Multicentre pharmacokinetic evaluation of rFVIII-Fc (efmoroctocog alfa) in a real life and comparison with non-extended half-life FVIII concentrates.

The use of enhanced half-life (EHL) FVIII has improved the quality of prophylaxis in haemophilia A, but with a benefit that may vary from one patient to another. We analysed the pharmacokinetic data obtained with efmoroctocog alfa (rFVIII-Fc) in 114 patients and, in 47 cases, compared them to those previously measured with non-EHL FVIII. The in vivo recovery (IVR) of rFVIII-Fc measured with one stage clotting assay (OSA) and chromogenic assay (CSA) was 2.2 and 2.8 IU/mL per IU/kg, respectively. The median half-life (T1/2 ) of rFVIII-Fc was 14.5 hours whatever the FVIII:C assay used, but variable and correlated with preinfusion VWF:Ag levels (r = .76). Both IVR and T1/2 were lower in patients under 12 years old (2.4 IU/mL per IU/kg and 11.1 hours, respectively; CSA). PK study of rFVIII-Fc vs non-EHL FVIII showed a T1/2 ratio of 1.4 in favour of rFVIII-Fc, regardless of the patient's age. However the relative increase in T1/2 with rFVIII-Fc was lower than 30% in one-third of patients evaluated, particularly when the previous FVIII administered was a BHK-derived product. This study therefore suggests that analysis of individual PK profile in response to a specific FVIII concentrate is potentially useful before a switch in haemophilia A patients.

Incidence of obstetrical thrombotic thrombocytopenic purpura in a retrospective study within thrombocytopenic pregnant women. A difficult diagnosis and a treatable disease.

BACKGROUND: Thrombotic thrombocytopenic Purpura (TTP) defined as ADAMTS-13 (A Disintegrin And Metalloprotease with ThromboSpondin type 1 domain 13) activity <10 % is a rare aetiology of thrombocytopenia during pregnancy, although the precise incidence is unknown. During pregnancy, the diagnosis of TTP is crucial as it has high feto-maternal morbidity-mortality and requires urgent plasma exchange. The purpose of this study was to assess the incidence of TTP retrospectively and to describe case presentations and follow-up. METHODS: A monocentric retrospective study (2008-2009) was conducted among pregnant women followed in a tertiary care obstetrical unit who experienced at least one episode of severe thrombocytopenia (platelets ≤75 G/L) during 2008 and 2009. In cases of uncertain aetiology of thrombocytopenia, ADAMTS-13 activity was assessed by the full length technique. RESULTS: Among 8,908 deliveries over the 2 year period, 79 women had a platelet count nadir ≤75 G/L. Eighteen had a known aetiology of thrombocytopenia and 11 were lost to follow-up. Among 50 remaining patients, ADAMTS-13 activity was undetectable (<5 %) in 4, consistent with the diagnosis of TTP. Platelet count spontaneously normalized in 3 patients after delivery. None presented focal cerebral involvement. Three of the four, who were primipara patients, had a sustained severe deficiency in the absence of anti-ADAMTS-13 antibodies, and ADAMTS-13 gene sequencing indicated a constitutive deficiency. The fourth, a multipara patient, had an acquired, auto-immune TTP. Placental pathology in the three primipara patients showed severe and non-specific ischemic lesions. Two patients lost their babies shortly after birth. In subsequent pregnancies in these two patients, prophylactic plasma infusion initiated early with increasing volume throughout pregnancy prevented TTP relapse, improved placental pathology, and led to normal delivery. CONCLUSIONS: The prevalence of TTP among thrombocytopenic pregnant women is high, up to 5 % in a tertiary unit. Platelet count normalization after delivery does not eliminate TTP. Clinicians should be aware of TTP during pregnancy, and, even if assessed retrospectively, ADAMTS-13 assessment is of particular importance for identifying patients with congenital TTP. In these patients, preventive plasma infusion and/or exchange can dramatically improve foetal prognosis, resulting in successful childbirth.

