Highly effective antifibrotic compound discovered as a contaminant in cefixime preparations: preliminary characterization

There are no approved drugs for specific treatment of excessive type I collagen synthesis in organ fibrosis. The discovery that biosynthesis of type I collagen in fibrosis is regulated by binding of LARP6 to the unique sequence found in type I collagen mRNAs, the 5 stem-loop (5SL), prompt the search for small molecule inhibitors of LARP6 binding. A contaminant in some commercial preparations of the third-generation cephalosporin, cefixime, has been discovered that inhibits LARP6/5SL interaction in vitro and type I procollagen secretion by cells and organoids in culture. The activity, termed ATO-OA, forms stable non-colloidal nano-entities (NE). ATO-OA NE inhibit the binding of LARP6 to 5SL with the IC50 of 3-4 {micro}g/ml and are equally effective in the dissociation of preassembled LARP6/5SL complex as in the inhibition of its formation. ATO-OA NE target the RRM domain of LARP6 to alter its conformation. In cultured cells, ATO-OA NE suppresses type I procollagen secretion into the cellular medium and causes intracellular retention of the protein. The effect of ATO-OA NE in vivo is LARP6 dependent, because the LARP6 knockout cells or the cells which make type I procollagen without 5SL show no effect of ATO-OA. In cultured organoids of human pancreatic adenocarcinoma cells ATO-OA NE diminished type I collagen production at [~]62.5 {micro}g/ml. These results suggest that the discovery of ATO-OA NE as potent and specific inhibitor of LARP6 may be a breakthrough towards development of antifibrotic drugs directly targeting type I collagen biosynthesis.