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Background: The Chinese Haemophilia Individualized Prophylaxis Study (CHIPS), which was launched in 2016, reported a significant reduction in haemarthrosis over a one-year study. However, its long-term efficacy requires verification. This paper summarizes the clinical outcomes of 18 severe haemophilia A (SHA) patients who completed one year on the CHIPS and 3 more years of follow-up., Methods: Clinical follow-up was based on the CHIPS protocol (from July 2018 to July 2021). Escalation was based on index joint bleeding, and serial ultrasound (greyscale and colour Doppler) examinations of the index joints (both sides of the ankles, knees and elbows) were conducted every 6 months via a scoring system., Results: A total of 18 SHA patients completed the 3-year study. Fifteen patients dropped out due to the financial crisis during the COVID-19 pandemic in China. The median age was 5.4 (range 4.3-6.9) years. A significant reduction in haemarthrosis was achieved, with mean annual bleeding rates reduced from 18.9 ± 2.8 to 1.7 ± 0.4 (p < 0.001), annual joint bleeding rates from 3.1 ± 0.7 to1.2 ± 0.3 (p < 0.028). 5 out of 8 target joint resolved. Sixteen doses were escalated. At study exit, the heterogeneous treatment outcomes of the SHA boys were 5 at step 4 (20-25 lU/kg, every other day), 10 at step 3 (15-20 IU/kg, 3×/week), 2 at step 2 (10-15 lU/kg, 3×/week) and 1 at step 1 (10-15 lU/kg, 2×/week). The mean FVIII consumption was 2964 IU/kg/year, with savings. The quality of life improved, with Canadian Haemophilia Outcomes-Kids Life Assessment Tool (CHO-KLAT, Chinese Version 2.0) scores ranging from 68.8 to 78.8. There was no change in the ultrasound score., Conclusion: Our follow-up data on the 18 SHA boys after completing one year on the CHIPS verify the long-term efficacy of the CHIPS for haemarthrosis reduction, joint health preservation, improvement in the quality of life of the boys and cost savings., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Objective: To investigate the influence of the dead space in disposable blood sampling needle on activated partial thromboplastin time (APTT), FVIII level and pharmacokinetic (PK) profiles in children with hemophilia., Methods: Children (<18 years) with severe hemophilia A were enrolled. After three days' washout-period, blood samples were collected at pre-dose, 1 h, 3 h, 9 h, 24 h and 48 h post-infusion. At each timepoint, two 2 mL vacuum tubes with 3.2% trisodium citrate were used. The first tube was signed as 'non-standard' (NS) and the second tube was signed as 'standard' (S). FVIII activities were evaluated by one-stage assay. WAPPS-Hemo was used to generate PK profiles like half-life time (t 1/2 ), clearance (CL), trough level and time to 1, 2 and 5IU/dL after a dose of 50 ± 10IU/dL. The FVIII activities at 9 h and 24 h post-infusion were put into WAPPS and thus brought four combinations by true or biased FVIII level that used., Result: Compared with standard-collected blood samples, prolonged APTT results ( P -values < 0.01) and decreased FVIII activity ( P -values < 0.05) were revealed in those non-standard blood samples. The corresponding bias was in positive relation to both APTT-S (r = 0.44, P  < 0.0001) and FVIII-S level(r = 0.68, P  < 0.001). The FVIII bias percentage got larger as FVIII-S level reduced (r = -0.24, P  < 0.01). During the four combinations of FVIII activity at 9 h and 24 h, statistically longer t 1/2 , lower CL and longer time to 1, 2 or 5IU/dL were observed in 9H-S&24H-S group and 9H-NS&24H-S group., Conclusion: While using vacuum tubes for clotting indicators and PK profiles, the dead space of blood sampling needle should be eliminated in advance.

