Complement activation negatively affects the platelet response to thrombopoietin receptor agonists in patients with immune thrombocytopenia: a prospective cohort study.

Increased platelet destruction is central in the pathogenesis of immune thrombocytopenia. However, impaired platelet production is also relevant and its significance underlies the rationale for treatment with thrombopoietin receptor agonists (TPO-RAs). Previous studies have associated enhanced complement activation with increased disease severity. Additionally, treatment refractoriness has been demonstrated to resolve by the administration of complement-targeted therapeutics in a subset of patients. The association between complement activation and the platelet response to TPO-RA therapy has previously not been investigated. In this study, blood samples from patients with immune thrombocytopenia (n = 15) were prospectively collected before and two, six and 12 weeks after the initiation of TPO-RA therapy. Plasma levels of complement degradation product C4d and soluble terminal complement complexes were assessed. Patients with significantly elevated baseline levels of terminal complement complexes exhibited more often an inadequate platelet response (p = .04), were exclusively subjected to rescue therapy with intravenous immunoglobulin (p = .02), and did not respond with a significant platelet count increase during the study period. C4d showed a significant (p = .01) ability to distinguish samples with significant terminal complement activation, implying engagement of the classical complement pathway. In conclusion, elevated levels of complement biomarkers were associated with a worse TPO-RA treatment response. Larger studies are needed to confirm these results. Biomarkers of complement activation may prove valuable as a prognostic tool to predict which patients that potentially could benefit from complement-inhibiting therapy in the future.

What is the context?Primary immune thrombocytopenia (ITP) is a potentially serious illness associated with an increased risk of bleeds. Manifestations range from confined skin bruising to life-threatening intracranial hemorrhages.It is an acquired immune disorder characterized by increased destruction and impaired production of platelets.Treatments aim at suppressing the destruction and supporting the production of platelets.Thrombopoietin receptor agonists (TPO-RA) are medically approved platelet growth factors that contribute to the generation of new platelets.The complement system is an evolutionary preserved part of innate immunity.Previous studies have indicated that complement activation may be an important contributor to disease and that the administration of complement-inhibiting therapy improves the platelet count in a subset of patients with primary ITP.What is new? The potential association between complement activation and a poor platelet response to TPO-RA therapy in primary ITP has not been previously studied.In fifteen patients with primary ITP starting TPO-RA therapy, we prospectively followed the platelet response and levels of complement biomarkers for 12 weeks.We showed that patients with high levels of complement biomarkers exhibited a worse treatment response during the study period.What is the impact?Our results suggest that levels of complement biomarkers may be valuable to predict which patients with treatment-refractory ITP that potentially could benefit from complement-inhibiting therapy in the futureLarger studies are needed to confirm our results.

Bone mineral density in haemophilia - a multicentre study evaluating the impact of different replacement regimens.

AIM: The aim of this study was to investigate if prophylactic treatment in severe haemophilia impact on bone mineral densisty (BMD) in adults with haemophilia A/B. METHODS: Subjects with haemophilia (n = 120) underwent bone-density measurement and clinical data was collected. BMD in subjects with severe haemophilia on high-dose prophylaxis (n = 41) was compared to BMD in subjects with mild haemophilia (n = 33) and to severe haemophilia treated with intermediate-dose prophylaxis (n = 32) or on-demand replacement therapy (n = 14). RESULTS: Subjects with severe haemophilia on high-dose prophylaxis showed BMD at total hip comparable to subjects with mild haemophilia (median BMD 955.8 and 977.4 mg/cm2 (P = .17), respectively). No difference in BMD was found related to type of prophylactic regimen (median BMD 955.8 and 942.4 mg/cm2 , in high-dose and intermediate dose groups, respectively; P = .70). Subjects with severe disease treated on-demand had significantly lower BMD compared to subjects on a high-dose prophylactic regimen (median BMD 771.8 and 955.8 mg/cm2 (P = .001), respectively). BMD decreased significantly with age, regardless of severity of haemophilia disease. In a multivariate analysis, adjusted for disease status and age, type of prophylactic regimen was not significantly associated with osteoporosis development. CONCLUSION: We show that BMD differs in persons with severe haemophilia on propylaxis as compared to those treated on-demand, but that type of prophylactic regimen does not reflect on BMD. The difference between treatment groups was mainly explained by an age difference between groups. However, patients on prophylaxis displayed a high degree of normal BMD not far from mild haemophilia at comparative age.

