Ofatumumab
Pronunciation: oh-fa-TOOM-oo-mab.
- Generic name
- ofatumumab
- Brand names
- Kesimpta
- Drug class
- CD20-directed cytolytic monoclonal antibody
- Form
- Not established from the sources reviewed: specific device/product-presentation format was not established in the sources reviewed for this page beyond patient self-administered subcutaneous injection after training.
- Route
- Subcutaneous injection
- Legal status
- Prescription-only biologic medicine
Availability and supply rules vary by country
Trade names by country: United States · Canada
Australia: · Full directory
What ofatumumab is and how it works
Ofatumumab (Kesimpta) is a biologic medicine (CD20-directed cytolytic monoclonal antibody) approved for treating relapsing forms of multiple sclerosis (MS) in adults. (1)
It is a self-administered subcutaneous injection given monthly after initial loading doses. A healthcare professional must provide training and supervise the first injection.
Mechanism of action: how ofatumumab works
Ofatumumab is a CD20-directed cytolytic monoclonal antibody. Not established from the sources reviewed: the detailed mechanism and disease-activity effect were not established in the sources reviewed for this page beyond the approved indication. (1)
What ofatumumab is used for
Relapsing forms of multiple sclerosis
Indicated for adults with relapsing forms of MS, including clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease. (1)
Before taking ofatumumab
Do not take / not appropriate for
- Do not receive ofatumumab if you have an active hepatitis B virus infection. (Kesimpta (this product)) (1)
- Do not receive if you have a history of life-threatening hypersensitivity to ofatumumab or a life-threatening injection-related reaction to Kesimpta. (Kesimpta (this product)) (1)
Tell your clinician about
- All current or recent infections, fever, or illness; treatment may need to be delayed.
- History of hepatitis B or liver problems, including any previous treatment for hepatitis.
- Vaccination history and whether you are due for any live vaccines.
- Pregnancy, plans for pregnancy, or breastfeeding; effective contraception is required during treatment and for 6 months after stopping.
- All medicines you are taking, including over-the-counter and supplements.
How to take ofatumumab
- Loading phase: 20 mg subcutaneous injection at Weeks 0, 1, and 2.
- Maintenance phase: 20 mg subcutaneous injection every month starting at Week 4.
- The first injection must be performed under the guidance of a healthcare professional.
- After proper training, subsequent injections can be self-administered at home.
- Do not change the dose or schedule yourself; any changes must be directed by your prescriber.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician.
Missed dose
Contact your treatment team if a dose is delayed or missed. Do not take an extra dose or change the dosing interval yourself; no specific rescheduling rule was established in the sources reviewed for this page.
Overdose
If overdose is suspected, seek urgent medical evaluation. (1)
Side effects
The most common side effects are upper respiratory tract infections, injection-related reactions, and headache. Serious infections and liver problems can occur. Most injection reactions are mild to moderate and happen within 24 hours of the first injection.
Upper respiratory tract infection
What to notice: Signs of an upper respiratory tract infection.
What to do: Contact your healthcare provider if symptoms persist or worsen. (1)
Systemic injection-related reaction
What to notice: Signs of a systemic injection-related reaction occurring within 24 hours after injection.
What to do: Most are mild to moderate. If severe or persistent, inform your treatment team. (1)
Headache
What to notice: New or worsening headache.
What to do: Discuss with your healthcare provider if troublesome. (1)
Local injection-site reaction
What to notice: Redness, swelling, itching, or pain at the injection site.
What to do: Usually mild; report to your treatment team if severe or spreading. (1)
Signs of serious infection
What to notice: Fever, persistent cough, body aches, or other signs of infection.
What to do: Contact your healthcare provider promptly; treatment may need to be delayed. (1)
Liver injury
What to notice: Signs of liver injury.
What to do: Seek prompt medical assessment and liver function tests. (1)
Progressive multifocal leukoencephalopathy (PML)
What to notice: Signs suggestive of PML, such as new or worsening neurological symptoms.
What to do: Contact your healthcare provider immediately; PML is a serious brain infection. (1)
Serious warnings
Severe hypersensitivity / anaphylaxis — emergency
Symptoms: Signs of a severe hypersensitivity reaction.
Action: Seek emergency medical attention immediately. (1)
Serious infections — urgent
Symptoms: Signs of a serious infection.
Action: Contact your healthcare provider right away; treatment may need to be interrupted. (1)
Hepatitis B virus reactivation — urgent
Symptoms: Signs of hepatitis B reactivation.
Action: Contact your healthcare provider; this risk exists even if you previously had resolved hepatitis B infection. (1)
Progressive multifocal leukoencephalopathy (PML) — emergency
Symptoms: New or worsening neurological symptoms.
