Iron chelation therapy for children with transfusion-dependent ß-thalassemia: How young is too young?

In this review, we provide a summary of evidence on iron overload in young children with transfusion-dependent ß-thalassemia (TDT) and explore the ideal timing for intervention. Key data from clinical trials and observational studies of the three available iron chelators deferoxamine, deferiprone, and deferasirox are also evaluated for inclusion of subsets of young children, especially those less than 6 years of age. Evidence on the efficacy and safety of iron chelation therapy for children ≥2 years of age with transfusional iron overload is widely available. New data exploring the risks and benefits of early-start iron chelation in younger patients with minimal iron overload are also emerging.

Clinically meaningful improvements in patient-reported outcomes in mitapivat-treated patients with pyruvate kinase deficiency.

Clinically meaningful benefits in the signs, symptoms, and impacts of #PKDeficiency as assessed by disease-specific patient-reported outcome measures were observed in mitapivat-treated adult patients in two phase 3 clinical trials.

Diagnosis and management of pyruvate kinase deficiency: international expert guidelines.

Pyruvate kinase (PK) deficiency is the most common cause of chronic congenital non-spherocytic haemolytic anaemia worldwide, with an estimated prevalence of one in 100 000 to one in 300 000 people. PK deficiency results in chronic haemolytic anaemia, with wide ranging and serious consequences affecting health, quality of life, and mortality. The goal of the International Guidelines for the Diagnosis and Management of Pyruvate Kinase Deficiency was to develop evidence-based guidelines for the clinical care of patients with PK deficiency. These clinical guidelines were developed by use of GRADE methodology and the AGREE II framework. Experts were invited after consideration of area of expertise, scholarly contributions in PK deficiency, and country of practice for global representation. The expert panel included 29 expert physicians (including adult and paediatric haematologists and other subspecialists), geneticists, laboratory specialists, nurses, a guidelines methodologist, patients with PK deficiency, and caregivers from ten countries. Five key topic areas were identified, the panel prioritised key questions, and a systematic literature search was done to generate evidence summaries that were used in the development of draft recommendations. The expert panel then met in person to finalise and vote on recommendations according to a structured consensus procedure. Agreement of greater than or equal to 67% among the expert panel was required for inclusion of a recommendation in the final guideline. The expert panel agreed on 31 total recommendations across five key topics: diagnosis and genetics, monitoring and management of chronic complications, standard management of anaemia, targeted and advanced therapies, and special populations. These new guidelines should facilitate best practices and evidence-based PK deficiency care into clinical practice.

Mitapivat improves ineffective erythropoiesis and iron overload in adult patients with pyruvate kinase deficiency.

ABSTRACT: Pyruvate kinase (PK) deficiency is a rare, hereditary disease characterized by chronic hemolytic anemia. Iron overload is a common complication regardless of age, genotype, or transfusion history. Mitapivat, an oral, allosteric PK activator, improves anemia and hemolysis in adult patients with PK deficiency. Mitapivat's impact on iron overload and ineffective erythropoiesis was evaluated in adults with PK deficiency who were not regularly transfused in the phase 3 ACTIVATE trial and long-term extension (LTE) (#NCT03548220/#NCT03853798). Patients in the LTE received mitapivat throughout ACTIVATE/LTE (baseline to week 96; mitapivat-to-mitapivat [M/M] arm) or switched from placebo (baseline to week 24) to mitapivat (week 24 to week 96; placebo-to-mitapivat [P/M] arm). Changes from baseline in markers of iron overload and erythropoiesis were assessed to week 96. Improvements in hepcidin (mean, 4770.0 ng/L; 95% confidence interval [CI], -1532.3 to 11 072.3), erythroferrone (mean, -9834.9 ng/L; 95% CI, -14 328.4 to -5341.3), soluble transferrin receptor (mean, -56.0 nmol/L; 95% CI, -84.8 to -27.2), and erythropoietin (mean, -32.85 IU/L; 95% CI, -54.65 to -11.06) were observed in the M/M arm (n = 40) from baseline to week 24, sustained to week 96. No improvements were observed in the P/M arm (n = 40) to week 24; however, upon transitioning to mitapivat, improvements similar to those observed in the M/M arm were seen. Mean changes from baseline in liver iron concentration by magnetic resonance imaging at week 96 in the M/M arm and the P/M arm were -2.0 mg Fe/g dry weight (dw; 95% CI, -4.8 to -0.8) and -1.8 mg Fe/g dw (95% CI, -4.4 to 0.80), respectively. Mitapivat is the first disease-modifying pharmacotherapy shown to have beneficial effects on iron overload and ineffective erythropoiesis in patients with PK deficiency. This trial was registered at www.ClinicalTrials.gov as #NCT03548220 (ACTIVATE) and #NCT03853798 (LTE).

