New treatments for SLE: cell-depleting and anti-cytokine therapies.
Although systemic lupus erythematosus (SLE) is indeed a complex autoimmune disease, recent advances in our understanding of lupus pathogenesis have suggested new, targeted approaches to therapy. The purpose of this review is to discuss the underlying scientific rationale and results of first clinical studies of new treatment approaches to SLE, with a focus on cell-depleting therapies and cytokine blockade. It has become clear that the B lymphocyte plays a key role in disease pathogenesis by both autoantibody-dependent and autoantibody-independent mechanisms. Additionally, aberrant interactions between B and T cells are critical to disease emergence and progression. New agents that directly target immune cells abnormal in SLE include the B-cell depleting or modulating antibodies, rituximab (anti-CD20) and epratuzumab (anti-CD22) and the anti-dsDNA tolerogen LJP394. Another promising approach has been to block co-stimulatory interactions between T and B cells, for example by inhibiting the CD40-CD40 ligand pathway with anti-CD40 ligand monoclonal antibody or the B7 pathway with CTLA-4Ig. Immune cells can also be manipulated indirectly through cytokine effects. For B cells, anti-BAFF (B-cell activation factor of the tumor necrosis family) provides an example of this approach. Other, more pleiotropic cytokines can likewise be blocked in SLE. In addition to the blockade of interleukin-10 (IL-10), the first anti-cytokine approach examined, it is mainly anti-tumor necrosis factor therapy that has come into focus, holding promise for some patients with lupus nephritis. The majority of the available data on these new treatment approaches stems from open-label trials, but controlled trials are under way. Moreover, many additional cytokines, such as interleukin (IL)-6, IL-18, and the type I interferons, represent interesting future targets.