Background Self-reactive antibodies produced by B-cell derived plasma cells play a crucial role in the pathogenesis of autoimmune disorders. By targeting the source of these pathogenic antibodies, B-cell modulation is one treatment option. However, newly emerging therapeutics directed at specific molecules are not universally available and the current therapies of autoimmune diseases still rely on the systemic use of corticosteroids. Hence, a development of new treatment strategies is required.

Objectives We investigated a hypothesis that some drugs, which are already used for other treatment purposes, might possess unknown B-cell modulatory effects. By using a drug library consisting of 1,200 commercially available, off-patent compounds, an in vitro screening evaluating the drug effect on human B cell proliferation was performed. Afterwards, the selected drugs were tested in vivo to confirm their effect on adaptive immunity and potential use as therapeutic agents in autoimmune diseases.

Methods Human B cells were obtained from healthy donors. Under the stimulation with IL-21 and anti-CD40 antibody, isolated B-cells were cultured for five days in the presence or in the absence of 1μM drugs from the library, and the drug effect on cell proliferation was assessed by 5-Bromo-2'-Deoxyuridine (BrdU) ELISA. Dose-dependency and cytotoxicity test with candidate drugs inhibiting B cell proliferation were performed as validation. IgM and IgG production in the culture supernatant was measured by ELISA. For in vivo validation, further selected drugs were tested in an experimental animal model of epidermolysis bullosa acquisita (EBA), an autoimmune skin blistering disease characterized by antibody production against type VII collagen which triggers the blister formation [1]. One day prior to the disease induction by immunizing B6.S mice with vWFA2, a subdomain of the pathogenic antigen in EBA [1], drug or vehicle treatment was initiated and continued for eight weeks. Disease severity was recoded weekly, and the antigen-specific B cell as well as plasma cell numbers in the draining lymph nodes were evaluated by flow cytometric analysis.

Results Out of 1,200 drugs, BrdU ELISA screening identified 48 compounds inhibiting human B cell proliferation and the validation narrowed the number of candidates to six. Immunoglobulin production was negatively affected in the presence of these compounds with a dose-dependent manner. Experimental EBA mice treated with the selected drugs showed >50% less disease development compared to the vehicle-treated group. Furthermore, mice treated with one of the candidate drugs had significantly fewer numbers of B cells as well as antigen-specific B cells in the draining lymph nodes (p<0.05).

Conclusions The present results suggest unknown properties of “old” drugs in B cell biology as well as the subsequent adaptive immunity and their potential “new” roles in the treatment of autoimmune diseases. In addition, such a drug screening method would save time and be more cost efficient than the conventional approach used to develop new therapeutic agents.

1. Ludwig R. Expert Rev Clin Immunol. 2015;11(12):1365–78.

Disclosure of Interest None declared