754 Original article
Evaluating and monitoring the efficacy of recombinant activated factor VIIa in patients with haemophilia and inhibitors Xue Qi, Yongqiang Zhao, Kuixing Li, Liankai Fan and Baolai Hua Although the use of bypassing agents has dramatically improved the management of haemophilia in patients with inhibitors, questions remain regarding optimal dosing regimens and methodology for monitoring their clinical effectiveness. In this study, we evaluated the efficacy and safety of two different doses of recombinant activated factor VIIa (rFVIIa) in patients with haemophilia and inhibitors and assessed the feasibility of using thromboelastography (TEG) and thrombin generation assays (TGA) for monitoring the response to rFVIIa. Six patients aged 9–49 years with congenital or acquired haemophilia with inhibitors who experienced a total of nine bleeding episodes were included. Seven episodes were treated with conventional rFVIIa dosing (72.7–109.1 mg/kg), and two episodes were treated with a single high-dose regimen (254.6–264.0 mg/ kg). Clinical and haemostatic responses were evaluated. Haemostasis was assessed by prothrombin time (PT), activated partial thromboplastin time (aPTT), factor VII coagulant activity (FVII:C), TEG, and TGA. Six out of seven (85.7%) bleeding episodes responded to conventional rFVIIa dosing, and half (50%) responded to the high-dose regimen. No relationships between PT, aPTT, and FVII:C levels and clinical outcome were observed. However,
Introduction In patients with haemophilia, bleeding episodes are prevented or treated by intravenous replacement of the deficient clotting factor. A major complication of haemophilia treatment is the development of inhibitory antibodies to factors VIII or IX, which occurs in up to 25% of patients receiving replacement therapy [1,2]. Even though immune tolerance therapy can eradicate these inhibitors, this treatment is ineffective in approximately 30% of patients and can be expensive [3]. Bypassing agents, such as recombinant factor VIIa (rFVIIa; NovoSeven, Novo Nordisk, Bagsvaerd, Denmark), are well tolerated and efficacious in managing bleeding episodes in patients with inhibitors [4,5]. However, the optimal dosing regimen of rFVIIa in these patients has been debated. Although haemostatic efficacy was achieved in 92% of pat ients using the recommended dose of 90 mg/kg [6], the efficacy and safety of a single high dose of rFVIIa (270 mg/kg) have also been demonstrated [7]. Currently, there is no accepted method to monitoring the effectiveness of bypassing agents in clinical practice [8–10]. Even though monitoring of the haemostatic 0957-5235 ß 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins
changes in TEG and TGA parameters tended to correspond to clinical response, although large inter-individual variation in rFVIIa efficacy was noted. A good response was seen with rFVIIa in treating acute bleeding episodes in patients with haemophilia and inhibitors. Because changes in TEG and TGA may correlate with clinical outcomes of rFVIIa, TEG and TGA may be useful for monitoring rFVIIa activity in inhibitorpositive haemophilia. Blood Coagul Fibrinolysis 25:754–760 ß 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins. Blood Coagulation and Fibrinolysis 2014, 25:754–760 Keywords: haemophilia, inhibitors, recombinant activated factor VIIa, thrombin generation assay, thromboelastography Department of Hematology, Peking Union Medical College Hospital, Chinese Academy of Medical Science, and Peking Union Medical College, Beijing, China Correspondence to Baolai Hua, Department of Hematology, Peking Union Medical College Hospital, Chinese Academy of Medical Science, and Peking Union Medical College, No. 1 Shuaifuyuan, Dongcheng District, Beijing 100730, China Tel: +86 10 69155020; e-mail: [email protected] Received 24 September 2013 Revised 28 March 2014 Accepted 28 March 2014
effect of these agents may optimize outcomes, prospectively defined, objective criteria for the effectiveness of bypassing agents are lacking. Moreover, clinical studies of their efficacy have relied on subjective assessments by investigators. Haemostasis and its abnormalities traditionally have been assessed by plasma clotting times, such as prothrombin time (PT) and activated partial thromboplastin time (aPTT). However, these standard clotting assays do not reflect total thrombin generation, measure only the initiation of clot formation and not its speed or total extent, and may not be sensitive to hypercoagulation or hypocoagulation [11]. Consequently, these tests may not accurately reflect a patient’s risk of bleeding or bleeding state. Thromboelastography (TEG) and the thrombin generation assay (TGA) have been considered as methods for monitoring the response to bypassing therapy in recent years [12,13]. TEG is a test of overall haemostatic functioning performed on whole blood, and therefore measures both cellular and plasmatic effects on blood coagulation [14]. The TGA, which evaluates peak DOI:10.1097/MBC.0000000000000137
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Monitoring rFVIIa activity in haemophilia Qi et al. 755
thrombin production, the total amount of thrombin produced, and overall time course of thrombin generation [14,15], can be used to measure the overall kinetics of thrombin generation and the efficiency of all of the systems activating and inactivating coagulation [14]. Both methods have been proposed as tools for optimizing the dose and duration of rFVIIa therapy and avoiding its potential complications [12,15]. So far, the overall cases reported of using TEG and TGA to monitor the effectiveness of rFVIIa (both high and low doses) in patients with haemophilia and inhibitors are rather limited. Experiences of using rFVIIa to treat haemophilia patients in both low and high doses from the Asian patients are rare, let alone from Chinese patients. In this study, we evaluated the efficacy and safety of different doses of rFVIIa in Chinese patients with haemophilia with inhibitors and the feasibility of TEG and TGA for monitoring the response to treatment.