Biomarkers of Complement and Platelet Activation are not correlated with the One or Twenty-Four Hours Corrected Count Increments in Prophylactically Platelet Transfused Hematological Patients: a Prospective Cohort Study.

Platelet transfusion refractoriness is a serious clinical concern that complicates the management of thrombocytopenic patients. Previous studies have suggested a potential role for both complement and platelet activation based on in vitro analyses of platelet concentrates. In this study, the post-transfusion platelet response, as indicated by the corrected count increment at 1 and 24 h after prophylactic platelet transfusions, respectively, was correlated with the 1 h post-transfusion Δconcentration (1 h post-transfusion - pretransfusion) of complement and platelet activation biomarkers. The study was registered as a clinical trial at ClinicalTrials.gov (identifier: NCT02601131) and patients were recruited during inpatient care in the hematological department. Soluble terminal complement complexes, soluble P-selectin and soluble CD40 ligand were analyzed. Confirmed alloimmunized patients were excluded. Included subjects were either given platelet transfusions (n = 43) and categorized into four clinical study groups or included in a non-transfused control group (n = 10). In total, 54 transfusions were included. No transfusion-mediated complement activation was observed. The transfusions were associated with a significant increase in the concentration of soluble P-selectin (p < .001), primarily corresponding to the passive infusion of soluble P-selectin-containing plasma residuals. The Δconcentration of soluble P-selectin was, however, not significantly correlated with the corrected count increments. Thus, significant correlations between biomarkers of complement and platelet activation and the post-transfusion platelet response could not be demonstrated in this study.

Clinical characterization and identification of rare genetic variants in atypical hemolytic uremic syndrome: A Swedish retrospective observational study.

Complement-mediated atypical hemolytic uremic syndrome (aHUS) is an ultra-rare renal disease primarily caused by genetic alterations in complement proteins. The genetic work-up required for confirmation of diagnosis is complicated and not always logistically accessible. The aim of the present study was to apply a diagnostic scheme compliant with the American College of Medical Genetics and Genomics guidelines to investigate the prevalence of complement-mediated aHUS among subjects formerly included in a retrospective cohort of clinically suspected aHUS. Clinical outcomes and genetic correlations to complement analyses were assessed. Subjects were investigated with medical record reviewing, inquiries, and laboratory analyses composed of whole genome sequencing; enzyme-linked immunosorbent assays for factor I, factor H, and factor H-specific antibodies; nephelometry for complement components three of four; flow cytometry for CD46 surface expression and immunoblotting for the presence of factor H-related protein 1. In total, 45% (n = 60/134) of the subjects were deceased at the time of study. Twenty of the eligible subjects consented to study participation. Based on genetic sequencing and clinical characteristics, six were categorized as definite/highly suspected complement-mediated aHUS, 10 as non-complement-mediated aHUS and four as having an HUS-like phenotype. In the complement-mediated aHUS group, two subjects had not received an aHUS diagnosis during the routine clinical management. Disease-contributing/likely disease-contributing genetic variants were identified in five subjects, including a novel missense variant in the complement factor H gene (c.3450A>G, p.I1150M). This study illustrates the risk for misdiagnosis in the management of patients with complement-mediated aHUS and the importance of a comprehensive assessment of both phenotype and genotype to reach a diagnosis.

Genomic and transcriptomic correlates of Richter transformation in chronic lymphocytic leukemia.

