PDCD1 and melanoma: In fact, this new‐generation fusion toxin has also seen a good synergy effect together with anti‐PD‐1 to treat melanoma.[107] The risk of vascular leakage and production issues (e.g., purity and aggregation) limit the clinical application of denileukin diftitox (Ontak), which is a fusion protein composed of the bacterial toxin DT and anti‐IL‐2.