Background: Physical activity is a crucial part of an active lifestyle for haemophiliac children. However, the fear of bleeds has been identified as barriers to participating physical activity for haemophiliac children even with prophylaxis. Lack of evidence and metrics driven by data is key problem., Objectives: We aim to develop machine learning models based on clinical data with multiple potential factors considered to predict risk of physical activity bleeding for haemophilia children with prophylaxis., Methods: From this cohort study, we collected information on 98 haemophiliac children with adequate prophylaxis (trough FVIII:C level > 1 %). The involved potential predictor variables include demographic information, treatment information, physical activity, joint evaluation, and pharmacokinetic parameters, etc. We applied CoxPH, Random Survival Forests (RSF) and DeepSurv to construct prediction models for the risk of bleeding during physical activities. All three survival analysis models were internally and externally validated., Results: A total of 98 patients were enrolled in this study. Their median age was 7.9 (5.5, 10.2) years. The CoxPH, RSF and DeepSurv models' discriminative and calibration abilities were all high, and the RSF model had the best performance (Internal validation: C-index, 0.7648 ± 0.0139; Brier Score, 0.1098 ± 0.0015; External validation: C-index, 0.7260 ± 0.0154; Brier Score, 0.0930 ± 0.0018). The prediction curves demonstrated that the developed RSF model can distinguish the risks well between bleeding and non-bleeding patients, as well as patients with different levels of physical activity. Meanwhile, the feature importance analysis confirmed that physical activity bleeding was deduced by comprehensive effects of various factors, and the importance of different factors on bleeding outcome is discrepant., Conclusions: This study revealed from the mechanism that it is necessary to incorporate multiple factors to accurately predict physical activity related bleeding risk. In clinical practice, the designed machine learning models can provide guidance for children with haemophilia A to positively participate in physical activity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Objectives: To assess current treatment-related outcomes for children with severe and moderate haemophilia A (cHA) in China., Methods: This cross-section Patient Report Outcome (PRO) report collected PRO data of severe and moderate cHAs registered in the 'Hemophilia Home Care Center' database (http://web.bjxueyou.cn) between January 2021 and November 2022. Data included records of bleeding, activities, and concentrates consumption. All patients had a confirmed diagnosis of moderate or severe haemophilia A (FVIII: C ≤ 5%) and were < 18 years old., Results: Among 1038 analysable cases, 9.6% of children with inhibitors had a higher rate of intracranial haemorrhage, dropout school rate, and higher FVIII consumption than children without inhibitors. Among 100 children with inhibitors, 36 patients were treated without immune tolerance induction (ITI), 14 patients with irregular treatment and 50 patients received ITI. Children with ITI had a lower ABR (2.4 (0,6.6) vs. 13.4 (9.5, 26.6), p<.001) and AJBR (0 (0, 3.1) vs. 8.9 (1.6, 19.3), p < .001) compared to those without ITI. Among 938 children without inhibitors, 28.5% received on-demand treatment and 71.5% received prophylaxis. Of 528 children with 1343.8 (1050.4, 2922.9)IU/kg/year median FVIII consumption, 43.0% received low-dose, 43.2% received intermediate-dose, and 13.8% received high-dose regimen; these children with prophylaxis had a lower ABR (3.1 (0, 10.7) vs. 12.8 (2.4, 45.5), p < .001), AJBR (0.5 (0, 3.9) vs. 3.0 (0, 12.0), p < .001) and disability rate (9.0% vs.18.5%, p = .032) compared to children who received on-demand treatment., Conclusion: The high rate of drop-out of school and disability still present a huge gap to meet the needs in China. It is necessary to improve the level of medical accessibility and medicine affordability and strengthen the patient/parent's education in China., (© 2023 John Wiley & Sons Ltd.)

