Moxetumomab pasudotox-tdfk, also called HA22 or CAT-8015, an anti-CD22 monoclonal antibody fused to Pseudomonas exotoxin (PE38), is another FDA-approved antibody-drug conjugate for targeting CD22.384,385 It is approved for application in patients with refractory or relapsed hairy cell leukemia (HCL). This evidence concerns the gene CD22 and hairy cell leukemia.