SNX-4414

To evaluate the ability of SNX‐7081, a novel small molecule inhibitor of Hsp90, to block components of inflammation, including cytokine production, protein kinase activity, and angiogenic signaling. A close analog was evaluated in preclinical in vivo models of rheumatoid arthritis (RA).

SNX‐7081 binding to Hsp90 was characterized in Jurkat cells and RA synovial fibroblasts (RASFs). Inhibition of NF‐κB nuclear translocation was evaluated in cellular systems, using lipopolysaccharide (LPS), tumor necrosis factor α, or interleukin‐1β stimulation. Suppression of cytokine production in THP‐1 cells, human umbilical vein endothelial cells, and RASFs was studied. Disruption of MAPK signaling cascades by SNX‐7081 following growth factor stimulation was assessed. SNX‐7081 was tested in 2 relevant angiogenesis assays: platelet‐derived growth factor activation of fibroblasts and LPS‐induced nitric oxide (NO) release in J774 macrophages. A close analog, SNX‐4414, was evaluated in rat collagen‐induced arthritis and adjuvant‐induced arthritis, following oral treatment.

SNX‐7081 showed strong binding affinity to Hsp90 and expected induction of Hsp70. NF‐κB nuclear translocation was blocked by SNX‐7081 at nanomolar concentrations, and cytokine production was potently inhibited. Growth factor activation of ERK and JNK signaling was significantly reduced by SNX‐7081. NO production was also sharply inhibited. In animal models, SNX‐4414 fully inhibited paw swelling and improved body weight. Scores for inflammation, pannus formation, cartilage damage, and bone resorption returned to normal.

The present results demonstrate that a small molecule Hsp90 inhibitor can impact inflammatory disease processes. The strong in vivo efficacy observed with SNX‐4414 provides preclinical validation for consideration of Hsp90 inhibitors in the treatment of RA.