Continuous infusion of B-domain deleted recombinant factor VIII (ReFacto) in patients with haemophilia A undergoing surgery: clinical experience

Continuous Infusion of Factor VIII and von Willebrand Factor in Surgery: Trials with pdFVIII LFB or pdVWF LFB in Patients with Bleeding Disorders

INTRODUCTION

A plasma-derived factor VIII product (pdFVIII, Factane 100 or 200 IU/mL) and a plasma-derived von Willebrand factor product (pdVWF, Wilfactin 100 IU/mL) are approved for replacement therapy by intravenous bolus injections in haemophilia A (HA) and von Willebrand disease (VWD), respectively. However, in situations requiring intensive treatment, continuous infusion (CI) may be desirable to better control target plasma factor levels.

AIM

To evaluate the perioperative haemostatic efficacy and safety of these concentrates administered by CI.

METHODS

Three phase III trials were conducted. Adults with HA (FVIII:C <1%) (Studies 1 and 2) or VWD (VWF:RCo <20%) (Study 3) received a preoperative bolus followed by CI of undiluted concentrate for at least 6 days. Bolus doses and CI rates were based on individual recovery and clearance, respectively. Initial infusion rate had to be higher for 48 hours for HA and 24 hours for VWD patients to anticipate potential fluctuations of factor concentrations during major surgery. Target levels of FVIII:C in HA and VWF:RCo in VWD were 80 and 70 IU/dL, respectively. Efficacy was assessed using a global haemostatic efficacy score.

RESULTS

Studies 1, 2, and 3 included 12, 4 and 6 patients, respectively. Efficacy outcomes were excellent/good in all 22 major surgeries including 18 orthopaedic procedures. Most daily measured FVIII and VWF levels (92%) were on target. No safety concerns, thrombotic events or inhibitors were identified.

CONCLUSION

pdFVIII and pdVWF administered by CI represent an effective and safe alternative to bolus injections in patients with severe HA or VWD undergoing surgery.

Setting the stage for individualized therapy in hemophilia: What role can pharmacokinetics play?

Replacement therapy with clotting factor concentrates (CFC) is the mainstay of treatment in hemophilia. Its widespread application has led to a dramatic decrease in morbidity and mortality in patients, with concomitant improvement of quality of life. However, dosing is challenging and costs are high. This review discusses benefits and limitations of pharmacokinetic (PK)-guided dosing of replacement therapy as an alternative for current dosing regimens. Dosing of CFC is now primarily based on body weight and based on its in vivo recovery (IVR). Benefits of PK-guided dosing include individualization of treatment with better targeting, more flexible blood sampling, increased insight into association of coagulation factor levels and bleeding, and potential overall lowering of overall costs. Limitations include a slight burden for the patient, and availability of closely collaborating, experienced clinical pharmacologists.

Ankle fusion in hemophilic patients

INTRODUCTION

Hemophilic arthropathy is painful and disabling. We report a retrospective study of ankle fusion with intra- and peri-operative clotting factor perfusion. The objective was to assess the efficacy of maintaining perioperative clotting factor rates close to 100%, and report long-term results. The study hypothesis was that results would be good, without early hemorrhagic complications.

MATERIAL AND METHOD

Between 2000 and 2013, 12 ankle fusions were performed in 9 patients, with a mean age of 39years (range, 19-58years). Anti-hemophilic factor perfusion was controlled by the reference physician of the Regional Hemophilia Treatment Center. Clinical AOFAS and Olerud scores and the Pettersson radiologic score were used for assessment. Mean preoperative AOFAS score was 22 (range, 2-55) and mean Olerud score 7 (range, 5-12). Mean preoperative factor VIII concentration was <1% (range, <1-3%).

RESULTS

Mean follow-up was 8years (range, 2-16years). Mean AOFAS score at follow-up was 69 (range, 35-92) and mean Olerud score 70 (range, 30-100). Improvement mainly concerned the Pain dimension. Statistical analysis found a significant difference between pre- and post-operative clinical scores (AOFAS, P=0.004; Olerud, P=0.004). Mean factor VIII concentration at surgery was 90% (range, 24-117%), and 109% (range, 75-152%) the day following surgery. There were no cases of hematoma or surgical site infection. Radiologic fusion was systematic at a mean 3.5 months (range, 3-4months).

