Recombinant ADAMTS13 in Congenital Thrombotic Thrombocytopenic Purpura.

BACKGROUND: Congenital thrombotic thrombocytopenic purpura (TTP) results from severe hereditary deficiency of ADAMTS13. The efficacy and safety of recombinant ADAMTS13 and standard therapy (plasma-derived products) administered as routine prophylaxis or on-demand treatment in patients with congenital TTP is not known. METHODS: In this phase 3, open-label, crossover trial, we randomly assigned patients in a 1:1 ratio to two 6-month periods of prophylaxis with recombinant ADAMTS13 (40 IU per kilogram of body weight, administered intravenously) or standard therapy, followed by the alternate treatment; thereafter, all the patients received recombinant ADAMTS13 for an additional 6 months. The trigger for this interim analysis was trial completion by at least 30 patients. The primary outcome was acute TTP events. Manifestations of TTP, safety, and pharmacokinetics were assessed. Patients who had an acute TTP event could receive on-demand treatment. RESULTS: A total of 48 patients underwent randomization; 32 completed the trial. No acute TTP event occurred during prophylaxis with recombinant ADAMTS13, whereas 1 patient had an acute TTP event during prophylaxis with standard therapy (mean annualized event rate, 0.05). Thrombocytopenia was the most frequent TTP manifestation (annualized event rate, 0.74 with recombinant ADAMTS13 and 1.73 with standard therapy). Adverse events occurred in 71% of the patients with recombinant ADAMTS13 and in 84% with standard therapy. Adverse events that were considered by investigators to be related to the trial drug occurred in 9% of the patients with recombinant ADAMTS13 and in 48% with standard therapy. Trial-drug interruption or discontinuation due to adverse events occurred in no patients with recombinant ADAMTS13 and in 8 patients with standard therapy. No neutralizing antibodies developed during recombinant ADAMTS13 treatment. The mean maximum ADAMTS13 activity after recombinant ADAMTS13 treatment was 101%, as compared with 19% after standard therapy. CONCLUSIONS: During prophylaxis with recombinant ADAMTS13 in patients with congenital TTP, ADAMTS13 activity reached approximately 100% of normal levels, adverse events were generally mild or moderate in severity, and TTP events and manifestations were rare. (Funded by Takeda Development Center Americas and Baxalta Innovations; ClinicalTrials.gov number, NCT03393975.).

Recombinant ADAMTS13 for Hereditary Thrombotic Thrombocytopenic Purpura.

A 27-year-old patient with a history of severe obstetrical complications and arterial thrombosis received a diagnosis of hereditary thrombotic thrombocytopenic purpura (TTP) due to severe ADAMTS13 deficiency when she presented with an acute episode in the 30th week of her second pregnancy. When the acute episode of hereditary TTP became plasma-refractory and fetal death was imminent, weekly injections of recombinant ADAMTS13 at a dose of 40 U per kilogram of body weight were initiated. The patient's platelet count normalized, and the growth of the fetus stabilized. At 37 weeks 1 day of gestation, a small-for-gestational-age boy was delivered by cesarean section. At the time of this report, the patient and her son were well, and she continued to receive injections of recombinant ADAMTS13 every 2 weeks. (Funded by the Swiss National Science Foundation.).

From the Discovery of ADAMTS13 to Current Understanding of Its Role in Health and Disease.

ADAMTS13 (a disintegrin-like metalloprotease domain with thrombospondin type 1 motif, member 13) is a protease of crucial importance in the regulation of the size of von Willebrand factor multimers. Very low ADAMTS13 activity levels result in thrombotic thrombocytopenic purpura, a rare and life-threatening disease. The mechanisms involved can either be acquired (immune-mediated thrombotic thrombocytopenic purpura [iTTP]) or congenital (cTTP, Upshaw-Schulman syndrome) caused by the autosomal recessive inheritance of disease-causing variants (DCVs) located along the ADAMTS13 gene, which is located in chromosome 9q34. Apart from its role in TTP, and as a regulator of microthrombosis, ADAMTS13 has begun to be identified as a prognostic and/or diagnostic marker of other diseases, such as those related to inflammatory processes, liver damage, metastasis of malignancies, sepsis, and different disorders related to angiogenesis. Since its first description almost 100 years ago, the improvement of laboratory tests and the description of novel DCVs along the ADAMTS13 gene have contributed to a better and faster diagnosis of patients under critical conditions. The ability of ADAMTS13 to dissolve platelet aggregates in vitro and its antithrombotic properties makes recombinant human ADAMTS13 treatment a potential therapeutic approach targeting not only patients with cTTP but also other medical conditions.