Background: The predictors of immune tolerance induction (ITI) outcomes in hemophilia A (HA) patients with the same F8 genetic background have not yet been evaluated, although the F8 genotype is strongly associated with ITI response. This study aims to explore the predictors of ITI outcomes in the same F8 genetic background by focusing on intron 22 inversion (Inv22) patients with high-responding inhibitors., Methods: HA children with Inv22 and high-responding inhibitors who received low-dose ITI therapy over 24 months were included in this study. ITI outcomes were centrally assessed at the 24th month of treatment. The predictive ability of clinical variables to identify ITI success was determined using the receiver operating characteristic (ROC) curve, and the predictor of ITI outcomes was analyzed on the multivariable Cox model., Results: Among the 32 patients investigated, 23 (71.9 %) achieved success. In univariate analysis, interval time from inhibitor diagnosis to ITI start (interval-time) was significantly associated with ITI success (P = 0.001); however, inhibitor titers showed no significance (P > 0.05). The interval-time demonstrated a good predictive value for ITI success with the area under the ROC curve of 0.855 (P = 0.002), and the cutoff value was 25.8 months (sensitivity, 87.0 %; specificity, 88.9 %). In the multivariable Cox model which considered success rate and time to success, interval-time was the only independent predictor (<25.8 months vs. ≥25.8 months, P = 0.002)., Conclusions: The interval-time was first identified as a unique predictor of ITI outcomes in HA patients with high-responding inhibitors under the same F8 genetic background (Inv22). An interval-time of <25.8 months was associated with increased ITI success and reduced time to success., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

Background: Shorter interval-time from inhibitor detection to starting immune tolerance induction (ITI) might predict better ITI outcomes for severe Hemophilia A (SHA) patients with high-risk-inhibitors. However, the prediction-impact of interval-time for these patients on low-dose ITI strategy remained unclear., Objectives: To explore the relationship between interval-time and low-dose ITI outcomes in Chinese SHA children with high-risk-inhibitors., Methods: This was a single-center, retrospective study on SHA children with high-risk-inhibitors (each with immediate pre-ITI inhibitor titer>10 Bethesda Units/mL) undergoing low-dose ITI strategy for ≥24 months. ITI outcomes and their predictive factors were evaluated at the 24th month treatment for each patient. The predictive ability of interval-time on ITI success was determined using receiver operating characteristic (ROC) curve., Results: Among 47 patients investigated, 34 (72.3 %) achieved success. Independent predictor for ITI-outcome on multivariate analysis included the interval-time (p = 0.007) and peak inhibitor-titer (p = 0.011). Shorter interval-time predicted ITI success [cut-off value = 22.3 months, area under ROC-curve (AUC) = 0.701] and early-ITI success within 12 month (cut-off value = 9.4 months AUC = 0.704). Linear regression analysis suggested each month interval-time delay delayed success by 0.1552 month. Unlike the interval-time, peak inhibitor-titer had no success-predictive value in high-peak inhibitor-titer patients on ITI with immunosuppressants., Conclusions: Interval-time represented a strong predictive value for outcomes in our low-dose ITI strategy for SHA patients with high-risk-inhibitors. Shorter interval-time was associated with higher success rate and earlier success achievement. The respective interval-time cut-off values were 22.3 months for ITI success and 9.4 months for early-success., Competing Interests: Declaration of competing interest The authors stated that they had no conflicts of interest or bias., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Introduction: As standard care of severe haemophilia A (SHA), prophylaxis should be individualised., Aim: This study aimed to investigate the effectiveness of this new-proposed individualised prophylaxis protocol., Methods: Boys with SHA were enrolled and followed a PK-guided, trough-level escalating protocol of prophylaxis after a six-month observational period. In the next 2 years, clinical assessments including joint bleeds, ultrasound (US) scores and Haemophilia Joint Health Score (HJHS) in both sides of ankles, knees and elbows were conducted every 6 months as a scoring system, which determined whether the trough level's escalation. Adjustment of dosing regimen was based on WAPPS-Hemo., Results: Fifty-eight SHA boys were finally analysed. Their age and bodyweight were 5.3(2.8,6.9) years and 21.5(16,25) kg. During the study, 47 escalations were conducted. At study exit, the patient number and proportion of different trough level groups were: < 1 IU/dl, 17.2% (10/58); 1-3 IU/dl, 53.5% (31/58); 3-5 IU/dl, 15.5% (9/58); > 5 IU/dl, 13.8% (8/58). Significantly reduced annualised bleeding rate [4(0,8) to 0(0,2), p < .0001] and annualised joint bleeding rate [2(0,4) to 0(0,.25), p < .0001] was observed at study exit as well as the continuous trend of increased zero bleeding proportion (ZBP) (27.6%-69.0%) and zero joint bleeding proportion (46.5%-81.3%). Besides, 85% (6/7) of the target joints vanished. Statistical improvements of US scores (p = .04) and HJHS (p = .02) were also reported at study exit., Conclusion: Our results showed the effectiveness of our protocol based on individualised target trough level and emphasise the importance of personalised prophylaxis., (© 2021 The Authors. Haemophilia published by John Wiley & Sons Ltd.)

