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Background: Pyruvate kinase (PK) deficiency is an inherited red blood cell (RBC) enzyme disorder that results in non-immune chronic hemolytic anemia. Characteristic symptoms of PK deficiency include anemia, fatigue, splenomegaly, jaundice, gallstones, thrombosis, and transfusional iron overload. Previously, treatments aimed at symptomatic management with RBC transfusions, phototherapy, folic acid supplementation, splenectomy, and iron chelation therapy when iron overload was documented. Mitapivat, a recently approved medication for treatment of PK-deficiency hemolytic anemia, is an oral allosteric activator of wild-type and mutant RBC PK enzymes. In this paper, we describe three cases of PK-deficiency anemia treated with mitapivat and describe modern management of this rare hemolytic disorder. Methods: A retrospective healthcare database analysis was conducted to extract relevant information. Both quantitative and qualitative methods were integrated to provide a more comprehensive understanding of the cases. Results: Two patients responded well to treatment with mitapivat, noted by an increase in hemoglobin levels, improvements in hemolytic markers, less frequent or no RBC transfusion requirements, and improvements in fatigue. One patient carrying two non-missense mutations of the PKLR gene did not respond to treatment with mitapivat. As variations in patient-specific factors (including genotype) can lead to different clinical manifestations and responses to treatment, we recommend considering both the phenotype (clinical symptoms and signs) and the genotype of the PKLR gene when making therapeutic decisions about starting a patient on mitapivat. Conclusions: While mitapivat addresses the previously unmet needs of most patients with PK deficiency as the first and only disease-modifying medication to receive approval for this condition, not all patients with PK deficiency are amenable to treatment with mitapivat. Full article

Pyruvate kinase (PK) deficiency is a rare genetic disorder that affects this critical enzyme within the glycolysis pathway. In recent years, Mitapivat (MTPV, AG-348) has emerged as a notable allosteric activator for treating PK deficiency. However, the allosteric regulatory effects exerted on PK by MTPV are yet to be comprehensively elucidated. To shed light on the molecular mechanisms of the allosteric effects, we employed crystallography and biophysical methods. Our efforts yielded a high-resolution crystal structure of the PK tetramer complexed with MTPV at 2.1 Å resolution. Isothermal titration calorimetry measurements revealed that MTPV binds to human PK with an affinity of 1 μM. The enhanced structural details now allow for unambiguous analysis of the MTPV-filled cavity intricately embedded within the enzyme. Finally, the structure suggests that MTPV binding induces an allosteric effect on the B-domain situated proximal to the active site. In summary, our study provides valuable insights into the allosteric regulation of PK by MTPV and paves the way for further structure-based drug optimization for therapeutic interventions in PK deficiency. Full article

This review was performed to determine the potential of drugs that can remove or decrease the requirements for blood transfusion among beta (β)-thalassemia patients. A comprehensive literature search was conducted to identify clinical trials and studies using PubMed Central, Google Scholar, PubMed, and ScienceDirect archived articles published from 1996 to November 2023. According to this review, clinical trials for a number of drugs, including luspatercept, sotatercept, mitapivat, etavopivat, hydroxyurea, rapamycin, decitabine, thalidomide, and quercetin, have been performed as part of efforts to improve the cure strategy for β-thalassemia. Of these drugs, luspatercept and sotatercept have exhibited particularly promising results and have been granted US Food and Drug Administration (FDA) approval for use in β-thalassemia patients. The mode of action for the drugs luspatercept and sotatercept involves the stimulation of hemoglobin (Hb) production or enhancement of its functionality, thereby decreasing reliance on blood transfusions and enhancing the overall quality of life. In this way, drugs like luspatercept and sotatercept present an opportunity to notably decrease the necessity for blood transfusions in β-thalassemia patients, improving their standard of living and overall prognosis. However, more research is needed to evaluate the effectiveness and safety of these drugs in the long run. Full article