A Pilot Multicentric Prospective Study on the Usefulness of Peripheral Blood Immunophenotyping As Erythroid Maturation Response Marker during Luspatercept Treatment in Patients Affected By ß-Thalassemia Major and SF3B1+ Myelodysplastic Syndrome
Authors: Pilo Federica , Origa Raffaella , Greco Marianna , Caocci Giovanni , Lazzaro Giuseppe , Zaccheddu Eleonora , Zappu Antonietta , Mereu Angela , Pettinau Martina , Moi Marta , La Nasa Giorgio 
Published: December 2023

Introduction
Erythropoiesis is a multi-step maturation process; luspatercept proved to be successful on ineffective erythropoiesis acting on the second phase of erythroid maturation reducing the hyper expression of transforming growth factor beta (TGF-beta) ligands via the Smad 2/3 signaling pathway, thus ameliorating the aberrant late stage erythroid maturation featured in the myelodysplastic syndrome (MDS) and thalassemia. MEDALIST and BELIVE studies showed efficacy and safety of Luspatercept in MDS and Thalassemic patients respectively, but, regarding erythroid maturation, a significant correlation has been revealed only between hematological response and the reticulocyte value or medullar erythroblasts counts. In order to avoid for patients extra scheduled bone marrow aspirate , in particular in thalassemic patients, in our pilot study we propose to explore, for the first time, the role of peripheral blood immunophenotyping (IF) as reproducible and more affordable erythroid maturation's marker respect to the medullar immunophenotyping described in the previous published papers. Our hypothesis is that peripheral IF could represent a new tool to detect the ameliorate of inefficacy erythropoiesis during Luspatercept therapy, acting as “minimal residual disease” in patients in response or that loss the response to Luspatercept.
Patients, Material and Methods
Approval by local Ethic Scientific Commission has be completed. Patients will be enrolling by Hematology Unit and by Hemoglobinophaties Unit from 2 different Institution in Italy (“A. Businco” Oncologic Hospital and “A. Cao” Hemoglobinopathies Hospital). Inclusion criteria: Patients must be affected by MDS with ringed sideroblasts (with or without SF3B1 mutation) very low, low and intermediate revised IPSS stage or affected by ß-thalassemia major; aged ≥ 18 years and able to understand and sign an informant consent; not renal or hepatic failure; EF &gt; 50%. Duration of the study will be scheduled for 1 year. Prevision of 30 patient enrolled in the first 1 year of study. Primary endpoint is to confirm the role of peripheral blood immunophenotyping (IF) as reproducible and affordable erythroid maturation's marker in these setting of patients. Secondary endpoint is to evaluate the role of peripheral IF as “minimal residual disease” in particular during the loss of Lusplatercept response and also the assessments of iron homeostasis in responder's patients. Patients will be assessed for r-IPSS and NGS (only for MDS), endogenous erythropoietin, full blood count and reticulocyte, iron status, transfusion burden in the previous 24 weeks and peripheral IF (centralized in the laboratory of Hematology Unit). All patients will collect these samples at baseline timing and after 12,24,36 and 48 weeks. Peripheral IF is tested by 8-color EuroFlow antibody panels define progressive terminal stages of erythroblasts' maturation (10 health samples have been used as control). Hematological response and Luspatercept's dose escalation are considered as for MEDALIST study criteria for MDS and BELIVE study for thalassemia, as well adverse events.
Results
At the time of this report 26 patients have been enrolled in the two institution (10 MDS and 16 thalassemic patients). Baseline patients' characteristics are reported in TAB 1 and baseline peripheral blood erythroid maturation (based on centralized IF) are reported in TAB 2
Conclusion
Our pilot study aims to explore, for the first time, the role of peripheral blood immunophenotyping (IF) as reproducible and affordable erythroid maturation's marker during Luspatercept therapy in Thalassemic and MDS patients.