Genetic variants in canonical Wnt signaling pathway associated with pediatric immune thrombocytopenia.

ABSTRACT: Through the use of genetic sequencing, molecular variants driving autoimmunity are increasingly identified in patients with chronic and refractory immune cytopenias. With the goal of discovering genetic variants that predispose to pediatric immune thrombocytopenia (ITP) or increase risk for chronic disease, we conducted a genome-wide association study in a large multi-institutional cohort of pediatric patients with ITP. A total of 591 patients were genotyped using an Illumina Global Screening Array BeadChip. Six variants met genome-wide significance in comparison between children with ITP and a cohort of healthy children. One variant in NAV2 was inversely associated with ITP (adjusted odds ratio [aOR], 0.52; P = 3.2 × 10-11). Two other variants in close proximity to NKD1 were also inversely associated with ITP (aOR, 0.43; P = 8.86 × 10-15; aOR, 0.48; P = 1.84 × 10-16). These genes have been linked to the canonical Wnt signaling pathway. No variants met genome-wide significance in comparison of those with ITP that self-resolved in <1 year versus those who developed chronic ITP. This study identifies genetic variants that may contribute to ITP risk and raises a novel pathway with a potential role in ITP pathogenesis.

Comorbidities and complications in adult and paediatric patients with pyruvate kinase deficiency: Analysis from the Peak Registry.

Pyruvate kinase (PK) deficiency, a rare, congenital haemolytic anaemia caused by mutations in the PKLR gene, is associated with many clinical manifestations, but the full disease burden has yet to be characterised. The Peak Registry (NCT03481738) is an observational, longitudinal registry of adult and paediatric patients with PK deficiency. Here, we described comorbidities and complications in these patients by age at most recent visit and PKLR genotype. As of 13 May 2022, 241 patients were included in the analysis. In total, 48.3% had undergone splenectomy and 50.5% had received chelation therapy. History of iron overload (before enrolment/during follow-up) was common (52.5%), even in never-transfused patients (20.7%). Neonatal complications and symptoms included jaundice, splenomegaly and hepatomegaly, with treatment interventions required in 41.5%. Among adults, osteopenia/osteoporosis occurred in 19.0% and pulmonary hypertension in 6.7%, with median onset ages of 37, 33 and 22 years, respectively. Biliary events and bone health problems were common across PKLR genotypes. Among 11 patients who had thromboembolic events, eight had undergone prior splenectomy. Patients with PK deficiency may have many complications, which can occur early in and throughout life. Awareness of their high disease burden may help clinicians better provide appropriate monitoring and management of these patients.

What is in a name: defining pediatric refractory ITP.

ABSTRACT: There are no agreed upon terminology to define "refractory" pediatric immune thrombocytopenia (ITP). Guidelines are therefore limited to arbitrary and outdated definitions. The Pediatric ITP Consortium of North America held a meeting in 2023 to define this entity. With 100% agreement, the faculty established that pediatric ITP that is refractory to emergent therapy could be defined as no platelet response after treatment with all eligible emergent pharmacotherapies. With 100% agreement, the working group established that pediatric patients with ITP that continue to demonstrate high disease burden and/or no platelet response despite treatment with multiple classes of disease-modifying therapies represent a challenging subset of ITP. These patients are at higher risk of ongoing disease burden and merit additional investigation as well as consideration for clinical trials or novel therapies. Future efforts to define disease burden and disease response will be completed in collaboration with the ITP International Working Group.

Quality of life in childhood immune thrombocytopenia: Revision of the Kids' ITP Tools (KIT).

The Kids ITP Tools (KIT) is a health-related quality of life (HRQoL) questionnaire that evaluates quality of life in children with immune thrombocytopenia (ITP). There are three formats: Child Self-Report, Parent Proxy-Report and Parent Impact-Report. This study aimed to develop a domain structure by grouping-related questions from the questionnaire into domains that independently reflect various aspects of HRQoL. The study was conducted in two phases. Phase 1 involved an online survey distributed to experts to identify conceptual domains for the KIT. Phase 2 utilized a statistical approach to analyse responses from patients with ITP and their families. A revised KIT 2.0 was ultimately developed to aid in treatment decision-making and monitoring of ITP.

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.

The 2022 review of the 2019 American Society of Hematology guidelines on immune thrombocytopenia.

