Clinical Predictors and Prediction Models for rFVIII-Fc Half Life in Real-World People with Severe Hemophilia A.

The half life of recombinant factor VIII-Fc (rFVIII-Fc) for people with hemophilia A (PwHA) varies greatly. Understanding the factors influencing the variation and assessment of rFVIII-Fc half life is important for personalized treatment. Eighty-five severe-type PwHA with rFVIII-Fc treatment receiving an evaluation of half life by the Web-Accessible Population Pharmacokinetic (PK) Service-Hemophilia during 2019-2021 were retrospectively enrolled. The 50-patient PK profiles before 2021 were used for analysis and developing prediction models of half life, and the 35-patient PK profiles in 2021 were used for external validation. The patients in the development cohort were aged 8-64, with a median rFVIII-Fc half life of 20.75 h (range, 8.25-41.5 h). By multivariate linear regression analysis, we found two, four, and five predictors of rFVIII-Fc half life for the blood groups non-O, O patients, and overall patients, respectively, including baseline VWF:Ag, BMI, VWF:activity/VWF:Ag ratio, body weight, O blood group, inhibitor history, HCV infection, and hematocrit. The three prediction equations of rFVIII-Fc half life (T) were respectively developed as T for non-O group patients = -0.81 + 0.63 × (BMI, kg/m2) + 6.07 × (baseline VWF:Ag, IU/mL), T for O group patients = -0.68 + 13.30 × (baseline VWF:Ag, IU/mL) + 0.27 × (BW, kg) - 1.17 × (BMI, kg/m2) + 16.02 × (VWF:activity/VWF:Ag ratio), and T for overall patients = -1.76 + 7.24 × (baseline VWF:Ag, IU/mL) - 3.84 × (Inhibitor history) + 2.99 × (HCV infection) - 2.83 × (O blood group) + 0.30 × (Hct, %), which explained 51.97%, 75.17%, and 66.38% of the half life variability, respectively. For external validation, there was a significant correlation between the predicted and observed half lives in the validation cohort. The median half life deviation was +1.53 h, +1.28 h, and +1.79 h for the equations of non-O group, O group, and overall group patients, respectively. In total, eight predictors influencing rFVIII-Fc half life were identified. Prediction equations of rFVIII-Fc half life were developed for the non-O and O blood groups and overall PwHA with a good degree of external validation. The equations could be applied to patients aged 8-64 without the need for PK blood sampling and clinically valuable for personalized therapy.

Real-world bleeding outcomes and product utilization in people with severe-type hemophilia A before and after switching to extended half-life rFVIIIFc prophylaxis therapy.

BACKGROUND: Recombinant factor VIII-Fc (rFVIIIFc) became available in Taiwan in 2018. Before this date, no people with hemophilia A (PwHA) were enrolled in a clinical trial of rFVIIIFc. We investigated changes in bleeding outcomes and product utilization in PwHA switching from rFVIII to rFVIIIFc. METHODS: Data were collected for Taiwanese PwHA (severe-type) who switched from rFVIII to rFVIIIFc, including annualized bleeding rate (ABR) and weekly dose consumption 12 months pre-switch and > 6 months post-switch. RESULTS: The 51 patients were divided into 3 groups according to their pre-switch treatment: on-demand treatment, intermittent periodic prophylaxis, and regular prophylaxis. In every group, the post-switch median ABR was significantly reduced, with no significant differences between groups. Meanwhile, the post-switch median weekly dose of each group was significantly increased. In 32 patients on pre-switch prophylaxis, switching brought a further reduction in median ABR, associated with a significant increase in median weekly dose. No adverse effects or novel inhibitor development were seen. CONCLUSION: This is the first report from Asia on real-world experience of rFVIIIFc, showing that switching to rFVIIIFc prophylaxis led to further reduction in ABR and increase in weekly dose for all patient groups, even those on pre-switch rFVIII prophylaxis.

A Comparative Evaluation of an Automated Functional Assay for Von Willebrand Factor Activity in Type 1 Von Willebrand Disease.

BACKGROUND: von Willebrand factor ristocetin cofactor activity (VWF:RCo) is the standard functional assay used for von Willebrand disease (VWD) diagnosis. However, it has some drawbacks including being time consuming and labor intensive and having high inter-laboratory variability. The HemosIL VWF activity assay has the advantages of both high speed and automation. The purpose of this study was to prospectively compare these two functional assays for type 1 VWD detection. METHODS: Plasma samples from 108 subjects were assessed in this study. HemosIL VWF activity was measured with the HemosIL latex immunoturbidimetric commercial kits by the ACL TOP coagulation analyzer. VWF:RCo was measured by platelet aggregation method. Pearson correlation analyses were performed to estimate the correlation of HemosIL VWF activity with VWF:RCo. Receiver-operator characteristic (ROC) curve analysis was used to evaluate the performance of the two diagnostic tests. RESULTS: The correlation coefficient between VWF:RCo and HemosIL VWF activity was 0.874 overall and was 0.761 and 0.811 in the cohorts of type 1 VWD and non-VWD, respectively. The sensitivity and specificity of HemosIL VWF activity assay for type 1 VWD identification were 94.7% and 80.0%, respectively, and the ROC curve of HemosIL VWF activity was larger than that of VWF:RCo (0.928 vs 0.863, p=0.0138). Finally, the positive and negative predictive values of the HemosIL VWF activity assay for type 1 VWD detection were 72.0% and 96.6%, respectively. CONCLUSION: Our results demonstrate that the HemosIL VWF activity assay was an effective method for type 1 VWD screening and diagnosis. It carried good sensitivity and specificity and had a higher ROC curve than VWF:RCo besides showing good correlation with VWF:RCo. With its advantages of greater speed and automated performance, these results suggest that the HemosIL VWF activity assay was reliable and precise in the clinical setting.