CONCLUSION

The study hypothesis was confirmed. Ankle fusion in advanced hemophilic arthropathy improved function and quality of life. Perioperative clotting factor perfusion contributed to these good results, providing supplementary prevention of hemorrhagic risk.

LEVEL OF EVIDENCE

IV, retrospective study.

A population pharmacokinetic model for perioperative dosing of factor VIII in hemophilia A patients

The role of pharmacokinetic-guided dosing of factor concentrates in hemophilia is currently a subject of debate and focuses on long-term prophylactic treatment. Few data are available on its impact in the perioperative period. In this study, a population pharmacokinetic model for currently registered factor VIII concentrates was developed for severe and moderate adult and pediatric hemophilia A patients (FVIII levels <0.05 IUmL^-1) undergoing elective, minor or major surgery. Retrospective data were collected on FVIII treatment, including timing and dosing, time point of FVIII sampling and all FVIII plasma concentrations achieved (trough, peak and steady state), brand of concentrate, as well as patients' and surgical characteristics. Population pharmacokinetic modeling was performed using non-linear mixed-effects modeling. Population pharmacokinetic parameters were estimated in 75 adults undergoing 140 surgeries (median age: 48 years; median weight: 80 kg) and 44 children undergoing 58 surgeries (median age: 4.3 years; median weight: 18.5 kg). Pharmacokinetic profiles were best described by a two-compartment model. Typical values for clearance, intercompartment clearance, central and peripheral volume were 0.15 L/h/68 kg, 0.16 L/h/68 kg, 2.81 L/68 kg and 1.90 L/68 kg. Interpatient variability in clearance and central volume was 37% and 27%. Clearance decreased with increasing age (P<0.01) and increased in cases with blood group O (26%; P<0.01). In addition, a minor decrease in clearance was observed when a major surgical procedure was performed (7%; P<0.01). The developed population model describes the perioperative pharmacokinetics of various FVIII concentrates, allowing individualization of perioperative FVIII therapy for severe and moderate hemophilia A patients by Bayesian adaptive dosing.

Perioperative treatment of hemophilia A patients: blood group O patients are at risk of bleeding complications

ESSENTIALS: Targeting of factor VIII values is a challenge during perioperative replacement therapy in hemophilia. This study aims to identify the extent and predictors of factor VIII underdosing and overdosing. Blood group O predicts underdosing and is associated with perioperative bleeding. To increase quality of care and cost-effectiveness of treatment, refining of dosing is obligatory.

SUMMARY

BACKGROUND

Perioperative administration of factor VIII (FVIII) concentrate in hemophilia A may result in both underdosing and overdosing, leading to respectively a risk of bleeding complications and unnecessary costs.

OBJECTIVES

This retrospective observational study aims to identify the extent and predictors of underdosing and overdosing in perioperative hemophilia A patients (FVIII levels < 0.05 IU mL(-1)).

PATIENTS AND METHODS

One hundred nineteen patients undergoing 198 elective, minor, or major surgical procedures were included (median age 40 years, median body weight 75 kg). Perioperative management was evaluated by quantification of perioperative infusion of FVIII concentrate and achieved FVIII levels. Predictors of underdosing and (excessive) overdosing were analyzed by logistic regression analysis. Excessive overdosing was defined as upper target level plus ≥ 0.20 IU mL(-1).

RESULTS

Depending on postoperative day, 7-45% of achieved FVIII levels were under and 33-75% were above predefined target ranges as stated by national guidelines. A potential reduction of FVIII consumption of 44% would have been attained if FVIII levels had been maintained within target ranges. Blood group O and major surgery were predictive of underdosing (odds ratio [OR] 6.3, 95% confidence interval [CI] 2.7-14.9; OR 3.3, 95% CI 1.4-7.9). Blood group O patients had more bleeding complications in comparison to patients with blood group non-O (OR 2.02, 95% CI 1.00-4.09). Patients with blood group non-O were at higher risk of overdosing (OR 1.5, 95% CI 1.1-1.9). Additionally, patients treated with bolus infusions were at higher risk of excessive overdosing (OR 1.8, 95% CI 1.3-2.4).

CONCLUSION

Quality of care and cost-effectiveness can be improved by refining of dosing strategies based on individual patient characteristics such as blood group and mode of infusion.

