Antiviral activity and ocular kinetics of antisense oligonucleotides designed to inhibit CMV replication

PURPOSE. To compare the antiviral activity and ocular distribution of first - and second-generation antisense oligonucleotides intended for the treatme nt of cytomegalovirus (CMV) retinitis. METHODS. The antiviral activity of ISIS 13312 and ISIS 2922 (Isis Pharmaceu ticals, Inc., Carlsbad, CA) against 10 clinical CMV isolates was compared w ith a plaque-reduction assay. The ocular pharmacokinetics were compared aft er intravitreal injection in rabbits (36-90 mug) and monkeys (125-500 mug). Vitreous and/or retina were collected after single and multiple injections to characterize ocular distribution, clearance, and accumulation. Oligonuc leotide concentrations were measured by capillary gel electrophoresis and i mmunohistochemical techniques. RESULTS. ISIS 13312 and ISIS 2922 demonstrated comparable antiviral activit y that was consistent among the 10 clinical isolates examined (50% inhibito ry concentration [IC50], <1 muM). Activity was independent of the resistanc e of CMV isolates to DNA polymerase inhibitors. After intravitreal injectio n, the kinetics of ISIS 2922 and ISIS 13312 were characterized by clearance from vitreous and distribution to the retina; however, ISIS 2922 was clear ed more quickly from the retina than ISIS 13312. The half-life of ISIS 1331 2 in the monkey retina was approximately 2 months. Retinal concentrations o f ISIS 13312 were dose dependent, with approximately a twofold increase in concentration after once-monthly doses compared with single-dose concentrat ions. Immunohistochemical analysis indicated that both oligonucleotides wer e efficiently distributed to numerous ocular tissues, including retina, cil iary body, and optic nerve. CONCLUSIONS. ISIS 13312 possesses antiviral activity and pharmacokinetic pr operties that favor its use as a therapeutic agent in treatment of CMV reti nitis. The half-life of ISIS 13312 in retina is longer than that of ISIS 29 22, potentially allowing for less frequent administration.