Belimumab is a prescription medication, sold under the brand name Benlysta, that belongs to a class of drugs known as biologics. It is a human monoclonal antibody, a laboratory-made protein designed to target a specific substance in the body. This medication is used as an add-on therapy, meaning it is given in addition to other standard medicines to manage certain autoimmune conditions. Belimumab is not a steroid; it works in a more targeted way to address an underlying process of the disease.
Conditions Treated by Belimumab
Belimumab is approved to treat two specific, related autoimmune conditions. The primary use is for Systemic Lupus Erythematosus (SLE), a disease where the body’s immune system mistakenly attacks its own healthy tissues, causing widespread inflammation and damage in organs like the skin, joints, and blood. It is prescribed for adults and children aged 5 years and older with active SLE.
The medication is also approved for treating active lupus nephritis (LN) in adults and children. Lupus nephritis is a serious complication of SLE that involves inflammation of the kidneys, which can impair their ability to function properly. The treatment helps control the kidney damage caused by the autoimmune attack in patients whose disease remains highly active.
Mechanism of Action
Belimumab functions by targeting a specific protein involved in the body’s immune response called B-Lymphocyte Stimulator (BLyS). In a healthy immune system, BLyS helps regulate the survival and maturation of a type of white blood cell known as a B-cell. These B-cells are responsible for producing antibodies that fight off infections.
In individuals with lupus, the body overproduces BLyS. This excess of BLyS contributes to the survival of “autoreactive” B-cells, which are B-cells that have gone awry. Instead of producing helpful antibodies, these autoreactive cells create autoantibodies that attack the body’s own healthy cells and tissues, leading to the inflammation and organ damage characteristic of lupus.
Belimumab works by binding directly to the soluble BLyS protein. This action blocks BLyS from attaching to its receptors on the surface of B-cells. By preventing this interaction, belimumab inhibits the survival signals that BLyS provides, which in turn reduces the number of circulating B-cells and their differentiation into autoantibody-producing plasma cells.
Administration and Dosing
Belimumab can be administered to patients in two different ways: as an intravenous (IV) infusion or a subcutaneous (under the skin) injection. The IV infusion is given by a healthcare provider in a clinical setting. For both SLE and lupus nephritis, the standard IV dose is 10 mg per kilogram of body weight, administered over about an hour. The initial treatment schedule involves infusions every two weeks for the first three doses, followed by maintenance infusions once every four weeks.
The subcutaneous option allows patients or their caregivers to administer the medication at home after proper training. For adults with SLE, the dose is 200 mg injected once a week. For adults starting treatment for active lupus nephritis, the regimen begins with a loading dose of 400 mg (as two 200 mg injections) once a week for the first four weeks, followed by a maintenance dose of 200 mg once a week.
Potential Side Effects and Safety Information
The most common side effects associated with belimumab include nausea, diarrhea, fever, headache, trouble sleeping (insomnia), and infections like bronchitis or a stuffy nose. When given as a subcutaneous injection, reactions at the injection site such as redness, itching, or swelling can also occur.
Because it suppresses the immune system, belimumab carries a risk of serious infections that could lead to hospitalization or death. Patients should immediately report symptoms like fever, chills, or persistent cough to their doctor. Allergic or hypersensitivity reactions can also occur, sometimes days after administration, and can be severe, causing symptoms like itching, swelling of the face and throat, and trouble breathing.
A significant warning associated with this medication involves mental health. Some patients have reported new or worsening depression, anxiety, and in some cases, thoughts of suicide or self-harm. Another serious, though rare, risk is Progressive Multifocal Leukoencephalopathy (PML), a dangerous brain infection that can lead to severe disability or death. Symptoms of PML include memory loss, confusion, dizziness, loss of balance, and difficulty walking or talking.
Considerations Before and During Treatment
Before beginning treatment with belimumab, patients should disclose their complete medical history to their healthcare provider. This includes any current or past infections, a history of mental health issues like depression, or a history of cancer. It is also important to provide a list of all other medications being taken, including over-the-counter drugs and herbal supplements.
A primary consideration is vaccination status. Patients should not receive live vaccines for 30 days before starting belimumab or at any time during treatment. Live vaccines could cause an infection in someone with a suppressed immune system.
Ongoing monitoring is a standard part of treatment. Regular check-ups allow the healthcare team to assess the drug’s effectiveness and watch for any potential side effects, particularly infections or changes in mood. Patients should also inform their doctor if they plan to become pregnant, as the effects of belimumab during pregnancy are not well understood. Effective contraception is recommended during treatment and for at least four months after the final dose.