Expression of γ-globin genes in β-thalassemia patients treated with sirolimus: results from a pilot clinical trial (Sirthalaclin)

Reframing thalassaemia syndrome as a benign haematopoietic stem cell disorder

Thalassaemia, caused by over 250 mutations in the beta globin gene, changes the haematopoietic stem cell (HSC) differentiation, leading to ineffective erythropoiesis. This Wider Perspective article overlooks its underlying nature as a benign HSC disorder with a significant impact on the erythroid cell lineage. The simplicity of managing symptoms through transfusions and iron chelation therapy has shifted the focus away from the development of cell-based treatments. The identification of the beta039 mutation by Chang and Kan in 1979 marked a turning point, suggesting as main approach the molecular level by correcting the beta globin chain imbalances through gene insertion and editing. However, challenges of technology have delayed the implementation of these strategies for over four decades. In contrast, the past two decades have witnessed significant advances in the treatment of HSC disorders of the myeloid clone which are driven by a 'target cell strategy'. Many current and innovative treatments for thalassaemia are now adopting this approach, highlighting the importance of identifying suitable candidates through risk stratification. This manuscript explores the evolving understanding of thalassaemia syndromes as congenital HSC disorders of the erythroid clone and examines the implications of this perspective for the development of future treatments.

Exploring the functional and immune landscape of E-β thalassemia patients through RNA sequencing of peripheral blood mononuclear cells

Thalassemia is a hematological disorder caused by mutations in the hemoglobin gene, often necessitating regular blood transfusions. These frequent transfusions exert continuous pressure on patients' immune systems. Despite extensive research on the hematological aspects of thalassemia, few studies have explored the immune status of these patients. In this study, we investigated the immune profiles of thalassemia patients using peripheral blood mononuclear cells (PBMCs). We examined the transcriptomes of PBMCs from five severe thalassemia patients, five non-severe patients, and five healthy volunteers. After isolating PBMCs, we extracted total RNA and performed RNA sequencing using the NOVASEQ 6000 platform. We analyzed the raw counts to observe differential gene expression between thalassemia patients and healthy controls, as well as between severe and non-severe patients. Additionally, we conducted gene set enrichment analysis (GSEA) to explore underlying immune conditions. The gene expression profile, along with GSEA, revealed a marked decrease in MHC-II-mediated antigen presentation. Notably, we identified, for the first time, the activation of reactive oxygen species (ROS) through NK cell-mediated eosinophil chemotaxis, suggesting a link to disease severity. Severe thalassemia patients also exhibited higher expression of pro-inflammatory cytokines. Furthermore, transcriptome analysis showed increased expression of the ABO gene in severe thalassemia patients, which may contribute to heightened immune reactions and an increased need for blood transfusions. Deconvolution of the RNA-seq data revealed lower abundances of CD4 T cells and monocytes in thalassemia patients. Thus, immune-modulating drugs could be explored as alternative therapeutic options for the management of thalassemia.

A β-Thalassemia Cell Biobank: Updates, Further Validation in Genetic and Therapeutic Research and Opportunities During (and After) the COVID-19 Pandemic

Background: Cellular biobanks are of great interest for performing studies finalized in the development of personalized approaches for genetic diseases, including β-thalassemia and sickle cell disease (SCD), important diseases affecting the hematopoietic system. These inherited genetic diseases are characterized by a global distribution and the need for intensive health care. The aim of this report is to present an update on the composition of a cellular Thal-Biobank, to describe its utilization since 2016, to present data on its application in studies on fetal hemoglobin induction and on gene editing, and to discuss its employment as a "unique tool" during and after the COVID-19 pandemic. Methods: The methods were as follows: freezing, cryopreservation, long-term storage, and thawing of erythroid precursor cells from β-thalassemia patients; fetal hemoglobin (HbF) induction; CRISPR-Cas9 gene editing; HPLC analysis of the hemoglobin pattern. Results: The updated version of the Thal-Biobank is a cellular repository constituted of 990 cryovials from 221 β-thalassemia patients; the phenotype (pattern of hemoglobin production) is maintained after long-term storage; fetal hemoglobin induction and CRISPR-Cas9 gene editing can be performed using biobanked cells. In representative experiments using an isoxazole derivative as HbF inducer, the HbF increased from 13.36% to more than 60%. Furthermore, in CRIPR/Cas9 gene editing, de novo production of HbA was obtained (42.7% with respect to the trace amounts found in untreated cells). Conclusions: The implemented Thal-Biobank was developed before the COVID-19 outbreak and should be considered a tool of great interest for researchers working on β-thalassemia, with the aim of developing innovative therapeutic protocols and verifying the impact of the COVID-19 pandemic on erythroid precursor cells.

