RARE DISEASE
Hemoglobin H disease
Hemoglobin H disease
Hemoglobin H disease
Synonyms: Alpha-thalassemia intermedia, HbH disease
Synonyms: Alpha-thalassemia intermedia, HbH disease
Synonyms: Alpha-thalassemia intermedia, HbH disease
Drug discovery
1
drug
With orphan designation
Overview
Hemoglobin H Disease Overview
Hemoglobin H (HbH) disease is an intermediate alpha-thalassemia caused by inactivation of three alpha-globin alleles (HBA1/HBA2), leading to chronic hemolytic anemia, marked microcytosis, hypochromia, and variable hepatosplenomegaly [1][2][13]. Severity ranges from mild (deletional mutations) to transfusion-dependent anemia (non-deletional forms, e.g., HbH-Constant Spring) [5][10]. Complications include iron overload, growth delays, and cholelithiasis [1][4]. Management focuses on intermittent transfusions during infections/pregnancy, iron chelation, and avoidance of oxidant drugs [5][9]. Genetic counseling is critical for family planning [5][13].
Burden
Chronic anemia reduces quality of life, with fatigue, growth impairment, and complications (e.g., gallstones) [1][10].
Non-deletional HbH (~25% of cases) increases transfusion dependence, iron overload, and mortality risk [2][11].
Psychosocial and economic impacts due to lifelong monitoring and treatment [6][10].
Therapies
Transfusions: Indicated for acute anemia (Hb <6 g/dL) triggered by infections, oxidant exposure, or pregnancy [5][9].
Iron chelation: Required for transfusion-associated or non-transfusion-related iron overload [5][16].
Splenectomy: Reserved for hypersplenism or frequent transfusion needs (common in non-deletional HbH) [5][10].
Categories: rare endocrine diseases, rare genetic diseases, rare hematological diseases, rare transplant-related disorders
Research Papers
160 drug discovery papers about Hemoglobin H disease, with 2 first-in-class and 3 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
160 drug discovery papers about Hemoglobin H disease, with 2 first-in-class and 3 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
2026-07-19 | Evaluating mitapivat for the treatment of alpha or beta thalassemia.
Thalassemia is a group of diverse genetic disorders with worldwide distribution that affects hemoglobin synthesis. Until recently, the therapeutic approach to thalassemia was symptomatic, relying on red blood cell transfusions, treatment of comorbidities and of disease-related complications. However, novel therapeutic agents have recently been developed and are gradually being integrated into routine clinical practice. One of the most promising agents is mitapivat (AG348), an oral pyruvate kinase activator that enhances the erythrocytic adenosine triphosphate (ATP) production. After series of preclinical and clinical studies, mitapivat has been suggested to be a safe and effective disease modifier for thalassemia. Large double blind randomized clinical trials have indicated that mitapivat may increase baseline hemoglobin levels, reduce transfusion burden, control ineffective erythropoiesis and hemolysis and improve quality of life. Mitapivat presents as a potential game-changer in the management of patients with both α- and β-thalassemia, regardless of transfusion dependency. However, further post-marketing evidence is required in order to evaluate mitapivat profile under real‑world conditions and routine clinical practice.
2026-06-23 | Chronic Red Cell Exchange for the Management of Alpha Thalassemia Major Complicated by Iron Overload.
