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.).

Correlation between a 2-week change in platelet count and clinical outcomes after the initiation of ravulizumab treatment in adult patients with atypical hemolytic uremic syndrome: post-hoc analysis of the phase III trial.

BACKGROUND: Atypical hemolytic uremic syndrome (aHUS) is a rare disease with poor outcomes when untreated, in which ravulizumab or eculizumab are the standard of care where available. It has been proposed to regularly monitor platelet counts as an early response to ravulizumab or eculizumab. This study aimed to investigate the association between the early response to ravulizumab treatment and renal outcomes through 26 weeks in complement inhibitor-naïve adults with aHUS. METHODS: Adult patients with aHUS enrolled in the ALXN1210-aHUS-311 phase III study of ravulizumab were divided into two groups according to the achievement of complete thrombotic microangiopathy (TMA) response, i.e., platelet count and lactate dehydrogenase (LDH) normalization and ≥ 25% improvement in serum creatinine (sCr) from baseline, by 26 weeks and baseline characteristics were compared. Changes in hematologic parameters, platelet count and LDH, were compared between the two groups. Finally, we examined whether early hematologic improvement was associated with renal recovery (dialysis discontinuation or ≥ 25% improvement in sCr from baseline) through 26 weeks. RESULTS: Of 56 ravulizumab-treated patients, 30 achieved complete TMA response for 26 weeks, and 26 did not. Patients with complete TMA response showed rapid improvements in platelet counts. In patients without complete TMA response, delayed normalization of platelet counts was observed. By day 15, 93.3% (28/30) of patients with complete TMA response at 26 weeks and 26.9% (7/26) of patients without complete TMA response achieved platelet normalization. At 26 weeks, 62.5% (35/56) achieved renal recovery; however, 37.5% (21/56) did not. In patients with renal recovery, 85.7% (30/35) of patients had platelet count normalization by day 15; in patients without renal recovery, 23.8% (5/21) of patients had platelet count normalization (P < 0.0001). Receiver operator characteristic curve analysis showed a moderate association between platelet counts on day 8/15 and renal recovery within 26 weeks (day 8: area under the curve [AUC] = 0.7985; day 15: AUC = 0.8406). CONCLUSIONS: Platelet count normalization occurred in 62.5% (35/56) by day 15 after ravulizumab initiation and was associated with renal recovery through 26 weeks in complement inhibitor-naïve adults with aHUS. TRIAL REGISTRATION: This study was performed as a post-hoc analysis of the ALXN1210-aHUS-311 phase III clinical trial (NCT02949128, registered October 25, 2016).

Frontline use of rituximab may prevent ADAMTS13 inhibitor boosting during caplacizumab treatment in patients with iTTP: post hoc analysis of a phase 2/3 study in Japan.

BACKGROUND: A recent Phase 2/3 study in Japanese patients showed that caplacizumab was effective in treating immune-mediated thrombotic thrombocytopenic purpura (iTTP), with a low rate of iTTP recurrence. ADAMTS13 activity is monitored weekly during caplacizumab treatment to guide discontinuation of caplacizumab and consequently avoid exacerbations or relapse. The aim of this study was to assess changes in ADAMTS13 activity/inhibitor levels during caplacizumab treatment in this patient population. METHODS: A post hoc analysis of the Phase 2/3 study in Japanese patients was conducted. Patients ≥ 18 years old with confirmed iTTP received 10 mg of caplacizumab daily in conjunction with therapeutic plasma exchange (TPE) and immunosuppression for 30 days post-TPE. Outcomes included time to recovery of ADAMTS13 activity, ADAMTS13 activity level at treatment end, incidence of ADAMTS13 inhibitor re-elevation (ie, inhibitor boosting) during treatment, time to platelet count recovery, number of days of TPE, and safety. Outcomes according to presence of inhibitor boosting were also assessed. RESULTS: Nineteen patients had confirmed iTTP and were included in this analysis. Median (95% confidence interval) time to recovery of ADAMTS13 activity to ≥ 10%, ≥ 20%, and ≥ 60% was 14.6 (5.9-24.8), 18.5 (5.9-31.8), and 47.5 (18.5-60.9) days, respectively. Median (range) ADAMTS13 activity level at caplacizumab treatment end was 62.0% (29.0-101.0). Nine patients had ADAMTS13 inhibitor boosting. Delayed response of ADAMTS13 activity was observed in patients with inhibitor boosting. The median time to platelet count response and median number of TPE days were shorter in patients with inhibitor boosting compared with patients without inhibitor boosting. Rituximab was administered to almost all patients with inhibitor boosting (88.9%), after completion of TPE. Patients without inhibitor boosting who were treated with rituximab received it prior to completion of TPE. Only one patient experienced a recurrence, which occurred shortly after caplacizumab discontinuation due to an adverse event. CONCLUSIONS: In patients with iTTP, caplacizumab with TPE and immunosuppression may reduce the risk of ADAMTS13 inhibitor boosting if rituximab is administered early in the iTTP treatment period. Early administration of rituximab in addition to caplacizumab may prevent iTTP recurrence with inhibitor boosting. TRIAL REGISTRATION: NCT04074187.

