Selecting b-thalassemia patients for gene therapy: a decision-making algorithm

The Società Italiana Talassemie ed Emoglobinopatie (Italian Society of Thalassemias and Hemoglobinopathies, SITE) has developed this document based on multidisciplinary discussions of a panel of experts to provide guidance on the identification and selection of patients with transfusion-dependent beta-thalassemia (β-TDT) who could benefit from gene therapy. Currently, allogeneic transplantation of hematopoietic stem cells is the only curative and most widely used therapy treatment for β-TDT. However, recent trials of gene therapy have reported very promising results in terms of overall survival and thalassemia-free survival and are opening a new landscape of treatment. This algorithm for the selection of patients suitable for gene therapy and the supporting notes were formulated by consensus review after an evaluation of currently available scientific evidence using validated criteria. The evidence was interpreted with caution because clinical trial experience of gene therapy is currently limited, a conventional treatment is available for patients with β-TDT and the availability of gene therapy will, at least initially, be quite limited. Clinical experience of allogeneic transplantation in β-TDT, which began in 1981, immediately showed the importance of patient risk stratification in order to achieve the best results (see the Pesaro experience and their classification of patients according to risk). Published data in the literature and the recent analysis of clinical evidence by the European Registry of Hemoglobinopathies of a large number of patients (2011 and 2018 analyses) confirm that young patient age (<14 years) and the availability of a human leukocyte antigen (HLA)-identical family donor are factors that offer the best outcome from allogeneic transplantation. Current knowledge of, and experience with, non-conventional treatments, such as allogeneic transplantation and gene therapy, are discussed in order to identify the best available treatment and indication for these patients according to their characteristics. At this point in time, when we can see the emergence of ‘the age of gene therapy’, it is essential to establish the optimal patient setting in which gene therapy can be applied, or better, to define the setting that represents the most suitable indication for gene therapy, identify the patients who should have clinical priority for access to the procedure, and set out requirements and recommendations for the identification of qualified treatment centers for gene therapy. When considering changes to the treatment of patients with β-TDT, including gene therapy, it is essential that a detailed consultation is held with the patient and their caregiver/family to discuss all possible risks and potential benefits from the treatment. Discussion of this aspect of care is outside of the scope of this document but remains an important element of patient care.