Platelet Apoptosis and PAI-1 Content Are Involved in the Procoagulant Profile of Immune Thrombocytopenia Patients Responders to Agonists of Thrombopoietin Receptor.

Abstract Background: The treatment goal for patients with immune thrombocytopenia (ITP) is to raise platelet counts to levels that minimize or stop bleeding. Thrombopoietin receptor agonists (TPO-RAs) have been successfully and extensively employed as second-line therapy for ITP. TPO-RAs, however, have a small but significant increase in the risk of thrombosis. Aim: The aim of this study was to elucidate the mechanisms involved in the procoagulant effect of TPO-RAs. Methods: This is a prospective, observational and transversal study. Eighty-two patients with chronic primary ITP, 40 without treatment for at least six months (UT-ITP) and 42 responders to TPO-RA therapy (64.3% with eltrombopag and 35.7 % with romiplostim) were recruited. One hundred and twelve healthy participants were also included. ROTEM® (naTEM test: only recalcification) was performed on platelet rich plasma adjusted to a platelet count of 25 x 109/L. Clotting time (CT, time from start of measurement until 2 mm of amplitude [in seconds], alpha angle, which reflects the rate of fibrin polymerisation (tangent to the curve at 2 mm amplitude [in degrees]), maximum clot firmness, which reflects the maximum tensile strength of the thrombus (MCF, [in mm]) and LI60, which describes the percentage of maximum clot strength present at 60 min (in %), were recorded. Surface exposure of phosphatidylserine (PS), active caspase-3, -8 or -9 and prothrombinase complex binding to platelets were assessed by flow cytometry. Plasma and platelet levels of PAI-1 were determined by ELISA (eBioscience Ltd., Hatfield, United Kingdom). The effect of TPO and romiplostim on PAI-1 content of MEG-01 cells was evaluated by Western blot. Three MEG-01 cell cultures were initiated simultaneously: control without drugs and treated with either TPO (100 ng/mL) or romiplostim (53 μg/mL). Samples were collected at the start and after 24, 48 and 72 hours to determine the PAI-1 content. The statistical analysis was performed using SPSS 9.0 software (SPSS Inc., Chicago, Illinois, USA). Results: The ROTEM® studies showed significant differences in the dynamics of clot formation when comparing the control with ITP samples. There was a delay in clot formation in the UT-ITP group, as observed by a prolonged CT [expressed as median (p25-p75): control: 516 (490- 633) s; UT-ITP: 938 (914-1348) s, p<0.001], and a diminished alpha angle (mean±SD; control: 61.7±5.6 degrees; UT-ITP: 49.2±7.3 degrees, p<0.05). Nevertheless, samples from patients with UT-ITP reached the same MCF as those from healthy controls (control: 45.3±2.4 mm; UT-ITP: 46.9±3.7 mm). On the other hand, patients with ITP undergoing TPO-RA therapy presented an initial clot formation similar to that of the control group [expressed as median (p25-p75): CT, 672 (598-928) s; alpha angle, 55.8±5.8 degrees] but achieved a higher MCF (53.1±4.5 mm, p<0.05) and a reduced clot lysis after 60 min (control: 91.8±4.0%; UT-ITP: 93.7±4.0%, TPO-RA ITP: 97.6±1.7, p<0.05). Higher values of MCF observed with platelets from ITP patients treated with TPO-RAs might be a consequence of their augmented apoptosis signs: platelets from this group exposed more PS than controls and this situation was accompanied by an increased activity of caspases-3,7, -8 and -9 (Figure 1 A and B). Moreover, platelets from ITP patients on treatment with TPO-RAs bound more prothrombinase complex than platelets from UT-ITP patients and healthy controls (Figure 1 C). Reduced clot lysis observed in ITP patients treated with TPO-RA was due, at least in part, to increased plasma and platelet levels of PAI-1 (Table 1). Increase in platelet content of PAI-1 might be the result of the effect of TPO-RAs during megakaryopoiesis since treatments of MEG-01 cells with TPO or romiplostim induced a 3-fold increase in their endogenous PAI-1 content after an incubation period of 48 hs. Conclusion: The patients with ITP undergoing TPO-RAs therapy presented a procoagulant profile due to the formation of a more fibrinolysis-resistant clot because of increased platelet and plasma PAI-1 levels. Moreover, platelets from this group of patients showed more signs of apoptosis that causes a higher exposure of PS and, consequently, a larger surface for the binding of the prothrombinase complex. Work supported by grant from FIS-FEDER PI15/01457. NB holds a Miguel Servet II (FIS-FEDER CP14/00024). Disclosures Álvarez-Roman: SOBI: Consultancy; NovoNordisk: Consultancy; Shire: Consultancy. Jimenez-Yuste:Grifols: Consultancy, Research Funding; Octapharma: Consultancy, Research Funding; CSL Behring: Consultancy; Bayer: Consultancy, Research Funding; Roche: Consultancy, Research Funding; Shire: Consultancy, Research Funding; Sobi: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; NovoNordisk: Consultancy, Research Funding. Butta:FIS-Fondos FEDER: Research Funding.

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Delayed Plasma Clot Lysis in Adult Patients with Primary Immune Thrombocytopenia (ITP)

Blood ◽

10.1182/blood-2021-152261 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 3162-3162

Author(s):

Theresa Schramm ◽

Jennifer Machacek ◽

Michael Fillitz ◽

Barbara Dixer ◽

Peter Quehenberger ◽

...

Keyword(s):

