops during treatment, the medication is discontinued until the infection resolves.
Certain safety precautions are necessary before and during therapy with rilonacept. Healthcare providers will screen patients for latent tuberculosis (TB) before they begin treatment. If a latent TB infection is found, it must be treated before the patient can start taking rilonacept. Additionally, patients receiving rilonacept should not be given live vaccines, as their suppressed immune system may not be able to mount a proper response, potentially leading to infection from the vaccine virus itself.