Novel and innovative approaches for treatment of β-thalassemia

Safety and Efficacy of Thalidomide and Hydroxyurea Combination in Beta Thalassemia Patients

Beta thalassemia results from imbalance in alpha and beta globin chains causing severe anemia, transfusion dependency, and iron overload. Hematopoietic stem cell transplantation (HSCT) is the only curative treatment. Patients without the option of HSCT may benefit from Hemoglobin F (HbF) inducing agents like thalidomide and hydroxyurea (HU). We conducted a retrospective analysis on 87 beta thalassemia patients who received a combination of low dose thalidomide and HU from January 2017 to December 2020. Patients received combination of HU 500 mg everyday (> 30 kg) or every alternate day (< 30 kg) and thalidomide 100 mg (> 30 kg) or 50 mg (< 30 kg) once daily. Parameters such as transfusion requirement, anthropometry, Hb levels, ferritin, drug side effects etc. were monitored and evaluated at the end of one year of therapy. Sixty-three patients (72%) achieved transfusion independence and were eligible for the study. Median time to transfusion independence was 6 months (range 3-11 months). At the end of 1 year, overall response rate was 72%. There was significant improvement in the Hb levels, ferritin values and height at the end of 1 year of follow up. No grade 3 or 4 toxicities were noted. We document improvement of Hb levels, transfusion independence, reduction in iron overload, and improvement in growth parameters with minimal side effects at the end of 1 year of follow up.

MicroRNAs in β-thalassemia

β-thalassemia is a lethal inherited disease resulting from β-globin gene mutations. Severe β-thalassemia requires regular blood transfusions. Other active interventions, including iron chelating, stem cell transplantation and gene therapy, have remarkably improved the quality of life and prolonged the survival of patients with transfusion-dependent β-thalassemia, but all with significant limitations and complications. MicroRNAs (miRNAs), encoded by a class of endogenous genes, are found to play important roles in regulating globin expression. Among the miRNAs of particular interest related to β-thalassemia, miR-15a/16-1, miR-486-3p, miR-26b, miR-199b-5p, miR-210, miR-34a, miR-138, miR-326, let-7, and miR-17/92 cluster elevate γ-globin expression, while miR-96, miR-146a, miR-223-3p, and miR-144 inhibit γ-globin expression. A couple of miRNAs, miR-144 and miR-150, repress α-globin expression, whereas miR-451 induces α-, β- and γ-globin expression. Single nucleotide polymorphism in miRNA genes or their targeted genes might also contribute to the abnormal expression of hemoglobin. Moreover, changes in the expression of miR-125b, miR-210, miR-451, and miR-609 reflect the severity of anemia and hemolysis in β-thalassemia patients. These results suggest that miRNAs are potential biomarkers for the diagnosis and prognosis of β-thalassemia, and miRNA-based therapeutic strategy might be used as a coordinated approach for effectively treating β-thalassemia.

Recent Progress in Gene Therapy and Other Targeted Therapeutic Approaches for Beta Thalassemia

Beta-thalassemia is a genetic disorder characterized by the impaired synthesis of the betaglobin chain of adult hemoglobin. The disorder has a complex pathophysiology that affects multiple organ systems. The main complications of beta thalassemia are ineffective erythropoiesis, chronic hemolytic anemia and hemosiderosis-induced organ dysfunction. Regular blood transfusions are the main therapy for beta thalassemia major; however, this treatment can cause cardiac and hepatic hemosiderosis - the most common cause of death in these patients. This review focuses on unique future therapeutic interventions for thalassemia that reverse splenomegaly, reduce transfusion frequency, decrease iron toxicity in organs, and correct chronic anemia. The targeted effective protocols include hemoglobin fetal inducers, ineffective erythropoiesis correctors, antioxidants, vitamins, and natural products. Resveratrol is a new herbal therapeutic approach which serves as fetal Hb inducer in beta thalassemia. Hematopoietic stem cell transplantation (HSCT) is the only curative therapy for beta thalassemia major and is preferred over iron chelation and blood transfusion for ensuring long life in these patients. Meanwhile, several molecular therapies, such as ActRIIB/IgG1 Fc recombinant protein, have emerged to address complications of beta thalassemia or the adverse effects of current drugs. Regarding gene correction strategies, a phase III trial called HGB-207 (Northstar-2; NCT02906202) is evaluating the efficacy and safety of autologous cell transplantation with LentiGlobin. Advanced gene-editing approaches aim to cut DNA at a targeted site and convert HbF to HbA during infancy, such as the suppression of BCL11A (B cell lymphoma 11A), HPFH (hereditary persistence of fetal hemoglobin) and zinc-finger nucleases. Gene therapy is progressing rapidly, with multiple clinical trials being conducted in many countries and the promise of commercial products to be available in the near future.