Bone marrow Tfr2 deletion improves the therapeutic efficacy of the activin-receptor ligand trap RAP-536 in β-thalassemic mice

Beta Thalassemia in Children: Established Approaches, Old Issues, New Non-Curative Therapies, and Perspectives on Healing

Despite a decrease in prevalence and incidence rates, beta thalassemia continues to represent a significant public health challenge worldwide. In high-resource settings, children with thalassemia have an open prognosis, with a high chance of reaching adulthood and old age with a good quality of life. This is achievable if transfusion therapy is properly managed, effectively mitigating ineffective erythropoiesis and its associated complications while also minimizing excessive iron accumulation. Adequate iron chelation is essential to maintain reactive forms of iron within the normal range throughout life, thus preventing organ damage caused by hemosiderosis, which inevitably results from a regular transfusion regimen. New therapies, both curative, such as gene therapy, and non-curative, such as modulators of erythropoiesis, are becoming available for patients with transfusion-dependent beta thalassemia. Two curative approaches based on gene therapy have been investigated in both adults and children with thalassemia. The first approach uses a lentivirus to correct the genetic defect, delivering a functional gene copy to the patient's cells. The second approach employs CRISPR/Cas9 gene editing to directly modify the defective gene at the molecular level. No non-curative therapies have received approval for pediatric use. Among adults, the only available drug is luspatercept, which is currently undergoing clinical trials in pediatric populations. However, in many countries around the world, the new therapeutic options remain a mirage, and even transfusion therapy itself is not guaranteed for most patients, while the choice of iron chelation therapy depends on drug availability and affordability.

Combination of a TGF-β ligand trap (RAP-GRL) and TMPRSS6-ASO is superior for correcting β-thalassemia

A recently approved drug that induces erythroid cell maturation (luspatercept) has been shown to improve anemia and reduce the need for blood transfusion in non-transfusion-dependent as well as transfusion-dependent β-thalassemia (BT) patients. Although these results were predominantly positive, not all the patients showed the expected increase in hemoglobin (Hb) levels or transfusion burden reduction. Additional studies indicated that administration of luspatercept in transfusion-dependent BT was associated with increased erythropoietic markers, decreased hepcidin levels, and increased liver iron content. Altogether, these studies suggest that luspatercept may necessitate additional drugs for improved erythroid and iron management. As luspatercept does not appear to directly affect iron metabolism, we hypothesized that TMPRSS6-ASO could improve iron parameters and iron overload when co-administered with luspatercept. We used an agent analogous to murine luspatercept (RAP-GRL) and another novel therapeutic, IONIS TMPRSS6-LRx (TMPRSS6-ASO), a hepcidin inducer, to treat non-transfusion-dependent BT-intermedia mice. Our study shows that RAP-GRL alone improved red blood cell (RBC) production, with no or limited effect on splenomegaly and iron parameters. In contrast, TMPRSS6-ASO improved RBC measurements, ameliorated splenomegaly, and improved iron overload most effectively. Our results provide pre-clinical support for combining TMPRSS6-ASO and luspatercept in treating BT, as these drugs together show potential for simultaneously improving both erythroid and iron parameters in BT patients.