Introduction: Development of haemophilia B inhibitors (HBI) results in the ineffectiveness of FIX replacement therapy. Inhibitor eradication by immune tolerance induction (ITI) is therefore necessary. In HBI, ITI even at high FIX dose is less effective and has a higher risk of severe complications., Aim: To characterize clinical features and outcome of ITI on HBI., Methods: This retrospective study was conducted in Haemophilia Paediatric Comprehensive Care Centre of China. We used low-dose ITI (25-50 FIX IU/kg/three-times-weekly to every-other-day) with domestic prothrombin complex concentrate (PCC), combined with two successive immunosuppressive (IS) regimens., Results: Sixteen HBI children, representing 5.7% of all and 14.4% of our severe registered HB patients, were enroled. Seven cases reported allergic reactions (ARs) proximal to inhibitor development. The historic peak inhibitor titre was median 54.2 (range 4.7-512) BU, and 15 (93.8%) had high-titre inhibitors. Twelve patients adherent to ITI were analysable. Of the nine ITI patients who received rituximab/prednisone (IS Regimen-1), four achieved tolerization in 1.4-43.3 months. Two subsequently relapsed but re-tolerized after a second course of IS Regimen-1. During ITI, the median treated bleed was .39/month (82.7% reduction from before ITI), and the incidence of AR and nephrotic syndrome (NS) complications was each at 22% (2/9). Three ITI patients received modified 'Beutel' protocol (IS Regimen-2) using multiple-IS-drugs, and two had rapid tolerization (.8 and 1.8 months)., Conclusions: Inhibitor eradication could be achieved by low-dose ITI protocol using PCC combined with IS. Larger studies are needed to confirm if ITI with IS Regimen-2 is more effective with less complications., (© 2022 John Wiley & Sons Ltd.)

Introduction: As the most commonly used FVIII concentrate in China, the individualized pharmacokinetics (PK) and clinical outcomes of Kovaltry (BAY81-8973) are not fully investigated in this population., Materials and Methods: Pediatric patients with severe hemophilia A were enrolled in Beijing Children's Hospital. After a three-day washout, they received PK tests after a single-dose infusion of 50 IU/kg. The blood samples were collected with a six-point assay. One-stage-based activated partial thromboplastin time was used for FVIII activity. The PK parameters were generated by WinNonlin software. The bleeding rates were calculated by their routine therapy record. The ultrasound was used to evaluate their both sides of knees, elbows and ankles., Result: Sixty-one boys with severe hemophilia A were enrolled and their median age was 5.73 years. Twenty-nine of them were blood group-O. Compared with blood group-O patients, those non-O patients showed longer t 1/2 (15.26 vs. 13.03 h, P < 0.001) and reduced CL (3.04 vs. 3.66 mL/kg/h, P < 0.05). Patients with higher VWF:Ag level had longer half-life time (t 1/2 ) (r = 0.60, P < 0.0001) and lower clearance (CL) (r = -0.45, P < 0.001). Patients with higher trough level showed decreased bleeding rates compared with those owning a trough level below 1 IU/dL (P < 0.05). In general, the zero bleeding rates raised with elevation of trough level. However, 20-30% of patients with low trough level (<1 IU/dL) also showed no bleeds and 10-20% of patients with high trough level (>5 IU/dL) still suffer bleeds. An inconsistency of 28% between joint bleeds and ultrasound evaluation was showed., Conclusion: This study revealed the great inter-individual variability in PK parameters, clinical bleeding phenotype and joint vulnerability, which all should be considered in treating hemophilia A., (Copyright © 2022. Published by Elsevier Ltd.)

