Optimal treatment strategies for hemophilia: achievements and limitations of current prophylactic regimens

Lonoctocog alfa (rVIII-SingleChain) for the treatment of haemophilia A

INTRODUCTION

The administration of factor VIII (FVIII) concentrates on-demand or on long-term prophylaxis is the effective and safe standard of care of patients with hemophilia A (HA). Development of neutralizing antibodies against exogenous FVIII and the short half-life of the current available products remain major challenges. There is currently a great interest towards newer FVIII products with the goal of reducing the inhibitor risk and increasing the half-life. Area covered: In this review, the authors describe the efficacy and safety of rVIII-SingleChain (Lonoctocog alfa), the first and only single chain recombinant FVIII (rFVIII) molecule developed for the prevention and treatment of bleeding episodes in HA patients. The pre-clinical and clinical studies of rVIII-SingleChain as well as the results of the AFFINITY trial program in previously treated patients both adults and pediatric are presented and discussed. Expert opinion: The results from PTP studies document the efficacy and safety profile of the rVIII-SingleChain. However, even if rFVIII-SingleChain presents advantageous pharmacokinetic features compared to conventional rFVIII, it should not be considered as an EHL-FVIII while its immunogenicity is currently being studied in PUPs. The slightly better PK profile of rFVIII-SingleChain could however allow a small number of selected patients to be treated with a less intensive regimen.

Contemporary issues in the management of von Willebrand disease

Von Willebrand disease (VWD) is the most common inherited bleeding disorder. Bleeding scores in VWD, focused in particular on mucosal bleeding, can be very useful in the diagnosis and validation of different types of treatment. The results of an extended prospective study with a large amount of information on clinical phenotype and implications in treatment are reviewed in this article. Treatment of mucosal and joint bleeding in severe VWD remains difficult in some patients. Due to the lack of data on the use of prophylaxis in these patients it is difficult to establish optimal treatment regimens. An overview of the literature, with a focus on the ongoing PRO.WILL study, is provided here. Furthermore, understanding the changes in von Willebrand factor (VWF) levels during pregnancy is very important for establishing the optimal management strategy for pregnancy and delivery in women with VWD. A recently published prospective observational cohort study in women with and without VWD during the postpartum period provides important data that should allow the improvement of postpartum treatment protocols.

Bone Density Status in Bleeding Disorders: Where Are We and What Needs to Be Done?

Bleeding disorders, including hemophilia, can be seen in every ethnic population in the world. Among various bleeding disorders, reduced bone density has been addressed in hemophilia A. In recent years, there has been an increasing interest in addressing osteopenia and osteoporosis in hemophilia A. There is little or no study about the possible susceptibility of other individuals with bleeding disorders to reduced bone density. Questions have been raised about the role of blood coagulation factors in bone mineralization. This review provides new insight and ideas for further survey in the field of bleeding disorders and reduced bone density.

Improved joint health in subjects with severe haemophilia A treated prophylactically with recombinant factor VIII Fc fusion protein

INTRODUCTION

Joint arthropathy is the long-term consequence of joint bleeding in people with severe haemophilia.

AIM

This study assessed change in joint health over time in subjects receiving recombinant factor VIII Fc fusion protein (rFVIIIFc) prophylaxis.

METHODS

ALONG is the phase 3 pivotal study in which the benefit of rFVIIIFc as a prophylactic treatment for bleeding control was shown in previously treated severe haemophilia patients ≥12 years of age (arm 1: 25-65 IU/kg every 3-5 days, arm 2: 65 IU/kg weekly and arm 3: episodic). After completing ALONG, subjects had the option to enrol into the extension study (ASPIRE). This interim, post hoc analysis assessed changes in joint health over ~2.8 years in these patients.

RESULTS

Forty-seven subjects had modified Haemophilia Joint Health Score (mHJHS) data at A-LONG baseline, ASPIRE baseline and ASPIRE Year 1 and Year 2. Compared with A-LONG baseline (23.4), mean improvement at ASPIRE Year 2 was -4.1 (95% confidence interval [CI], -6.5, -1.8; P = .001). Regardless of prestudy treatment regimen, subjects showed continuous improvement in mHJHS from A-LONG baseline through ASPIRE Year 2 (prestudy prophylaxis: -2.4, P = .09; prestudy episodic treatment: -7.2, P = .003). Benefits were seen in subjects with target joints (-5.6, P = .005) as well as those with severe arthropathy (-8.8, P = .02). The mHJHS components with the greatest improvement at ASPIRE Year 2 were swelling (-1.4, P = .008), range of motion (-1.1, P = .03) and strength (-0.8, P = .04).