HemosIL VWF:GPIbR Assay Has a Greater Sensitivity than VWF:RCo Technique to Detect Acquired von Willebrand Syndrome in Myeloproliferative Neoplasms.

BACKGROUND: Acquired von Willebrand syndrome (AVWS) is frequent in patients with myeloproliferative neoplasms (MPNs). For von Willebrand factor (VWF) functional evaluation, ristocetin cofactor activity by aggregometry (VWF:RCo) is considered the gold standard but has limitations, and automated activity measurement has been developed such as the HemosIL VWF:RCo Werfen with particle agglutination (VWF:GPIbR). OBJECTIVES: To evaluate the performance of VWF:GPIbR with HemosIL VWF:RCo Werfen (VWF:GPIbR) versus VWF:RCo in patients with thrombocytosis in the context of MPNs (T-MPNs) and in patients with secondary thrombocytosis (ST). METHODS: MPN patients with thrombocytosis >450 G/L (T-MPNs) were compared with patients with ST due to inflammation or iron deficiency. VWF activity (VWF:Act) was analyzed using VWF:RCo or VWF:GPIbR. VWF analysis was completed by analysis of VWF multimers and VWF collagen binding (CB) assay (VWF:CB). RESULTS: A total of 33 T-MPNs and 18 ST patients were included. Compared with aggregometry, evaluation of VWF:Act by VWF:GPIbR led to lower values in T-MPN patients, but also in ST patients. Interestingly, although the VWF:RCo/VWF:Ag ratio did not reveal differences between T-MPNs and ST patients, the VWF:GPIbR/VWF:Ag ratio analysis allowed us to suspect AVWS only in T-MPN patients. Using the distribution of VWF multimer analysis and VWF:CB, we here demonstrated that VWF:GPIbR allows AVWS diagnosis in nine T-MPNs as opposed to aggregometry. CONCLUSION: Evaluation of VWF:Act using VWF:GPIbR has a greater sensitivity compared with aggregometry to detect AVWS in T-MPN patients.

Urine Protein/Creatinine Ratio in Thrombotic Microangiopathies: A Simple Test to Facilitate Thrombotic Thrombocytopenic Purpura and Hemolytic and Uremic Syndrome Diagnosis.

BACKGROUND: Early diagnosis of thrombotic thrombocytopenic purpura (TTP) versus hemolytic and uremic syndrome (HUS) is critical for the prompt initiation of specific therapies. OBJECTIVE: To evaluate the diagnostic performance of the proteinuria/creatininuria ratio (PU/CU) for TTP versus HUS. PATIENTS/METHODS: In a retrospective study, in association with the "French Score" (FS) (platelets < 30 G/L and serum creatinine level < 200 µmol/L), we assessed PU/CU for the diagnosis of TTP in patients above the age of 15 with thrombotic microangiopathy (TMA). Patients with a history of kidney disease or with on-going cancer, allograft or pregnancy were excluded from the analysis. RESULTS: Between February 2011 and April 2019, we identified 124 TMA. Fifty-six TMA patients for whom PU/CU were available, including 35 TTP and 21 HUS cases, were considered. Using receiver-operating characteristic curves (ROC), those with a threshold of 1.5 g/g for the PU/CU had a 77% sensitivity (95% CI (63, 94)) and a 90% specificity (95% CI (71, 100)) for TTP diagnosis compared with those having an 80% sensitivity (95% CI (66, 92)) and a 90% specificity (95% CI (76, 100) with a FS of 2. In comparison, a composite score, defined as a FS of 2 or a PU/CU ≤ 1.5 g/g, improved sensitivity to 99.6% (95% CI (93, 100)) for TTP diagnosis and enabled us to reclassify seven false-negative TTP patients. CONCLUSIONS: The addition of urinary PU/CU upon admission of patients with TMA is a fast and readily available test that can aid in the differential diagnosis of TTP versus HUS alongside traditional scoring.

