What Does Kesimpta Treat?

Kesimpta (ofatumumab) is a prescription medication for relapsing forms of multiple sclerosis (MS) in adults. This includes clinically isolated syndrome, relapsing-remitting MS, and active secondary progressive disease. It is a biologic that targets specific immune cells to reduce MS relapses and slow disability progression.

What Does Kesimpta Treat?

Kesimpta treats relapsing forms of multiple sclerosis. Relapsing MS means people have flare-ups (relapses) where new or worsening symptoms appear, followed by periods of recovery. Over time, repeated relapses can lead to lasting disability. Kesimpta reduces the number of these attacks and helps slow the accumulation of disability. It is not used for primary progressive MS, where symptoms steadily worsen from the start without clear relapses.

MS is an autoimmune disease where the immune system mistakenly attacks the protective coating (myelin) around nerve fibers in the brain and spinal cord. This damage disrupts communication between the brain and the body. By calming a specific part of the immune system, Kesimpta helps protect the myelin and reduce the inflammation that drives relapses.

How Does Kesimpta Work?

Kesimpta belongs to a class of drugs called monoclonal antibodies. It targets and binds to a protein called CD20 found on the surface of B cells, a type of immune cell. Once bound to CD20, Kesimpta marks these B cells for destruction by the body’s own immune system. B cells contribute to MS by producing antibodies and activating other immune cells that attack myelin. By lowering the number of B cells, Kesimpta reduces the overall inflammatory attack on the nervous system.

This is not a permanent removal. B cells gradually return over time after treatment stops. The goal is to keep B cell levels low enough to prevent relapses while the body still has enough immune reserve to fight infections. Unlike some older MS treatments that suppress a broad range of immune cells, Kesimpta targets only B cells, leaving other immune cells largely alone.

Who Is a Candidate for Kesimpta?

Kesimpta is approved for adults with relapsing forms of MS. A neurologist typically determines if it is appropriate based on the type of MS, disease activity, and other health factors. People with active hepatitis B infection or untreated tuberculosis should not start Kesimpta until those infections are resolved or properly managed. Live vaccines should be given at least four weeks before starting treatment because Kesimpta can weaken the response to vaccines.

Women who are pregnant, planning pregnancy, or breastfeeding should discuss risks with their doctor. Kesimpta may cross the placenta in the second and third trimesters and could affect the baby’s developing immune system. There is a pregnancy registry that monitors outcomes. Men considering fatherhood should also talk with their doctor about any potential effects, though current evidence does not show specific risks to male fertility.

How Is Kesimpta Administered?

Kesimpta is given as a shot under the skin (subcutaneous injection). It comes in a pre-filled syringe or autoinjector that patients can use at home after proper training from a healthcare provider. The first three doses are given weekly to quickly lower B cell levels. After that, maintenance dosing is once every four weeks. Each injection is 20 mg.

The dosage schedule is fixed and does not need adjustment based on weight. If a dose is missed, it should be taken as soon as possible, and the next dose scheduled accordingly. People are advised to rotate injection sites to reduce skin reactions, using the abdomen, thigh, or upper arm.

What Are the Common Side Effects?

The most frequent side effect is injection-related reactions, such as redness, swelling, pain, or itching at the injection site. These reactions usually happen within 24 hours and tend to decrease with repeated doses. Taking an antihistamine or acetaminophen beforehand can help manage symptoms, but this should be discussed with a doctor first.

Kesimpta increases the risk of upper respiratory tract infections, including sinusitis and the common cold. Serious infections like pneumonia or herpes zoster (shingles) can occur, though less often. Because it lowers B cells, the immune system is less able to mount a strong antibody response to infections. People should report any signs of infection promptly, such as fever, cough, or pain with urination.

Other possible side effects include headache, back pain, and nausea. Rare but serious risks include allergic reactions (anaphylaxis) and a condition called progressive multifocal leukoencephalopathy (PML), though PML is extremely rare with Kesimpta and has mostly been seen with other B-cell–depleting drugs. There is also a theoretical risk of hepatitis B reactivation, which is why screening is done before starting treatment.

How Effective Is Kesimpta Compared to Other MS Treatments?

In a large Phase 3 clinical trial, Kesimpta was compared directly to teriflunomide (Aubagio), an oral MS medication. People taking Kesimpta had significantly fewer relapses and were less likely to have new lesions on MRI scans over a two-year period. Kesimpta also showed a reduction in confirmed disability progression compared to teriflunomide. These findings place Kesimpta among the more effective disease-modifying therapies for relapsing MS.

However, effectiveness varies by individual. Some people may need to try more than one medication before finding the best fit. Kesimpta is not considered a first-line for everyone; a neurologist weighs factors like disease severity, previous treatments, side effect tolerance, and patient preference. It is generally well tolerated, but because it is a newer therapy, long-term data beyond six years is still being collected.

Are There Alternatives to Kesimpta?

Several other disease-modifying therapies exist for relapsing MS. They include oral medications like fingolimod (Gilenya), dimethyl fumarate (Tecfidera), and infusion therapies like ocrelizumab (Ocrevus) or natalizumab (Tysabri). Kesimpta and Ocrevus both target CD20 on B cells, but Ocrevus is given by IV infusion every six months, while Kesimpta is a monthly self-injection. Some people prefer the convenience of home injection over clinic visits for infusions.

Each MS medication has a different safety profile, monitoring schedule, and effectiveness. For example, natalizumab carries a higher risk of PML, especially in people who have had the JC virus. Kesimpta does not require routine MRIs to monitor for PML, but it does not eliminate the risk entirely. The choice of treatment should be a shared decision between the patient and neurologist.

What Precautions Are Needed During Treatment?

Before starting Kesimpta, doctors usually check for hepatitis B, tuberculosis, and other chronic infections. Blood tests for IgG levels and immunoglobulins may be done periodically. Vaccinations should be updated at least four weeks prior, especially flu, pneumonia, and COVID-19 vaccines. Live vaccines (such as MMR, yellow fever, or live shingles vaccine) should be avoided during treatment and for a period after stopping.

People on Kesimpta should be monitored for infections throughout treatment. If a serious infection develops, the drug may be paused until the infection resolves. There is also a small risk of decreased antibody levels over time, which could increase infection risk further. Patients should alert their doctor before receiving any other vaccines or surgeries.