Most Common Side Effects of Kesimpta
Kesimpta (ofatumumab), used for relapsing multiple sclerosis, commonly causes injection-related reactions in up to 21% of patients. These include pain, redness, and swelling at the site, often occurring after the first dose and decreasing over time.[1]
Other frequent side effects (affecting 10-20% of users) are upper respiratory tract infections, headache, and urinary tract infections.[1][2]
How Injection Reactions Feel and Last
Reactions typically start within 24 hours of the subcutaneous injection and resolve in 1-3 days. Symptoms range from mild itching or rash to temporary flu-like feelings such as fatigue or feverishness. Premedication with an antihistamine or pain reliever can reduce severity.[1]
Side Effects by Frequency
- Very common (≥10%): Injection site reactions, upper respiratory infections, headache.[1]
- Common (1-10%): Urinary tract infections, blood tests showing reduced white blood cells or liver enzyme changes, herpes infections, allergic reactions.[1][2]
- Less common issues include fatigue, diarrhea, or worsening MS symptoms temporarily after starting.[1]
Why Do These Happen with Kesimpta?
As a monoclonal antibody targeting CD20 on B cells, Kesimpta depletes these immune cells, raising infection risk and triggering localized inflammation from injections. First doses carry higher reaction rates due to initial immune response.[1][3]
What If Reactions Are Severe?
Serious effects like severe allergic reactions (anaphylaxis), progressive multifocal leukoencephalopathy (rare brain infection), or hepatitis B reactivation occur in under 1% but require immediate medical attention. Stop use and seek care for swelling of face/throat, persistent fever, or neurological changes.[1][2]
How Patients Manage Side Effects
Rotate injection sites (abdomen, thigh, upper arm), apply cold packs, and stay hydrated. Regular blood monitoring catches issues like low infection-fighting cells early. Most tolerate it well long-term, with side effects peaking early.[1][3]
Kesimpta vs. Other MS Drugs' Side Effects
Compared to Ocrevus (IV infusion, fewer injection issues but infusion reactions), Kesimpta offers at-home dosing but similar infection risks. Unlike oral fingolimod, it avoids heart rhythm concerns but shares B-cell depletion effects.[2][3]
[1]: Kesimpta Prescribing Information (Novartis)
[2]: FDA Label for Kesimpta
[3]: Drugs.com - Kesimpta Side Effects