Alpha thalassemia major is a severe hemoglobinopathy characterized by absent or markedly reduced alpha-globin production, necessitating lifelong blood transfusions. Chronic simple transfusions can lead to significant iron overload, often requiring iron chelation therapy. However, some patients are unable to tolerate chelation or chelation is insufficient, highlighting the need for alternative strategies for managing iron overload. This study is one of the first to evaluate the feasibility, safety, and efficacy of red blood cell exchange (RBCX) as a therapeutic option for managing iron overload while improving hemoglobin function in an alpha thalassemia major patient with iron overload despite chelation therapy. RBCX therapy was performed approximately every 3 weeks over 1 year, with frequent adjustment of exchange parameters to meet pre-transfusion target levels of functional hemoglobin. Serum ferritin levels, hemoglobin electrophoresis, and functional hemoglobin levels were tracked with each exchange transfusion. For each RBCX treatment, variant hemoglobins decreased by 3.8-fold (from 19.9% to 8.9%) and functional hemoglobin levels increased approximately 3.0 g/dL. RBCX was well tolerated and associated with a marked reduction in systemic iron burden, with serum ferritin declining 7.4-fold (86.4%) over 1 year of therapy, followed by a rise after cessation of RBCX. Cardiac iron remained within normal limits throughout the study period. In contrast, liver iron demonstrated a transient increase shortly after initiation of RBCX, but ultimately declined to levels below baseline after 1 year, even during a period in the absence of iron chelation. These findings suggest that RBCX exerts a meaningful effect on iron homeostasis and raises the possibility of a synergistic benefit when combined with iron chelation. This case highlights that RBCX is a viable therapeutic strategy to treat iron overload in patients with alpha thalassemia major.
2026-06-18 | Delayed Recognition and Significant Morbidity in Adults with Non-Transfusion-Dependent Thalassemia.
Non-transfusion-dependent thalassemia (NTDT) is characterized by variable degrees of anemia, ineffective erythropoiesis, and iron overload, with a heightened risk of age-related complications. However, the clinical profiles of patients who first present to thalassemia care in adulthood, as well as the gaps in management, are poorly described. In a multi-institutional study, we identified 82 patients with NTDT aged ≥18 years who were referred to three U.S. thalassemia centers between 2013 and 2023. Data were collected by manual chart review and included clinical history, laboratory tests, and imaging. The median age at initial visit was 36.8 years (range 18-74), and 37 (45%) of the patients had α-thalassemia, while 45 (55%) had β-thalassemia. Complications assessed included symptomatic anemia, prior splenectomy, extramedullary hematopoiesis, iron overload, pulmonary hypertension, cardiac arrhythmia, endocrine complications, and thrombosis. Iron overload was common, with 71% of available liver MRIs showing hepatic iron >5 mg Fe/g dry weight. Among patients with LIC >5 mg Fe/g, only 24.4% were on chelation at referral. Strikingly, 49% of patients were recommended to start regular transfusions following the consultation, predominantly for symptomatic anemia or complications of ineffective erythropoiesis. Patients with NTDT referred for initial comprehensive thalassemia care in adulthood had high rates of morbidities and undertreated iron overload. The criteria for initiating regular transfusions must be widely implemented to mitigate long-term complications and improve the quality of life of adults with NTDT.
2026-06-08 | Unveiling molecular mechanisms and therapeutic targets in HbH-CS disease: a focus on oxidative stress and mitochondrial dysfunction.
This study aimed to investigate the molecular mechanisms and therapeutic targets related to oxidative stress and mitochondrial dysfunction in Hemoglobin H-Constant Spring (HbH-CS) disease. HbH-CS differentially expressed genes (DEGs) were selected from a microarray dataset. Oxidative stress-related genes (OSGs) and mitochondrial function-related genes (MiRGs) were retrieved from public databases. Oxidative stress and mitochondrial function-related genes (OMRGs) were defined as the intersection of HbH-CS DEGs, OSGs, and MiRGs. Programmed cell death (PCD) mechanisms and functional enrichment analyses were subsequently investigated. A protein-protein interaction (PPI) network was constructed to identify hub genes, and potential regulatory mechanisms and expression levels of candidate genes were further explored. A total of 98 OMRGs were identified, which were associated with cellular respiration, oxidative stress response, mitochondrial membrane, and apoptotic signaling. Apoptosis was determined to be the primary PCD mechanism. Three hub genes were identified: AKT serine/threonine kinase 1 (AKT1), B cell lymphoma/leukemia-2 (BCL2), and cytochrome c, somatic (CYCS). Additionally, RNA-binding motif protein 15B (RBM15B) was recognized as a shared N6-methyladenosine (m6A) regulator. The mRNA expression levels of these four genes were significantly downregulated in HbH-CS patients. These findings provide novel insights into the molecular mechanisms and identify potential therapeutic targets for clinical intervention.