Low-dose continuous infusion of factor VIII in patients with haemophilia A

BACKGROUND

Patients with haemophilia A (HA) or B (HB) can be given prophylactic or on-demand treatment administered by continuous infusion or bolus injections of factor VIII (FVIII) or IX (FIX). In this study we evaluated the efficacy and safety of low-dose continuous infusion of FVIII or FIX.

MATERIAL AND METHODS

We studied all eligible patients with HA or HB treated with continuous infusion of factor concentrates over an 18-year period in a single Slovenian Haemophilia Comprehensive Care Centre. Treatment started with a bolus injection of FVIII or FIX, followed by continuous infusion at the initial rate of 2 IU/kg/h of FVIII in HA patients and 4.5 IU/kg/h of FIX in HB patients. The infusion rate was subsequently adjusted according to the indication for therapy.

RESULTS

A total of 66 continuous infusions (40 in major surgery, 10 in minor surgery and 16 with bleeding episode) in 46 HA patients and 16 (15 in severe and 1 in mild HA) in eight HB patients were included in the study. During the first week of treatment, the median continuous infusion rates in HA patients undergoing major surgery, minor surgery and a bleeding event were 2.18 (0.75-3.68), 1.48 (1.0-2.54) and 2.24 (1.33-3.93) IU/kg/h, respectively. The median FVIII activities were 0.69 (0.37-1.19), 0.47 (0.39-0.84) and 0.52 (0.36-1.06) IU/mL. After the first week of treatment, even lower doses of FVIII were needed. Red blood cell transfusions had to be administered to three patients (2 with severe and 1 with moderate HA) during the continuous infusion and inhibitors developed in five patients. In HB patients, the median continuous infusion rate was 1.85 (1.07-2.94) IU/kg/h and the median FIX activity was 0.62 (0.30-1.04) IU/mL. Red blood cell transfusions were not required, and thrombophlebitis and inhibitors did not appear.

DISCUSSION

Overall, low-dose continuous infusion was shown to be an effective and safe way of treating patients with HA. The protocol used also proved efficient and safe in all HB patients.

The "OPTI-CLOT" trial. A randomised controlled trial on periOperative PharmacokineTIc-guided dosing of CLOTting factor concentrate in haemophilia A

Haemophilia A is an X-linked inherited, rare bleeding disorder, caused by a deficiency of coagulation factor VIII (FVIII). Previous studies in prophylactic dosing have demonstrated that FVIII consumption can be significantly reduced by individualising dosing based on combined analysis of individual pharmacokinetic (PK) profiling and population PK data (Bayesian analysis). So far, no studies have been performed that address perioperative concentrate consumption using iterative PK-guided dosing based on a PK population model. The "OPTI-CLOT" trial is an open-label, prospective, multicentre randomised controlled superiority trial (RCT), aiming to detect a 25 % difference in perioperative FVIII concentrate consumption with iterative Bayesian PK-guided dosing in comparison to the standard dosing procedure. Sixty haemophilia A patients ≥ 12 years of age, with FVIII plasma levels ≤ 0.05 IUml(-1) will be included requiring FVIII replacement therapy administered either by continuous or bolus infusion for an elective, low or medium risk surgical procedure. The proposed study aims to investigate a novel perioperative iterative PK-guided dosing strategy, based on a recently constructed perioperative PK population model. This model will potentially decrease underdosing and overdosing of clotting factor concentrate and is expected to overall reduce FVIII consumption by minimally 25 %. Moreover, participating hospitals will gain experience with PK-guided dosing, facilitating future implementation of this intervention which is expected to optimise current care and reduce costs of treatment.

Total knee arthroplasty in severe haemophilic patients under continuous infusion of clotting factors

PURPOSE

Haemophilic arthropathy is painful, invalidating and destructive. Authors report a prospective study of total knee arthroplasties in patients with severe haemophilia under continuous infusion of clotting factors. The purpose is to evaluate the benefits of continuous infusion of clotting factors regarding long-term functional improvement and radio-clinical results.

METHODS

From 1998 to 2009, 20 total knee arthroplasties were implanted in 14 patients with a mean age of 36.5 years (24-56). A continuous infusion of anti-haemophilic factors was used and supervised by the physician of the Regional Haemophilia Treatment Centre (CRTH). Evaluation was clinical using the HSS and Oxford scores and radiological.

