- Ni YG, Di Marco S, Condra JH, Peterson LB, Wang W, Wang F, Pandit S, Hammond HA, Rosa R, Cummings RT, Wood DD, Liu X, Bottomley MJ, Shen X, Cubbon RM, Wang SP, Johns DG, Volpari C, Hamuro L, Chin J, Huang L, Zhao JZ, Vitelli S, Haytko P, Wisniewski D, Mitnaul LJ, Sparrow CP, Hubbard B, Carfi A, Sitlani A
- A proprotein convertase subtilisin-like/kexin type 9 (PCSK9)-binding antibody that structurally mimics the EGF(A) domain of LDL-receptor reduces free circulating PCSK9 and LDL-cholesterol.
- J Lipid Res. 2010 Oct 19.
- Proprotein convertase subtilisin-like/kexin type 9 regulates LDL cholesterol levels by inhibiting LDL-receptor mediated cellular LDL uptake. We have identified a fragment of antibody (Fab) 1D05 which binds PCSK9 with nanomolar affinity. The fully human antibody 1D05-IgG2 completely blocks the inhibitory effects of wildtype 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 LDL-receptor EGF(A) binding site. Notably, the 1D05-Fab CDR-H3 and CDR-H2 loops structurally mimic the EGF(A) domain of LDL-receptor. In a transgenic mouse model (CETP/LDL-receptor-hemi) with plasma lipid and PCSK9 profiles comparable to those of humans, 1D05-IgG2 reduces plasma LDL cholesterol 40% and raises hepatic LDL-receptor protein levels approximately five fold. Similarly, in healthy rhesus monkeys, 1D05-IgG2 effectively reduces LDL cholesterol 20-50% for over two weeks, despite its relatively short terminal half life (t1/2=3.2 days). Importantly, the decrease in circulating LDL cholesterol corresponds closely to the reduction in free PCSK9 levels. Together these results clearly demonstrate the LDL-lowering effect of the neutralizing anti-PCSK9 1D05-IgG2 is mediated by reducing the amount of PCSK9 that can bind to the LDL-receptor.