STABILITY AND PHARMACOKINETIC CHARACTERISTICS OF OLIGONUCLEOTIDES MODIFIED AT TERMINAL LINKAGES IN MICE

To construct the strategy for delivery systems that can control in viv o disposition of antisense oligonucleotides, we studied the stability and basic pharmacokinetic characteristics of oligonucleotides. Decathy midylic acid (T-10), a model oligodeoxynucleotide, and its derivatives , 5'-biotin-T-10 (5'B-T-10) and 3'-methoxyetyethyiam 5'-biotin-T-10 (3 'M5'B-T-10), containing phosphoroamidate modification at 3'- and/or 5' -terminal internucleoside linkages, were synthesized. In phosphate-buf fered saline (PBS, pH 7.4) containing 10% mouse serum, unmodified T-10 was degraded with a half-life of 45 minutes; the degradation half-liv es of 5'B-T-10 and 3'M5'B-T-10 were 11 and 30 h, respectively. In mous e whole blood, 3'M5'B-T-10 was relatively stable, and 45% remained int act after 1 h incubation. After intravenous injection of [H-3]3'M5'B-T -10 into mice at a dose of 1 mg/kg, the radioactivity was rapidly clea red from plasma with a half-life of 2 minutes and accumulated in the k idney, liver, and gallbladder. About 30% of the dose was excreted in t he urine within 60 :minutes. A much more rapid degradation of [H-3]3'M 5'B-T-10 was observed in vivo than expected from in vitro experiments: more than 90% of the radioactivity in plasma was degradation product at 2 minutes after injection. These results suggested that enzymatic d egradation occurred in some compartments in addition to tile blood poo l. The apparent urinary excretion clearance of [H-3]3'M5'B-T-10 was cl ose to that of inulin, when!as the apparent hepatic uptake clearance w as much greater than that of inulin and comparable to that of dextran sulfate, which is taken up by the liver by scavenger receptors for pol yanions. Thus, the present study demonstrated that the disposition pro cesses to be controlled involve stability, urinary excretion, and hepa tic uptake for the development of oligonucleotide delivery systems.