Artificial intelligence-assisted ultrasound imaging in hemophilia: research, development, and evaluation of hemarthrosis and synovitis detection.

Background: Joint bleeding can lead to synovitis and arthropathy in people with hemophilia, reducing quality of life. Although early diagnosis is associated with improved therapeutic outcomes, diagnostic ultrasonography requires specialist experience. Artificial intelligence (AI) algorithms may support ultrasonography diagnoses. Objectives: This study will research, develop, and evaluate the diagnostic precision of an AI algorithm for detecting the presence or absence of hemarthrosis and synovitis in people with hemophilia. Methods: Elbow, knee, and ankle ultrasound images were obtained from people with hemophilia from January 2010 to March 2022. The images were used to train and test the AI models to estimate the presence/absence of hemarthrosis and synovitis. The primary endpoint was the area under the curve for the diagnostic precision to diagnose hemarthrosis and synovitis. Other endpoints were the rate of accuracy, precision, sensitivity, and specificity. Results: Out of 5649 images collected, 3435 were used for analysis. The area under the curve for hemarthrosis detection for the elbow, knee, and ankle joints was ≥0.87 and for synovitis, it was ≥0.90. The accuracy and precision for hemarthrosis detection were ≥0.74 and ≥0.67, respectively, and those for synovitis were ≥0.83 and ≥0.74, respectively. Analysis across people with hemophilia aged 10 to 60 years showed consistent results. Conclusion: AI models have the potential to aid diagnosis and enable earlier therapeutic interventions, helping people with hemophilia achieve healthy and active lives. Although AI models show potential in diagnosis, evidence is unclear on required control for abnormal findings. Long-term observation is crucial for assessing impact on joint health.

A novel factor V compound heterozygous mutation associated with thrombosis (Y1961C; FV-Kanazawa, together with 1982_1983del).

BACKGROUND: Factor (F)V is pivotal in both procoagulant and anticoagulant mechanisms. The present report describes a novel F5 mutation in a FV-deficient patient (FV activity, 6 IU/dL; FV antigen, 32 IU/dL) complicated by recurrent deep vein thrombosis. The patient demonstrated activated protein C resistance (APCR) with compound heterozygous mutations consisting of FV-Y1961C (FVKanazawa) and FV-1982_1983del. OBJECTIVES: To clarify thrombotic mechanisms associated with this FV abnormality. METHODS AND RESULTS: Levels of FV-1982_1983del were below the detection sensitivity in our expression experiments using human embryonic kidney 293T cells, and analyses were targeted, therefore, on the FV-Y1961C mutation. Activated partial thromboplastin time-based clotting assays demonstrated that FV-Y1961C exhibited APCR and that the reduced activated protein C (APC) susceptibility in FVa-Y1961C resulted in a marked depression of APC-catalyzed inactivation with delayed cleavage at Arg506 and little cleavage at Arg306 with or without protein S. The APC cofactor activity of FV-Y1961C in APC-catalyzed FVIIIa inactivation promoted by Arg336 cleavage in FVIII was impaired. The binding affinity of FVa-Y1961C to phospholipid membranes was reduced in reactions involving APC/protein S-catalyzed inactivation and in prothrombinase activity. Furthermore, the addition of FVa-Y1961C to plasma failed to inhibit tissue factor-induced procoagulant function. These characteristics were similar to those of FV-W1920R (FVNara) and FV-A2086D (FVBesançon). CONCLUSION: We identified a compound heterozygous FV-Y1961C mutation in the C1 domain representing a novel FV mutation (FVKanazawa) resulting in not only APCR due to impaired FVa susceptibility and FV cofactor activity for APC function but also impaired inhibition of tissue factor-induced procoagulant function. These defects in anticoagulant function associated with FV in FV-Y1961C contributed to a prothrombotic state.

ROTEM could be useful for lupus anticoagulant hypoprothrombinemia syndrome.

