SYNTHESIS, ACTIVITY, AND STRUCTURE-ACTIVITY RELATIONSHIP STUDIES OF NOVEL CATIONIC LIPIDS FOR DNA TRANSFER

We have designed and synthesized original cationic lipids for gene del ivery. A synthetic method on solid support allowed easy access to unsy mmetrically monofunctionalized polyamine building blocks of variable g eometries. These polyamine building blocks were introduced into cation ic lipids. To optimize the transfection efficiency in the novel series , we have carried out structure-activity relationship studies by intro duction of variable-length lipids, of variable-length linkers between lipid and cationic moiety, and of substituted linkers. We introduce th e concept of using the linkers within cationic Lipids molecules as car riers of side groups harboring various functionalities (side chain ent ity), as assessed by the introduction of a library composed of cationi c entities, additional lipid chains, targeting groups, and finally the molecular probes rhodamine and biotin for cellular traffic studies. T he transfection activity of the products was assayed in vitro on Hela carcinoma, on NIH3T3, and on CV1 fibroblasts and in vivo on the Lewis Lung carcinoma model. Products from the series displayed high transfec tion activities. Results indicated that the introduction of a targetin g side chain moiety into the cationic lipid is permitted. A primary ph ysicochemical characterization of the DNA/lipid complexes was demonstr ated with this leading compound. Selected products from the series are currently being developed for preclinical studies, and the labeled li popolyamines can be used to study the intracellular traffic of DNA/cat ionic lipid complexes.