TPBG and neoplasm: As scFv5T4::SpeCD203A and SpeCD203A showed similar activity in vitro (Figure 4a), the inability of SpeCD203A to impact tumor size or metastatic disease indicates that the scFv5T4 moiety of the fusion protein was required for in vivo targeting of 5T4+ HT-29 cells (Figures 2A, 5C and 5D).