Purpose: Hemophilia B (HB) is a hereditary bleeding disorder caused by a deficiency of coagulation factor IX (FIX), which represents 15% to 20% of all patients with hemophilia. Clinical studies have found significant benefits of prophylaxis treatment with FIX versus on-demand (OD) treatment. However, these benefits are associated with an increase in FIX consumption and a considerable increase in cost. Most Chinese children with HB receive OD treatment. Only a small proportion of patients with HB receive prophylaxis treatment in China. The patients with inhibitors could result in more complicated bleeding events, joint status, or treatment patterns. The objective of this study is to assess the cost-effectiveness of prophylaxis compared with OD treatment in children with HB without inhibitors from the Chinese health care perspective., Methods: A Markov model was used to analyze cost-effectiveness by comparing prophylaxis with OD treatment. The model uses a 17-year time horizon with a yearly cycle. Transition probabilities and utility weights were estimated using published studies. The cost data for patients with HB were collected from Beijing Children's Hospital and Capital Medical University. One-way and probabilistic sensitivity analyses were performed to assess the robustness of the results., Findings: The model projects that prophylaxis has an incremental 1.23 quality-adjusted life-years (QALYs). The incremental cost per QALY gained for individuals with HB receiving prophylaxis was ¥155,709.80 ($23,530.36) compared with the OD group, which is under the willingness-to-pay threshold (3 times the gross domestic product per capital according to the World Health Organization recommendations) in China of ¥193,932 ($29,306.37). Moreover, 1-way sensitivity analysis found that the results were sensitive to the utility of nonarticular bleeding. The lower this parameter is, the higher the probability is of the incremental cost-effectiveness ratio for prophylaxis not being cost-effective. This finding infers that when the patients have a better QALY (higher utility) at the beginning, the cost for benefit from prophylaxis treatment is lower. The results of the probabilistic sensitivity analyses indicate that the probability of prophylaxis being cost-effective is 89.3%., Implications: Although prophylaxis is a costly treatment, the results of this study indicate that it is cost-effective compared with OD treatment for children with HB in China., (Copyright © 2021. Published by Elsevier Inc.)

Introduction: Haemophilia A is a rare inherited bleeding disease caused by the deficiency of coagulation factor VIII (FVIII). The main treatment protocol is to administer regular exogenous FVIII concentrate infusions. With the discovery of variability in individualised pharmacokinetics (PK) and bleeding phenotype, the previous weight-based approach needs to be replaced by more advanced PK-tailored prophylaxis with an accurate evaluation system. In this study, we combine individualised PK profiles and a complementary evaluation system to guide prophylaxis in paediatric patients with haemophilia A., Methods and Analysis: This is a single-centre, prospective single-arm study. The aim of this study is to assess the effectiveness of a new strategy combining PK and a complementary evaluation system to treat haemophilia A in Chinese paediatric patients. Sixty paediatric patients with haemophilia will be recruited. After PK testing, they will receive a PK-guided stepup prophylaxis in the next 2 years. The dosing regimen will be determined according to individualised PK profiles and complementary evaluation findings. Related indicators at the end of the study will be compared with the values at treatment initiation to examine the effectiveness of this new strategy. The demographic data of the investigated patients will be summarised by descriptive statistics. Quantitative data will be described by summary statistics, including arithmetic median, range, mean and arithmetic SD. Analyses will use t-test to compare indicators such as bleeding rate and imaging score at both ends of the study as well as during follow-up., Ethics and Dissemination: The study has been approved by the Ethics Committee of Beijing Children's Hospital (Number 2020-Z-095). The findings will be presented at international meetings such as World Federation of Hemophilia World Congress. Related manuscripts will be submitted to peer-review journals such as Blood and Hemophilia ., Trial Registration Number: ChiCTR2000037821; Pre-results., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: The traditional weight-based dosing regimen can lead to under- or overdosage due to the interindividual variability of pharmacokinetic (PK) parameters. PK-guided prophylaxis can be an optimized therapy choice., Aim: This study aimed to investigate the clinical outcomes of PK-guided prophylaxis in 46 boys with severe haemophilia A., Methods: Forty-six boys with severe haemophilia A were enrolled in Beijing Children's Hospital. The PK tests were performed using a five-point assay. PK parameters were calculated using WinNonlin software. The dosing regimen and bleeding rates recorded during the observation period. The adjustment was based on PK evaluation, bleeding details, doctor's advice and patients' choice., Results: The half-life time, in vivo recovery and clearance of Kovaltry were 14.34 ± 2.68 h, 1.78 ± 0.29 kg/dl and 3.38 ± 0.94 ml/kg/h, respectively. In 18 patients without any change in the dosing regimen, the trough level was 4.0 ± 2.41 IU/dl and the bleeding rates were similar after PK tests. For patients with a higher trough level after adjustment, higher dose and frequency were observed, as well as a higher trough level. Also, reduced annual bleeding rate (ABR), annual joint bleeding rate and annual spontaneous bleeding rate (ASBR) were found. In five patients with a reduced trough level, lower infusion frequency and weekly coagulation factor VIII (FVIII) consumption were observed, with no statistically significant difference in ABR and ASBR., Conclusion: PK-guided prophylaxis can help haemophiliac patients improve quality of life by decreasing bleeds with appropriate FVIII consumption and reducing infusion frequency without increments in bleeds, thus optimizing haemophilia treatment., (© 2021 John Wiley & Sons Ltd.)