Ratio of von Willebrand factor to ADAMTS13 is a useful predictor of esophagogastric varices progression after sustained virologic response in patients with hepatitis C virus-related liver cirrhosis.

AIM: Esophagogastric varices (EGV) are a serious complication of hepatitis C virus (HCV)-related liver cirrhosis (HCV-LC). In most cases, portal hypertension improves after a sustained virologic response (SVR) is achieved with direct-acting antiviral (DAA) treatment; however, in some cases, EGV exacerbation occurs after HCV elimination. We investigated whether von Willebrand factor (VWF) and a disintegrin-like metalloproteinase with thrombospondin type-1 motif 13 (ADAMTS13) can predict EGV progression with HCV-LC after SVR achievement. METHODS: This retrospective study enrolled 47 patients with HCV-LC who achieved an SVR after DAA treatment. Eighteen patients experienced EGV progression after the SVR was achieved (EGV progression group). Twenty-nine patients did not experience EGV progression after the SVR was achieved (non-EGV progression group). Plasma VWF antigen levels and ADAMTS13 activity were measured the day before DAA treatment. RESULTS: The EGV progression group had significantly higher plasma VWF antigen levels (p = 0.00331) and VWF-to-ADAMTS13 ratios (p = 0.000249) than the non-EGV progression group. Multivariate logistic regression models found that a VWF-to-ADAMTS13 ratio >2.3 was the only risk factor for EGV progression after the SVR was achieved (hazard ratio [HR], 18.4; 95% confidence interval [CI], 3.08-109; p = 0.00138). During the observation period, patients with a VWF-to-ADAMTS13 ratio >2.3 had a significantly higher cumulative incidence of EGV progression after SVR achievement than patients with a VWF-to-ADAMTS13 ratio ≤2.3 (HR, 6.4; 95% CI, 1.78-22.96; p = 0.0044). CONCLUSIONS: The VWF-to-ADAMTS13 ratio before DAA treatment for HCV could predict EGV progression after SVR achievement.

VWF/ADAMTS13 Ratio as a Potential Predictive Biomarker for Acute Kidney Injury Onset in Cirrhosis.

AIM: We investigated the von Willebrand factor to ADAMTS13 ratio (von Willebrand factor [VWF]:Ag/ADAMTS13:AC) as a potential biomarker for the outcomes of acute kidney injury (AKI) in liver cirrhosis (LC). METHODS: This retrospective cross-sectional study included patients with LC who developed AKI (AKI group: n = 91) and patients with LC who did not develop AKI [non-AKI (NAKI) group, n = 91] as a control group. Plasma levels of the von Willebrand factor antigen (Ag) and ADAMTS13 activity (AC) were measured in patients with AKI or NAKI. Moreover, risk factors for onset of AKI, AKI-associated 90-day mortality, and poor AKI treatment response were identified. RESULTS: The AKI group had a significantly higher VWF:Ag/ADAMTS13:AC than the NAKI group. Values of VWF:Ag/ADAMTS13:AC ≥ 5.7 were identified as risk factors for AKI onset in patients with LC (odds ratio [OR] 2.56; 95% CI 1.26-4.99; p < 0.001). Among patients with AKI, values of VWF:Ag/ADAMTS13:AC ≥ 9.0 were identified as risk factors for 90-day mortality (OR 6.83; 95% CI 2.32-20.10; p < 0.001). Cumulative survival was significantly lower in those with high (≥ 9.0) than in those with low (< 9.0) VWF:Ag/ADAMTS13:AC. Furthermore, values of VWF:Ag/ADAMTS13:AC ≥ 7.4 were identified as risk factors for poor treatment response (OR 4.2; 95% CI 1.39-12.70; p < 0.001). The treatment response rates were significantly higher in those with low (< 7.4) VWF:Ag/ADAMTS13:AC than in those with high (≥ 7.4) VWF:Ag/ADAMTS13:AC. CONCLUSION: VWF:Ag/ADAMTS13:AC potentially predicts the onset, prognosis, and treatment response of AKI in patients with LC.