Research Funding ◽

Immune Thrombocytopenia ◽

Clot Lysis ◽

Lag Phase ◽

Healthy Controls ◽

Plasma Clot ◽

Significant Difference ◽

Primary Immune Thrombocytopenia ◽

Pai 1 ◽

Bleeding Severity

Abstract Introduction: Primary immune thrombocytopenia (ITP) is an orphan disease characterized by very low platelet counts. Patients have heterogeneous bleeding phenotypes, which are not only determined by platelet counts, also a paradoxically increased thrombotic risk has been observed. Aim: To investigate, whether the fibrinolysis inhibitors plasminogen activator inhibitor-1 (PAI-1) and α2-antiplasmin are associated with impaired plasma clot lysis in primary ITP patients in comparison to non-immunologic thrombocytopenic controls (TPC) and healthy controls (HC). Furthermore, associations with bleeding severity and previous thrombotic events were investigated. Methods: Patients from the Vienna ITP biobank (EC 1843/2016), a multi-centric study including adult patients with primary ITP were investigated and compared to age- and sex-matched control groups: TPC with thrombocytopenia after chemotherapy and HC. Informed consent was obtained from all individuals before study inclusion. A clot formation and lysis assay (CLA) was performed according to the recommendations of the ISTH SSC. Platelet poor plasma samples were measured in duplicates for each patient and control. PAI-1 (PAI-1 Actibind ELISA, Technoclone, Vienna, Austria) and α2-antiplasmin by the chromogenic STA Stachrom antiplasmin assay (Diagnostic Stago, Asnieres, France) were measured. Bleeding severity was measured using the ITP-specific ITP-ISTH BAT (Rodeghiero et al. 2013). Results: In total, 37 primary ITP patients, 18 TPC and 156 healthy controls were analyzed (Table 1). Primary ITP patients had a higher BMI than HC. Bleeding severity was higher and more ITP patients had a thrombosis history compared to HC, whereas there was no difference in comparison to TPC. PAI-1 activity was highest in ITP patients, with a statistically significant difference in comparison to HC. α2-antiplasmin activity was higher in ITP patients than in TPC, whereas there was no difference in comparison to HC. After adjustment for sex, age, BMI and fibrinogen, primary ITP patients had a reduced clot formation rate (V max) and significantly delayed plasma clot lysis compared to TPC and HC (Table 2). Also, the lag phase and time to peak absorbance (TTP) were prolonged with a significant difference in comparison to HC. To investigate outliers of PAI-1 and α2-antiplasmin, we calculated cut-offs at the 75 th percentile of healthy controls (PAI-1: ≥ 3.1 U/mL, α2-antiplasmin: ≥ 107.0 %). 14 (37.8 %) ITP patients had PAI-1 levels and 10 (27.0 %) ITP patients had α2-antiplasmin activity above the cut-off. ITP patients with high PAI-1 levels had mildly delayed clot lysis in comparison to those below with a significantly lower maximal lysis rate (mLR). ITP patients with α2-antiplasmin activity above the cut-off had a significantly shorter lag phase, faster V max and shorter TTP than patients below the cut-off, whereas there was no difference in clot lysis. No differences between ITP patients above or below the respective cut-offs of PAI-1 and α2-antiplasmin regarding their bleeding severity and thrombosis incidence were observed (Table 3). Conclusion: Primary ITP patients have a tendency towards increased PAI-1 activity, which is associated with considerably delayed plasma clot lysis. Albeit an association with the bleeding score could not be identified, this impaired lysis could be seen as a counter-regulation and at least contribute to the relatively mild bleeding tendency in patients with ITP. Figure 1 Figure 1. Disclosures Pabinger: CSL Behring: Consultancy, Honoraria, Research Funding; NovoNordisk: Consultancy, Research Funding; Bayer: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Daiichi Sanchyo: Consultancy, Honoraria; Alexion: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria.

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Haemostasis in Immune Trombocytopenia Patients Responders to Agonists of Thrombopoietin Receptor

Blood ◽

10.1182/blood.v128.22.3743.3743 ◽

2016 ◽

Vol 128 (22) ◽

pp. 3743-3743

Author(s):

Nora Butta ◽

Ihosvany Fernandez Bello ◽

María Teresa Álvarez Román ◽

Monica Martín Salces ◽

Raul Justo Sanz ◽

...

Keyword(s):

Platelet Count ◽

Thrombin Generation ◽

Conflicts Of Interest ◽

Platelet Rich Plasma ◽

Alpha Angle ◽

Bleeding Risk ◽

Healthy Controls ◽

Pharmacologic Agent ◽

Thrombopoietin Receptor ◽

Pai 1

Abstract Introduction: The goal of treatment of patients with immune thrombocytopaenia (ITP) is to raise platelet count to a level that will minimize or stop bleeding. One of the therapeutic strategies employed is to augment platelet production with agonists of the thrombopoietin receptor (TPOR-A). Clinical trials for TPOR-A comparing their effects with placebo showed a reduction in proportion of patients reporting bleeding (Tarantino et al, Blood Coag Fibrinolysis, 2013, 24:284-296). This effect might rely on the increase in platelet count, but other factors known to compensate bleeding risk in thrombocytopenic ITP patients might be regulated by TPOR-A. Objective: We aimed to compare haemostasis in ITP patients untreated with any pharmacologic agent (UT-ITPp) and treated with TPOR-A (TPOA-Rp) using the coagulation global assays thromboelastrometry (ROTEM®) and Calibrated Automated Thrombogram (CAT). Methods: Thirty chronic UT-ITPp [platelet count: (86±60)x109 platelets/L], twenty six responders to TPOR-A [16 with Romiplostim® and 10 with Revolade®, platelet count: (132±46)x109 platelets/L] and fifty healthy controls were included. Citrated blood was centrifuged at 152 g 10 min at 23°C for obtaining platelet rich plasma (PRP) and at 1,500 g for 15 min at 23°C for platelet-poor plasma (PPP). Aliquots were stored at -80ºC until analysis. Non-activated ROTEM was performed on PRP adjusted to a platelet count of 25 x 109/L. Clotting time (CT, time from start of measurement until initiation of clotting [in seconds], alpha angle, which reflects the rate of fibrin polymerisation (tangent to the curve at 2-mm amplitude [in degrees]), maximum clot firmness, which reflects the maximum tensile strength of the thrombus (MCF, [in mm]) and LI60, which describes the percentage of maximum clot strength present at 60 min (in %), were recorded. Plasma thrombin generation was measured in PPP using the CAT test at a final concentration of 1 pM tissue factor and 4 microM phospholipids. We evaluated the endogenous thrombin potential (ETP, the total amount of thrombin generated over time); the lag time (the time to the beginning of the explosive burst of thrombin generation); the peak height of the curve (the maximum thrombin concentration produced); and the time to the peak. Platelet activation was determined by flow cytometry through PAC1-FITC binding after stimulation with 100 micromol/L thrombin receptor-activating peptide 6 (TRAP). Fibrinolytic proteins were tested in PPP using commercialized kits. Comparisons of quantitative variables were made with SPSS.22 software. Values of p≤0.05 were considered statistically significant. Results: Platelets from all patients with ITP had a defect in their ability to be activated, as shown by the lower PAC1 binding (p<0.001). No differences were observed among groups for thrombin generation except for an increase in ETP in both groups of ITP patients [control: 1240±320 nMxmin, UT-ITPp: 1464±443 nMxmin (p<0.05), TPOA-Rp: 1533±390 nMxmin (p<0.05)]. In ROTEM experiments, PRP from UT-ITPp and TPOA-Rp showed a prolonged CT [control: 550± 95 sec, UT-ITPp: 1090±75 sec (p<0.05), TPOA-Rp: 859±209 sec (p<0.05)]. Only UT-ITPp presented a diminished alpha angle [control: 60.3±7.5, UT-ITPp: 49.3±7.3 (p<0.05), TPOA-Rp: 55.8±5.58]. On the other hand, TPOA-Rp had an increased MCF (control: 46.5±2.1 mm, UT-ITPp: 50.2±5.6 mm, TPOA-Rp: 57.9±4.4 mm, p<0.05) and LI60 (control: 91.8±3.1 %, UT-ITPp: 94.1±3.1 %, TPOA-Rp: 97.6±1.1 %, p<0.05). To evaluate whether increased LI60 values were due to an imbalance in fibrinolysis related proteins, tPA, uPA, TAFI and PAI-1 plasma levels were measured. No differences were observed among the two groups of patients and healthy controls except for PAI-1 which level was increased in TPOA-Rp (control: 12.9±12.3 ng/ml, UT-ITPp: 17.3±12.5 ng/ml, TPOA-Rp: 46.8±20.8, ng/ml p<0.05). Conclusions: As we previously described, TPOR-A treatment increased platelet count but did not ameliorate their function (Álvarez Román et al, Thromb Haemost. 2014, 112:65-72). Nevertheless, ITP patients responders to TPOR-A showed a haemostasis unbalanced on a hypercoagulable profile due, at least in part, to a hipofibrinolytic pattern mainly caused by an increase in PAI-1 plasma level. This fact, together with the increment in platelet count caused by TPOR-A, might help to protect these patients from bleeding. This work was supported by a grant from the FIS-FEDER PI15/01457 Disclosures No relevant conflicts of interest to declare.

