The American Food and Drug Administration (FDA) has approved the use of ofatumumab (tradename Kesimpta) for the treatment of relapsing forms of MS, including clinically isolated syndrome, relapsing-remitting MS (RRMS), and active secondary progressive MS (SPMS). It has yet to be approved for use in Australia. This treatment has been used since 2009 for the treatment of chronic lymphocytic leukemia (under the tradename Arzerra), but has been restricted in some markets.
Ofatumumab is a “monoclonal antibody” which can be self-administered by monthly injection at home. Antibodies are proteins normally made by the immune system to target foreign invaders. “Monoclonal” antibodies are so named because they have one specific target for destruction. In this case, ofatumumab has been engineered to target CD20, a molecule found on a type of immune cell thought to be important in the development and progression of MS. Other medications used to target CD20 in MS have included rituximab (Rituxan) and ocrelizumab (Ocrevus).
Several MS medications are repurposed cancer treatments, specifically for leukemia and lymphoma which are immune cell-based cancers. Monoclonal antibodies successfully reduce specific immune cells both in these malignancies (where immune cells are multiplying in an uncontrolled way) and in autoimmune diseases (where the immune cells are mistakenly targeting brain and spinal cord). Reduction in immune cells has been especially powerful in reducing relapses in RRMS, however, it has had less clinical effect in some forms of progressive forms of MS as progressive forms of MS are thought to generally have lower levels of inflammation.
In clinical trials named ASCLEPIOS I and II, ofatumumab was compared against teriflunomide (Aubagio). The trials randomly assigned 946 patients to receive ofatumumab and 936 to receive teriflunomide. Results showed that average yearly rates of relapses for patients with MS were reduced by 51% for those who received ofatumumab, and by 58% for those who received teriflunomide. A larger number in the ofatumumab group had no evidence of MS activity during the trial, measured via number of relapses, disability worsening, and MRI activity. No evidence of disease activity is widely recognised as the optimal treatment goal in MS.
Like any medication, there are potential side effects. For ofatumumab, these include injection-related reactions and increased risk of infections. We await review by the Therapeutic Goods Administration and Pharmaceutical Benefits Advisory Committee to determine whether ofatumumab will become available and subsidised for MS in Australia and for whom.
MS is a very varied disease, and not all medications will work for all people. It is important that individuals with MS discuss any new treatment options with their neurologist or health care professional, as ofatumumab is not suitable for everyone.