CONCLUSIONS

Prophylaxis with rFVIIIFc may improve joint health over time regardless of prestudy prophylaxis or episodic treatment regimens.

Modeling of Body Weight Metrics for Effective and Cost-Efficient Conventional Factor VIII Dosing in Hemophilia A Prophylaxis

The total body weight-based dosing strategy currently used in the prophylactic treatment of hemophilia A may not be appropriate for all populations. The assumptions that guide weight-based dosing are not valid in overweight and obese populations, resulting in overdosing and ineffective resource utilization. We explored different weight metrics including lean body weight, ideal body weight, and adjusted body weight to determine an alternative dosing strategy that is both safe and resource-efficient in normal and overweight/obese adult patients. Using a validated population pharmacokinetic model, we simulated a variety of dosing regimens using different doses, weight metrics, and frequencies; we also investigated the implications of assuming various levels of endogenous factor production. Ideal body weight performed the best across all of the regimens explored, maintaining safety while moderating resource consumption for overweight and obese patients.

Patient powered prophylaxis: A 12-month study of individualized prophylaxis in adults with severe haemophilia A

INTRODUCTION

Adults with severe haemophilia A (SHA) may experience breakthrough bleeds despite standard weight-based FVIII prophylaxis three times weekly. Individualized prophylaxis has evolved to optimize patient outcomes.

AIMS

This study aimed to evaluate the impact of a standardized approach to individualized prophylaxis on annualized bleeding rates (ABR), factor utilization, physical activity and quality of life in adults with SHA.

METHODS

In this prospective cohort study, patients with baseline FVIII:C <2% and ABR >3 on weight-based prophylaxis received a standardized approach to individualized prophylaxis. Changes in ABR, annualized FVIII consumption and adherence from the 12-month prestudy and 12-month intervention period were compared. Changes in Haemo-QoL-A total score, Physical Functioning (PF) subscale and physical activity level measured by accelerometry were also examined.

RESULTS

Eighteen patients participated (median age 26 years). Individualized prophylaxis decreased total bleeds in the population by 69% and traumatic bleeds by 73%. The median ABR decreased from 7.5 to 2 (P<.001). Annualized factor consumption increased by 7.3%, as a result of 66% reduction in factor utilization for treatment of bleeds and 25% increase in factor utilization for prophylaxis. Adherence scores for frequency and dosing did not change. There was a significant increase in the Haemo-QoL-A total score (P=.02) and PF score (P=.01) from baseline to 4 months but no change in physical activity.

CONCLUSION

Patients with SHA who switched from standard to individualized prophylaxis show reduced ABR and increased FVIII consumption, and also improved their health-related quality of life. The mechanism is independent of adherence to prescribed prophylactic regimen.

Surgery and survival in birth cohorts with severe haemophilia and differences in access to replacement therapy: The Malmö experience

BACKGROUND

Persons with severe haemophilia require lifelong replacement therapy, prophylaxis, to prevent bleeding. Data describing long-term outcomes of prophylactic treatment are scarce. The aim of this study was to investigate joint surgery and survival among persons with severe haemophilia with special attention to access to prophylaxis in the early years of life.

METHODS

Eligible participants had severe haemophilia A or B and were treated at the Malmö centre from the 1960s onward. Time from birth until joint surgery was analysed for participants negative for factor inhibitor and alive in 2000. We compared survival among the entire cohort with severe haemophilia treated at the Malmö centre with the general male population of Sweden and a sample of persons with severe haemophilia from the United Kingdom (UK).

RESULTS

Overall, 167 participants were included, 106 (63.5%) of whom had complete data on joint surgery. Among those born before 1970, 1970-1979 and ≥1980 approximately 37%, 21% and 0% had their first joint surgery by age 30, respectively. There were no second joint surgeries reported in cohorts born ≥1970. Persons with severe haemophilia and negative for HIV treated in Malmö have attained approximately similar survival to that of the general male population in Sweden and live slightly longer than persons with severe haemophilia from the UK.