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Autoantibodies to Thrombopoietin and the Thrombopoietin Receptor in Patients with Immune Thrombocytopenia

Blood ◽

10.1182/blood.v128.22.2548.2548 ◽

2016 ◽

Vol 128 (22) ◽

pp. 2548-2548 ◽

Cited By ~ 1

Author(s):

Ishac Nazy ◽

Jane C. Moore ◽

Rumi Clare ◽

James W. Smith ◽

Nikola Ivetic ◽

...

Keyword(s):

Research Funding ◽

Immune Thrombocytopenia ◽

Healthy Controls ◽

Capture Assay ◽

Immune Mediated ◽

Splenic Enlargement ◽

Thrombopoietin Receptor ◽

Circulating Antibodies ◽

Platelet Disorders ◽

Circulating Autoantibodies

Abstract Background: Primary immune thrombocytopenia (ITP) is an autoimmune bleeding disorder caused by autoantibodies against platelet glycoproteins (GP). These autoantibodies are detected in only 40-60% of ITP patients even when sensitive techniques are used. Our understanding of the mechanisms of ITP is limited by the variability in clinical presentation, varied differences in treatment responses and the lack of reliable biomarkers. Several studies have exploited the possibilities of other immune-mediated mechanisms to account for low platelet counts in the absence of detectable antibodies. Thus, we hypothesized that other autoantibodies that target antigens involved in the platelet lifecycle can be important in ITP, such as thrombopoietin (TPO) and the thrombopoietin receptor (cMpl). The objective of this study was to evaluate the frequency and clinical significance of autoantibodies against TPO and cMpl in patients with ITP compared to patients with other thrombocytopenic disorders and healthy controls. Methods: We tested well-defined adult ITP patients with a platelet count less than 100 x109/L and ITP patients in remission (platelets > 100,000) all of whom had not received any immune-modulating treatments in the previous 3 months. We also tested patients with other immune-mediated platelet disorders, non-immune thrombocytopenia and healthy controls. Patients with immune-mediated platelet disorders had anti-phospholipid syndrome (APS); heparin induced thrombocytopenia (HIT); or thrombotic thrombocytopenic purpura (TTP). Patients with non-immune thrombocytopenia had hypersplenism with documented splenic enlargement; familial thrombocytopenia; or myelodysplastic syndrome. Samples were tested for circulating antibodies against TPO or cMpl using newly developed enzyme immunoassays (EIAs) and for antibodies against platelet glycoproteins (GPIIb/IIIa and GPIb/IX) using the antigen capture assay. Results: Among patients with active ITP, 36/42 (86%) had antibodies to TPO or c-Mpl: 4/42 (10%) had anti-TPO autoantibodies only and 5/42 (12%) had anti-cMpl autoantibodies only and 15/42 (36%) had both. Among patients with ITP in remission, 8/15 (53%) had autoantibodies to TPO or cMpl. Autoantibodies were not detected in healthy controls; however, all patients with non-immune thrombocytopenia had circulating autoantibodies to TPO or c-Mpl (10/10, 100%): 1/10 (10%) had anti-TPO autoantibodies only and 1/10 (10%) had anti-cMpl autoantibodies only and 8/10 (80%) had both. We also found antibodies against TPO and cMpl in patients with other immune-mediated platelet disorders. Among HIT patients (n=26), 73% had antibodies to TPO and 50% had antibodies to cMpl; among TTP patients (n=16), 31% had antibodies to TPO and 13% had antibodies to cMpl; and among APS patients (n=17), 29% had antibodies to TPO and 47% had antibodies to cMpl. Platelet bound antibodies to GPIIb/IIIa, GPIb/IX or both were detected in 18/42 (43%) active ITP samples; 6/15 (40%) remission ITP samples; and 2/10 (20%) patients with thrombocytopenia from non-immune causes. ITP patients with anti-TPO or anti-cMpl antibodies required fewer ITP therapies before remission was achieved compared with patients who had anti-GP autoantibodies. Conclusions: Testing the entire panel of autoantibodies that included anti-TPO, anti-cMpl and anti-GP, we were able to identify all patients with active ITP; however, we could not distinguish between patients with ITP and other thrombocytopenic syndromes. Disclosures Arnold: Novartis: Consultancy, Research Funding; Bristol Myers Squibb: Consultancy; UCB: Consultancy; Amgen: Consultancy, Research Funding.

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Haemostasis Impairment in Patients with Myelodysplastic Syndromes with Normal Platelet Counts

Blood ◽

10.1182/blood.v126.23.5225.5225 ◽

2015 ◽

Vol 126 (23) ◽

pp. 5225-5225

Author(s):

Nora Butta ◽

Monica Martín Salces ◽

Raquel De Paz ◽

Ihosvany Fernandez Bello ◽

María Teresa Álvarez Román ◽

...