The transformation of chronic lymphocytic leukemia (CLL) to high-grade B-cell lymphoma is known as Richter syndrome (RS), a rare event with dismal prognosis. In this study, we conducted whole-genome sequencing (WGS) of paired circulating CLL (PB-CLL) and RS biopsies (tissue-RS) from 17 patients recruited into a clinical trial (CHOP-O). We found that tissue-RS was enriched for mutations in poor-risk CLL drivers and genes in the DNA damage response (DDR) pathway. In addition, we identified genomic aberrations not previously implicated in RS, including the protein tyrosine phosphatase receptor (PTPRD) and tumor necrosis factor receptor-associated factor 3 (TRAF3). In the noncoding genome, we discovered activation-induced cytidine deaminase-related and unrelated kataegis in tissue-RS affecting regulatory regions of key immune-regulatory genes. These include BTG2, CXCR4, NFATC1, PAX5, NOTCH-1, SLC44A5, FCRL3, SELL, TNIP2, and TRIM13. Furthermore, differences between the global mutation signatures of pairs of PB-CLL and tissue-RS samples implicate DDR as the dominant mechanism driving transformation. Pathway-based clonal deconvolution analysis showed that genes in the MAPK and DDR pathways demonstrate high clonal-expansion probability. Direct comparison of nodal-CLL and tissue-RS pairs from an independent cohort confirmed differential expression of the same pathways by RNA expression profiling. Our integrated analysis of WGS and RNA expression data significantly extends previous targeted approaches, which were limited by the lack of germline samples, and it facilitates the identification of novel genomic correlates implicated in RS transformation, which could be targeted therapeutically. Our results inform the future selection of investigative agents for a UK clinical platform study. This trial was registered at www.clinicaltrials.gov as #NCT03899337.

SAMHD1 Limits the Efficacy of Forodesine in Leukemia by Protecting Cells against the Cytotoxicity of dGTP.

The anti-leukemia agent forodesine causes cytotoxic overload of intracellular deoxyguanosine triphosphate (dGTP) but is efficacious only in a subset of patients. We report that SAMHD1, a phosphohydrolase degrading deoxyribonucleoside triphosphate (dNTP), protects cells against the effects of dNTP imbalances. SAMHD1-deficient cells induce intrinsic apoptosis upon provision of deoxyribonucleosides, particularly deoxyguanosine (dG). Moreover, dG and forodesine act synergistically to kill cells lacking SAMHD1. Using mass cytometry, we find that these compounds kill SAMHD1-deficient malignant cells in patients with chronic lymphocytic leukemia (CLL). Normal cells and CLL cells from patients without SAMHD1 mutation are unaffected. We therefore propose to use forodesine as a precision medicine for leukemia, stratifying patients by SAMHD1 genotype or expression.

First-line therapy in chronic lymphocytic leukemia: a Swedish nation-wide real-world study on 1053 consecutive patients treated between 2007 and 2013.

The aim of this study was to investigate long-term outcome following first-line therapy in consecutive chronic lymphocytic leukemia (CLL) patients in a well-defined geographic area: Sweden. All patients diagnosed with CLL (2007-2013) (n=3672) were identified from national registries, screening of patient files identified all (100%) treated first line (n=1053) and for those, an in-depth analysis was performed. End points were overall response rate, progression-free survival (PFS), overall survival (OS), and safety. Median age was 71 years; 53% had Rai stage III-IV and 97% had performance status grade 0-2. Fluorescence in situ hybridization (FISH) was performed in 57% of patients: 15% had del(17p). Chlorambucil + prednisone was used in 39% (5% also received rituximab). Fludarabine+cyclophosphamide+rituximab or fludarabine+cyclophosphamide was used in 43% and bendamustine + rituximab in 6%. Overall response rate was 64%; chlorambucil 43%, fludarabine+cyclophosphamide+rituximab 84%, fludarabine+cyclophosphamide 75% and bendamustine + rituximab 75%. Median PFS and OS was 24 and 58 months, respectively, both were significantly associated (multivariate analysis) with type of treatment, del(17p), performance status, gender, age and geographical region (OS only). Chlorambucil-treated patients had a median PFS and OS of only 9 and 33 months, respectively. Chlorambucil usage declined gradually throughout the study period, but one-third of patients still received chlorambucil + rituximab in 2013. Infections ≥grade III were significantly associated with treatment; chlorambucil 19% versus fludarabine+cyclophosphamide+rituximab 30%. Richter transformation occurred in 5.5% of the patients, equally distributed across therapies. This is the largest retrospective, real-world cohort of consecutive first-line treated CLL patients with a complete follow up. In elderly patients, an unmet need for more effective, well-tolerated therapies was identified.