Deep intronic variant c.5999-277G>A of F8 gene may be a hot spot mutation for mild hemophilia A patients without mutation in exonic DNA.

BACKGROUND: In 10%-18% of mild-type hemophilia A (HA) patients, mutations cannot be found by routine DNA analysis. OBJECTIVE: We aimed to identify the genetic defects by mRNA analysis of F8 gene in mild HA patients without mutation in exonic DNA. PATIENTS AND METHODS: From 2006 to 2016, we identified F8 exon mutations in 39 of 49 mild HA patients using routine genetic testing. We then evaluated the 10 remaining patients from six unrelated families without exonic DNA mutation by performing cDNA sequence analysis. RESULTS: Nine of the 10 (90%) patients were confirmed to have F8 gene mutation. Eight patients from four unrelated families were notably found to have presence of an aberrant 675-bp fragment. Sequencing of this fragment showed that there were two separate new alternative splicing exons of 35 bp and 55 bp within intron 18, which formed a 90-bp insertion between exon 18 and exon 19 (E18ins90bpE19) in the mRNA. Based on direct sequencing, this alternative splicing transcript appears to have resulted from deep intronic variant c.5999-277G>A of intron 18. CONCLUSIONS: Our study suggests that deep intronic variant of c.5999-277G>A may be a hot spot mutation for mild hemophilia patients without mutation in exonic DNA.

Obesity and overweight in patients with hemophilia: Prevalence by age, clinical correlates, and impact on joint bleeding.

BACKGROUND: The prevalence of obesity in patients with hemophilia (PWH) varies among different ethnicities, and its influence on joint bleeding and hemophilic arthropathy has not been studied in Taiwan population. We explored the prevalence and clinical correlates of obesity and the impact of body mass index (BMI) on annual joint bleeding rate (AJBR) and hemophilic arthropathy in PWH in Taiwan. METHODS: We retrospectively collected clinical information on 140 severe/40 moderate PWH from 2006 to 2014. The patients' median age was 31.5 years, ranged from 6 to 73 years. Their BMI, 6 index joints score by Pettersson scoring, AJBR, and other clinical data were analyzed. RESULTS: The prevalence of overweight and obesity by age group was 7.1% in PWH aged ≤10 years, and rapidly increased to 34.5% in PWH aged 11 to 18 years, 46.7% in PWH aged 18 to 29 years, 61.8% in PWH aged 30 to 39 years, 60.6% in PWH aged 40 to 49 years, and 48% in PWH aged ≥50 years, respectively. Two peak rates were 72.7% in PWH aged 35 to 44 years and 66.7% in PWH aged >65 years. Age, HCV infection, knee score, elbow score, and total 6 index joints scores were found to correlate positively with BMI. However, subtype and severity of hemophilia, ankle scores, HBV and HIV infection did not correlate with BMI. Finally, BMI was found to correlate positively with AJBR in both adult and pediatric PWH. CONCLUSION: The prevalence of overweight and obesity in adolescent and adult PWH was higher than those in the general male population in Taiwan, which rapidly increased with age to peak in PWH aged 35 to 44 years and >65 years. High index joint score, with the exception of ankle scores, positively correlated with high BMI. Further, BMI and obesity also had positive correlation with AJBR in PWH. To our knowledge, this is the first study examining these associations in PWH in Taiwan.

von Willebrand disease: a clinical and laboratory study of sixty-five patients.

von Willebrand disease (VWD) is the commonest inherited bleeding disorder, yet it has not been well recognized in Southeast Asia. The aim of this prospective study was to report our experience of VWD diagnosis and to establish the clinical presentations of VWD in Taiwan. From October 2003 to April 2010, 863 patients with suspicion of having an inherited bleeding disorder underwent VWD screening tests. Those with positive tests were selected for further clinical and laboratory evaluation. A nested gender- and age-matched control cohort underwent similar investigation for comparison. VWD was diagnosed by comprehensive laboratory tests including factor VIII clotting activity, von Willebrand factor antigen assay, VWF:ristocetin cofactor activity (VWF:RCo) and platelet function analyzer (PFA)-100 closure times. VWF multimer analysis was performed by western blot for disease subtype identification. Sixty-five (7.5%) patients from 55 unrelated families were discovered to have VWD. Their median age was 27 years with a range of 4 to 69 years. The most common and specific bleeding symptom in male and female patients was bleeding after dental extraction and menorrhagia, respectively, as compared with control subjects. PFA-100 epinephrine closure time was the most sensitive laboratory test for VWD diagnosis with a sensitivity of 85%, followed by VWF:RCo assay (73%). Among 49 patients with VWF multimer analysis, 37(75.5%) were revealed to have type 1 VWD. Our study demonstrates that VWD and its clinical manifestations and subtypes in Taiwan are similar to those in the West and represents the first report of its kind in a Southeast Asian population.