Carfilzomib-associated thrombotic microangiopathy: clinical features and outcomes.

BACKGROUND AND HYPOTHESIS: Carfilzomib, a new proteasome inhibitor indicated for patients with relapsed/refractory myeloma, has been associated with cases of thrombotic microangiopathy (CFZ-TMA). The role of variants in the complement alternative pathway and therapeutic potential of complement blockade with eculizumab remain to be determined. METHODS: We report 37 cases of CFZ-TMA recorded in the French reference center for TMA with their clinical characteristics, genetic analysis and outcome according to treatments. RESULTS: A trigger was identified in more than half of cases, including 8 influenza and 5 SARS-CoV-2 cases. All patients presented with acute kidney injury (AKI) (KDIGO stage 3 in 31 (84%) patients) while neurological (n=13, 36%) and cardiac damage (n=7, 19%) were less frequent. ADAMTS13 and complement activity were normal (n= 28 and 18 patients tested) and no pathogenic variant in the alternative complement pathway was found in 7 patients tested.TMA resolved in most (n=34, 94%) patients but 12 (44%) still displayed stage 3 AKI at discharge. Nineteen (51%) patients were treated with therapeutic plasma exchange, 14 (38%) patients received corticosteroids and 18 (50%) were treated with eculizumab. However none of these treatments demonstrated a significant impact on outcomes. CONCLUSION: This study is the largest case series of CFZ-TMA since its approval in 2012. Patients present with severe AKI and experience frequent sequelae. Complement variants and blockade therapy do not seem to play a role in the pathophysiology and prognosis of the disease.

Caplacizumab: A game changer also in pregnancy-associated immune-mediated thrombotic thrombocytopenic purpura?

Therapeutic options in immune-mediated thrombotic thrombocytopenic purpura (iTTP) during pregnancy are limited besides therapeutic plasma exchange (TPE) and corticosteroids. The report by Odetola et al. suggests that caplacizumab represents a reasonable option in iTTP during pregnancy, especially when the disease is not rapidly controlled with the standard TPE-corticosteroid association. Commentary on: Odetola et al. Safe and effective use of caplacizumab in pregnancy-related acquired thrombotic thrombocytopenic purpura. Br J Haematol 2023;202:879-882.

TTP: From empiricism for an enigmatic disease to targeted molecular therapies.

The 100th anniversary of the first description of Thrombotic Thrombocytopenic Purpura (TTP) as a disease by Dr. Eli Moschcowitz approaches. For many decades, TTP remained mostly a mysterious fatal condition, where diagnosis was often post-mortem. Initially a pentad of symptoms was identified, a pattern that later revealed to be fallible. Sporadic observations led to empiric interventions that allowed for the first impactful breakthrough in TTP treatment, almost 70 years after its first description: the introduction of plasma exchange and infusions as treatments. The main body of knowledge within the field was gathered in the latest three decades: patient registries were set and proved crucial for advancements; the general mechanisms of disease have been described; the diagnosis was refined; new treatments and biomarkers with improvements on prognosis and management were introduced. Further changes and improvements are expected in the upcoming decades. In this review, we provide a brief historic overview of TTP, as an illustrative example of the success of translational medicine enabling to rapidly shift from a management largely based on empiricism to targeted therapies and personalized medicine, for the benefit of patients. Current management options and present and future perspectives in this still evolving field are summarized.

Open ADAMTS13, induced by antibodies, is a biomarker for subclinical immune-mediated thrombotic thrombocytopenic purpura.