ADAMTS-13: A Prognostic Biomarker for Portal Vein Thrombosis in Japanese Patients with Liver Cirrhosis.

Portal vein thrombosis (PVT), one of the most prevalent hepatic vascular conditions in patients with liver cirrhosis (LC), is associated with high mortality rates. An imbalance between a disintegrin-like metalloproteinase with thrombospondin type-1 motifs 13 (ADAMTS-13) enzyme and von Willebrand factor (VWF) is responsible for hypercoagulability, including spontaneous thrombus formation in blood vessels. Herein, we aimed to identify potential prognostic and diagnostic biomarkers in Japanese patients with LC and PVT. In total, 345 patients were divided into two groups: 40 patients who developed PVT (PVT group) and 305 who did not develop PVT (NPVT group). Among the 345 patients with LC, 81% (279/345) were deemed ineligible due to the presence of preventive comorbidities, active or recent malignancies, and organ dysfunction. The remaining 66 patients were divided into two groups: the PVT group (n = 33) and the NPVT group (n = 33). Plasma ADAMTS-13 activity (ADAMTS-13:AC) and the vWF antigen (VWF:Ag) were measured using enzyme-linked immunosorbent assays. Contrast-enhanced, three-dimensional helical computed tomography (CT) was used to detect and characterize PVT. ADAMTS-13:AC was significantly lower in the PVT group than in the NPVT group. No significant differences in plasma vWF:Ag or liver stiffness were observed between the two groups. ADAMTS-13:AC of <18.8 was an independent risk factor for PVT on multivariate analyses (odds ratio: 1.67, 95% confidence interval: 1.21-3.00, p < 0.002). The receiver operating characteristic analysis of ADAMTS-13:AC revealed an area under the curve of 0.913 in PVT detection. Patients with PVT having ADAMTS-13:AC ≥18.8 (n = 17) had higher albumin levels and better prognoses than those with ADAMTS-13:AC <18.8 (n = 16). No significant correlations of ADAMTS-13:AC levels with either fibrin degradation product or D-dimer levels were observed. ADAMTS-13:AC levels could be potential diagnostic and prognostic biomarkers for PVT in Japanese patients with LC.

[Advances in the treatment of thrombotic thrombocytopenic purpura].

Thrombotic thrombocytopenic purpura (TTP) is a fatal thrombotic disease caused by a marked decrease in the activity of ADAMTS13, a von Willebrand factor cleaving protease. In congenital TTP, ADAMTS13 activity is decreased by an abnormality in ADAMTS13, and in acquired TTP, by anti-ADAMTS13 autoantibody. Death from thrombosis in the acute phase has been an issue with conventional treatment of acquired TTP by plasma exchange or immunosuppressive therapy. However, the advent of caplacizumab, an anti-VWF nanobody, has made it possible to suppress thrombus formation and is expected to improve survival rates. In addition, some case series have shown the efficacy of caplacizumab without plasma exchange for acquired TTP, and this approach is being investigated in clinical trials. Fresh-frozen plasma is transfused to supply ADAMTS13 for congenital TTP, but frequent transfusions over a long period of time can lead to problems such as infection and allergic reactions. Novel therapies such as recombinant ADAMTS13 products and gene therapy are now under development, and show promise for future clinical use.

[Congenital thrombotic thrombocytopenic purpura diagnosed in adulthood after repeated thrombocytopenia since neonatal period].

