Pyruvate kinase activators in hereditary haemolytic anaemias: current evidence and clinical potential.

# Pyruvate kinase activators in hereditary haemolytic anaemias: current evidence and clinical potential *The Lancet 2026* Therapeutics Pyruvate kinase activators in hereditary haemolytic anaemias: current evidence and clinical potential Thomas Doeven, Andreas Glenthøj, Rachael F Grace, Eduard J van Beers Hereditary haemolytic anaemias represent the most prevalent group of genetic disorders worldwide and have a Lancet 2026; 407: 1383–96 substantial impact on global health. Current treatments are few and primarily supportive. Recent studies suggest a Published Online crucial and overlapping role of metabolic impairment of red blood cells in these diseases, extending beyond the March 12, 2026 primary genetic defect. Pyruvate kinase activators enhance glycolysis, thereby targeting this shared metabolic https://doi.org/10.1016/ S0140-6736(26)00150-9 impairment by increasing ATP production and improving cellular homeostasis. The first pyruvate kinase activator Center for Benign has been approved for the treatment of pyruvate kinase deficiency. Clinical trials evaluating pyruvate kinase activators Haematology, Thrombosis and in other haemolytic disorders, including thalassaemia, sickle cell disease, and red blood cell membrane disorders Haemostasis, Van have provided evidence of clinical ecacy by ameliorating haemolytic anaemia and improving other disease-related Creveldkliniek, University outcomes, while maintaining a generally favourable safety profile. Ongoing preclinical and translational research Medical Center Utrecht, Utrecht University, Utrecht, continues to provide further insights into other potential indications for pyruvate kinase activators. Netherlands (T Doeven MD, E J van Beers MD PhD); Danish Introduction Red blood cell metabolism: the basis for cellular Red Blood Cell Center, Hereditary haemolytic anaemias comprise a wide range homeostasis and survival Department of Haematology, Copenhagen University of disorders, including haemoglobinopathies, red blood Glycolytic dependency of red blood cells and the key role Hospital - Rigshospitalet, cell membrane disorders, and enzyme deficiencies. of PK Copenhagen, Denmark These disorders are characterised by haemolysis, Mature, non-mutated red blood cells do not have (A Glenthøj MD); Department splenomegaly, and secondary haemochromatosis, with mitochondria and are therefore incapable of generating of Paediatrics, Dana-Farber/ Boston Children’s Cancer and phenotypes ranging from mild anaemia to life- ATP through mitochondrial cellular respiration, relying Blood Disorders Center, threatening, transfusion-dependent haemolysis.1,2 exclusively on anaerobic glycolysis.10 PK catalyses the final Harvard Medical School, Current treatment strategies are primarily supportive, and irreversible step in glycolysis, yielding one ATP Boston, MA, USA (R F Grace MD) including blood transfusions, iron chelation, and molecule. As glycolytic intermediates are cut in half by Correspondence to: splenectomy. Curative options, including allogenic stem aldolase before reaching PK, the net yield is two molecules Dr Eduard J van Beers, Center for Benign Haematology, cell transplantation and emerging gene therapies, carry of ATP per glucose molecule.11 The total net production of Thrombosis and Haemostasis, substantial risks and remain inaccessible to most.3 glycolysis is therefore dependent on PK. The other product Van Creveldkliniek, University Consequently, a substantial unmet therapeutic need of PK, pyruvate, serves as an important substrate for Medical Center Utrecht, Utrecht remains, especially for symptomatic patients with mild- several subsequent metabolic pathways in nucleated cells.12 University, Utrecht 3584 CX, Netherlands to-moderate disease burden and those not eligible or The human body contains four dierent PK E.J.vanBeers-3@umcutrecht.nl comfortable with the current risks of curative isoenzymes, encoded by two distinct genes. PKM interventions. encodes PKM1 and PKM2, found in skeletal muscle, the Pyruvate kinase (PK) activators represent a new heart, the brain, and in fetal and several mature tissues, targeted therapeutic approach for hereditary haemolytic including proliferating cells. PKLR encodes PKL, found anaemias, addressing a fundamental metabolic primarily in the liver and PKR, confined to the red blood vulnerability in red blood cells. PK activators enhance cell.12,13 The PKR isoenzyme is a tetrameric enzyme, with glycolytic flux and ATP generation within red blood cells, two major conformational states: the T-state (tense) and counteracting the depletion that contributes to haemolysis. Advances in the understanding of the role of cellular metabolism in other hereditary haemolytic Search strategy and selection criteria anaemias have shown an overlapping role of glycolytic We searched the PubMed database for relevant publications impairment, not limited to enzyme deficiencies.4–6 These from its inception to April 23, 2025, using search terms insights have led to the exploration of PK activators “pyruvate kinase activator”, “PK activator”, “mitapivat“, across PK deficiency and other hereditary haemolytic “AG-348”, “etavopivat”, “FT-4202”, “tebapivat”, and anaemias, including thalassaemia, sickle cell disease, “AG-946”. The reference lists of the identified relevant and red blood cell membrane disorders.7–9 publications were reviewed to identify additional This Therapeutics paper provides a comprehensive publications of interest. Relevant clinical trials were identified overview of red blood cell metabolism and its essential in both the US National Library of Medicine clinical trials role in supporting red blood cell survival. The therapeutic database, the EU Clinical Trials Register, and the WHO rationale and the mechanisms of action of PK activators International Clinical Trials Registry Platform using the search across hereditary haemolytic anaemias are explained in terms above. Selection of relevant publications prioritised addition to the current evidence on safety and ecacy those published within the past 3 years, but older work was outcomes, future directions, and clinical potential of this included where relevant. emerging therapeutic class. Therapeutics the active R-state (relaxed). The enzyme exists in an all primarily regulated by ATP-dependent processes.23 equilibrium between the two states, which transitions to Decreased deformability causes splenic sequestration the active R-state upon binding of endogenous allosteric and extravascular haemolysis, and might also activators, such as fructose-1,6-bisphosphate, at its contribute to intravascular haemolysis in sickle cell regulatory site. Because the R-state has an increased disease.23 ATP depletion in red blood cells prevents anity for its substrate, phosphoenolpyruvate, PK ATP-dependent protein 4.1R (P4.1) phosphorylation, activity, and glycolytic flux become enhanced, allowing strengthening membrane–spectrin interactions, more ecient catalysis.14 thereby