sh-Polypeptide-157 is a single chain recombinant human peptide produced by fermentation in E. coli. The starting gene is synthesized to be identical to the human gene which codes for Chain E of the scFv region of light chain from K202.B, the bispecific antibody, used as such or adapted to the production host. It contains a maximum of 478 amino acids which may contain disulfide bonds and/or glycosylation. The protein consists of the proper sequence of the 20 standard amino acids.