Janet M. Leeds

Comparison of pharmacokinetics and tissue disposition of an antisense phosphorothioate oligonucleotide targeting human Ha-ras mRNA in mouse and monkey

The plasma pharmacokinetics and tissue disposition of ISIS 2503 were studied in mice following single and multiple bolus intravenous (iv) injections of 1-50 mg/kg, and in monkeys following single and multiple 2-h iv infusions of 1-10 mg/kg and bolus iv injections of 1 mg/kg of ISIS 2503. ISIS 2503 and its metabolites were measured in plasma, urine, and tissues using solid-phase extraction followed by capillary gel electrophoresis (CGE). In both species, the plasma clearance of ISIS 2503 was characterized by rapid distribution to tissues, and to a lesser extent, metabolism. The plasma clearance in mice was at least two-fold more rapid than in monkeys at equivalent doses. The plasma disposition (t1/2) increased with dose. The highest concentrations of oligonucleotide were consistently observed in the kidney and liver in both species. At equivalent doses, tissue concentrations in monkeys were much higher than tissue concentrations in mice. Urinary excretion of total oligonucleotide was a minor elimination pathway in both species at doses < 10 mg/kg. However, urinary excretion of total oligonucleotide in mice was increased to 12-29% as dose increased from 20 to 50 mg/kg.

Pharmacokinetics and Tissue Disposition in Monkeys of an Antisense Oligonucleotide Inhibitor of Ha-Ras Encapsulated in Stealth Liposomes

AbstractPurpose. This study examined the pharmacokinetics and tissue distribution of an antisense oligonucleotide ISIS 2503, formulated in stealth (pegylated) liposomes (encapsulated) or in phosphate-buffered saline (unencapsulated). Methods. Encapsulated or unencapsulated ISIS 2503 was administered to rhesus monkeys by intravenous infusion. The concentrations of ISIS 2503 and metabolites in blood, plasma, and tissue samples were determined by capillary gel electrophoresis. Results. Plasma concentrations of encapsulated ISIS 2503 decreased mono-exponentially after infusion with a mean half-life of 57.8 hours. In contrast, the concentration of unencapsulated ISIS 2503 in plasma decreased rapidly with a mean half-life of 1.07 hours. Both encapsulated and unencapsulated ISIS 2503 distributed widely into tissues. Encapsulated ISIS 2503 distributed primarily to the reticulo-endothelial system and there were few metabolites observed. In contrast, unencapsulated ISIS 2503 distributed rapidly to tissue with highest concentration seen in kidney and liver. Nuclease-mediated metabolism was extensive for unencapsulated oligonucleotide in plasma and tissues. Conclusions. The data suggest that stealth liposomes protect ISIS 2503 from nucleases in blood and tissues, slow tissue uptake, and slow the rate of clearance from the systemic circulation. These attributes may make these formulations attractive for delivering oligonucleotides to sites with increased vasculature permeability such as tumors or sites of inflammation.

Pharmacokinetics in mice of a [3H]-labeled phosphorothioate oligonucleotide formulated in the presence and absence of a cationic lipid

Abstract Formulation of phosphorothioate oligonucleotides with cationic lipids enhances the pharmacological activity of the oligonucleotide in cellular based assay systems. The effect of cationic lipid formulation on the pharmacokinetic behavior of a phosphorothioate oligodeoxynucleotide in mice was investigated in the present study. In the absence of any formulation, the phosphorothioate oligonucleotide exhibited a plasma T 1 2 of 10.2 min and was broadly distributed to many peripheral tissues with liver, kidney, skeletal muscle and skin being the major organs of disposition. Formulating the oligonucleotide with a DMRIE/DOPE (50:50) formulation, such that there was a 2.5:1 positive charge excess on the lipidic structure, resulted in marked changes in the distribution of the oligonucleotide. Significant increases in the amount of oligonucleotide distributed to liver, lung and spleen were observed when the oligonucleotide was formulated with cationic lipids. These results suggest that it is possible to change the biodistribution of phosphorothioate oligodeoxynucleotides by formulating with cationic liposomes.

Pharmacokinetic Properties of Phosphorothioate Oligonucleotides

Abstract The pharmacokinetic parameters determined for different phosphorothioate oligonucleotides were compared. The data suggest that phosphorothioate pharmacokinetics are primarily determined by chemical class. The pharmacokinetics are consistent across species, show dose-dependency, and are independent of sequence.