A 27-year-old woman was diagnosed with idiopathic thrombocytopenic purpura in the neonatal period, and was admitted to our hospital after presenting with impaired consciousness, purpura, nausea and vomiting, with a platelet count of 10×109/l. Congenital thrombotic thrombocytopenic purpura (cTTP) was suspected on the basis of recurrent thrombocytopenia and impaired consciousness, so tests for ADAMTS13 activity and inhibitor were performed. ADAMTS13 activity was severely decreased, ADAMTS13 inhibitor was negative, and platelet count increased after transfusion of fresh frozen plasma. These findings and the results of genetic testing done on all family members led to a diagnosis of cTTP. cTTP requires differential diagnosis even in adults. If a patient diagnosed with ITP in childhood has a history or findings that suggest cTTP during follow-up observation, it is necessary to actively consider ADAMTS13 testing.

Annual incidence and severity of acute episodes in hereditary thrombotic thrombocytopenic purpura.

Hereditary thrombotic thrombocytopenic purpura (hTTP) is a rare thrombotic microangiopathy characterized by severe congenital ADAMTS13 deficiency and recurring acute episodes causing morbidity and premature death. Information on the annual incidence and severity of acute episodes in patients with hTTP is largely lacking. This study reports prospective data on 87 patients from the Hereditary TTP Registry (clinicaltrials.gov #NCT01257269) for survival, frequency, and severity of acute episodes from enrollment until December 2019. The 87 patients, followed up for a median of 4.2 years (range, 0.01-15 years), had a median age at overt disease onset and at clinical diagnosis of 4.6 years and 18 years (range, 0.0-70 years for both), respectively. Forty-three patients received regular plasma prophylaxis, whereas 22 did not, and treatment changed over time or was unknown in the remaining 22. Forty-three patients experienced 131 acute episodes, of which 91 (69%) occurred in patients receiving regular prophylaxis. This resulted in an annual incidence of acute episodes of 0.36 (95% confidence interval [CI], 0.29-0.44) with regular plasma treatment and of 0.41 (95% CI, 0.30-0.56) without regular plasma treatment. More than one-third of acute episodes (n = 51) were documented in children <10 years of age at enrollment and were often triggered by infections. Their annual incidence of acute episodes was significantly higher than in patients aged >40 years (1.18 [95% CI, 0.88-1.55] vs 0.14 [95% CI, 0.08-0.23]). The prophylactic plasma infusion regimens used were insufficient to prevent acute episodes in many patients. Such regimens are burdensome, and caregivers, patients, and their guardians are reluctant to start regular plasma infusions, from which children particularly would benefit.

Redefining outcomes in immune TTP: an international working group consensus report.

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a potentially fatal thrombotic microangiopathy caused by autoantibody-mediated severe deficiency of ADAMTS13. Standardized definitions of response, exacerbation, remission, and relapse were initially proposed in 2003 and modified by the International Working Group for TTP in 2017. These definitions, which have been widely used in clinical practice and research, are based primarily on the platelet count and are benchmarked against the timing of discontinuation of therapeutic plasma exchange (TPE). They do not incorporate ADAMTS13 activity or the temporizing effects on the platelet count of caplacizumab, a novel anti-von Willebrand factor (VWF) nanobody. In light of these limitations, the IWG aimed to develop revised consensus outcome definitions that incorporate ADAMTS13 activity and the effects of anti-VWF therapy, by using an estimate-talk-estimate approach. The updated definitions distinguish clinical remission and clinical relapse (defined primarily by platelet count) from ADAMTS13 remission and ADAMTS13 relapse (defined by ADAMTS13 activity). The revised definitions of exacerbation and remission are benchmarked against not only the timing of discontinuation of TPE but also that of anti-VWF therapy. Retrospective validation of the revised definitions is described, although they have yet to be prospectively validated. Clinical implications of the updated outcome definitions are also discussed and an example of their application to clinical practice is provided to highlight their clinical relevance.

Epidermal clearance of Candida albicans is mediated by IL-17 but independent of fungal innate immune receptors.