DISCUSSION AND CONCLUSION

Prophylaxis in Sweden, although costly, has markedly improved survival and joint outcomes for persons with severe haemophilia. This study highlights the importance of early start of replacement therapy to prevent or postpone serious joint damage.

Long-term efficacy and safety of prophylaxis with recombinant factor VIII in Chinese pediatric patients with hemophilia A: a multi-center, retrospective, non-interventional, phase IV (ReCARE) study

BACKGROUND

The first recombinant factor VIII (rFVIII) product was launched in China in 2007. However, until now, no study has been conducted to describe the efficacy and safety of prophylaxis with rFVIII in Chinese pediatric patients with hemophilia A (HA).

OBJECTIVE

To summarize the efficacy and safety data on prophylaxis with rFVIII in Chinese pediatric patients with HA.

METHODS

ReCARE (Retrospective study in Chinese pediatric hemophilia A patients with rFVIII contained regular prophylaxis) was a retrospective study conducted in 12 hemophilia treatment centers (HTCs) across China. The primary endpoints included reduction in annualized bleeding rate (ABR); the secondary endpoints included evaluation of joint function (number and sites of target joints) using Gilbert score and Hemophilia Joint Health Score (HJHS), quality of life (QoL) and factors affecting treatment choices. Safety assessment of rFVIII was also conducted.

RESULTS

We analyzed a total of 183 male pediatric patients (mean age, 7.1 ± 4.23 years) who received prophylaxis between 1 November 2007 and 31 May 2013. Compared with baseline, prophylaxis with rFVIII significantly reduced overall annualized joint bleed rate (AJBR) (p < .001) and ABR (p < .001). Inhibitor formation was reported in 5 (2.7%) patients and hemarthrosis was reported in 1 patient. The mean number of target joints was positively related to age (p < .001) and weight (p = .003) at baseline. Responses from survey questionnaires reported that effective bleeding control, joint protection, improvement in quality of life, favorable medical insurance policies, and economic capability were reasons for choosing prophylaxis.

CONCLUSION

Prophylaxis with rFVIII reduced bleeding and number of target joints, even with a low-dose regimen, in Chinese pediatric patients with HA. Other than the efficacy and safety, factors such as poor disease control, improved economic stability and stable financial support made prophylaxis as an attractive treatment option. ClinicalTrials.gov ID: NCT02263066.

Home infusion teaching practices at federally funded hemophilia treatment centers in the United States of America

BACKGROUND

Home management of hemophilia is standard of care in many countries. This study examined current nursing practices in teaching home infusion (HI) at hemophilia treatment centers (HTC) in the USA.

OBJECTIVES

The aims were to identify and compare tools and resources used, areas of unmet needs, and to discuss implications for nurses in practice.

METHODS

An anonymous electronic survey was distributed to 574 HTC nurses; 156 responses were analyzed.

RESULTS

The data demonstrated that nurses, more specifically nurse coordinators, were most responsible for teaching HI. However, many nurses lack the knowledge and confidence to do so: 23.0% responded feeling somewhat or not very confident with teaching. Of those 36.4% were staff nurses, 11.9% nurse coordinators, and 41.7% advanced practice registered nurses. The majority of nurses have worked more than 5 years as a nurse, with a mean length of time of 23.7 years (SD=11.12, range 3-47) and a mean of 12.9 years (SD=10.29, range 1-42) in a HTC. Thirty-eight and a half percent of nurses have worked less than 5 years in a HTC. Most nurses appeared to follow the Infusion Nurses Society standards when performing venipunctures. Many centers reported using a formal tool or curriculum to teach HI. Nonetheless, these curricula are not uniform and their use is inconsistent between centers and regions.

CONCLUSION

There are currently no national guidelines or standards to assist nurses in this task. The data confirmed the need to develop guidelines and a standardized curriculum to teach HI.