Methods Patients and study procedures
The study was approved by the Ethics Review Committee of the Chinese Academy of Medical Sciences and the Peking Union Medical College and conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained by the study subjects or their guardians before the start of the study. Study subjects included six patients aged 9–49 years (admitted during January through May 2010) with inhibitor-positive congenital haemophilia A or B and patients with acquired haemophilia. Patients included in the study had experienced mild or moderate bleeding, such as bleeding in the joint or muscles or haematuria within 24 h, and had not received bypass therapy within 72 h. Patients with major haemorrhage, and patients in whom past therapy with rFVIIa was ineffective, were excluded from the study. Anonymous identification numbers were used to maintain patient confidentiality. rFVIIa was administered in conventional or high-dose regimens. The conventional dose regimen was used in acute bleeding: rFVIIa was given as an intravenous (IV) bolus injection at a conventional dose of 90 mg/kg at baseline (hour 0) and a 90-mg/kg injection 2 h later (hour 2) if deemed necessary based on clinical/laboratory response. The high-dose regimen was administered if a re-bleed occurred. In this regimen, a single high dose of 270 mg/kg was administered. Clinical evaluations included evaluation of pain and bleeding, and were performed before dosing, 30 min and 2 h after dosing, and at the time of hospital discharge. Follow-up visits were also conducted by phone. Treatment response was characterized as good, partial, or poor based on the following criteria. Patients who did not require dose escalation or a switch to a different bypass therapy and who showed an improvement in bleeding-
related symptoms (arthralgia and haematuria) were considered to have a good response. Patients who did not meet one of these criteria but whose bleeding symptoms did not worsen were considered to have a partial response, and patients who did not meet either criteria or whose bleeding symptoms worsened during the initial treatment were considered to have a poor response [16]. Patients were also evaluated for treatment-related adverse events, including allergic reactions, thrombosis, or discomfort. Laboratory evaluations, which included assessments of PT, aPTT, factor VII coagulant activity (FVII:C), TEG, and TGA, were conducted before and 0.5 and 2 h after the first dose of rFVIIa administration for each bleeding episode. Blood sampling and laboratory assays
Peripheral venous blood samples were collected through a 21-gauge needle into Vacutainer tubes containing sodium citrate 0.11 ml/l (BD, Franklin Lakes, New Jersey, USA). After samples were stored for 15 min at room temperature, 1 ml of each sample was used in the TEG test and the rest was used to prepare platelet-poor plasma within 4 h of blood sampling. Platelet-poor plasma was obtained at room temperature by centrifugation at 3000 rpm for 15 min and stored at 808C for further analyses of PT, aPTT, FVII:C, and TGA. PT, aPTT, FVII:C, FVIII:C, and FIX:C were determined by one-stage assay. Inhibitors of FVIII and FIX (FVIII:I and FIX:I) were determined using the Bethesda method. Stago automated coagulation analyzer and its supporting reagents (Stago, Paris, France) were used for all these analyses. TEG (Haemoscope Corporation, Niles, Illinois, USA) was performed using the method described by Luddington and Reikvam et al. [17,18]. The numerical parameters assessed using TEG included the reaction time (R time), the kinetics time (K time), Alpha (the angle of tangent at 20 mm), representing the slope between R time and K time, and the maximum amplitude [19]. The R time is defined as the time from addition of calcium to the start of clot formation and denotes the latency time between placing blood in the sample cup until the clot starts to form (2-mm amplitude). The K time, or the clot formation time, is defined as the time from the start of clot formation to a clot firmness of 20 mm. Finally, the maximum amplitude evaluates the maximum clot firmness reached during analysis and assesses the clot’s rigidity/strength (fibrin and platelet binding). The following reference values were adopted: R time, 2–8 min; K time, 1–3 min; Alpha, 55–788; maximum amplitude, 51–69 mm. The calibrated automated TGA was conducted using the Thrombinoscope (Thrombinoscope BV, Maastricht, The Netherlands) according to the manufacturers’ instructions for thrombin generation. Fluorescence was
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756 Blood Coagulation and Fibrinolysis 2014, Vol 25 No 7
evaluated using an Ascent Reader (Thermo Electron and Fisher Scientific Company, Waltham, Massachusetts, USA), and thrombin generation curves were assessed using Thrombinoscope software. Four major thrombin generation parameters were studied using this technology: the lag time (min, the time to thrombin burst), the time to peak thrombin concentration (min), the peak thrombin height (nmol/l), and the endogenous thrombin potential (ETP, area under the curve in nmol/l per min) [20]. The following reference values were used: lag time 1.9 0.29 min; time to peak 4.1 0.4 min; peak height 446.2 52.8 nmol/l; ETP 1908 228.4 nmol/l per min [6,20,21]. The TGA was analyzed in the transfusion lab of Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China. Statistical analysis
Descriptive statistics were used to analyze PT, aPTT, FVII:C, the TEG parameters (R time, K time, Alpha angle, and maximum amplitude) and the TGA parameters (lag time, peak height, time to peak, and ETP) before and after rFVIIa administration. Data are reported by their median and range if not otherwise stated.
Results Six patients with haemophilia A or B with inhibitors or acquired haemophilia A were enrolled in the study, received rFVIIa therapy, and underwent haemostatic monitoring. Information on the demographics, baseline characteristics, and type of acute bleeding of the patients in the study is shown in Table 1. Nine acute bleeding episodes were reported. Seven bleeding episodes were treated with the conventional rFVIIa dose regimen (72.73–109.09 mg/kg) and two bleeding episodes were treated with the high-dose regimen (254.55–264.00 mg/kg). As shown in Table 1, the total efficacy of rFVIIa was 77.8% (7/9), and a good or partial response was observed in 85.7% (6/7) of patients receiving the conventional dose and 50% (1/2) receiving the high dose (Table 1). Three re-bleeds occurred in two patients (two in patient 3 and one in patient 4). Because patient 3 initially responded well to a conventional dose, Table 1
another conventional dose was given after the first rebleed, which successfully stopped the bleeding. However, a high dose was used to treat this patient’s second re-bleed. Tables 2 and 3 illustrate the impact of rFVIIa on PT, aPTT, and FVII:C. At baseline, all the patients showed normal values for PT and FVII:C and longer-than-normal values for aPTT. For both conventional dosing and high dosing, administration of rFVIIa shortened PT and aPTT and increased FVII:C levels. A numerically higher FVII:C level was observed following use of the high dose (Table 3) versus use of the conventional dose (Table 2). There was no association between changes in these parameters and response to treatment. As shown in Fig. 1, TEG parameters were undetectable and demonstrated nearly flat curves prior to the initiation of rFVIIa, even after 1 h of analysis. However, after rFVIIa was administered, TEG profiles improved, indicating that the use of rFVIIa accelerates clotting. Marked decreases in R and K times were observed, and a trend towards increased Alpha angle values was seen. Greater changes were seen with the higher-dose regimen than with the conventional dose regimen (Tables 2 and 3). There was significant variation among subjects and only one patient exhibited a concentration–response effect. Ex-vivo results showed an important increase in parameters following an injection of rFVIIa and the degree of improvement varied among the three clinical outcome groups studied (Table 2). Both the R time and K time were shorter in the ‘good response’ group compared with those in the ‘poor response’ group when evaluated both 30 min and 2 h after rFVIIa administration. Similarly, the Alpha angle increased more in the ‘good response’ group compared with those in the ‘poor response’ group. In contrast, there was no direct effect on the maximum amplitude, which is primarily determined by platelet count and fibrinogen concentration. TGA analyses yielded similar results (Table 2). Thrombin generation curves showed an important increase in thrombin generation capacity following injection of rFVIIa. Both 30 min and 2 h after the administration of
Demographics, baseline characteristics, and treatment response by patients in acute bleeding episodes
Patient no.
Sex/age (y)
Type of haemophilia
FVIII:C (IU/dl)
Inhibitor (BU/ml1)
1 2 3a
M/9 M/49 M/10
Haemophilia A Haemophilia A Haemophilia A
1 1 1
20 160 1.5
4b,c
M/20
Haemophilia A
1
1.2
5 6c
M/15 F/37
Haemophilia B AHA
1 1
1.3 80
Bleeding type Haematuria Joint bleeds Joint bleeds Joint bleeds Joint bleeds Haematuria Haematuria Joint bleeds Haematuria
rFVIIa dose (mg/kg)
Total doses for each bleeding
104.35 85.71 109.09 72.73 254.55 96.00 264.00 100.00 92.31
1 1 1 1 1 2 1 1 2
Dose
Treatment response
Conventional Conventional Conventional Conventional High Conventional High Conventional Conventional
Good Good Good Good Good Poor Poor Partial Good
AHA, acquired haemophilia, rFVIIa, recombinant activated factor VIIa; M, male. a Patient 3 experienced three acute bleeding episodes. Two episodes were treated with conventional dose and the third bleeding was treated with high dose. b Patient 4 experienced two acute bleeding episodes. One was treated with conventional dose and another was treated with high dose. c For the first bleeding episode of patient 4 and patient 6, a second dose was given 2 h after the first injection of rFVIIa.