IL-17 plays important roles in host defense against Candida albicans at barrier surfaces and during invasive infection. However, the role of IL-17 in host defense after colonization of the epidermis, a main site of C. albicans infection, remains poorly understood. Using a murine model of epicutaneous candidiasis without skin abrasion, we found that skin inflammation triggered by epidermal C. albicans colonization was self-limiting with fungal clearance completed by day 7 after inoculation in wild-type mice or animals deficient in IL-17A or IL-17F. In contrast, marked neutrophilic inflammation in the epidermis and impaired fungal clearance were observed in mice lacking both IL-17A and IL-17F. Clearance of C. albicans was independent of Dectin-1, Dectin-2, CARD9 (caspase-recruitment domain family, member 9), TLR2 (Toll-like receptor 2) and MyD88 in the epidermal colonization model. We found that group 3 innate lymphoid cells (ILC3s) and γδT cells were the major IL-17 producers in the epicutaneous candidiasis model. Analyses of Rag2-/- mice and Rag2-/-Il2rg-/- mice revealed that production of IL-17A and IL-17F by ILC3s was sufficient for C. albicans clearance. Finally, we found that depletion of neutrophils impaired C. albicans clearance in the epidermal colonization model. Taken together, these findings indicate a critical and redundant function of IL-17A and IL-17F produced by ILC3s in host defense against C. albicans in the epidermis. The results also suggest that epidermal C. albicans clearance is independent of innate immune receptors or that these receptors act redundantly in fungal recognition and clearance.

Interleukin-10-producing plasmablasts exert regulatory function in autoimmune inflammation.

B cells can suppress autoimmunity by secreting interleukin-10 (IL-10). Although subpopulations of splenic B lineage cells are reported to express IL-10 in vitro, the identity of IL-10-producing B cells with regulatory function in vivo remains unknown. By using IL-10 reporter mice, we found that plasmablasts in the draining lymph nodes (dLNs), but not splenic B lineage cells, predominantly expressed IL-10 during experimental autoimmune encephalomyelitis (EAE). These plasmablasts were generated only during EAE inflammation. Mice lacking plasmablasts by genetic ablation of the transcription factors Blimp1 or IRF4 in B lineage cells developed an exacerbated EAE. Furthermore, IRF4 positively regulated IL-10 production that can inhibit dendritic cell functions to generate pathogenic T cells. Our data demonstrate that plasmablasts in the dLNs serve as IL-10 producers to limit autoimmune inflammation and emphasize the importance of plasmablasts as IL-10-producing regulatory B cells.

Application of a scoring system in Japanese patients diagnosed with atypical hemolytic uremic syndrome to assess the relationship between the score and clinical responses to eculizumab.

BACKGROUND: Atypical hemolytic uremic syndrome (aHUS) is caused by complement dysregulation and is generally diagnosed by exclusion from other disorders of thrombotic microangiopathy (TMA). Eculizumab, a terminal complement inhibitor, has been approved for aHUS treatment since 2013 in Japan. Recently, a scoring system was published to support diagnosis of aHUS. Herein we modified this scoring system to apply it to patients diagnosed with aHUS and treated with eculizumab, and assessed the association between the score and clinical responses to eculizumab. METHODS: One hundred eighty-eight Japanese patients who were clinically diagnosed with aHUS, treated with eculizumab, and enrolled in post-marketing surveillance (PMS) were included in this analysis. Some of parameters in the original scoring system were replaced with clinically similar parameters collected in the PMS to modify the system, hereafter referred to as the TMA/aHUS score, which ranges from -15 to 20 points. Treatment responses within 90 days after eculizumab initiation were also assessed, and the relationship between treatment response and TMA/aHUS scores calculated at TMA onset was explored. RESULTS: The median (range) TMA/aHUS score was 10 (3-16). Receiver operating characteristic curve analysis showed that the cutoff value of TMA/aHUS score to predict treatment response to eculizumab was estimated as 10, and negative predictive value indicated that ≥ 5 points was appropriate to consider assessing the treatment response to eculizumab; 185 (98%) patients had ≥ 5 points and 3 (2%) had < 5 points. Among the patients with ≥ 5 points, 96.1% showed partial response and 31.1% showed complete response. One of the three patients with < 5 points met partial response criteria. No significant difference in the TMA/aHUS scores was observed between survivors and non-survivors, suggesting that the score was not appropriate to predict the outcome (i.e., survival/death) in patients treated with eculizumab. CONCLUSION: Almost all patients clinically diagnosed with aHUS scored ≥ 5 points and responded to eculizumab. The TMA/aHUS score system could become a supporting tool for the clinical diagnosis of aHUS and probability of response to treatment with a C5 inhibitor. TRIAL REGISTRATION: This study was conducted as per good PMS practice guidelines for drugs (MHLW Ministerial Ordinance No. 171 of 2004).

