Michael Recht

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.).

Interferon-gamma expression by Th1 effector T cells mediated by the p38 MAP kinase signaling pathway.

Signal transduction via MAP kinase pathways plays a key role in a variety of cellular responses, including growth factor‐induced proliferation, differentiation and cell death. In mammalian cells, p38 MAP kinase can be activated by multiple stimuli, such as pro‐inflammatory cytokines and environmental stress. Although p38 MAP kinase is implicated in the control of inflammatory responses, the molecular mechanisms remain unclear. Upon activation, CD4+ T cells differentiate into Th2 cells, which potentiate the humoral immune response or pro‐inflammatory Th1 cells. Here, we show that pyridinyl imidazole compounds (specific inhibitors of p38 MAP kinase) block the production of interferon‐γ (IFNγ) by Th1 cells without affecting IL‐4 production by Th2 cells. These drugs also inhibit transcription driven by the IFNγ promoter. In transgenic mice, inhibition of the p38 MAP kinase pathway by the expression of dominant‐negative p38 MAP kinase results in selective impairment of Th1 responses. In contrast, activation of the p38 MAP kinase pathway by the expression of constitutivelyactivated MAP kinase kinase 6 in transgenic mice caused increased production of IFNγ during the differentiation and activation of Th1 cells. Together, these data demonstrate that the p38 MAP kinase is relevant for Th1 cells, not Th2 cells, and that inhibition of p38 MAP kinase represents a possible site of therapeutic intervention in diseases where a predominant Th1 immune response leads to a pathological outcome. Moreover, our study provides an additional mechanism by which the p38 MAP kinase pathway controls inflammatory responses.

Plasma and albumin-free recombinant factor VIII: pharmacokinetics, efficacy and safety in previously treated pediatric patients.

Summary.  Background: The pharmacokinetics of factor VIII replacement therapy in preschool previously treated patients (PTPs) with hemophilia A have not been well characterized. Objectives: To assess the pharmacokinetics, efficacy and safety of a plasma‐free recombinant FVIII concentrate, ADVATE [Antihemophilic Factor (Recombinant), Plasma/Albumin‐Free Method, rAHF‐PFM], in children < 6 years of age with severe hemophilia. Patients/methods: Fifty‐two boys, one girl, mean (± SD) age 3.1 ± 1.5 years and ≥ 50 days of prior FVIII exposure, were enrolled in a prospective study of ADVATE rAHF‐PFM at 23 centers. Results: The mean terminal phase half‐life (t1/2) was 9.88 ± 1.89 h, and the mean adjusted in vivo recovery (IVR) was 1.90 ± 0.43 IU dL−1 (IU kg−1)−1. Over the 1–6‐year age range, t1/2 of rAHF‐PFM increased by 0.40 h year−1. IVR increased by 0.095IU dL−1(IU kg−1)−1 (kg m−2)−1 in relation to body mass index (BMI). Patients primarily received prophylaxis. Median (range) annual joint bleeds were 0.0 (0.0–5.8), 0.0 (0.0–6.1) and 14.2 (0.0–34.5) for standard prophylaxis, modified prophylaxis and on‐demand treatment, respectively. Bleeds were managed in 90% (319/354) of episodes with one or two rAHF‐PFM infusions; response was rated excellent/good in 93.8% of episodes. Over a median 156 exposure days, no FVIII inhibitors were detected and no related severe adverse events or unusual non‐serious adverse events were seen. Conclusions: Children < 6 years of age appear to have shorter FVIII t1/2 and lower IVR values than older subjects. However, these parameters increased with age (t1/2) and BMI (adjusted IVR), respectively. rAHF‐PFM was clinically effective and well tolerated, with no signs of increased immunogenicity in previously treated young children with hemophilia A.

