ANTI-PCSK9 ANTIBODIES WITH pH-DEPENDENT BINDING CHARACTERISTICS

Abstract

The present invention provides antibodies and antigen-binding fragments thereof that specifically bind human proprotein convertase subtilisin/kexin type 9 (hPCSK9) which do not exhibit enhanced binding affinity for hPCSK9 at acidic pH relative to neutral pH. In certain embodiments, the antibodies and antigen-binding fragments of the invention bind hPCSK9 with a lower affinity at acidic pH than at neutral pH.

1 - 5 . (canceled) 
     
     
         6 . An isolated antibody or antigen-binding fragment thereof that specifically binds human proprotein convertase subtilisin/kexin type 9 (hPCSK9), wherein the antibody or antigen-binding fragment thereof does not exhibit an enhanced binding affinity for hPCSK9 at an acidic pH relative to a neutral pH, as measured by surface plasmon resonance. 
     
     
         7 . The isolated antibody or antigen-binding fragment of  claim 6 , wherein the antibody or antigen-binding fragment thereof binds hPCSK9 with a lower affinity at acidic pH than at neutral pH. 
     
     
         8 . The isolated antibody or antigen-binding fragment of  claim 6 , wherein the antibody or antigen-binding fragment thereof binds hPCSK9 with a shorter t½ at acidic pH than at neutral pH, as measured by surface plasmon resonance. 
     
     
         9 . The isolated antibody or antigen-binding fragment of  claim 6 , wherein the antibody or antigen-binding fragment thereof: (a) binds hPCSK9 with a lower affinity at acidic pH than at neutral pH; and (b) binds hPCSK9 with a shorter t½ at acidic pH than at neutral pH, as measured by surface plasmon resonance. 
     
     
         10 . An isolated antibody or antigen-binding fragment thereof that specifically binds human proprotein convertase subtilisin/kexin type 9 (hPCSK9), wherein the antibody or antigen-binding fragment thereof: (a) binds hPCSK9 with a lower affinity at acidic pH than at neutral pH; and (b) exhibits a serum half-life which is greater than the serum half-life of an anti-hPCSK9 antibody that does not exhibit lower affinity binding to hPCSK9 at acidic pH. 
     
     
         11 . An isolated antibody or antigen-binding fragment thereof that specifically binds human proprotein convertase subtilisin/kexin type 9 (hPCSK9), wherein the antibody or antigen-binding fragment thereof: (a) binds hPCSK9 with a shorter t1/2 at acidic pH than at neutral pH, as measured by surface plasmon resonance; and (b) exhibits a serum half-life which is greater than the serum half-life of an anti-hPCSK9 antibody that does not exhibit a shorter t1/2 at acidic pH than at neutral pH, as measured by surface plasmon resonance. 
     
     
         12 . An isolated antibody or antigen-binding fragment thereof that specifically binds human proprotein convertase subtilisin/kexin type 9 (hPCSK9), wherein the antibody or antigen-binding fragment thereof: (a) binds hPCSK9 with a lower affinity at acidic pH than at neutral pH; (b) binds hPCSK9 with a shorter t1/2 at acidic pH than at neutral pH, as measured by surface plasmon resonance; and (c) exhibits a serum half-life which is greater than the serum half-life of an anti-hPCSK9 antibody that does not exhibit lower affinity binding to hPCSK9 at acidic pH. 
     
     
         13 . The isolated antibody or antigen-binding fragment of  claim 6 , wherein the antibody or antigen-binding fragment thereof is obtained by immunizing a mouse with a hPCSK9 antigen, isolating an antibody or antigen-binding fragment of an antibody that specifically binds hPCSK9, and testing the antibody or antigen-binding fragment for lower affinity binding at acidic pH as compared to neutral pH using an in vitro assay. 
     
     
         14 . The isolated antibody or antigen-binding fragment of  claim 13 , wherein the in vitro assay is a surface plasmon resonance assay conducted at neutral pH and at acidic pH. 
     
     
         15 . The isolated antibody or antigen-binding fragment of  claim 13 , wherein the in vitro assay is a PCSK9/LDLR blocking assay conducted at neutral pH and at acidic pH. 
     
     
         16 . The isolated antibody or antigen-binding fragment of  claim 10 , wherein the antibody or antigen-binding fragment thereof exhibits a serum half-life of greater than 200 hours when administered to a subject at a dose of 5 mg/kg. 
     
     
         17 . The isolated antibody or antigen-binding fragment of  claim 11 , wherein the antibody or antigen-binding fragment thereof exhibits a serum half-life of greater than 200 hours when administered to a subject at a dose of 5 mg/kg. 
     
     
         18 . The isolated antibody or antigen-binding fragment of  claim 7 , wherein administration of the antibody or antigen-binding fragment thereof to an animal at a dose of 5 mg/kg reduces LDL-C level by at least 50% relative to baseline LDL-C level, and sustains the reduction in LDL-C level for up to 28 days after administration. 
     
     
         19 . The isolated antibody or antigen-binding fragment of  claim 7 , wherein administration of the antibody or antigen-binding fragment thereof to an animal at a dose of 15 mg/kg reduces LDL-C level by at least 50% relative to baseline LDL-C level, and sustains the reduction in LDL-C level for up to 90 days after administration. 
     
     
         20 . The isolated antibody or antigen-binding fragment of  claim 7 , wherein the antibody or antigen-binding fragment thereof does not bind mouse PCSK9 (mPCSK9, SEQ ID NO:757), rat PCSK9 (rPCSK9, SEQ ID NO:763), or hamster PCSK9 (maPCSK9, SEQ ID NO:762), at pH 7.4 or at pH 5.5. 
     
     
         21 . The isolated antibody or antigen-binding fragment of  claim 7 , wherein the antibody or antigen-binding fragment thereof binds to the same epitope on hPCSK9 as an antibody comprising heavy and light chain CDR amino acid sequences having SEQ ID NOs:220, 222, 224, 228, 230 and 232. 
     
     
         22 . The isolated antibody or antigen-binding fragment of  claim 7 , wherein the antibody or antigen-binding fragment thereof competes for binding to hPCSK9 with an antibody comprising heavy and light chain CDR amino acid sequences having SEQ ID NOs:220, 222, 224, 228, 230 and 232. 
     
     
         23 . The isolated antibody or antigen-binding fragment of  claim 7 , wherein the antibody or antigen-binding fragment thereof comprises the heavy and light chain CDRs of a HCVR/LCVR amino acid sequence pair having SEQ ID NOs: 218/226. 
     
     
         24 . The isolated antibody or antigen-binding fragment of  claim 7 , wherein the antibody or antigen-binding fragment thereof comprises heavy and light chain CDR amino acid sequences having SEQ ID NOs:220, 222, 224, 228, 230 and 232. 
     
     
         25 . The isolated antibody or antigen-binding fragment of  claim 24 , wherein the antibody or antigen-binding fragment thereof comprises an HCVR having the amino acid sequence of SEQ ID NO:218 and an LCVR having the amino acid sequence of SEQ ID NO:226.