Ofatumumab Injection (Chronic Lymphocytic Leukemia)
Ofatumumab (Kesimpta) is a targeted antibody therapy given by injection to treat relapsing forms of multiple sclerosis in adults.
🧬 Where this information comes from Click to expand
The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 1 clinical label set within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →
Ofatumumab (Kesimpta) is a lab-made antibody for relapsing forms of multiple sclerosis in adults. It latches onto B cells, a type of immune cell, and prompts the body to destroy them, and it is one of several B-cell therapies for MS and the one you inject yourself at home once a month. Most people tolerate it well, and colds, headache, and redness or a reaction after the shot are the most common complaints. Watch for infection, since losing B cells weakens your defenses, and call your doctor about fever, chills, a lingering cough or infections that keep coming back.
Clinical pearls
- Get any live vaccines at least 4 weeks before starting, because they cannot be given during treatment or until B cells recover.
- Expect hepatitis B testing and liver and immunoglobulin (antibody level) blood tests before starting, with repeat checks throughout treatment.
- Use reliable contraception during treatment and for 6 months after, since it can deplete an unborn baby’s B cells.
- Tell any prescriber you use it before starting steroids or other immune-suppressing drugs, which stack on top of its infection risk.
Patient information guide A plain-language walkthrough of Ofatumumab Injection (Chronic Lymphocytic Leukemia), written from its FDA label.
What Ofatumumab Injection (Chronic Lymphocytic Leukemia) is used for
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Ofatumumab is approved to treat relapsing forms of multiple sclerosis (MS) in adults. The specific forms it covers include:
- Clinically isolated syndrome — a first neurological episode that may indicate the onset of MS
- Relapsing-remitting MS — the most common form, with defined attacks (relapses) followed by recovery periods
- Active secondary progressive MS — a later stage of MS where disability may accumulate, but with ongoing relapses
How Ofatumumab Injection (Chronic Lymphocytic Leukemia) works
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Ofatumumab is a monoclonal antibody — a targeted, lab-engineered protein — that binds to a surface marker called CD20 found on pre-B and mature B lymphocytes (a type of immune cell). Once bound, it triggers two destruction mechanisms: antibody-dependent cellular cytolysis (the immune system kills the flagged cells) and complement-mediated lysis (a separate immune cascade breaks them apart). The result is a significant depletion of B cells, which are believed to play a central role in the inflammation that damages nerves in MS.
The exact reason B-cell depletion helps MS is still not fully understood, but reducing these cells has been shown to control relapses in clinical trials.
Ofatumumab Injection (Chronic Lymphocytic Leukemia) dosage
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Ofatumumab is given only as a subcutaneous injection — a small shot under the skin, similar to how some people inject insulin. There are no food restrictions. A starting series is given in the first two weeks, followed by once-monthly maintenance injections beginning at week 4.
- Starting phase: injections at weeks 0, 1, and 2
- Maintenance phase: one injection per month starting at week 4
- Missed dose: inject as soon as you remember — do not simply wait for the next scheduled date
Follow the detailed administration instructions provided with your auto-injector, and ask your care team to walk you through the first injection.
Dosing details from the FDA-approved label
From the Ofatumumab Injection (Chronic Lymphocytic Leukemia) prescribing information (“Dosage and Administration”). Doses are set by your prescriber for your product, condition, kidney function and age — never change a dose on your own.
( 2.2 , 2.3 ) Initial Dosing: 20 mg administered at Weeks 0, 1, and 2.
