Intravitreal delivery of oligonucleotides by sterically stabilized liposomes

PURPOSE.. The efficacy of sterically stabilized liposomes for delivering a model phosphodiester oligonucleotide intravitreally was investigated in the rabbit, METHODS. Ocular distribution and clearance from the vitreous humor of a model 16-mer oligothyraidylate (pdT16) were evaluated in the rabbit by radioactivity measurements after intravitreal injection of either a solution or liposomes containing the [P-33] pdT16 oligonucleotide. The integrity of pdT16 was investigated using a competitive hybridization assay. RESULTS. The residual concentration of the [P-33] pdT16 oligonucleotide Within the Ocular tissues was significantly increased after intravitreal administration of the liposomal suspension compared with I simple solution, Administration of liposome-encapsulated pdT16 oligonucleotide resulted in sustained release into the Vitreous and the retina-choroid compared with release from the solution and in a reduced distribution to nontarget tissues (sclera, lens), In addition, liposomes protected the phosphodiester oligonucleotide against degradation. This was not observed after administration of the free oligonucleotide. CONCLUSIONS. The intravitreal injection of a phosphodiester oligonucleotide encapsulated within liposomes is a new way of delivering intact oligonucleotide to the eye in a controlled manner. This offers interesting prospects for the treatment of retinal diseases.