Efficacy of lidocaine injection method for esophageal endoscopic submucosal dissection: single-center, double-blind, randomized controlled trial.

BACKGROUND: Intraoperative body movements are one of the causes of difficulty in performing esophageal endoscopic submucosal dissection (ESD) under conscious sedation. The use of local anesthetics as local injection materials during ESD may overcome this difficulty. We clinically evaluated the lidocaine injection method (LIM) in the submucosa during esophageal ESD. METHODS: This was a single-center, prospective, double-blind, randomized trial. Patients who underwent esophageal ESD under conscious sedation from June 2018 to May 2021 were included in this study. In the LIM group, lidocaine was used for submucosal injection during ESD; in the control group, ESD was performed without lidocaine. The primary outcome was the presence of body movements. RESULTS: Fifty patients were enrolled and randomized in a 1:1 ratio in two groups. The incidence of body movements was significantly lower in the LIM group (12% [3/25]) than in the control group (48% [12/25]; P = 0.01). The median additional dose of midazolam was 2 mg (interquartile range [IQR]: 0.5-4 mg) in the LIM group and 4 mg (IQR: 3-6 mg) in the control group, which was significantly lower in the LIM group (P < 0.01). The median visual analog scale score for endoscopist satisfaction was 7 (IQR: 5-8) in the LIM group and 5 (IQR: 4-6.5) in the control group, which was significantly higher in the LIM group. CONCLUSIONS: LIM during esophageal ESD reduced body movements while decreasing the level of sedation. Therefore, LIM during esophageal ESD is an option for maintaining good sedation (UMIN000032804).

Two pregnant women with immune-mediated thrombotic thrombocytopenic purpura: A case report.

Thrombotic thrombocytopenic purpura (TTP) during pregnancy is life-threatening. We encountered two pregnant women with immune-mediated TTP (iTTP). A 40-year-old primigravida woman was referred at 19 gestational weeks (GWs) owing to iTTP. She received plasma exchange (PE) and steroid therapies and delivered a live infant at 27 GWs by cesarean delivery. A 29-year-old primigravida woman was referred owing to intrauterine fetal death and thrombocytopenia at 20 GWs. She was diagnosed with iTTP and received PE therapy. She required additional PE and steroid therapies owing to relapse. Before her second pregnancy, she received prednisolone and hydroxychloroquine according to the therapy for systemic lupus erythematosus (SLE). She had induced labor at 37 GWs owing to decrease plasma level of a disintegrin-like and metalloproteinase with thrombospondin type 1 motif 13 (ADAMTS13) activity. Close monitoring of plasma ADAMTS13 activity level and treatments for underlying SLE may prevent iTTP relapse and lead to a good prognosis.

[Novel treatment strategies for acquired thrombotic thrombocytopenic purpura].

Thrombotic thrombocytopenic purpura (TTP) is a poor prognosis disease caused by platelet thrombi produced in the microvessels throughout the body. The thrombus is mainly composed of von Willebrand factor (VWF) and platelets. Acquired TTP is an autoimmune disease wherein autoantibodies against ADAMTS13, a VWF-cleaving enzyme, are produced and ADAMTS13 activity is markedly decreased. Plasma exchange using fresh-frozen plasma as a replacement fluid effective against acquired TTP was reported in 1991. Since then, plasma exchange and corticosteroids have been the standard of care in Japan. Caplacizumab, which is a monoclonal antibody against the VWF A1 domain, finally became available for use in 2022, and the number of cases is still increasing in Japan. A clinical trial of recombinant ADAMTS13 product is being conducted for congenital TTP, and an era is expected to come in the future when plasma exchange will no longer be necessary.

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.

Ratio of von Willebrand factor antigen to ADAMTS13 activity is a useful biomarker for acute-on-chronic liver failure development and prognosis in patients with liver cirrhosis.