Identify the influences of systemic lupus erythematosus on acquired ADAMTS13-deficient thrombotic thrombocytopenic purpura using comprehensive bioinformatics analysis.

BACKGROUND: The association between acquired ADAMTS13-deficient thrombotic thrombocytopenic purpura (aTTP) and systemic lupus erythematosus (SLE) has been studied; however, the underlying molecular causes remain poorly understood. This research aimed to employ bioinformatics approaches to elucidate potential molecular mechanisms contributing to the pathogenesis of SLE and aTTP. MATERIAL AND METHODS: The Gene Expression Omnibus (GEO) database yielded GSE121239 and GSE36418 to get mutual different expression genes (DEGs). Subsequently, DEGs were subjected to process Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Then, the DEGs were used for protein-protein interaction (PPI) analysis and screened for hub genes and drugs by the DGIDB drug database. RESULTS: A total of 87 DEGs between the SLE and TTP datasets were identified. In the GO and KEGG analyses, DEGs were mainly enriched in the "regulation of transcription by RNA polymerase II" and "signaling pathways regulating pluripotency of stem cells." After a PPI analysis, three hub genes (BMPR2, SMAD5, and ATF2) were identified. Finally, two drugs targeted to ATF2 were predicted by the DGIDB drug database. CONCLUSIONS: Three core genes were linked to the molecular pathogenesis of SLE and aTTP, and two drugs may be viable treatments for both diseases.

Inherited ADAMTS13 mutations associated with Thrombotic Thrombocytopenic Purpura: a short review and update.

ADAMTS13 is a plasma metalloprotease with the primary function of cleaving VWF to maintain hemostasis. Circulating ADAMTS13 is in the closed conformation until blood vessel injury triggers a VWF-dependant activation to the open active form of the protein. ADAMTS13 is a multi-domain protein with the domains broadly functioning to interact and cleave VWF or maintain global latency of ADAMTS13. Thrombotic Thrombocytopenic Purpura is a disease characterized by excessive thrombi formation in the microvasculature, diagnosis is made when ADAMTS13 activity is <10%. In the hereditary form, a variety of mutations are found throughout all domains of ADAMTS13, examples are given alongside details of each domain in this article. ADAMTS13 mutations can inhibit the binding and cleavage of VWF directly or indirectly through reduced secretion, leading to increased size of VWF multimers and platelet recruitment. Molecular characterization of ADAMTS13 may provide insight into the mechanisms of TTP to aid in both scientific and clinical research.

HLA loci predisposing to immune TTP in Japanese: potential role of the shared ADAMTS13 peptide bound to different HLA-DR.

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a rare autoimmune disorder caused by neutralizing anti-ADAMTS13 autoantibodies. In white individuals, HLA allele DRB1*11 is a predisposing factor for iTTP, whereas DRB1*04 is a protective factor. However, the role of HLA in Asians is unclear. In this study, we analyzed 10 HLA loci using next-generation sequencing in 52 Japanese patients with iTTP, and the allele frequency in the iTTP group was compared with that in a Japanese control group. We identified the following HLA alleles as predisposing factors for iTTP in the Japanese population: DRB1*08:03 (odds ratio [OR], 3.06; corrected P [Pc] = .005), DRB3/4/5*blank (OR, 2.3; Pc = .007), DQA1*01:03 (OR, 2.25; Pc = .006), and DQB1*06:01 (OR,: 2.41; Pc = .003). The estimated haplotype consisting of these 4 alleles was significantly more frequent in the iTTP group than in the control group (30.8% vs 6.0%; Pc < .001). DRB1*15:01 and DRB5*01:01 were weak protective factors for iTTP (OR, 0.23; Pc = .076; and OR, 0.23, Pc = .034, respectively). On the other hand, DRB1*11 and DRB1*04 were not associated with iTTP in the Japanese. These findings indicated that predisposing and protective factors for iTTP differ between Japanese and white individuals. HLA-DR molecules encoded by DRB1*08:03 and DRB1*11:01 have different peptide-binding motifs, but interestingly, bound to the shared ADAMTS13 peptide in an in silico prediction model.