Read the label’s full dosing text
2 DOSAGE AND ADMINISTRATION Before initiating KESIMPTA, screen for Hepatitis B virus (HBV) and obtain serum quantitative immunoglobulins, aminotransferases, alkaline phosphatase, and bilirubin. ( 2.1 ) Administer KESIMPTA by subcutaneous injection only. ( 2.2 , 2.3 ) Initial Dosing: 20 mg administered at Weeks 0, 1, and 2. ( 2.2 ) Subsequent Dosing: 20 mg administered monthly starting at Week 4. ( 2.2 ) 2.1 Assessments Prior to First Dose of KESIMPTA Hepatitis B Virus Screening Prior to initiating KESIMPTA, perform Hepatitis B virus (HBV) screening. KESIMPTA is contraindicated in patients with active HBV confirmed by positive results for Hepatitis B surface antigen [HBsAg] and anti-HBV tests. For patients who are negative for HBsAg and positive for Hepatitis B core antibody [HBcAb+] or are carriers of HBV [HBsAg+], consult liver disease experts before starting and during treatment with KESIMPTA [see Warnings and Precautions (5.1)] . Serum Immunoglobulins Prior to initiating KESIMPTA, perform testing for quantitative serum immunoglobulins [see Warnings and Precautions (5.3)] . For patients with low serum immunoglobulins, consult immunology experts before initiating treatment with KESIMPTA. Vaccinations Because vaccination with live-attenuated or live vaccines is not recommended during treatment and after discontinuation until B-cell repletion, administer all immunizations according to immunization guidelines at least 4 weeks prior to initiation of KESIMPTA for live or live-attenuated vaccines, and whenever possible, at least 2 weeks prior to initiation of KESIMPTA for inactivated vaccines [see Warnings and Precautions (5.1)] . Liver Function Tests Prior to initiating KESIMPTA, obtain serum aminotransferases (alanine aminotransferase [ALT] and aspartate aminotransferase [AST]), alkaline phosphatase, and bilirubin levels [see Warnings and Precautions (5.4)] . 2.2 Recommended Dosage The recommended dosage of KESIMPTA is: initial dosing of 20 mg by subcutaneous injection at Weeks 0, 1, and 2, followed by subsequent dosing of 20 mg by subcutaneous injection once monthly starting at Week 4. Missed Doses If an injection of KESIMPTA is missed, it should be administered as soon as possible without waiting until the next scheduled dose. Subsequent doses should be administered at the recommended intervals.
Excerpted — the section continues on the label. Read the full Dosage and Administration section on DailyMed →
Ofatumumab Injection (Chronic Lymphocytic Leukemia) side effects
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The most commonly reported side effects with ofatumumab include:
Common side effects
- Upper respiratory tract infections (colds, sinus infections)
- Headache
- Injection-related reactions (systemic symptoms after the shot)
- Local injection site reactions (redness or discomfort where injected)
- Urinary tract infections
- Low immunoglobulin M (IgM) levels
When to get medical help
- Signs of serious infection: fever, chills, persistent cough, or feeling very unwell — call your doctor right away
- Symptoms of a severe allergic reaction: swelling of the face or throat, difficulty breathing, rapid heartbeat — seek emergency care immediately
- Signs of liver injury: yellowing of the skin or eyes, dark urine, severe nausea or stomach pain
- Unusual or repeated infections that don't clear up — this could signal immune compromise from low immunoglobulin levels
- Any new or worsening symptoms of infection during treatment
Seek immediate medical help if you develop signs of a severe allergic reaction — such as throat swelling or difficulty breathing — or symptoms of a serious infection like high fever, severe fatigue, or an infection that won't clear up.
Ofatumumab Injection (Chronic Lymphocytic Leukemia) warnings and precautions
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- Serious infections: Because ofatumumab depletes B cells, your immune defenses are reduced. Serious bacterial, fungal, and viral infections — including life-threatening ones — have occurred. Report any sign of infection to your doctor promptly. Treatment is delayed if you have an active infection.
- Injection and hypersensitivity reactions: Allergic reactions, including anaphylaxis (a severe, sudden allergic response) and angioedema (swelling under the skin), have been reported. Management depends on severity — know the warning signs.
- Low immunoglobulins: The drug can lower immune protein levels over time, further raising infection risk. These levels are checked before, during, and after treatment.
