Antibody single-chain variable region (scFv) sequences derived from amatuximab recognizing MSLN and from either blinatumomab or AMG330 targeting CD3 were used to engineer and express two MSLN/CD3-targeting BsAbs: MSLN AMA -CD3 L2K and MSLN AMA -CD3 AMG respectively...Chemotherapy (DA) consisted of 3 doses of 1.5 mg/kg daunorubicin iv and 5 doses of 50 mg/kg cytarabine ip...Conclusion These data validate the efficacy of MSLN-targeting BsAbs in PDX models with endogenous MSLN expression. Because prior MSLN-directed therapies appeared safe in humans, MSLN-targeting BsAbs could be ideal immunotherapies for MSLN-positive pediatric AML patients.