Keyword(s):

Platelet Count ◽

Myelodysplastic Syndromes ◽

Thrombin Generation ◽

Alpha Angle ◽

Clot Formation ◽

Bleeding Complications ◽

Control Group ◽

Healthy Controls ◽

Normal Platelet Count ◽

Normal Platelet

Abstract Background: Bleeding complications can have serious outcomes in patients with myelodysplastic syndromes (MDS) and are usually related to thrombocytopaenia. In a recent work we demonstrated that platelets from MDS have impaired capacity to respond to agonist stimulation and exposed more phosphatidylserine (PS) than those from healthy controls whichever their platelet count was (Martin et al, Thromb Haemost., 2013;109:909-19). The exposure of PS in the outer layer of cell membranes supports coagulation through enhanced formation of the tenase (factors IXa, VIIIa and X) and prothrombinase (factors Xa, Va and prothrombin) complexes and thrombin generation. So, the possibility exists that these processes are increased in these patients. Objectives: The aim of this work was to study whether thrombus formation and thrombin generation is impaired in MDS patients with normal platelet count employing global coagulation tests thromboelastrometry (ROTEM) and Calibrated Automated Thrombogram (CAT). Methods: Thirty-one MDS patients with normal platelet count and twenty healthy controls were included. Citrated blood was centrifuged at 152 g 10 min at 23°C for obtaining platelet rich plasma (PRP) and at 1,500 g for 15 min at 23°C for platelet-poor plasma (PPP). For ROTEM and CAT experiments, PRP was adjusted to a platelet count of 25 x 109/L. Aliquots for ROTEM assay were tested within the two hours after obtaining blood samples. For CAT experiments, adjusted PRP and PPP aliquots were stored at -70ºC until analysis. Kinetics of clot formation, non-activated ROTEM was performed on adjusted PRP. Clotting time (CT, time from start of measurement until initiation of clotting [in seconds], alpha angle, which reflects the rate of fibrin polymerisation (tangent to the curve at 2-mm amplitude [in degrees]), and maximum clot firmness, which reflects the maximum tensile strength of the thrombus (MCF, [in mm]), were recorded. Thrombin generation was measured in adjusted PRP without any trigger and in PPP with 1 pM tissue factor and 4 µM phospholipids (PPP-Reagent LOW, Thrombinoscope BV, Maastricht, The Netherlands) as trigger. Endogenous thrombin potential (ETP, the total amount of thrombin generated over time); the lag time (the time to the beginning of the explosive burst of thrombin generation); the peak height of the curve (the maximum thrombin concentration produced); and the time to the peak were evaluated. Platelet activation was determined by PAC1 (BD, Madrid, Spain) binding after stimulation with 100 μM thrombin receptor-activating peptide 6 (TRAP, Bachem, Switzerland) and surface PS through Annexin-V binding and flow cytometry analyses. Results: Platelets from MDS patients had a reduced response to TRAP stimulation (control= 12016+6384 arbitrary units; MDS= 5829+3704 arbitrary units) and exposed more PS than controls (control= 362.1+80.5 MF; MDS= 378.5+173.5 MF). ROTEM experiments showed kinetic parameters corresponding to a hipocoagulable profile (CT: control= 550+95 sec, MDS= 922+216 sec, p<0.01; alpha angle control= 62.8+4.3, MDS= 47.5+6.0, p<0.05; A5: control= 29.8+3.2, MDS= 24.2+5.8, p<0.05 whereas MCF was similar to controls (control= 46.7+3.1mm, MDS= 47.5+4.3 mm). In order to evaluate whether the impaired clot formation was due to a reduction in plasma-associated thrombin generation, CAT experiments were performed in PPP samples. No differences were found between MDS patients and control group (ETP: control=1223.4+257.8 nMxmin, MDS= 1224.4+344 .1 nMxmin; peak: control= 279.5+54.7nM, MDS= 265.9+64.1 nM). On the other hand, when thrombin generation experiments were performed in adjusted PRP, ETP and peak values were lower than in control group (ETP: control=1574.8+430.5 nMxmin, MDS= 1167.4+354 nMxmin,p<0.05; peak: control= 225.6+82.9 nM, MDS= 266.9+92.2 nM, p<0.05). Conclusions: Platelet dysfunction might be resposible of bleeding complications observed in patients with MDS with normal platelet counts. Increment in PS exposure on platelet surface did not seem to compensate impairment in platelet function. Disclosures No relevant conflicts of interest to declare.

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Absence of Hyperactivation of Fibrinolysis Explains the Lack of Hemostatic Efficacy of Prophylactic Tranexamic Acid (TXA) in Hypoproliferative Thrombocytopenia

Blood ◽

10.1182/blood-2021-146898 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 2094-2094

Author(s):

Anton Ilich ◽

Terry B. Gernsheimer ◽

Darrell J Triulzi ◽

Heather Herren ◽

Siobhan P Brown ◽

...

Keyword(s):