BACKGROUND: Lupus anticoagulant-hypoprothrombinemia syndrome (LAHPS) is a rare disease caused by acquired factor II (FII) deficiency and lupus anticoagulant. Patients with LAHPS typically present with thrombosis and bleeding. However, little information is available on the evaluation of coagulation potential in patients with LAHPS. We examined global coagulation potentials in patients with LAHPS during the clinical course in this study. METHODS: Coagulation potentials in two pediatric patients with LAHPS were assessed by measuring clotting time (CT) and clot formation time using Ca2+-triggered rotational thromboelastometry (ROTEM), CT and maximum coagulation velocity using clot waveform analysis (CWA), and lag time and peak thrombin using the thrombin generation assay (TGA). The day of admission was defined as day 0. RESULTS: In case 1, the bleeding symptoms disappeared by day 5. However, the TGA and CWA results were markedly lower than normal, although FII activity (FII:C) returned to within the normal range by day 14. In contrast, ROTEM revealed a recovery to near-normal levels (day 14). All coagulation parameters (day 80) were within normal ranges. In case 2, coagulation potential was severely depressed until day 12, although FII:C returned to normal levels. Bleeding symptoms disappeared on day 19, and the ROTEM data revealed that the parameters were close to the normal range. The coagulation parameters in all assays were normalized on day 75. CONCLUSIONS: Recovery of coagulation potential in patients with LAHPS was slower than the recovery of FII:C. Moreover, ROTEM appeared to be clinically useful for assessing coagulation potential in patients with LAHPS.

The combination of Asp519Val/Glu665Val and Lys1813Ala mutations in FVIII markedly increases coagulation potential.

ABSTRACT: A2 domain dissociation in activated factor VIII (FVIIIa) results in reduced activity. Previous studies demonstrated that some FVIII mutants (D519V/E665V and K1813A) with delayed A2 dissociation enhanced coagulation potential. We speculated, therefore, that FVIII encompassing a combination of these mutations might further enhance coagulant activity. The aim was to assess the D519V/E665V/K1813A-FVIII mutation as a gain of function. The FVIII mutants, D519V/E665V/K1813A, D519V/E665V, and K1813A were expressed in a baby hamster kidney cell system, and global coagulation potential of these mutants was compared with wild-type (WT) FVIII in vitro and in hemophilia A mice in vivo. Kinetic analyses indicated that the apparent Kd for FIXa on the tenase assembly with D519V/E665V and D519V/E665V/K1813A mutants were lower, and that the generated FXa for D519V/E665V/K1813A was significantly greater than WT-FVIII. WT-FVIII activity after thrombin activation increased by ∼12-fold within 5 minutes, and returned to initial levels within 30 minutes. In contrast, The FVIII-related activity of D519V/E665V/K1813A increased further with time after thrombin activation, and showed an ∼25-fold increase at 2 hours. The A2 dissociation rate of D519V/E665V/K1813A was ∼50-fold slower than the WT in a 1-stage clotting assay. Thrombin generation assays demonstrated that D519V/E665V/K1813A (0.125 nM) exhibited coagulation potential comparable with that of the WT (1 nM). In animal studies, rotational thromboelastometry and tail-clip assays showed that the coagulation potential of D519V/E665V/K1813A (0.25 µg/kg) was equal to that of the WT (2 µg/kg). FVIII-D519V/E665V/K1813A mutant could provide an approximately eightfold increase in hemostatic function of WT-FVIII because of increased FVIIIa stability and the association between FVIIIa and FIXa.

Peritoneal dialysis-associated infection caused by Mycobacterium abscessus in a pediatric patient on continuous peritoneal dialysis without switching to hemodialysis.

Most peritoneal dialysis (PD)-associated infections caused by Mycobacterium abscessus (M. abscessus) require a transfer from PD to hemodialysis (HD). Here, we report a pediatric case of exit-site and tunnel infections caused by M. abscessus, for whom PD was continued with catheter replacement, debridement of the infected site, and the administration of multiple antibacterial agents. A 10-year-old boy with end-stage kidney disease secondary to juvenile nephronophthisis with NPHP1 deletion, for whom PD was initiated at the age of 9 years, was admitted to the hospital with complaints of fever, pus at the exit-site of the PD catheter, and poor PD drainage. The dialysis effluent culture results were negative; however, M. abscessus was detected in the pus at the exit-site of the PD catheter. The management of HD was expected to be challenging owing to the presence of developmental disorders. Therefore, PD was continued with the simultaneous removal of the PD catheter, reinsertion of a new catheter at a new site, and debridement of the infected site. Multiple antibacterial therapies were administered for 2 months, and the patient was eventually discharged without switching to HD. To the best of our knowledge, this is the first pediatric case of a PD-associated infection caused by M. abscessus, for whom PD was continued without switching to HD. This treatment strategy is not generally recommended but may be an option for patients without peritonitis who have difficulty switching to HD.

