Development of a latent IL-17 antagonist for targeted therapy of rheumatoid arthritis.

Abstract

Cytokine based therapies can be targeted to the sites of active inflammation by modifying a given cytokine as a LAP-cytokine. IL-17A has been shown to directly contribute to pathogenesis of rheumatoid arthritis (RA). IL-17F, another member of the IL-17 cytokines family shares structural homology, receptor binding and biological properties with IL-17A but is 30-100 times less potent than IL-17A. (H161R) IL-17F mutant, a natural variant of IL-17F was shown to be protective against asthma in Japanese population. In vitro, IL-17F mutant competitively inhibited wild-type IL-17F and lacked the ability to activate downstream signaling pathways. I hypothesized that (H161R) IL-17F mutant is an additional inhibitor of IL-17A and if modified as LAP-IL-17F mutant, would be an effective targeted therapy for RA. (H161R) IL-17F mutant was created by substituting nucleotide A at position 485 in the wild type IL-17F by G. In vitro assays showed that the IL-17F mutant could bind to IL-17RC but lacked the ability to stimulate IL-6 secretion in HFFF2, 3T3 and HeLa cells and phosphorylate ERK1/2 in HeLa cells. IL-17F mutant also inhibited IL-17A induced secretion of IL-6 in all these cell lines. In order to assess in vivo therapeutic efficacy of LAP-IL-17F mutant in collagen induced arthritis mice, three mouse analogues of human IL-17F mutant were developed. Of these, (Q158R) IL-17F mutant displayed IL-17 agonistic properties, (H157R) IL-17F mutant could not be expressed in vitro and the truncated IL-17F mutant could not bind to mouse IL-17RC. Investigation of in vivo expression and pharmacokinetics of intravenous hydrodynamically delivered human full-length and LAP-IL-17 plasmid DNAs in naïve SCID and C57BL/6 mice showed that human IL-17 transgene expression was detectable in mouse serum at 48 hours post-delivery. The transgene expression however declined rapidly over the next two weeks. The local expression of transgene in C57BL/6 airpouch lavage fluid was less than 5% of its systemic levels. Taken together, the findings of the study warrant an investigation of in vivo therapeutic efficacy of human (H161F) IL-17F mutant in a suitable preclinical RA model, such as RA synovium/SCID mice.