Variable response to propranolol treatment of kaposiform hemangioendothelioma, tufted angioma, and Kasabach-Merritt phenomenon

Propranolol is a non‐selective beta‐adrenergic antagonist successfully used in a case of kaposiform hemangioendothelioma (KHE) associated with Kasabach–Merritt phenomenon (KMP). We report 11 patients treated with propranolol for KHE and the related variant tufted angioma (TA), six of whom also had KMP. The varied responses to treatment, with only 36% responding in our series, demonstrate the need for further study of this medication before routine use for these indications. Pediatr Blood Cancer 2012; 59: 934–938.

Clinical evaluation of moroctocog alfa (AF-CC), a new generation of B-domain deleted recombinant factor VIII (BDDrFVIII) for treatment of haemophilia A: demonstration of safety, efficacy, and pharmacokinetic equivalence to full-length recombinant factor VIII

Summary.  BDDrFVIII is a B‐domain deleted recombinant factor VIII (rFVIII) product for haemophilia A. Manufacture uniquely includes purification chromatography by synthetic‐affinity ligand rather than murine‐based monoclonal antibody, as well as an albumin‐free cell culture process. BDDrFVIII was studied in 204 patients, including 62 subjects <16 years old, in two studies. A double‐blind, randomized, pharmacokinetic (PK) crossover study, utilizing a central laboratory assay (one‐stage (OS)) for both drug potency assignment and plasma FVIII‐activity measurements, demonstrated that BDDrFVIII was PK‐equivalent to a full‐length rFVIII. Favourable efficacy and safety were observed: during defined routine prophylaxis in a patient population significant for preexisting target joints, nearly half (45.7%) of patients had no bleeding, and a low‐annualized bleed rate (ABR) was achieved (median 1.9); 92.5% of haemorrhages (n = 187) required ≤2 infusions. Three subjects (1.5%, across both studies) developed de novo inhibitors (low‐titre, transient), and the primary safety endpoint, based on a prospective Bayesian analysis, demonstrated the absence of neoantigenicity for BDDrFVIII. The PK‐equivalence, based on central testing to align test and reference articles, and the novel Bayesian analysis of inhibitor safety in these investigations reflect robust experimental designs with relevance to future studies. This extensive dataset demonstrates the safety and efficacy of BDDrFVIII for haemophilia A.

Results from a large multinational clinical trial (guardian™1) using prophylactic treatment with turoctocog alfa in adolescent and adult patients with severe haemophilia A: Safety and efficacy

Recombinant factor VIII (rFVIII) products provide a safe and efficacious replacement therapy for prophylaxis and treatment of bleeding episodes in patients with severe haemophilia A. This multinational, open‐label, non‐controlled trial investigated the safety and efficacy of turoctocog alfa, a new rFVIII product. The primary objective was to evaluate safety. A total of 150 patients (24 adolescents and 126 adults) with severe haemophilia A (FVIII activity ≤1%), with at least 150 exposure days (EDs) to any FVIII product and no history of inhibitors were enrolled, and 146 patients (97%) completed the trial. All patients received prophylaxis with turoctocog alfa for approximately 6 months and had a mean of 85 EDs during the trial. None of the patients developed FVIII inhibitors, there were no indications of early FVIII inhibitor development and no safety concerns were identified. A total of 225 adverse events were reported in 100 (67%) patients, with the most common being events associated with dosing procedures, headaches, and nasopharyngitis. A total of 499 bleeding episodes were reported during the trial, the majority (89%) were controlled with 1–2 infusions of turoctocog alfa. Based on patient reports, the success rate (defined as ‘excellent’ or ‘good’ haemostatic response) for treatment of bleeding episodes was 81%. The overall median annualized bleeding rate was 3.7 (interquartile range: 8.7) bleeds/patient/year. In conclusion, turoctocog alfa provides a new, safe and effective alternative for prophylaxis and treatment of bleeding episodes in patients with haemophilia A.

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.

