First-in-human Study of SAR443579 Infusion in Male and Female Children and Adult Participants With Relapsed or Refractory Acute Myeloid Leukemia (R/​R AML), B-cell Acute Lymphoblastic Leukemia (B-ALL), High Risk-myelodysplasia (HR-MDS), or Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN)

• Drug: SAR443579

Inclusion Criteria

• Participant must be at least 1 year (for France: 2 years) old at the time the trial participant or legal guardian signs the informed consenta process in which a patient receives detailed information about a procedure or treatment, including its potential risks, benefits, and alternatives. The patient then has the opportunity to understand the information and voluntarily agree to the procedure or treatment. form and will be assigned as follows:
  • Adult arm: aged at least 18 years old.
  • Pediatric arm: aged 1 (for France: 2 years) to less than 18 years old.
• Adult and Pediatric Arms: Escalation and Expansion/Optimization Cohorts A1, A2, C, D: Confirmed diagnosisthe process of identifying a disease based on signs and symptoms, patient history and medical test results of primary or secondary AML (any subtype) according to World Health Organization (WHO) 2022 classification. Participants with AML must meet one of the following criteria, a), b), c) or d) and are limited to those with no available (or are ineligible) therapy with known clinical benefit.

  a) Primary Induction Failure (PIF) AML, defined as disease refractory to one of the following, i or ii.

  i) An intensive induction attempt, per institution. Induction attempts include high-dose and/or standard-dose cytarabine ± an anthracyclines/anthracenedione ± an anti-metabolite, with or without growth factor or targeted therapymedication that targets specific molecular features of cancer cells containing regimens.

ii) For adults who are age 75 years or older, or who have comorbidities that preclude use of intensive induction chemotherapya cancer treatment that uses drugs to kill or slow the growth of cancer cells, while minimising damage to healthy cells; PIF is defined as AML refractory to one of the following less intensive regimens, 1 or 2:

1. 4 cycles of hypomethylating agents (HMA) or
2. 2 cycles HMA + venetoclax b) Early relapsethe return of disease (ER) AML, defined as AML in relapse with CR, CRh or CRi duration less than 6 months on prior induction treatment c) Leukemia in first or higher relapse d) For participants aged 1 (for France: 2 years) to less than 18 years old, primary induction failure is defined as disease refractory after two cycles of induction therapy.
   • Adult Arm (Escalation and Expansion/Optimization Cohorts B and Japan Cohort C only): Confirmed diagnosis of MDS, meeting the following criteria:
     1. intermediate or high-risk category as per a Revised International Prognostic Scoring System (IPSS-R) AND
     2. confirmed CD123 + expression status determined by local institutional standards AND
     3. limited to those with no available (or are ineligible) therapy with known clinical benefit.
   • Pediatric arms escalation part and Japan Cohort C only: Confirmed diagnosis of CD123+ BALL without extramedullary lesions that have no available (or are ineligible) therapy with known clinical benefit. Participants with non-CNS chloromatous disease are not allowed in the study.
   • Body weight at least 10 kg.
   • Pediatric arm and escalation part only: Confirmed diagnosis of BPDCN according to World Health Organization (WHO) 2022 classification, who have relapsed or refractory disease with no available (or are ineligible) therapy with known clinical benefit.
   • Japan participants (Cohort C): Participant must be at least 18 years old at the time the trial participant signs the informed consent form