Identification of a novel genetic locus associated with immune-mediated thrombotic thrombocytopenic purpura.

Immune thrombotic thrombocytopenic purpura (iTTP) is an ultra-rare, life-threatening disorder, mediated through severe ADAMTS13 deficiency causing multi-system micro-thrombi formation, and has specific human leukocyte antigen associations. We undertook a large genome-wide association study to investigate additional genetically distinct associations in iTTP. We compared two iTTP patient cohorts with controls, following standardized genome-wide quality control procedures for single-nucleotide polymorphisms and imputed HLA types. Associations were functionally investigated using expression quantitative trait loci (eQTL), and motif binding prediction software. Independent associations consistent with previous findings in iTTP were detected at the HLA locus and in addition a novel association was detected on chromosome 3 (rs9884090, P=5.22x10-10, odds ratio 0.40) in the UK discovery cohort. Meta-analysis, including the French replication cohort, strengthened the associations. The haploblock containing rs9884090 is associated with reduced protein O-glycosyltransferase 1 (POGLUT1) expression (eQTL P<0.05), and functional annotation suggested a potential causative variant (rs71767581). This work implicates POGLUT1 in iTTP pathophysiology and suggests altered post-translational modification of its targets may influence disease susceptibility.

COVID-19 vaccine (mRNA BNT162b2) and COVID-19 infection-induced thrombotic thrombocytopenic purpura in adolescents.

The mRNA COVID-19 vaccine and COVID-19 infection caused by the SARS-CoV-2 virus may be immunologic triggers for the development of thrombotic thrombocytopenic purpura (TTP). There is not yet literature that discusses TTP induced by COVID-19 vaccination or infection in pediatric or adolescent patients. We describe three adolescents presenting with TTP (both de novo and relapsed disease) following administration of the Pfizer COVID-19 vaccine or after COVID-19 infection. Our observations demonstrate that the Pfizer-BioNTech mRNA vaccine and COVID-19 infection can act as triggers for the development/relapse of both congenital and acquired TTP.

A Case Report of Congenital Thrombotic Thrombocytopenic Purpura: The Peripheral Blood Smear Lights the Diagnosis.

We report on a 12-year-old boy with congenital thrombotic thrombocytopenic purpura, on who had an erroneous diagnosis as chronic immune thrombocytopenia. The patient presented with complaints of jaundice and skin rash. Laboratory analysis showed nonimmune hemolytic anemia and severe thrombocytopenia. Peripheral blood smear showed 8% schistocytes, polychromasia, and anisocytosis. The ADAMTS13 antigen and activity were suspected to be lower than 5% with any antibodies against the enzyme. The DNA sequence analyses resulted in compound heterozygosity consisting of c.291_391del in exon 3 and c.4143dupA in exon 29. Schistocyte (fragmented erythrocytes) on the peripheral blood smear is a light that illuminates the diagnosis. Early recognition of the disease can prevent inappropriate treatments and morbidities due to organ damage.

Acquired Thrombotic Thrombocytopenic Purpura in a 5-Year-old Child With Wiskott-Aldrich Syndrome.

Thrombocytopenia is often seen as a laboratory finding during childhood. A supposed idiopathic thrombocytopenic purpura patient who was later diagnosed as Wiskott-Aldrich syndrome (WAS) and developed acquired thrombotic thrombocytopenic purpura (aTTP). Although autoimmune manifestations in WAS described, aTTP was reported just once. Five-year-old-boy was initially brought with cough, bloody stool (diarrhea), oral mucosal bleeding at 12th months of age. Following diagnosed with idiopathic thrombocytopenic purpura and receiving intravenous immunoglobulin, platelet count raised from 20,000 to 50,000/µL. One year after WAS diagnosis by mutation analysis, he presented with complaints of resistant fever, epistaxis, and melena. Hemoglobin decreased from 10 to 5.9 g/dL. Schistocytes in peripheral blood smear and high anti-ADAMTS-13 antibody level indicated development of aTTP.