ABSTRACT: The 2019 American Society of Hematology (ASH) guidelines for immune thrombocytopenia (ITP) included recommendations on the management of adults (recommendations 1-9) and children (recommendations 10-21) with primary ITP . We describe here the results of a review of the 2019 guidelines by a working group of experts requested by ASH to inform decision-making about the need for and timing of a guideline revision. An updated Medline and Embase search applied the same search terms as in the 2019 ASH guidelines, limited to systematic reviews and clinical trials, from May 2017 to July 2022. There were 193 studies identified, 102 underwent abstract reviews, and 54 full reviews. Each study was assessed based on relevance to the previous recommendation with regard to the population, prioritized outcomes, new outcomes, and study design. Reviewers assessed if the data would change the strength or the directionality of the existing recommendation or merit development of a new recommendation. Based on this review, the ASH Committee on Quality endorsed a focused update on second-line management for adults with ITP. In addition, there will be continued annual monitoring and reviewing of the 2019 ASH guidelines on ITP in full to evaluate when there is sufficient new evidence to warrant additional revisions.

Integrating circulating T follicular memory cells and autoantibody repertoires for characterization of autoimmune disorders.

Introduction: Autoimmune diseases are heterogeneous and often lack specific or sensitive diagnostic tests. Increased percentages of CD4+CXCR5+PD1+ circulating T follicular helper (cTfh) cells and skewed distributions of cTfh subtypes have been associated with autoimmunity. However, cTfh cell percentages can normalize with immunomodulatory treatment despite persistent disease activity, indicating the need for identifying additional cellular and/or serologic features correlating with autoimmunity. Methods: The cohort included 50 controls and 56 patients with autoimmune cytopenias, gastrointestinal, pulmonary, and/or neurologic autoimmune disease. Flow cytometry was used to measure CD4+CXCR5+ T cell subsets expressing the chemokine receptors CXCR3 and/or CCR6: CXCR3+CCR6- Type 1, CXCR3-CCR6- Type 2, CXCR3+CCR6+ Type 1/17, and CXCR3- CCR6+ Type 17 T cells. IgG and IgA autoantibodies were quantified using a microarray featuring 1616 full-length, conformationally intact protein antigens. The 97.5th percentile in the control cohort defined normal limits for T cell subset percentages and total number (burden) of autoantibodies. Results: This study focused on CD4+CXCR5+ T cells because CXCR5 upregulation occurs after cognate T-B cell interactions characteristic of autoimmune diseases. We refer to these cells as circulating T follicular memory (cTfm) cells to acknowledge the dynamic nature of antigen-experienced CXCR5+ T cells, which encompass progenitors of cTfh or Tfh cells as well as early effector memory T cells that have not yet lost CXCR5. Compared to controls, 57.1% of patients had increased CXCR5+CXCR3+CCR6+ cTfm1/17 and 25% had increased CXCR5+CXCR3-CCR6+ cTfm17 cell percentages. Patients had significantly more diverse IgG and IgA autoantibodies than controls and 44.6% had an increased burden of autoantibodies of either isotype. Unsupervised autoantibody clustering identified three clusters of patients with IgG autoantibody profiles distinct from those of controls, enriched for patients with active autoimmunity and monogenic diseases. An increased percentage of cTfm17 cells was most closely associated with an increased burden of high-titer IgG and IgA autoantibodies. A composite measure integrating increased cTfm1/17, cTfm17, and high-titer IgG and/or IgA autoantibodies had 91.1% sensitivity and 90.9% specificity for identifying patients with autoimmunity. Percentages of cTfm1/17 and cTfm17 percentages and numbers of high-titer autoantibodies in patients receiving immunomodulatory treatment did not differ from those in untreated patients, thus suggesting that measurements of cTfm can complement measurements of other cellular markers affected by treatment. Conclusions: This study highlights two new approaches for assessing autoimmunity: measuring CD4+CXCR5+ cTfm subsets as well as total burden of autoantibodies. Our findings suggest that these approaches are particularly relevant to patients with rare autoimmune disorders for whom target antigens and prognosis are often unknown.

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).

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.

Pyruvate kinase activators for treatment of pyruvate kinase deficiency.

Pyruvate kinase (PK) deficiency is a congenital hemolytic anemia with wide-ranging clinical symptoms and complications associated with significant morbidity and reduced health-related quality of life in both children and adults. The management of patients with PK deficiency has been historically challenging due to difficulties in the diagnostic evaluation, heterogeneity of clinical manifestations, and treatment options limited to supportive care with transfusions and splenectomy. An oral allosteric PK activator, mitapivat, is now a clinically available disease-modifying treatment for adults with PK deficiency. Phase 2 and 3 clinical trials of mitapivat have demonstrated sustained improvements in hemolytic anemia, hematopoiesis, and quality of life in many adults with PK deficiency and a generally reassuring safety profile with continued dosing. Additional long-term benefits include rapid and ongoing reduction in iron overload and potential stabilization of bone health. Clinical trials of treatment with mitapivat in children with PK deficiency are ongoing. In addition to disease-modifying treatment with PK activators, gene therapy is a potentially curative treatment currently under evaluation in clinical trials. With the availability of disease-targeted therapies, accurately diagnosing PK deficiency in patients with chronic hemolytic anemia is critical. PK activation and gene therapy have the potential to change the natural history of PK deficiency by improving clinical manifestations and patient quality of life and decreasing the risk of long-term complications.