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12.3 (12.1–13.0) 112.4 (103.1–117.1) 138 (108–147) NA NA NA NA 3.25 (3.00–3.67) 11.43 (9.00–13.10) 50.24 (33.39–62.61) 802.5 (475.5–1009.5)
12.0 104.8 125 NA NA NA NA 4.92 10.43 42.29 665.5
Partial 11.8 109.6 147 NA NA NA NA 4.83 17.33 30.71 491.0
Poor 7.6 66.9 2588 25.2 5.7 41.6 74.5 2.00 7.33 86.70 910.0
(7.5–8.5) (63.4–79.7) (1502–2730) (21.2–40.0) (4.3–8.0) (28.5–44.1) (67.0–80.9) (1.67–2.25) (6.67–8.17) (39.89–106.83) (509.0–1330.0)
Good, median (range) 7.7 54.7 2882 46.4 11.7 21.2 67.4 1.92 7.26 84.12 1042.5
Partial
0.5 h after
7.2 68.5 2882 74.2 27.8 8.2 48.3 2.17 11.67 38.84 604.5
Poor 8.0 76.5 1434 23.6 4.7 43.1 69.8 2.00 7.00 84.21 911.5
(7.8–8.6) (67.0–79.5) (1078–2730) (20.0–26.7) (3.2–8.0) (31.2–55.5) (65.9–78.7) (1.67–2.09) (6.67–8.26) (51.03–96.63) (572.0–1224.5)
Good, median (range)
8.1 60.9 1859 59.6 15.5 17.6 67.2 2.00 8.67 71.05 901.0
Partial
2.0 h after
7.6 79.8 1537 64.5 27.5 8.8 48.1 2.17 11.83 34.53 536.5
Poor
12.1 12.2 7.3 7.3 7.5 7.6
PT (s) 108.1 102.4 51.3 57.2 60.0 69.0
aPTT (s) 147 119 4868 5525 2962 3130
FVII:C (%) NA NA 9.7 66.8 15.5 44.8
R (min) NA NA 2.1 20.8 2.7 10.8
K (min)
TEG
NA NA 62.1 12.8 56.6 21.9
Alpha
NA NA 71.5 57.9 72.2 67.1
Maximum amplitude (mm)
3.59 3.50 2.25 2.17 1.92 2.17
Lag time (min)
9.26 15.00 7.76 11.00 7.76 11.83
ttPeak (min)
138.17 45.03 115.14 30.15 118.46 24.59
Peak (nmol/l)
TGA
1622 732.5 1325.5 499.5 1393.0 404.0
ETP (nmol/l/min)
aPTT, activated partial thromboplastin time; ETP, endogenous thrombin potential; FVII:C, factor VII coagulant activity; K, kinetics time; PT, prothrombin time; R, reaction time; rFVIIa, recombinant activated factor VIIa; TEG, thromboelastography.
2 h after
0.5 h after
3 4 3 4 3 4
Patient no.
PT, aPTT, and FVII:C
Haemostatic parameters before dose and at 0.5 and 2.0 h following the administration of high dose of rFVIIa in patients 3 and 4
Before dose
Table 3
aPTT, activated partial thromboplastin time; ETP, endogenous thrombin potential; FVII:C, factor VII coagulant activity; K, kinetics time; PT, prothrombin time; R, reaction time; rFVIIa, recombinant activated factor VIIa; TEG, thromboelastography; ttPeak, time to peak.
TGA
TEG
PT (s) aPTT (s) FVII:C (%) R time (min) K time (min) Alpha Maximum amplitude (mm) Lag time (min) ttPeak (min) Peak (nmol/l) ETP (nmol/l/min)
Good, median (range)
Before dose
Haemostatic parameters before dose and at 0.5 and 2.0 h following the administration of conventional dose of rFVIIa in groups defined by clinical response
PT, aPTT, and FVII:C
Table 2
Monitoring rFVIIa activity in haemophilia Qi et al. 757
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758 Blood Coagulation and Fibrinolysis 2014, Vol 25 No 7
Fig. 2
(a)
10 millimeters
Before 0.5 h after 2 h after
(a)
Thrombin (nmol/l)
Fig. 1
10 millimeters
120 100 80 60
0.5 h after
40
2 h after
20 0
(b)
Before
0
10
20
30
40
50
60
70
Time (min)
Before 0.5 h after 2 h after (c)
10 millimeters
Thrombin (nmol/l)
(b)
110 90 70
Before
50
0.5 h after
30
2 h after
10 –10
0
10
20
30
40
50
Time (min)
Thromboelastography profiles in patients with inhibitor-positive haemophilia before and after treatment in patients with a good response (a: patient 3), partial response (b: patient 5), and poor response (c: patient 4).
rFVIIa, decreased lag time and time to peak, increased peak thrombin generation, and a marked increase in ETP were observed, but these values still remained below the reference range. As in the TEG analyses, inter-individual variation in these parameters was large. TGA parameters improved in all patients, regardless of the clinical response. However, changes in TGA profiles were different in each response group (Fig. 2). Thirty minutes and 2 h after administration of the first dose, the lag time and time to peak were shorter in the ‘good response’ group compared with those in the ‘poor response’ group. Similarly, peak thrombin and ETP increased more in the ‘good response’ group compared with those in the ‘poor response’ group.
Discussion Results from our study confirmed the efficacy and safety of rFVIIa in improving haemostasis during acute bleeding episodes in patients with congenital or acquired haemophilia and inhibitors. Of the nine acute bleeding episodes included in the analysis, seven were treated
(c) Thrombin (nmol/l)
Before 0.5 h after 2 h after
120 100 80 60
Before
40
0.5 h after 2 h after
20 0 –20
0
10
20
30
40
50
60
70
Time (min) Thrombin generation as assessed by thrombin generation assay in patients with inhibitor-positive haemophilia who exhibited a good (a: patient 3), partial (b: patient 5), or poor (c: patient 4) response to recombinant activated factor VIIa.