Αlpha-thalassemia: A practical overview.

α-Thalassemia is an inherited blood disorder characterized by decreased synthesis of α-globin chains that results in an imbalance of α and ß globin and thus varying degrees of ineffective erythropoiesis, decreased red blood cell (RBC) survival, chronic hemolytic anemia, and subsequent comorbidities. Clinical presentation varies depending on the genotype, ranging from a silent or mild carrier state to severe, transfusion-dependent or lethal disease. Management of patients with α-thalassemia is primarily supportive, addressing either symptoms (eg, RBC transfusions for anemia), complications of the disease, or its transfusion-dependence (eg, chelation therapy for iron overload). Several novel therapies are also in development, including curative gene manipulation techniques and disease modifying agents that target ineffective erythropoiesis and chronic hemolytic anemia. This review of α-thalassemia and its various manifestations provides practical information for clinicians who practice beyond those regions where it is found with high frequency.

Pregnancy outcomes and iron status in ß-thalassemia major and intermedia: a systematic review and meta-analysis.

ABSTRACT: Advancements in orally bioavailable iron chelators and MRI methods have improved life expectancy and reproductive potential in thalassemia major (TM) and thalassemia intermedia (TI). Pregnancy is associated with adverse maternal and neonatal outcomes, frequency of which has not been well delineated. This systematic review aims to provide risk estimates of maternal and fetal outcomes in TM and TI and explore pregnancy's impact on iron homeostasis. Fifteen studies (429 participants, 684 pregnancies) were included. Meta-analysis revealed a higher thrombosis risk in TI (3.7%) compared to TM (0.92%), unchanged from prepregnancy. Heart failure risks in the earlier years appeared similar (TM 1.6% vs TI 1.1%), and maternal mortality in TM was 3.7%, but with current management, these risks are rare. Gestational diabetes and pre-eclampsia occurred in 3.9% and 11.3% of TM pregnancies, respectively. Caesarean section rates were 83.9% in TM and 67% in TI. No significant difference in stillbirth, small for gestational age neonates, or preterm birth incidence between TM and TI was observed. In TM pregnancies, red cell requirements significantly increased (from 102 to 139 ml/kg/year, P = 0.001), and 70% of TI pregnancies required blood transfusions. As expected, increased transfusion alongside chelation cessation led to a significant increase in serum ferritin during pregnancy (TM by 1005 ng/mL; TI by 332 ng/mL, P < 0.0001). Deterioration in iron status was further reflected by an increase in liver iron concentration (from 4.6 to 11.9 mg/g dry weight, P < 0.0001), and myocardial T2-star (T2∗) magnetic resonance imaging decreased (from 36.2 ± 2.5 ms to 31.1 ms) during pregnancy. These findings emphasize the elevated maternal risk of iron-related cardiomyopathy during pregnancy and labor, stressing the importance of cardiac monitoring and postpartum chelation therapy resumption.

THromboprophylaxis In Sickle Cell Disease with central venous catheters (THIS): an internal pilot randomised controlled trial protocol.

