Characterization of genetic variants in the EGLN1/PHD2 gene identified in a European collection of patients with erythrocytosis.

Hereditary erythrocytosis is a rare hematologic disorder characterized by an excess of red blood cell production. Here we describe a European collaborative study involving a collection of 2,160 patients with erythrocytosis sequenced in ten different laboratories. We focused our study on the EGLN1 gene and identified 39 germline missense variants including one gene deletion in 47 probands. EGLN1 encodes the PHD2 prolyl 4-hydroxylase, a major inhibitor of hypoxia-inducible factor. We performed a comprehensive study to evaluate the causal role of the identified PHD2 variants: (i) in silico studies of localization, conservation, and deleterious effects; (ii) analysis of hematologic parameters of carriers identified in the UK Biobank; (iii) functional studies of the protein activity and stability; and (iv) a comprehensive study of PHD2 splicing. Altogether, these studies allowed the classification of 16 pathogenic or likely pathogenic mutants in a total of 48 patients and relatives. The in silico studies extended to the variants described in the literature showed that a minority of PHD2 variants can be classified as pathogenic (36/96), without any differences from the variants of unknown significance regarding the severity of the developed disease (hematologic parameters and complications). Here, we demonstrated the great value of federating laboratories working on such rare disorders in order to implement the criteria required for genetic classification, a strategy that should be extended to all hereditary hematologic diseases.

Erythrocytosis associated with IgA nephropathy.

BACKGROUND: Erythrocytosis is a hematological disorder usually related to hematopoietic stem cell somatic mutations. However, unexplained erythrocytosis remains frequent. In this study, we evaluated the involvement of IgA1, a regulator of erythropoiesis also implicated in IgA nephropathy (IgAN) pathophysiology, in unexplained polycythemia/erythrocytosis (PE) of IgAN patients. METHODS: IgAN-PE patients' serum was collected, analyzed and used to study IgA1 effect on proliferation and differentiation of erythroid progenitors. Hematological parameters of transgenic mice for human alpha1 heavy chain were studied. Multicentric observational cohorts of chronic kidney disease (CKD) patients, including both native kidney diseases and renal transplants, were studied to analyze patient hemoglobin levels. FINDINGS: We retrospectively identified 6 patients with IgAN and unexplained PE. In large CKD cohorts, IgAN was associated with PE in 3.5% of patients (p<0.001 compared to other nephropathies). IgAN was an independent factor associated with higher hemoglobin levels (13.1g/dL vs 12.2 g/dL, p=0.01). During post-transplant anemia, anemia recovery was faster in IgAN patients. Elevated polymeric/monomeric IgA1 ratio as well as high Gd-IgA1 rate were observed in circulating IgA1 of the 6 IgAN-PE patients as compared with control or IgAN patients without PE. IgA1 from these patients increased the sensitivity of erythroid progenitors to Epo. In mice, we also observed an elevation of hematocrit in alpha1 knock-in mice compared to wild type controls. INTERPRETATION: These data identify a new etiology of erythrocytosis and demonstrate the role of pIgA1 in human erythropoiesis. This syndrome of IgA-related erythrocytosis should be investigated in case of unexplained erythrocytosis and renal disease. FUNDING: This work was supported by INSERM (French national institute for health and medical research), Labex GRex and Imagine Institute (Paris, France).

Inferring the dynamics of mutated hematopoietic stem and progenitor cells induced by IFNα in myeloproliferative neoplasms.

