CLEARANCE KINETICS, BIODISTRIBUTION, AND ORGAN SATURABILITY OF PHOSPHOROTHIOATE OLIGODEOXYNUCLEOTIDES IN MICE

We examined the dynamics of removal from circulation, tissue distribut ion, and persistence of phosphorothioate oligodeoxynucleotides (S-ODN) anti-tumor-necrosis-factor and a control of random sequence (randomer ) in mice. After intravenous injection, the majority (96%) of S-ODN cl eared rapidly from the circulation in the first two phases. In the fir st phase, 37.8 +/- 2.3% of the radioactivity bad a mean half-life (t(1 /2)) of 2.0 +/- 0.4 minutes. In the second phase, 58.1 +/- 1.5% of the radioactivity cleared with t(1/2) of 12.6 +/- 0.2 minutes. The catabo lic phase, constituting a minor proportion (4.1 +/- 0.8% of tbe total radioactivity), had a mean t(1/2) of 2.7 +/- 0.5 hours. At a low dose (1 mu g) tissue distribution of both S-ODN anti-tumor-necrosis-factor and randomer were similar. The liver and kidneys were the major organs involved in uptake and removal of S-ODN. Autoradiographic studies sho wed the litter Kupffer cells to be the major site of uptake and renal urinary space for elimination. The clearance rate from the circulation wets increased with the dose of S-ODN. In contrast, the fraction of r adioactivity localized in the kidneys, liver, and spleen was decreased with increase in dosage. Furthermore, at a high dose (200 mu g), the tissue distribution of the S-ODN anti-tumor-necrosis-factor differed s ignificantly from the randomer. These findings have general significan ce in showing that the liver and kidneys are the major organs for remo val of S-ODN and these organs are saturable at high doses. In addition , the results have specific importance in defining different parameter s, dose and base composition, that affect utilization of antisense oli gonucleotides for controlling gene expression in vivo.