2026-06-08 | Derivation and Pluripotency Validation of Six iPSC Lines From Amniotic Fluid Carrying Intermediate α-Thalassemia Genotypes (--3.7/αSEA and --4.2/αSEA).
Thalassemia intermedia (TI), or hemoglobin H (Hb H) disease, presents significant clinical heterogeneity, and its pathogenesis remains unclear. This study aimed to establish induced pluripotent stem cells (iPSCs) from amniotic fluid (AF) cells of fetuses diagnosed with intermediate α-thalassemia genotypes (-α3.7/--SEA and -α4.2/--SEA) to provide a robust in vitro model for investigating disease mechanisms and exploring therapeutic strategies. AF cells from six TI fetuses were reprogrammed using nonintegrating episomal vectors via electro-transfection. The resulting iPSC lines underwent comprehensive characterization, including alkaline phosphatase (AP) staining, immunofluorescence (IF) for pluripotency markers (e.g., OCT-4, SOX-2, and TRA-1-60), quantitative reverse transcription real-time PCR (RT-qPCR) for the expression of pluripotency genes, G-band karyotyping, and genetic analysis for thalassemia. Differentiation potential was assessed in vivo via teratoma formation in immunodeficient mice and in vitro through directed hematopoietic differentiation. Six stable iPSC lines were successfully established. All lines retained the progenitor's intermediate α-thalassemia genotype and exhibited normal karyotypes. They displayed typical embryonic stem cell (ESC)-like morphology, were positive for AP, and expressed key pluripotency markers. In vivo, all lines robustly formed teratomas containing tissues derived from all three germ layers (endoderm, mesoderm, and ectoderm). Furthermore, in vitro hematopoietic differentiation protocols successfully induced the iPSCs to generate CD34+/CD43+ hematopoietic progenitors, which were functionally validated by their ability to form hematopoietic colonies in colony-forming unit (CFU) assays. We have successfully derived and comprehensively characterized six patient-specific iPSC lines from intermediate α-thalassemia fetuses. These cell lines demonstrate robust pluripotency and maintain the capacity for hematopoietic differentiation. They represent a valuable resource for investigating TI pathophysiology, screening novel drugs, and developing future cell-based therapeutic strategies.
2026-07-19 | Evaluating mitapivat for the treatment of alpha or beta thalassemia.
Thalassemia is a group of diverse genetic disorders with worldwide distribution that affects hemoglobin synthesis. Until recently, the therapeutic approach to thalassemia was symptomatic, relying on red blood cell transfusions, treatment of comorbidities and of disease-related complications. However, novel therapeutic agents have recently been developed and are gradually being integrated into routine clinical practice. One of the most promising agents is mitapivat (AG348), an oral pyruvate kinase activator that enhances the erythrocytic adenosine triphosphate (ATP) production. After series of preclinical and clinical studies, mitapivat has been suggested to be a safe and effective disease modifier for thalassemia. Large double blind randomized clinical trials have indicated that mitapivat may increase baseline hemoglobin levels, reduce transfusion burden, control ineffective erythropoiesis and hemolysis and improve quality of life. Mitapivat presents as a potential game-changer in the management of patients with both α- and β-thalassemia, regardless of transfusion dependency. However, further post-marketing evidence is required in order to evaluate mitapivat profile under real‑world conditions and routine clinical practice.
2026-06-23 | Chronic Red Cell Exchange for the Management of Alpha Thalassemia Major Complicated by Iron Overload.