Classical BCR-ABL-negative myeloproliferative neoplasms (MPNs) are clonal disorders of hematopoietic stem cells (HSCs) caused mainly by recurrent mutations in genes encoding JAK2 (JAK2), calreticulin (CALR), or the thrombopoietin receptor (MPL). Interferon α (IFNα) has demonstrated some efficacy in inducing molecular remission in MPNs. To determine factors that influence molecular response rate, we evaluated the long-term molecular efficacy of IFNα in patients with MPN by monitoring the fate of cells carrying driver mutations in a prospective observational and longitudinal study of 48 patients over more than 5 years. We measured the clonal architecture of early and late hematopoietic progenitors (84 845 measurements) and the global variant allele frequency in mature cells (409 measurements) several times per year. Using mathematical modeling and hierarchical Bayesian inference, we further inferred the dynamics of IFNα-targeted mutated HSCs. Our data support the hypothesis that IFNα targets JAK2V617F HSCs by inducing their exit from quiescence and differentiation into progenitors. Our observations indicate that treatment efficacy is higher in homozygous than heterozygous JAK2V617F HSCs and increases with high IFNα dose in heterozygous JAK2V617F HSCs. We also found that the molecular responses of CALRm HSCs to IFNα were heterogeneous, varying between type 1 and type 2 CALRm, and a high dose of IFNα correlates with worse outcomes. Our work indicates that the long-term molecular efficacy of IFNα implies an HSC exhaustion mechanism and depends on both the driver mutation type and IFNα dose.

Different impact of calreticulin mutations on human hematopoiesis in myeloproliferative neoplasms.

Mutations of calreticulin (CALRm) define a subtype of myeloproliferative neoplasms (MPN). We studied the biological and genetic features of CALR-mutated essential thrombocythemia and myelofibrosis patients. In most cases, CALRm were found in granulocytes, monocytes, B and NK cells, but also in T cells. However, the type 1 CALRm spreads more easily than the type 2 CALRm in lymphoid cells. The CALRm were also associated with an early clonal dominance at the level of hematopoietic stem and progenitor cells (HSPC) with no significant increase during granulo/monocytic differentiation in most cases. Moreover, we found that half of type 2 CALRm patients harbors some homozygous progenitors. Those patients were associated with a higher clonal dominance during granulo/monocytic differentiation than patients with only heterozygous type 2 CALRm progenitors. When associated mutations were present, CALRm were the first genetic event suggesting that they are both the initiating and phenotypic event. In blood, type 1 CALRm led to a greater increased number of all types of progenitors compared with the type 2 CALRm. However, both types of CALRm induced an increase in megakaryocytic progenitors associated with a ruxolitinib-sensitive independent growth and with a mild constitutive signaling in megakaryocytes. At the transcriptional level, type 1 CALRm seems to deregulate more pathways than the type 2 CALRm in megakaryocytes. Altogether, our results show that CALRm modify both the HSPC and megakaryocyte biology with a stronger effect for type 1 than for type 2 CALRm.

Correction to: The prognostic value of serum erythropoietin in patients with lower-risk myelodysplastic syndromes: a review of the literature and expert opinion.

This article was originally published without an Open Access but due to the authors final decision to opt for Open Choice this correction was created.

The prognostic value of serum erythropoietin in patients with lower-risk myelodysplastic syndromes: a review of the literature and expert opinion.

Myelodysplastic syndromes (MDS) are hematopoietic stem cell malignancies associated with an erythroid maturation defect, resulting in anemia. Treatments for MDS include erythropoiesis-stimulating agents (ESAs). The identification of prognostic markers is important to help predict response and improve outcomes. Various scoring systems have been developed to help predict response to ESAs. Despite limitations in its assessment, serum erythropoietin (sEPO) level is an important predictor of hematologic response to ESAs in patients with lower-risk MDS. Numerous studies have reported significantly lower sEPO levels among responders versus non-responders. Furthermore, treatment response is significantly more likely among those with sEPO levels below versus those above various cutoffs. Other prognostic indicators for response to ESAs include lower transfusion requirement, fewer bone marrow blasts, higher hemoglobin, lower serum ferritin, lower-risk MDS, and more normal cytogenetics. Studies of other MDS therapies (e.g., lenalidomide and luspatercept) have also reported that lower sEPO levels are indicative of hematologic response. In addition, lower sEPO levels (up to 500 IU/L) have been included in treatment algorithms for patients with lower-risk MDS to define whether ESAs are indicated. Lower sEPO levels are predictive of hematologic response-particularly to ESAs. Further, clinical trials should use sEPO thresholds to ensure more homogeneous cohorts.