AZD8055 Is More Effective Than Rapamycin in Inhibiting Proliferation and Promoting Mitochondrial Clearance in Erythroid Differentiation

Background: As an important downstream effector of various signaling pathways, mTOR plays critical roles in regulating many physiological processes including erythropoiesis. It is composed of two distinct complexes, mTORC1 and mTORC2, which differ in their components and downstream signaling effects. Our previous study revealed that the inhibition of mTORC1 by rapamycin significantly repressed the erythroid progenitor expansion in the early stage but promoted enucleation and mitochondria clearance in the late stage of erythroid differentiation. However, the particular roles and differences of mTORC1 and mTORC2 in the regulation of erythropoiesis still remain largely unknown. In the present study, we investigated the comparative effects of dual mTORC1/mTORC2 mTOR kinase inhibitor AZD8055 and mTORC1 inhibitor rapamycin on erythroid differentiation in K562 cells induced by hemin and erythropoiesis in β-thalassemia mouse model. Materials and Methods: In vitro erythroid differentiation model of hemin-induced K562 cells and β-thalassemia mouse model were treated with AZD8055 and rapamycin. Cell Counting Kit-8 was used to detect cell viability. The cell proliferation, cell cycle, erythroid surface marker expression, mitochondrial content, and membrane potential were determined and analyzed by flow cytometry and laser scanning confocal microscopy. Globin gene expression during erythroid differentiation was measured by RT-qPCR. The mTORC2/mTORC1 and autophagy pathway was evaluated using western blotting. Results: Both AZD8055 and rapamycin treatments increased the expression levels of the erythroid differentiation-specific markers, CD235a, α-globin, γ-globin, and ε-globin. Notably, AZD8055 suppressed the cell proliferation and promoted the mitochondrial clearance of hemin-induced K562 cells more effectively than rapamycin. In a mouse model of β-thalassemia, both rapamycin and AZD8055 remarkably improve erythroid cell maturation and anemia. Moreover, AZD8055 and rapamycin treatment inhibited the mTORC1 pathway and enhanced autophagy, whereas AZD8055 enhanced autophagy more effectively than rapamycin. Indeed, AZD8055 treatment inhibited both mTORC2 and mTORC1 pathway in hemin-induced K562 cells. Conclusion: AZD8055 is more effective than rapamycin in inhibiting proliferation and promoting mitochondrial clearance in erythroid differentiation, which might provide us one more therapeutic option other than rapamycin for ineffective erythropoiesis treatment in the future. These findings also provide some preliminary information indicating the roles of mTORC1 and mTORC2 in erythropoiesis, and further studies are necessary to dissect the underlying mechanisms.

Activating transcription factor 4 in erythroid development and β -thalassemia: a powerful regulator with therapeutic potential

Activating transcription factor 4 (ATF4) is a fundamental basic region/leucine zipper transcription factor, responds to various stress signals, and plays crucial roles in normal metabolic and stress response processes. Although its functions in human health and disease are not completely understood, compelling evidence underscores ATF4 is indispensable for multiple stages and lineages of erythroid development, including the regulation of fetal liver hematopoietic stem cells, induction of terminal erythroid differentiation, and maintenance of erythroid homeostasis. β -Thalassemia is a blood disorder arising from mutations in the β -globin gene. Reactivating the expression of the γ -globin gene in adult patients has emerged as a promising therapeutic strategy for ameliorating clinical symptoms associated with β -thalassemia. Recent research has suggested that ATF4 contributes to decreased fetal hemoglobin (HbF) level through its binding to potent negative regulators of HbF, such as BCL11A and MYB. Notably, evidence also suggests a contrasting outcome where increased ATF4 protein levels are associated with enhanced HbF at the transcriptional level. Consequently, the identification of mechanisms that modulate ATF4-mediated γ -globin transcription and its effects on erythroid development may unveil novel targets for β -thalassemia treatment.