INTRODUCTION: Individuals with sickle cell disease (SCD) and central venous catheters (CVC) are at high risk for venous thromboembolism (VTE). Minimal data exist regarding the use of anticoagulation as thromboprophylaxis of VTE in this demographic, and as a result, clinical equipoise exists. Prophylactic dose rivaroxaban, a direct oral anticoagulant, is efficacious and safe as thromboprophylaxis in other demographics, and may be an optimal agent in SCD with CVC. Prior to conducting a full clinical trial to assess rivaroxaban as thromboprophylaxis in SCD with CVC, a pilot study is needed to gauge its feasibility. METHODS AND ANALYSIS: THromboprophylaxis In Sickle Cell Disease pilot trial is an investigator-initiated, multicentre, double-blinded, randomised controlled trial (RCT) assessing if it is feasible and safe to conduct an adequately powered RCT comparing rivaroxaban to matching placebo as thromboprophylaxis in those with SCD and CVC. Fifty adult patients with SCD and CVC will be randomised to receive either rivaroxaban 10 mg daily or matching placebo for the duration of the CVC in situ for up to 1 year. After randomisation, follow-up visits will occur every 3 months. The primary outcomes pertain to the feasibility of a full trial and include numbers of eligible and recruited participants. Exploratory outcomes include overall incidence of VTE and bleeding complications, as well as quality of life. If the full trial is feasible, blinding will be maintained and patients in the pilot study will be included in the full trial. ETHICS AND DISSEMINATION: The trial was initially approved by the University Health Network Research Ethics Board (REB) in Toronto, Canada. All sites will obtain approval from their respective REB prior to commencement of study activities. Study results will be disseminated through presentations at medical conferences and peer-reviewed publications. TRIAL REGISTRATION NUMBER: NCT05033314.

Blood pressure thresholds for the diagnosis of hypertensive disorders of pregnancy in sickle cell disease.

In this retrospective cohort study of singleton pregnancies in people with sickle cell disease (SCD) delivered at two academic centres between 1990 and 2021, we collected demographic and SCD-related data, pregnancy outcomes, and the highest systolic and diastolic blood pressure (SBP and DBP) at seven time periods. We compared the characteristics of subjects with new or worsening proteinuria (NWP) during pregnancy to those without. We then constructed receiver operating characteristic (ROC) curves to determine the blood pressure (BP) that best identifies those with NWP. The SBP or DBP thresholds which maximized sensitivity and specificity were 120 mmHg SBP (sensitivity: 55.2%, specificity: 73.5%) and 70 mmHg DBP (sensitivity: 27.6%, specificity: 67.7%). The existing BP threshold of 140/90 mmHg lacked sensitivity in both genotype groups (HbSS/HbSß0 : SBP = 21% sensitive, DBP = 5.3% sensitive; HbSS/HbSß+ : SBP = 10% sensitive, DBP = 0% sensitive). Finally, percent change in SBP, DBP and MAP were all poor tests for identifying NWP. Existing BP thresholds used to diagnose hypertensive disorders of pregnancy (HDP) are not sensitive for pregnant people with SCD. For this population, lowering the BP threshold that defines HDP may improve identification of those who need increased observation, consideration of early delivery and eclampsia prophylaxis.

Natural history of blood pressure in sickle cell disease pregnancy.

In this retrospective cohort study of singleton pregnancies in people with sickle cell disease (SCD) delivered at two academic centres between 1990 and 2021, we collected demographic and SCD-related data, pregnancy outcomes, and the highest systolic and diastolic blood pressure (SBP and DBP) at seven time periods. We compared blood pressure values and trajectories in the composite cohort and in each genotype group to control values in a non-SCD pregnancy dataset. There were 290 pregnancies among 197 patients with SCD. Sixteen per cent (n = 47) of pregnancies had a hypertensive disorder of pregnancy (HDP); the rates did not differ by genotype. The mean SBP and DBP were lower in the HbSS/HbSß0 group than in the non-SCD control group at all timepoints. Mean SBP and DBP trajectories were similar between the HbSS/HbSß0 group and non-SCD controls, whereas the mean SBP and DBP in the HbSC/HbSß+ group decreased between the first and second trimesters and plateaued between the second and third trimesters. There were no differences in blood pressure trajectory by haemoglobin >/< 10 gm/dL or by chronic transfusion status. Overall, pregnant people with SCD have lower blood pressure than unaffected pregnant people, raising the possibility that HDP are underdiagnosed, particularly in people with HbSS/HbSß0 .

Pyruvate kinase activators: targeting red cell metabolism in thalassemia.