New pathogenic mechanisms induced by germline erythropoietin receptor mutations in primary erythrocytosis.

Primary familial and congenital polycythemia is characterized by erythropoietin hypersensitivity of erythroid progenitors due to germline nonsense or frameshift mutations in the erythropoietin receptor gene. All mutations so far described lead to the truncation of the C-terminal receptor sequence that contains negative regulatory domains. Their removal is presented as sufficient to cause the erythropoietin hypersensitivity phenotype. Here we provide evidence for a new mechanism whereby the presence of novel sequences generated by frameshift mutations is required for the phenotype rather than just extensive truncation resulting from nonsense mutations. We show that the erythropoietin hypersensitivity induced by a new erythropoietin receptor mutant, p.Gln434Profs*11, could not be explained by the loss of negative signaling and of the internalization domains, but rather by the appearance of a new C-terminal tail. The latter, by increasing erythropoietin receptor dimerization, stability and cell-surface localization, causes pre-activation of erythropoietin receptor and JAK2, constitutive signaling and hypersensitivity to erythropoietin. Similar results were obtained with another mutant, p.Pro438Metfs*6, which shares the same last five amino acid residues (MDTVP) with erythropoietin receptor p.Gln434Profs*11, confirming the involvement of the new peptide sequence in the erythropoietin hypersensitivity phenotype. These results suggest a new mechanism that might be common to erythropoietin receptor frameshift mutations. In summary, we show that primary familial and congenital polycythemia is more complex than expected since distinct mechanisms are involved in the erythropoietin hypersensitivity phenotype, according to the type of erythropoietin receptor mutation.

Evaluation of the safety and immunogenicity of subcutaneous HX575 epoetin alfa in the treatment of anemia associated with chronic kidney disease in predialysis and dialysis patients
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AIM: To assess the safety and immunogenicity of subcutaneous (SC) HX575 (epoetin-α) in dialysis- and nondialysis-dependent adult patients with chronic kidney disease (CKD). METHODS: Open-label, single-arm, multicenter study in patients (n = 416) from Germany, Italy, Poland, Romania, Russia, Turkey, and Ukraine. RESULTS: Mean (standard deviation (SD)) age was 52.3 (15.8) years, all patients were Caucasian, and similar proportions were male/female. 250 patients (60.1%) were erythropoiesis-stimulating agent (ESA)-naïve, and 166 (39.9%) were receiving ESA maintenance therapy at study start; mean (SD) on-study treatment duration with HX575 was 43.4 (15.8) weeks and 45.3 (13.7) weeks, respectively. Binding antierythropoietin (EPO) antibodies were detected by radioimmunoprecipitation (RIP) assay in 7 patients (1.7%; incidence 0.019); 5 of these were ESA-naïve at study entry. No patient developed neutralizing antibodies as determined in a cell-based epoetin neutralizing assay. Of the 7 patients with a positive binding anti-EPO RIP assay, 4 tested negative at later time points while continuing HX575 treatment. Three patients had low titers of anti-EPO antibodies at the last study assessment. There were no clinical signs of immunogenicity or hypersensitivity. CONCLUSIONS: SC HX575 was effective for correcting and maintaining correction of anemia, and the mean weekly dose remained stable over time.
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Selective testing for calreticulin gene mutations in patients with splanchnic vein thrombosis: A prospective cohort study.