Background: Kovaltry (BAY81-8973) is an unmodified full-length factor VIII (FVIII) concentrate that enhances the pharmacokinetic (PK) profiles as compared to some other standard half-life time FVIII concentrates. However, the PK of Kovaltry in haemophiliac patients aged <12 years has not been reported previously., Aim: To investigate the pharmacokinetics and clinical outcomes of Kovaltry in 35 paediatric patients aged <12 years., Methods: A total of 35 boys with severe haemophilia A were enrolled from August 2019 to May 2020 in Beijing Children's Hospital. After 72-hour washout, PK tests were performed post-infusion of 50 IU/kg Kovaltry in a five-timepoint assay. WinNonlin software was used to generate individual PK parameters. The dose, frequency and bleeding details were collected within the first 6 months after switching to Kovaltry from other FVIII concentrates., Results: Compared to the blood group O, patients with blood group non-O showed longer mean half-life (t 1/2 ) (p < .01), lower mean clearance (CL) (p = .01) and similar in vivo recovery (IVR) (p = .51). Higher von Willebrand factor antigen (VWF:Ag) level was correlated to longer t 1/2 (p < .0001) and lower CL (p < .01). IVR was correlated to body mass index (BMI) (p < .0001). Patients with trough level >3 IU/dL demonstrated lower annual bleeding rate (ABR) (p < .01), annual joint bleeding rate (AJBR) (p < .01) and annual spontaneous bleeding rate (ASBR) (p < .01)., Conclusion: This study firstly reported the PK profiles of Kovaltry in 35 paediatric patients <12 years old. The great inter-individual variability of PK parameters was also confirmed in these patients. VWF:Ag and blood group were major influencing factors of t 1/2 and CL of Kovaltry, while BMI was a vital predictor for IVR. Patients with high trough FVIII level in routine prophylaxis had reduced bleeding rates., (© 2021 John Wiley & Sons Ltd.)

The factor VIII (FVIII)-neutralizing antibody (inhibitor) seen in 25%-30% of patients with severe haemophilia A (SHA). Vaccination is a non-genetic risk factor of inhibitor development as 'danger signal' which may provide a pro-inflammatory microenvironment to increase FVIII immunogenicity. We reported a previously treated SHA patient postponed the first vaccination to 15-month age received diphtheria-pertussis-tetanus intramuscularly. At 18-month age, the patient received Hepatitis A intramuscularly and Varicella Zoster Virus subcutaneously with 2 weeks interval and FVIII infusion was given <24 h prior for each. Successive bleedings occurred 1 week later with inefficacy of FVIII replacement. High-titre inhibitor was tested at 117 exposure days. This case suggested that continuous vaccinations in close proximity to FVIII could induce inhibitor. The relationship between vaccination and FVIII immunogenicity still needs to be revealed by further study.

Objective: To study the current situation of coagulation factor VIII (FVIII) inhibitor development in children with hemophilia A (HA) through a cross-sectional survey, and to explore the risk factors of inhibitor development in order to provide evidence for further prevention and management strategies., Method: The clinical data of outpatients with hemophilia A in Beijing Children's Hospital seen from November 2012 to May 2013 were collected, FVIII inhibitor was screened and analyzed its risk factors., Result: A total of 102 HA children were enrolled, 5 were mild cases, 32 were moderate, and 65 were severe cases; the median age on enrollment was 55.5 (3.0-200.0) months:19(18.6%) of patients had inhibitors and 9 (8.8%) had low-titer inhibitors, 10 (9.8%) had high-titer inhibitors. Receiving FVIII treatment for life-threatening bleeding (P = 0.03) ,OR 4.10 (95%CI:1.17-14.32) was a risk factor for inhibitor generation and patients within 20 exposure days have more chances of inhibitor development (P = 0.04) ,OR 3.32 (95%CI:1.02-10.86) . High and intense FVIII exposure within short term was the risk factor for high titer inhibitor development (P = 0.01) ,OR 5.25 (95%CI:1.45-21.92) ., Conclusion: Intense FVIII exposure for severe hemorrhage was the risk factor of inhibitors development especially of high titer inhibitors.

