The present invention provides compositions and methods relating to or derived from antigen binding proteins capable of inhibiting PCSK9 binding to LDLR and having increased pH sensitivity, improved binding affinity and/or increased in vivos half life. In embodiments, the antigen binding proteins specifically bind PCSK9 and have increased pH sensitivity, improved binding affinity and/or increased in vivos half life. In some embodiments, an antigen binding protein is a fully human, humanized, or chimeric antibodies, binding fragments and derivatives of such antibodies, and polypeptides that specifically bind PCSK9 Other embodiments provide nucleic acids encoding such antigen binding proteins, and fragments and derivatives thereof, and polypeptides, cells comprising such polynucleotides, methods of making such antigen binding proteins, and fragments and derivatives thereof, and polypeptides, and methods of using such antigen binding proteins, fragments and derivatives thereof, and polypeptides, including methods of treating or diagnosing subjects suffering from hypercholesterolemia and related disorders or conditions.