reducing membrane flexibility.24 Moreover, ATP depletion indirectly leads to oxidative stress- Energy-driven mechanisms in red blood cell related hyperphosphorylation of band 3.21 This maintenance and survival substantially alters the membrane’s structure and Adequate glycolytic functioning is essential for ATP function, also aecting membrane-bound glycolytic generation, and glycolytic impairment causes haemolysis, enzymes and ion-transporters.22,25 Lastly, insucient as seen in PK deficiency.10 ATP supports several important ATP levels impair plasma membrane Ca²+-ATPase energy-driven mechanisms that are essential to cellular functioning, causing intracellular Ca²+ concentrations functioning and survival. These mechanisms include to rise.26 This activates the Ca²+-sensitive K+ (Gardos) regulation and maintenance of oxidative and metabolic channels, leading to K+ and water eux, resulting in homeostasis; support of red blood cell deformability, cellular dehydration. This mechanism underlies measured by membrane integrity, flexibility, and cellular hereditary xerocytosis but also occurs in PK deficiency hydration; preservation of membrane asymmetry; and and sickle cell disease.23 High Ca²+ concentrations also eective erythropoiesis. Impaired glycolysis leads to activate proteolytic enzymes such as calpain, which dysfunction of these mechanisms, consequently disrupt membrane–protein interactions and induce resulting in anaemia. Although mechanisms in the membrane vesiculation.27 Collectively, these following section and figure 1 are presented individually, mechanisms reduce cellular deformability, ultimately they are highly interrelated. promoting haemolysis. Oxidative and metabolic homeostasis Membrane asymmetry ATP is required to convert glucose into glucose-6- ATP is required for maintaining membrane asymmetry phosphate, which fuels the hexose monophosphate by driving energy-dependent transport proteins.28 The pathway (HMP). This pathway generates nicotinamide confinement of phosphatidylserine to the inner layer is adenine dinucleotide phosphate (NADPH), used to important as phosphatidylserine exposure is prothrom- regenerate reduced glutathione. Glutathione is a key botic and induces phagocytosis by splenic macrophages.23 antioxidant that protects haemoglobin, glycolytic ATP depletion leads to increased intracellular Ca²+, which enzymes, and membrane proteins from oxidative enhances scramblase activity and inhibits flippase damage.15,16 Severe ATP depletion can impair glucose activity, resulting in increased phosphatidylserine phosphorylation, reducing HMP substrate availability exposure.23,29 This mechanism thus contributes to and potentially limiting NADPH production.15 haemolysis, as has been observed in sickle cell disease Consequently, glutathione regeneration might be and thalassaemia.26,30 restricted, resulting in cumulative oxidative stress.16,17 Older functional studies reported conflicting findings on Erythropoiesis whether HMP shunt capacity is diminished in small case Erythroid maturation is energy demanding, with series of glycolytic enzyme deficiencies with severe ATP maturing red blood cells progressively shifting from depletion.18,19 In PK deficiency, one such study found aerobic mechanisms towards anaerobic glycolysis, reduced HMP shunt activity following oxidative stress, making glycolytic functioning especially important but this was based on only five patients.18 Metabolomics during terminal erythroid stages.31 Glycolytic on peripheral blood, however, also suggest reduced HMP impairment might contribute to ineective activity in PK deficiency compared with healthy controls.20 erythropoiesis via several mechanisms. In PK In disorders such as sickle cell disease and hereditary deficiency, reduced pyruvate generation forces red spherocytosis, oxidative stress contributes to haemolysis blood cell precursors to use alternative anaplerotic by inhibiting phosphatases and activating kinases, carbon entry (primarily α-ketoglutarate derived from causing excessive tyrosine phosphorylation of band 3, glutamine) as fuel for the tricarboxylic acid cycle. which destabilises the membrane–cytoskeletal network Consuming other carbons in early maturation stages and promotes red blood cell destruction.21,22 presumably reduces antioxidant potential at later stages, contributing to defective mitophagy and Cellular deformability phagocytosis of precursors.32,33 In thalassaemia, Red blood cell deformability is measured by membrane ineective erythropoiesis arises from excess unpaired flexibility, cytoskeletal integrity, and cellular hydration, α-globin or β-globin chains within erythroblasts, 1384 Therapeutics causing chronic oxidation and apoptosis of red blood Biological rationale for PK activators across hereditary cell precursors.34,35 Reduced ATP generation could haemolytic anaemias aggravate this process, as clearance of these chains ATP is essential for red cell homeostasis, supporting relies on ATP-dependent proteolytic mechanisms.8 metabolism, redox balance, membrane integrity, Lastly, phosphatidylserine exposure in erythroid hydration, and deformability, as well as erythropoiesis. precursors, triggered by low-energy states, also Anaemias with impairment of any of these mechanisms contributes to ineective erythropoiesis by promoting might benefit from treatment with PK activators. Red their phagocytic removal.30 blood cells in various hereditary haemolytic anaemias Haemolysis Antioxidant Oxidative ATP Antioxidants capacity damage ATP Protein 4.1R Stronger membrane–spectrin Flexibility hypophosphorylation interactions Integrity ATP Band 3 hyperphosphorylation Band 3–cytoskeleton dissociation Deformability Vesiculation Vesiculation Glycolysis ATP Ca2+-ATPase activity Intracellular Ca2+ Gardos channel activity Hydration Scramblase activity Membrane ATP Ca2+-ATPase activity Intracellular Ca2+ PS exposure Flippase activity asymmetry Ineffective erythropoiesis Antioxidant Reticulocyte Pyruvate Less fuel for TCA cycle Anaplerosis capacity maturation Figure 1: Pathways through which glycolytic dysfunction causes anaemia Impaired glycolytic function leads to anaemia through several mechanisms affecting red blood cell function, homeostasis, production, and survival. PS=phosphatidylserine. TCA=tricarboxylic acid. Figure created using biorender.com. Mechanism Diseases Dosages in Median range Mean range Bioavailability† Metabolism Elimination of action investigated in phase 2/3 t , h* (min, t, h* (±SD) (%) max ½ clinical trials clinical trials, max) mg Mitapivat Allosteric PKD, SCD, 5–200 BID 0·77 (0·48, 2·00)– 17·8 (3·3)– 72·7 CYP3A4, Primarily via (AG-348)13,40,41 activator of thalassaemia, 1·01 (0·50, 3·00)‡ 20·4 (3·6)‡ CYP3A5, hepatic PKR, PKM2, RBC membrane CYP1A2, metabolism and PKL disorders, and CYP2C8, (1·1–2·4% renal CDA II CYP2C9 clearance) Etavopivat Selective SCD and 200–400 QD 0·50 (0·5, 3·0)– 10·6 (2·4)– ·· CYP3A4, Primarily via (FT-4202)38,42 allosteric PKR thalassaemia 1·5 (0·5, 4·0) 13·8 (3·9) CYP3A5, hepatic activator CYP2C9 metabolism (0·8–1·7% renal clearance) Tebapivat