Figure 2.

Enhancement in blood residence and tissue accumulation is strongly correlated to the molecular weight of PK-modifying anchors

(A) (Left) Schematic of fully modified fluorescently labeled asymmetric siRNA and of 8-mer oligonucleotide anchors covalently attached to a variety of high-molecular-weight PEG moieties. (Right) Gel-shift assay depicting binding and hybridization of each variant of the 8-mer anchor to the parent siRNA duplex (21–13), highlighting the differences in migration according to size. (B and C) Wild-type FVB/N female mice treated intravenously (28.5 nmol, ∼13 mg/kg) with siRNA duplexes containing different PEG sizes hybridized to the parent asymmetric compound through an 8-mer anchor. Concentrations of the guide strand in the blood and tissues were assessed by PNA-based hybridization assay and values normalized to the MW of the parent unconjugated siRNA duplex for comparison. (B) (Left) Concentration-time profiles of the parent siRNA using different size PK-modifying anchors. Serial blood samples were collected from the saphenous vein. (Right) Pharmacokinetic parameters calculated based on non-compartmental analysis. (C) Tissue biodistribution profile relative to the parent siRNA when using different size PK-modifying anchors at 48 h post-injection. n = 4–5/group. Mean ± Standard deviation (SD).