Alpha globin gene alterations modifying the phenotype of homozygous beta thalassaemia

The phenotype of β-thalassemia varies widely. The primary determinant is the type of beta-globin gene mutation; however, there are secondary and tertiary modifiers also as associated alpha mutations, polymorphisms, as well as coinheritance of mutations affecting other related systems. Co-inheritance of alpha thalassemia mutations is known to ameliorate the severity of HbE-β thalassemia. However, the role of alpha globin gene alterations (deletions and triplication) is not well illustrated in homozygous β-thalassemia. Here we evaluated the role of alpha globin gene alterations in 122 β-thalassemia patients having IVS1-5 (G > C) homozygous mutation. β-thalassemia mutations were detected by ARMS PCR and alpha mutations by GAP-PCR. Gene expression by qRT-PCR. Out of 122 cases, 15 patients had alpha 3.7 triplications (ααα3.7anti), 24 had alpha 3.7 kb deletion (-α3.7) mutation and three patients had 4.2 kb deletion (-α4.2). Patients were divided into two groups, requiring less than 8 units (NTDT) and more than 8 units (TDT) of blood transfusion per year (≥8U BT/year). The percentage of alpha deletion was significantly (p = 0.0042) high in NTDT (42.1%) as compared with TDT (13.2%). Conversely, the proportion of alpha triplication is high in the TDT as compared with NTDT. Even mean serum ferritin level was found to be significantly high in patients having alpha triplication as compared with those having alpha deletions (p = 0.0184) and normal alpha gene (p = 0.0003). α/β globin ratio was highest in TDT patients with alpha triplication and lowest in NTDT patients with alpha-del. The results show that concurrent inheritance of alpha gene alterations influences the phenotypic severity of homozygous β-thalassemia.

Therapeutic Relevance of Inducing Autophagy in β-Thalassemia

The β-thalassemias are inherited genetic disorders affecting the hematopoietic system. In β-thalassemias, more than 350 mutations of the adult β-globin gene cause the low or absent production of adult hemoglobin (HbA). A clinical parameter affecting the physiology of erythroid cells is the excess of free α-globin. Possible experimental strategies for a reduction in excess free α-globin chains in β-thalassemia are CRISPR-Cas9-based genome editing of the β-globin gene, forcing "de novo" HbA production and fetal hemoglobin (HbF) induction. In addition, a reduction in excess free α-globin chains in β-thalassemia can be achieved by induction of the autophagic process. This process is regulated by the Unc-51-like kinase 1 (Ulk1) gene. The interplay with the PI3K/Akt/TOR pathway, with the activity of the α-globin stabilizing protein (AHSP) and the involvement of microRNAs in autophagy and Ulk1 gene expression, is presented and discussed in the context of identifying novel biomarkers and potential therapeutic targets for β-thalassemia.

Increased Expression of α-Hemoglobin Stabilizing Protein (AHSP) mRNA in Erythroid Precursor Cells Isolated from β-Thalassemia Patients Treated with Sirolimus (Rapamycin)