Allosteric SCD and MDS 2·5–20 QD ·· ·· ·· ·· ·· (AG-946)39 activator of PKR and PKM2 t =time to maximum concentration. t=estimated terminal elimination half-life. PKR=pyruvate kinase R. PKD=pyruvate kinase deficiency. SCD=sickle cell disease. RBC=red max ½ blood cell. CDA II=congenital dyserythropoietic anaemia type 2. BID=twice daily. QD=once daily. MDS=myelodysplastic syndrome. *Results displayed are based on single dosage of either 30 mg, 120 mg, or 360 mg mitapivat or 200 mg, 400 mg, 700 mg, or 1000 mg etavopivat. †After administration of a single dose of 120 mg mitapivat. ‡Accuracy and reliability at higher dose levels (700–2500 mg) were influenced by duration of sampling and were therefore not included. Table 1: Pharmacodynamic and pharmacokinetic properties of current pyruvate kinase activators Therapeutics exist in a state of chronic metabolic stress with relative Mechanisms of action shortage of ATP due to an increased ATP demand to fuel PK activators enhance glycolytic flux, increasing ATP ATP-dependent compensatory mechanisms.12,36 However, levels and decreasing 2,3-DPG levels glycolytic functioning and ATP generation are often PK activators enhance PK activity by acting as an allosteric insucient or even impaired, promoting anaemia activator. The therapeutic agent was initially developed to through several mechanisms (figure 1).4,5 By increasing target the PKM2 paradox in the Warburg eect through glycolytic flux, ATP availability, and cell deformability, PK activation of the PKM2 isoform.37 However, shortly activators could improve anaemia and haemolysis across thereafter, mitapivat (formerly AG-348), a small allosteric a range of hereditary haemolytic anaemias. non-specific PK activator, was developed to target the mutant PK enzymes underlying the pathophysiology of PK deficiency.13 Binding of mitapivat to a pocket at the Glucose dimer–dimer interface of the PK enzyme, distinct from CH 2 OH the FBP binding site, leads to conformational changes O that increase phosp hoenolpyruvate binding anity. OH Etavopivat (formerly FT-4202) is a potent and selective OH OH PKR activator. Etavopivat, similar to mitapivat, stabilises OH ATP PKR, but has a higher selectivity for PKR.38 Tebapivat (formerly AG-946) is a second-generation PK activator optimised with increased potency, longer residence time, ADP HMP pathway G6-P and improved pharmacokinetics and pharmacodynamics, including longer half-life time (table 1).39 In the first preclinical study, mitapivat improved PKR activity across various mutant PK enzymes encompassing F6-P ATP a range of PK deficiency genotypes. Ex vivo mitapivat treatment of red blood cells from both healthy controls and patients with PK deficiency resulted in dose- ADP F1,6-BP dependent increases in PKR activity and thermostability, accompanied by increases in ATP and decreases in 2,3-diphosphoglycerate (2,3-DPG) levels (figure 2).13 Red blood cells from patients with PK deficiency of specific 1,3-DPG 1,3-DPG genotypes, for example deletions and nonsense variants, Rapoport–Luebering shunt exhibited little activation of PK upon treatment. This was most likely due to severely reduced PK protein levels, ADP ADP thereby leaving little PK enzyme available for activation, a 2,3-DPG (x2) finding confirmed in clinical trials.13,43 The observation ATP ATP that mitapivat also enhanced PK activity of the wild-type PKR enzyme suggested that patients with other red blood cell diseases characterised by relative ATP shortage, such 3-PG (x2) as thalassaemia and sickle cell disease, could also benefit from PK activators. This observation has been the main Mitapivat (AG-348) Etavopivat (FT-4202) rationale for investigating PK activators in other red blood Tebapivat (AG-946) cell diseases.13 PEP (x2) In preclinical β-thalassaemia studies, including a ADP ADP murine model and an ex vivo human red blood cell PKR model, mitapivat increased PK activity and ATP levels ATP ATP and ameliorated ineective erythropoiesis, iron overload, O and anaemia.5,44 In preclinical sickle cell disease studies HC 3 O– using red blood cells from mice, non-human primates, and humans, PK activators increased haemoglobin– O oxygen anity, reduced sickling, improved deformability, Pyruvate (x2) and decreased haemolysis.45–47 These findings support a dual mechanism of action in sickle cell disease: increased Figure 2: Effects of PK activation on glycolytic flux A simplified overview of the glycolytic pathway, highlighting the effects on ATP and ATP levels, leading to improved red blood cell 2,3-DPG following PK activation. G6-P=glucose-6-phosphate. HMP=hexose homeostasis, enhanced deformability, and reduced monophosphate. F6-P=fructose-6-phosphate. F1,6-BP=fructose-1,6-biphosphate. haemolysis; and decreased 2,3-DPG levels with increased 1,3-DPG=1,3-diphosphoglycerate. 2,3-DPG=2,3-diphosphoglycerate. haemoglobin–oxygen anity, reflected by reduced p50 3-PG=3-phosphoglycerate. PEP=phosphoenolpyruvate. PK=pyruvate kinase. PKR=pyruvate kinase R. Figure created using biorender.com. levels, and reduced red blood cell sickling. This 1386 Therapeutics Ca2+ K+ Ca2+ K+ Ca2+ PMCA Gardos channel Band 3 ATP Ca2+ Ca2+ Ca2+ Vesiculation PS exposure P AAnnkkkyyyrrriiinnn K+ Ca2+ Hydration Spectrins + – – Oxidative homeostasis PK activators Cytoskeletal integrity + + Glucose + 2 ATP 2 ADP Erythropoiesis F6-P HMP pathway 2 NAD+ + 2Pi 4 ADP Bone marrow 2NADH + 2H+ 4 ATP Pyruvate (x2) Figure 3: Effect of PK activators on cellular mechanisms that influence cell survival Intracellular and intramedullary pathways improved by PK activation across hereditary haemolytic anaemias. Mechanisms described from left to right. PK activators enhance glycolytic flux, thereby increasing ATP production, decreasing glycolytic intermediates, including 2,3-diphosphoglycerate, and restoring the metabolic and oxidative homeostasis. Consequently, less oxidative stress-related protein denaturation and band 3 phosphorylation occur. Increased ATP availability following PK activation might lead to enhanced PMCA-mediated Ca2+ efflux. As a result, decreased intracellular Ca2+concentrations prevent Gardos channel activation, thereby reducing K+ efflux and cellular dehydration. Moreover, decreased intracellular Ca2+ concentrations prevent membrane vesiculation, and enable the maintenance of membrane asymmetry, including less PS exposure. Increased ATP generation resulting from PK activation boosts protein phosphatase activity, thereby preventing the phosphorylation of band 3. This effect leads to enhanced cytoskeleton–membrane interactions, preventing membrane vesiculation and improving membrane integrity and flexibility. During erythropoiesis, PK activators increase glycolytic flux in the erythroblasts, enhancing the oxidative stress response and promoting erythroid maturation. Additionally, PK activators enhance mitochondrial biogenesis and promote mitochondrial clearance, thereby ameliorating mitochondrial dysfunction. Both mechanisms contribute to improved erythropoiesis. F6-P=fructose-6-phosphate. HMP=hexose monophosphate. P=phosphate. PK=pyruvate