Recently, we showed that ADAMTS13 circulates in an open conformation during the acute phase of immune-mediated thrombotic thrombocytopenic purpura (iTTP). Although the cause of this conformational change remains elusive, ADAMTS13 is primarily closed in iTTP patients in remission with ADAMTS13 activity >50% and undetectable anti-ADAMTS13 autoantibodies, as well as after rituximab treatment, suggesting a role for anti-ADAMTS13 autoantibodies. Therefore, immunoglobulin G from 18 acute iTTP patients was purified and added to closed ADAMTS13 in healthy donor plasma. This resulted in open ADAMTS13 in 14 of 18 (78%) samples, proving that anti-ADAMTS13 autoantibodies can induce an open ADAMTS13 conformation. To further elucidate the conformation of ADAMTS13 in iTTP patients, we studied a novel iTTP patient cohort (n = 197) that also included plasma samples from iTTP patients in remission in whom ADAMTS13 activity was <50%. The open ADAMTS13 conformation was found during acute iTTP, as well as in patients in remission with ADAMTS13 activity <50% and in half of the patients with ADAMTS13 activity >50%, although free anti-ADAMTS13 autoantibodies were not always detected. Thus, open ADAMTS13 is a hallmark of acute iTTP, as well as a novel biomarker that can be used to detect subclinical iTTP in patients in remission. Finally, a long-term follow-up study in 1 iTTP patient showed that the open conformation precedes a substantial drop in ADAMTS13 activity. In conclusion, we have shown that anti-ADAMTS13 autoantibodies from iTTP patients induce an open ADAMTS13 conformation. Most importantly, an open ADAMTS13 conformation is a biomarker for subclinical iTTP and could become an important tool in TTP management.

Severe HELLP syndrome masquerading as thrombocytopenic thrombotic purpura: a case report.

BACKGROUND: Thrombotic microangiopathies (TMAs) occurring in the postpartum period may be difficult to manage. They present as the combination of mechanical hemolytic anemia and consumption thrombocytopenia due to endothelial dysfunction. The cause of this endothelial aggression can be multiple: thrombocytopenic thrombotic purpura (TTP), HELLP syndrome, antiphospholipid syndrome, atypical hemolytic and uremic syndrome or acute fatty liver of pregnancy. TTP results from a severe deficiency of ADAMTS13, which is a protease cleaving specifically von Willebrand factor chiefly produced by liver cells. There are two main causes, the production of anti-ADAMTS13 auto-antibodies and, more rarely, a genetic deficiency in ADAMTS13. First-line treatment is based on plasma exchange. HELLP syndrome occurs in the third trimester of pregnancy usually in association with preeclampsia and represents a form of TMA characterized by damage to the sinusoidal capillaries of the liver. Prompt delivery is the main treatment. We present a case illustrating the challenges in discriminating between different postpartum TMAs, with a focus on the distinction between TTP and HELLP syndrome. Specifically, we highlight how acute liver failure (ALF) stemming from HELLP may lead to TTP with a spectacular response to plasma exchanges. CASE: A 28-year-old, 33 + 4 weeks pregnant woman presented with severe preeclampsia complicated by ALF in the setting of partial liver necrosis, disseminated intravascular coagulation, microangiopathic hemolytic anemia and acute kidney injury. Greatly diminished levels of ADAMTS13 (< 5%) activity and neurological impairment suggested an initial diagnosis of thrombotic thrombocytopenic purpura (TTP). Therapeutic plasma exchange (TPE) was initiated and complete renal, neurological, hematological and hepatic recovery was observed. Secondary TTP induced by ALF due to HELLP syndrome was the final diagnosis. CONCLUSION: Our case addresses the overlapping nature of postpartum TMAs and raises the possibility that HELLP-induced ALF may constitute an additional mechanism resulting in TTP, thereby opening a possible indication for TPE.

Thrombotic thrombocytopenic purpura.

Thrombotic thrombocytopenic purpura (TTP) is a rare and life-threatening thrombotic microangiopathy characterized by microangiopathic hemolytic anemia, severe thrombocytopenia, and organ ischemia linked to disseminated microvascular platelet rich-thrombi. TTP is specifically related to a severe deficiency in ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13), the specific von Willebrand factor-cleaving protease. ADAMTS13 deficiency is most frequently acquired via ADAMTS13 autoantibodies, but rarely, it is inherited via mutations of the ADAMTS13 gene. The first acute episode of TTP usually occurs during adulthood, with a predominant anti-ADAMTS13 autoimmune etiology. In rare cases, however, TTP begins as soon as childhood, with frequent inherited forms. TTP is ∼2-fold more frequent in women, and its outcome is characterized by a relapsing tendency. Rapid recognition of TTP is crucial to initiate appropriate treatment. The first-line therapy for acute TTP is based on daily therapeutic plasma exchange supplying deficient ADAMTS13, with or without steroids. Additional immune modulators targeting ADAMTS13 autoantibodies are mainly based on steroids and the humanized anti-CD20 monoclonal antibody rituximab. In refractory or unresponsive TTP, more intensive therapies including twice-daily plasma exchange; pulses of cyclophosphamide, vincristine, or cyclosporine A; or salvage splenectomy are considered. New drugs including N-acetylcysteine, bortezomib, recombinant ADAMTS13, and caplacizumab show promise in the management of TTP. Also, long-term follow-up of patients with TTP is crucial to identify the occurrence of other autoimmune diseases, to control relapses, and to evaluate psychophysical sequelae. Further development of both patients' registries worldwide and innovative drugs is still needed to improve TTP management.