- Liver injury: Significant liver damage has occurred. Liver function tests are required before starting and are monitored during treatment. The drug should be stopped if liver injury is confirmed without another explanation.
- Fetal harm: Animal studies show ofatumumab can cross the placenta and deplete B cells in the developing baby. Women must use effective contraception during treatment and for 6 months afterward.
- Vaccines: Live and live-attenuated vaccines must not be given during treatment or until B cells recover after stopping. Plan all vaccinations in advance.
Ofatumumab Injection (Chronic Lymphocytic Leukemia) interactions
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Ofatumumab does not interact with most traditional medications through liver enzyme pathways — but immune system effects are where the real concern lies:
- Immunosuppressant drugs and corticosteroids — using these alongside ofatumumab can stack up immune-suppressing effects, raising the risk of serious infection
- Other MS or immune-modulating therapies — switching from another MS treatment to ofatumumab requires careful timing; residual immune effects from prior drugs can overlap and compound the immunosuppression
- Live or live-attenuated vaccines — these are not safe during treatment or until B cells recover after stopping; inactivated vaccines should ideally be given at least 2 weeks before starting
Interactions listed in the FDA-approved label
From the Ofatumumab Injection (Chronic Lymphocytic Leukemia) prescribing information (“Drug Interactions”): what the manufacturer studied or reported to the FDA.
7 DRUG INTERACTIONS 7.1 Immunosuppressive or Immune-Modulating Therapies Concomitant usage of KESIMPTA with immunosuppressant drugs, including systemic corticosteroids, may increase the risk of infection. Consider the risk of additive immune system effects when coadministering immunosuppressive therapies with KESIMPTA.
Read the label’s full interactions text
7 DRUG INTERACTIONS 7.1 Immunosuppressive or Immune-Modulating Therapies Concomitant usage of KESIMPTA with immunosuppressant drugs, including systemic corticosteroids, may increase the risk of infection. Consider the risk of additive immune system effects when coadministering immunosuppressive therapies with KESIMPTA. When switching from therapies with immune effects, the duration and mechanism of action of these therapies should be taken into account because of potential additive immunosuppressive effects when initiating KESIMPTA.
Not a complete list. The label covers the interactions the manufacturer studied or reported, and our own interaction database does not cover every medicine either. Bring your full medication list, including vitamins and herbal products, to your pharmacist.
Before taking Ofatumumab Injection (Chronic Lymphocytic Leukemia)
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- Active hepatitis B infection — this is a contraindication; the drug must not be used
- Past hepatitis B exposure — even without active disease, specialist evaluation is required before starting
- Previous severe allergic reaction to ofatumumab — also a contraindication
- Low immunoglobulin levels — an immunology consult is recommended before starting
- Pregnancy — may harm the fetus; contraception required during treatment and for 6 months after the last dose
- Newborns and infants exposed in the womb — live vaccines should be avoided until B-cell counts are confirmed normal
- Renal or hepatic impairment — pharmacokinetics in these patients have not been studied; discuss with your doctor
- Upcoming vaccinations — live vaccines must be completed at least 4 weeks before starting; inactivated vaccines at least 2 weeks before
What Ofatumumab Injection (Chronic Lymphocytic Leukemia) does in the body
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Ofatumumab rapidly and deeply depletes B lymphocytes — immune cells measured via CD19+ markers in the blood. Within just one to two weeks of starting treatment, the vast majority of patients show B-cell counts fall below the lower limit of normal. By week 12, nearly all treated patients have significantly suppressed B-cell levels, and those low levels are maintained throughout ongoing therapy.
After stopping treatment, B cells gradually recover — the median time for B-cell counts to return to normal is roughly 24 weeks (about 6 months), though this varies by individual.
How your body processes Ofatumumab Injection (Chronic Lymphocytic Leukemia)
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Ofatumumab is injected under the skin and is believed to be absorbed primarily through the lymphatic system — the same route used by similar antibody therapies. Its elimination from the body is unusual: early in treatment, when B-cell counts are high, the drug is cleared faster because the B cells themselves consume it. As B cells are depleted, the body clears ofatumumab more slowly through normal protein breakdown (catabolism).