Psychometric validation of the Pyruvate Kinase Deficiency Diary and Pyruvate Kinase Deficiency Impact Assessment in adults in the phase 3 ACTIVATE trial.

BACKGROUND: Pyruvate kinase (PK) deficiency is a rare hereditary disorder characterized by chronic hemolytic anemia and serious sequalae which negatively affect patient quality of life. This study aimed to psychometrically validate the first disease-specific patient-reported outcome (PRO) instruments: the 7-item PK Deficiency Diary (PKDD) and 12-item PK Deficiency Impact Assessment (PKDIA), designed to assess signs, symptoms, and impacts of PK deficiency in patients enrolled in the ACTIVATE global phase 3 study of mitapivat versus placebo (NCT03548220). METHODS: All validation analyses for the PKDD and PKDIA were performed on blinded data, with analyses on item integrity, scoring, reliability, and validity conducted on data from screening and baseline. Completion rates and baseline response distributions were characterized using descriptive statistics. Item response modelling was used to inform a weighted scoring system. Reliability was assessed by internal consistency and test-retest reliability; and validity by convergent and known-groups analyses. RESULTS: Of the 80 adults enrolled, baseline data were available for 77 (96.3%) and 78 (97.5%) patients for the PKDD and PKDIA, respectively. Item responses skewed right, indicating that mean values exceeded median values, especially for items utilizing a 0-10 numeric scale, which were subsequently recoded to a 0-4 scale; 4 items were removed from the PKDIA due to redundancy or low relevance to the trial population. Both the PKDD and PKDIA demonstrated high internal consistency (McDonald's coefficient ω = 0.86 and 0.90, respectively), test-retest reliability (intra-class coefficients of 0.94 and 0.87, respectively), and convergent validity with other PROs (linear correlation coefficients [|r|] between 0.30-0.73 and 0.50-0.82, respectively). CONCLUSIONS: The findings provide evidence of validity and reliability for the PKDD and PKDIA, the first disease-specific PRO measures for PK deficiency, and can therefore increase understanding of, and more accurately capture, the wider impact of PK deficiency on health-related quality of life. Trial registration ClinicalTrials.gov, NCT03548220. Registered June 07, 2018; https://www. CLINICALTRIALS: gov/ct2/show/NCT03548220 .

Pyruvate kinase (PK) deficiency is a rare genetic blood disorder with a wide range of signs and symptoms that may have a negative impact on patients' quality of life. Patient-reported outcome (PRO) instruments are tools that assess how a disease affects a patient from the patient's perspective. These instruments must go through a validation process to make sure they truly capture the patient's experience with their condition or its treatment. This study aimed to validate two new PRO instruments in adult patients enrolled in the ACTIVATE clinical trial (NCT03548220), where patients with PK deficiency received the drug mitapivat or a placebo. These two new PRO instruments are the first to be developed specifically for PK deficiency: the PK Deficiency Diary (PKDD), a daily diary that asks 7 questions to measure the core signs and symptoms of PK deficiency, and the PK Deficiency Impact Assessment (PKDIA), a weekly questionnaire with 12 questions to assess the impact of PK deficiency on a patient's life. The results of this study showed that the PKDD and PKDIA properly and reliably measured the signs, symptoms, and impacts of PK deficiency that they aimed to capture. These findings indicate that the PKDD and PKDIA are the first validated PROs specifically for PK deficiency and can help improve the understanding of the impact of PK deficiency on patients' quality of life.

HLA antibodies in fetal and neonatal alloimmune thrombocytopenia.

BACKGROUND: Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is caused by antibodies against human platelet antigens (HPA). However, in many cases that meet clinical criteria for the condition, maternal sera do not have HPA antibodies. In studies examining whether human leukocyte antigen (HLA) antibodies cause FNAIT, the results are limited and inconclusive. This study sought to examine whether clinically suspected FNAIT cases with absent maternal HPA antibodies had different HLA antibody strength and specificity compared to controls. STUDY DESIGN AND METHODS: A retrospective case-control study assessed class I HLA antibody strength and specificity in cases submitted for testing to Versiti, Wisconsin. There were 813 cases that met initial screening criteria, but written consent could only be obtained for 50. After review of medical records and expert panel review, 31 cases with clinical criteria of FNAIT and maternal HLA but not HPA antibodies were included. Each case was matched for maternal age, gestational age at delivery, parity, and race/ethnicity to two controls from unaffected pregnancies that had maternal serum HLA antibodies. RESULTS: FNAIT cases were found to have both significantly higher HLA antibody strength, measured by mean fluorescence index (MFI), and broader HLA antibody specificity at antigen epitope level, compared to matched controls (p < .001). p-values remained significant after controlling for parity and gestational age at delivery. DISCUSSION: Additional studies are needed to further examine whether the strong HLA antibodies identified in HPA-antibody-negative cases directly cause neonatal thrombocytopenia and whether prenatal treatment may be warranted in select cases to prevent recurrence.