Importance: It remained unclear that the efficacy comparison between low‐dose immune tolerance induction (LD‐ITI) incorporating immunosuppressants (IS) when severe hemophilia A (SHA) patients had inhibitor‐titer ≥200 Bethesda Units (BU)/mL (LD‐ITI‐IS200 regimen) and LD‐ITI combining with IS when SHA patients had inhibitor‐titer ≥40 BU/mL (LD‐ITI‐IS40 regimen). Objective: To compare the efficacy of the LD‐ITI‐IS200 regimen with that of the LD‐ITI‐IS40 regimen for SHA patients with high‐titer inhibitors. Methods: A prospective cohort study on patients receiving LD‐ITI‐IS200 compared to those receiving LD‐ITI‐IS40 from January 2021 to December 2023. Both received LD‐ITI [FVIII 50 IU/kg every other day]. IS (rituximab + prednisone) was added when peak inhibitor tier ≥200 BU/mL in the LD‐ITI‐IS200 regimen and ≥40 BU/mL in the LD‐ITI‐IS40 regimen. Success is defined as a negative inhibitor plus FVIII recovery ≥66% of the expected. Results: We enrolled 30 patients on LD‐ITI‐IS200 and 64 patients on LD‐ITI‐IS40, with similar baseline clinical characteristics. A lower IS‐use rate was discovered in the LD‐ITI‐IS200 regimen compared to the LD‐ITI‐IS40 regimen (30.0% vs. 62.5%). The two regimens (LD‐ITI‐IS200 vs. LD‐ITI‐IS40) had similar success rate (70.0% vs. 79.7%), median time to success (9.4 vs. 10.6 months), and annualized bleeding rate during ITI (3.7 vs. 2.8). The cost to success was lower for LD‐ITI‐IS200 than for LD‐ITI‐IS40 (2107 vs. 3256 US Dollar/kg). Among patients with peak inhibitor‐titer 40–199 BU/mL, 10 non‐IS‐using (on LD‐ITI‐IS200 regimen) and 28 IS‐using (on LD‐ITI‐IS40 regimen) had similar success rates (70.0% vs. 78.6%) and time to success (9.0 vs. 8.8 months). Interpretation: In LD‐ITI, IS are not necessary for inhibitor titer <200 BU/mL. [ABSTRACT FROM AUTHOR]

Importance: The use of factor VIII (FVIII) concentrates under pharmacokinetic (PK) guidance has become the main approach for treatment of hemophilia. However, limited PK research has been conducted in Chinese pediatric patients. Objective: To investigate the PK parameters of various FVIII concentrates in Chinese pediatric patients. Methods: Seventy‐nine patients were enrolled (28 treated with Kogenate FS®, 23 treated with Advate ®, and 28 treated with GreenMono™). All enrolled patients participated in single‐dose PK analysis after at least a 3‐day washout period. Blood samples were collected predose, as well as at 1 h, 9 h, 24 h, and 48 h after infusion; FVIII levels were measured using a one‐stage clotting assay. von Willebrand Factor Antigen (VWF:Ag) levels and blood types were also determined. PK parameters were evaluated by WAPPS‐Hemo. Results: Mean values of terminal elimination half‐life time (t1/2) for the Kogenate FS®, Advate®, and GreenMono™ FVIII groups were 12.24 h, 10.18 h, and 9.62 h; median clearance values were 4.16, 6.23, and 5.11 mL·kg−1·h−1; and median in vivo recovery values were 1.97, 1.55, and 1.61 IU/dL per IU/kg. Longer t1/2, higher in vivo recovery, and lower clearance were observed in patients with higher VWF:Ag level who were treated with recombinant concentrates. Interpretation: Chinese pediatric patients with hemophilia had FVIII PK characteristics similar to those previously observed in non‐Chinese children, including large variation among individuals. VWF:Ag level and FVIII brand were associated with differences in FVIII PK. Thus, PK‐guided dosing should be used to optimize individualized therapy in Chinese children. [ABSTRACT FROM AUTHOR]