Background/Objectives: in β-thalassemia, important clinical complications are caused by the presence of free α-globin chains in the erythroid cells of β-thalassemia patients. These free α-globin chains are present in excess as a result of the lack of β-globin chains to bind with; they tend to aggregate and precipitate, causing deleterious effects and overall cytotoxicity, maturation arrest of the erythroid cells and, ultimately, ineffective erythropoiesis. The chaperone protein α-hemoglobin-stabilizing protein (AHSP) reversibly binds with free α-globin; the resulting AHSP-αHb complex prevents aggregation and precipitation. Sirolimus (rapamycin) has been previously demonstrated to induce expression of fetal hemoglobin and decrease the excess of free α-globin chain in the erythroid cells of β-thalassemia patients. The objective of this study was to verify whether sirolimus is also able to upregulate AHSP expression in erythroid precursor cells (ErPCs) isolated from β-thalassemia patients. Methods: the expression of AHSP genes was analyzed by measuring the AHSP mRNA content by real-time quantitative PCR (RT-qPCR) and the AHSP protein production by Western blotting. Results: AHSP gene expression was found to be higher in ErPCs of β-thalassemia patients in comparison to ErPCs isolated from healthy subjects. In addition, AHSP expression was further induced by treatment of β-thalassemia ErPCs with sirolimus. Finally, AHSP mRNA was expressed at an increased level in ErPCs of sirolimus-treated β-thalassemia patients participating in the NCT03877809 Sirthalaclin clinical trial. Conclusions: this exploratory study suggests that AHSP expression should be considered as an endpoint in clinical trials based on sirolimus.

Pharmacogenomics of Drugs Used in β-Thalassemia and Sickle-Cell Disease: From Basic Research to Clinical Applications

In this short review we have presented and discussed studies on pharmacogenomics (also termed pharmacogenetics) of the drugs employed in the treatment of β-thalassemia or Sickle-cell disease (SCD). This field of investigation is relevant, since it is expected to help clinicians select the appropriate drug and the correct dosage for each patient. We first discussed the search for DNA polymorphisms associated with a high expression of γ-globin genes and identified this using GWAS studies and CRISPR-based gene editing approaches. We then presented validated DNA polymorphisms associated with a high HbF production (including, but not limited to the HBG2 XmnI polymorphism and those related to the BCL11A, MYB, KLF-1, and LYAR genes). The expression of microRNAs involved in the regulation of γ-globin genes was also presented in the context of pharmacomiRNomics. Then, the pharmacogenomics of validated fetal hemoglobin inducers (hydroxyurea, butyrate and butyrate analogues, thalidomide, and sirolimus), of iron chelators, and of analgesics in the pain management of SCD patients were considered. Finally, we discuss current clinical trials, as well as international research networks focusing on clinical issues related to pharmacogenomics in hematological diseases.

Impact of α-Globin Gene Expression and α-Globin Modifiers on the Phenotype of β-Thalassemia and Other Hemoglobinopathies: Implications for Patient Management

In this short review, we presented and discussed studies on the expression of globin genes in β-thalassemia, focusing on the impact of α-globin gene expression and α-globin modifiers on the phenotype and clinical severity of β-thalassemia. We first discussed the impact of the excess of free α-globin on the phenotype of β-thalassemia. We then reviewed studies focusing on the expression of α-globin-stabilizing protein (AHSP), as a potential strategy of counteracting the effects of the excess of free α-globin on erythroid cells. Alternative processes controlling α-globin excess were also considered, including the activation of autophagy by β-thalassemia erythroid cells. Altogether, the studies reviewed herein are expected to have a potential impact on the management of patients with β-thalassemia and other hemoglobinopathies for which reduction in α-globin excess is clinically beneficial.

Inhibitory effects of SARS-CoV-2 spike protein and BNT162b2 vaccine on erythropoietin-induced globin gene expression in erythroid precursor cells from patients with β-thalassemia