Generation of anti-idiotypic antibodies to detect anti-spacer antibody idiotopes in acute thrombotic thrombocytopenic purpura patients.

In autoantibody-mediated autoimmune diseases, autoantibody profiling allows patients to be stratified and links autoantibodies with disease severity and outcome. However, in immune-mediated thrombotic thrombocytopenic purpura (iTTP) patients, stratification according to antibody profiles and their clinical relevance has not been fully explored. We aimed to develop a new type of autoantibody profiling assay for iTTP based on the use of anti-idiotypic antibodies. Anti-idiotypic antibodies against 3 anti-spacer autoantibodies were generated in mice and were used to capture the respective anti-spacer idiotopes from 151 acute iTTP plasma samples. We next deciphered these anti-spacer idiotope profiles in iTTP patients and investigated whether these limited idiotope profiles could be linked with disease severity. We developed 3 anti-idiotypic antibodies that recognized particular idiotopes in the anti-spacer autoantibodies II-1, TTP73 or I-9, that are involved in ADAMTS13 binding; 35%, 24% and 42% of patients were positive for antibodies with the II-1, TTP73 and I-9 idiotopes, respectively. Stratifying patients according to the corresponding 8 anti-spacer idiotope profiles provided a new insight into the anti-spacer II-1, TTP73 and I-9 idiotope profiles in these patients. Finally, these limited idiotope profiles showed no association with disease severity. We successfully developed 3 anti-idiotypic antibodies that allowed us to determine the profiles of the anti-spacer II-1, TTP73 and I-9 idiotopes in iTTP patients. Increasing the number of patients and/or future development of additional anti-idiotypic antibodies against other anti-ADAMTS13 autoantibodies might allow idiotope profiles of clinical, prognostic value to be identified.

Inherited Thrombotic Thrombocytopenic Purpura Revealed by Recurrent Strokes in a Male Adult: Case Report and Literature Review.

Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy related to a severe deficiency of ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13). In this article, we describe the first case of a young male adult suffering from a hereditary TTP revealed by recurrent strokes, relapsing despite antiplatelet and anticoagulant therapy. Because of the persistent moderate thrombocytopenia, plasmatic ADAMTS13 activity was investigated and was found lower than 5% in the absence of anti-ADAMTS13 IgG. Direct sequencing of ADAMTS13 gene led to the diagnosis of Upschaw-Schulman syndrome (USS). Inherited TTP or USS is a rare autosomal recessive inherited disease leading to a severe deficiency of ADAMTS13 mostly beginning in childhood or in young female adult during pregnancy. Our patient was treated with fresh frozen plasma every 2 weeks. One year after diagnosis, he was free of neurological symptoms. Around 12 cases of inherited TTP diagnosed in adults (outside pregnancy) are described in literature. Only 4 of them exhibited a stroke. This case is the first late onset genetic TTP revealed by recurrent strokes, moderate thrombocytopenia without anemia.

Pediatric thrombotic thrombocytopenic purpura.

Child-onset thrombotic thrombocytopenic purpura (TTP) is a rare entity of thrombotic microangiopathy (TMA). The pathophysiology of the disease is based on a severe functional deficiency of ADAMTS13 (activity <10%), the specific von Willebrand factor (VWF)-cleavage protease. This deficiency may be either acquired (associated anti-ADAMTS13 autoantibodies) or congenital (resulting from biallelic mutations of ADAMTS13 gene). ADAMTS13 deficiency is responsible for the accumulation of high molecular weight multimers of VWF and the formation of platelet thrombi in the microcirculation. Consequently, microangiopathic hemolytic anemia and consumption thrombocytopenia are associated with organ ischemia. The differential diagnosis with other TMAs, autoimmune cytopenias or hematological malignancies may be challenging. The exploration of ADAMTS13 (activity, antibodies, antigen, ADAMTS13 gene) supports the diagnosis of TTP. The first-line treatment of the acute phase of TTP is based on plasmatherapy. In congenital TTP, patients with a chronic disease benefit from a prophylactic plasmatherapy. In autoimmune TTP, steroids and B-cells depleting therapies increasingly are used together with plasma exchange. Long-term follow-up including the monitoring of ADAMTS13 activity is mandatory. A severe decrease in ADAMTS13 activity (<10%) may predict relapses and preemptive B-cell depletion with rituximab can be used to prevent relapses.