with conventional doses (72.7–109.1 mg/kg), and two were treated with high doses (254.6–264.0 mg/kg). A good or partial response was reported in six of seven (85.7%) bleeding episodes following the use of conventional doses and in one of two (50%) bleeding episodes following the use of high doses. The overall therapeutic efficacy rate observed in this study was 77.8% (7/9). These data are consistent with data from other studies that have reported total efficacy rates of 92% with conventional doses [6] and 65% with a single dose of high-dose therapy [7]. Other reports of the efficacy of
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Monitoring rFVIIa activity in haemophilia Qi et al. 759
conventionally dosed rFVIIa have ranged from 70–80%. The previous finding of effectiveness of rFVIIa was reassured in our study. Several factors can affect response rates in studies of rFVIIa therapy in patients with haemophilia with inhibitors. One, the timing of treatment appears to be critical. Some data suggest that earlier administration of rFVIIa is associated with a greater response [22]. More frequent bleeding in the treated joint or presence of a target joint is also related to lower ratings of efficacy [23]. Because response rates have been reported to be greater in patients with episodes of joint bleeding than in those with episodes of bleeding outside the joints, the sites of bleeding may also affect treatment response [24]. In our study, rFVIIa achieved a good or a partial response in all subjects with joint bleeds. Although patients 3 and 4 exhibited the same titers of inhibitors, their responses to treatment were remarkably different. Although both conventional and high dose of rFVIIa provided successful haemostasis following acute bleeding episodes in patient 3, neither conventional nor high dose rFVIIa induced haemostasis in patient 4. In this patient, bleeding stopped after switching to prothrombin complex concentrates (PCCs). The different mechanisms of action between rFVIIa and PCC provide a theoretical foundation for inter-individual variation in the clinical efficacy of these agents. Several patient-specific factors may also contribute to the differences in responses to rFVIIa and other bypassing agents. These include variations in TF, prothrombin, protein C, protein S, antithrombin III, TF pathway inhibitor, and tissue plasminogen activator levels, as well as polymorphisms in FV Leiden and endothelial protein C receptors [25]. Our evaluation of the utility of several strategies for monitoring the haemostatic efficacy of rFVIIa confirmed that rFVIIa decreases PT and aPTT and increases FVII:C, as expected. However, no association between changes in these markers of parameters and the therapeutic efficacy of rFVIIa was observed. Because these tests only detect the initial thrombin generated, not the total thrombin produced, they are not suitable for use in rFVIIa monitoring. This study also demonstrates the superiority of assessments of overall coagulation potential, such as TEG and TGA, to traditional clotting parameters in evaluating haemostasis in patients with haemophilia and inhibitors. Unlike changes in PT, aPTT, or FVII:C levels, changes in TEG and TGA parameters reflect changes in the rate of thrombin generation and thrombin generation capacity and appear to relate to clinical outcome. In this study, treatment with rFVIIa was associated with important changes in TEG parameters, such as a reduction in the time to the start of clot formation, reductions in the time to clot strength of 20 mm, and increased thrombin generation. Substantial changes in TGA parameters were also
noticed, including reductions in the lag in thrombin formation and time to peak thrombin generation, as well as an increase in peak thrombin generation and ETP. These trends have been observed in other studies of the utility of TEG and TGA [16,26]. No consistent correlation between improvements in TEG and TGA parameters and rFVIIa doses was reported, possibly because of a large variation in responses and the small number of patients in the study. Large inter-individual differences in TEG responses have been reported in similar studies, including those involving patients with moderate and severe haemophilia [27]. In one such study, FVIII:C levels required to normalize the whole blood coagulation profile in some patients with severe haemophilia was 10 times higher than those in other patients with severe disease. Our results differ from those reported by Ay et al. [9] in their study of the feasibility of using TGA and TEG for monitoring bypass therapy in seven patients with inhibitors. In this study of seven patients who experienced 17 bleeding episodes, TEG and TGA were used to assess the haemostatic impact of rFVIIa at a dose of 80–115 mg/ kg (used to treat six episodes) or activated PCC (aPCC) at 50–100 IU/kg per dose (used to treat 11 episodes). Assessments were conducted at baseline and at 1 and 24 h after bypass therapy, and when clinical haemostasis was obtained. In this study, no association between clinical response to rFVIIa or aPCC and TEG or TGA parameters was observed, leading the authors to conclude that the clinical effectiveness of bypass therapy cannot be assessed by either technology. However, this study and our study had several key methodological differences. For example, our study only used rFVIIa as bypass agent therapy, used different definitions of clinical response, and a narrower interval between TEG/TGA evaluations, suggesting the need for greater standardization of these assessments [9]. Although total number of cases included in the current study was small because of the difficulty of recruitment, the findings brought fresh insights for Chinese haematologists who have relatively limited experiences of rFVIIa usage in patients with haemophilia with inhibitors. Data obtained from the study were consistent with clinical practice and expectations for Chinese patients. Conclusion
In conclusion, TEG and TGA may represent potential surrogate markers for monitoring the impact of bypassing agents such as rFVIIa. These assays may ultimately facilitate the assessment of a patient’s risk of bleeding and thrombotic complications and help clinicians optimize dosing strategies and provide individually tailored treatment regimens. Even though both assays can be useful, the use of TGA is frequently limited to laboratory analyses in academic settings [9]. Regardless of the test
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760 Blood Coagulation and Fibrinolysis 2014, Vol 25 No 7
used, additional studies relating clinical and laboratory findings are necessary to determine which TEG and TGA parameters best predict response. The utility of TEG and TGA also may be increased by standardizing TEG and TGA reagents, methodology, reporting, and interpretation. Further studies should therefore focus on optimizing TEG and TGA methodology to increase the sensitivity of these important technologies.
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Acknowledgements Nicole Cooper of MedVal Scientific Information Services, LLC, provided medical writing and editorial assistance, funding for which was provided by Novo Nordisk Inc. Conflicts of interest
Source of funding: X.Q., B.H., K.L., L.F., and Y.Z.: The drug used in this trial was provided by Novo Nordisk, China. The authors have no other potential conflicts of interest to report.