Safety and efficacy of BAY 94-9027, a prolonged-half-life factor VIII

Essentials Recombinant factor VIII BAY 94-9027 conjugates in a site-specific manner with polyethylene glycol. BAY 94-9027 was given to patients with severe hemophilia A as prophylaxis and to treat bleeds. BAY 94-9027 prevented bleeds at dose intervals up to every 7 days and effectively treated bleeds. BAY 94-9027 treatment was mainly well tolerated and no patient developed factor VIII inhibitors. Click to hear Dr Tiede's perspective on half-life extended factor VIII for the treatment of hemophilia A SUMMARY: Background BAY 94-9027 is a B-domain-deleted prolonged-half-life recombinant factor VIII (FVIII) that conjugates in a site-specific manner with polyethylene glycol. Objective Assess efficacy and safety of BAY 94-9027 for prophylaxis and treatment of bleeds in patients with severe hemophilia A. Patients/methods In this multinational, phase 2/3, partially randomized, open-label trial, men aged 12-65 years with FVIII < 1% and ≥ 150 exposure days to FVIII received BAY 94-9027 for 36 weeks on demand or prophylactically at intervals determined following a 10-week run-in period on 25 IU kg-1 body weight two times per week. Patients with > 1 bleed during the run-in subsequently received 30-40 IU kg-1 two times per week; patients with ≤ 1 bleed were eligible for randomization to every-5-days (45-60 IU kg-1 ) or every-7-days (60 IU kg-1 ) prophylaxis (1 : 1) for 26 additional weeks until randomization arms were filled. Patients who were eligible but not randomized continued twice-weekly prophylaxis. The primary efficacy outcome was annualized bleeding rate (ABR). Results The intent-to-treat population included 132 patients (prophylaxis, n = 112; on demand, n = 20). Median ABR (quartile [Q1; Q3]) for patients treated two times per week who were not eligible for randomization (n = 13) improved after dose increase (17.4 [14.3; 26.0] to 4.1 [2.0; 10.6]). Median ABR for patients randomized to every-5-days treatment (n = 43) was 1.9 (0; 4.2), similar to patients eligible for randomization but who continued treatment two times per week (n = 11). Median ABR for 32/43 patients (74%) who continued every-7-days prophylaxis until study end was 0.96 (0.0; 4.3). Six hundred and thirty-six of 702 bleeds (90.6%) were controlled with ≤ 2 infusions. No patient developed a FVIII inhibitor. Conclusions BAY 94-9027 prevented bleeding across three individually tailored dose regimens and was effective for treatment of bleeds.

Partnering to change the world for people with haemophilia: 6(th) Haemophilia Global Summit, Prague, Czech Republic, 24-26(th) September 2015

The 6(th) Haemophilia Global Summit was held in Prague, Czech Republic, in September 2015. The programme was designed by an independent Scientific Steering Committee of haemophilia experts and aimed to share optimal management strategies for haemophilia at all life stages, explore recent potential advances in the management of haemophilia A and B and discuss challenges in haemophilia care. In this supplement from the meeting, Dan Hart reviews the lessons that can be learnt from cost-constrained environments with regard to improving care for people with haemophilia globally. Sébastien Lobet discusses the importance of physical activity for optimising care and Roseline d'Oiron and Jan Blatný consider the role of real-world data in understanding the effect of treatment in a clinical setting over the long term and the true impact of treatment on the day-to-day life of the patient. Gili Kenet addresses the current challenges relating to the optimal management of prophylaxis, and Gerry Dolan and Cedric Hermans discuss the value of pharmacokinetic (PK) parameters in informing treatment decisions. Cedric Hermans and Valérie Libotte explore the importance of considering social and occupational development factors as an integral part of haemophilia care, and Jan Astermark reviews key strategies to predict and prevent inhibitor development.

The Efficacy of Recombinant FVIII Low-Dose Prophylaxis in Chinese Pediatric Patients With Severe Hemophilia A: A Retrospective Analysis From the ReCARE Study

Objective:

This study explores the efficacy of recombinant factor VIII (rFVIII) low-dose prophylaxis in Chinese pediatric patients with severe hemophilia A from the Retrospective Study in Chinese Pediatric Hemophilia A Patients With rFVIII Contained Regular Prophylaxis (ReCARE) population.

Methods:

This is additional analysis of the multicenter, retrospective ReCARE study, in which the annual bleeding rate (ABR), annual joint bleeding rate (AJBR), and safety of >12-week, low dose (10-30 IU/kg/wk) rFVIII prophylaxis divided into primary, secondary, and tertiary groups based on the joint status and joint bleeding history were analyzed.

