Savita Rangarajan

Adenovirus-Associated Virus Vector-Mediated Gene Transfer in Hemophilia B

BACKGROUND Hemophilia B, an X-linked disorder, is ideally suited for gene therapy. We investigated the use of a new gene therapy in patients with the disorder. METHODS We infused a single dose of a serotype-8-pseudotyped, self-complementary adenovirus-associated virus (AAV) vector expressing a codon-optimized human factor IX (FIX) transgene (scAAV2/8-LP1-hFIXco) in a peripheral vein in six patients with severe hemophilia B (FIX activity, <1% of normal values). Study participants were enrolled sequentially in one of three cohorts (given a high, intermediate, or low dose of vector), with two participants in each group. Vector was administered without immunosuppressive therapy, and participants were followed for 6 to 16 months. RESULTS AAV-mediated expression of FIX at 2 to 11% of normal levels was observed in all participants. Four of the six discontinued FIX prophylaxis and remained free of spontaneous hemorrhage; in the other two, the interval between prophylactic injections was increased. Of the two participants who received the high dose of vector, one had a transient, asymptomatic elevation of serum aminotransferase levels, which was associated with the detection of AAV8-capsid-specific T cells in the peripheral blood; the other had a slight increase in liver-enzyme levels, the cause of which was less clear. Each of these two participants received a short course of glucocorticoid therapy, which rapidly normalized aminotransferase levels and maintained FIX levels in the range of 3 to 11% of normal values. CONCLUSIONS Peripheral-vein infusion of scAAV2/8-LP1-hFIXco resulted in FIX transgene expression at levels sufficient to improve the bleeding phenotype, with few side effects. Although immune-mediated clearance of AAV-transduced hepatocytes remains a concern, this process may be controlled with a short course of glucocorticoids without loss of transgene expression. (Funded by the Medical Research Council and others; ClinicalTrials.gov number, NCT00979238.).

Long-Term Safety and Efficacy of Factor IX Gene Therapy in Hemophilia B

BACKGROUND In patients with severe hemophilia B, gene therapy that is mediated by a novel self-complementary adeno-associated virus serotype 8 (AAV8) vector has been shown to raise factor IX levels for periods of up to 16 months. We wanted to determine the durability of transgene expression, the vector dose-response relationship, and the level of persistent or late toxicity. METHODS We evaluated the stability of transgene expression and long-term safety in 10 patients with severe hemophilia B: 6 patients who had been enrolled in an initial phase 1 dose-escalation trial, with 2 patients each receiving a low, intermediate, or high dose, and 4 additional patients who received the high dose (2×10(12) vector genomes per kilogram of body weight). The patients subsequently underwent extensive clinical and laboratory monitoring. RESULTS A single intravenous infusion of vector in all 10 patients with severe hemophilia B resulted in a dose-dependent increase in circulating factor IX to a level that was 1 to 6% of the normal value over a median period of 3.2 years, with observation ongoing. In the high-dose group, a consistent increase in the factor IX level to a mean (±SD) of 5.1±1.7% was observed in all 6 patients, which resulted in a reduction of more than 90% in both bleeding episodes and the use of prophylactic factor IX concentrate. A transient increase in the mean alanine aminotransferase level to 86 IU per liter (range, 36 to 202) occurred between week 7 and week 10 in 4 of the 6 patients in the high-dose group but resolved over a median of 5 days (range, 2 to 35) after prednisolone treatment. CONCLUSIONS In 10 patients with severe hemophilia B, the infusion of a single dose of AAV8 vector resulted in long-term therapeutic factor IX expression associated with clinical improvement. With a follow-up period of up to 3 years, no late toxic effects from the therapy were reported. (Funded by the National Heart, Lung, and Blood Institute and others; ClinicalTrials.gov number, NCT00979238.).

Diagnosis and treatment of factor VIII and IX inhibitors in congenital haemophilia: (4th edition)

Peter W. Collins, Elizabeth Chalmers, Daniel P. Hart, Ri Liesner, Savita Rangarajan, Kate Talks, Mike Williams and Charles R. Hay School of Medicine, Cardiff University, University Hospital of Wales, Wales, Royal Hospital for Sick Children, Glasgow, The London School of Medicine and Dentistry, Royal London Hospital, Barts, Queen Mary University, London, Great Ormond Street NHS Trust, London, Hampshire Hospital NHS Foundation Trust, Basingstoke & North Hampshire Hospital, Basingstoke, Royal Victoria Infirmary, Newcastle upon Tyne, Birmingham Childrens’ Hospital NHS Foundation Trust, Birmingham and Central Manchester University Hospitals, Manchester, UK

Fibrinogen estimates are influenced by methods of measurement and hemodilution with colloid plasma expanders

BACKGROUND: Measurement of plasma fibrinogen is often required in critically ill patients or massively bleeding patients being resuscitated with colloid plasma expander. This study aimed at evaluating different assays of plasma fibrinogen after in vitro dilution with commonly used plasma expanders and challenged the hypothesis that levels of fibrinogen are estimated significantly higher in plasma diluted with colloid plasma expander compared with isotonic saline.