Clinical-grade validation of whole genome sequencing reveals robust detection of low-frequency variants and copy number alterations in CLL.

The 100 000 Genome Project aims to develop a diagnostics platform by introducing whole genome sequencing (WGS) into clinical practice. Samples from patients with chronic lymphocytic leukaemia were subjected to WGS. WGS detection of single nucleotide variants and insertion/deletions were validated by targeted next generation sequencing showing high concordance (96·3%), also for detection of sub-clonal variants and low-frequency TP53 variants. Copy number alteration detection was verified by fluorescent in situ hybridisation and genome-wide single nucleotide polymorphism array (concordances of 86·7% and 92·9%, respectively), confirming adequate sensitivity by WGS. Our results confirm that WGS can provide comprehensive genomic characterisation for clinical trials, drug discovery and, ultimately, precision medicine.

Application of whole-exome sequencing to direct the specific functional testing and diagnosis of rare inherited bleeding disorders in patients from the Öresund Region, Scandinavia.

Rare inherited bleeding disorders (IBD) are a common cause of bleeding tendency. To ensure a correct diagnosis, specialized laboratory analyses are necessary. This study reports the results of an upfront diagnostic strategy using targeted whole exome sequencing. In total, 156 patients with a significant bleeding assessment tool score participated in the study, of which a third had thrombocytopenia. Eighty-seven genes specifically associated with genetic predisposition to bleeding were analysed by whole exome sequencing. Variants were classified according to the five-tier scheme. We identified 353 germline variants. Eight patients (5%) harboured a known pathogenic variant. Of the 345 previously unknown variants, computational analyses predicted 99 to be significant. Further filtration according to the Mendelian inheritance pattern, resulted in 59 variants being predicted to be clinically significant. Moreover, 34% (20/59) were assigned as novel class 4 or 5 variants upon targeted functional testing. A class 4 or 5 variant was identified in 30% of patients with thrombocytopenia (14/47) versus 11% of patients with a normal platelet count (12/109) (P < 0·01). An IBD diagnosis has a major clinical impact. The genetic investigations detailed here extricated our patients from a diagnostic conundrum, thus demonstrating that continuous optimization of the diagnostic work-up of IBD is of great benefit.

At the Cross Section of Thrombotic Microangiopathy and Atypical Hemolytic Uremic Syndrome: A Narrative Review of Differential Diagnostics and a Problematization of Nomenclature.

Complement-mediated atypical hemolytic uremic syndrome (aHUS) is a rare disease associated with high mortality and morbidity. Renal biopsies often indicate thrombotic microangiopathy (TMA). The condition is caused by an excessive activation of the alternative pathway leading to depositions of membrane attack complexes (MAC) on host cells. It may depend on mutations in complement components and regulatory proteins, or the formation of complement-specific antibodies. Mainly, an environmental trigger (e.g. infection) is needed for the excessive response to develop. The clinical characteristics are more or less shared with a wide range of diseases manifesting with microangiopathic hemolytic anemia. Because of prior deficits in pathogenic understanding, associated nomenclature has been based on clinical symptoms. New knowledge challenges these symptomatic definitions; however, an outdated terminology is still being applied in clinical practice to various extents. With respect to gained insights, it is more advantageous to rebuild the concepts on etiological and pathogenic grounds. The need for more distinct definitions is even more urgent in the light of the effective treatment regimen with eculizumab for complement-mediated aHUS. This review presents an up-to-date summary of the field of investigation, addresses the need for faster differential diagnostics and proposes a revised nomenclature based on the current pathogenic understanding.

