Targeted siRNA Delivery and mRNA Knockdown Mediated by Bispecific Digoxigenin-binding Antibodies.
Bispecific antibodies (bsAbs) that bind to cell surface antigens and to digoxigenin (Dig) were used for targeted small interfering RNA (siRNA) delivery. They are derivatives of immunoglobulins G (IgGs) that bind tumor antigens, such as Her2, IGF1-R, CD22, and LeY, with stabilized Dig-binding variable domains fused to the C-terminal ends of the heavy chains. siRNA that was digoxigeninylated at its 3'end was bound in a 2:1 ratio to the bsAbs. These bsAb-siRNA complexes delivered siRNAs specifically to cells that express the corresponding antigen as demonstrated by flow cytometry and confocal microscopy. The complexes internalized into endosomes and Dig-siRNAs separated from bsAbs, but Dig-siRNA was not released into the cytoplasm; bsAb-targeting alone was thus not sufficient for effective mRNA knockdown. This limitation was overcome by formulating the Dig-siRNA into nanoparticles consisting of dynamic polyconjugates (DPCs) or into lipid-based nanoparticles (LNPs). The resulting complexes enabled bsAb-targeted siRNA-specific messenger RNA (mRNA) knockdown with IC(50) siRNA values in the low nanomolar range for a variety of bsAbs, siRNAs, and target cells. Furthermore, pilot studies in mice bearing tumor xenografts indicated mRNA knockdown in endothelial cells following systemic co-administration of bsAbs and siRNA formulated in LNPs that were targeted to the tumor vasculature.Molecular Therapy - Nucleic Acids (2012) 1, e45; doi:10.1038/mtna.2012.39; published online 18 September 2012.
Roche Pharma Research and Early Development (pRED), Large Molecule Research, Penzberg, Germany.
Britta
B
Schneider
Michael
M
Grote
Matthias
M
John
Alexander
A
Haas
Birgit
B
Bramlage
Ludger M
LM
Ickenstein
Kerstin
K
Jahn-Hofmann
Frieder
F
Bauss
Weijun
W
Cheng
Rebecca
R
Croasdale
Karin
K
Daub
Simone
S
Dill
Eike
E
Hoffmann
Wilma
W
Lau
Helmut
H
Burtscher
James L
JL
Ludtke
Silke
S
Metz
Olaf
O
Mundigl
Zane C
ZC
Neal
Werner
W
Scheuer
Jan
J
Stracke
Hans
H
Herweijer
Ulrjch
U
Brinkmann