AGONISTIC ANTIBODY DIRECTED AGAINST HUMAN THROMBOPOIETIN RECEPTOR

摘要

Disclosed is an agonistic antibody directed against human thrombopoietin receptor (also referred to as "human c-Mpl). Specifically, the antibody has a constant region having a set of amino acid sequences selected from the following items (1) to (3): (1) amino acid sequences for a heavy-chain constant region and a light-chain constant region of a human antibody; (2) an amino acid sequence for a human antibody heavy-chain constant region in which the domain is replaced by one of other human antibody subclass and an amino acid sequence for a human antibody light-chain constant region; and (3) a set of amino acid sequences having the deletion, substitution, addition or insertion of one or several amino acid residues in each of the amino acid sequences shown in (1) and (2), and the antibody has a variable region capable of binding to a human thrombopoietin receptor to activate the receptor. The antibody also has the following properties: (a) the antibody can induce the formation of a colony at a concentration of 10,000 ng/mL or less in the CFU-MK colony formation assay using a human umbilical cord blood CD34+ cell; and (b) the antibody has the maximum activity higher than that of PEG-rHuMGDF by 50% or more and a 50% effective concentration (EC50) of 100 nM or less in the cell growth assay using an UT7/TPO cell. Also disclosed is a pharmaceutical composition for the treatment of thrombocytopenia, which comprises the antibody.