Results:

A total of 57 patients (median age: 8.2 [0.4-17.3] years) from the ReCARE study receiving primary (n = 3), secondary (n = 21), and tertiary (n = 33) prophylaxes were included. Low-dose prophylaxis had significant bleeding reduction in all 3 groups compared to the baseline ( S = 408.5, P < .001), with median ABR rates of −4.0 (−8.0 to −3.1), −4.0 (−24.0 to 8.0), and −13.9 (−110.6 to 20.6) in the primary, secondary, and tertiary groups, respectively, with a significant difference between the secondary and tertiary groups ( P = .008). Median AJBR reduction rates were −2.3 (−6.3 to 8.4) and −14.9 (−61.5 to 19.1) in the secondary and tertiary groups, respectively. But there was no significant difference in AJBRs between the secondary and tertiary groups ( P = .061), which was related to damaged joint status. Hence, longer prophylaxis was associated with better prevention of joint bleeding ( P = .024).

Conclusion:

Despite significant ABR/AJBR reduction in all 3 groups, the efficacy of the primary prophylaxis was better than the secondary and tertiary prophylaxes.

New therapies for hemophilia

Individuals with severe hemophilia have benefitted from 5 decades of advances that have led to widespread availability of safe and efficacious factors VIII and IX, a multidisciplinary integrated care model through a network of specialized hemophilia treatment centers, and aggressive introduction of prophylactic replacement therapy to prevent bleeding and preserve joint health. Yet, there are remaining challenges and treatment gaps which have prevented complete abrogation of all joint bleeding, and progressive joint deterioration may continue in some affected individuals over the course of a lifetime. Some of these challenges can now be addressed with recombinant clotting factors with extended half-life that may improve adherence to prophylaxis regimens through more convenient infusion schedules, maintain higher plasma levels for longer when clinically necessary, and allow for better adaptation to individual phenotypic and pharmacokinetic variability. Real-world case studies will be presented that illustrate practical application of these newly approved therapies in clinical practice and the clinical trial data that have demonstrated the potential for improved clinical outcomes by implementing these strategies.

Individualized prophylaxis for optimizing hemophilia care: can we apply this to both developed and developing nations?

Prophylaxis is considered optimal care for hemophilia patients to prevent bleeding and to preserve joint function thereby improving quality of life (QoL). The evidence for prophylaxis is irrefutable and is the standard of care in developed nations. Prophylaxis can be further individualized to improve outcomes and cost effectiveness. Individualization is best accomplished taking into account the bleeding phenotype, physical activity/lifestyle, joint status, and pharmacokinetic handling of specific clotting factor concentrates, all of which vary among individuals. Patient acceptance should also be considered. Assessment tools (e.g. joint status imaging and function studies/scores, QoL) for determining and monitoring risk factors and outcome, as well as population PK profiling have been developed to assist the individualization process. The determinants of optimal prophylaxis include (1) factor dose/dosing frequency, hence, cost/affordability (2) bleeding triggers (physical activity/lifestyle, chronic arthropathy and synovitis) and (3) bleeding rates. Altering one determinant results in adjustment of the other two. Thus, the trough level to protect from spontaneous bleeding can be increased in patients who have greater bleeding risks; and prophylaxis to achieve zero joint bleeds is achievable through optimal individualization. Prophylaxis in economically constrained nations is limited by the ill-affordability of clotting factor concentrates. However, at least 5 studies on children and adults from Thailand, China and India have shown superiority of low dose (~5–10 IU kg⁻¹ 2-3× per week) prophylaxis over episodic treatment in terms of bleed reduction, and quality of life, with improved physical activity, independent functioning, school attendance and community participation. In these nations, the prophylaxis goals should be for improved QoL rather than “zero bleeds” and perfect joints. Prophylaxis can still be individualized to affordability. Higher protective trough level can be achieved by using smaller doses given more frequently without an increase in consumption/cost. The bleeding trigger can also be down-regulated by avoiding unnecessary injury, and by engaging in judicious strengthening exercises appropriate to the joint status to improve balance and joint stabilization. Central to the success of prophylaxis are clinics with comprehensive care that provide the necessary professional expertise, support, and counseling, to educate patients, families, and other healthcare professionals, and to support research for improved hemophilia care.