Severe transient ADAMTS13 deficiency in pneumococcal-associated hemolytic uremic syndrome.

Thrombotic microangiopathies comprise different entities, including hemolytic uremic syndrome (HUS), thrombotic thrombocytopenic purpura (TTP), and several other conditions. TTP is characterized by hemolytic anemia, thrombocytopenia, and multiorgan failure. TTP is the result of severe von Willebrand factor multimer cleaving protease (ADAMTS13) deficiency that is either inherited or the result of acquired autoantibodies. We report a critically ill 2-year-old girl with invasive pneumococcal disease associated HUS (p-HUS) whose condition was complicated by severe ADAMTS13 deficiency, without detectable inhibitor, in a context of multiple organ failure. The patient recovered with supportive treatment, and ADAMTS13 activity normalized without plasmatherapy. Severe ADAMTS13 deficiency appears to be a manifestation of transient endothelial cell injury in the context of severe sepsis, including invasive p-HUS. The choice of appropriate therapy should not be based on this finding.

Successful treatment with rituximab for acute refractory thrombotic thrombocytopenic purpura related to acquired ADAMTS13 deficiency: a pediatric report and literature review.

OBJECTIVE: To report the case of a child with severe autoimmune thrombotic thrombocytopenic purpura (TTP) resistant to plasma exchange and steroids who was successfully treated with rituximab. DESIGN: Case report and review of the literature on pediatric acquired TTP. The report was approved by an independent local ethics committee. SETTING: Pediatric intensive care unit in a tertiary care children's hospital. PATIENT: A 10-yr-old boy was referred to the emergency unit with fever, vomiting, confusion, hemolytic anemia, thrombocytopenia, and mild acute renal failure. An atypical hemolytic uremic syndrome was suspected, and plasma exchange was started urgently. The patient was refractory to plasma therapy and presented critical complications. After a diagnosis of acquired TTP attributable to anti-ADAMTS13 autoantibodies had been made, he was treated with rituximab, which resulted in a stable clinical remission. INTERVENTIONS: Rituximab therapy. MEASUREMENTS AND MAIN RESULTS: Clinical remission. CONCLUSIONS: TTP is a rare but life-threatening condition in children that is characterized by hemolytic anemia, thrombocytopenia, and signs of ischemic organ dysfunction. If renal involvement is present, TTP may be misdiagnosed as hemolytic uremic syndrome, but reliable screening for ADAMTS13 activity and anti-ADAMTS autoantibodies allow us to distinguish the two entities and provide adequate therapy.

Real Life Population Pharmacokinetics Modelling of Eight Factors VIII in Patients with Severe Haemophilia A: Is It Always Relevant to Switch to an Extended Half-Life?

We retrospectively analysed the data files of 171 adults and 87 children/adolescents with severe haemophilia, except for 14 patients (moderate; minor) (1), to develop a global population pharmacokinetic (PK) model for eight factors VIII (FVIII) that could estimate individual PK parameters for targeting the desired level of FVIII activity (FVIII:C); and (2) to compare half-life (HL) in patients switching from a standard half-life (SHL) to an extended half-life (EHL) and evaluate the relevance of the switch. One-stage clotting assay for the measurement of FVIII activity (FVIII:C, IU/mL) was used for population PK modelling. The software, Monolix version 2019R1, was used for non-linear mixed-effects modelling. A linear two-compartment model best described FVIII:C. The estimated PK parameters (between-subject variability) were: 2640 mL (23.2%) for volume of central compartment (V1), 339 mL (46.8%) for volume of peripheral compartment (V2), 135 mL/h for Q (fixed random effect), and 204 mL/h (34.9%) for clearance (Cl). Weight, age, and categorical covariate EHL were found to influence Cl and only weight for V1. This model can be used for all of the FVIII cited in the study. Moreover, we demonstrated, in accordance with previous studies, that Elocta had longer half-life (EHL) than SHL (mean ratio: 1.48) as compared to Advate, Factane, Kogenate, Novoeight, and Refacto.