Additional Factor X Enhances Emicizumab-Driven Coagulation Function in Patients with Hemophilia A and Hemophilia A Mice.

BACKGROUND: Bypassing agents are used for breakthrough bleedings in patients with hemophilia A with inhibitor (PwHAwI) receiving emicizumab prophylaxis. Previous study demonstrated a weak binding affinity between emicizumab and factor (F)X (K d; 1.85 µM), and that this value was much greater than the plasma FX concentration (∼130 nM). We speculated that increased FX levels could enhance coagulation potential in emicizumab-treated patients with hemophilia A (PwHA). To investigate the relationship between FX concentrations and emicizumab-driven coagulation. METHODS: Plasma FX (up to 1,040 nM) and emicizumab (50 µg/mL) were added to FVIII-deficient plasmas, and plasma-derived FX (520 nM) or recombinant (r)FVIIa (2.2 µg/mL) was added to plasmas from three emicizumab-treated PwHAwI. The adjusted maximum coagulation velocity (Ad|min1|) by clot waveform analysis and peak thrombin (PeakTh) by thrombin generation assay in them were evaluated. Emicizumab (3.0 mg/kg), human (h)FIX (100 IU/kg), and various doses of hFX (100-500 IU/kg) were intravenously administered to HA mice. Clotting time/clot formation time (CT/CFT) were assessed using rotational thromboelastometry, and blood loss was estimated by a tail-clip assay. RESULTS: The addition of FX to FVIII-deficient plasma with emicizumab increased Ad|min1| and PeakTh. The coagulation parameters in emicizumab-treated PwHAwI spiked with additional FX remained within the normal range as well as the additional rFVIIa. In animal models, hFX injection shortened the CT and CT + CFT. The shorter CT and CT + CFT, and the lower blood loss were evident after 200 or 500 IU/kg hFX administration, and those indices were comparable to those in wild-type mice. CONCLUSION: Supplementation with FX may improve emicizumab-driven hemostasis in PwHA.

Vitamin K prophylaxis in neonates: comparing two different oral regimens.

OBJECTIVE: This prospective study compared PIVKA-II and PT-INR levels in infants who received two vitamin K (VK) prophylactic regimens. METHODS: A single institution administered 119 healthy newborns 2 mg of VK syrup. Infants were assigned to a 3-time regimen (n = 56) with VK at birth, five days (5D), and 1-month-old (1 M), or a 13-time regimen (n = 63) with VK at birth, 5D, and then weekly for 11 weeks. RESULTS: The 13-time regimen significantly lowered PIVKA-II and reduced PT-INR at 1 M in both breastfed (PIVKA-II: 18-16 mAU/mL, p = 0.02; PT-INR: 1.37-1.13, p < 0.01) and formula-fed infants (PIVKA-II: 18-15 mAU/mL, p = 0.01; PT-INR: 1.54-1.24, p < 0.01), compared to baseline measurements taken at 5D. The 3-time regimen did not significantly alter PIVKA-II levels and only improved PT-INR (2.00-1.50, p < 0.01) in formula-fed infants. CONCLUSION: The 13-time VK regimen significantly enhanced coagulation profiles more effectively than the 3-time regimen.

Reduced plasma factor X is associated with a lack of response to recombinant activated factor VII in patients with hemophilia A and inhibitor, but does not impair emicizumab-driven hemostasis in vitro.

