• Age ≤21 years old

• Relapsed/refractory CD123+ disease defined as follows:

∙ AML/MDS

• Relapsed disease: Patients developing recurrent disease after a first complete remission (CR)

• Refractory disease: Patients not achieving a CR after 2 cycles of induction chemotherapy

∙ B-cell ALL

• Relapsed disease that is CD123 positive and CD19 negative/dim or patients otherwise ineligible for CD19 directed therapies including

‣ Patients in 2nd or greater relapse

⁃ Patients with relapse after allogeneic HSCT

• Refractory disease that is CD123 positive and CD19 negative/dim or patients otherwise ineligible for CD19 directed therapies

∙ T-cell All • Relapsed refractory disease that is CD123 positive

∙ BPDCN

∙ • Relapsed/refractory disease that has failed front-line therapy

• Estimated life expectancy of \>12 weeks

• Karnofsky or Lansky (age-dependent) performance score ≥50

• Patients with a history of prior allogeneic HCT must be clinically recovered from prior HCT therapy, have no evidence of active GVHD and have not received a donor lymphocyte infusion (DLI) within the 28 days prior to apheresis

• Patient must have an identified, suitable HCT donor

• For females of child-bearing age:

• Not lactating with intent to breastfeed

• Not pregnant with negative serum pregnancy test within 7 days prior to enrollment

• Meets eligibility criteria to undergo autologous apheresis, or have previously undergone autologous apheresis

• Age≤21 years old

• Detectable disease that is CD123+ (at least MRD+ disease)

• Estimated life expectancy of \>8 weeks

• Karnofsky or Lansky (age-dependent) performance score≥50

• Patients with a history of prior allogeneic HCT must be clinically recovered from prior HCT therapy, have no evidence of active GVHD and have not received a donor lymphocyte infusion (DLI) within the 28 days prior to planned infusion

• Patient must have an identified, suitable HCT donor

• Adequate cardiac function defined as left ventricular ejection fraction \>40%, OR shortening fraction ≥25%

• EKG without evidence of clinically significant arrhythmia

• Adequate renal function defined as creatinine clearance or radioisotope GFR ≥50 ml/min/1.73m2 (GFR ≥40 ml/min/1.73m2 if \< 2 years of age)

• Adequate pulmonary function defined as forced vital capacity (FVC)≥50% of predicted value; or pulse oximetry≥92% on room air if patient is unable to perform pulmonary function testing

• Total Bilirubin≤3 times the upper limit of normal for age, except in subjects with Gilbert's syndrome

• Alanine aminotransferase (ALT) OR aspartate aminotransferase (AST) ≤5 times the upper limit of normal for age

• Has recovered from all NCI CTAE grade III-IV, non-hematologic acute toxicities from prior therapy

• For females of child-bearing age

‣ Not lactating with intent to breastfeed

⁃ Not pregnant with negative serum pregnancy test within 7 days prior to enrollment

• If sexually active, agreement to use birth control until 3 months after T- cell infusion. Male partners should use a condom.

• Available autologous transduced T-cell product that has met GMP release criteria