A PCSK9-binding antibody that structurally mimics the EGF(A) domain of LDL-receptor reduces LDL cholesterol in vivo.
Proprotein convertase subtilisin-like/kexin type 9 (PCSK9) regulates LDL cholesterol levels by inhibiting LDL receptor (LDLr)-mediated cellular LDL uptake. We have identified a fragment antigen-binding (Fab) 1D05 which binds PCSK9 with nanomolar affinity. The fully human antibody 1D05-IgG2 completely blocks the inhibitory effects of wild-type PCSK9 and two gain-of-function human PCSK9 mutants, S127R and D374Y. The crystal structure of 1D05-Fab bound to PCSK9 reveals that 1D05-Fab binds to an epitope on the PCSK9 catalytic domain which includes the entire LDLr EGF(A) binding site. Notably, the 1D05-Fab CDR-H3 and CDR-H2 loops structurally mimic the EGF(A) domain of LDLr. In a transgenic mouse model (CETP/LDLr-hemi), in which plasma lipid and PCSK9 profiles are comparable to those of humans, 1D05-IgG2 reduces plasma LDL cholesterol to 40% and raises hepatic LDLr protein levels approximately fivefold. Similarly, in healthy rhesus monkeys, 1D05-IgG2 effectively reduced LDL cholesterol 20%-50% for over 2 weeks, despite its relatively short terminal half-life (t(1/2) = 3.2 days). Importantly, the decrease in circulating LDL cholesterol corresponds closely to the reduction in free PCSK9 levels. Together these results clearly demonstrate that the LDL-lowering effect of the neutralizing anti-PCSK9 1D05-IgG2 antibody is mediated by reducing the amount of PCSK9 that can bind to the LDLr.
Ni
Yan G
YG
Department of Cardiovascular Diseases, Merck Research Laboratories, Rahway, New Jersey, USA. yan_ni@merck.com
Di Marco
Stefania
S
Condra
Jon H
JH
Peterson
Laurence B
LB
Wang
Weirong
W
Wang
Fubao
F
Pandit
Shilpa
S
Hammond
Holly A
HA
Rosa
Ray
R
Cummings
Richard T
RT
Wood
Dana D
DD
Liu
Xiaomei
X
Bottomley
Matthew J
MJ
Shen
Xun
X
Cubbon
Rose M
RM
Wang
Sheng-ping
SP
Johns
Douglas G
DG
Volpari
Cinzia
C
Hamuro
Lora
L
Chin
Jayne
J
Huang
Lingyi
L
Zhao
Jing Zhang
JZ
Vitelli
Salvatore
S
Haytko
Peter
P
Wisniewski
Douglas
D
Mitnaul
Lyndon J
LJ
Sparrow
Carl P
CP
Hubbard
Brian
B
Carfí
Andrea
A
Sitlani
Ayesha
A
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001665:Binding Sites; D053480:Cholesterol Ester Transfer Proteins / Q000378:metabolism; D008078:Cholesterol, LDL / Q000097:blood*; D015200:Fluoroimmunoassay; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry / Q000494:pharmacology*; D007074:Immunoglobulin G / Q000276:immunology / Q000378:metabolism; D008253:Macaca mulatta; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D011973:Receptors, LDL / Q000737:chemistry* / Q000378:metabolism; D012697:Serine Endopeptidases / Q000737:chemistry / Q000276:immunology*
D000911:Antibodies, Monoclonal; C506642:CETP protein, human; D053480:Cholesterol Ester Transfer Proteins; D008078:Cholesterol, LDL; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D011973:Receptors, LDL; C472125:PCSK9 protein, human; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D012697:Serine Endopeptidases