During the recent coronavirus disease 2019 (COVID-19) pandemic several patients with β-thalassemia have been infected by severe acute respiratory syndrome coronavirus (SARS-CoV-2), and most patients were vaccinated against SARS-CoV-2. Recent studies demonstrate an impact of SARS-CoV-2 infection on the hematopoietic system. The main objective of this study was to verify the effects of exposure of erythroid precursor cells (ErPCs) from patients with β-thalassemia to SARS-CoV-2 spike protein (S-protein) and the BNT162b2 vaccine. Erythropoietin (EPO)-cultured ErPCs have been either untreated or treated with S-protein or BNT162b2 vaccine. The employed ErPCs were from a β-thalassemia cellular Biobank developed before the COVID-19 pandemic. The genotypes were β+-IVSI-110/β+-IVSI-110 (one patient),  β039/β+-IVSI-110 (3 patients), and β039/ β039 (2 patients). After treatment with S-protein or BNT162b2 for 5 days, lysates were analyzed by high performance liquid chromatography (HPLC), for hemoglobin production, and isolated RNA was assayed by RT-qPCR, for detection of globin gene expression. The main conclusions of the results obtained are that SARS-CoV-2 S-protein and BNT162b2 vaccine (a) inhibit fetal hemoglobin (HbF) production by β-thalassemic ErPCs and (b) inhibit γ-globin mRNA accumulation. In addition, we have performed in silico studies suggesting a high affinity of S-protein to HbF. Remarkably, the binding interaction energy of fetal hemoglobin to S-protein was comparable with that of angiotensin-converting enzyme 2 (ACE2). Our results are consistent with the hypothesis of a relevant impact of SARS-CoV-2 infection and COVID-19 vaccination on the hematopoietic system.

New Synthetic Isoxazole Derivatives Acting as Potent Inducers of Fetal Hemoglobin in Erythroid Precursor Cells Isolated from β-Thalassemic Patients

Induction of fetal hemoglobin (HbF) is highly beneficial for patients carrying β-thalassemia, and novel HbF inducers are highly needed. Here, we describe a new class of promising HbF inducers characterized by an isoxazole chemical skeleton and obtained through modification of two natural molecules, geldanamycin and radicicol. After preliminary biological assays based on benzidine staining and RT-qPCR conducted on human erythroleukemic K562 cells, we employed erythroid precursors cells (ErPCs) isolated from β-thalassemic patients. ErPCs weretreated with appropriate concentrations of isoxazole derivatives. The accumulation of globin mRNAs was studied by RT-qPCR, and hemoglobin production by HPLC. We demonstrated the high efficacy of isozaxoles in inducing HbF. Most of these derivatives displayed an activity similar to that observed using known HbF inducers, such as hydroxyurea (HU) or rapamycin; some of the analyzed compounds were able to induce HbF with more efficiency than HU. All the compounds were active in reducing the excess of free α-globin in treated ErPCs. All the compounds displayed a lack of genotoxicity. These novel isoxazoles deserve further pre-clinical study aimed at verifying whether they are suitable for the development of therapeutic protocols for β-thalassemia.

Decrease in α-Globin and Increase in the Autophagy-Activating Kinase ULK1 mRNA in Erythroid Precursors from β-Thalassemia Patients Treated with Sirolimus

The β-thalassemias are hereditary monogenic diseases characterized by a low or absent production of adult hemoglobin and excess in the content of α-globin. This excess is cytotoxic for the erythroid cells and responsible for the β-thalassemia-associated ineffective erythropoiesis. Therefore, the decrease in excess α-globin is a relevant clinical effect for these patients and can be realized through the induction of fetal hemoglobin, autophagy, or both. The in vivo effects of sirolimus (rapamycin) and analogs on the induction of fetal hemoglobin (HbF) are of key importance for therapeutic protocols in a variety of hemoglobinopathies, including β-thalassemias. In this research communication, we report data showing that a decrease in autophagy-associated p62 protein, increased expression of ULK-1, and reduction in excess α-globin are occurring in erythroid precursors (ErPCs) stimulated in vitro with low dosages of sirolimus. In addition, increased ULK-1 mRNA content and a decrease in α-globin content were found in ErPCs isolated from β-thalassemia patients recruited for the NCT03877809 clinical trial and treated with 0.5-2 mg/day sirolimus. Our data support the concept that autophagy, ULK1 expression, and α-globin chain reduction should be considered important endpoints in sirolimus-based clinical trials for β-thalassemias.