Indications of underdiagnosis of atypical haemolytic uraemic syndrome in a cohort referred to the Coagulation Unit in Malmo, Sweden, for analysis of ADAMTS13 2007-2012.

AIM: Complement-mediated atypical haemolytic uraemic syndrome (aHUS) is a rare disease with high mortality and morbidity if left untreated. The diagnostic work-up is complicated and the manifestations overlap with other conditions. Therefore, we hypothesize that complement-mediated aHUS is an under diagnosed disease. METHODS: A cohort of 768 referrals referred to the Coagulation Unit in Malmo, Sweden, for analysis of a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13), 2007-2012, were retrospectively reviewed. Subjects were included on the basis of presence of haemolytic anaemia, thrombocytopaenia, renal failure and ADAMTS13 > 0.05. They were excluded if tested positive for Escherichia coli. Included subjects were categorized as "suspected HUS" with and without potential causes and triggers. Levels of C3 and C4, presence of complement factor H (CFH)-specific antibodies and associated deficiency in complement factor H related protein 1 (CFHR1) were analyzed on frozen samples. RESULTS: In total, 134/316 (42%) unique subjects fulfilled inclusion criteria; 103 were categorized as "suspected HUS associated with potential causes/triggers" and 31 subjects categorized as "suspected HUS" without such association. One case of complement-mediated aHUS had been confirmed during the treatment period. Laboratory analyses performed showed that in total 78 cases had findings consistent with complement-mediated aHUS: 24 cases indicated presence of CFH-specific antibodies whereof five cases had isolated low C3 titres and six cases had deficiency of CFHR1. Additionally 54 cases indicated isolated alternative pathway consumption. CONCLUSION: The results suggest that the presence of complement-mediated aHUS was under diagnosed in this cohort calling for improvement of diagnostic availability.

Long-term anti-FVIII antibody response in Bethesda-negative haemophilia A patients receiving continuous replacement therapy.

It has previously been shown that patients with haemophilia A may develop non-neutralizing anti-factor VIII (FVIII) antibodies (NNA) that escape detection by the Bethesda assay, but are detected using immune-based assays. We and others found NNAs to be directed not only towards non-functional parts of the protein, but towards all regions of the FVIII protein. We also showed a heterogeneous antibody response towards different FVIII products. However, the clinical relevance and the natural history of NNA remain unclear. Therefore, we followed a cohort of unrelated subjects with haemophilia A for 4 years with the goal of exploring the long-term development of NNA using an enzyme-linked immunosorbent assay (ELISA). Ten of 78 subjects (12·8%) exhibited an immune response that was transient and heterogeneous, and none of the subjects developed an FVIII inhibitor. The result of the ELISA was examined in relation to clinical variables and no significant associations between a positive ELISA and age, F8 mutation, port-à-cath implantation and HCV infection were shown. Interestingly, patients with NNA had significantly fewer bleeding episodes (P = 0·048) compared with NNA-negative subjects. The results indicate that the immune response to FVIII products within an individual may vary over time. However, the clinical impact of NNA remains unclear.

Combination of FVIII and by-passing agent potentiates in vitro thrombin production in haemophilia A inhibitor plasma.

