PRF1 and neoplasm: Additionally, when applying T cell engagers to treat solid tumors, on‐target/off‐tumor and off‐target/off‐tumor toxicity should be considered.[25] In this study, the administration of Nb‐TriTE in the absence of tumor cells does not trigger perforin and granzyme B secretion (Figure 4B) or increase cytokines release (Figure 4C) from human PBMCs in vitro.