Alpha thalassemia major is a severe hemoglobinopathy characterized by absent or markedly reduced alpha-globin production, necessitating lifelong blood transfusions. Chronic simple transfusions can lead to significant iron overload, often requiring iron chelation therapy. However, some patients are unable to tolerate chelation or chelation is insufficient, highlighting the need for alternative strategies for managing iron overload. This study is one of the first to evaluate the feasibility, safety, and efficacy of red blood cell exchange (RBCX) as a therapeutic option for managing iron overload while improving hemoglobin function in an alpha thalassemia major patient with iron overload despite chelation therapy. RBCX therapy was performed approximately every 3 weeks over 1 year, with frequent adjustment of exchange parameters to meet pre-transfusion target levels of functional hemoglobin. Serum ferritin levels, hemoglobin electrophoresis, and functional hemoglobin levels were tracked with each exchange transfusion. For each RBCX treatment, variant hemoglobins decreased by 3.8-fold (from 19.9% to 8.9%) and functional hemoglobin levels increased approximately 3.0 g/dL. RBCX was well tolerated and associated with a marked reduction in systemic iron burden, with serum ferritin declining 7.4-fold (86.4%) over 1 year of therapy, followed by a rise after cessation of RBCX. Cardiac iron remained within normal limits throughout the study period. In contrast, liver iron demonstrated a transient increase shortly after initiation of RBCX, but ultimately declined to levels below baseline after 1 year, even during a period in the absence of iron chelation. These findings suggest that RBCX exerts a meaningful effect on iron homeostasis and raises the possibility of a synergistic benefit when combined with iron chelation. This case highlights that RBCX is a viable therapeutic strategy to treat iron overload in patients with alpha thalassemia major.
2026-06-18 | Delayed Recognition and Significant Morbidity in Adults with Non-Transfusion-Dependent Thalassemia.
Non-transfusion-dependent thalassemia (NTDT) is characterized by variable degrees of anemia, ineffective erythropoiesis, and iron overload, with a heightened risk of age-related complications. However, the clinical profiles of patients who first present to thalassemia care in adulthood, as well as the gaps in management, are poorly described. In a multi-institutional study, we identified 82 patients with NTDT aged ≥18 years who were referred to three U.S. thalassemia centers between 2013 and 2023. Data were collected by manual chart review and included clinical history, laboratory tests, and imaging. The median age at initial visit was 36.8 years (range 18-74), and 37 (45%) of the patients had α-thalassemia, while 45 (55%) had β-thalassemia. Complications assessed included symptomatic anemia, prior splenectomy, extramedullary hematopoiesis, iron overload, pulmonary hypertension, cardiac arrhythmia, endocrine complications, and thrombosis. Iron overload was common, with 71% of available liver MRIs showing hepatic iron >5 mg Fe/g dry weight. Among patients with LIC >5 mg Fe/g, only 24.4% were on chelation at referral. Strikingly, 49% of patients were recommended to start regular transfusions following the consultation, predominantly for symptomatic anemia or complications of ineffective erythropoiesis. Patients with NTDT referred for initial comprehensive thalassemia care in adulthood had high rates of morbidities and undertreated iron overload. The criteria for initiating regular transfusions must be widely implemented to mitigate long-term complications and improve the quality of life of adults with NTDT.
2026-06-08 | Unveiling molecular mechanisms and therapeutic targets in HbH-CS disease: a focus on oxidative stress and mitochondrial dysfunction.