Thalassemia is an inherited red blood cell disorder whereby the qualitative and/or quantitative imbalance in α- to ß-globin ratio results in hemolysis and ineffective erythropoiesis. Oxidative stress, from the precipitated excess globin and free iron, is a major factor that drives hemolysis and ineffective erythropoiesis. Pyruvate kinase activity and adenosine triphosphate availability are reduced due to the overwhelmed cellular antioxidant system from the excessive oxidative stress. Mitapivat, a pyruvate kinase activator in development as a treatment for thalassemia, was shown to increase hemoglobin and reduce hemolysis in a small phase 2 single-arm trial of patients with α- and ß-thalassemia. The ongoing phase 3 studies with mitapivat and the phase 2 study with etavopivat will examine the role of pyruvate kinase activators as disease modifying agents in thalassemia.

Screening for cognitive impairment in adults with sickle cell disease: A systematic review and meta-analysis.

Neurovascular disease such as symptomatic stroke, silent brain infarcts and vascular cognitive impairment are common complications of sickle cell disease (SCD) that can have devastating consequences on quality of life, employment, and social functioning.  Early recognition of neurovascular disease is a prerequisite for the timely optimization of medical care and to connect patients to adaptive resources. While cognitive impairment has been well described in children, currently available data are limited in adults. As a result, guidance on the optimal cognitive screening strategies in adults is scarce. We conducted a systematic review to identify the different screening tools that have been evaluated in SCD. A meta-analysis was performed to estimate the prevalence of suspected cognitive impairment in this population. In this qualitative synthesis, we present 8 studies that evaluated 6 different screening tools. Patient characteristics that impacted on cognitive screening performance included age, education level, and a prior history of stroke. We report a pooled prevalence of 38% [14-62%] of suspected cognitive impairment. We discuss the relative benefits and limitations of the different screening tools to help clinicians select an adapted approach tailored to their specific patients' needs. Further studies are needed to establish and validate cognitive screening strategies in patients with diverse cultural and educational backgrounds.

Activation of pyruvate kinase as therapeutic option for rare hemolytic anemias: Shedding new light on an old enzyme.

Novel developments in therapies for various hereditary hemolytic anemias reflect the pivotal role of pyruvate kinase (PK), a key enzyme of glycolysis, in red blood cell (RBC) health. Without PK catalyzing one of the final steps of the Embden-Meyerhof pathway, there is no net yield of adenosine triphosphate (ATP) during glycolysis, the sole source of energy production required for proper RBC function and survival. In hereditary hemolytic anemias, RBC health is compromised and therefore lifespan is shortened. Although our knowledge on glycolysis in general and PK function in particular is solid, recent advances in genetic, molecular, biochemical, and metabolic aspects of hereditary anemias have improved our understanding of these diseases. These advances provide a rationale for targeting PK as therapeutic option in hereditary hemolytic anemias other than PK deficiency. This review summarizes the knowledge, rationale, (pre)clinical trials, and future advances of PK activators for this important group of rare diseases.

Characterizing the process of urgent referrals and transfers to a large tertiary care apheresis centre in Ontario: A retrospective database review.

BACKGROUND: Therapeutic plasma exchange (TPE) and red blood cell exchange (RBCX) are life-saving apheresis procedures offered in 7 Ontario hospitals. Most referrals are directed by CritiCall Ontario (CritiCall), a 24/7 service funded by the Ontario Ministry of Health and Long-Term Care. We used CritiCall data to examine referral requests, acceptances, and transfers for urgent apheresis to our centre. METHODS: Retrospective CritiCall referral and transfer data for urgent apheresis between October 2013 and December 2018 were included. Continuous variables were analyzed by linear regression. Categorical variables were analyzed using nonparametric tests. RESULTS: Eighty-five cases (52 TPE, 33 RBCX) were identified. Median patient age was 52 years (interquartile range [IQR] 32) for TPE, 29 years (IQR 18) for RBCX. Most patients (58%) were female. Total time from referral to arrival at our centre was 243 (IQR 166) minutes. The greatest proportion of this total was from patient acceptance to arrival (169 [IQR 112] minutes). Median distance between referring and accepting centres was 39 (IQR 30) kilometres, with ground transportation used most often. Multiple linear regression examining factors that contribute to total time demonstrated that the number of physicians contacted prior to patient acceptance and inter-hospital distance were independently associated (p = 0.007 and p = 0.048, respectively). INTERPRETATION: Addressing modifiable factors to reduce time is important given that time to initiate treatment is associated with better outcomes. Quality improvement strategies should be aimed at coordinated provincial resource sharing, pairing referrals with nearest available apheresis centres, and creating efficiency in the interval between patient acceptance and arrival.