Board Of Directors ◽

Research Funding ◽

Study Drug ◽

Clot Lysis ◽

Advisory Committees ◽

Trial Investigator ◽

Lysis Time ◽

Pai 1 ◽

Clot Lysis Time

Abstract Background: We previously reported the results of the A-TREAT study (American Trial Using Tranexamic Acid in Thrombocytopenia: NCT02578901). This randomized double-blind placebo-controlled trial demonstrated that TXA administration is not superior to placebo in preventing WHO grade 2 or higher bleeding in severely thrombocytopenic patients requiring supportive platelet transfusion following myeloablative therapy for hematologic disorders (Gernsheimer T., ASH 2020 Plenary Session). Here, we present results of the A-TREAT ancillary study - Fibrinolysis Evaluation in A-TREAT (FEAT). Blood samples were collected from a subset (n=115) of A-TREAT participants just prior to initiation of study drug (when the platelet count was <30,000/µl) and at a later time point when TXA was at a steady state trough level (5 ±2 days following study drug initiation). Using global assays of fibrinolysis in plasma, our a priori hypotheses were that: 1] a baseline 'hyperfibrinolytic' profile would be associated with a higher proportion of grade 2+ bleeding; and 2] trough TXA levels would be associated with a 'hypofibrinolytic' profile and a lower proportion of grade 2+ bleeding. Methods: Fibrinolysis in platelet-free citrated plasma was assessed by 3 global assays: euglobulin clot lysis time (ECLT), plasmin generation (PG), and tPA resistance clot lysis time (tPA-CLT) using previously described methods (Ilich A. RPTH 2020, Miszta A. JTH 2021). Trough plasma TXA concentration was measured using a validated tandem mass spectrometry assay. Individual fibrinolytic analytes (PAI-1, tPA, plasminogen, alpha2-antiplasmin and plasmin-antiplasmin complexes) were quantified by ELISA. Results: Baseline samples did not demonstrate a hyperfibrinolytic profile by ECLT. To the contrary, ECLT values were significantly increased compared to healthy controls (figure 1). Furthermore, none of the measured fibrinolytic parameters (ECLT, tPA-CLT, total PAI-1, tPA, plasminogen, alpha2-antiplasmin or plasmin-antiplasmin complexes) at baseline were associated with a greater risk of grade 2+ bleeding during follow up, regardless of treatment arm. On the follow-up samples, neither pharmacokinetic (trough TXA concentration) nor pharmacodynamic parameters (PG or tPA-CLT) were associated with bleeding severity. A high inter-patient variability of TXA trough concentrations was noted in the treatment arm (min-max: 0.7-10 ug/ml), and drug levels correlated strongly with global fibrinolysis assessment by PG (Spearman r, -0.78, 95% CI -0.88 - -0.62) and tPA-CLT (r, 0.74, 0.56 - 0.85) (figure 2). Conclusions: 1] No evidence of fibrinolytic hyperactivation was observed in these thrombocytopenic patients; 2] trough TXA concentrations varied significantly between patients receiving the same dosing schedule; and 3] tPA-CLT and PG parameters correlated well with TXA plasma concentrations and thus may be used to estimate the extent of fibrinolytic inhibition in patients treated with TXA. Discussion: The absence of hyperactivation of endogenous fibrinolysis in this study is in contrast to our recent findings in trauma. Specifically, we reported that almost half of trauma patients demonstrated evidence of fibrinolytic hyperactivation (by ECLT) on admission (Ilich A. Thromb Res, 2021). Since TXA has been shown to reduce mortality due to bleeding in trauma (CRASH II, Lancet, 2010) and given that baseline hyperfibrinolysis is common in trauma, we hypothesize that the absence of fibrinolytic hyperactivation observed in the A-TREAT study patients likely explains the clinical lack of efficacy of TXA. Figure 1 Figure 1. Disclosures Gernsheimer: Amgen: Honoraria; Novartis: Honoraria; Principia: Research Funding; Rigel: Research Funding; Cellphire: Consultancy; Dova: Consultancy; Sanofi: Consultancy. Triulzi: Fresenius Kabi: Membership on an entity's Board of Directors or advisory committees; Realta: Membership on an entity's Board of Directors or advisory committees. Wolberg: CSL Behring: Consultancy; Bristol Myers Squibb: Research Funding; Takeda: Research Funding. Key: Takeda: Research Funding; BioMarin: Honoraria, Other: Participation as a clinical trial investigator; Sanofi: Consultancy; Grifols: Research Funding; Uniqure: Consultancy, Other: Participation as a clinical trial investigator.

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Association between Megakaryocyte Abnormalities on Bone Marrow Smear and Response to Thrombopoietin Receptor Agonists in Adult Patients with Primary Immune Thrombocytopenia

Blood ◽

10.1182/blood-2021-151435 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 3160-3160

Author(s):

Ondine Walter ◽

Agnès Ribes ◽

Johanne Germain ◽

Jean-Baptiste Rieu ◽

Thibault Comont ◽

...

Keyword(s):

Bone Marrow ◽

Platelet Count ◽

Board Of Directors ◽

Research Funding ◽

Immune Thrombocytopenia ◽

Adult Patients ◽

Second Line ◽

Bone Marrow Smear ◽

Advisory Committees ◽

Thrombopoietin Receptor

Abstract Introduction: Immune thrombocytopenia (ITP) is an autoimmune disease due to peripheral destruction but also impaired central production of platelets. Autoimmune reaction directed against megakaryocytes (MKs) has been described, and may explain morphological abnormalities of MKs observed in some patients with primary ITP. Thrombopoietin receptor agonists (TPO-RAs) are indicated as second-line treatments for ITP, but no predictive factors of response used in clinical routine practice has been demonstrated. The utility of systematic bone marrow smears (BMS) at ITP diagnosis is discussed. Howerer, it is usually recommended before second-line treatments. Two studies have suggested an association between MK abnormalities and response to corticosteroids in primary ITP, but none have investigated this association for TPO-RAs. This study aimed to investigate the association between MK abnormalities and response to TPO-RAs in adult patients with primary ITP. Methods: The source of population was the CARMEN registry. The CARMEN (Cytopénies Auto-immunes: Registre Midi-PyréneEN) registry is aimed at the prospective follow-up of all incident ITP adults in the French Midi-Pyrénées region (South-West of France, 3 million inhabitants) since June 2013. Each investigator follows all adult patients (aged ≥18 years) with incident ITP in routine visit or hospital stay. ITP was defined by international definition (platelet count <100 x 10 9/L and exclusion of other causes of thrombocytopenia). The study population consisted in all patients included in the CARMEN registry between June 2013 and March 2018 with primary ITP, treated by TPO-RA and with a BMS before initiating TPO-RA. We excluded the patients with a number of MKs <10 MK on the BMS. Morphological abnormalities were established based on literature and defined by consensus among 3 expert cytologists (AR, JBR and VDM). All MKs present on each smear were analyzed. MKs were categorized by the presence of dysplasia (monolobed MK and/or separated nuclei and/or microMKs), and according to their stage of maturation (basophilic, granular and thrombocytogenic). All patients' medical charts were reviewed by two experts in ITP (OW and GM) to determine the response to TPO-RAs. Response was defined by a platelet count between 30 and 100 G/L with at least a doubling of basal platelet count according to the international definition. In case of subsequent exposure to both TPORAs in a single patient, response was defined by response to at least one TPO-RA in the main analysis. We performed a subgroup analysis by TPORAs. Results: During the study period, 451 patients with incident ITP were included in CARMEN-registry. Among them, 105 had been treated by TPO-RAs, including 65 with BMS before the exposure to TPORA. We then excluded 20 patients with secondary ITP and 7 with less than 10 MKs on the BMS. We finally included 38 patients in the analysis. Median age at diagnosis was 71 years (interquartile range - IQR: 31 - 94) and 34.2% were women. Thirty-three patients were treated with eltrombopag, 17 with romiplostim including 13 who were exposed to both TPORAs. Thirty-four (89.4%) achieved response. The median number of MKs analyzed per patient was 137 (IQR: 50 - 265). All results are presented in Table 1. In the main analysis, there was no significant difference in the median percentage of dysplastic MKs in responders (4.0%, 95% confidence interval - CI: 2.3 - 6.4) and non-responders (4.5%, 95% CI: 0.7 - 7.1). There was a trend for a higher proportion of granular MKs (4.5%, 95% CI: 3 - 6) and basophilic MKs (30.1%, 95% CI: 21.9 - 39.1) in non-responders comparing to responders (granular: 2.0%, 95% CI: 0 - 4.1; basophilic: 21.3%, 95% CI: 11.4 - 40.7). Results were similar in the subgroup of patients treated with eltrombopag (data not shown; the low number of patients treated with romiplostim precluded any analysis). Conclusion: In this study, neither MK abnormalities nor the pattern of MK maturation stages were significantly associated with response to TPO-RAs. These results do not support a systematic bone marrow smear in patients with primary ITP to look for morphological predictive factors of response to TPO-RA. Figure 1 Figure 1. Disclosures Comont: AstraZeneca: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Takeda: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding. Moulis: Amgen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Grifols: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sobi: Membership on an entity's Board of Directors or advisory committees; Argenx: Membership on an entity's Board of Directors or advisory committees.

