Evaluation of Gemtuzumab Ozogamicin and Drug Combination in Pediatric Acute Myeloid Leukemia: A NOPHO-DB-SHIP Consortium Study

The primary objective of the CHIP-AML22 Master protocol is to enhance the overall event-free survival (EFS) for children and adolescents with newly diagnosed **Acute Myeloid Leukemia** (AML), compared to the NOPHO-DBH AML-2012 protocol. This is clinically significant as improving EFS can lead to better long-term outcomes and quality of life for pediatric patients with AML. Additionally, the study aims to assess whether the addition of gemtuzumab ozogamicin (GO) to the first induction course improves early anti-leukemic efficacy in CD33-positive AML patients. Furthermore, the study seeks to demonstrate the non-inferiority in disease-free survival of two courses of consolidation therapy, by omitting HA3E, compared to three courses, in the entire standard-risk group eligible for this randomization.

Secondary objectives include:

• For the entire study population, the aim is to improve short-term efficacy by evaluating different endpoints such as overall survival (OS), disease-free survival (DFS), and the cumulative incidence of relapse (CIR), as well as to decrease treatment-related toxicity.
• In the induction randomization, the study evaluates differences in anti-leukemic efficacy across the total group, both arms, and subgroups defined by the intensity of CD33-expression, CD33 SNPs, and cytogenetics. It also assesses the safety of adding GO to the induction course 1, compared to no-GO.
• In the consolidation randomization, the study aims to improve the safety of consolidation treatment, compare the consumption of healthcare resources, and compare OS and CIR.

The clinical trial involves a total of **200 participants** diagnosed with **Acute Myeloid Leukemia** (AML). The study population includes both male and female subjects, ranging in age from 1 day to 18 years at the time of initial diagnosis. Participants are required to have newly diagnosed AML of de novo origin, not secondary to bone marrow failure or therapy-related causes. The trial population was selected based on their ability to comply with scheduled follow-up and manage toxicity, with informed consent obtained from patients or their legal guardians. The study includes a vulnerable population, as it involves children and adolescents. Lifestyle considerations such as diet and physical activity are not specified. Key inclusion criteria include CD33 positivity of leukemic blasts for induction randomization and stratification to the Standard Risk Group for consolidation randomization. The trial aims to improve event-free survival (EFS) in this demographic, assessing the efficacy of adding GO to the induction course and evaluating consolidation therapy courses.

The clinical trial is designed to evaluate the efficacy and safety of various treatment regimens in pediatric patients newly diagnosed with **Acute Myeloid Leukemia** (AML). This is a randomized, open-label, controlled trial with a complex design, aiming to improve event-free survival (EFS) in children and adolescents. The trial is expected to run until March 31, 2036, with recruitment starting on August 2, 2023. Participants will be involved in the study for a maximum treatment period of up to 26 months, depending on the specific treatment arm they are assigned to.

The trial includes several key phases: an initial screening visit, multiple follow-up visits, and an end-of-study visit. The screening visit will determine eligibility based on criteria such as age (1 day to 18 years), de novo AML diagnosis, and the ability to comply with follow-up and toxicity management. Participants will be randomized into different treatment arms, with some receiving additional agents like **gemtuzumab ozogamicin** during the induction phase. The primary endpoints include EFS and disease-free survival (DFS), with secondary endpoints assessing overall survival (OS), cumulative toxicity, and other efficacy measures.

Study visits will be scheduled to monitor treatment response and safety. Follow-up visits will include assessments of bone marrow blast counts and minimal residual disease (MRD) levels. The end-of-study visit will evaluate the overall treatment outcomes and any long-term effects. Participants may be withdrawn from the study early if they experience unacceptable toxicity, fail to comply with the protocol, or withdraw consent. The trial's design ensures rigorous monitoring and data collection to achieve its objectives while maintaining participant safety.

The clinical trial involves the administration of several experimental medications, each with specific pharmaceutical forms, dosages, routes, and frequencies of administration. **Daunorubicin hydrochloride** is provided as a 20 mg powder for intravenous injection. It is administered intravenously with a maximum daily dose of 60 mg/m² and a total dose not exceeding 180 mg/m² over a treatment period of up to 3 weeks. This medication is manufactured by Zentiva Pharma UK Limited.

**Methylprednisolone** is available as Solu-Medrone, a powder and solvent for solution for injection or concentrate for solution for infusion, with a concentration of 1000 mg per vial. It is administered intrathecally with a maximum daily dose of 4800 µg and a total dose of 43200 µg over a 9-week period. This product is provided by Pfizer Healthcare Ireland.

