CD20+ T Cells as Pathogenic Players and Therapeutic Targets in MS

Ublituximab: A new FDA-approved anti-CD20 mAb for relapsing forms of multiple sclerosis

Ublituximab, an intravenous glycoengineered chimeric anti-CD20 IgG1 monoclonal antibody (mAb), is a new FDA-approved treatment for relapsing forms of Multiple Sclerosis (MS). Reassembling the other three anti-CD20 mAbs already in use for MS (rituximab, ocrelizumab and ofatumumab), ublituximab leads to depletion of B cells but spars long-lived plasma cells. Here, we discuss the main findings obtained during the phase 3 clinical trials (ULTIMATE I and II) for ublituximab versus teriflunomide. The current emergence and approval of new anti-CD20 mAbs with different dose regimens, routes of application, glycoengineering and mechanisms of action may contribute to different clinical outcomes.

Ocrelizumab Treatment Modulates B-Cell Regulating Factors in Multiple Sclerosis

BACKGROUND AND OBJECTIVES

Antibodies to CD20 efficiently reduce new relapses in multiple sclerosis (MS), and ocrelizumab has been shown to be effective also in primary progressive MS. Although anti-CD20 treatments efficiently deplete B cells in blood, some B cells and CD20^- plasma cells persist in lymphatic organs and the inflamed CNS; their survival is regulated by the B cell-activating factor (BAFF)/A proliferation-inducing ligand (APRIL) system. The administration of a soluble receptor for BAFF and APRIL, atacicept, unexpectedly worsened MS. Here, we explored the long-term effects of ocrelizumab on immune cell subsets as well as on cytokines and endogenous soluble receptors comprising the BAFF-APRIL system.

METHODS

We analyzed immune cell subsets and B cell-regulating factors longitudinally for up to 2.5 years in patients with MS treated with ocrelizumab. In a second cohort, we determined B-cell regulatory factors in the CSF before and after ocrelizumab. We quantified the cytokines BAFF and APRIL along with their endogenous soluble receptors soluble B-cell maturation antigen (sBCMA) and soluble transmembrane activator and calcium-modulator and cyclophilin ligand (CAML) interactor (sTACI) using enzyme-linked immunosorbent assays (ELISAs). In addition, we established an in-house ELISA to measure sTACI-BAFF complexes.

RESULTS

Ocrelizumab treatment of people with MS persistently depleted B cells and CD20⁺ T cells. This treatment enhanced BAFF and reduced the free endogenous soluble receptor and decoy sTACI in both serum and CSF. Levels of sTACI negatively correlated with BAFF levels. Reduction of sTACI was associated with formation of sTACI-BAFF complexes.

DISCUSSION

We describe a novel effect of anti-CD20 therapy on the BAFF-APRIL system, namely reduction of sTACI. Because sTACI is a decoy for APRIL, its reduction may enhance local APRIL activity, thereby promoting regulatory IgA⁺ plasma cells and astrocytic interleukin (IL)-10 production. Thus, reducing sTACI might contribute to the beneficial effect of anti-CD20 as exogenous sTACI (atacicept) worsened MS.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that endogenous sTACI in blood and CSF is decreased after ocrelizumab treatment.

Antibody Therapies for Progressive Multiple Sclerosis and for Promoting Repair

Progressive multiple sclerosis (PMS) is clinically distinct from relapsing-remitting MS (RRMS). In PMS, clinical disability progression occurs independently of relapse activity. Furthermore, there is increasing evidence that the pathological mechanisms of PMS and RRMS are different. Current therapeutic options for the treatment of PMS remain inadequate, although ocrelizumab, a B-cell-depleting antibody, is now available as the first approved therapeutic option for primary progressive MS. Recent advances in understanding the pathophysiology of PMS provide hope for new innovative therapeutic options: these include antibody therapies with anti-inflammatory, neuroprotective, and/or remyelination-fostering effects. In this review, we summarize the relevant trial data relating to antibody therapy and consider future antibody options for treating PMS.