The Long Scientific Journey of Sirolimus (Rapamycin): From the Soil of Easter Island (Rapa Nui) to Applied Research and Clinical Trials on β-Thalassemia and Other Hemoglobinopathies

In this review article, we present the fascinating story of rapamycin (sirolimus), a drug able to induce γ-globin gene expression and increased production of fetal hemoglobin (HbF) in erythroid cells, including primary erythroid precursor cells (ErPCs) isolated from β-thalassemia patients. For this reason, rapamycin is considered of great interest for the treatment of β-thalassemia. In fact, high levels of HbF are known to be highly beneficial for β-thalassemia patients. The story of rapamycin discovery began in 1964, with METEI, the Medical Expedition to Easter Island (Rapa Nui). During this expedition, samples of the soil from different parts of the island were collected and, from this material, an antibiotic-producing microorganism (Streptomyces hygroscopicus) was identified. Rapamycin was extracted from the mycelium with organic solvents, isolated, and demonstrated to be very active as an anti-bacterial and anti-fungal agent. Later, rapamycin was demonstrated to inhibit the in vitro cell growth of tumor cell lines. More importantly, rapamycin was found to be an immunosuppressive agent applicable to prevent kidney rejection after transplantation. More recently, rapamycin was found to be a potent inducer of HbF both in vitro using ErPCs isolated from β-thalassemia patients, in vivo using experimental mice, and in patients treated with this compound. These studies were the basis for proposing clinical trials on β-thalassemia patients.

Combined approaches for increasing fetal hemoglobin (HbF) and de novo production of adult hemoglobin (HbA) in erythroid cells from β-thalassemia patients: treatment with HbF inducers and CRISPR-Cas9 based genome editing

Genome editing (GE) is one of the most efficient and useful molecular approaches to correct the effects of gene mutations in hereditary monogenetic diseases, including β-thalassemia. CRISPR-Cas9 gene editing has been proposed for effective correction of the β-thalassemia mutation, obtaining high-level "de novo" production of adult hemoglobin (HbA). In addition to the correction of the primary gene mutations causing β-thalassemia, several reports demonstrate that gene editing can be employed to increase fetal hemoglobin (HbF), obtaining important clinical benefits in treated β-thalassemia patients. This important objective can be achieved through CRISPR-Cas9 disruption of genes encoding transcriptional repressors of γ-globin gene expression (such as BCL11A, SOX6, KLF-1) or their binding sites in the HBG promoter, mimicking non-deletional and deletional HPFH mutations. These two approaches (β-globin gene correction and genome editing of the genes encoding repressors of γ-globin gene transcription) can be, at least in theory, combined. However, since multiplex CRISPR-Cas9 gene editing is associated with documented evidence concerning possible genotoxicity, this review is focused on the possibility to combine pharmacologically-mediated HbF induction protocols with the "de novo" production of HbA using CRISPR-Cas9 gene editing.

Effects of Sirolimus Treatment on Fetal Hemoglobin Production and Response to SARS-CoV-2 Vaccination: A Case Report Study

The β-thalassemias are a group of monogenic hereditary hematological disorders caused by deletions and/or mutations of the β-globin gene, leading to low or absent production of adult hemoglobin (HbA). For β-thalassemia, sirolimus has been under clinical consideration in two trials (NCT03877809 and NCT04247750). A reduced immune response to anti-SARS-CoV-2 vaccination has been reported in organ recipient patients treated with the immunosuppressant sirolimus. Therefore, there was some concern regarding the fact that monotherapy with sirolimus would reduce the antibody response after SARS-CoV-2 vaccination. In the representative clinical case reported in this study, sirolimus treatment induced the expected increase of fetal hemoglobin (HbF) but did not prevent the production of anti-SARS-CoV-2 IgG after vaccination with mRNA-1273 (Moderna). In our opinion, this case report should stimulate further studies on β-thalassemia patients under sirolimus monotherapy in order to confirm the safety (or even the positive effects) of sirolimus with respect to the humoral response to anti-SARS-CoV-2 vaccination. In addition, considering the extensive use of sirolimus for the treatment of other human pathologies (for instance, in organ transplantation, systemic lupus erythematosus, autoimmune cytopenia, and lymphangioleiomyomatosis), this case report study might be of general interest, as large numbers of patients are currently under sirolimus treatment.