BACKGROUND: The hemostatic effect of recombinant (r) factor (F)VIIa after repetitive intermittent administration may be attenuated in patients with hemophilia A (PwHA) with inhibitors (PwHAwI) creating a clinically unresponsive status, although mechanism(s) remain to be clarified. In patients receiving prophylaxis treatment with emicizumab, concomitant rFVIIa is sometimes utilized in multiple doses for surgical procedures or breakthrough bleeding. AIM AND METHODS: We identified 'unresponsiveness' to rFVIIa, based on global coagulation function monitored using rotational thromboelastometry (ROTEM) in 11 PwHAwI and 5 patients with acquired HA, and investigated possible mechanisms focusing on the association between plasma FX levels and rFVIIa-mediated interactions. RESULTS: Our data demonstrated that FX antigen levels were lower in the rFVIIa-unresponsive group than in the rFVIIa-responsive group (0.46 ± 0.14 IU/mL vs. 0.87 ± 0.15 IU/mL, p < 0.01). This relationship was further examined by thrombin generation assays using a FX-deficient PwHAwI plasma model. The addition of FX with rFVIIa was associated with increased peak thrombin (PeakTh) generation. At low levels of FX (<0.5 IU/mL), rFVIIa failed to increase PeakTh to the normal range, consistent with clinical rFVIIa-unresponsiveness. In the presence of emicizumab (50 µg/mL), PeakTh was increased maximally to 80 % of normal, even at low levels of FX (0.28 IU/mL). CONCLUSIONS: Unresponsiveness to rFVIIa was associated with reduced levels of FX in PwHAwI. Emicizumab exhibited in vitro coagulation potential in the presence of FX at concentrations that appeared to limit the clinical response to rFVIIa therapy.

The effects of emicizumab on in vitro coagulation and fibrinolysis parameters in patients with disseminated intravascular coagulation with and without addition of anti-FVIII antibody.

BACKGROUND: Emicizumab (Emi) is used as haemostatic prophylaxis for patients with haemophilia A (PwHA). Disseminated intravascular coagulation (DIC) is a condition characterized by persistent systemic activation of coagulation, but there is yet no information on coagulation and fibrinolysis potentials in Emi-treated PwHA with DIC. AIM: To examine the effect of Emi on coagulation and fibrinolysis potentials in HA-model DIC plasmas. METHODS: Plasma from a patient with sepsis-DIC (seven patients) was treated with anti-factor (F)VIII monoclonal antibody (HA-model DIC plasma) and incubated with Emi (50 µg/mL). The plasma was then assessed using clot-fibrinolysis waveform analysis (CFWA). Coagulation and fibrinolysis parameters were expressed as ratios relative to normal plasma (|min1|-ratio and |FL-min1|-ratio, respectively). PATIENTS AND RESULTS: In case 1, coagulant potential was slightly high and fibrinolytic potential was extremely low, presenting a coagulant-dominant state (|min1|-ratio/|FL-min1|-ratio: 1.1/.38). In cases 2-5, fibrinolytic potential was not suppressed, but there were marked hypercoagulant potentials, indicating relative coagulant-dominant states. In case 6, coagulant and fibrinolytic potentials were increased but well balanced (|min1|-ratio/|FL-min1|-ratio: 1.38/1.28). In case 7, both potentials were severely deteriorated in not only CFWA but also the thrombin/plasmin generation assay. The addition of Emi into the HA-model DIC plasmas increased |min1|-ratio values in all cases, but the coagulant potentials did not exceed the initial ones (DIC plasma before treatment with anti-FVIII antibody). CONCLUSIONS: The presence of Emi in the HA-model DIC plasma improved coagulation potentials, but did not increase coagulation potentials beyond those of DIC plasma in non-HA states.

Force-sensing treadmill gait analysis system can detect gait abnormalities in haemophilia patients without arthropathy.

BACKGROUND: Joint damage in patients with haemophilia (PwH) is commonly assessed by imaging, but few reports have described how structural changes in joints, for example, haemophilic arthropathy (HA)-affect gait ability. OBJECTIVES: We evaluated gait function among PwH with HA, PwH without HA, and people without haemophilia (non-PwH) using a Zebris FDM-T treadmill (FDM-T), an easy-to-use gait assessment instrument with a force sensor matrix. METHODS: The following gait parameters were collected: centre of pressure trajectory intersection (COPi) anterior/posterior variability, COPi lateral variability, COPi anterior/posterior symmetry, COPi lateral symmetry, single-limb support line (SLSL) length, and SLSL variability. Participants walked at their typical gait speed. The physical function of the PwH was assessed by the Hemophilia Joint Health Score (HJHS). Parameters were compared among the three groups. RESULTS: Twelve PwH with HA, 28 PwH without HA, and 12 non-PwH were enrolled. Gait speed significantly differed between groups (non-PwH, 3.1 ± 0.7; PwH without HA, 2.0 ± 0.7; PwH with HA; 1.5 ± 0.4). The COPi anterior/posterior variability, COPi lateral variability, SLSL length, and SLSL variability were greater in the PwH groups than in the non-PwH group. The COPi lateral symmetry differed between PwH with HA and the other groups. The HJHS was not correlated with gait parameters among PwH with HA. CONCLUSIONS: Gait parameters and speed were abnormal in both PwH with HA and PwH without HA. The FDM-T can be used to identify early stages of physical dysfunction that cannot be detected by conventional functional assessments such as the HJHS.