The by-passing agents, recombinant activated factor VII (rFVIIa) and activated prothrombin complex concentrate (APCC), are important tools in the treatment of patients with haemophilia A and high-responding inhibitory antibodies. It has been observed clinically that in some patients undergoing immune tolerance induction the bleeding frequency decreases, hypothetically caused by a transient haemostatic effect of infused FVIII not measurable ex vivo. We evaluated how by-passing agents and factor VIII (FVIII) affect thrombin generation (TG) in vitro using plasma from 11 patients with severe haemophilia A and high titre inhibitors. Samples were spiked with combinations of APCC, rFVIIa and five different FVIII products. Combination of APCC and FVIII showed a synergistic effect in eliciting TG (P<0·005) for four FVIII products. When rFVIIa and FVIII were combined the interaction between the preparations was found to be additive. APCC and rFVIIa were then combined without FVIII, resulting in an additive effect on thrombin production. Each product separately increased TG above baseline. In conclusion, the amount of thrombin formed in vitro by adding a by-passing agent, was higher in the presence of FVIII. Our findings support the use of FVIII in by-passing therapy to optimize the haemostatic effect.

Quiescence of hematopoietic stem cells and maintenance of the stem cell pool is not dependent on TGF-beta signaling in vivo.

OBJECTIVE: Maintained quiescence of hematopoietic stem cells (HSCs) is of critical importance to prevent premature exhaustion of the stem cell pool under conditions of hematopoietic stress. The growth inhibitory cytokine transforming growth factor beta (TGF-beta) has been shown to play a critical role in maintaining quiescence of HSCs in vitro. Here, we have used conditional knockout mice for the TGF-beta type I receptor (TbetaRI) to ask whether the naturally quiescent state of HSCs in vivo is dependent on TGF-beta signaling and thus whether TGF-beta serves as a protective factor for the stem cell pool during conditions of stress. METHODS: TbetaRI null and control bone marrow chimeras were subjected to repeated treatments with the cell cycle-specific cytotoxic drug 5-fluorouracil (5-FU) and surviving HSCs were assayed by competitive transplantation experiments. Exhaustion of stem cells was provoked by serially transplanting TGF-beta signaling-deficient as well as normal BM cells into lethally irradiated recipients, which were monitored for survival. RESULTS: Surprisingly, we found that TGF-beta receptor-deficient HSCs have similar susceptibility, compared to controls, to repeated 5-FU treatments, indicative of normally maintained quiescence in these cells. Likewise, hematopoietic failure occurred at similar stages in serially transplanted recipients of TbetaRI null and control BM, respectively, demonstrating normal consumption of the stem cell pool during hematopoietic stress. CONCLUSIONS: These findings clearly demonstrate that, despite a key role in vitro, TGF-beta does not provide the necessary signal that induces the quiescent state of HSCs and maintains the stem cell pool in vivo.

Haematopoietic stem cells retain long-term repopulating activity and multipotency in the absence of stem-cell leukaemia SCL/tal-1 gene.

The production of blood cells is sustained throughout the lifetime of an individual by haematopoietic stem cells (HSCs). Specification of HSCs from mesoderm during embryonic development requires the stem cell leukaemia SCL/tal-1 gene product. Forced expression of SCL/tal-1 strongly induces blood formation in embryos, indicating that this gene has a dominant role in commitment to haematopoiesis. In the adult haematopoietic system, expression of SCL/tal-1 is enriched in HSCs and multipotent progenitors, and in erythroid and megakaryocytic lineages, consistent with roles for this factor in adult haematopoiesis. Here we assess by conditional gene targeting whether SCL/tal-1 is required continuously for the identity and function of HSCs. We find that SCL/tal-1 is dispensable for HSC engraftment, self-renewal and differentiation into myeloid and lymphoid lineages; however, the proper differentiation of erythroid and megakaryocytic precursors is dependent on SCL/tal-1. Thus, SCL/tal-1 is essential for the genesis of HSCs, but its continued expression is not essential for HSC functions. These findings contrast with lineage choice mechanisms, in which the identity of haematopoietic lineages requires continuous transcription factor expression.