kinase. PMCA=plasma membrane Ca2+-ATPase. PS=phosphatidylserine. Figure created using biorender.com. mechanism is likely driven by the mitigation of sickle haemoglobin–oxygen anity, limiting HbS poly- haemoglobin (HbS) polymerisation.48 In a sickle cell merisation.49 In a preclinical hereditary spheroc ytosis disease study, red blood cells showed reduced micro- mouse model, mitapivat ameliorated anaemia and was vascular occlusion under both normoxic and hypoxic non-inferior to splenectomy.50 conditions following PK activation, reflecting improved Subsequent healthy volunteer phase 1 clinical trials of deformability and reduced sickling through improved PK activators have shown findings consistent with Therapeutics pre clinical studies, showing dose-dependent increases in spherocytosis mouse model, mitapivat reprogrammed ATP levels, haemoglobin–oxygen anity, and decreases in the red blood cell metabolome and ameliorated the 2,3-DPG concentration.40,42 intracellular redox milieu, supported by the downregulation of hypoxia-regulated genes and PK activators drive several cellular pathways that enzymes.50,51 Similar findings were observed following enhance red blood cell survival tebapivat exposure to hereditary spherocytosis aected See Online for appendix Figure 3 and appendix (p 1) present the eects of PK red blood cells ex vivo.52 Although steady state activation on cellular mechanisms. PK activators improve metabolomics have numerous limitations, these results the metabolic and oxidative homeostasis of the red blood suggest that PK activation enhances the antioxidant status cell. In β-thalassaemic erythroblasts and a hereditary of red blood cells. Other observations underlining the Design Dosage Population, n Treatment period Safety outcomes* Key efficacy outcomes Mitapivat Yang et al40 Phase 1, randomised, 30–2500 mg, single Healthy volunteers, 36 Single dose Headache (16·7%); nausea ATP ↑; 2,3-DPG decrease (NCT0210810)PK double-blind, placebo- dose (13·9%); AE ≥grade 3 (0%) controlled, single ascending dose Yang et al40 Phase 1, randomised, 15–700 mg BID Healthy volunteers, 36 2 weeks Headache (13·9%); nausea ATP ↑; 2,3-DPG decrease (NCT0214996) double-blind, placebo- (13·9%); AE ≥grade 3 (2%) controlled, multiple ascending dose Grace et al58 Phase 2, open-label, single- 50 mg or 300 mg PKD, not receiving 24 weeks (core); up Headache (44%); insomnia 20 (38%) participants with (NCT02476916): arm BID regular RBC to 8·5 years (40%); nausea (38%); Hb response ≥1·0 g/dL DRIVE PK transfusions, 52 (extension) AE ≥grade 3 (21%) Al-Samkari et al59 Phase 3, randomised, Dose escalation from PKD, not receiving 24 weeks (core); Nausea (18%); headache 16 (40%) participants with (NCT03548220): placebo-controlled 5 mg to 50 mg BID regular RBC 192 weeks (open- (15%); AE ≥grade 3 (25%) sustained Hb response ACTIVATE transfusions, 40 label extension) ≥1·5 g/dL Glenthøj et al60 Phase 3, open-label, single- Dose escalation from PKD, receiving regular 40 weeks (core); ALT increase (37%); headache 10 (37%) participants with (NCT03559699): arm 5 mg to 50 mg BID RBC transfusions, 27 192 weeks (open- (37%); nausea (19%); AST transfusion reduction ≥33% ACTIVATE-T label extension) increase (19%); fatigue (19%); AE ≥grade 3 (30%) van Beers et al61 Phase 3, open-label, single- Dose escalation from PKD, not receiving 96 weeks ·· Improvements in laboratory (NCT03853798) arm 5 mg to 50 mg BID regular RBC markers of erythropoiesis and ACTIVATE extension transfusions, 78 iron overload reduction in MRI liver iron content Kuo et al8 Phase 2, open-label, single- Dose escalation from α or β-NTDT, 20 24 weeks (core); Insomnia (50%); dizziness 16 (80%) participants with (NCT0369205) arm 50 mg to 100 mg BID 10 years (extension) (30%); headache (25%); AE Hb response of ≥1·0 g/dL ≥grade 3 (25%) Taher et al62 Phase 3, double-blind, 100 mg BID α or β-NTDT, 129 24 weeks (core); Headache (22%); insomnia 55 (42%) participants with (NCT04770753): randomised, placebo- 5 years (open-label (15%); nausea (12%); AE Hb response of ≥1·0 g/dL vs ENERGIZE controlled extension) ≥grade 3 (14%) 1 (2%) participant in the placebo group Xu et al63 Phase 1, open-label, single- Dose escalation from SCD HbSS, 17 2 weeks each dose Insomnia (41%); 9 (56·3%) participants with (NCT0400016) arm 5 mg to 100 mg BID (core); up to 6 years hyperglycaemia (29%); pain Hb response ≥1·0 g/dL (extension) (29%); AE ≥grade 3 (41%) Conrey et al64 Phase 2, open-label, single- Dose escalation from SCD HbSS, 15 Up to 144 weeks VOCs (66·7%); estradiol ↓ 14 (93%) participants with (NCT04000165) and arm 50 mg to 100 mg BID (53·3%); esterone ↓ (46·7%); Hb response ≥1·0 g/dL Xu et al63 extension AE ≥grade 3 (73·3%) van Dijk et al65 Phase 2, open-label, single- Dose escalation from SCD (HbSS, HbS-β0 thal, 8 weeks Headache (44%); ALT ↑ Mean reduction in point of (EudraCT 2019- arm 20 mg to 100 mg BID or HbS-β+ thal), 10 (44%); AST ↑ (22%); sickling of 9·7 ±6·2 mmHg 003438-18): dyspepsia (22%); AE ≥grade 3 (p=0·0032) from baseline ESTIMATE (not specified) van Dijk et al7 Phase 2, open-label, single- Dose escalation from SCD (HbSS, HbS-β0 thal, 52 weeks (core); ALT ↑ (70%); AST ↑ (60%); Mean reduction in point of (EudraCT 2019- arm 20 mg to 100 mg BID or HbS-β+ thal), 9 2 + 2 years headache (40%); AE ≥grade 3 sickling of 4·1 ± 5·6 mm Hg 003438-18): (extension)66 (20%) (p=0·0802) from baseline ESTIMATE extension Idowu et al67 Phase 2/3, double-blind, 50 mg or 100 mg SCD (any genotype), 52 12 weeks (phase 2); Headache (23%); arthralgia 12 (46%) participants with (NCT05031780): randomised, placebo- BID 52 weeks (phase 3); (15%); AE ≥grade 3 (15%) Hb response ≥1·0 g/dL in the RISE UP controlled 216 weeks (open- 50 mg group and 13 (50%) in label extension) the 100 mg group vs one (4%) in the placebo group after 12 weeks of treatment (Table 2 continues on next page) 1388 Therapeutics Design Dosage Population, n Treatment period Safety outcomes* Key efficacy outcomes (Continued from previous page) Etavopivat Forsyth et al42 Phase 1, randomised, 200–1000 mg, single Healthy volunteers, 24 Single dose Each reported event occurred ·· (NCT0381569) placebo-controlled, double- dose once; AE ≥grade 3 (4%) blind, single ascending dose Forsyth et al42 Phase 1, randomised, 100, 200, 300 BID or Healthy volunteers, 36 2 weeks Headache (28%); all other ATP ↑; 2,3-DPG decrease; (NCT0381569) placebo-controlled, double- 400 mg QD events occurred once; p50 decrease blind, multiple ascending AE ≥grade 3 (0%) dose Saraf et al68 Phase 1, randomised, 700 mg, single dose SCD (HbSS, HbS-β0 thal, Single dose Each reported event occurred ·· (NCT0381569) placebo-controlled, single HbS-β+ thal, or HbSC), 5 once; AE ≥grade 3 (0%) dose Saraf et al68 Phase 1, randomised, 300 mg or 600 mg SCD (HbSS, HbS-β0 thal, 2 weeks Headache (37·5%); nausea 11 (73%) participants with a (NCT0381569) placebo-controlled, double- QD HbS-β+ thal, HbSC), 16 (37·5%); dizziness (25%); Hb response ≥1·0 g/dL; blind, multiple ascending AE ≥grade 3 (12·5%) p50 decrease dose Saraf et al68 Phase 1, open-label, single- 400 mg QD SCD (HbSS, HbS-β0 thal, 12 weeks Headache (46·7%); nausea 11 (73%) participants with a (NCT0381569) arm HbS-β+ thal, or HbSC), (26·7%); dizziness (20%); Hb response ≥1·0 g/dL; 15 upper respiratory infection p50 decrease (20%); AE ≥grade 3 (40%) Safety and efficacy results correspond to the core period specified for each study. Results from the extension periods are listed where available. n=number of patients treated with pyruvate kinase activator (placebo not included). AE=adverse event. 