At steady state, the half-life — the time it takes for half the drug to leave the body — is approximately 16 days. Ofatumumab breaks down into small peptides and amino acids; it is not cleared by the kidneys and does not interact with the liver enzymes that process most traditional medications. Factors like age, sex, body weight, and race do not meaningfully change how the drug behaves in the body.
How to store Ofatumumab Injection (Chronic Lymphocytic Leukemia)
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refrigerated at 2ºC to 8ºC (36ºF to 46ºF). protect from light until the time of use. Do not freeze.
Written from the FDA-approved label with AI and reviewed by our pharmacy team. How we use AI →
Ofatumumab Injection (Chronic Lymphocytic Leukemia): pharmacist answers to common questions
Quick, plain-English answers to the questions patients ask most about Ofatumumab Injection (Chronic Lymphocytic Leukemia) — the kind of thing our pharmacy team would talk through with you at the counter.
What exactly is this medication used for?
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How do I actually take it — is it a pill or a shot?
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What side effects should I actually expect?
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I'm worried about the infection risk — should I be?
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Is it safe to take if I'm pregnant or trying to get pregnant?
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Do I need any tests or shots before I start this medication?
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Is Ofatumumab Injection (Chronic Lymphocytic Leukemia) available over the counter?
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When was Ofatumumab Injection (Chronic Lymphocytic Leukemia) first available?
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Answers drafted from the FDA-approved label with AI and reviewed by our pharmacy team. How we use AI →
More about Ofatumumab Injection (Chronic Lymphocytic Leukemia) on HelloPharmacist
Ofatumumab Injection (Chronic Lymphocytic Leukemia) on the U.S. market: products, makers and brands
How Ofatumumab Injection (Chronic Lymphocytic Leukemia) appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.
The FDA lists Ofatumumab Injection (Chronic Lymphocytic Leukemia) products; the earliest marketing or approval year on record is 2009. Brand names on the directory include Arzerra, Kesimpta; the rest are generics.
How widely Ofatumumab Injection (Chronic Lymphocytic Leukemia) is used (Medicaid data)
A general measure of how commonly Ofatumumab Injection (Chronic Lymphocytic Leukemia) is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.
Think of this as a proxy for how widely Ofatumumab Injection (Chronic Lymphocytic Leukemia) is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.
How commonly is Ofatumumab Injection (Chronic Lymphocytic Leukemia) prescribed? Of the 1,601 medications we measure, Ofatumumab Injection (Chronic Lymphocytic Leukemia) ranks #660 by Medicaid prescriptions — more than 59% of them.
Utilization by Ofatumumab Injection (Chronic Lymphocytic Leukemia) product
Pick a product to see its own Medicaid numbers. Each chip is one clinical product — a specific strength & dosage form as defined by RxNorm — with brand-name and generic versions combined.
0.4 ML ofatumumab 50 MG/ML Pen Injector
Summed across the 1 of 2 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 2390949
Shares are of the Medicaid prescriptions shown here. Product grouping follows RxNorm (the National Library of Medicine’s drug terminology), so “one product” means one strength & dosage form regardless of manufacturer. Dollar figures are gross Medicaid reimbursement before mandatory rebates — rebates (often large, especially for brand-name drugs) are confidential, so actual net cost to Medicaid is lower than shown.
Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Ofatumumab Injection (Chronic Lymphocytic Leukemia), and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 1 of 2 listed Ofatumumab Injection (Chronic Lymphocytic Leukemia) NDCs with Medicaid activity.
Ofatumumab Injection (Chronic Lymphocytic Leukemia) side effects reported to the FDA (FAERS)
After a medicine reaches the market, patients, doctors and drugmakers can send the FDA reports of problems they think may be linked to it. Here’s what’s been reported for Ofatumumab Injection (Chronic Lymphocytic Leukemia) — a signal of what to watch for, not proof the drug caused it.