The use of pharmacokinetics in dose individualization of factor VIII in the treatment of hemophilia A

INTRODUCTION

Hemophilia A is a bleeding disorder resulting from a lack of clotting factor VIII (FVIII), and treatment typically consists of prophylactic replacement of the deficient factor. However, high between subject variability precludes the development of a 'one size fits all' dosing strategy and necessitates an individualized approach. We sought to summarize the data on the pharmacokinetics of FVIII available as a basis for the development of population pharmacokinetic models to be used in dose tailoring. Areas covered: We reviewed the pharmacokinetics of FVIII as used for the treatment of hemophilia A, with a focus on the variability observed between patients and the application of pharmacokinetic methods to dose individualization. We also explored the covariates affecting pharmacokinetic parameters, the differences between plasma-derived and recombinant FVIII and the development of extended half-life products. Expert opinion: The pharmacokinetics of factor VIII in patients with hemophilia shows a high interpatient variability, and is affected by age, weight, level of von Willebrand factor, and blood group. A population approach to estimating individual pharmacokinetics is likely to provide the most successful strategy to tailor factor concentrate dosing to the individual needs and to ensure optimal patient outcomes, while also improving the cost-effectiveness of prophylactic replacement therapy.

The F8(-/-) rat as a model of hemophilic arthropathy

Essentials Validating the F8 rat as a new intermediate-size animal model of hemophilic arthropathy. Factor VIII (FVIII) treated F8(-/-) rats suffered induced hemarthrosis analyzed by histopathology. F8 (-/-) animals develop hemophilic arthropathy upon hemarthrosis, preventable by FVIII treatment. The F8 (-/-) rat presents as a new pharmacologic model of hemophilic arthropathy.

SUMMARY

Background Translational animal models of hemophilia are valuable for determining the pathobiology of the disease and its co-morbidities (e.g. hemophilic arthropathy, HA). The biologic mechanisms behind the development of HA, a painful and debilitating condition, are not completely understood. We recently characterized a F8(-/-) rat, which could be a new preclinical model of HA. Objectives To establish the F8(-/-) rat as a model of HA by determining if the F8(-/-) rat develops HA resembling human HA after an induced joint bleed and whether a second joint bleed causes further disease progression. Methods Wild-type and F8(-/-) rats were treated with vehicle or recombinant human factor VIII (rhFVIII) prior to a needle-induced joint bleed. Joint swelling was measured prior to injury, the following 7 days and upon euthanasia. Histologic sections of the joint were stained, and athropathic changes identified and scored with regard to synovitis, bone remodelling, cartilage degradation and hemosiderin deposition. Results Vehicle-treated F8(-/-) rats experienced marked joint swelling and developed chronic degenerative joint changes (i.e. fibrosis of the subsynovial membrane, chondrocyte loss and excessive bone remodeling). Treatment with rhFVIII reduced or prevented swelling and degenerative joint changes, returning the F8(-/-) animals to a wild-type phenotype. Conclusion The hemophilic phenotype of the F8(-/-) rat resulted in a persistent hemarthrosis following an induced joint bleed. This caused development of HA resembling human HA, which was prevented by rhFVIII treatment, confirming the potential of the F8(-/-) rat as a model of HA.

An innovative outcome-based care and procurement model of hemophilia management

Hemophilia is a rare bleeding disorder associated with spontaneous and post-traumatic bleeding. Each hemophilia patient requires a personalized approach to episodic or prophylactic treatment, but self-management can be challenging for patients, and avoidable bleeding may occur. Patient-tailored care may provide more effective prevention of bleeding, which in turn, may decrease the likelihood of arthropathy and associated chronic pain, missed time from school or work, and progressive loss of mobility. A strategy is presented here aiming to reduce or eliminate bleeding altogether through a holistic approach based on individual patient characteristics. In an environment of budget constraints, this approach would link procurement to patient outcome, adding incentives for all stakeholders to strive for optimal care and, ultimately, a bleed-free world.

Successful Phenotype Improvement following Gene Therapy for Severe Hemophilia A in Privately Owned Dogs

Severe hemophilia A (HA) is an inherited bleeding disorder characterized by <1% of residual factor VIII (FVIII) clotting activity. The disease affects several mammals including dogs, and, like humans, is associated with high morbidity and mortality. In gene therapy using adeno-associated viral (AAV) vectors, the canine model has been one of the best predictors of the therapeutic dose tested in clinical trials for hemophilia B (factor IX deficiency) and other genetic diseases, such as congenital blindness. Here we report our experience with liver gene therapy with AAV-FVIII in two outbred, privately owned dogs with severe HA that resulted in sustained expression of 1–2% of normal FVIII levels and prevented 90% of expected bleeding episodes. A Thr62Met mutation in the F8 gene was identified in one dog. These data recapitulate the improvement of the disease phenotype in research animals, and in humans, with AAV liver gene therapy for hemophilia B. Our experience is a novel example of the benefits of a relevant preclinical canine model to facilitate both translational studies in humans and improved welfare of privately owned dogs.