2,3-DPG=2,3-diphosphoglycerate. BID=twice daily. PKD=pyruvate kinase deficiency. RBC=red blood cell. Hb=haemoglobin. ALT=alanine aminotransferase. AST=aspartate aminotransferase. NTDT=non-transfusion dependent thalassaemia. SCD=sickle cell disease. VOC=vaso-occlusive crisis. Thal=thalassaemia. QD=once daily. *Percentages represent the proportion of patients in whom the corresponding events occurred. Only safety outcomes from the intervention arm are displayed in the case of placebo-controlled trials. For each study, the three most frequent reported events (occurring in ≥10% of participants) are presented. Table 2: Clinical trials with completed and published results improved antioxidant status were seen in mitapivat- erythroblasts and improves both erythroblast ATP treated mice with sickle cell disease, showing reduced production and resistance to oxidative stress.44,57 erythrocyte reactive oxygen species.53 PK activators also improve the red blood cell PK activation across hereditary haemolytic hydration state. Ex vivo treatment with both mitapivat anaemias: evidence from clinical trials and tebapivat sign ifi cantly improved red blood cell PK activators have been evaluated in multiple clinical hydration in hereditary spherocytosis red blood cells trials across a wide range of haematological disorders and in some red blood cells aected by hereditary (tables 2 and 3). xerocytosis.52,54 These improvements in hydration, along with improvements in red blood cell deform- Efficacy outcomes ability, were also observed in sickled cells following PK deficiency mitapivat treatment.55 Additionally, PK activation in ex PK activators target the enzyme deficiency causing vivo red blood cells aected by sickle cell disease haemolytic anaemia. A phase 2 open-label clinical trial of resulted in reduced intracellular Ca²+ levels and mitapivat in adults with PK deficiency who were not enhanced Ca²+ eux.49,56 receiving regular transfusions was initiated in 2015.58 A PK activators support cytoskeletal integrity, leading to rapid and sustained haemoglobin response of 1·0 g/dL was improved red blood cell deformability. Both mitapivat and reached by 50% of the participants. These improvements tebapivat decreased the tyrosine phosphorylation of band 3 were accompanied by a decrease in haemolytic markers in a dose-dependent manner, likely through increased and reticulocyte count. A relationship was found between protein phosphatase activity. Additionally, mitapivat PK protein levels at baseline, PKLR genotype, and treatment increased membrane ankyrin-1 levels and haemoglobin response rate, with only those with at least ankyrin-1 and band 3 interactions.56 one missense PKLR mutation achieving haemoglobin PK activators might ameliorate ineective erythropoiesis. response.58 The two phase 3 mitapivat trials in adults with Mitapivat enhances erythropoiesis and erythroid PK deficiency therefore excluded patients with two non- maturation and decreases intramedullary apoptosis in missense mutations. The ACTIVATE trial was a phase 3, mice with β-thalassemia.44 In mice with β-thalassemia and randomised, placebo-controlled trial in adults with PK sickle cell disease, mitapivat also improves mitochondrial deficiency who were not receiving regular transfusions, in dysfunction during erythropoiesis by stimulating which an early and sustained haemoglobin response of at mitochondrial biogenesis and clearance.44,53 In addition, least 1·5 g/dL was observed in 16 (40%) of 40 participants, mitapivat reduces reactive oxygen species within the compared with 0 of 40 participants receiving placebo.59 The Therapeutics ACTIVATE-T trial was an open-label, single-arm study content, and erythropoiesis.61 Based on these results, conducted in adults with PK deficiency who were regularly mitapivat is approved in multiple global regions for the transfused. Following mitapivat treatment, ten (37%) of 27 treatment of symptomatic anaemia in adults with PK of the participants reached the transfusion reduction deficiency. endpoint, with six (22%) reaching a transfusion-free status Following these results, two phase 3 randomised, and three (11%) reaching a normal haemoglobin.60 In placebo-controlled clinical trials of treatment with addition, both trials showed improvements in haemolytic mitapivat in children with PK deficiency were initiated: markers, reticulocyte count, and patient-reported ACTIVATE-KidsT (regularly transfused) and ACTIVATE- outcomes, highlighting benefits on health-related quality of Kids (not regularly transfused).70,71 Although neither study life.69 In an extension study, mitapivat treatment also led to has yet been published, no new safety concerns in children improvements in markers of iron overload, liver iron have been reported to date. Design Dosage Population Treatment period Key outcome measures Mitapivat NCT05175105: Phase 3, double-blind, Dose escalation from Paediatric (age <18 years) patients 20 weeks (core); 5 years Hb response; sex hormones and ACTIVATE-Kids placebo-controlled 1 mg to 50 mg BID with non-transfusion-dependent (extension) BMD; haemolytic and erythropoietic PKD markers; iron markers; patient- reported outcomes; pharmacokinetics and pharmacodynamics NCT05144256: Phase 3, double-blind, Dose escalation from Paediatric (age <18 years) patients 32 weeks (core); 5 years Transfusion reduction response; ACTIVATE-KidsT placebo-controlled 1 mg to 50 mg BID with transfusion-dependent PKD (open-label extension) Hb response; sex hormones and BMD; iron markers; patient-reported outcomes; pharmacokinetics and pharmacodynamics NCT04770779: Phase 3, double-blind, 100 mg BID Transfusion dependent α or β-thal 48 weeks (core); 5 years Transfusion reduction response; iron ENERGIZE-T randomised, placebo- (open-label extension) markers; safety; pharmacokinetics controlled and pharmacodynamics NCT06286046: Phase 2, open-label, single- 100 mg BID SCD (HbSS or HbS-β0 thal) 6 months Kidney function and markers; RESIST arm hospitalisation rate; safety NCT05935202: Phase 2, open-label, single- Dose escalation from RBC membranopathies or CDA II 32 weeks (core); 1 year Safety; Hb response; haemolytic and SATISFY arm 50 mg to 100 mg BID (extension) erythropoietic markers; iron markers; patient-reported outcomes Etavopivat NCT04987489: Phase 2, open-label 400 mg QD SCD (cohort A); transfusion- 48 weeks Hb response; transfusion reduction GLADIOLUS dependent thal (cohort B); non- response; iron markers and overload transfusion dependent thal (cohort C) NCT06609226: Phase 3, open-label, roll-over 400 mg QD SCD or