**Gemtuzumab ozogamicin** is supplied as MYLOTARG, a 5 mg powder for concentrate for solution for infusion. It is administered intravenously with a maximum daily dose of 3 mg/m² and a total dose of 6 mg/m² over a 2-week period. This medication is produced by Pfizer Europe MA EEIG.

**Etoposide phosphate** is available as ETOPOPHOS, a 100 mg powder for the preparation of an infusion solution. It is administered intravenously with a maximum daily dose of 150 mg/m² and a total dose of 1200 mg/m² over a 13-week period. This product is manufactured by Cheplapharm Arzneimittel GmbH.

**Prednisolone sodium succinate** is provided as Di-Adreson-F Aquosum, a 25 mg powder for solution for injection. It is administered intrathecally with a maximum daily dose of 6 mg and a total dose of 54 mg over a 9-week period. This medication is produced by ACE Pharmaceuticals BV.

**Methotrexate** is available as a 2.5 mg/ml injection solution. It is administered intrathecally with a maximum daily dose of 12 mg and a total dose of 120 mg over a 10-week period. This product is provided by Hospira UK Limited.

**Fludarabine phosphate** is supplied as a 50 mg powder for solution for injection or infusion. It is administered intravenously with a maximum daily dose of 30 mg/m² and a total dose of 150 mg/m² over a 5-week period. This medication is manufactured by Actavis UK Limited.

**Mitoxantrone** is available as a 2 mg/ml concentrate for solution for infusion. It is administered intravenously with a maximum daily dose of 10 mg/m² and a total dose of 55 mg/m² over an 8-week period. This product is provided by Accord Healthcare Limited.

**Hydrocortisone** is provided as Solu-Cortef, a 100 mg powder for solution for injection or infusion. It is administered intrathecally with a maximum daily dose of 24 mg and a total dose of 216 mg over a 9-week period. This medication is produced by Pfizer Healthcare Ireland.

**Etoposide** is available as a 20 mg/ml concentrate for solution for infusion. It is administered intravenously with a maximum daily dose of 150 mg/m² and a total dose of 1700 mg/m² over a 13-week period. This product is manufactured by Accord Healthcare Limited.

**Dexrazoxane** is supplied as CARDIOXANE, a 500 mg powder for solution for infusion. It is administered intravenously with a maximum daily dose of 600 mg/m² and a total dose of 4550 mg/m² over an 11-week period. This medication is produced by Clinigen Healthcare Ltd.

**Cytarabine** is available as a 100 mg/ml solution for injection or infusion. It is administered intravenously with a maximum daily dose of 6000 mg/m² and a total dose of 36800 mg/m² over a 26-week period. This product is provided by Accord Healthcare Limited.

The efficacy of the clinical trial will be assessed using several primary and secondary endpoints. The primary endpoints include **Event-Free Survival (EFS)** for the overarching objective, **Minimal Residual Disease (MRD)** of less than 0.1% leukemic cells in the bone marrow (BM) before the start of induction course 2, and **Disease-Free Survival (DFS)** for the consolidation randomization. These endpoints will be measured using flow cytometry to evaluate leukemic cell levels in the bone marrow.

Secondary endpoints will include bone marrow blast counts by morphology and multi-color flow cytometry (MFCM) after courses #1 and #2 and before allogeneic stem cell transplantation (allo-SCT), overall response rate (ORR) including complete remission (CR), complete remission with incomplete platelet recovery (CRp), and complete remission with incomplete hematologic recovery (CRi), as well as morphologic leukemia-free state (MLFS) rates. Additionally, MRD negativity and absolute MRD levels after courses #1 and #2 and before allo-SCT will be assessed. Other secondary endpoints include overall survival (OS), DFS, cumulative incidence of relapse (CIR), and cumulative toxicity, which will be defined as the total of all grades of adverse events (AEs) over time, graded by the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) version 5.0.

The efficacy parameters will be collected and analyzed at specified timepoints throughout the trial, including after each treatment course and before allo-SCT. The use of validated scales and laboratory tests, such as flow cytometry, will ensure the accuracy and reliability of the data collected. The trial aims to improve the overall EFS for children and adolescents with newly diagnosed acute myeloid leukemia (AML) and to assess the efficacy of adding gemtuzumab ozogamicin (GO) to the first induction course in CD33-positive AML patients.