Patent ID: 8623356

Claim:
An isolated pair of demibodies comprising a first demibody and a second demibody, said first demibody comprising: an antigen-binding portion of a first immunoglobulin that interacts with a first antigen on a target cell; a first non-cytotoxic portion of an Fc domain; and a first member of a complementary leucine zipper pair; said second demibody comprising: an antigen-binding portion of a second immunoglobulin that interacts with a second antigen on the target cell; a second non-cytotoxic portion of an Fc domain; and a second member of a complementary leucine zipper pair; wherein the pair of demibodies is configured so that the first and second non-toxic portions of said first and second demibodies are only able to combine to generate a cytotoxic Fc domain after the first and second demibodies are bound to the first and second antigens on the target cell.