The effect of FUT-175 (nafamstat mesilate) on C3a, C4a and C5a generation in vitro and inflammatory reactions in vivo

Abstract

FUT-175 is a synthetic protease inhibitor and an inhibitor of the classical and alternate pathways of complement activation. In human serum, FUT-175 inhibited C3a, C4a and C5a generation induced by heat aggregated IgG, zymosan and Cobra venom factor with IC50 values in the range of 3-43 microM depending on the stimulus and the fragments. To assess in vivo anti-inflammatory activity, inflammatory reactions induced in the skin of rabbits were quantitated by using 125I-albumin extravasation, 51Cr-labelled leukocyte accumulation and 86RbCl accumulation as a measure of hyperemia. Infusion of FUT-175 at 2 mg/kg/h inhibited all three parameters by 50-80% in dermal reactions induced by killed E. coli, zymosan, immune complexes, the reversed Arthus reaction, zymosan activated plasma (ZAP), f-norleu-leu-phe (FNLP) and LTB4. In contrast, the response to endotoxin (0.1 microgram) was not effected by FUT-175 treatment. The effect of FUT-175 was comparable to that of local or systemic therapy with indomethacin, but unlike indomethacin, the effect of FUT-175 was not reversed by local PGE2 administration. Furthermore, indomethacin and FUT-175 had additive anti-inflammatory effects. These results suggest that although FUT-175 is a potent inhibitor of C3a, C4a and C5a generation, it has novel and broad anti-inflammatory effects, possibly through actions in addition to complement inhibition as indicated by inhibition of FNLP-, LTB4- and ZAP-induced reactions.

Part of Endotoxins research, CIRS biomarkers research · Curated by Lauren Lowenstein, The Biotoxin Lady

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