BACKGROUND AND AIMS: Myeloproliferative neoplasms (MPN) are the leading cause of splanchnic vein thrombosis (SVT). Janus kinase 2 gene (JAK2)V617F mutations are found in 80 to 90% of patients with SVT and MPN. Mutations of the calreticulin (CALR) gene have also been reported. However, as their prevalence ranges from 0 to 2%, the utility of routine testing is questionable. This study aimed to identify a group of patients with SVT at high risk of harboring CALR mutations and thus requiring this genetic testing. METHODS: CALR, JAK2V617F and thrombopoietin receptor gene (MPL) mutations were analysed in a test cohort that included 312 patients with SVT. Criteria to identify patients at high risk of CALR mutations in this test cohort was used and evaluated in a validation cohort that included 209 patients with SVT. RESULTS: In the test cohort, 59 patients had JAK2V617F, five had CALR and none had MPL mutations. Patients with CALR mutations had higher spleen height and platelet count than patients without these mutations. All patients with CALR mutations had a spleen height ⩾16cm and platelet count >200×109/L. These criteria had a positive predictive value of 56% (5/9) and a negative predictive value of 100% (0/233) for the identification of CALR mutations. In the validation cohort, these criteria had a positive predictive value of 33% (2/6) and a negative predictive value of 99% (1/96). CONCLUSION: CALR mutations should be tested in patients with SVT, a spleen height ⩾16cm, platelet count >200×109/L, and no JAK2V617F. This strategy avoids 96% of unnecessary CALR mutations testing. Lay summary: Mutations of the CALR gene are detected in 0 to 2% of patients with SVT, thus the utility of systematic CALR mutation testing to diagnose MPN is questionable. This study demonstrates that CALR mutations testing can be restricted to patients with SVT, a spleen height ⩾16cm, a platelet count >200×109/L, and no JAK2V617F. This strategy avoids 96% of unnecessary CALR mutations testing.

Presence of atypical thrombopoietin receptor (MPL) mutations in triple-negative essential thrombocythemia patients.

Mutations in signaling molecules of the cytokine receptor axis play a central role in myeloproliferative neoplasm (MPN) pathogenesis. Polycythemia vera is mainly related to JAK2 mutations, whereas a wider mutational spectrum is detected in essential thrombocythemia (ET) with mutations in JAK2, the thrombopoietin (TPO) receptor (MPL), and the calreticulin (CALR) genes. Here, we studied the mutational profile of 17 ET patients negative for JAK2V617F, MPLW515K/L, and CALR mutations, using whole-exome sequencing and next-generation sequencing (NGS) targeted on JAK2 and MPL. We found several signaling mutations including JAK2V617F at very low allele frequency, 1 homozygous SH2B3 mutation, 1 MPLS505N, 1 MPLW515R, and 2 MPLS204P mutations. In the remaining patients, 4 presented a clonal and 7 a polyclonal hematopoiesis, suggesting that certain triple-negative ETs are not MPNs. NGS on 26 additional triple-negative ETs detected only 1 MPLY591N mutation. Functional studies on MPLS204P and MPLY591N revealed that they are weak gain-of-function mutants increasing MPL signaling and conferring either TPO hypersensitivity or independence to expressing cells, but with a low efficiency. Further studies should be performed to precisely determine the frequency of MPLS204 and MPLY591 mutants in a bigger cohort of MPN.

Severe chronic primary neutropenia in adults: report on a series of 108 patients.

Severe chronic primary neutropenia (CPN) is a rare entity, and long-term outcome and risk factors for infections in severe CPN adults have not been described to date. We report the characteristics and outcomes of 108 severe adult CPN patients enrolled in a multi-institutional observational study. Severe CPN adults were mostly female (78%), and median age at diagnosis was 28.3 years. Diagnosis was fortuitous in 62% of cases. The median absolute neutrophil count (ANC) at diagnosis was 0.4 × 10(9)/L, and median ANC without granulocyte colony-stimulating factor (G-CSF) during follow-up was 0.5 × 10(9)/L. Twenty-three of 66 (34.8%) evaluable patients had neutrophil autoantibodies, and 6 of 47 (12.8%) a T-cell clone. The presence of neutrophil autoantibodies or T-cell clone was not associated with any specific clinical or biological characteristics. No death or hematologic malignancies occurred, and 44 severe bacterial infections were reported in 27 patients with a median follow-up of 8.3 years. Fifty patients received G-CSF either sporadically (n = 24) or continuously (n = 26) and responded (96%). Nineteen patients received immunosuppressive therapies: overall response (OR) was 41%, and median duration of response was 3 months. At diagnosis, the only predictive factor for the occurrence of severe bacterial infections was an ANC count below 0.2 × 10(9)/L (OR, 0.76). Severe CPN in adults is characterized by a female predominance and a benign outcome with a low rate of severe bacterial infections and no secondary malignancies. G-CSF is efficient and well tolerated but is not required in a majority of patients.