Delayed diagnosis of congenital thrombotic thrombocytopenic purpura in a patient with recurrent strokes.

Congenital thrombotic thrombocytopenic purpura (cTTP) is caused by ADAMTS13 mutations and associated with high risk of microvascular thrombosis. A 58 year old female had an ischemic stroke during hormonal fertility, and a TIA a year after. She suffered another stroke 18 years later while on warfarin. Four months after she developed severe thrombocytopenia, mild anemia, and increased LDH. Blood film showed schistocytes. She was hospitalized with presumptive TTP. ADAMTS 13 activity was undetectable without inhibitor. She developed another stroke and received plasma exchange. A homozygote ADAMTS 13 mutation was identified. Despite plasma, the ADAMTS13 activity remained < 10% and she had another stroke. Recombinant ADAMTS13 therapy was obtained through compassionate use. She receives weekly infusions maintaining ADAMTS13 trough levels above 10% without thrombotic recurrences. This case underscores the need to recognize cTTP as a cause of cryptogenic strokes, and the diagnostic value of the peripheral blood film. rADAMTS13 replacement may prevent recurrences.

New missense mutation p.Trp387Ser affecting the functionally important TrpXXTrp motif in the TSR1 repeat of ADAMTS13 metalloproteinase: Case report.

Upshaw-Schulman syndrome (USS)-rare autosomal recessive disease that affects <1/1 000 000 individuals. It is characterized by the massive formation of platelet thrombi in the microcirculation accompanied by haemolytic anaemia, thrombocytopenia and clinical and laboratory signs of renal and neurological failure. USS is caused by mutations in the ADAMTS13 gene. Mutations in the ADAM metallopeptidase with thrombospondin type 1 motif 13  (ADAMTS13) gene can lead to disruption of secretion of this enzyme, or to decrease of enzyme proteinase activity without effect on ADAMTS13 secretion. The aim of this work is to describe a clinical case of USS caused by a new missense mutation in the ADAMTS13 gene. The diagnosis of thrombotic thrombocytopenic purpura was based on clinical signs and confirmed if plasma ADAMTS13 activity was <10%. ADAMTS13 gene sequencing was performed by the Sanger method using oligonucleotide primers of our own design. We found a new, undescribed mutation p.Trp387Ser in a TrpXXTrp motif. Previously, a pathogenic variation disrupting the 387TrpSerSerTrp390 motif of the ADAMTS13 protein was detected only once. Clinical picture of a patient with the combination of the p.Trp387Ser and p.Arg1060Trp variations is quite similar to that of the homozygous state of p.Arg1060Trp variant.

[Advance in the diagnosis and treatment of hereditary thrombotic thrombocytopenic purpura].

Congenital thrombotic thrombocytopenic purpura, also known as Upshaw-Schulman syndrome, is a rare autosomal recessive genetic disorder. The main pathogenesis is homozygous or compound heterozygous variants of von Willebrand factor lyase (ADAMTS13) gene mapped to chromosome 9q34, which may result in severe lack of ADAMTS13 which cleaves von Willebrand factor (vWF) multimers in the plasma and increase the risk of microvascular thrombosis, leading to various complications. The advance of research on the pathogenesis of cTTP, recombinant human ADAMTS13 and gene therapy have made breakthroughs which may lead to cure of cTTP. This article has provided a review for the latest progress made in the diagnosis and treatment of cTTP.

[Immune-mediated thrombotic thrombocytopenic purpura and susceptible HLA alleles].

