Solid phase synthesis of polyamine conjugates in the search for new inhibitors of trypanothione reductase and transfection agents for gene therapy

The enzyme trypanothione reductase (TR) is unique to the parasitic protozoa known as Trypanosomes and Leishmania. This enzyme and its substrate trypanothione (N1,N8-bis(glutathionyl)spermidine) play an essential role in the maintenance of a reducing cellular environment within these parasites. The trypanothione reductase (TR) system is made more attractive as a target for rational drug design since the high substrate specificity of TR is different compared to human glutathione reductase (GR).This thesis describes the synthesis of a range of immobilised polyamines (Spermine, Spermidine and Norspermidine) which allowed the synthesis of a number of polyamine derivatives. A series of TR inhibitors were identified using directed solid phase chemistry, with compounds based on a natural product Kukoamine A as a lead structure. Several potent inhibitors of TR were discovered with Ki values as low as 76 nM.A bio-compatible safety-catch linker was developed for the solid phase synthesis and release of transfection agents. The links were evaluated using both peptides and small organic molecules on polystyrene and TentaGel resin.The library of transfection agents based on bile acid and long chain fatty acid were prepared. The biological activity of these compounds was screened using green fluorescent protein (GFP) as a marker. The result showed that the bile acid (N1-(3α, 7α-dihydroxy-5β-cholane-24-carbonyl)-1,12-diamino-4,9-diazdecane) was the most potent compound. The transfection efficiency with relatively low toxicity and ease of preparation make it a promising candidate for general gene therapy!