Germline duplication of ATG2B and GSKIP predisposes to familial myeloid malignancies.

No major predisposition gene for familial myeloproliferative neoplasms (MPN) has been identified. Here we demonstrate that the autosomal dominant transmission of a 700-kb duplication in four genetically related families predisposes to myeloid malignancies, including MPN, frequently progressing to leukemia. Using induced pluripotent stem cells and primary cells, we demonstrate that overexpression of ATG2B and GSKIP enhances hematopoietic progenitor differentiation, including of megakaryocytes, by increasing progenitor sensitivity to thrombopoietin (TPO). ATG2B and GSKIP cooperate with acquired JAK2, MPL and CALR mutations during MPN development. Thus, the germline duplication may change the fitness of cells harboring signaling pathway mutations and increases the probability of disease development.

Biosimilars: from technical to pharmacoeconomic considerations. 30th Rencontres Nationales de Pharmacologie et Recherche clinique pour l'Innovation et l'Evaluation des Technologies de Santé. Tables rondes.

A biosimilar is a biological medicinal product claimed to be similar to a reference biological medicinal product. Its development plan includes studies comparing it with the reference product in order to confirm its similarity in terms of quality, preclinical safety, clinical efficacy, and clinical safety, including immunogenicity. Biosimilars differ from generics both in their molecular complexity and in the specific requirements that apply to them. Since patents on many biological medicinal products will expire within the next 5 years in major therapeutic areas such as oncology, rheumatology and gastroenterology and as those products are so costly to the French national health insurance system, the availability of biosimilars would have a considerable economic impact. The round table has issued a number of recommendations intended to ensure that the upcoming arrival of biosimilars on the market is a success, in which prescribing physicians would have a central role in informing and reassuring patients, an efficient monitoring of the patients treated with biologicals would be set up and time to market for biosimilars would be speeded up.

Incidence of erythropoietin antibody-mediated pure red cell aplasia: the Prospective Immunogenicity Surveillance Registry (PRIMS).

BACKGROUND: Subcutaneous administration of Eprex(®) (epoetin alfa) in patients with chronic kidney disease (CKD) was contraindicated in the European Union between 2002 and 2006 after increased reports of anti-erythropoietin antibody-mediated pure red cell aplasia (PRCA). The Prospective Immunogenicity Surveillance Registry (PRIMS) was conducted to estimate the incidence of antibody-mediated PRCA with subcutaneous administration of a new coated-stopper syringe presentation of Eprex(®) and to compare this with the PRCA incidence with subcutaneous NeoRecormon(®) (epoetin beta) and Aranesp(®) (darbepoetin alfa). METHODS: PRIMS was a multicentre, multinational, non-interventional, parallel-group, immunogenicity surveillance registry. Adults with CKD receiving or about to initiate subcutaneous Eprex(®), NeoRecormon(®) or Aranesp(®) for anaemia were enrolled and followed for up to 3 years. Unexplained loss or lack of effect (LOE), including suspected PRCA, was reported, with antibody testing for confirmation of PRCA. RESULTS: Of the 15 333 patients enrolled, 5948 received Eprex(®) (8377 patient-years) and 9356 received NeoRecormon(®)/Aranesp(®) (14 286 patient-years). No treatment data were available for 29 patients. Among 23 patients with LOE, five cases of PRCA were confirmed (Eprex(®), n = 3; NeoRecormon(®), n = 1; Aranesp(®), n = 1). Based on exposed time, PRCA incidence was 35.8/100 000 patient-years (95% CI 7.4-104.7) for Eprex(®) versus 14.0/100 000 patient-years (95% CI 1.7-50.6) for NeoRecormon(®)/Aranesp(®). The incidence of PRCA with Eprex(®) was not significantly different versus comparator ESAs (rate ratio: 2.56; 95% CI 0.43-15.31). An analysis based on observed time produced similar findings. CONCLUSION: This large, prospective registry demonstrates that PRCA is rare with subcutaneous administration of either the new coated-stopper syringe presentation of Eprex(®), or NeoRecormon(®) or Aranesp(®).

