Antisense oligonucleotides are short synthetic fragments of genes that are
able to inhibit gene expression after being internalized by cells. They can
therefore be used as antiviral compounds particularly, for the treatment o
f ocular viral infections (i.e. Herpes simplex virus or Cytomegalovirus, CM
V). Antisense oligonucleotides are however poorly stable in biological flui
ds and their intracellular penetration is limited. Although oligonucleotide
s are now currently used in therapeutics for the treatment of CMV by intrav
itreal injection (Vitravene(R)), their main drawbacks impose to repeat the
number of administrations which can be very harmful and damaging. A system
that is able to permit a protection of oligonucleotides against degradation
and their slow delivery into the vitreous would be more favorable for impr
oving patient compliance. The use of liposomes for intravitreal administrat
ion can be very promising since these lipid vesicles are able to protect ol
igonucleotides against degradation by nucleases and they allow to increase
the retention time of many drugs in the vitreous. In this review, the poten
tialities of liposomes far the intravitreal delivery of oligonucleotides wi
ll be discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.