AIM: Acute-on-chronic liver failure (ACLF) is associated with a high risk of short-term mortality after progression to multiple organ failure. A disintegrin-like and metalloproteinase with thrombospondin type-1 motifs 13 (ADAMTS13) is a metalloproteinase that specifically cleaves multimeric von Willebrand factor (VWF). An imbalance between ADAMTS13 enzyme and VWF substrate is associated with liver cirrhosis progression that induces ACLF. This study examined the relationship between ADAMTS13 and VWF and ACLF development to determine whether ADAMTS13 and VWF are useful predictive biomarkers for ACLF development and prognosis of patients with liver cirrhosis. METHODS: The study enrolled 67 patients with Child-Pugh class A and B liver cirrhosis. ADAMTS13 activity (ADAMTS13:AC) and VWF antigen (VWF:Ag) were measured using enzyme-linked immunosorbent assays. The ratio of VWF:Ag to ADAMTS13:AC (VWF:Ag/ADAMTS13:AC) was used to divide patients into two groups according to the classification and regression tree based on Gray model survival analysis. RESULTS: Compared with patients with Child-Pugh class A liver cirrhosis, class B patients had a higher VWF:Ag/ADAMTS13:AC and a higher risk of ACLF development. Cumulative incidence of ACLF was significantly higher in patients with high (>7.9) versus low (≤7.9) VWF:Ag/ADAMTS13:AC (hazard ratio [HR], 6.50; 95% CI, 2.31-18.29; p < 0.001). Cumulative survival was significantly lower in cirrhotic patients with high versus low VWF:Ag/ADAMTS13:AC (HR 5.11; 95% CI, 1.85-14.14; p = 0.002). CONCLUSIONS: For patients with liver cirrhosis, VWF:Ag/ADAMTS13:AC is associated with functional liver reserve and predicts the development of ACLF and the prognosis.

[Development of a novel aptamer blocking the interaction between the VWF A1 domain and platelet GP Ib for the treatment of arterial thrombosis].

A DNA aptamer to the von Willebrand factor (VWF) A1 domain, TAGX-0004, inhibits the binding of VWF to platelets. Nucleic acid aptamers are single-stranded DNA or RNA molecule forming three-dimensional structures that are capable of specifically binding to proteins and are expected to contribute to alternative medicine. ARC1779, an aptamer targeting the VWF A1 domain, had been evaluated in a phase II clinical trial of patients with acquired thrombotic thrombocytopenic purpura (aTTP); however, its development was terminated. Caplacizumab, an anti-VWF A1 domain nanobody, is now increasingly employed as first-line therapy for the treatment of aTTP in Western countries. However, there have been reports regarding adverse bleeding events and the high cost of the treatment. In this study, the inhibitory effects of TAGX-0004 were compared with those of ARC1779 and caplacizumab on in vitro platelet aggregation and thrombus formation. TAGX-0004 had an excellent high affinity to the VWF A1 domain and superior efficacy, such as its potent inhibitory activity in in vitro platelet aggregation and thrombus formation. Therefore, it can potentially overcome the problems associated with caplacizumab and can be developed as a promising drug not only for aTTP treatment but also for the treatment of the various VWF-mediated thrombotic disorders.

[The frontline of TMA management].

Thrombotic microangiopathy (TMA) is a pathological condition characterized by platelet thrombi-induced generalized microvascular occlusion, thrombocytopenia, and microangiopathic hemolytic anemia. TMA includes the life-threatening diseases thrombotic thrombocytopenic purpura (TTP) and hemolytic-uremic syndrome (HUS). TTP is different from HUS in that it has a severe deficiency in ADAMTS13 activity. Congenital TTP is caused by a lack of plasma ADAMTS13 activity caused by genetic mutations, and acquired TTP is caused by a secondary deficiency caused by autoantibodies. In Japan the only product approved for the treatment of congenital TTP is fresh frozen plasma containing ADAMTS13. Recombinant ADAMTS13 may provide a new treatment option for congenital TTP. The first-line treatment for acquired TTP is plasma exchange. Rituximab treatment should be considered for patients who are refractory or have relapsed. Caplacizumab is a nanobody that specifically targets von Willebrand factor. ISTH recently published guidelines recommending that caplacizumab be added to the initial treatment for acquired TTP. Atypical HUS (aHUS) is related with the dysregulation of the complement alternative pathway. Eculizumab, a monoclonal antibody that inhibits C5, was the first drug approved for aHUS, and it was found to be well-tolerated by patients and effective in clinical use. TMA is classified based on its etiology, and specific treatments for targeting various etiologies are now available.