What the label lists and what reports show
Ofatumumab side effects
Ofatumumab's FDA label: “Most common adverse reactions (incidence greater than 10%) are upper respiratory tract infection, headache, injection-related reactions, and local injection site reactions.” FAERS holds 33,037 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is fatigue (5,534 reports).
- No generic listed
Check it at the source: the ofatumumab FDA label on DailyMed (effective April 1, 2026, Novartis Pharmaceuticals Corporation); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of KESIMPTA?KESIMPTA may cause serious side effects, including: See “What is the most important information I should know about KESIMPTA?” Injection-related reactions. Injection-related reactions are a common side effect of KESIMPTA. Injecting KESIMPTA can cause injection-related reactions that can happen within 24 hours (1 day) following the first injection and with later injections. There are two kinds of reactions: at or near the injection site: redness of the skin, swelling, itching and pain. Talk with your healthcare provider if you have any of these signs and symptoms. that may happen when certain substances are released in your body: fever, headache, pain in the muscles, chills, tiredness, rash, hives, trouble breathing, swelling of the face, eyelids, lips, mouth, tongue and throat, and feeling faint, or chest tightness. […]
Source: FDA drug label, Novartis Pharmaceuticals Corporation, effective April 1, 2026 (SPL set 6a8a3f53-2062-48ff-9dbe-b939df133ca3), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsMost common adverse reactions (incidence greater than 10%) are upper respiratory tract infection, headache, injection-related reactions, and local injection site reactions.
Table 1: Adverse Reactions in Patients With RMS With an Incidence of at Least 5% With KESIMPTA and a Greater Incidence Than Teriflunomide (Pooled Study 1 and Study 2)
| Adverse reactions | KESIMPTA 20 mg N = 946 % | Teriflunomide 14 mg N = 936 % |
|---|---|---|
| Upper respiratory tract infections a | 39 | 38 |
| Injection-related reactions (systemic) | 21 | 15 |
| Headache | 13 | 12 |
| Injection-site reactions (local) | 11 | 6 |
| Urinary tract infection | 10 | 8 |
| Back pain | 8 | 6 |
| Blood immunoglobulin M decreased | 6 | 2 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe following clinically significant adverse reactions are discussed in greater detail elsewhere in the labeling: Infections [see Warnings and Precautions (5.1)] Injection-Related Reactions and Hypersensitivity Reactions [see Warnings and Precautions (5.2)] Reduction in Immunoglobulins [see Warnings and Precautions (5.3)] Liver Injury [see Warnings and Precautions (5.4)] Most common adverse reactions (incidence greater than 10%) are upper respiratory tract infection, headache, injection-related reactions, and local injection site reactions. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Novartis Pharmaceuticals Corporation at 1-888-669-6682 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice. Approximately 1500 patients with RMS received KESIMPTA in clinical studies. In Study 1 and Study 2, 1882 patients with RMS were randomized, 946 of whom were treated with KESIMPTA for a median duration of 85 weeks; 33% of patients receiving KESIMPTA were treated for up to 120 weeks [see Clinical Studies (14.1)].
Source: FDA drug label, Novartis Pharmaceuticals Corporation, effective April 1, 2026 (SPL set 6a8a3f53-2062-48ff-9dbe-b939df133ca3), via openFDA; the full label on DailyMed
What do FAERS reports show?
33,037 reports list ofatumumab among the medicines taken, each a report of something that happened, not proof the medicine caused it; 762 are coded as a death and 4,565 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Reports rose sharply in 2023 (8,729, against a median of 680 a year): FAERS counts follow reporting, which news, litigation and label changes can drive, not how often a reaction happens. Of the 22 reactions below, 8 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Ofatumumab: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions