Bi-Specific Monovalent Diabodies That are Capable of Binding CD19 and CD3, and Uses Thereof

A CD19×CD3 bi-specific monovalent Fc diabody capable of specific binding to CD19 and to CD3, wherein the diabody comprises a first, a second and a third polypeptide chain, wherein said polypeptide chains form a covalently bonded complex, and wherein:

• I. said first polypeptide chain comprises, in the N-terminal to C-terminal direction:
• A. a Domain IA, comprising
• (1) a sub-Domain (IA1), which comprises a VL Domain capable of binding to either CD19 (VLCD19) or CD3 (VLCD3);
• and
• (2) a sub-Domain (IA2), which comprises a VH Domain capable of binding to either CD19 (VHCD19) or CD3 (VHCD3);
• wherein said sub-Domains IA1 and IA2 are separated from one another by a polypeptide linker, and are either
• (a) VLCD19 and VHCD3;
• or
• (b) VLCD3 and VHCD19;
• B. a Domain IB, comprising a charged Heterodimer-Promoting Domain, wherein said Domain IB is separated from said Domain 1A by a polypeptide linker;
• C. a Domain IC, comprising a CH2-CH3 Domain of an antibody;
• and
• II. said second polypeptide chain comprises, in the N-terminal to C-terminal direction:
• A. a Domain HA, comprising
• (1) a sub-Domain (IIA1), which comprises a VL Domain capable of binding to either CD19 (VLCD19) or CD3 (VLCD3);
• and
• (2) a sub-Domain (IIA2), which comprises a VH Domain capable of binding to either CD19 (VHCD19) or CD3 (VHCD3);
• wherein said sub-Domains IIA1 and IIA2 are separated from one another by a polypeptide linker, and are:
• (a) VLCD19 and VHCD3, if said sub-Domains IA1 and IA2 are VLCD3 and VHCD19;
• or
• (b) VLCD3 and VHCD19, if said sub-Domains IA1 and IA2 are VLCD19 and VHCD3;
• B. a Domain IIB, comprising a charged Heterodimer-Promoting Domain, wherein said Domain JIB is separated from said Domain IIA by a polypeptide linker, and wherein said charged Heterodimer-Promoting Domain of said Domain IB and said charged Heterodimer-Promoting Domain of said Domain IIB have opposite charges;
• and
• III. said third polypeptide chain comprises, in the N-terminal to C-terminal direction a Domain IIIC that comprises a CH2-CH3 Domain of an antibody;
• wherein said VLCD19 and said VHCD19 domains form a CD19 binding domain, and said VLCD3 and VHCD3 domains form a CD3 binding domain;
• and said CH2-CH3 Domains of said first and third polypeptide chains form an Fc domain capable of binding to an Fc receptor, thereby forming said CD19×CD3 bi-specific monovalent diabody.