Real-world long-term safety and effectiveness of turoctocog alfa in the treatment of haemophilia A in Japan: results from a multicentre, non-interventional, post-marketing study.

OBJECTIVES: To assess the safety and effectiveness of turoctocog alfa in previously treated patients (PTPs) and previously untreated patients (PUPs) with haemophilia A in a real-world setting in Japan. METHODS: This multicentre, non-interventional, post-marketing study recruited patients with haemophilia A who initiated treatment with turoctocog alfa from 18 sites (08/2014-12/2018). The primary endpoint was adverse events (AEs) during the 2-year study period. RESULTS: The safety and effectiveness analysis set included 39 patients. In total, 13 (33.3%) patients reported ≥1 AE; incidence rate was 60.4 events/100 patient-years of exposure (PYE). Treatment was withdrawn in two cases: pruritus in a PTP and factor VIII inhibitor development in a PUP. Inhibitor development occurred in 2.6% of all patients, with an incidence rate of 3.8 events/100 PYE. The rate of inhibitor development was 0%, 25% and 20% in PTPs, PUPs and PUPs with severe type, respectively. The haemostatic success rate was 91.4% for 383 bleeding episodes and 85.7% for 14 surgeries. The negative binomial annualised bleeding rate for the prophylaxis regimen was 6.19 episodes/year (95% CI, 3.69-10.38). The mean (SD) total consumption of turoctocog alfa (n = 34; excluding FVIII inhibitors) was 5,382.6 (7,180.1) IU/kg/year/patient; consumption was 4,133.1 (1,452.4) IU/kg/year/patient for prophylaxis. DISCUSSION: The effectiveness and safety profiles were comparable to those observed in other turoctocog alfa trials; effectiveness analysis and consumption were not affected by treatment regimens. CONCLUSION: Long-term use of turoctocog alfa therapy in clinical practice posed no newly identified safety issues and was effective for prophylaxis and treatment of bleeds in patients with haemophilia A in Japan.

Anticoagulant effects of protein C, protein S, and antithrombin levels on the protein C pathway in young children.

The protein C (PC) pathway involves physiological anticoagulant factors (PC, protein S [PS], and factor V) and performs major anticoagulant functions in adults. Variations in overall PC pathway function due to dynamic changes in PC and PS in early childhood are poorly understood. We aimed to evaluate the contributions of PC pathway function during early childhood by measuring changes in plasma thrombin generation (TG) after administration of the PC activator protac. We evaluated correlations between anticoagulant factors and percentage of protac-induced coagulation inhibition (PiCi%). Before protac addition, TG in newborns (n = 35), infants (n = 42), young children (n = 35), and adults (n = 20) were 525 ± 74, 720 ± 96, 785 ± 53, and 802 ± 64 mOD/min, and PiCi% were 42.1 ± 9.9, 69.8 ± 11.0, 82.9 ± 4.4, and 86.9 ± 3.4%, respectively. The distribution of PiCi% on the two axes of TG (with or without protac) changed continuously with age and differed from that of warfarin-treated plasma and adult PC- or PS-deficient plasma. PiCi% increased dynamically during infancy and correlated with PS levels in newborns and PC levels in young children. Addition of PC or fresh frozen plasma equivalent to approximately 25% PC to PC-deficient plasma improved PiCi%. This automatic measurement requires only a small sample volume and is useful for analysis of developmental hemostasis.

Hybrid human-porcine factor VIII proteins partially escape the inhibitory effects of anti-factor VIII inhibitor alloantibodies having A2 or C2 domain specificity.