Updates and advances in pyruvate kinase deficiency.

Mutations in the PKLR gene lead to pyruvate kinase (PK) deficiency, causing chronic hemolytic anemia secondary to reduced red cell energy, which is crucial for maintenance of the red cell membrane and function. Heterogeneous clinical manifestations can result in significant morbidity and reduced health-related quality of life. Treatment options have historically been limited to supportive care, including red cell transfusions and splenectomy. Current disease-modifying treatment considerations include an oral allosteric PK activator, mitapivat, which was recently approved for adults with PK deficiency, and gene therapy, which is currently undergoing clinical trials. Studies evaluating the role of PK activators in other congenital hemolytic anemias are ongoing. The long-term effect of treatment with disease-modifying therapy in PK deficiency will require continued evaluation.

The Pyruvate Kinase Deficiency Global Longitudinal (Peak) Registry: rationale and study design.

INTRODUCTION: Pyruvate kinase (PK) deficiency is a rare, under-recognised, hereditary condition that leads to chronic haemolytic anaemia and potentially serious secondary complications, such as iron overload, cholecystitis, pulmonary hypertension and extramedullary haematopoiesis. It is an autosomal recessive disease caused by homozygous or compound heterozygous mutations in the PKLR gene. Due to its rarity and clinical heterogeneity, information on the natural history and long-term clinical course of PK deficiency is limited, presenting major challenges to patient management, the development of new therapies and establishing disease-specific treatment recommendations. The Pyruvate Kinase Deficiency Global Longitudinal (Peak) Registry is an initiative to address the gaps in the knowledge of PK deficiency. This manuscript describes the objectives, study design and methodology for the Peak Registry. METHODS AND ANALYSIS: The Peak Registry is an observational, longitudinal, global registry of adult and paediatric patients with a genetically confirmed diagnosis of PK deficiency. The Peak Steering Committee is composed of 11 clinicians and researchers with experience in the diagnosis and management of PK deficiency from 10 countries, a patient representative and representatives from the sponsor (Agios Pharmaceuticals). The registry objective is to foster an understanding of the longitudinal clinical implications of PK deficiency, including its natural history, treatments and outcomes, and variability in clinical care. The aim is to enrol up to 500 participants from approximately 60 study centres across 20 countries over 7 years, with between 2 and 9 years of follow-up. Data will include demographics, diagnosis history, genotyping, transfusion history, relevant clinical events, medications, emergency room visits and hospitalisations. ETHICS AND DISSEMINATION: Registry protocol and informed consent forms are approved by institutional review boards/independent ethics committees at each study site. The study is being conducted in accordance with the Declaration of Helsinki. Registry data will be published in peer-reviewed journal articles and conference publications. TRIAL REGISTRATION NUMBER: NCT03481738.

Pediatric refractory immune thrombocytopenia: A systematic review.

Pediatric immune thrombocytopenia (ITP) is an acquired disorder associated with autoimmune destruction and impairment of platelet production in children. Some children exhibit poor or transient response to ITP-directed treatments and are referred to as having refractory ITP (rITP). There is currently no consensus on the definition of rITP, nor evidence-based treatment guidelines for patients with rITP. After a survey of pediatric ITP experts demonstrated lack of consensus on pediatric rITP, we pursued a systematic review to examine the reported clinical phenotypes and treatment outcomes in pediatric rITP. The search identified 253 relevant manuscripts; following review, 11 studies proposed a definition for pediatric rITP with no consensus amongst them. Most definitions included suboptimal response to medical management, while some outlined specific platelet thresholds to define this suboptimal response. Common attributes identified in this study should be used to propose a comprehensive definition, which will facilitate outcome comparisons of future rITP studies.

Utilization of an ITP quality improvement pathway improves adherence to management guidelines.

Despite availability of epidemiologic studies and national guidelines for the management of newly diagnosed pediatric immune thrombocytopenia (ITP), practice variation exists among and within hematology practices. We previously described the development of an ITP pathway guiding management based on bleeding symptoms. Over an 8-year period, integration of this iterative ITP pathway into management of newly diagnosed ITP increased observation rates in children with no or mild bleeding symptoms and improved consistency of laboratory evaluation and treatment strategies without increasing adverse outcomes. This quality improvement initiative has been sustainable, acceptable to providers, and increased adherence to guidelines.