thal who completed at least 264 weeks Annualised rate of VOCs; Hb FLORAL one treatment period in the parent response; transfusion reduction study response; hospitalisation rate; safety NCT04624659: Phase 2/3, randomised, 200 mg or 400 mg QD SCD (any genotype) 52 weeks (core); 112 weeks Hb response; annualised rate of HIBISCUS double-blind, placebo- (open-label extension) VOCs; haemolytic and erythropoietic controlled markers; patient-reported outcomes NCT06612268: Phase 3, randomised, 400 mg QD Patients aged ≥12 years with SCD 52 weeks VOC rate; Hb response; haemolytic HIBISCUS 2 double-blind, placebo- (HbSS, HbS-β0 thal, or other and erythropoietic markers; patient- controlled syndrome) reported outcomes; kidney function NCT05953584: Phase 2, open-label, single- 400 mg QD Children with SCD (HbSS or HbS-β0 52 weeks (core); 48 weeks Timed average mean maximum HIBISCUS 3 arm thal) who are at increased risk of (extension) velocity of the internal carotid artery stroke and middle cerebral artery NCT06198712: Phase 1/2, open-label, single- 400 mg QD Paediatric (age 12–18 years) patients 24 weeks (core); 72 weeks Pharmacokinetics and HIBISCUS KIDS arm with SCD (any genotype) (extension) pharmacodynamics; Hb response; annualised rate of VOCs; patient- reported outcomes; timed average mean maximum velocity; safety NCT05725902 Phase 2, open-label, single- 400 mg QD Children with SCD (HbSS or HbS-β0 24 weeks Cerebral blood flow; oxygen ejection arm thal) fraction; cerebral metabolic rate of oxygen; safety NCT05568225: Phase 2, open-label 400 mg QD Very low, low, and intermediate risk 48 weeks Transfusion reduction response; Hb FORTITUDE MDS response; iron markers; platelet and neutrophil response; overall survival; safety (Table 3 continues on next page) 1390 Therapeutics Design Dosage Population Treatment period Key outcome measures (Continued from previous page) Tebapivat NCT04536792 Phase 1, randomised, 1 mg to 100 mg (SAD); Healthy volunteers Single dose (SAD); 2 weeks Safety; pharmacokinetics and double-blind, placebo- 1 mg to 20 mg QD (MAD) (MAD) pharmacodynamics controlled, SAD and MAD NCT04536792 Phase 1, open-label 2 mg or 5 mg QD SCD (HbSS or HbS-β0 thal) 4 weeks (core); 2 years Safety; pharmacokinetics and (extension) pharmacodynamics; Hb response; haemolytic and erythropoietic markers NCT06924970 Phase 2, double-blind, 2·5 mg, 5 mg, or 7 mg SCD (HbSS, HbSC, HbS-β0 thal or 12 weeks (core); 52 weeks Hb response; haemolytic and randomised, placebo- QD other syndrome) (extension) erythropoietic markers; patient- controlled reported outcomes; safety NCT05490446 Phase 2, open-label, single- 5 mg QD Lower-risk MDS* 16 weeks (core); 156 weeks Hb response; transfusion arm (phase 2A) (extension) independence; transfusion reduction response; safety; pharmacokinetics and pharmacodynamics NCT05490446 Phase 2, open-label 10 mg, 15 mg, or 20 mg Lower-risk MDS* 24 weeks (core); 156 weeks Transfusion reduction response; (phase 2B) QD (extension) Hb response; safety; pharmacokinetics and pharmacodynamics Safety measured as number and severity of treatment-emergent adverse events. BID=twice daily. PKD=pyruvate kinase deficiency. Hb=haemoglobin. BMD=bone mineral density. Thal=thalassaemia. SCD=sickle cell disease. RBC=red blood cell. CDA II=congenital dyserythropoietic anaemia type 2. QD=once daily. VOC=vaso-occlusive crisis. SAD=single ascending dose. MAD=multiple ascending dose. MDS=myelodysplastic syndrome. *Lower-risk MDS defined as Revised International Prognostic Scoring System risk score ≤3·5 and <5% blasts. Table 3: Ongoing clinical trials without completed and published core period results Thalassaemia trials in thalassaemia, mitapivat improved haemolytic, Thalassaemia is an inherited haemolytic anaemia erythropoietic, and patient-reported outcomes, while characterised by impaired globin chain synthesis, iron markers were largely unchanged or unreported, causing imbalance between α-globin and β-globin chains underscoring the potential clinical benefit of PK in red blood cells. The precipitation of excess unpaired activators in thalassaemia. globin chains leads to oxidative stress and subsequent ineective erythropoiesis, haemolysis, and anaemia.34 To Sickle cell disease clear excess unpaired globin chains, thalassaemic red Sickle cell disease results from a single nucleotide point blood cells require more ATP but, paradoxically, have mutation in the β-globin gene that produces mutated lower ATP levels.72,73 Oxidative stress in thalassaemia is sickle haemoglobin, which polymerises upon thought to inhibit PK activity by oxidising cysteine deoxygenation.1 Polymerisation of HbS distorts red blood residues of PK.74,75 In thalassaemia, PK activators address cells to the characteristic sickle shape, increasing their both ineective erythropoiesis and haemolysis. An open- fragility and causing haemolytic anaemia, while label phase 2 clinical trial in α and β non-transfusion promoting microvascular obstruction that underlies dependent thalassaemia (NTDT) evaluated the safety and painful vaso-occlusive events. Red blood cells in sickle cell ecacy of mitapivat.8 16 (80%) of 20 participants across a disease are marked by reduced ATP levels, increased wide spectrum of genotypes reached the primary 2,3-DPG levels, with reduced oxygen anity causing early endpoint, a haemoglobin increase of at least 1·0 g/dL. deoxygenation.6,15,77 The observed glycolytic disturbances in Two randomised phase 3 trials, ENERGIZE and sickle cell disease might result from PK dysfunction.6 ENERGIZE-T, were subsequently initiated to evaluate These metabolic changes are associated with increased ecacy in NTDT and transfusion-dependent risk of polymerisation and poor outcomes.15,78,79 Increased thalassaemia, respectively.76,62 In ENERGIZE, haemo- sickling and sickle cell disease-like phenotypes have been globin responses of at least 1·0 g/dL were observed in reported in individuals with sickle cell trait and 55 (42%) of 130 patients treated with mitapivat versus co-inherited PK deficiency, supporting the hypothesis that 1 (2%) of 64 patients treated with placebo.62 These PK activation could ameliorate sickling in this disease.80,81 improvements were observed in both α-NTDT and PK activators exert a dual eect in sickle cell disease by β-NTDT, addressing a substantial unmet therapeutic replenishing ATP and increasing haemoglobin–oxygen need, especially in α-thalassaemia, for which no approved anity. Mitapivat was evaluated in a phase 1, single-arm, treatments are currently available. Although the open-label dose-escalation study, in which ENERGIZE-T study results have yet to be published, 9 of 16 participants had a haemoglobin response of at least preliminary findings indicate that mitapivat might 1·0 g/dL, along with reductions in haemolytic markers decrease transfusion burden.76 In both phase 2 and 3 and reticulocyte count.63 The investigator-initiated, Therapeutics single-arm phase 2 ESTIMATE study evaluated mitapivat spherocytosis, hereditary elliptocytosis, and hereditary in ten adults with sickle cell disease.65 The