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Effects of Rituximab and Dexamethasone on Regulatory and Pro-Inflammatory B-Cell Subsets in Patients with Primary Immune Thrombocytopenia

Blood ◽

10.1182/blood.v128.22.1378.1378 ◽

2016 ◽

Vol 128 (22) ◽

pp. 1378-1378

Author(s):

Sif Gudbrandsdottir ◽

Marie Brimnes ◽

Tania Kollgaard ◽

Hans Carl Hasselbalch ◽

Claus Henrik Nielsen

Keyword(s):

B Cells ◽

Autoimmune Diseases ◽

B Cell ◽

Research Funding ◽

Immune Thrombocytopenia ◽

Lower Proportion ◽

Surface Markers ◽

Healthy Controls ◽

Cell Functions ◽

Primary Immune Thrombocytopenia

Abstract Background B-cell depletion with rituximab (RTX) is widely accepted as first- or second-line therapy in primary immune thrombocytopenia (ITP), but it is still unclear how RTX mediates its positive effect in ITP patients. RTX has been reported to induce a reduced titer of platelet antibodies. However, this finding is inconsistent and other B-cell functions, such as the ability to secrete cytokines or to function as antigen-presenting cells for T cells, may be involved in the pathogenesis of ITP. Evidence suggests that B cells participate in the regulation of autoimmune diseases by virtue of their ability to produce the regulatory cytokines interleukin (IL)-10, IL-35, or transforming growth factor β. The various functions of B cells involved in the pathogenesis of autoimmune diseases can in part be deducted by their phenotype as recognized by measurement of specific surface markers and cytokine secretion. Materials and Methods We previously conducted a trial involving 137 newly diagnosed adult ITP patients randomized to treatment with RTX (375 mg/m2/week for 4 weeks) + dexamethasone (DXM) (40 mg/day for 4 days repeated up to 6 cycles) or DXM monotherapy. From this cohort, we identified 16 patients with available samples of peripheral blood mononuclear cells (PBMCs) at baseline and 12 months after treatment; 9 patients from the RTX+DXM group, 7 patients from the DXM group. Seven anonymous blood donors served as healthy controls. PBMCs were incubated for 18 h at 37°C under 5% CO2 in RPMI-1640 containing 10% (v/v) serum from healthy blood group AB donors, either alone or stimulated with 10 µg/ml CpG oligodeoxynucleotides. Expression of the cell-surface markers CD5, CD27, CD25 and CD19, and intracellular content of IL-6 and IL-10 were measured by flow cytometry. Results All patients responded to therapy and were in complete or partial remission at 12 months. Patient characteristics are listed in table I. We observed a significant increase in the proportion of CD5+ B cells 12 months after treatment with RTX+DXM compared to baseline (p < 0.01, Fig. 1A). The percentage of CD27+ memory B cells was significantly decreased at 12 months compared to baseline in patients receiving RTX+DXM (p < 0.05, Fig. 1B), and there was an inverse correlation between platelet numbers and the proportion of CD27+ B cells (R = -0.71; p < 0.05). The proportion of CD25+ B cells tended to decrease in patients treated with RTX+DXM, and was lower at 12 months than in patients treated with DMX only (p < 0.05, Fig 1C). PBMCs from ITP patients contained a lower proportion of IL-10+ B cells (p < 0.01) as well as a lower proportion of B cells producing IL-6 (p < 0.01) at baseline than PBMCs from healthy controls. At 12 months the low proportions had normalized in both treatment groups (Fig. 2). Conclusion B cells from ITP patients treated with RTX+DXM contained a high proportion of CD5+ B cells and low proportions of CD25+ and CD27+ B cells. Before treatment, B cells from ITP patients contained low frequencies of IL-10+ and IL-6+ B cells. Treatment with RTX + DXM or DXM alone reverted these aberrancies to normal. The increase in IL-10+ B cells as well as CD5+ B cells, which may represent overlapping subsets, is compatible with induction of Bregs and may support Treg development. Given the role of CD5+ B cells in maintenance of tolerance, the high frequency of these cells, which has also been observed after RTX therapy in rheumatoid arthritis, is compatible with amelioration of disease. Table 1 Table 1. Disclosures Gudbrandsdottir: GSK: Research Funding; Amgen: Research Funding.

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Splenectomy for Primary Immune Thrombocytopenia Revisited at the Era of Thrombopoietin Receptor Agonists: New Insights for an Old Treatment

Blood ◽

10.1182/blood-2021-147450 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 17-17

Author(s):

Arthur Mageau ◽

Louis Terriou ◽

Mikael Ebbo ◽

Odile Souchaud-Debouverie ◽

Corentin Orvain ◽

...

Keyword(s):