Thrombin generation test as a marker for high risk venous thrombosis pregnancies.

Pregnancy is a well-established risk factor for venous thromboembolism and is associated with a state of hypercoagulability. The use of sensitive and specific biological markers to predict risk factors for thrombosis is essential during pregnancy. Our objective was to investigate the usefulness of thrombin generation test (TGT) as a marker to predict the risk of thrombosis in high risk venous thrombosis (HRVT) pregnancies compared to normal pregnancies. This retrospective study enrolled 134 women with HRVT pregnancies, 78 of whom had monozygotic, spontaneous and untreated pregnancies and formed the study group. The control group comprised 106 women with normal pregnancies. Routine assessment of coagulation activation markers: fibrinogen, D-dimer, prothrombin fragments 1 + 2 (F1 + 2), thrombin-antithrombin complexes (TAT) and fibrin monomer complexes (FMC) was performed every 5 weeks in the study group to detect a possible pathological state of hypercoagulability. TGT was performed using platelet-free plasma, 1 and 5 pM tissue factor (TF), supplemented by phospholipids (PL) ± thrombomodulin. Fibrinogen, D-dimer, F1 + 2, and TAT, but not FMC, increased significantly throughout pregnancy in both groups but no difference was shown between the groups. TGT showed an early increase in thrombin generation in both groups, which stabilized during the second month of pregnancy. No correlation was demonstrated between thrombin generation parameters and coagulation activation markers. Based on our results, TGT did not prove conclusive as a marker to predict the risk of thrombosis in HRVT pregnancies. Finding a sensitive and specific biological marker to predict thrombosis risk requires further investigation.

Management and follow-up of pregnancy-onset thrombotic thrombocytopenic purpura: the French experience.

ABSTRACT: Pregnancy-onset thrombotic thrombocytopenic purpura (TTP) is a rare and life-threatening disease of which diagnosis and management requires experienced multidisciplinary teams. The mechanisms responsible for a deficiency in the disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13 (ADAMTS13) leading to pregnancy-onset TTP may be congenital or acquired, and studying ADAMTS13 conformation could be of interest. The differential diagnosis between TTP and other pregnancy-associated thrombotic microangiopathies (TMA) is often challenging. Our retrospective multicenter study highlights the significance and the challenges associated with pregnancy-onset TTP and childbirth in terms of diagnosis, obstetric management, and follow-up aspects. Among 1174 pregnancy-onset TMA enrolled in the French Registry for TMA from 2000 to 2020, we identified 108 pregnancy-onset TTP: 52 immune-mediated TTP (iTTP, 48.1%), 27 acquired TTP of unidentified mechanism (uTTP, 25%), and 29 congenital TTP (cTTP, 26.9%). Data show that maternal outcome is good (survival rate: 95%) and fetal outcome is linked to the gestational age at the onset of the disease (survival rate: 75.5%). Three distinct entities with different natural histories emerged: pregnancy-onset iTTP appears similar to idiopathic iTTP, with an open ADAMTS13 conformation, and is marked by a relapse risk independent of subsequent pregnancies; pregnancy-onset uTTP appears to have a different pathophysiology with an unexpected open ADAMTS13 conformation and a very low relapse risk independent of subsequent pregnancies; finally, pregnancy-onset cTTP is characterized by the necessity of pregnancy as a systematic and specific trigger and a need for prophylactic plasmatherapy for subsequent pregnancies. This trial was registered at www.clinicaltrials.gov as #NCT00426686, and at the Health Authority and the French Ministry of Health (P051064/PHRC AOM05012).