primary xerocytosis.4,5 In hereditary spherocytosis, PK deficiency endpoint, change in point of sickling, decreased after likely reflects loss of membrane-associated glycolytic 8 weeks. Decreases in 2,3-DPG and increased proteins as a result of membrane vesiculation.4 Although haemoglobin–oxygen anity shifted the oxygen PK activation does not correct the membrane defect, it dissociation curve towards normal. A haemoglobin improves red-cell rheology ex vivo irrespective of response occurred in five of nine evaluable participants, splenectomy status, supporting ongoing clinical trials.52 with parallel reductions in reticulocytes and haemolytic Following these observations, the investigator-initiated markers. In subsequent extensions of mentioned studies phase 2 SATISFY trial evaluated mitapivat in hereditary with a median follow-up of 132 weeks and 156 weeks, spherocytosis, hereditary xerocytosis, and congenital these improvements were sustained.64,66 Although dyserythropoietic anaemia type II.85 Although results are exploratory and based on a small sample, the annualised not yet published, early data suggest improved rate of vaso-occlusive events in the ESTIMATE declined. haemoglobin, haemolytic markers, and patient-reported This endpoint is being assessed in ongoing phase 3 trials. outcomes, particularly in hereditary spherocytosis. RISE UP was a phase 2/3, double-blind, randomised, placebo-controlled trial of mitapivat in adults with sickle Myelodysplastic syndrome cell disease. In the phase 2 part of this study, the primary Myelodysplastic syndrome is an acquired disorder ecacy endpoint, a haemoglobin response of at least characterised by variable cytopenias, including anaemia 1·0 g/dL, was reached by 12 (46%) of 26 participants due to ineective erythropoiesis, and an increased risk of receiving 50 mg mitapivat twice daily and 13 (50%) of 26 progression to acute myeloid leukaemia. Myelodysplastic receiving 100 mg mitapivat twice daily, compared with syndrome has been associated with impaired glycolytic 1 (4%) of 27 receiving placebo. Haemolytic markers, activity in red blood cells, which could be improved upon reticulocytes, erythropoietin, and health-related quality of ex vivo treatment with PK activators.86 A phase 2a/2b life also improved in both dosage groups. Although not clinical trial investigating the safety and ecacy of powered for vaso-occlusive crises, annualised pain crises tebapivat in lower-risk myelodysplastic syndrome (Revised were 52–70% lower with mitapivat than with placebo.67 International Prognostic Scoring System score ≤3·5 and These findings support continued evaluation of 100 mg <5% blasts) is ongoing.87 Etavopivat has also been twice daily in the phase 3 trial. investigated for the treatment of myelodysplastic syndrome Etavopivat has also been evaluated in sickle cell disease. in an open-label phase 2 study, but the trial was terminated In a randomised, placebo-controlled, phase 1 study, a after enrolment of 17 out of 45 planned patients, as a futility haemoglobin response of at least 1·0 g/dL was reached in assessment indicated a low likelihood of clinical benefit.88 11 of 15 participants receiving etavopivat, along with improvements in ATP, 2,3-DPG, haemolytic markers, p50, Safety and tolerability point of sickling, and cellular deformability.68 The ongoing During the decade in which PK activators, mainly phase 2/3 HIBISCUS trial is evaluating etavopivat in mitapivat, have been evaluated in humans, some potential adults with sickle cell disease in a randomised, placebo- safety risks have been identified. However, available data controlled, double-blind setting.82 Although data have yet suggest that PK activators are generally well tolerated, and to be published, initial findings indicate a possible the reported adverse events are mostly mild, transient, and reduction in vaso-occlusive event rates. manageable with dose modifications or supportive Tebapivat has been evaluated in a phase 1, open-label interventions. The reported discontinuation rates in study in adults with sickle cell disease. The complete trial clinical trials across all diseases are low. The most common results have not been published yet, but early findings reported treatment-emergent adverse events are headache, suggest improvements in haemoglobin and haemolytic insomnia, and nausea. Other frequently reported markers in both dosage groups (2 mg and 5 mg).83 treatment-emergent adverse events included liver enzyme Collectively, PK activators in sickle cell disease show increase, dizziness, fatigue, sex hormone changes, and improvements in haemoglobin, haemolytic and upper respiratory infections, while vaso-occlusive crises erythropoietic markers, health-related quality of life, and were reported in sickle cell disease (table 2). vaso-occlusive event rate, suggesting a potential clinical Preclinical and early-phase clinical trials showed that benefit in this patient population. mitapivat is an inhibitor of the aromatase enzyme. This is important because aromatase inhibition might cause Red blood cell membrane disorders hormone changes and reduce bone mineral density, and Red blood cell membrane disorders arise from genetic osteopenia and osteoporosis are more prevalent in defects in cytoskeletal, membrane and transmembrane, patients with haemolytic disorders.89 Adult trials have and ion-channel proteins and are characterised by reported changes in sex hormones, albeit in most cases, haemolysis due to reduced deformability and subsequent not clinically significant.58,64 These changes were reversible splenic entrapment.84 Glycolytic impairment is also and did not lead to a significant decrease in bone mineral observed, with reduced PK activity in hereditary density, even after long-term treatment with mitapivat.89,90 1392 Therapeutics Two patients with PK deficiency developed fractures after Despite several identified potential risks, the available mitapivat initiation, one with prior L4 compression data support an acceptable safety profile for PK activators fracture and long-term steroid use.59,91 Four traumatic in the studied populations. Ongoing data collection will single-digit fractures were reported in patients with sickle clarify which side-eects are class related. Given the cell disease, mostly early after treatment start.64 These potential for lifelong use, long-term monitoring and findings emphasise the importance of continued individualised risk-benefit assessment remain essential. assessment of bone mineral density.59,91 Aromatase Importantly, there are currently little long-term safety data. inhibition is also an important consideration in treatment of children, given potential eects on growth and pubertal Future directions development. This is being carefully examined in clinical Many other red blood cell enzyme disorders could benefit trials of children with PK deficiency treated with from PK activation due to enhancement of glycolytic flux mitapivat.70,71 A phase 1 clinical ascending-dose study and restoration of metabolic and antioxidative evaluating etavopivat