Tafasitamab (MOR00208) in Pediatric Patients With Relapsed or Refractory Acute B Lineage Leukemia

Inclusion Criteria:

* Age ≥ 3 years and \< 18 years at enrollment
* B-lineage (CD19 positive) ALL (B, pro-B, pre-B or c-ALL)
* Patients must have either

  * underwent a first allogeneic stem cell transplantation after relapse with one of the following very high-risk somatic molecular alterations:

    * KMT2A::AFF1 \[t(4;11) rearrangement
    * TP53 alteration (mutation/deletion)
    * low hypodiploidy (\<40 chromosomes, evident or masked)
    * TCF3-PBX1 \[t(1;19)\]
    * TCF3::HLF \[t(17;19)\] and irrespective of MRD after SCT or
  * underwent a first allogeneic stem cell transplantation or a CAR T-cell therapy with newly emerging or persistent MRD load posttransplant / post CAR T- cell-treatment or
  * have received stem cell transplantation without having reached a sufficient molecular remission prior to transplant (defined as MRD ≥10E-4) irrespective of MRD after SCT or
  * underwent a second or subsequent allogeneic stem cell transplantation irrespective of MRD after SCT
* Females of childbearing potential (FCBP1) must agree

  * to utilize two reliable forms of contraception simultaneously or practice complete abstinence from heterosexual contact for at least 3 months before starting study drug, while participating in the study (including dose interruptions), and for at least 3 months after study treatment discontinuation and must agree to regular pregnancy testing during this timeframe
  * to abstain from breastfeeding during study participation and 3 months after study drug discontinuation.
* Males must agree

  * to use a latex condom during any sexual contact with FCBP while participating in the study and for 3 months following discontinuation from this study, even if he has undergone a successful vasectomy
  * to refrain from donating semen or sperm during study participation and for 3 months after discontinuation from this study treatment.

Exclusion Criteria:

* Frank relapse (\>5% leukemic blasts)
* Philadelphia chromosome-positive (Ph+) ALL
* Ejection fraction \<25% on echocardiography
* Cystatin C-clearance \<40ml/min
* Liver function abnormalities with bilirubin \>4 mg/dL and elevation of transaminases higher than 400 U/L
* Severe infection (HIV, Chronic active viral hepatitis), tests have to be conducted at screening
* Acute GvHD III-IV or extensive chronic GvHD
* The following immunosuppressive drugs (≥ 1 week of administration):

steroids ≥ 1mg/kg body weight, cytostatics (except intrathecal/ intracerebroventricular application for CNS treatment)

* Application of other experimental therapy modalities in the last 4 weeks
* Significant psychiatric disabilities, uncontrolled seizure disorders or severe peripheral neuropathy/ leukoencephalopathy
* Signs of autoimmune disease (i.e. idiopathic thrombocytopenic purpura, autoimmune hemolytic anemia)
* Subjects that do not agree to refrain from donating blood while on study drug
* Concurrent severe or uncontrolled medical disease which by assessment of the treating physician could compromise participation in the study
* Women during pregnancy and lactation
* History of hypersensitivity to the investigational medicinal product or to any drug with similar chemical structure or to any excipient present in the pharmaceutical form of the investigational medicinal product.