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Ay Y, Balkan C, Karapinar DY, Akin M, Bilenoglu B, Kavakli K. Feasibility of using thrombin generation assay (TGA) for monitoring bypassing agent therapy in patients with hemophilia having inhibitors. Clin Appl Thromb Hemost 2012; 19:389–394. Young G, Aledort L. Therapy for haemophilia: recent advances and goals for the future. Expert Opin Emerg Drugs 2005; 10:173–184. van Veen JJ, Gatt A, Makris M. Thrombin generation testing in routine clinical practice: are we there yet? Br J Haematol 2008; 142:889–903. Sorensen B, Ingerslev J. Thromboelastography and recombinant factor VIIa-hemophilia and beyond. Semin Hematol 2004; 41 (1 suppl 1):140– 144. Varadi K, Negrier C, Berntorp E, Astermark J, Bordet JC, Morfini M, et al. Monitoring the bioavailability of FEIBA with a thrombin generation assay. J Thromb Haemost 2003; 1:2374–2380. Varadi K, Turecek PL, Schwarz HP. Thrombin generation assay and other universal tests for monitoring haemophilia therapy. Haemophilia 2004; 10 (Suppl 2):17–21. van Veen JJ, Gatt A, Bowyer AE, Cooper PC, Kitchen S, Makris M. Calibrated automated thrombin generation and modified thromboelastometry in haemophilia A. Thromb Res 2009; 123:895–901. Dehmel H, Werwitzke S, Trummer A, Ganser A, Tiede A. Thrombelastographic monitoring of recombinant factor VIIa in acquired haemophilia. Haemophilia 2008; 14:736–742. Luddington RJ. Thrombelastography/thromboelastometry. Clin Lab Haematol 2005; 27:81–90. Reikvam H, Steien E, Hauge B, Liseth K, Hagen KG, Storkson R, et al. Thrombelastography. Transfus Apheresis Sci 2009; 40:119–123. Young G, Ebbesen LS, Viuff D, Di Paola J, Konkle BA, Negrier C, et al. Evaluation of thromboelastography for monitoring recombinant activated factor VII ex vivo in haemophilia A and B patients with inhibitors: a multicentre trial. Blood Coagul Fibrinolysis 2008; 19:276–282. Hemker HC, Al Dieri R, De Smedt E, Beguin S. Thrombin generation, a function test of the haemostatic-thrombotic system. Thromb Haemost 2006; 96:553–561. Chen HY, Ding QL, Zhang LW, Xu GQ, Dai J, Wang XF, et al. [The application of thrombin generation tests to warfarin anticoagulation monitoring]. Article in Chinese. Zhonghua Xue Ye Xue Za Zhi 2008; 29:168–170. Santagostino E, Gringeri A, Mannucci PM. Home treatment with recombinant activated factor VII in patients with factor VIII inhibitors: the advantages of early intervention. Br J Haematol 1999; 104:22–26. Astermark J, Donfield SM, DiMichele DM, Gringeri A, Gilbert SA, Waters J, et al. A randomized comparison of bypassing agents in hemophilia complicated by an inhibitor: the FEIBA NovoSeven Comparative (FENOC) Study. Blood 2007; 109:546–551. Mauser-Bunschoten EP, Koopman MM, Goede-Bolder AD, Leebeek FW, van der Meer J, van Marwijk Kooij GM, et al. Efficacy of recombinant factor VIIa administered by continuous infusion to haemophilia patients with inhibitors. Haemophilia 2002; 8:649–656. Berntorp E. Differential response to bypassing agents complicates treatment in patients with haemophilia and inhibitors. Haemophilia 2009; 15:3–10. Livnat T, Martinowitz U, Zivelin A, Seligsohn U. Effects of factor VIII inhibitor bypassing activity (FEIBA), recombinant factor VIIa or both on thrombin generation in normal and haemophilia A plasma. Haemophilia 2008; 14:782–786. Ingerslev J, Poulsen LH, Sorensen B. Potential role of the dynamic properties of whole blood coagulation in assessment of dosage requirements in haemophilia. Haemophilia 2003; 9:348–352.
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Evaluating and monitoring the efficacy of recombinant activated factor VIIa in patients with haemophilia and inhibitors Xue Qi, Yongqiang Zhao, Kuixing Li, Liankai Fan and Baolai Hua Although the use of bypassing agents has dramatically improved the management of haemophilia in patients with inhibitors, questions remain regarding optimal dosing regimens and methodology for monitoring their clinical effectiveness. In this study, we evaluated the efficacy and safety of two different doses of recombinant activated factor VIIa (rFVIIa) in patients with haemophilia and inhibitors and assessed the feasibility of using thromboelastography (TEG) and thrombin generation assays (TGA) for monitoring the response to rFVIIa. Six patients aged 9–49 years with congenital or acquired haemophilia with inhibitors who experienced a total of nine bleeding episodes were included. Seven episodes were treated with conventional rFVIIa dosing (72.7–109.1 mg/kg), and two episodes were treated with a single high-dose regimen (254.6–264.0 mg/ kg). Clinical and haemostatic responses were evaluated. Haemostasis was assessed by prothrombin time (PT), activated partial thromboplastin time (aPTT), factor VII coagulant activity (FVII:C), TEG, and TGA. Six out of seven (85.7%) bleeding episodes responded to conventional rFVIIa dosing, and half (50%) responded to the high-dose regimen. No relationships between PT, aPTT, and FVII:C levels and clinical outcome were observed. However,
Introduction In patients with haemophilia, bleeding episodes are prevented or treated by intravenous replacement of the deficient clotting factor. A major complication of haemophilia treatment is the development of inhibitory antibodies to factors VIII or IX, which occurs in up to 25% of patients receiving replacement therapy [1,2]. Even though immune tolerance therapy can eradicate these inhibitors, this treatment is ineffective in approximately 30% of patients and can be expensive [3]. Bypassing agents, such as recombinant factor VIIa (rFVIIa; NovoSeven, Novo Nordisk, Bagsvaerd, Denmark), are well tolerated and efficacious in managing bleeding episodes in patients with inhibitors [4,5]. However, the optimal dosing regimen of rFVIIa in these patients has been debated. Although haemostatic efficacy was achieved in 92% of pat ients using the recommended dose of 90 mg/kg [6], the efficacy and safety of a single high dose of rFVIIa (270 mg/kg) have also been demonstrated [7]. Currently, there is no accepted method to monitoring the effectiveness of bypassing agents in clinical practice [8–10]. Even though monitoring of the haemostatic 0957-5235 ß 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins
changes in TEG and TGA parameters tended to correspond to clinical response, although large inter-individual variation in rFVIIa efficacy was noted. A good response was seen with rFVIIa in treating acute bleeding episodes in patients with haemophilia and inhibitors. Because changes in TEG and TGA may correlate with clinical outcomes of rFVIIa, TEG and TGA may be useful for monitoring rFVIIa activity in inhibitorpositive haemophilia. Blood Coagul Fibrinolysis 25:754–760 ß 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins. Blood Coagulation and Fibrinolysis 2014, 25:754–760 Keywords: haemophilia, inhibitors, recombinant activated factor VIIa, thrombin generation assay, thromboelastography Department of Hematology, Peking Union Medical College Hospital, Chinese Academy of Medical Science, and Peking Union Medical College, Beijing, China Correspondence to Baolai Hua, Department of Hematology, Peking Union Medical College Hospital, Chinese Academy of Medical Science, and Peking Union Medical College, No. 1 Shuaifuyuan, Dongcheng District, Beijing 100730, China Tel: +86 10 69155020; e-mail: [email protected] Received 24 September 2013 Revised 28 March 2014 Accepted 28 March 2014
effect of these agents may optimize outcomes, prospectively defined, objective criteria for the effectiveness of bypassing agents are lacking. Moreover, clinical studies of their efficacy have relied on subjective assessments by investigators. Haemostasis and its abnormalities traditionally have been assessed by plasma clotting times, such as prothrombin time (PT) and activated partial thromboplastin time (aPTT). However, these standard clotting assays do not reflect total thrombin generation, measure only the initiation of clot formation and not its speed or total extent, and may not be sensitive to hypercoagulation or hypocoagulation [11]. Consequently, these tests may not accurately reflect a patient’s risk of bleeding or bleeding state. Thromboelastography (TEG) and the thrombin generation assay (TGA) have been considered as methods for monitoring the response to bypassing therapy in recent years [12,13]. TEG is a test of overall haemostatic functioning performed on whole blood, and therefore measures both cellular and plasmatic effects on blood coagulation [14]. The TGA, which evaluates peak DOI:10.1097/MBC.0000000000000137
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Monitoring rFVIIa activity in haemophilia Qi et al. 755
thrombin production, the total amount of thrombin produced, and overall time course of thrombin generation [14,15], can be used to measure the overall kinetics of thrombin generation and the efficiency of all of the systems activating and inactivating coagulation [14]. Both methods have been proposed as tools for optimizing the dose and duration of rFVIIa therapy and avoiding its potential complications [12,15]. So far, the overall cases reported of using TEG and TGA to monitor the effectiveness of rFVIIa (both high and low doses) in patients with haemophilia and inhibitors are rather limited. Experiences of using rFVIIa to treat haemophilia patients in both low and high doses from the Asian patients are rare, let alone from Chinese patients. In this study, we evaluated the efficacy and safety of different doses of rFVIIa in Chinese patients with haemophilia with inhibitors and the feasibility of TEG and TGA for monitoring the response to treatment.
