Ofatumumab

What it is and how it works

Mechanism of Action The precise mechanism by which ofatumumab exerts its therapeutic effects in multiple sclerosis is unknown, but is presumed to involve binding to CD20, a cell surface antigen present on pre-B and mature B lymphocytes. Following cell surface binding to B lymphocytes, ofatumumab results in antibody-dependent cellular cytolysis and complement-mediated lysis.

Mechanism class: CD20-directed Antibody Interactions

Indications

is indicated for the treatment of relapsing forms of multiple sclerosis (MS), to include clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease, in adults. KESIMPTA is a CD20-directed cytolytic antibody indicated for the treatment of relapsing forms of multiple sclerosis (MS), to include clinically isolated syndrome, relapsing-remitting disease, and active secondary progressive disease, in adults.

Dosage and administration (summary)

Before initiating KESIMPTA, screen for Hepatitis B virus (HBV) and obtain serum quantitative immunoglobulins, aminotransferases, alkaline phosphatase, and bilirubin. Administer KESIMPTA by subcutaneous injection only. ( 2.2 , 2.3 ) Initial Dosing: 20 mg administered at Weeks 0, 1, and 2. Subsequent Dosing: 20 mg administered monthly starting at Week 4. 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.

Contraindications

is contraindicated in patients with: Active HBV infection . History of hypersensitivity to ofatumumab or life-threatening injection-related reaction to KESIMPTA. Hypersensitivity reactions have included anaphylaxis and angioedema . Active HBV infection. History of hypersensitivity to ofatumumab or life-threatening injection-related reaction to KESIMPTA.

Warnings and precautions

Infections: Serious, including life-threatening and fatal infections, have occurred in patients treated with anti-CD20 therapies. Delay KESIMPTA administration in patients with an active infection until the infection is resolved. Vaccination with live-attenuated or live vaccines is not recommended during treatment with KESIMPTA and after discontinuation, until B-cell repletion. Injection-Related Reactions and Hypersensitivity Reactions: Management for injection-related reactions and hypersensitivity reactions depends on the type and severity of the reaction.

Pregnancy

Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to KESIMPTA during pregnancy. Healthcare providers are encouraged to enroll pregnant patients, or pregnant women may register themselves in the MotherToBaby Pregnancy Study in Multiple Sclerosis by calling 1-877-311-8972, b…

Storage and supply

Storage and Handling KESIMPTA Sensoready pens and prefilled syringes must be refrigerated at 2ºC to 8ºC (36ºF to 46ºF). Keep the product in the original carton to protect from light until the time of use. Do not freeze. To avoid foaming, do not shake.

Source: Ofatumumab (Kesimpta) — US FDA prescribing information, 2026-04-01, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.