Source: openFDA, from the FDA Adverse Event Reporting System (FAERS). These are voluntary reports — they don’t prove the drug caused the effect, and counts reflect how often something was reported, not how often it actually happens. Reports also often name the very problem the medicine is taken for — a common reason to file one is that the drug didn’t help — so for a pain reliever you may see “pain” high on the list; that points to why the report was filed, not to the drug causing the symptom. This counts every report that lists Ofatumumab Injection (Chronic Lymphocytic Leukemia) in any role, so the total runs higher than the FDA’s official dashboard, which counts only cases where the drug is the suspect. For the authoritative figures, see the FDA FAERS Public Dashboard. Always talk to your pharmacist or doctor.
Ofatumumab Injection (Chronic Lymphocytic Leukemia) FDA approval history
How Ofatumumab Injection (Chronic Lymphocytic Leukemia) went from FDA review to the pharmacy shelf — the key milestones in its regulatory journey.
Source: Drugs@FDA.
Ofatumumab Injection (Chronic Lymphocytic Leukemia) recall history
A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.
The FDA’s enforcement reports list no Ofatumumab recalls since July 2021.
✅No Ofatumumab recalls on record since July 2021Source: FDA enforcement (recall) reports, via openFDA; our copy was last updated Sep 24, 2026.
RxNorm Concept Web — From Ingredient to Every Form and Strength
This page starts with one ingredient concept (IN). The branches below show its dose-form concepts (SCDF), then the available clinical drug and strength concepts (SCD). Combination products remain separate concepts with their own pages.
RxCUI 712566 2 dose forms · 3 strengths
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Dose form (SCDF) Injection RxCUI 1658041No current FDA listingClinical drug / strength (SCD) 5 ML ofatumumab 20 MG/MLRxCUI 165804750 ML ofatumumab 20 MG/MLRxCUI 1658042 -
Dose form (SCDF) Pen Injector RxCUI 2390948No current FDA listingClinical drug / strength (SCD) 0.4 ML ofatumumab 50 MG/MLRxCUI 2390949
Look up RxCUI 712566 in the RxCUI Atlas →
RxNorm is the U.S. National Library of Medicine’s normalized drug vocabulary. Its concept hierarchy can include forms that are not currently marketed; the status on each branch compares that concept with current FDA listings. RxCUIs identify vocabulary concepts, not individual packages or manufacturers.
Ofatumumab Injection (Chronic Lymphocytic Leukemia) supply and shortage status
Whether Ofatumumab Injection (Chronic Lymphocytic Leukemia) is in short supply in the U.S. right now, plus any shortage history the FDA has on record. A shortage usually reflects a manufacturing or demand issue — not a safety problem with the drug.
Source: openFDA, from the FDA Drug Shortages database.
Ofatumumab Injection (Chronic Lymphocytic Leukemia) brand names
Ofatumumab Injection (Chronic Lymphocytic Leukemia) is sold under 2 brand names in the FDA directory — Arzerra, Kesimpta. A brand and its generic contain the same active ingredient; the brand name belongs to one company's product.
Ofatumumab Injection (Chronic Lymphocytic Leukemia) drug class (RxNorm)
Ofatumumab Injection (Chronic Lymphocytic Leukemia) belongs to the CD20-directed Cytolytic Antibody class.
Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.
Sources for this Ofatumumab Injection (Chronic Lymphocytic Leukemia) page
Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.
How this page is built
HelloPharmacist combines public FDA and NLM records and does not author the underlying clinical facts. The plain-language sections are written with AI from the FDA-approved label text and reviewed by our pharmacy team before publication. Novartis Pharmaceuticals Corporation is the representative DailyMed label linked for verification and dates. This is general education, not medical advice: always talk to your doctor or pharmacist about your own medicines. How we build and review drug pages →