Methods Patients and study procedures
The study was approved by the Ethics Review Committee of the Chinese Academy of Medical Sciences and the Peking Union Medical College and conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained by the study subjects or their guardians before the start of the study. Study subjects included six patients aged 9–49 years (admitted during January through May 2010) with inhibitor-positive congenital haemophilia A or B and patients with acquired haemophilia. Patients included in the study had experienced mild or moderate bleeding, such as bleeding in the joint or muscles or haematuria within 24 h, and had not received bypass therapy within 72 h. Patients with major haemorrhage, and patients in whom past therapy with rFVIIa was ineffective, were excluded from the study. Anonymous identification numbers were used to maintain patient confidentiality. rFVIIa was administered in conventional or high-dose regimens. The conventional dose regimen was used in acute bleeding: rFVIIa was given as an intravenous (IV) bolus injection at a conventional dose of 90 mg/kg at baseline (hour 0) and a 90-mg/kg injection 2 h later (hour 2) if deemed necessary based on clinical/laboratory response. The high-dose regimen was administered if a re-bleed occurred. In this regimen, a single high dose of 270 mg/kg was administered. Clinical evaluations included evaluation of pain and bleeding, and were performed before dosing, 30 min and 2 h after dosing, and at the time of hospital discharge. Follow-up visits were also conducted by phone. Treatment response was characterized as good, partial, or poor based on the following criteria. Patients who did not require dose escalation or a switch to a different bypass therapy and who showed an improvement in bleeding-
related symptoms (arthralgia and haematuria) were considered to have a good response. Patients who did not meet one of these criteria but whose bleeding symptoms did not worsen were considered to have a partial response, and patients who did not meet either criteria or whose bleeding symptoms worsened during the initial treatment were considered to have a poor response [16]. Patients were also evaluated for treatment-related adverse events, including allergic reactions, thrombosis, or discomfort. Laboratory evaluations, which included assessments of PT, aPTT, factor VII coagulant activity (FVII:C), TEG, and TGA, were conducted before and 0.5 and 2 h after the first dose of rFVIIa administration for each bleeding episode. Blood sampling and laboratory assays
Peripheral venous blood samples were collected through a 21-gauge needle into Vacutainer tubes containing sodium citrate 0.11 ml/l (BD, Franklin Lakes, New Jersey, USA). After samples were stored for 15 min at room temperature, 1 ml of each sample was used in the TEG test and the rest was used to prepare platelet-poor plasma within 4 h of blood sampling. Platelet-poor plasma was obtained at room temperature by centrifugation at 3000 rpm for 15 min and stored at 808C for further analyses of PT, aPTT, FVII:C, and TGA. PT, aPTT, FVII:C, FVIII:C, and FIX:C were determined by one-stage assay. Inhibitors of FVIII and FIX (FVIII:I and FIX:I) were determined using the Bethesda method. Stago automated coagulation analyzer and its supporting reagents (Stago, Paris, France) were used for all these analyses. TEG (Haemoscope Corporation, Niles, Illinois, USA) was performed using the method described by Luddington and Reikvam et al. [17,18]. The numerical parameters assessed using TEG included the reaction time (R time), the kinetics time (K time), Alpha (the angle of tangent at 20 mm), representing the slope between R time and K time, and the maximum amplitude [19]. The R time is defined as the time from addition of calcium to the start of clot formation and denotes the latency time between placing blood in the sample cup until the clot starts to form (2-mm amplitude). The K time, or the clot formation time, is defined as the time from the start of clot formation to a clot firmness of 20 mm. Finally, the maximum amplitude evaluates the maximum clot firmness reached during analysis and assesses the clot’s rigidity/strength (fibrin and platelet binding). The following reference values were adopted: R time, 2–8 min; K time, 1–3 min; Alpha, 55–788; maximum amplitude, 51–69 mm. The calibrated automated TGA was conducted using the Thrombinoscope (Thrombinoscope BV, Maastricht, The Netherlands) according to the manufacturers’ instructions for thrombin generation. Fluorescence was
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756 Blood Coagulation and Fibrinolysis 2014, Vol 25 No 7
evaluated using an Ascent Reader (Thermo Electron and Fisher Scientific Company, Waltham, Massachusetts, USA), and thrombin generation curves were assessed using Thrombinoscope software. Four major thrombin generation parameters were studied using this technology: the lag time (min, the time to thrombin burst), the time to peak thrombin concentration (min), the peak thrombin height (nmol/l), and the endogenous thrombin potential (ETP, area under the curve in nmol/l per min) [20]. The following reference values were used: lag time 1.9 0.29 min; time to peak 4.1 0.4 min; peak height 446.2 52.8 nmol/l; ETP 1908 228.4 nmol/l per min [6,20,21]. The TGA was analyzed in the transfusion lab of Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China. Statistical analysis
Descriptive statistics were used to analyze PT, aPTT, FVII:C, the TEG parameters (R time, K time, Alpha angle, and maximum amplitude) and the TGA parameters (lag time, peak height, time to peak, and ETP) before and after rFVIIa administration. Data are reported by their median and range if not otherwise stated.
Results Six patients with haemophilia A or B with inhibitors or acquired haemophilia A were enrolled in the study, received rFVIIa therapy, and underwent haemostatic monitoring. Information on the demographics, baseline characteristics, and type of acute bleeding of the patients in the study is shown in Table 1. Nine acute bleeding episodes were reported. Seven bleeding episodes were treated with the conventional rFVIIa dose regimen (72.73–109.09 mg/kg) and two bleeding episodes were treated with the high-dose regimen (254.55–264.00 mg/kg). As shown in Table 1, the total efficacy of rFVIIa was 77.8% (7/9), and a good or partial response was observed in 85.7% (6/7) of patients receiving the conventional dose and 50% (1/2) receiving the high dose (Table 1). Three re-bleeds occurred in two patients (two in patient 3 and one in patient 4). Because patient 3 initially responded well to a conventional dose, Table 1
another conventional dose was given after the first rebleed, which successfully stopped the bleeding. However, a high dose was used to treat this patient’s second re-bleed. Tables 2 and 3 illustrate the impact of rFVIIa on PT, aPTT, and FVII:C. At baseline, all the patients showed normal values for PT and FVII:C and longer-than-normal values for aPTT. For both conventional dosing and high dosing, administration of rFVIIa shortened PT and aPTT and increased FVII:C levels. A numerically higher FVII:C level was observed following use of the high dose (Table 3) versus use of the conventional dose (Table 2). There was no association between changes in these parameters and response to treatment. As shown in Fig. 1, TEG parameters were undetectable and demonstrated nearly flat curves prior to the initiation of rFVIIa, even after 1 h of analysis. However, after rFVIIa was administered, TEG profiles improved, indicating that the use of rFVIIa accelerates clotting. Marked decreases in R and K times were observed, and a trend towards increased Alpha angle values was seen. Greater changes were seen with the higher-dose regimen than with the conventional dose regimen (Tables 2 and 3). There was significant variation among subjects and only one patient exhibited a concentration–response effect. Ex-vivo results showed an important increase in parameters following an injection of rFVIIa and the degree of improvement varied among the three clinical outcome groups studied (Table 2). Both the R time and K time were shorter in the ‘good response’ group compared with those in the ‘poor response’ group when evaluated both 30 min and 2 h after rFVIIa administration. Similarly, the Alpha angle increased more in the ‘good response’ group compared with those in the ‘poor response’ group. In contrast, there was no direct effect on the maximum amplitude, which is primarily determined by platelet count and fibrinogen concentration. TGA analyses yielded similar results (Table 2). Thrombin generation curves showed an important increase in thrombin generation capacity following injection of rFVIIa. Both 30 min and 2 h after the administration of
Demographics, baseline characteristics, and treatment response by patients in acute bleeding episodes
Patient no.
