GTB 3550 (OXIS 3550) is a single-chain, triple compound-specific scFv recombinant fusion protein (Tri-specific NK cell engagers; TriKE®) composed of anti-CD16 and anti-CD33 antibodies and an IL-15 variant developed by GT Biopharma (owner of Oxis Biotech) for the treatment of patients with R/R acute myelogenous leukemia (AML) and high-risk myelodysplastic syndrome (MDS) (98–101). Here, IL15 is linked to acute myeloid leukemia.