title: Titrating haemophilia B phenotypes using siRNA strategy: evidence that antithrombotic activity is separated from bleeding liability.
abstract: Haemophilia A and B are characterised by a life-long bleeding predisposition, and several lines of evidence suggest that risks of atherothrombotic events may also be reduced. Establishing a direct correlation between coagulation factor levels, thrombotic risks and bleeding propensity has long been hampered by an inability to selectively and specifically inhibit coagulation factor levels. Here, the exquisite selectivity of gene silencing combined with a gene knockout (KO) approach was used to define the relative contribution of factor IX (fIX) to thrombosis and primary haemostasis in the rat. Using a lipid nanoparticle (LNP) formulation, we successfully delivered fIX siRNAs to the liver by intravenous administration. The knockdown (KD) of target gene mRNA was achieved rapidly (within 24 hour post-siRNA dosing), sustained (maintained for at least 7 days post dosing) and not associated with changes in mRNA expression levels of other coagulation factors. We found that intermediate levels of liver fIX mRNA silencing (60-95 %) translating into a 50-99 % reduction of plasma fIX activity provided protection from thrombosis without prolonging the cuticle bleeding time. Over 99 % inhibition of fIX activity was required to observe increase in bleeding, a phenotype confirmed in fIX KO rats. These data provide substantial evidence of a participation of fIX in the mechanisms regulating thrombosis prior to those regulating primary haemostasis, therefore highlighting the potential of fIX as a therapeutic target. In addition, hepatic mRNA silencing using LNP-encapsulated siRNAs may represent a promising novel approach for the chronic treatment and prevention of coagulation-dependent thrombotic disorders in humans.
authors: Joseph M
authors: JM
authors: Metzger
authors: Marija Tadin-Strapps, Department of Genetics and Pharmacogenomics, Merck Research Laboratories, Merck & Co., Inc., 33 Avenue E Louis Pasteur, Boston, MA 02115, USA, Tel.:+1 617 992 2339, E-mail: marija_tadin-strapps@merck.com.
authors: Marija
authors: M
authors: Tadin-Strapps
authors: Anil
authors: A
authors: Thankappan
authors: Walter R
authors: WR
authors: Strapps
authors: Marti
authors: M
authors: DiPietro
authors: Karen
authors: K
authors: Leander
authors: Zuo
authors: Z
authors: Zhang
authors: Myung K
authors: MK
authors: Shin
authors: John
authors: J
authors: Levorse
authors: Kunal
authors: K
authors: Desai
authors: Yiming
authors: Y
authors: Xu
authors: KehDih
authors: K
authors: Lai
authors: Weizhen
authors: W
authors: Wu
authors: Zhu
authors: Z
authors: Chen
authors: Tian-Quan
authors: TQ
authors: Cai
authors: Nina
authors: N
authors: Jochnowitz
authors: Ross
authors: R
authors: Bentley
authors: Lizbeth
authors: L
authors: Hoos
authors: Yuchen
authors: Y
authors: Zhou
authors: Laura
authors: L
authors: Sepp-Lorenzino
authors: Dietmar
authors: D
authors: Seiffert
authors: Patrick Andre, Cardiometabolic Disease, Merck & Co., Inc., Galloping Hill Road, Kenilworth, NJ 07033, USA, Tel.:+1 908 740 7329, E-mail: Patrick.andre@merck.com.
authors: Patrick
authors: P
authors: Andre
mesh_terms: D000818:Animals; D002460:Cell Line; D002712:Chlorides; D004195:Disease Models, Animal; D005164:Factor IX / Q000235:genetics* / Q000378:metabolism; D005290:Ferric Compounds; D005786:Gene Expression Regulation; D005838:Genotype; D002836:Hemophilia B / Q000097:blood / Q000235:genetics*; D006470:Hemorrhage / Q000097:blood / Q000235:genetics*; D006487:Hemostasis / Q000235:genetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D010641:Phenotype; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics* / Q000378:metabolism; D000067492:RNAi Therapeutics; D051381:Rats; D017207:Rats, Sprague-Dawley; D055647:Rats, Transgenic; D013927:Thrombosis / Q000097:blood / Q000139:chemically induced / Q000235:genetics / Q000517:prevention & control*; D013997:Time Factors; D014162:Transfection
chemical_list: D002712:Chlorides; D005290:Ferric Compounds; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D005164:Factor IX; C024555:ferric chloride
keywords: coagulation; factor fIX; haemostasis; siRNA; thrombosis