Thrombotic thrombocytopenic purpura (TTP) is an extremely rare and fatal thrombotic disorder characterized by impaired enzyme activity of von Willebrand factor cleaving protease, also known as ADAMTS13. Immune-mediated TTP (iTTP) is an acquired form of TTP caused by the production of auto-antibodies against ADAMTS13. The pathophysiology of autoimmune disorders is multifactorial, with several human leukocyte antigen (HLA) alleles identified as a genetic risk factor for autoimmune diseases known as susceptible HLA. In the early 2010s, three distinct European groups revealed that DRB1*11 is one of the most susceptible alleles in acquiring iTTP among Caucasians based on HLA typing data. Several in silico predictions for allele-restricted ADAMTS13 epitopes against T cells are made in this context, followed by an in vitro validation employing mass spectrometry using eluted peptides and T-cell assays. However, similar analyses in a genetically distinct Japanese population have not yet been conducted. We used next-generation sequencing to perform HLA typing for 52 Japanese patients with iTTP from 19 institutes. Our detailed analysis revealed that the specific allele DRB1*08:03 was identified as a genetic risk factor for iTTP in Japanese patients, but there were no statistically significant differences in the allele frequency of DRB1*11 between iTTP and healthy controls.

Current prophylactic plasma infusion protocols do not adequately prevent long-term cumulative organ damage in the Japanese congenital thrombotic thrombocytopenic purpura cohort.

Congenital thrombotic thrombocytopenic purpura (cTTP), known as Upshaw-Schulman syndrome, is an ultrarare thrombotic disorder caused by ADAMTS13 gene mutations; however, its long-term outcomes have not been widely studied. A questionnaire survey was administered to physicians of patients in the Japanese cTTP registry to characterise these outcomes. We analysed 55 patients in remission, with 41 cases receiving prophylactic fresh frozen plasma (FFP; median dosage: 13·2 ml/kg per month) and 14 receiving on-demand FFP. Patients receiving prophylactic FFP were considered as having a more severe form of the disease and had lower platelet counts and higher serum creatinine levels than those receiving on-demand FFP (median 138 × 109 /l vs. 243 × 109 /l, P = 0·003 and 0·71 mg/dl vs 0·58 mg/dl, P = 0·009, respectively). Patients who received prophylactic FFP more commonly developed organ damage, including renal impairment, cerebral infarctions, and cardiac hypofunction, than those who did not. Adverse FFP-related events were seen in 78% of the prophylactic FFP group, with allergic reactions being most common. Since current protocols for FFP administration to the prophylactic FFP group in Japan may be insufficient for preventing cumulative organ damage, a higher dosage of ADAMTS13 supply using recombinant ADAMTS13 agent is needed in these patients.

Consumption of complement in a 26-year-old woman with severe thrombotic thrombocytopenia after ChAdOx1 nCov-19 vaccination.

Extremely rare reactions characterized by thrombosis and thrombocytopenia have been described in subjects that received ChAdOx1 nCoV-19 vaccination 5-16 days earlier. Although patients with vaccine-induced thrombotic thrombocytopenia (VITT) have high levels of antibodies to platelet factor 4 (PF4)-polyanion complexes, the exact mechanism of the development of thrombosis is still unknown. Here we reported serum studies as well as proteomics and genomics analyses demonstrating a massive complement activation potentially linked to the presence of anti-PF4 antibodies in a patient with severe VITT. At admission, complement activity of the classical and lectin pathways were absent (0% for both) with normal levels of the alternative pathway (73%) in association with elevated levels of the complement activation marker sC5b-9 (630 ng/mL [n.v. 139-462 ng/mL]) and anti-PF4 IgG (1.918 OD [n.v. 0.136-0.300 OD]). The immunoblotting analysis of C2 showed the complete disappearance of its normal band at 110 kDa. Intravenous immunoglobulin treatment allowed to recover complement activity of the classical pathway (91%) and lectin pathway (115%), to reduce levels of sC5b-9 (135 ng/mL) and anti-PF4 IgG (0.681 OD) and to normalize the C2 pattern at immunoblotting. Proteomics and genomics analyses in addition to serum studies showed that the absence of complement activity during VITT was not linked to alterations of the C2 gene but rather to a strong complement activation leading to C2 consumption. Our data in a single patient suggest monitoring complement parameters in other VITT patients considering also the possibility to target complement activation with specific drugs.

Characterization and treatment of congenital thrombotic thrombocytopenic purpura.

