Provided is a bispecific recombinant protein, comprising a high affinitytumor-targeting arm and a low affinity fusion protein blocking the interactionofCD47 with SIRP.alpha.. The antibody corresponding to the high affinity tumor-targetingarm does not bind to CD47, and its binding affinity to the target antigen onthe tumorcell is at least 6 times as great as the binding affinity of monomer fusionproteinhomodimer, corresponding to the low affinity fusion protein blocking theinteractionof CD47 with SIRP.alpha., to a CD47 on the tumor cell, wherein the lowaffinity fusionprotein blocking the interaction of CD47 with SIRP.alpha. comprises aSIRP.alpha. extracellulartruncation. Also provided are nucleic acid molecules encoding recombinantproteinsand the use of the recombinant proteins and nucleic acid molecules in themanufactureof a medicament for treating tumors.