Factor VIII brand and the incidence of factor VIII inhibitors in previously untreated UK children with severe hemophilia A, 2000-2011.

The effect of recombinant factor VIII (rFVIII) brand on inhibitor development was investigated in all 407 severe hemophilia A previously untreated patients born in the United Kingdom (UK) between 1 January 2000 and 31 December 2011. Eighty-eight (22%) had been in the RODIN study. Information was extracted from the National Haemophilia Database. Because exposure days (EDs) were not known for some patients, time from first treatment was used as a surrogate for rFVIII exposure. An inhibitor developed in 118 (29%) patients, 60 high and 58 low titer, after a median (interquartile range) of 7.8 (3.3-13.5) months from first exposure and 16 (9-30) EDs. Of 128 patients treated with Kogenate Bayer/Helixate NexGen, 45 (35.2%, 95% confidence interval [CI] 27.4-43.8) developed an inhibitor compared with 42/172 (24.4%, 95% CI 18.6% to 31.4%) with Advate (P = .04). The adjusted hazard ratio (HR) (95% CI) for Kogenate Bayer/Helixate NexGen compared with Advate was 2.14 (1.12-4.10) (P = .02) for high titer and 1.75 (1.11-2.76) (P = .02) for all inhibitors. When excluding UK-RODIN patients, the adjusted HR (95% CI) for high-titer inhibitors was 2.00 (0.93-4.34) (P = .08). ReFacto AF was associated with a higher incidence of all, but not high-titer, inhibitors than Advate. These results will help inform debate around the relative immunogenicity and use of rFVIII brands.

AAV5–Factor VIII Gene Transfer in Severe Hemophilia A

Background Patients with hemophilia A rely on exogenous factor VIII to prevent bleeding in joints, soft tissue, and the central nervous system. Although successful gene transfer has been reported in patients with hemophilia B, the large size of the factor VIII coding region has precluded improved outcomes with gene therapy in patients with hemophilia A. Methods We infused a single intravenous dose of a codon‐optimized adeno‐associated virus serotype 5 (AAV5) vector encoding a B‐domain–deleted human factor VIII (AAV5‐hFVIII‐SQ) in nine men with severe hemophilia A. Participants were enrolled sequentially into one of three dose cohorts (low dose [one participant], intermediate dose [one participant], and high dose [seven participants]) and were followed through 52 weeks. Results Factor VIII activity levels remained at 3 IU or less per deciliter in the recipients of the low or intermediate dose. In the high‐dose cohort, the factor VIII activity level was more than 5 IU per deciliter between weeks 2 and 9 after gene transfer in all seven participants, and the level in six participants increased to a normal value (>50 IU per deciliter) that was maintained at 1 year after receipt of the dose. In the high‐dose cohort, the median annualized bleeding rate among participants who had previously received prophylactic therapy decreased from 16 events before the study to 1 event after gene transfer, and factor VIII use for participant‐reported bleeding ceased in all the participants in this cohort by week 22. The primary adverse event was an elevation in the serum alanine aminotransferase level to 1.5 times the upper limit of the normal range or less. Progression of preexisting chronic arthropathy in one participant was the only serious adverse event. No neutralizing antibodies to factor VIII were detected. Conclusions The infusion of AAV5‐hFVIII‐SQ was associated with the sustained normalization of factor VIII activity level over a period of 1 year in six of seven participants who received a high dose, with stabilization of hemostasis and a profound reduction in factor VIII use in all seven participants. In this small study, no safety events were noted, but no safety conclusions can be drawn. (Funded by BioMarin Pharmaceutical; ClinicalTrials.gov number, NCT02576795; EudraCT number, 2014‐003880‐38.)