This study aimed to investigate the molecular mechanisms and therapeutic targets related to oxidative stress and mitochondrial dysfunction in Hemoglobin H-Constant Spring (HbH-CS) disease. HbH-CS differentially expressed genes (DEGs) were selected from a microarray dataset. Oxidative stress-related genes (OSGs) and mitochondrial function-related genes (MiRGs) were retrieved from public databases. Oxidative stress and mitochondrial function-related genes (OMRGs) were defined as the intersection of HbH-CS DEGs, OSGs, and MiRGs. Programmed cell death (PCD) mechanisms and functional enrichment analyses were subsequently investigated. A protein-protein interaction (PPI) network was constructed to identify hub genes, and potential regulatory mechanisms and expression levels of candidate genes were further explored. A total of 98 OMRGs were identified, which were associated with cellular respiration, oxidative stress response, mitochondrial membrane, and apoptotic signaling. Apoptosis was determined to be the primary PCD mechanism. Three hub genes were identified: AKT serine/threonine kinase 1 (AKT1), B cell lymphoma/leukemia-2 (BCL2), and cytochrome c, somatic (CYCS). Additionally, RNA-binding motif protein 15B (RBM15B) was recognized as a shared N6-methyladenosine (m6A) regulator. The mRNA expression levels of these four genes were significantly downregulated in HbH-CS patients. These findings provide novel insights into the molecular mechanisms and identify potential therapeutic targets for clinical intervention.
2026-06-08 | Derivation and Pluripotency Validation of Six iPSC Lines From Amniotic Fluid Carrying Intermediate α-Thalassemia Genotypes (--3.7/αSEA and --4.2/αSEA).
Thalassemia intermedia (TI), or hemoglobin H (Hb H) disease, presents significant clinical heterogeneity, and its pathogenesis remains unclear. This study aimed to establish induced pluripotent stem cells (iPSCs) from amniotic fluid (AF) cells of fetuses diagnosed with intermediate α-thalassemia genotypes (-α3.7/--SEA and -α4.2/--SEA) to provide a robust in vitro model for investigating disease mechanisms and exploring therapeutic strategies. AF cells from six TI fetuses were reprogrammed using nonintegrating episomal vectors via electro-transfection. The resulting iPSC lines underwent comprehensive characterization, including alkaline phosphatase (AP) staining, immunofluorescence (IF) for pluripotency markers (e.g., OCT-4, SOX-2, and TRA-1-60), quantitative reverse transcription real-time PCR (RT-qPCR) for the expression of pluripotency genes, G-band karyotyping, and genetic analysis for thalassemia. Differentiation potential was assessed in vivo via teratoma formation in immunodeficient mice and in vitro through directed hematopoietic differentiation. Six stable iPSC lines were successfully established. All lines retained the progenitor's intermediate α-thalassemia genotype and exhibited normal karyotypes. They displayed typical embryonic stem cell (ESC)-like morphology, were positive for AP, and expressed key pluripotency markers. In vivo, all lines robustly formed teratomas containing tissues derived from all three germ layers (endoderm, mesoderm, and ectoderm). Furthermore, in vitro hematopoietic differentiation protocols successfully induced the iPSCs to generate CD34+/CD43+ hematopoietic progenitors, which were functionally validated by their ability to form hematopoietic colonies in colony-forming unit (CFU) assays. We have successfully derived and comprehensively characterized six patient-specific iPSC lines from intermediate α-thalassemia fetuses. These cell lines demonstrate robust pluripotency and maintain the capacity for hematopoietic differentiation. They represent a valuable resource for investigating TI pathophysiology, screening novel drugs, and developing future cell-based therapeutic strategies.
Access all drug discovery papers and probability of success in trials forecasts:
Access all drug discovery papers and probability of success in trials forecasts:
Drug Discovery Landscape
1 orphan drug designation for Hemoglobin H disease, including 1 approved therapy.
1 orphan drug designation for Hemoglobin H disease, including 1 approved therapy.
Drug | Therapy type | Regulator | Orphan designation | Approval | Sponsor |
|---|---|---|---|---|---|
Mitapivat sulfate [Pyrukynd] | small molecules | EMA | 2024-01-12 | 2026-05-22 | Agios Netherlands B.V. |
Let's accelerate rare disease drug discovery
Let's accelerate drug discovery
Get access to Explority AI's forecasts to outperform average preclinical success rates. Whether you're expanding your R&D pipeline, evaluating a partnership, or simply have a question — we'd love to hear from you.