Evaluation of Cumulative Fludarabine Exposure in Hematological Malignancy Patients Undergoing Reduced Intensity Allogeneic Stem Cell Transplantation

The primary objective of this study is to evaluate the **cumulative exposure** and interpatient variability in cumulative exposure to F-Ara-A in patients receiving reduced intensity conditioning (RIC) with standard dose **Fludarabine** based on body surface area (BSA). This is clinically relevant as understanding the variability in drug exposure can inform dosing strategies to optimize therapeutic outcomes and minimize toxicity in patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) for hematological malignancies.

Secondary objectives include:

• Assessing the impact of patient covariates on cumulative exposure to Fludarabine.
• Evaluating the impact of F-Ara-A exposure on long-term patient outcomes.
• Investigating the impact of F-Ara-A exposure on neurological toxicity.
• Validating a previously published pharmacokinetic model of F-Ara-A, developed in a myeloablative conditioning (MAC) setting, in the RIC setting.

The clinical trial involves **patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT)** for hematological malignancy following reduced intensity conditioning (RIC) with Fludarabine, Melphalan, and ATG. The study population includes both male and female participants aged 18 years and older. Participants are required to have a hematological malignancy and must be capable of understanding and signing an informed consent. The trial does not involve a vulnerable population. Participants are expected to adhere to specific lifestyle considerations, including the use of highly effective birth control methods during and after the study, consistent with local regulations. The trial population was selected based on specific inclusion criteria, such as the use of Tacrolimus or Ciclosporin and Mycophenolate Mofetil (MMF) for graft versus host disease (GvHD) prevention, and having a human leukocyte antigen (HLA) identical sibling donor, 10/10 HLA matched unrelated donor, or 9/10 mismatched unrelated donor. The sponsor has not provided information regarding the total number of participants in the study.

The clinical trial is designed to evaluate the **cumulative exposure** and interpatient variability in exposure to F-Ara-A in patients receiving reduced intensity conditioning (RIC) with standard dose **Fludarabine** based on body surface area (BSA). This trial is a **randomized, double-blind, controlled** study, with an estimated duration extending until July 2029. The trial will commence recruitment in July 2024 and will involve patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) for hematological malignancy, following RIC with Fludarabine, Melphalan, and anti-thymocyte globulin (ATG).

Participants will undergo a series of study visits, beginning with an inclusion (screening) visit to assess eligibility based on criteria such as age (≥ 18 years), ability to provide informed consent, and specific medical conditions. The inclusion criteria also require the use of Tacrolimus or Ciclosporin and Mycophenolate Mofetil (MMF) for graft versus host disease (GvHD) prevention, and a human leukocyte antigen (HLA) identical sibling donor, 10/10 HLA matched unrelated donor, or 9/10 mismatched unrelated donor. The primary endpoint is the area under the curve (AUC) of F-Ara-A after exposure to Fludarabine, assessed after the last patient has completed the conditioning regimen.

Follow-up visits will be conducted to monitor the association between F-Ara-A AUC and factors such as creatinine clearance, bodyweight/BMI, and its influence on non-relapse mortality, relapse rate, progression-free survival, and overall survival. These assessments will occur when the first 25 included patients and all included patients have reached 1, 2, and 3 years of follow-up post-transplant. The end-of-study visit will conclude the participant's involvement, with the expected length of participation varying based on individual response and study progression.

Participants may be subject to early termination from the study if they fail to adhere to the protocol, experience adverse events that compromise safety, or withdraw consent. The trial is categorized as a Phase IV trial, with all medicinal products having marketing authorization in the concerned Member State and used in accordance with the terms of the authorization. The study involves minimal additional risk or burden, with only extra blood draws being required.

The clinical trial involves the administration of several experimental medications, each with specific pharmaceutical forms, dosages, and administration routes. **Melphalan**, marketed as ALKERAN 50 mg, is provided as a powder and solvent for solution for infusion. It is administered intravenously with a maximum daily dose of 140 mg/m² and a total dose of 140 mg/m² over a treatment period of one day. The active substance is of chemical origin, and the product is manufactured by Aspen Pharma Trading Limited.

**Fludarabine Phosphate** is used in two formulations: Fludarabine Sandoz 25 mg/ml and Fludarabine Teva 25 mg/ml, both as concentrates for solution for injection or infusion. These are administered intravenously with a maximum daily dose of 30 mg/m² and a total dose of 150 mg/m² over a five-day treatment period. Both products are of chemical origin, with Sandoz N.V. and Teva Pharma Belgium N.V./S.A. as the respective manufacturers.

**Anti-T Lymphocyte Immunoglobulin for Human Use, Rabbit**, marketed as Grafalon 20 mg/ml, is provided as a concentrate for solution for infusion. It is administered intravenously with a maximum daily dose of 2.5 mg/m² and a total dose of 5 mg/m² over a two-day treatment period. This product is derived from structurally diverse substances, specifically blood-derived, and is manufactured by Neovii Biotech GmbH.

**Rabbit Anti-Human Thymocyte Immunoglobulin**, marketed as THYMOGLOBULINE 5 mg/ml, is provided as a powder for solution for infusion. It is administered intravenously with a maximum daily dose of 2.5 mg/kg and a total dose of 5 mg/kg over a two-day treatment period. This product is also derived from structurally diverse substances, specifically blood-derived, and is manufactured by Genzyme Europe B.V.

Throughout the trial, participant compliance with the dosing schedules is monitored to ensure adherence to the treatment protocols. The trial does not include any non-experimental treatments such as standard-of-care therapy, placebo, or comparator treatments. The focus is on evaluating the cumulative exposure and interpatient variability in exposure to these medications, particularly in the context of reduced intensity conditioning with standard dose Fludarabine based on body surface area.

Efficacy in this clinical trial will be assessed primarily through the measurement of the **Area under the curve (AUC)** of F-Ara-A following exposure to Fludarabine in the context of reduced intensity conditioning with Fludarabine, Melphalan, and anti-thymocyte globulin (ATG). This primary endpoint will be evaluated after the last included patient has completed the conditioning regimen. Secondary endpoints include the association between F-Ara-A AUC and creatinine clearance, bodyweight/BMI, and its influence on non-relapse mortality, relapse rate, progression-free survival, and overall survival. These secondary endpoints will be assessed at various timepoints, specifically when the first 25 included patients and all included patients have reached 1 year, 2 years, and 3 years of follow-up post-transplant.

Additional secondary endpoints involve the influence of F-Ara-A AUC on median time to neutrophil and platelet engraftment, peripheral CD4 and CD8 T-cell count, and the incidence of central nervous system complications/events in the first year after allogeneic stem cell transplant. The applicability of a pharmacokinetic model published by Langenhorst et al. to predict F-Ara-A AUC in the study population will also be evaluated. These assessments will be conducted using data collected at specified follow-up intervals, ensuring a comprehensive analysis of the efficacy parameters.