Hemophagocytic lymphohistiocytosis is associated with deficiency and closed conformation of ADAMTS-13.

Background: A disintegrin and metalloprotease with thrombospondin type 1 repeats, member 13 (ADAMTS-13) is the specific von Willebrand factor-cleaving protease and circulates in a closed and latent conformation due to a spacer/CUB1 domain interaction. ADAMTS-13 is allosterically activated after binding of its substrate or antibodies, inducing an open conformation. Recently, we suggested a potential role of plasmin (fibrinolysin) in hemostasis disorders reported in most patients with hemophagocytic lymphohistiocytosis (HLH), a rare and life-threatening condition related to a severe systemic inflammatory state. Most patients with HLH had a partial ADAMTS-13 deficiency, and plasmin could induce a truncation of the C-terminal part of ADAMTS-13 and thus an open conformation. Objectives: To understand the effect of plasmin on ADAMTS-13, our study aimed to investigate ADAMTS-13 conformation in patients with HLH. Methods: Forty-five critically ill patients with HLH were prospectively enrolled between April 2015 and December 2018. ADAMTS-13 activity was measured by fluorescent resonance energy transfer-VWF73 assay, ADAMTS-13 antigen, and conformation with our homemade 3H9-enzyme-linked immunosorbent assay and 1C4-enzyme-linked immunosorbent assay. Results: ADAMTS-13 activity ranged from <10 to 65 IU/dL, and 41 of the 45 patients had a quantitative deficiency in ADAMTS-13 (activity <50 IU/dL). Twenty patients had a severe ADAMTS-13 deficiency (activity <20 IU/dL). ADAMTS-13 conformation was folded in all patients under normal conditions. Surprisingly, the switch of ADAMTS-13 conformation expected with the monoclonal antibody 17G2 (anti-CUB1) was disturbed in 6 patients (activity <20 IU/dL). Conclusion: Our study reported that ADAMTS-13 conformation is closed in HLH and provides an indirect proof that plasmin is not able to massively degrade ADAMTS-13. Further studies on glycosylation and citrullination profiles of ADAMTS-13 are needed to understand their role in HLH.

Diagnosis of thrombotic thrombocytopenic purpura: easy-to-use fiber optic surface plasmon resonance immunoassays for automated ADAMTS-13 antigen and conformation evaluation.

BACKGROUND: Laboratory diagnosis of immune-mediated thrombotic thrombocytopenic purpura (iTTP) remains challenging when ADAMTS-13 activity ranges between 10% and 20%. To prevent misdiagnosis, open ADAMTS-13 conformation gained clinical attention as a novel biomarker, especially to diagnose acute iTTP in patients with diagnostic undecisive ADAMTS-13 activity. Plasma ADAMTS-13 conformation analysis corrects for ADAMTS-13 antigen, with both parameters being characterized in enzyme-linked immunosorbent assay (ELISA)-based reference assays requiring expert technicians. OBJECTIVES: To design ADAMTS-13 antigen and conformation assays on automated, easy-to-use fiber optic surface plasmon resonance (FO-SPR) technology to promote assay accessibility and diagnose challenging iTTP patients. METHODS: ADAMTS-13 antigen and conformation assays were designed on FO-SPR technology. Plasma of 20 healthy donors and 20 acute iTTP patients were quantified, and data from FO-SPR and ELISA reference assays were compared. RESULTS: Following assay design, both antigen and conformation FO-SPR assays were optimized and characterized, presenting strong analytical sensitivity (detection limit of 0.001 µg/mL) and repeatability (interassay variation of 14.4%). Comparative analysis suggested positive correlation (Spearman r of 0.92) and good agreement between FO-SPR and ELISA assays. As expected, FO-SPR assays showed a closed or open ADAMTS-13 conformation in healthy donors and acute iTTP patients, respectively. CONCLUSION: Both ADAMTS-13 antigen and conformation assays were transferred onto automated, easy-to-use FO-SPR technology, displaying potent analytical sensitivity and reproducibility. ADAMTS-13 antigen and conformation were determined for healthy donors and acute iTTP patients showing strong correlation with ELISA reference. Introducing FO-SPR technology in clinical context could support routine diagnosis of acute iTTP patients, notably when ADAMTS-13 activity fluctuates between 10% and 20%.