Board Of Directors ◽

Research Funding ◽

Immune Thrombocytopenia ◽

Sustained Response ◽

White Pulp ◽

Advisory Committees ◽

Thrombocytopenic Purpura ◽

Thrombopoietin Receptor ◽

Primary Immune Thrombocytopenia

Abstract Introduction Although splenectomy is still considered as the most effective curative treatment for primary immune thrombocytopenia (ITP), its use has significantly declined in the last decade, especially since the emergence of thrombopoietin receptor agonist (TPO-RAs) and anti-CD20 monoclonal antibodies 1-3. The main objective of our study was to evaluate if splenectomy was still as effective in the modern era, particularly for patients who failed to respond to TPO-RAs and rituximab. One of the secondary objectives was to assess, among patients who did not respond to or relapse after splenectomy, the pattern of response to subsequent intervention with treatments used before splenectomy and particularly TPO-RAs. Methods This multicentre retrospective observational study involved adults who underwent surgical splenectomy for primary ITP in France from 2011 (authorization of TPO-RAs in France) to 2020. To be included in the study, patients had to fulfil the following criteria : age ³18 years, primary ITP diagnosis defined according to the usual international criteria 2. Patients with abnormal spleen histology (other than reactional lymphoid hyperplasia, white-pulp hypoplasia or red pulp hyperplasia) or yet definite secondary ITP were excluded. Response was defined according to international criteria 4. Sustained response was defined as the absence of ITP relapse at last visit. We performed univariable and multivariable logistic regression procedures to calculates the odds ratio associated with a sustained response. Results In total,185 patients, 98 (53 %) women, with median age at splenectomy of 43.3 [interquartile range 27.6-64.3] years, were included in 18 French university and general hospitals from the French reference center network. Most of the patients were splenectomised at the chronic phase of ITP (n=150, 81.1%) and only two patients had undergone surgery within 3 months after ITP onset. Of note, 100 (54.1%) and 135 (73.0%) patients received TPO-RAs and/or rituximab prior to the splenectomy, respectively. The median time of follow-up after splenectomy was 39.2 months [16.5-63.0]. Overall, 144 (77.8%) of patients had an initial response and 23 patients (12.4%) relapsed during follow-up leading to an overall rate of sustained response of 65.4%, similar to the one observed in the pre-TPO-RA's era 1. Characteristics of patients according to the period during which occurred the splenectomy is available in Table 1. Among the 14 patients who failed to respond to both eltrombopag and romiplostim prior to splenectomy a sustained response after splenectomy was observed in 7 (50%). Among the 13 patients who had failed after both TPO-RAs and rituximab, we observed a sustained response in 6 (46%). In the multivariate analysis, an older age (60-75 years: OR 0,39 [0,17-0,86], p=0.02; >75 years: OR 0,28 [0,10-0,75], p=0.013) and a history of more than 4 treatment lines for ITP before splenectomy (OR 0.25 [0.08-0.66], p=0.010) were significantly associated with a lack of sustained response after splenectomy. TPO-RAs were used for 57/64 (89.1%) patients who failed to respond to splenectomy. Among them, 21 were treated with one TPO-RA (i.e. eltrombopag or romiplostim) which was previously used before splenectomy without any efficacy and a response was observed in 13 (62%) of them. Conclusions In conclusion, splenectomy seems to be still a relevant option for treating adult primary ITP not responding to TPO-RAs and rituximab. Patients who fail to respond or relapse after splenectomy should be re-challenged with TPO-RAs. 1. Kojouri, K., Vesely, S. K., Terrell, D. R. & George, J. N. Splenectomy for adult patients with idiopathic thrombocytopenic purpura: a systematic review to assess long-term 2. Provan, D. et al. Updated international consensus report on the investigation and management of primary immune thrombocytopenia. Blood Adv. 3.Neunert, C. et al. American Society of Hematology 2019 guidelines for immune thrombocytopenia. Blood Adv. 3, 3829-3866 (2019). 4. Rodeghiero, F. et al. Standardization of terminology, definitions and outcome criteria in immune thrombocytopenic purpura of adults and children: report from an international working group. Blood 113, 2386-2393 (2009). Figure 1 Figure 1. Disclosures Terriou: Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Ebbo: Grifols: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Octapharma: Other: Attendance Grant; Sobi: Other: Attendance Grant. Viallard: Novartis: Consultancy; Amgen: Consultancy; Grifols: Consultancy; LFB: Consultancy. Jeandel: Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Support for congress; Sobi: Membership on an entity's Board of Directors or advisory committees; Amgen: Other: Support for congress; GSK: Other: Support for congress; Pharming: Other: support for congress. Michel: Amgen: Consultancy; Novartis: Consultancy; Rigel: Honoraria; UCB: Honoraria; Alexion: Honoraria; Argenx: Honoraria. Godeau: Grifols: Consultancy; Sobi: Consultancy; Amgen: Consultancy; Novartis: Consultancy. Comont: Takeda: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria, Research Funding; AstraZeneca: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding.

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Immune Profiling of Immune Thrombocytopenia (ITP) Patients: Evidence for CD8 T Cell Involvement in the Disease

Blood ◽

10.1182/blood.v126.23.2259.2259 ◽

2015 ◽

Vol 126 (23) ◽

pp. 2259-2259

Author(s):

Monica Escorcio-Correia ◽

Andrew Provan ◽

Daniel J Pennington

Keyword(s):

T Cells ◽

B Cells ◽

Research Funding ◽

Immune Thrombocytopenia ◽

Cytotoxic T Cells ◽

Granzyme B ◽

Cd8 T Cell ◽

Interferon Γ ◽

Healthy Controls ◽

Platelet Autoantibodies

Abstract Introduction: Immune thrombocytopenia (ITP) is a bleeding disorder caused by an autoimmune response against platelets. In the majority of cases, ITP is thought to be caused by the presence of autoreactive B cells that produce anti-platelet autoantibodies and target platelets for destruction by phagocytic cells. However, in about 40% of ITP patients platelet autoantibodies cannot be detected and there is some evidence that cytotoxic cells might also be responsible for platelet death. Indeed, many patients repeatedly fail to respond to current immunosuppressive therapies that target B cells and their autoantibodies. As a consequence, these patients retain very low platelet counts with increased bleeding diathesis. In this study we have immunophenotyped a group of adult chronic ITP patients that have not responded to traditional immunosuppressive therapies and we identified 2 subgroups of patients with either an increase or decrease in the frequency of CD8+ T effector memory CD45RA+ cells (CD8TEMRA) compared to healthy controls. Methods: PBMCs were isolated from blood samples of 14 ITP patients with platelet counts <100x109/L and 14 matched healthy controls. The cells were phenotyped using a variety of antibodies including: CD3, CD4, CD8, CD45RA, CCR7, CD127, CD25, CD14, CD16 and CD19. In addition, at least 5x106 PBMCs were stimulated with PMA (50ng/ml) and ionomycin (1µg/ml) for 5 hours at 37°C, 5% CO2 and stained with antibodies against CD3 and CD8, then fixed and permeabilised before staining with antibodies specific to Granzyme B and Interferon-γ. Results and discussion: In our cohort of ITP patients we were able to identify two subgroups of patients based on their frequency of CD8TEMRA cells, identified as CD45RA+ CCR7- cells, gated on CD3+ CD8+ cells. Compared to healthy controls (mean=16.33%), 6/14 patients had significantly lower frequencies of CD8TEMRA cells (mean=11.31%) and 8/14 patients showed a significant increase (mean=31.50%). Interestingly, these two groups of patients also show significant differences between them in the frequency of CD19+ B cells (gated on CD3- cells), as the group with the lowest CD8TEMRA frequency showed a significant increase in B cells compared to the high CD8TEMRA group. Considering that CD8TEMRA cells are described as highly differentiated cytotoxic T cells, these results suggest that in patients with active ITP in which the CD8TEMRA population is more prevalent and the frequency of B cells is reduced, cytotoxic T cells might play an important role in platelet destruction. Although an increase in the frequency of CD8TEMRA with age has been described we did not find a correlation between these two variables in our cohort of patients. In the low CD8TEMRA group we also observed a significant increase in the frequency of T regulatory cells (Tregs) and monocytes when compared to healthy controls, whereas the trend in the high CD8TEMRA group was for frequencies closer to controls. In addition, when analysing the production of Granzyme B and Interferon-γ after a short in vitro stimulation, we found that the trend was for the CD8+ T cells in the high CD8TEMRA group to produce higher levels of both Granzyme B and Interferon-γ when compared to the patients in the low CD8TEMRA group. This would support the hypothesis that in patients with increased frequency of CD8TEMRA there has been an expansion of cells with cytotoxic properties. Further work will be required to confirm that in this cohort of patients there is a CD8+ T cell population that can specifically target and lyse platelets, thus contributing to ITP pathogenesis. Disclosures Provan: UCB: Consultancy; GSK: Equity Ownership, Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Medimmune: Consultancy.