Production and Characterization of K562 Cellular Clones Hyper-Expressing the Gene Encoding α-Globin: Preliminary Analysis of Biomarkers Associated with Autophagy

One of the most relevant pathophysiological hallmarks of β-thalassemia is the accumulation of toxic α-globin chains inside erythroid cells, which is responsible for their premature death (hemolysis). In this context, the availability of an experimental model system mimicking the excess in α-globin chain production is still lacking. The objective of the present study was to produce and characterize K562 cellular clones forced to produce high amounts of α-globin, in order to develop an experimental model system suitable for studies aimed at the reduction of the accumulation of toxic α-globin aggregates. In the present study, we produced and characterized K562 cellular clones that, unlike the original K562 cell line, stably produced high levels of α-globin protein. As expected, the obtained clones had a tendency to undergo apoptosis that was proportional to the accumulation of α-globin, confirming the pivotal role of α-globin accumulation in damaging erythroid cells. Interestingly, the obtained clones seemed to trigger autophagy spontaneously, probably to overcome the accumulation/toxicity of the α-globin. We propose this new model system for the screening of pharmacological agents able to activate the full program of autophagy to reduce α-globin accumulation, but the model may be also suitable for new therapeutical approaches targeted at the reduction of the expression of the α-globin gene.

Effects of Sirolimus treatment on patients with β-Thalassemia: Lymphocyte immunophenotype and biological activity of memory CD4+ and CD8+ T cells

Inhibitors of the mammalian target of rapamycin (mTOR) have been proposed to improve vaccine responses, especially in the elderly. Accordingly, testing mTOR inhibitors (such as Sirolimus) and other geroprotective drugs might be considered a key strategy to improve overall health resilience of aged populations. In this respect, Sirolimus (also known as rapamycin) is of great interest, in consideration of the fact that it is extensively used in routine therapy and in clinical studies for the treatment of several diseases. Recently, Sirolimus has been considered in laboratory and clinical studies aimed to find novel protocols for the therapy of hemoglobinopathies (e.g. β-Thalassemia). The objective of the present study was to analyse the activity of CD4⁺ and CD8⁺ T cells in β-Thalassemia patients treated with Sirolimus, taking advantages from the availability of cellular samples of the NCT03877809 clinical trial. The approach was to verify IFN-γ releases following stimulation of peripheral blood mononuclear cells (PBMCs) to stimulatory CEF and CEFTA peptide pools, stimulatory for CD4⁺ and CD8⁺ T cells, respectively. The main results of the present study are that treatment of β-Thalassemia patients with Sirolimus has a positive impact on the biological activity and number of memory CD4⁺ and CD8⁺ T cells releasing IFN-γ following stimulation with antigenic stimuli present in immunological memory. These data are to our knowledge novel and in our opinion of interest, in consideration of the fact that β-Thalassemia patients are considered prone to immune deficiency.

A Rational Approach to Drug Repositioning in β-thalassemia: Induction of Fetal Hemoglobin by Established Drugs

Drug repositioning and the relevance of orphan drug designation for β-thalassemia is reviewed. Drug repositioning and similar terms ('drug repurposing', 'drug reprofiling', 'drug redirecting', 'drug rescue', 'drug re-tasking' and/or 'drug rediscovery') have gained great attention, especially in the field or rare diseases (RDs), and represent relevant novel drug development strategies to be considered together with the "off-label" use of pharmaceutical products under clinical trial regimen. The most significant advantage of drug repositioning over traditional drug development is that the repositioned drug has already passed a significant number of short- and long-term toxicity tests, as well as it has already undergone pharmacokinetic and pharmacodynamic (PK/PD) studies. The established safety of repositioned drugs is known to significantly reduce the probability of project failure. Furthermore, development of repurposed drugs can shorten much of the time needed to bring a drug to market. Finally, patent filing of repurposed drugs is expected to catch the attention of pharmaceutical industries interested in the development of therapeutic protocols for RDs. Repurposed molecules that could be proposed as potential drugs for β-thalassemia, will be reported, with some of the most solid examples, including sirolimus (rapamycin) that recently has been tested in a pilot clinical trial.