Targeting of Antithrombin in Hemophilia A or B with RNAi Therapy

Background Current hemophilia treatment involves frequent intravenous infusions of clotting factors, which is associated with variable hemostatic protection, a high treatment burden, and a risk of the development of inhibitory alloantibodies. Fitusiran, an investigational RNA interference (RNAi) therapy that targets antithrombin (encoded by SERPINC1), is in development to address these and other limitations. Methods In this phase 1 dose‐escalation study, we enrolled 4 healthy volunteers and 25 participants with moderate or severe hemophilia A or B who did not have inhibitory alloantibodies. Healthy volunteers received a single subcutaneous injection of fitusiran (at a dose of 0.03 mg per kilogram of body weight) or placebo. The participants with hemophilia received three injections of fitusiran administered either once weekly (at a dose of 0.015, 0.045, or 0.075 mg per kilogram) or once monthly (at a dose of 0.225, 0.45, 0.9, or 1.8 mg per kilogram or a fixed dose of 80 mg). The study objectives were to assess the pharmacokinetic and pharmacodynamic characteristics and safety of fitusiran. Results No thromboembolic events were observed during the study. The most common adverse events were mild injection‐site reactions. Plasma levels of fitusiran increased in a dose‐dependent manner and showed no accumulation with repeated administration. The monthly regimen induced a dose‐dependent mean maximum antithrombin reduction of 70 to 89% from baseline. A reduction in the antithrombin level of more than 75% from baseline resulted in median peak thrombin values at the lower end of the range observed in healthy participants. Conclusions Once‐monthly subcutaneous administration of fitusiran resulted in dose‐dependent lowering of the antithrombin level and increased thrombin generation in participants with hemophilia A or B who did not have inhibitory alloantibodies. (Funded by Alnylam Pharmaceuticals; ClinicalTrials.gov number, NCT02035605.)

Recombinant factor VIIa analog in the management of hemophilia with inhibitors: results from a multicenter, randomized, controlled trial of vatreptacog alfa

Vatreptacog alfa, a recombinant factor VIIa (rFVIIa) analog with three amino acid substitutions and 99% identity to native FVIIa, was developed to improve the treatment of hemophilic patients with inhibitors.

Diagnosis and management of acquired coagulation inhibitors: a guideline from UKHCDO

A United Kingdom Haemophilia Centre Doctors’ Organization (UKHCDO) guideline approved by the British Committee for Standards in Haematology Peter W Collins, Elizabeth Chalmers, Daniel Hart, Ian Jennings, Ri Liesner, Savita Rangarajan, Kate Talks, Michael Williams and Charles R. M. Hay School of Medicine, Cardiff University, University Hospital of Wales, Cardiff, Royal Hospital for Sick Children, Glasgow, Royal London Hospital, Barts and The London School of Medicine and Dentistry, Queen Mary University London, London, UK NEQAS Blood Coagulation, Sheffield, Great Ormond Street NHS Trust, London, Hampshire Hospital NHS Foundation Trust, Basingstoke & North Hampshire Hospital, Basingstoke, Newcastle upon Tyne Hospital NHS Foundation Trust, Newcastle, Birmingham Children’s Hospital NHS Foundation Trust, Birmingham, and Manchester University Dept of Haematology, Manchester Royal Infirmary, Manchester, UK

Experience of four UK comprehensive care centres using FEIBA® for surgeries in patients with inhibitors

Summary.  Increasing evidence indicates that factor VIII (FVIII) inhibitor bypassing agents (FEIBA® and NovoSeven®) can provide effective peri‐operative haemostasis in haemophilia patients with high‐responding inhibitors. We report the collected experience of all major and minor surgeries, conducted between December 1998 and September 2008, at four UK haemophilia Comprehensive Care Centres with FEIBA® as the first‐line bypassing agent in patients with inhibitors. A total of 26 surgical procedures were performed in 18 patients of ages 34–83 years including five patients with acquired FVIII inhibitors. A single pre‐operative infusion of FEIBA was followed by 6–12 h interval dosing for major surgeries at the discretion of the physician to approximate a maximum of 200 U kg−1 day−1, with tapering when postoperative haemostasis and wound healing permitted. Haemostatic outcomes were retrospectively reviewed against European consensus thresholds for blood loss and duration of treatment compared with expectations for equivalent procedures in non‐inhibitor patients. Peri‐operative haemostatic outcome with FEIBA was rated excellent or good in 78% of 18 major surgeries in 12 patients, including 11 major orthopaedic procedures. Haemostatic outcome was rated excellent in all seven procedures in five patients with acquired FVIII inhibitors and in all eight minor surgical procedures in six patients. FEIBA was well tolerated with no intra‐operative haemostatic complications. A single, transient postoperative thrombotic adverse event occurred in a patient with cerebrovascular disease. This case series adds significantly to existing evidence that FEIBA can provide adequate, well‐tolerated, peri‐operative haemostatic cover for a wide variety of major and minor surgical procedures.