Congenital thrombotic thrombocytopenic purpura (cTTP) is an ultra-rare thrombomicroangiopathy caused by an inherited deficiency of a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13). There are limited data on genotype-phenotype correlation; there is no consensus on treatment. We reviewed the largest cohort of cTTP cases, diagnosed in the United Kingdom, over the past 15 years. Seventy-three cases of cTTP were diagnosed, confirmed by genetic analysis. Ninety-three percent were alive at the time of review. Thirty-six percent had homozygous mutations; 64% had compound heterozygous mutations. Two presentation peaks were seen: childhood (median diagnosis age, 3.5 years) and adulthood, typically related to pregnancy (median diagnosis age, 31 years). Genetic mutations differed by age of onset with prespacer mutations more likely to be associated with childhood onset (P = .0011). Sixty-nine percent of adult presentations were associated with pregnancy. Fresh-frozen plasma (FFP) and intermediate purity factor VIII concentrate were used as treatment. Eighty-eight percent of patients with normal blood counts, but with headaches, lethargy, or abdominal pain, reported symptom resolution with prophylactic therapy. The most common currently used regimen of 3-weekly FFP proved insufficient for 70% of patients and weekly or fortnightly infusions were required. Stroke incidence was significantly reduced in patients receiving prophylactic therapy (2% vs 17%; P = .04). Long-term, there is a risk of end-organ damage, seen in 75% of patients with late diagnosis of cTTP. In conclusion, prespacer mutations are associated with earlier development of cTTP symptoms. Prophylactic ADAMTS13 replacement decreases the risk of end-organ damage such as ischemic stroke and resolved previously unrecognized symptoms in patients with nonovert disease.

Unfolding the pathophysiology of congenital thrombotic thrombocytopenic purpura in pregnancy: lessons from a cluster of familial cases.

BACKGROUND: Thrombotic thrombocytopenic purpura (TTP), a rare, potentially life-threatening thrombotic microangiopathy, manifests either as congenital TTP or acquired forms. It is caused by the absence or severe depletion of a disintegrin and metalloproteinase with thrombospondin motifs 13 (ADAMTS13) protease, leading to the accumulation of ultra large von Willebrand factor multimers as well as extensive platelet adhesion and clumping, which can ultimately cause severe secondary end-organ damage. Pregnancy can provoke or exacerbate TTP, leading to maternal and fetal complications. OBJECTIVE: In this report, we focused on pregnancy outcomes in a recently recognized cohort of congenital TTP patients of Bedouin Arab descent in southern Israel who were all homozygous for a novel c.3772delA variant of the ADAMTS13 gene, leading to the clinical manifestations of TTP largely during pregnancy. STUDY DESIGN: All patients presented in this study belong to 2 closely related families of Arab Bedouin descent and were found to be homozygous for a novel ADAMTS13-c.3772delA variant. The cohort consisted of 19 females; 16 of them had congenital TTP and had been pregnant and were thus included. Patient data were collected from electronic medical records. RESULTS: Of note, 13 women from our cohort, who delivered 14 fetuses (owing to 1 twin pregnancy), were diagnosed with congenital TTP following complicated pregnancies, which included recurrent pregnancy loss, stillbirth, early onset preeclampsia (both mild and severe), hemolysis, elevated liver enzymes and low platelet count syndrome, intrauterine growth restriction with abnormal Doppler flow, preterm premature rupture of membranes, and a total perinatal mortality rate of 30.7% (4/13). An additional 3 women, who were diagnosed owing to complications outside of pregnancy and at older ages, experienced TTP during their pregnancies, which occurred before diagnosis. Subsequent pregnancies were treated with fresh frozen plasma leading to a 100% fetal survival rate in the pregnancies that reached fetal viability. All placentas had lesions consistent with maternal vascular underperfusion. However, the severity and frequency of these lesions were lower in the 8 placentas from pregnancies treated with fresh frozen plasma. CONCLUSION: This case series details a distinctive cohort of congenital TTP patients, all homozygous for the same, novel ADAMTS13 variant, who presented with clinical complications during pregnancy and maternal vascular lesions of underperfusion in the placenta. Our findings imply that the variant identified in the ADAMTS13 gene in our cohort may have a specific functional impact on the placenta, and that treatment with fresh frozen plasma during pregnancy ameliorates the course of the disease, leading to a milder phenotype or a normal pregnancy in the majority of cases.