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Procoagulant Profile in Patients with Immune Thrombocytopaenia

Blood ◽

10.1182/blood.v126.23.1062.1062 ◽

2015 ◽

Vol 126 (23) ◽

pp. 1062-1062

Author(s):

Nora Butta ◽

Ihosvany Fernandez Bello ◽

María Teresa Álvarez Román ◽

María Isabel Rivas Pollmar ◽

Miguel Canales ◽

...

Keyword(s):

Platelet Count ◽

Plasma Concentration ◽

Thrombin Generation ◽

Alpha Angle ◽

Bleeding Risk ◽

Endothelial Damage ◽

Healthy Controls ◽

Platelet Counts ◽

Spearman Test ◽

Pai 1

Abstract Background: Patients with platelet counts less than 20 or 30 x 109/L have an increased risk of bleeding. Nevertheless, some patients with immune thrombocytopenia (ITP) have fewer bleeding symptoms than expected. In a previous communication (ASH 2014) we reported that these patients presented high microparticles (MP)-associated procoagulant activity to compensate bleeding risk and that cellular origin of these MPs were platelets and red cells. However, other mechanisms might be involved. Objective: The aim of this work was to analyse the involvement of other factors to compensate bleeding risk in thrombocytopenic ITP patients. Moreover, the feasibility of using the coagulation global assays thromboelastrometry (ROTEM) and Calibrated Automated Thrombogram (CAT) to test haemostasis in these patients was evaluated. Methods: Fifty patients with chronic ITP with platelet count less than 50 x 109/L and twenty-five healthy controls were included. Platelet counts were determined with a Coulter Ac. T Diff cell counter (Beckman Coulter, Madrid, Spain). Citrated blood was centrifuged at 152 g 10 min at 23°C for obtaining platelet rich plasma (PRP) and at 1,500 g for 15 min at 23°C for platelet-poor plasma (PPP) and aliquots were stored at -70ºC until analysis. To assess the kinetics of clot formation, non-activated ROTEM was performed on PRP adjusted to a platelet count of 25 x 109/L. Clotting time (CT, time from start of measurement until initiation of clotting [in seconds], alpha angle, which reflects the rate of fibrin polymerisation (tangent to the curve at 2-mm amplitude [in degrees]), maximum clot firmness,which reflects the maximum tensile strength of the thrombus (MCF, [in mm]) and LI60, which describes the percentage of maximum clot strength present at 60 min (in %), were recorded. Plasma thrombin generation was measured in PPP using the Calibrated Automated Thrombogram (CAT) test at a final concentration of 1 pM tissue factor and 4 mM phospholipids (PPP-Reagent LOW, Thrombinoscope BV, Maastricht, The Netherlands). We evaluated the endogenous thrombin potential (ETP, the total amount of thrombin generated over time); the lag time (the time to the beginning of the explosive burst of thrombin generation); the peak height of the curve (the maximum thrombin concentration produced); and the time to the peak. Fibrinolytic proteins and E-selectin was tested in PPP using commercialized kits. Results were expressed as mean±SD. Comparisons of quantitative variables were made with Mann-Whitney test and correlations with Spearman test. Values of p≤0.05 were considered statistically significant. Results: PRP from ITP patients showed a prolonged CT (control: 550+ 95 sec, ITP: 890+165 sec, p<0.01), diminished alpha angle (control: 62.8+4.3, ITP: 53.5+7.5, p<0.05), and increased MCF (control: 46.7+3.1mm, ITP: 52.4+6.1 mm, p<0.05) and LI60 (control: 90.6+3.0% , ITP: 95.5+3.4, p<0.05) when compared with controls. In order to evaluate whether increased LI60 values were due to an imbalance in fibrinolysis related proteins, tPA, uPA, TAFI and PAI-1 plasma levels were measured. No differences were observed between patients and healthy controls except for PAI-1 which level was increased in ITP patients (control: 14.7 ng/ml+11.7 ng/ml, ITP: 30.4+17.5, p<0.05). Since plasma PAI-1 might be increased as consequence of endothelial damage, plasma concentration of E-selectin, marker of endothelial injury, was determined. E-selectin was increased in samples from ITP patients (control: 10.5 ng/ml+3.9 ng/ml, ITP: 31.6+14.0, p<0.05). Moreover, MCF and LI60 ROTEM parameters correlated to E-selectin plasma concentration (Spearman r values 0.6643, p<0.001 for MCF; 0.6053, p<0.001 for LI60). Thrombin generation in PPP was also measured and a shorter time to peak (control: 9.3+1.2 sec, ITP: 8.3+1.7 sec,p<0.05) and increased ETP (control: 1223.8+257.7 nMxmin, ITP: 1696.4+524 nMxmin,p<0.05) and peak (control: 225.7+82.8.1 nM, ITP: 330.4+106.1 nM,p<0.05) were observed in ITP patients. Conclusions: We demonstrated that ITP patients presented a hypercoagulable profile that might be related, at least in part, to a reduced fibrinolysis mainly caused by an increase in PAI-1 level that seemed to be related to endothelial damage. Moreover ROTEM and CAT appeared to be useful tools for evaluating coagulant profile in ITP patients. Disclosures No relevant conflicts of interest to declare.

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