Biosimilars: from Technical to Pharmacoeconomic Considerations.

A biosimilar is a biological medicinal product claimed to be similar to a reference biological medicinal product. Its development plan includes studies comparing it with the reference product in order to confirm its similarity in terms of quality, preclinical safety, clinical efficacy, and clinical safety, including immunogenicity. Biosimilars differ from generics both in their molecular complexity and in the specific requirements that apply to them. Since patents on many biological medicinal products will expire within the next 5 years in major therapeutic areas such as oncology, rheumatology and gastroenterology and as those products are so costly to the French national health insurance system, the availability of biosimilars would have a considerable economic impact. The round table has issued a number of recommendations intended to ensure that the upcoming arrival of biosimilars on the market is a success, in which prescribing physicians would have a central role in informing and reassuring patients, an efficient monitoring of the patients treated with biologicals would be set up and time to market for biosimilars would be speeded up.

Similar names for similar biologics.

Approval of the first biosimilar in the USA may occur by the end of 2014, yet a naming approach for biosimilars has not been determined. Biosimilars are highly similar to their biologic reference product but are not identical to it, because of their structural complexity and variations in manufacturing processes among companies. There is a need for a naming approach that can distinguish a biosimilar from its reference product and other biosimilars and ensure accurate tracing of adverse events (AEs) to the administered product. In contrast, generic small-molecule drugs are identical to their reference product and, therefore, share the same nonproprietary name. Clinical trials required to demonstrate biosimilarity for approval may not detect rare AEs or those occurring after prolonged use, and the incidence of such events may differ between a biosimilar and its reference product. The need for precise biologic identification is further underscored by the possibility of biosimilar interchangeability, a US designation that will allow substitution without prescriber intervention. For several biologics, the US Food and Drug Administration (FDA) has used a naming approach that adds a prefix to a common root nonproprietary name, enabling healthcare providers to distinguish between products, avoid medication errors, and facilitate pharmacovigilance. We recommend that the FDA implement a biosimilars naming policy that likewise would add a distinguishable prefix or suffix to the root nonproprietary name of the reference product. This approach would ensure that a biosimilar could be distinguished from its reference product and other biosimilars in patient records and pharmacovigilance databases/reports, facilitating accurate attribution of AEs.

Autoimmune neutropenia after kidney transplantation: a disregarded entity of posttransplant neutropenia.

BACKGROUND: Neutropenia is common after kidney transplantation and is associated with an increased incidence of infections. Drug toxicities are the main causes of posttransplant neutropenia (PTN), mainly related to immunosuppressive drugs as mycophenolic acid (MPA) and anti-infectious agents, but some PTN remain unexplained. METHODS: Between January 2012 and January 2013, cultures of autologous granulocytic progenitors from bone marrow aspirate were performed in two patients with unexplained severe neutropenia. RESULTS: Both patients' serum inhibited granulocytic differentiation while granulocytic differentiation was normal with the control serum. Similar inhibition of differentiation of granulocytic progenitors from a control marrow was observed with the patients' serum as compared with the control serum. Moreover, in both cases intravenous immunoglobulins allowed full neutrophil count recovery. Other usual etiologies of acquired neutropenia including systemic drug toxicity, infection, and autoimmune disease were excluded. As frequently observed in adult immune neutropenia, granulocyte autoantibodies were absent in both cases. Owing to biological and clinical results, we concluded that an autoimmune mechanism was responsible for neutropenia. The levels of MPA, which is known to interact with tacrolimus, were not measured in our patients. However, the persistence of neutropenia more than 70 days after withdrawal of MPA did not support this hypothesis. CONCLUSION: Autoimmune neutropenia should be considered in kidney transplant recipients in case of persistent unexplained neutropenia as it allows effective treatment and avoids the withdrawal of important immunosuppressive and anti-infectious treatments.