Reduced Oligodendrocyte-specific Cytotoxicity and Ofatumumab Treatment

Background and Rationale:

The role of B-cells in multiple sclerosis (MS) pathogenesis is still not fully understood, however studies have shown that: 1) intrathecal synthesis of immunoglobulin can be detected in the cerebral spinal fluid of >90% of MS patients; 2) there are multiple clonally expanded B-cell populations in chronic MS brain lesions; 3) ectopic lymphoid follicles containing proliferating B-cells have been identified within the meninges of secondary progressive MS patients; and 4) anti-B cell depleting therapies have been shown to have clinical benefit in MS. In addition to these findings B-cells have been shown to:

• Secrete autoantibodies.
• Serve as antigen-presenting cells.
• Facilitate T-cell activation.
• Contribute to the micro-environment by local secretion of immune mediators such as cytokines and chemokines.

It is important that investigators not only understand the clinical effects of B-cell depletion, but also, critically, that investigators understand the ongoing mechanisms of action following treatment with Ofatumumab. Specifically, how the remaining pathogenic leukocyte populations, such as T-cells, monocytes, neutrophils and natural killer (NK) cells are modulated indirectly by Ofatumumab such that they may be less pathogenic to the myelinating oligodendrocyte population.

Ofatumumab is an anti-CD20 human monoclonal antibody that has demonstrated efficacy in lowering relapse rates, magnetic resonance Imaging (MRI) activity and neurofilament light (NF-L) levels, as well as significant reductions in confirmed disability worsening in patients with relapsing forms MS.

The exact role(s) of B cells in MS pathogenesis are still unclear at present, as are the events that lead to oligodendrocyte death and dysfunction. Oligodendrocytes are the myelinating cells of the central nervous system (CNS), and demyelination and oligodendrocyte death are critical events in the disease process of MS. At present no current approved MS drug therapies are targeted to directly protecting against oligodendrocyte loss and dysfunction or aimed at enhancing repair of the CNS. The proposed studies in this application are novel in that effect(s) of Ofatumumab treatment in MS has not been previously studied in oligodendrocyte or oligodendrocyte progenitor cell (OPC) populations. The outcomes from this study could identify an additional mode of action of Ofatumumab treatment, with effects that could indirectly benefit the CNS.

Specific Aims:

For this study, the investigators propose that the long-term mechanism of action associated with the beneficial clinical outcomes of Ofatumumab therapy in MS is not only due to the direct effect of removing circulating B-cells, but is also due to the subsequent alteration in immune homeostasis with an accompanied reduction in cytotoxic secretory products from leukocyte subsets including T cells, monocytes, neutrophils and NK cells. The study has two specific aims:

For Specific Aim 1 (primary objective) the investigators will determine if solutes secreted by T cells, monocytes, neutrophils or NK cells isolated from patients with relapsing-remitting forms of MS following 6 months (M06) of treatment with Ofatumumab are less toxic to mouse-derived oligodendrocytes and their progeny (OPC) than solutes secreted by the same sub-populations of leukocytes collected prior to treatment (M00 drug naive). In this aim, the primary outcome will be to assess measures of oligodendrocyte and OPC death, and mitochondrial dysfunction.

For Specific Aim 2 (exploratory objective) the investigators will identify the factor(s) responsible for inducing oligodendrocyte and OPC stress (comparing M06 supernatant samples to M00) by firstly using a cytokine array approach followed, if needed, by a 2D-electrophoresis LC-MS proteomic approach. The investigators will also perform additional analyses that will explore altered microglial and astrocyte responses following treatment with solutes secreted from leukocyte sub-populations at M00 and M06 in MS patients.

Study Population:

For this prospective longitudinal study the investigators will recruit 20 patients with clinically definite relapsing-remitting MS (RR-MS) (as defined by the revised McDonald criteria) who will be treated with Ofatumumab (Kesimpta). The investigators will also recruit 20 healthy control (HC) subjects. For these studies, RR-MS patients will serve as their own internal control and the investigators will compare changes over time on Ofatumumab with pre-treatment measures. In addition, RR-MS patient samples will be compared to healthy control leukocyte sub-population supernatants. All RR-MS patients will be prescribed and treated with Ofatumumab as part of their standard of care from their treating provider, with the exception of the HC subjects who receive no treatment.

Procedures and Data Collection:

All RR-MS patients will be selected from those currently being seen by physicians at the Multiple Sclerosis Comprehensive Care Center at University of Southern California (USC) Keck School of Medicine or the LAC+USC Medical Center, Multiple Sclerosis Clinic, and for whom the physician has already deemed Ofatumumab would be a logical treatment alternative. The investigators will not be assessing eligibility for Ofatumumab treatment as criteria for inclusion in this investigator-initiated trial (IIT). The investigators expect enroll subjects over a 10-12 month recruitment phase. The investigators expect the last patient sample to be collected 18 months following commencement of the study with final analysis of data completed 27 months after study commencement. For the Ofatumumab cohort, the investigators will collect ~80ml blood from enrolled patients at M00 (baseline, naive to drug), and will collect a further 80ml of blood at M06 (months 5-6 prior to the 6-month Ofatumumab injection). For the HC cohort, the investigators will collect ~80ml blood from enrolled subjects at only one time point. Blood samples will be processed and leukocyte sub-populations isolated for culture.