Interfant-21: International collaborative treatment protocol for infants under one year with KMT2A-rearranged acute lymphoblastic leukemia or mixed phenotype acute leukemia

The primary objective of this study is to improve the outcome in terms of **event-free survival (EFS)** for infants newly diagnosed with KMT2A-rearranged acute lymphoblastic leukemia (ALL), compared to historical results from the Interfant-06 protocol. This is clinically relevant as it aims to enhance survival rates and reduce the incidence of adverse events in this vulnerable patient population.

Secondary objectives include:

• Estimating overall survival (OS) and comparing it with historical results of the Interfant-06 protocol, both overall and by risk group.
• Determining outcomes according to risk group and comparing them with historical results of the Interfant-06 protocol.
• Assessing outcomes in terms of secondary endpoint 3, considering the protocol-specific definition of resistance.
• Evaluating the response to different treatment phases in terms of minimal residual disease (MRD) response.
• Evaluating the incidence of CD19 negative relapses.
• Evaluating the incidence of myeloid lineage switches.
• Describing the toxicity associated with each treatment phase.
• Describing long-term cardiotoxicity.
• Evaluating survival after relapse, overall and by risk group.

The clinical trial involves a total of **54 participants** diagnosed with **acute lymphoblastic leukemia** (ALL), specifically focusing on those with KMT2A-rearranged (KMT2A-r) infant ALL. The study population includes both male and female subjects who are **365 days of age or younger** at the time of diagnosis. Participants were selected based on their diagnosis of B-precursor ALL or B-cell MPAL (single lineage) according to the WHO classification of tumors of hematopoietic and lymphoid tissues. The trial includes a vulnerable population, as it involves infants. Written informed consent was obtained from the parents or legally authorized guardians of the participants. The study does not specify any particular lifestyle considerations such as diet or physical activity for the participants.

The clinical trial is designed to evaluate the efficacy of a treatment protocol for infants under one year with **acute lymphoblastic leukemia** (ALL) or mixed phenotype acute leukemia (MPAL) with KMT2A-rearrangement. The trial employs a randomized, double-blind, controlled design to ensure the reliability and validity of the results. The primary objective is to improve event-free survival (EFS) compared to historical data from the Interfant-06 protocol. The trial is expected to run until December 31, 2030, with recruitment having commenced on October 3, 2022.

Participants will undergo a series of study visits, beginning with an inclusion (screening) visit to confirm eligibility based on criteria such as age (≤ 365 days at diagnosis) and diagnosis of B-precursor ALL or B-cell MPAL. Written informed consent from a parent or legal guardian is required. Follow-up visits will be scheduled to monitor the participants' response to treatment, assess adverse events, and collect data on secondary endpoints such as overall survival (OS) and minimal residual disease (MRD) response. The end-of-study visit will conclude the participant's involvement, with data collection on long-term outcomes.

The expected length of participant involvement varies depending on individual response to treatment and the occurrence of any adverse events. Conditions that may lead to early termination from the study include resistance to induction therapy, relapse, or the development of a second malignancy. Participants will be closely monitored throughout the trial to ensure safety and adherence to the protocol. The trial's comprehensive design aims to provide robust data on the efficacy and safety of the treatment protocol for this vulnerable patient population.

The clinical trial involves the administration of several experimental medications, each with specific pharmaceutical forms, dosages, and routes of administration. **Methotrexate** is provided in two forms: Methotrexaat Teva 10 mg tablets and Emthexate PF 100 mg/ml injection. The tablets are administered orally with a maximum daily dose of 20 mg/m² and a total dose of 1560 mg/m² over a period of 78 weeks. The injection is administered intravenously with a maximum daily dose of 5000 mg/m² and a total dose of 10000 mg/m² over 2 days.

**Cytarabine** is administered as Cytarabine Accord 100 mg/ml solution for injection or infusion. This medication is given intravenously with a maximum daily dose of 6000 mg/m² and a total dose of 22850 mg/m² over 51 days.