Sex/age (y)
Type of haemophilia
FVIII:C (IU/dl)
Inhibitor (BU/ml1)
1 2 3a
M/9 M/49 M/10
Haemophilia A Haemophilia A Haemophilia A
1 1 1
20 160 1.5
4b,c
M/20
Haemophilia A
1
1.2
5 6c
M/15 F/37
Haemophilia B AHA
1 1
1.3 80
Bleeding type Haematuria Joint bleeds Joint bleeds Joint bleeds Joint bleeds Haematuria Haematuria Joint bleeds Haematuria
rFVIIa dose (mg/kg)
Total doses for each bleeding
104.35 85.71 109.09 72.73 254.55 96.00 264.00 100.00 92.31
1 1 1 1 1 2 1 1 2
Dose
Treatment response
Conventional Conventional Conventional Conventional High Conventional High Conventional Conventional
Good Good Good Good Good Poor Poor Partial Good
AHA, acquired haemophilia, rFVIIa, recombinant activated factor VIIa; M, male. a Patient 3 experienced three acute bleeding episodes. Two episodes were treated with conventional dose and the third bleeding was treated with high dose. b Patient 4 experienced two acute bleeding episodes. One was treated with conventional dose and another was treated with high dose. c For the first bleeding episode of patient 4 and patient 6, a second dose was given 2 h after the first injection of rFVIIa.
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12.3 (12.1–13.0) 112.4 (103.1–117.1) 138 (108–147) NA NA NA NA 3.25 (3.00–3.67) 11.43 (9.00–13.10) 50.24 (33.39–62.61) 802.5 (475.5–1009.5)
12.0 104.8 125 NA NA NA NA 4.92 10.43 42.29 665.5
Partial 11.8 109.6 147 NA NA NA NA 4.83 17.33 30.71 491.0
Poor 7.6 66.9 2588 25.2 5.7 41.6 74.5 2.00 7.33 86.70 910.0
(7.5–8.5) (63.4–79.7) (1502–2730) (21.2–40.0) (4.3–8.0) (28.5–44.1) (67.0–80.9) (1.67–2.25) (6.67–8.17) (39.89–106.83) (509.0–1330.0)
Good, median (range) 7.7 54.7 2882 46.4 11.7 21.2 67.4 1.92 7.26 84.12 1042.5
Partial
0.5 h after
7.2 68.5 2882 74.2 27.8 8.2 48.3 2.17 11.67 38.84 604.5
Poor 8.0 76.5 1434 23.6 4.7 43.1 69.8 2.00 7.00 84.21 911.5
(7.8–8.6) (67.0–79.5) (1078–2730) (20.0–26.7) (3.2–8.0) (31.2–55.5) (65.9–78.7) (1.67–2.09) (6.67–8.26) (51.03–96.63) (572.0–1224.5)
Good, median (range)
8.1 60.9 1859 59.6 15.5 17.6 67.2 2.00 8.67 71.05 901.0
Partial
2.0 h after
7.6 79.8 1537 64.5 27.5 8.8 48.1 2.17 11.83 34.53 536.5
Poor
12.1 12.2 7.3 7.3 7.5 7.6
PT (s) 108.1 102.4 51.3 57.2 60.0 69.0
aPTT (s) 147 119 4868 5525 2962 3130
FVII:C (%) NA NA 9.7 66.8 15.5 44.8
R (min) NA NA 2.1 20.8 2.7 10.8
K (min)
TEG
NA NA 62.1 12.8 56.6 21.9
Alpha
NA NA 71.5 57.9 72.2 67.1
Maximum amplitude (mm)
3.59 3.50 2.25 2.17 1.92 2.17
Lag time (min)
9.26 15.00 7.76 11.00 7.76 11.83
ttPeak (min)
138.17 45.03 115.14 30.15 118.46 24.59
Peak (nmol/l)
TGA
1622 732.5 1325.5 499.5 1393.0 404.0
ETP (nmol/l/min)
aPTT, activated partial thromboplastin time; ETP, endogenous thrombin potential; FVII:C, factor VII coagulant activity; K, kinetics time; PT, prothrombin time; R, reaction time; rFVIIa, recombinant activated factor VIIa; TEG, thromboelastography.
2 h after
0.5 h after
3 4 3 4 3 4
Patient no.
PT, aPTT, and FVII:C
Haemostatic parameters before dose and at 0.5 and 2.0 h following the administration of high dose of rFVIIa in patients 3 and 4
Before dose
Table 3
aPTT, activated partial thromboplastin time; ETP, endogenous thrombin potential; FVII:C, factor VII coagulant activity; K, kinetics time; PT, prothrombin time; R, reaction time; rFVIIa, recombinant activated factor VIIa; TEG, thromboelastography; ttPeak, time to peak.
TGA
TEG
PT (s) aPTT (s) FVII:C (%) R time (min) K time (min) Alpha Maximum amplitude (mm) Lag time (min) ttPeak (min) Peak (nmol/l) ETP (nmol/l/min)
Good, median (range)
Before dose
Haemostatic parameters before dose and at 0.5 and 2.0 h following the administration of conventional dose of rFVIIa in groups defined by clinical response
PT, aPTT, and FVII:C
Table 2
Monitoring rFVIIa activity in haemophilia Qi et al. 757
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758 Blood Coagulation and Fibrinolysis 2014, Vol 25 No 7
Fig. 2
(a)
10 millimeters
Before 0.5 h after 2 h after
(a)
Thrombin (nmol/l)
Fig. 1
10 millimeters
120 100 80 60
0.5 h after
40
2 h after
20 0
(b)
Before
0
10
20
30
40
50
60
70
Time (min)
Before 0.5 h after 2 h after (c)
10 millimeters
Thrombin (nmol/l)
(b)
110 90 70
Before
50
0.5 h after
30
2 h after
10 –10
0
10
20
30
40
50
Time (min)
Thromboelastography profiles in patients with inhibitor-positive haemophilia before and after treatment in patients with a good response (a: patient 3), partial response (b: patient 5), and poor response (c: patient 4).
rFVIIa, decreased lag time and time to peak, increased peak thrombin generation, and a marked increase in ETP were observed, but these values still remained below the reference range. As in the TEG analyses, inter-individual variation in these parameters was large. TGA parameters improved in all patients, regardless of the clinical response. However, changes in TGA profiles were different in each response group (Fig. 2). Thirty minutes and 2 h after administration of the first dose, the lag time and time to peak were shorter in the ‘good response’ group compared with those in the ‘poor response’ group. Similarly, peak thrombin and ETP increased more in the ‘good response’ group compared with those in the ‘poor response’ group.