RESULTS

One patient was lost to follow-up. Median follow-up is 66.5 months (6-134). Oxford score at latest follow-up is 42 (37-46). On revision, HSS score is 91 (84-96). Median flexion gain is 32.5° (-20; 75°). There is a median flexion contracture of 5° (0-15°) and a median extension improvement of 22.5°. We report 2 secondary infectious complications, concerning the same operated knee of a single patient. No post-operative haematoma was reported in our study.

CONCLUSION

Total knee arthroplasty in haemophilic arthropathy improves both the function and quality of life of this group of patients. Continuous infusion of clotting factors contributes significantly to these results, by allowing early and intensive rehabilitation, and offers security regarding haemorrhagic complications commonly described in the literature and that we have not encountered in our study.

LEVEL OF EVIDENCE

Therapeutic study, Level IV.

Evidence-based patient safety advisory: blood dyscrasias

Rarely, patients with blood disorders may seek to undergo plastic surgery. Although plastic surgeons are not expected to diagnose or manage blood disorders, they should be able to recognize which patients are suitable for surgery and which should be referred to a hematologist before a procedure. This practice advisory provides an overview of the perioperative steps that should be completed to ensure appropriate care for patients with blood disorders.

Continuous infusion of coagulation factors: current opinion

PURPOSE OF REVIEW

To review the most recent reports on continuous infusion of coagulation factors, focusing on the current issues relating to this mode of therapy.

RECENT FINDINGS

Continuous infusion has been extensively used as an alternative to intermittent bolus factor replacement since the 1990s. To date, more than 100 reports comprising more than 800 continuous infusion treatments in various clinical situations have been published, with an increase in the current utilization of recombinant coagulation factors. An excellent hemostatic efficacy of continuous infusion has been reported. Continuous infusion protocols, however, still vary widely in terms of the different hemostatic levels targeted, dosage regimens, modes of continuous infusion and duration of therapy, which obviously result in variations in the cost-effectiveness reported by different centers.

SUMMARY

Continuous infusion has been shown to be a safe and cost-effective mode of replacement for treatment of hemophilia. The lack of evidence-based information on the hemostatic levels to be maintained in specific clinical situations, and recent concerns regarding the development of inhibitors, particularly in patients with mild hemophilia treated with continuous infusion, need to be addressed by prospective, randomized studies that compare traditional intermittent injections and the continuous infusion mode of factor replacement.

A postmarketing surveillance study of the safety and efficacy of ReFactoR (St Louis-derived active substance) in patients with haemophilia A

This clinical trial evaluated the safety and efficacy of ReFacto (St Louis-derived active substance) in patients with severe or moderately severe haemophilia A over a period of 6 months or 50 exposure days (EDs), whichever occurred first. Sixty patients, 58 previously treated and two previously untreated, were enrolled into this study. This was an open-label, multicentre, postmarketing surveillance study in which patients received prophylaxis or on-demand treatment as determined by their doctor. Surgical prophylaxis was evaluated in seven patients requiring elective surgery. Thirty-two patients aged <1 to 66 years (median 19.5) received prophylaxis and 28 patients, aged 1-71 years (median 33.5), received on-demand treatment. The majority of patients had severe haemophilia A (FVIII:C < 2%): 84.4% in the prophylaxis group and 85.7% in the on-demand group. Prophylaxis with ReFacto was associated with a median of 6.7 bleeds per year (range: 0-37). The investigator's assessment of final outcome for prophylactic treatment was excellent or effective for 93.1% of patients. ReFacto resolved 92.8% of bleeds with one or two infusions. The investigator's assessment was excellent or good for 98.2% of bleeds treated with ReFacto. Haemostasis was achieved for all seven surgical cases and ReFacto gave an excellent or good response for each. The nature and incidence of adverse events was as expected and no new safety concerns emerged. One previously treated patient (PTP) developed a high-titre inhibitor (maximum 75 BU) and one minimally treated patient (MTP) developed a low-titre inhibitor while on the study but eventually achieved high titres (maximum 30 BU) after immune tolerance therapy was initiated with a plasma-derived FVIII product. One previously untreated patient (PUP) developed a transient low-titre inhibitor (0.4 BU). Other serious adverse events (SAEs) were unrelated to study treatment. There were no allergic events. The results of this study are consistent with the previously published ReFacto pivotal studies.