Pharmacokinetics and pharmacodynamics of SCT800, a new recombinant FVIII, in hemophilia A mice

AIM

SCT800 is a new third-generation recombinant FVIII agent that is undergoing promising preclinical study. This study aimed to investigate the pharmacokinetic and pharmacodynamic profiles of SCT800 in hemophilia A mice.

METHODS

After hemophilia A mice were intravenously injected with single dose of SCT800 (80, 180, and 280 IU/kg) or the commercially available product Xyntha (280 IU/kg), pharmacokinetics profiles were evaluated based on measuring plasma

FVIII

C. For pharmacodynamics study, dose-response curves of SCT800 and Xyntha (1-200 IU/kg) were constructed using a tail bleeding model monitoring both bleeding time and blood loss.

RESULTS

Pharmacokinetics profile analysis showed a dose independency of SCT800 ranging from 80 to 280 IU/kg and comparable pharmacokinetic profiles between SCT800 and Xyntha at the doses tested. Pharmacodynamics study revealed comparable ED50 values of SCT800 and Xyntha in the tail bleeding model: 14.78 and 15.81 IU/kg for bleeding time, respectively; 13.50 and 13.58 IU/kg for blood loss, respectively. Moreover, at the doses tested, the accompanying dose-related safety evaluation in the tail bleeding model showed lower hypercoagulable tendency and wider dosage range potential for SCT800 than Xyntha.

CONCLUSION

In hemophilia A mice, SCT800 shows comparable pharmacokinetics and pharmacodynamics to Xyntha at the doses tested, and possibly with better safety properties.

Donor antigen-primed regulatory T cells permit liver regeneration and phenotype correction in hemophilia A mouse by allogeneic bone marrow stem cells

INTRODUCTION

Cell replacement therapy may be considered as an alternate approach to provide therapeutic dose of plasma factor VIII (FVIII) in patients with hemophilia A (HA). However, immune rejection limits the use of allogeneic cells in this mode of therapy. Here, we have examined the role of donor major histocompatibility complex (MHC)-stimulated host CD4(+)CD25(+) regulatory T (Treg) cells in suppressing immune responses against allogeneic uncommitted (Lin(-)) bone marrow cells (BMCs) for correction of bleeding disorder in HA mice.

METHODS

Allogeneic donor Lin(-) BMCs were co-transplanted with allo-antigen sensitized Treg cells in HA mice having acetaminophen-induced acute liver injury. Plasma FVIII activity was determined by in vitro functional assay, and correction of bleeding phenotype was assessed on the basis of capillary blood clotting time and tail-clip challenge. The immunosuppression potential of the sensitized Treg cells on CD4(+) T cells was studied both in vitro and in vivo. Suppression of inflammatory reactions in the liver against the homed donor cells by sensitized Treg cells was analysed by histopathological scoring. Allo-specificity of sensitized Treg cells and long-term retention of immunosuppression were examined against a third-party donor and by secondary challenge of allogeneic donor cells, respectively. The engraftment and phenotype change of donor BMCs in the liver and their role in synthesis of FVIII and liver regeneration were also determined.

RESULTS

Co-transplantation of allogeneic Lin(-) BMCs with sensitized Treg cells led to systemic immune modulation and suppression of inflammatory reactions in the liver, allowing better engraftment of allogeneic cells in the liver. Allo-antigen priming led to allo-specific immune suppression even after 1 year of transplantation. Donor-derived endothelial cells expressed FVIII in HA mice, leading to the correction of bleeding phenotype. Donor-derived hepatocyte-like cells, which constitute the major fraction of engrafted cells, supported regeneration of the liver after acute injury.

CONCLUSIONS

A highly proficient FVIII secreting core system can be created in regenerating liver by transplanting allogeneic Lin(-) BMCs in HA mice where transplantation tolerance against donor antigens can be induced by in vitro allo-antigen primed Treg cells. This strategy can be beneficial in treatment of genetic liver disorders for achieving prophylactic levels of the missing proteins.