Discussion Results from our study confirmed the efficacy and safety of rFVIIa in improving haemostasis during acute bleeding episodes in patients with congenital or acquired haemophilia and inhibitors. Of the nine acute bleeding episodes included in the analysis, seven were treated
(c) Thrombin (nmol/l)
Before 0.5 h after 2 h after
120 100 80 60
Before
40
0.5 h after 2 h after
20 0 –20
0
10
20
30
40
50
60
70
Time (min) Thrombin generation as assessed by thrombin generation assay in patients with inhibitor-positive haemophilia who exhibited a good (a: patient 3), partial (b: patient 5), or poor (c: patient 4) response to recombinant activated factor VIIa.
with conventional doses (72.7–109.1 mg/kg), and two were treated with high doses (254.6–264.0 mg/kg). A good or partial response was reported in six of seven (85.7%) bleeding episodes following the use of conventional doses and in one of two (50%) bleeding episodes following the use of high doses. The overall therapeutic efficacy rate observed in this study was 77.8% (7/9). These data are consistent with data from other studies that have reported total efficacy rates of 92% with conventional doses [6] and 65% with a single dose of high-dose therapy [7]. Other reports of the efficacy of
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Monitoring rFVIIa activity in haemophilia Qi et al. 759
conventionally dosed rFVIIa have ranged from 70–80%. The previous finding of effectiveness of rFVIIa was reassured in our study. Several factors can affect response rates in studies of rFVIIa therapy in patients with haemophilia with inhibitors. One, the timing of treatment appears to be critical. Some data suggest that earlier administration of rFVIIa is associated with a greater response [22]. More frequent bleeding in the treated joint or presence of a target joint is also related to lower ratings of efficacy [23]. Because response rates have been reported to be greater in patients with episodes of joint bleeding than in those with episodes of bleeding outside the joints, the sites of bleeding may also affect treatment response [24]. In our study, rFVIIa achieved a good or a partial response in all subjects with joint bleeds. Although patients 3 and 4 exhibited the same titers of inhibitors, their responses to treatment were remarkably different. Although both conventional and high dose of rFVIIa provided successful haemostasis following acute bleeding episodes in patient 3, neither conventional nor high dose rFVIIa induced haemostasis in patient 4. In this patient, bleeding stopped after switching to prothrombin complex concentrates (PCCs). The different mechanisms of action between rFVIIa and PCC provide a theoretical foundation for inter-individual variation in the clinical efficacy of these agents. Several patient-specific factors may also contribute to the differences in responses to rFVIIa and other bypassing agents. These include variations in TF, prothrombin, protein C, protein S, antithrombin III, TF pathway inhibitor, and tissue plasminogen activator levels, as well as polymorphisms in FV Leiden and endothelial protein C receptors [25]. Our evaluation of the utility of several strategies for monitoring the haemostatic efficacy of rFVIIa confirmed that rFVIIa decreases PT and aPTT and increases FVII:C, as expected. However, no association between changes in these markers of parameters and the therapeutic efficacy of rFVIIa was observed. Because these tests only detect the initial thrombin generated, not the total thrombin produced, they are not suitable for use in rFVIIa monitoring. This study also demonstrates the superiority of assessments of overall coagulation potential, such as TEG and TGA, to traditional clotting parameters in evaluating haemostasis in patients with haemophilia and inhibitors. Unlike changes in PT, aPTT, or FVII:C levels, changes in TEG and TGA parameters reflect changes in the rate of thrombin generation and thrombin generation capacity and appear to relate to clinical outcome. In this study, treatment with rFVIIa was associated with important changes in TEG parameters, such as a reduction in the time to the start of clot formation, reductions in the time to clot strength of 20 mm, and increased thrombin generation. Substantial changes in TGA parameters were also
noticed, including reductions in the lag in thrombin formation and time to peak thrombin generation, as well as an increase in peak thrombin generation and ETP. These trends have been observed in other studies of the utility of TEG and TGA [16,26]. No consistent correlation between improvements in TEG and TGA parameters and rFVIIa doses was reported, possibly because of a large variation in responses and the small number of patients in the study. Large inter-individual differences in TEG responses have been reported in similar studies, including those involving patients with moderate and severe haemophilia [27]. In one such study, FVIII:C levels required to normalize the whole blood coagulation profile in some patients with severe haemophilia was 10 times higher than those in other patients with severe disease. Our results differ from those reported by Ay et al. [9] in their study of the feasibility of using TGA and TEG for monitoring bypass therapy in seven patients with inhibitors. In this study of seven patients who experienced 17 bleeding episodes, TEG and TGA were used to assess the haemostatic impact of rFVIIa at a dose of 80–115 mg/ kg (used to treat six episodes) or activated PCC (aPCC) at 50–100 IU/kg per dose (used to treat 11 episodes). Assessments were conducted at baseline and at 1 and 24 h after bypass therapy, and when clinical haemostasis was obtained. In this study, no association between clinical response to rFVIIa or aPCC and TEG or TGA parameters was observed, leading the authors to conclude that the clinical effectiveness of bypass therapy cannot be assessed by either technology. However, this study and our study had several key methodological differences. For example, our study only used rFVIIa as bypass agent therapy, used different definitions of clinical response, and a narrower interval between TEG/TGA evaluations, suggesting the need for greater standardization of these assessments [9]. Although total number of cases included in the current study was small because of the difficulty of recruitment, the findings brought fresh insights for Chinese haematologists who have relatively limited experiences of rFVIIa usage in patients with haemophilia with inhibitors. Data obtained from the study were consistent with clinical practice and expectations for Chinese patients. Conclusion
In conclusion, TEG and TGA may represent potential surrogate markers for monitoring the impact of bypassing agents such as rFVIIa. These assays may ultimately facilitate the assessment of a patient’s risk of bleeding and thrombotic complications and help clinicians optimize dosing strategies and provide individually tailored treatment regimens. Even though both assays can be useful, the use of TGA is frequently limited to laboratory analyses in academic settings [9]. Regardless of the test
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760 Blood Coagulation and Fibrinolysis 2014, Vol 25 No 7
used, additional studies relating clinical and laboratory findings are necessary to determine which TEG and TGA parameters best predict response. The utility of TEG and TGA also may be increased by standardizing TEG and TGA reagents, methodology, reporting, and interpretation. Further studies should therefore focus on optimizing TEG and TGA methodology to increase the sensitivity of these important technologies.
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Acknowledgements Nicole Cooper of MedVal Scientific Information Services, LLC, provided medical writing and editorial assistance, funding for which was provided by Novo Nordisk Inc. Conflicts of interest
Source of funding: X.Q., B.H., K.L., L.F., and Y.Z.: The drug used in this trial was provided by Novo Nordisk, China. The authors have no other potential conflicts of interest to report.
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