Discloses a bispecific single chain antibody molecule comprising a first binding domain which is capable of binding to an epitope of human and Callithrix jacchus, Saguinis Oedipus or Saimiri sciureus CD3&egr； (epsilon), wherein the epitope SEQ ID NO: 2 ( QDGNEEMGGITQTPYKVSISGTTVILT), SEQ ID NO: 4 (QDGNEEMGDTTQNPYKVSISGTTVTLT). SEQ ID NO: 6 (QDGNEEMGDTTQNPYKVSISGTTVTLT) or SEQ ID NO: 8 (QDGNEEIGDTTQNPYKVSISGTTVTLT) and comprises the amino acid sequence Gln-Asp-Gly-Asn-Glu and a second binding domain capable of binding to prostate-specific membrane antigen (PSMA) wherein the antibody comprises specific CDR regions.