INTRODUCTION: Porcine factor (pF)VIII has low cross-reactivity with anti-human (h)FVIII inhibitor alloantibodies. Clinical trials of pFVIII in congenital haemophilia A patients with inhibitor (PwHA-I) are in progress. Most polyclonal anti-hFVIII inhibitors recognize its A2 and/or C2 domain(s), and recombinant human-porcine hybrid (hp)FVIII proteins may escape neutralization by these inhibitors. AIM: To evaluate the ability of hpFVIII to limit the anti-FVIII activity of inhibitor alloantibodies. METHODS: Three hybrid proteins were created by substituting the hFVIII A2, C2 domain or both with the corresponding domains of pFVIII [termed hp(A2), hp(C2) and hp(A2/C2), respectively]. The reactivity of these hybrids was assessed by one-stage clotting assays (OSA), thrombin generation assays (TGA) and rotational thromboelastometry (ROTEM) by adding them to FVIII-deficient samples. RESULTS: OSA demonstrated that the hybrid proteins avoided neutralization by anti-FVIII A2 or C2 monoclonal antibodies (mAb) and polyclonal inhibitor-antibodies (polyAb) from PwHA-I. In TGA, thrombin generation with hp(A2) and hp(A2/C2) was not attenuated in the presence of patient IgG recognizing anti-A2 domain. In contrast, that with hFVIII and hp(C2) was suppressed by this IgG to levels equivalent to those of FVIII-deficient plasma. With anti-A2/C2 polyAb, the activity of hp(A2/C2) was unaffected. ROTEM demonstrated that the addition of hp(A2) or hp(A2/C2) to anti-A2 polyAb shortened clot times/clot formation times, whilst hFVIII or hp(C2) were ineffective. Similarly with anti-A2/C2 polyAb, hp(A2/C2) restored coagulation potential to a greater extent than hp(A2) and hp(C2). CONCLUSION: Hybrid FVIII proteins containing porcine FVIII A2 and/or C2 domain(s) could support effective therapy in PwHA-I by avoiding neutralization.

Association of physical activity with bleeding events and safety in patients with haemophilia A starting emicizumab prophylaxis: an interim analysis of the TSUBASA study.

INTRODUCTION: Little information exists on the relationship between bleeding outcomes and physical activity in patients with haemophilia A (PwHA). AIM: This interim analysis of the TSUBASA study (UMIN-CTR ID: UMIN000037448) evaluated the association of physical activity with bleeding and safety in PwHA starting emicizumab. METHODS: PwHA without factor VIII inhibitors were recruited. Physical activity and bleed data were obtained using an electronic patient-reported outcome application and wearable activity tracker. Adverse events (AEs) were documented. RESULTS: At data cut-off (31-May-2021), 107 PwHA were enrolled, with a median (range) age of 35 (0-73) years. Physical activity data were obtained for 74 participants. Of these, 47 (63.5%) recorded a total of 396 exercise events. The most common exercise events were walking (32.4%), cycling (14.9%), and football (5.4%). Two (0.5%) exercise events in the same individual were associated with bleeding (running, weight training). The safety analysis population consisted of 106 participants treated with emicizumab (median observation period: 241.5 days). Twenty-one (19.8%) participants experienced a total of 39 AEs. Five (4.7%) experienced a serious AE, none of which was emicizumab-related, and three (2.8%) experienced an adverse drug reaction. CONCLUSIONS: PwHA receiving emicizumab in the TSUBASA study experienced minimal bleeding associated with physical activity. TRIAL REGISTRATION: Trial registration: UMIN-CTR ID: UMIN000037448.

NXT007-mediated hemostatic potential is suppressed by activated protein C-catalyzed inactivation of activated factor V.

