[Atacicept: a new B lymphocyte-targeted therapy for multiple sclerosis]

Exploring the depths of IgG4: insights into autoimmunity and novel treatments

IgG4 subclass antibodies represent the rarest subclass of IgG antibodies, comprising only 3-5% of antibodies circulating in the bloodstream. These antibodies possess unique structural features, notably their ability to undergo a process known as fragment-antigen binding (Fab)-arm exchange, wherein they exchange half-molecules with other IgG4 antibodies. Functionally, IgG4 antibodies primarily block and exert immunomodulatory effects, particularly in the context of IgE isotype-mediated hypersensitivity reactions. In the context of disease, IgG4 antibodies are prominently observed in various autoimmune diseases combined under the term IgG4 autoimmune diseases (IgG4-AID). These diseases include myasthenia gravis (MG) with autoantibodies against muscle-specific tyrosine kinase (MuSK), nodo-paranodopathies with autoantibodies against paranodal and nodal proteins, pemphigus vulgaris and foliaceus with antibodies against desmoglein and encephalitis with antibodies against LGI1/CASPR2. Additionally, IgG4 antibodies are a prominent feature in the rare entity of IgG4 related disease (IgG4-RD). Intriguingly, both IgG4-AID and IgG4-RD demonstrate a remarkable responsiveness to anti-CD20-mediated B cell depletion therapy (BCDT), suggesting shared underlying immunopathologies. This review aims to provide a comprehensive exploration of B cells, antibody subclasses, and their general properties before examining the distinctive characteristics of IgG4 subclass antibodies in the context of health, IgG4-AID and IgG4-RD. Furthermore, we will examine potential therapeutic strategies for these conditions, with a special focus on leveraging insights gained from anti-CD20-mediated BCDT. Through this analysis, we aim to enhance our understanding of the pathogenesis of IgG4-mediated diseases and identify promising possibilities for targeted therapeutic intervention.

Monoclonal antibodies and recombinant immunoglobulins for the treatment of multiple sclerosis

Multiple sclerosis (MS) is an inflammatory and degenerative disease leading to demyelination and axonal damage in the CNS. Autoimmunity plays a central role in MS pathogenesis. Per definition, monoclonal antibodies are recombinant biological compounds with a well defined target, thus carrying the promise of targeting pathogenic cells or molecules with high specificity, avoiding undesired off-target effects. Natalizumab was the first monoclonal antibody to be approved for the treatment of MS. Several other monoclonal antibodies are in development and have demonstrated promising efficacy in phase II studies. They can be categorized according to their mode of action into compounds targeting (i) leukocyte migration into the CNS (natalizumab); (ii) cytolytic antibodies (rituximab, ocrelizumab, ofatumumab, alemtuzumab); or (iii) antibodies and recombinant proteins targeting cytokines and chemokines and their receptors (daclizumab, ustekinumab, atacicept, tabalumab [Ly-2127399], secukinumab [AIN457]). In this review, we discuss the specific molecular targets, clinical efficacy and safety of these compounds and discuss criteria to anticipate the position of monoclonal antibodies in the diversifying armamentarium of MS therapy in the coming years.

More to come: humoral immune responses in MS

Interest in the role of B-cells in multiple sclerosis (MS) pathogenesis has increased, and a number of B-cell targeted therapies are currently in clinical trials. B-cells are key mediators of the humoral immune response, with roles including antibody production and acting as antigen presenting cells. Whilst previously, the presence of B-cells within MS plaques has been thought to be secondary to T-cell dysregulation, it is now becoming clear that B-cells play an independent role in disease. In this review we will discuss the potential role of B-cells in MS, how this influences our understanding of the disease, and potential therapeutic implications.