Profile of Luspatercept in the Treatment of Anemia in Adults with Non-Transfusion-Dependent ß-Thalassemia (NTDT): Design, Development and Potential Place in Therapy.

Over the past decade, evidence has been mounting on the detrimental clinical sequelae of untreated anemia in patients with non-transfusion-dependent ß-thalassemia (NTDT). There are no pharmacologic agents that are specifically approved for the management of anemia in NTDT, and available options such as splenectomy, transfusion therapy, and hydroxyurea each come with their own shortcomings, especially for long-term use. Luspatercept is an erythroid maturation agent that has been evaluated in a Phase 2, randomized trial and showed a significant benefit in raising hemoglobin level by at least 1 g/dL in adults with NTDT and a baseline hemoglobin level ≤10 g/dL. These data led to luspatercept's approval by the European Commission for the treatment of anemia in adults with NTDT and presents the first evidence-based approach for a novel agent that is able to ameliorate anemia in this patient population.

Investigating the association between fasting insulin, erythrocytosis and HbA1c through Mendelian randomization and observational analyses.

Background: Insulin resistance (IR) with associated compensatory hyperinsulinemia (HI) are early abnormalities in the etiology of prediabetes (preT2D) and type 2 diabetes (T2D). IR and HI also associate with increased erythrocytosis. Hemoglobin A1c (HbA1c) is commonly used to diagnose and monitor preT2D and T2D, but can be influenced by erythrocytosis independent of glycemia. Methods: We undertook bidirectional Mendelian randomization (MR) in individuals of European ancestry to investigate potential causal associations between increased fasting insulin adjusted for BMI (FI), erythrocytosis and its non-glycemic impact on HbA1c. We investigated the association between the triglyceride-glucose index (TGI), a surrogate measure of IR and HI, and glycation gap (difference between measured HbA1c and predicted HbA1c derived from linear regression of fasting glucose) in people with normoglycemia and preT2D. Results: Inverse variance weighted MR (IVWMR) suggested that increased FI increases hemoglobin (Hb, b=0.54 ± 0.09, p=2.7 x 10-10), red cell count (RCC, b=0.54 ± 0.12, p=5.38x10-6) and reticulocyte (RETIC, b=0.70 ± 0.15, p=2.18x10-6). Multivariable MR indicated that increased FI did not impact HbA1c (b=0.23 ± 0.16, p=0.162) but reduced HbA1c after adjustment for T2D (b=0.31 ± 0.13, p=0.016). Increased Hb (b=0.03 ± 0.01, p=0.02), RCC (b=0.02 ± 0.01, p=0.04) and RETIC (b=0.03 ± 0.01, p=0.002) might modestly increase FI. In the observational cohort, increased TGI associated with decreased glycation gap, (i.e., measured HbA1c was lower than expected based on fasting glucose, (b=-0.09 ± 0.009, p<0.0001)) in people with preT2D but not in those with normoglycemia (b=0.02 ± 0.007, p<0.0001). Conclusions: MR suggests increased FI increases erythrocytosis and might potentially decrease HbA1c by non-glycemic effects. Increased TGI, a surrogate measure of increased FI, associates with lower-than-expected HbA1c in people with preT2D. These findings merit confirmatory studies to evaluate their clinical significance.

Emerging Therapies in ß-Thalassemia.

Advances in understanding the underlying pathophysiology of ß-thalassemia have enabled efforts toward the development of novel therapeutic modalities. These can be classified into three major categories based on their ability to target different features of the underlying disease pathophysiology: correction of the α/ß globin chain imbalance, targeting ineffective erythropoiesis, and targeting iron dysregulation. This article provides an overview of these different emerging therapies that are currently in development for ß-thalassemia.