A New Antibody (Tafasitamab) for Children and Adolescents with Relapsed or Refractory B-ALL Following Stem Cell Transplantation

Acute lymphoblastic leukemia (ALL) is the most common form of childhood blood cancer. In this disease, certain white blood cells—known as lymphocytes—undergo malignant changes and displace the normal blood-forming bone marrow. Lymphocytes are divided into B cells and T cells, which are responsible for defending against foreign substances, such as pathogens. This study examines cases of ALL in which B cells are affected (B-ALL), which is the more common form. Typical symptoms include increased susceptibility to infections, a tendency to bleed, reduced physical performance, and dizziness. Treatment for ALL typically follows established therapy protocols. If certain risk factors are present or if the response to standard therapy is insufficient, a stem cell transplant (SCT). In this procedure, the patient’s diseased blood system is destroyed using intensive chemotherapy and, if necessary, radiation therapy, and then a new blood system from a donor (allogeneic SCT) is transplanted. Despite potential side effects, this is a highly effective procedure that can cure many patients. However, there are cases in which an SCT does not produce an adequate response or the disease becomes active again after a short time. To date, there have been insufficient treatment options for this situation.

The Anti-CD19-ALL study is investigating the drug tafasitamab, an antibody that specifically targets a protein (CD19) on the surface of B cells, thereby destroying the malignant cancer cells. Tafasitamab is already used to treat other conditions and is well tolerated by adults. The study aims first to determine a safe dose of tafasitamab with few side effects in children (Phase 1) and, in a second step (Phase 2), to investigate the drug’s effect on the course of the disease. The drug is intended to help effectively combat recurrent cancer cells, thereby reducing the risk of relapse and improving long-term survival rates. There is only one study arm, meaning all patients will receive tafasitamab and will be aware of the treatment (open-label). In the first phase, a safe and effective dose of the antibody will be determined in children (49-day observation period). In the second phase, the study will examine how well the drug works and what side effects occur. To this end, the number of cancer cells in the blood and bone marrow (minimal residual disease, MRD) will be monitored for up to 1.5 years (545 days) after the start of treatment. In both phases, patients will receive the previously determined dose of tafasitamab every two weeks, with additional doses during the first 3 cycles.

Children and adolescents under the age of 18 who have CD19-positive acute lymphoblastic B-cell leukemia are eligible to participate. The disease must have already been treated with an allogeneic stem cell transplant, but without sufficient success. This means that patients continue to show signs of the disease or have suffered a relapse.