found no aromatase inhibition.42 homeostasis. A case report of a patient with In the early phase of the DRIVE-PK study, two patients phosphofructokinase deficiency described symptom developed acute haemolysis after abrupt discontinuation improvement of muscle disease and improvements in of mitapivat.58 After this occurrence, dose taper regimens haemoglobin following mitapivat treatment, supporting were implemented in this trial and subsequent clinical further exploration in other red cell enzymopathies, such trials. No events of acute haemolysis have been reported as glucose-6-phosphate isomerase deficiency.97 Ongoing with dose decreases or discontinuing the medication trials of PK activators in haematological conditions, such with the implementation of these regimens. as myelodysplastic syndrome, are expected to provide Hepatocellular injury was reported in patients with important insights that might support expanding their thalassaemia treated with mitapivat. This occurred use to other hypoproliferative anaemias or bone marrow within the first 6 months of exposure. After treatment failure syndromes, such as Diamond-Blackfan anaemia.87 discontinuation, liver enzymes normalised. Hepat- Ongoing evaluation in the paediatric population is ocellular injury was therefore included as a potentially important, as early initiation of treatment might prevent important risk, and prescribing information was updated the development of long-term complications associated to include monthly liver enzyme monitoring during the with haemolysis, blood transfusions, and iron overload. first 6 months of treatment.92 Most importantly, eective symptom management is The DRIVE-PK and ACTIVATE studies reported grade 3 crucial given the substantial disease burden during or higher events of hypertriglyceridaemia in childhood, and this could prevent unnecessary three (6%) of 52 and in two (5%) of 40 participants, splenectomy and its associated complications and risks. respectively.58,59 The ACTIVATE-T study also reported Although mitapivat shows ecacy across a wide range two occurrences, one of which was considered a grade 4 of PKLR genotypes in patients with PK deficiency, most serious adverse event.60 Screening for triglyceride increases do not respond or only modestly.58–60 Non-responders are should therefore be considered, and the long-term risk of often patients with minimal residual enzyme. This cardiovascular disease should be weighed against the underscores the need for alternative therapeutic benefits of mitapivat treatment in those patients with strategies, including the development of next-generation hypertriglyceridaemia. PK activators with ecacy in patients with severely Concerns have been raised that drugs increasing impaired PK function. haemoglobin–oxygen anity could impair tissue oxygen Next-generation PK activators with high PKR and PKL delivery.93,94 In sickle cell disease, voxelotor markedly limits selectivity, such as etavopivat, might prevent potential o- oxygen release by stabilising the non-polymerising form of target, isoenzyme-related eects.38 However, o-target HbS. In contrast, PK activators lower 2,3-DPG, causing PKM2 activation resulting in side-eects has not been only a mild left shift of the oxygen–dissociation curve, investigated or reported. As PKL is more than while maintaining oxygen release and exerting anti- 95% homologous to PKR and selectivity for PKR over PKL sickling eects.95 Moreover, fetal haemoglobin (HbF) is is not tested, it remains unclear whether mitapivat’s side- less sensitive to 2,3-DPG mediated modulation of oxygen eects will also emerge with etavopivat. Whether the anity than adult haemoglobin, as γ-globin binds 2,3-DPG improved pharmacodynamic and pharmacokinetic more weakly, which is expected to attenuate the eect of properties of next-generation PK activators, such as 2,3-DPG changes in patients with high HbF proportions.96 tebapivat, can improve outcomes has yet to be investigated.39 In the RISE UP study, this shift did not seem substantial The rarity of many red blood cell disorders limits the enough to impair tissue oxygen delivery, as indicated by feasibility of studying PK activation in clinical trials, the absence of increased erythropoietin concentrations in while a substantial unmet therapeutic need remains. either mitapivat group.67 Neurological safety signals have Continued evaluation through real-world data and basket not been reported to date, and an ongoing study trials involving cohorts with multiple rare anaemias (NCT05725902) is evaluating cerebral oxygen metabolism should be encouraged, as these could improve our in patients with sickle cell disease receiving etavopivat. understanding of disease biology, provide further Therapeutics insights into the potential of PK activation, and expand 5 Rab MAE, van Oirschot BA, van Straaten S, et al. Decreased activity the possibilities for targeted treatments in these ultra- and stability of pyruvate kinase in hereditary hemolytic anemia: a potential target for therapy by AG-348 (mitapivat), an allosteric rare haematological disorders. activator of red blood cell pyruvate kinase. Blood 2019; 134 (suppl 1): 3506. Conclusions 6 Rab MAE, Bos J, van Oirschot BA, et al. Decreased activity and stability of pyruvate kinase in sickle cell disease: a novel target for PK activators represent a novel, oral, and generally well mitapivat therapy. Blood 2021; 137: 2997–3001. tolerated therapeutic approach for hereditary haemolytic 7 van Dijk MJ, Rab MAE, van Oirschot BA, et al. One-year safety and anaemias, oering a mechanism-based alternative to ecacy of mitapivat in sickle cell disease: follow-up results of a phase 2, open-label study. Blood Adv 2023; 7: 7539–50. supportive care. Clinical trials have shown meaningful 8 Kuo KHM, Layton DM, Lal A, et al. Safety and ecacy of mitapivat, improvements in key disease markers, with potential an oral pyruvate kinase activator, in adults with non-transfusion benefits in reducing complications and improving quality dependent α-thalassaemia or β-thalassaemia: an open-label, of life. An expanding number of red blood cell disorders multicentre, phase 2 study. Lancet 2022; 400: 493–501. 9 Doeven T, Van Beers EJ, van Wijk R, et al. Satisfy: a EuroBloodNet could benefit from PK activation, supported by preclinical multicenter, single-arm phase 2 trial of mitapivat in adult patients research suggesting a role of glycolytic disturbances in with erythrocyte membranopathies and congenital their pathophysiology. Early results of PK activation in dyserythropoietic anemia type II - results from the 8-week dose- escalation period. Blood 2024; 144 (suppl 1): 3831. children with PK deficiency suggest a favourable safety 10 van Wijk R, van Solinge WW. 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Hemasphere 2025; 9: 462–63. 1396 --- [PDF原文](https://sci-net.xyz/storage/7932541/ff2e5cfef9b9501c28d30297257f0c952e57d477debbda0cd964ff6407bd7fea/Pyruvate-kinase-activators-in-hereditary-haemolytic-anaemias-current-evidence-and-clinical.pdf) DOI: 10.1016/S0140-6736(26)00150-9