Background: Activated protein C (APC) inactivates activated factor (F) V (FVa) and FVIIIa. NXT007, an emicizumab-based engineered therapeutic bispecific antibody, enhances the coagulation potential of FVIII-deficient plasma (FVIIIdef-plasma) to near normal levels. However, little is known about the effect of APC-induced inactivation in NXT007-mediated hemostatic function. Objectives: To investigate the contribution of APC-mediated reactions to NXT007-driven hemostasis. Methods: In pooled normal plasma (PNP) or FVIIIdef-plasma spiked with NXT007 (10 µg/mL), effects of APC (0-16 nM) were measured using a thrombin generation assay (TGA). The direct effects of APC on cofactor activity of NXT007 or FVIIIa in a FXa generation assay were also measured. The FVdef-plasma and FV Leiden plasma (FVLeiden plasma) were preincubated with 2 anti-FVIII monoclonal antibodies (termed FVIII-depleted), and the APC effect in the presence of NXT007 in FVIII-depleted FVdef-plasma with the addition of exogenous FV (7.5-30 nM) or FVIII-depleted FVLeiden plasma was investigated. Results: The APC dose-dependent suppression effect in TGA of FVIIIdef-plasma spiked with NXT007 was similar to that of PNP. FXa generation with NXT007 was not impaired by the addition of APC, suggesting that the APC-induced reaction in TGA with NXT007 was attributed to the direct inactivation of FVa. The addition of APC to FVIII-depleted FVdef-plasma, along with NXT007 and various FV concentrations, showed a similar attenuation to PNP. The NXT007-driven thrombin generation in FVIII-depleted FVLeiden plasma was suppressed by APC, similar to the reaction in native FVLeiden plasma. Conclusion: NXT007 did not impair APC-mediated downregulation of FVa in FVIIIdef-plasmas, regardless of the presence of FV mutation with APC resistance.

Emicizumab-mediated hemostatic function assessed by thrombin generation assay in an in vitro model of factor VIII-depleted thrombophilia plasma.

Patients with hemophilia A (PwHA) may have concurrent deficiency of representative anticoagulant proteins, protein (P)C, PS, and antithrombin (AT), which reduces bleeding frequency. However, emicizumab-driven hemostasis in PwHA with such thrombophilic potential remains unclarified. This study investigated the influence of natural anticoagulants on emicizumab-driven coagulation in HA model plasma. Various concentrations of PS and AT were added to PS-deficient plasma and AT-deficient plasma in the presence of anti-FVIII antibody (FVIIIAb; 10BU/mL). PC-deficient plasma was mixed with normal plasma at various concentrations in the presence of FVIIIAb. Emicizumab (50 µg/mL) was added to these thrombophilic HA model plasmas, prior to tissue factor/ellagic acid-triggered thrombin generation assays. Co-presence of emicizumab increased peak thrombin values (PeakTh) dependent on PS, AT, and PC concentrations. Maximum coagulation potentials in the PS-reduced HA model plasmas remained normal in the presence of emicizumab. PeakTh were close to normal in the presence of 50%AT irrespective of emicizumab, but were higher than normal in the presence of 25%AT. Addition of recombinant FVIIa (corresponding to an administered dose of 90 µg/kg) enhanced coagulation potential to normal levels. Our findings provide novel information on hemostatic regulation in emicizumab-treated PwHA with a possible thrombophilic disposition.

The clinical and genetic landscape of early-onset thrombophilia in Japan.

OBJECTIVES: To determine the optimal management for early-onset thrombophilia (EOT), the genetic and clinical features of protein C (PC)-, protein S (PS)-, or antithrombin (AT)-deficient patients of ≤20 years of age were studied in Japan. METHODS/RESULTS: Clinical and genetic information of all genetically diagnosed cases was collected through the prospective, retrospective study, and literature review. One-hundred-one patients had PC (n = 55), PS (n = 29), or AT deficiency (n = 18). One overlapping case had PC- and PS-monoallelic variant. Fifty-five PC-deficient patients (54%) had 26 monoallelic or 29 biallelic variant(s), and 29 (29%) PS-deficient patients had 20 monoallelic or nine biallelic variant(s). None of the patients had AT-biallelic variants. The frequent low-risk allele p.K193del (PC-Tottori) was found in five patients with monoallelic (19%) but not 29 with biallelic variant(s). The most common low-risk allele p.K196E (PS-Tokushima) was found in five with monoallelic (25%) and six with biallelic variant(s) (67%). One exceptional de novo PC variant was found in 32 families with EOT. Only five parents had a history of thromboembolism. Thrombosis concurrently developed in three mother-newborn pairs (two PC deficiency and one AT deficiency). The prospective cohort revealed the outcomes of 35 patients: three deaths with PC deficiency and 20 complication-free survivors. Neurological complications were more frequently found in patients with PC-biallelic variants than those with PC-, PS-, or AT-monoallelic variants (73% vs. 24%, p = .019). CONCLUSIONS: We demonstrate the need for elective screening for EOT targeting PC deficiency in Japan. Early prenatal diagnosis of PC deficiency in mother-infant pairs may prevent perinatal thrombosis in them.