Action: Seek emergency medical evaluation and inform them you are on ofatumumab. (1)
Interactions
| Medicine or test | Effect | Action |
|---|---|---|
| Live vaccines | Live vaccines may cause serious infection if given while B cells are depleted. Live vaccines should be administered at least 4 weeks before starting Kesimpta and must be avoided during treatment and until B-cell recovery. | Discuss any planned vaccines, live or non-live, with your healthcare provider before starting therapy. (1) |
Pregnancy, breastfeeding, kidney/liver function, age
Pregnancy
May cause fetal harm based on animal data. Females of reproductive potential must use effective contraception during treatment and for 6 months after the last dose. If you become pregnant, inform your healthcare provider immediately. (1)
Breastfeeding
It is unknown whether ofatumumab is excreted in human milk. IgG antibodies are known to be present in breast milk, so a risk to the nursing infant cannot be excluded. Discuss the benefits and risks with your doctor. (1)
Children and adolescents
Safety and effectiveness in pediatric patients have not been established in the sources reviewed for this page. (1)
Monitoring
Before starting
- Screen for hepatitis B virus before starting treatment.
- Obtain baseline liver function tests.
- Review vaccination history; live vaccines are given at least 4 weeks prior when needed.
- Confirm no history of a life-threatening injection reaction to ofatumumab.
During treatment
- Monitor immunoglobulin levels, particularly IgM, during treatment.
- Assess liver function as clinically indicated.
- Watch for new or worsening neurological symptoms that could suggest PML.
Storage
Follow the exact product label and keep medicines away from children.
Professional information
Clinician-facing context only. Use the current local indication, dosing, and safety information. This summary is based on US prescribing information for the MS indication.
United States
Indication: Relapsing forms of multiple sclerosis
Dose summary: Loading: 20 mg subcutaneous injection at Weeks 0, 1, and 2. Maintenance: 20 mg monthly starting at Week 4. First injection under healthcare professional supervision.
Renal context: The pharmacokinetics of ofatumumab have not been studied in renal impairment and the label specifies no renal dose adjustment. Ofatumumab is a monoclonal antibody given as a fixed 20 mg subcutaneous dose; renal status is assessed by the prescriber rather than adjusted from a table. (1)
Hepatic guidance
Baseline liver function tests are obtained before starting therapy.
Frequently asked questions
Can Kesimpta cure my MS?
Kesimpta is a disease-modifying therapy for multiple sclerosis. (1)
Can I receive live vaccines while on Kesimpta?
Live vaccines should be given at least 4 weeks before starting Kesimpta and avoided during treatment and until B-cell recovery. Discuss any vaccine, live or non-live, with your healthcare provider before receiving it. (1)
What should I do if I miss a monthly injection?
Contact your healthcare provider for instructions. Do not take an extra dose or change the dosing schedule yourself. (1)
Is Kesimpta the same as the intravenous ofatumumab product (Arzerra)?
Kesimpta (subcutaneous, for MS) and the intravenous ofatumumab product used for chronic lymphocytic leukemia have different indications and dosing. (1)
What is the mechanism of action of ofatumumab?
Ofatumumab is a CD20-directed cytolytic monoclonal antibody. Not established from the sources reviewed: the detailed mechanism and disease-activity effect were not established in the sources reviewed for this page beyond the approved indication. (1)
What is the generic name of Ofatumumab?
The generic name is ofatumumab. It is sold under brand names including Kesimpta. (1)
What class of drug is ofatumumab?
Ofatumumab is classed as: CD20-directed cytolytic monoclonal antibody. (1)
References
- KESIMPTA (ofatumumab) — prescribing informationU.S. Food and Drug Administration · United States · accessed 2026-08-05 · source 1
- KESIMPTA (OFATUMUMAB) INJECTION, SOLUTION [NOVARTIS PHARMACEUTICALS CORPORATION] — US prescribing information (DailyMed SPL)U.S. National Library of Medicine (DailyMed) · US · accessed 2026-08-14 · source 2
- Ofatumumab Injection (Chronic Lymphocytic Leukemia) — patient drug information (MedlinePlus)U.S. National Library of Medicine (MedlinePlus) · US · accessed 2026-08-14 · source 3
- KESIMPTA — FDA approval record (Drugs@FDA BLA125326)U.S. Food and Drug Administration · US · accessed 2026-08-14 · source 4
- ofatumumab — RxNorm normalized drug concept (RXCUI 712566)U.S. National Library of Medicine (RxNorm) · US · accessed 2026-08-14 · source 5
Brand names by country
Single-ingredient ofatumumab names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.
Priority countries
United States
- KESIMPTA20 mg/.4mL · novartis pharmaceuticals corporation
Canada
- ARZERRA