**Tioguanine** is available as Thiosix 20 mg and 10 mg tablets, administered orally. The maximum daily dose is 60 mg/m², with a total dose of 1680 mg/m² over 28 days.

**Dexamethasone** is provided in two tablet forms: Dexamethason Teva 1.5 mg and 0.5 mg. Both are administered orally with a maximum daily dose of 6 mg/m² and a total dose of 126 mg/m² over 21 days.

**Mitoxantrone** is administered as Mitoxantron Sandoz 2 mg/ml solution for infusion. This is given intravenously with a maximum daily dose of 12 mg/m² and a total dose of 36 mg/m² over 3 days.

**Blinatumomab** is provided as BLINCYTO 38.5 micrograms powder for concentrate and solution for infusion. It is administered intravenously with a maximum daily dose of 15 µg/m² and a total dose of 840 µg/m² over 8 weeks.

**Prednisone** is administered as Prednison Auro 5 mg tablets, taken orally with a maximum daily dose of 60 mg/m² and a total dose of 420 mg/m² over 7 days.

**Asparaginase** is available as Spectrila 10,000 U powder for concentrate for solution for infusion. It is administered intravenously with a maximum daily dose of 1500 IU and a total dose of 6000 IU over 4 days.

**Hydrocortisone** is administered as Solu-Cortef Powder for Solution for Injection or Infusion 100 mg. This is given via intrathecal use with a maximum daily dose of 20 mg and a total dose of 400 mg over 20 days.

**Daunorubicin** is provided as Cerubidine 20 mg solution for injection. It is administered intravenously with a maximum daily dose of 75 mg/m² and a total dose of 2250 mg/m² over 30 days.

**Cyclophosphamide Monohydrate** is available as ENDOXAN I.V. solution for injection in 500 mg and 1000 mg forms. It is administered intravenously with a maximum daily dose of 1000 mg/m² and a total dose of 3000 mg/m² over 4 days.

**Etoposide** is administered as Toposin 20 mg/ml solution for intravenous infusion. The maximum daily dose is 100 mg/m², with a total dose of 500 mg/m² over 5 days.

**Mercaptopurine** is provided as Xaluprine 20 mg/ml oral suspension. It is administered orally with a maximum daily dose of 60 mg/m² and a total dose of 29330 mg/m² over 84 weeks.

**Vincristine Sulfate** is administered as Vincristinesulfaat Teva 1 mg/ml solution for injection. It is given intravenously with a maximum daily dose of 0.05 mg/kg and a total dose of 0.20 mg/kg over 4 days.

**Methylprednisolone** is provided as Solu-Medrone powder and solvent for solution for injection or concentrate for infusion 1000 mg/vial. It is administered via intrathecal use with a maximum daily dose of 4 mg and a total dose of 80 mg over 20 days.

Efficacy in the clinical trial will be assessed primarily through the measurement of **event-free survival (EFS)**, which is defined as the time from diagnosis to resistance to induction, relapse, death from any cause, or second malignancy, whichever occurs first. This endpoint will be evaluated to compare the outcomes of newly diagnosed infants with KMT2A-rearranged acute lymphoblastic leukemia (ALL) against historical data from the Interfant-06 protocol. Secondary endpoints include overall survival (OS), which is the time from diagnosis to death from any cause, and will be estimated for the entire study cohort and according to risk group. Additional secondary endpoints involve the cumulative incidence of resistance to induction, relapse, death in complete remission, and second malignancy. The study will also assess minimal residual disease (MRD) response, the proportion of CD19 negative relapses, myeloid lineage switches, and adverse events, including grade ≥3 adverse events during blinatumomab courses and grade ≥2 cardiac disorders at 2 and 5 years post-diagnosis. The OS after first relapse will also be evaluated, defined as the time from first relapse to death from any cause. These efficacy parameters will be collected and analyzed throughout the trial duration, with specific timepoints and methods as outlined in the trial protocol.