Chemically modified short interfering hybrids (siHYBRIDS):: Nanoimmunoliposome delivery in vitro and in vivo for RNAi of HER-2

A blunt-ended 19-mer short interfering hybrid (siHybrid) (H) comprised of sense-DNA/antisense-RNA targeting HER-2 mRNA was encapsulated in a liposomal nanoplex with anti-transferrin receptor single-chain antibody fragment (TfRscFv) as the targeting moiety for clinically relevant tumor-specific delivery. In vitro delivery to a human pancreatic cell line (PANC-1) was shown to exhibit sequence-specific inhibition of 48-h cell growth with an IC50 value of 37 nM. The inhibitory potency of this siHybrid was increased (IC50 value of 7.8 nM) using a homologous chemically modified siHybrid ( mH ) in which the 19-mer sense strand had the following pattern of 2 '-deoxyinosine (dI) and 2'-O-methylribonucleotide (2'-OMe) residues: 5'-d(TITIT)-2'OMe(GCGGUGGUU)-d(GICIT). These modifications were intended to favor antisense strand-mediated RNAi while mitigating possible sense strand-mediated off-target effects and RNase H-mediated cleavage of the antisense RNA strand. The presently reported immunoliposomal delivery system was successfully used in vivo to inhibit HER-2 expression, and thus induce apoptosis in human breast carcinoma tumors (MDA-MB-435) in mice upon repeated i.v. treatment at a dose of 3 mg/kg of H or mH . The in vivo potency of modified siHybrid mH appeared to be qualitatively greater than that of H , as was the case in vitro .