Phase 2 Evaluation of Varnimcabtagene Autoleucel in Pediatric CD19+ Acute Lymphoblastic Leukemia Resistant or Refractory to Standard Therapies

The primary objective of this Phase 2 study is to evaluate the **efficacy** (response rate) of ARI-0001 cells in pediatric patients with CD19+ **acute lymphoblastic leukemia** that is resistant or refractory to therapy. This is clinically relevant as it addresses the need for effective treatment options in a population with limited therapeutic alternatives, potentially improving outcomes in this challenging clinical scenario.

Secondary objectives include:

• Evaluating the **safety** and tolerability of ARI-0001 therapy, which is crucial for understanding the risk-benefit profile of the treatment.
• Further evaluating efficacy by assessing the duration of response and survival metrics, including event-free, relapse-free, and overall survival, following ARI-0001 cell infusion. This provides a comprehensive view of the treatment's long-term benefits.
• Assessing the kinetics of ARI-0001 cells in peripheral blood, bone marrow, and cerebrospinal fluid post-administration, which is important for understanding the distribution and persistence of the therapy.
• Evaluating functional CART-cell persistence by assessing B-cell aplasia in peripheral blood, which is indicative of the treatment's sustained activity and potential for long-term disease control.

The clinical trial involves a study population of **paediatric patients** aged 0 to 18 years diagnosed with **acute lymphoblastic leukemia** (ALL) that is resistant or refractory to therapy. The trial includes both male and female participants, and the population is considered vulnerable due to the age range and health condition. The sponsor has not provided the total number of participants. Participants were selected based on specific inclusion criteria, such as having a diagnosis of relapsed or refractory CD19+ ALL, with disease burden defined by morphologic relapse in bone marrow or presence of leukemic blasts in an extramedullary site. The trial does not exclude subjects with isolated extramedullary involvement, Down syndrome, or CNS3 involvement if the disease is stable. Additionally, patients with Ph+ ALL who are intolerant or have failed at least one TKI are included, provided the blasts remain CD19+ at inclusion. Participants must have a performance status of Lansky or Karnofsky ≥ 50%, a life expectancy of more than three months, and adequate venous access with no contraindications for lymphoapheresis. The trial requires the signature of informed consent from the patient and/or legal guardian.

The clinical trial is designed to evaluate the efficacy of **varnimcabtagene autoleucel** in pediatric patients with CD19+ **acute lymphoblastic leukemia** that is resistant or refractory to therapy. This is a Phase II, randomized, double-blind, controlled trial. The trial is expected to last until March 23, 2027, with recruitment starting on March 23, 2023. Participants will be involved in the study for a maximum treatment period of up to 2 months, depending on their response and condition.

The trial will include several study visits, beginning with an inclusion (screening) visit to assess eligibility based on criteria such as age (0 to 18 years), diagnosis of relapsed/refractory CD19+ ALL, and performance status. Following the screening, participants will undergo lymphoapheresis for the collection of T-cells, which will be expanded and transduced with a lentivirus to express a chimeric antigen receptor. The primary endpoint is the complete response rate within 100 days post-infusion, evaluated through multiparameter flow cytometry.

Follow-up visits will occur weekly for the first month, monthly for the first 6 months, and then at 12 months to monitor the in vivo survival of ARI-0001 cells and B-cell aplasia. Secondary endpoints include event-free survival, duration of remission, and overall survival at 12 months. The end-of-study visit will assess long-term outcomes and any adverse events, with a focus on toxicity and procedure-related mortality.

Participants may be terminated early from the study if they experience significant adverse events, fail to comply with the study protocol, or if the principal investigator determines that continued participation is not in the participant's best interest. The trial aims to provide comprehensive data on the safety and efficacy of the investigational product in this patient population.

The clinical trial involves the administration of several **experimental medications** and auxiliary treatments. **Varnimcabtagene autoleucel** is the primary investigational product, administered as a dispersion for infusion. It is a cell therapy product, specifically a lentivirus-transduced autologous T-cell therapy, designed to express a chimeric antigen receptor targeting CD19. The maximum daily dose is 2 units, with a total dose not exceeding 3 units over a treatment period of up to 2 weeks. The route of administration is intravenous.

**Allopurinol** is used as an auxiliary treatment in the form of tablets. It acts as a uric acid inhibitor and is administered orally. The maximum daily dose is 300 mg/m², with a total dose limit of 2100 mg/m² over a 1-week period.

**Human Immunoglobulin G** is provided as a solution for injection, administered intravenously. It is used to support immune function, with a maximum daily and total dose of 500 mg/kg over a 1-day period.

**Cytarabine** is a chemotherapy agent administered as a solution for injection or infusion. The maximum daily dose is 500 mg/m², with a total dose of 1000 mg/m² over a 2-day period, delivered via intravenous infusion.

**Dexchlorpheniramine maleate** is an antihistamine provided in syrup form, administered both orally and intravenously. The maximum daily dose is 0.15 mg/kg, with a total dose of 0.45 mg/kg over a 3-day period.

**Fludarabine** is another chemotherapy agent, administered as a concentrate for solution for infusion. The maximum daily dose is 30 mg/m², with a total dose of 90 mg/m² over a 3-day period, delivered intravenously.

**Methylprednisolone** is a corticoid provided as a solution for injection, administered intravenously. The maximum daily dose is 2 mg/kg, with a total dose of 6 mg/kg over a 3-day period.

**Tocilizumab** is administered as a solution for infusion, used to manage inflammatory responses. The maximum daily and total dose is 2400 mg, delivered intravenously over a 1-day period.

**Paracetamol** is used as an analgesic in syrup form, administered both orally and intravenously. The maximum daily dose is 1 g, with a total dose of 3 g over a 1-day period.

**Cyclophosphamide** is a chemotherapy agent provided as a solution for injection or infusion. The maximum daily dose is 300 mg/m², with a total dose of 900 mg/m² over a 3-day period, delivered via intravenous infusion.

**Etoposide** is another chemotherapy agent, administered as a solution for infusion. The maximum daily dose is 150 mg/m², with a total dose of 450 mg/m² over a 3-day period, delivered via intravenous infusion.

The efficacy of the investigational product, ARI-0001 cells, in the clinical trial will be assessed primarily through the **complete response rate**. This includes the complete remission (CR) rate and CR rate with incomplete hematological recovery (CRi), with undetectable measurable residual disease determined by multiparameter flow cytometry within 100 days post-infusion. For patients with isolated extramedullary disease, response evaluation will be conducted using morphology and flow cytometry of cerebrospinal fluid (CSF) and/or imaging tests such as PET-CT or MRI.

Secondary endpoints for efficacy include event-free survival (EFS) at 12 months, duration of remission from CR or CRi to relapse or death due to acute lymphoblastic leukemia (ALL), relapse-free survival (RFS) at 12 months, overall survival at 12 months, and transplant and disease-free survival at 6 and 12 months. Additionally, the in vivo survival of ARI-0001 cells in peripheral blood will be monitored using flow cytometry and qPCR of the transgene weekly for the first month, monthly for the first 6 months, and then at 12 months. B-cell aplasia will be measured by flow cytometry weekly for the first month, monthly for the first 6 months, every 3 months from month 6 to month 12, and every 6 months until the end of the study.

Toxicity will also be evaluated as part of the efficacy assessment, defined by adverse events of grade ≥3 according to common toxicity criteria (version 5.0). Specific adverse events of interest include cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), and cerebral edema, graded according to the ASTCT classification. Procedure-related mortality will also be measured.