A retrospective study to describe the incidence of moderate to severe allergic reactions to factor IX in subjects with haemophilia B

Summary.  Using a patient chart review process, we conducted a retrospective study to describe the frequency of allergic reactions in individuals with haemophilia B receiving factor IX (FIX) replacement therapy. The number of allergic reactions in individuals receiving a recombinant FIX (rFIX) product (BeneFix®) was then compared with the number of reactions in patients receiving plasma‐derived FIX (pdFIX) products. Of the 180 subjects in the study, 163 received rFIX, 88 received pdFIX; 71 received both product types. A total of seven (3.89%) subjects had a moderate or severe allergic reaction to a FIX product (95% confidence interval [CI], 1.06–6.71%). Among those receiving rFIX, four subjects (2.45%) had an allergic reaction (95% CI, 0.08–4.83%). Of individuals taking pdFIX products, three (3.41%) developed an allergic reaction (95% CI, 0–7.20%). It was noted that three (1.84%) of those taking rFIX developed an inhibitor to FIX (95% CI, 0–3.90%), while four (4.55%) of those receiving a pdFIX product developed an inhibitor (95% CI, 0.19–8.90%). Inhibitor development was frequently associated with allergic reaction. These results provide evidence that there is no difference in the frequency of allergic reactions or inhibitor development in individuals receiving rFIX compared with those receiving pdFIX concentrates. The current study and a previous study of similar design have now compared the rate of allergic reactions associated with rFIX and pdFIX concentrates has now been compared in a total of 414 subjects; this represents the largest collection of data to date on this rare complication of haemophilia B therapy.

The longitudinal effect of body adiposity on joint mobility in young males with Haemophilia A

Summary.  Although body adiposity and disease severity in haemophilia have been found in cross‐sectional studies to be negatively associated with joint mobility, it is not clear how these two factors affect the rate of joint mobility loss over time. Over a 10‐year period, repeated measures of joint range of motion (ROM) were collected annually using universal goniometers on bilateral hip, knee, ankle, shoulder and elbow joints in 6131 young males with haemophilia A aged ≤20 years. Body mass index (BMI) was calculated using data on weight and height during follow up. The effect of body adiposity, adjusted for disease severity, on the rate of joint mobility loss over time was assessed using a longitudinal model. Compared with haemophilia males with normal BMI, those who were obese had lower ROM at initial visit and a faster rate of joint mobility loss in the lower limbs. Overweight subjects experienced similar loss in ROM, although to a lesser degree. A decline in ROM with age was also observed in upper limb joints but the rate was not significantly affected by body adiposity. Haemophilia severity, joint bleeding and the presence of an inhibitor were other significant contributors to joint mobility loss in both upper and lower limb joints. Excess body adiposity accelerates joint mobility loss in weight bearing joints particularly among those with severe haemophilia. Our findings suggest that body weight control and effective treatment of bleeds should be implemented together to achieve better joint ROM outcomes in males with haemophilia.

A genome-wide association study of resistance to HIV infection in highly exposed uninfected individuals with hemophilia A

Human genetic variation contributes to differences in susceptibility to HIV-1 infection. To search for novel host resistance factors, we performed a genome-wide association study (GWAS) in hemophilia patients highly exposed to potentially contaminated factor VIII infusions. Individuals with hemophilia A and a documented history of factor VIII infusions before the introduction of viral inactivation procedures (1979-1984) were recruited from 36 hemophilia treatment centers (HTCs), and their genome-wide genetic variants were compared with those from matched HIV-infected individuals. Homozygous carriers of known CCR5 resistance mutations were excluded. Single nucleotide polymorphisms (SNPs) and inferred copy number variants (CNVs) were tested using logistic regression. In addition, we performed a pathway enrichment analysis, a heritability analysis, and a search for epistatic interactions with CCR5 Δ32 heterozygosity. A total of 560 HIV-uninfected cases were recruited: 36 (6.4%) were homozygous for CCR5 Δ32 or m303. After quality control and SNP imputation, we tested 1 081 435 SNPs and 3686 CNVs for association with HIV-1 serostatus in 431 cases and 765 HIV-infected controls. No SNP or CNV reached genome-wide significance. The additional analyses did not reveal any strong genetic effect. Highly exposed, yet uninfected hemophiliacs form an ideal study group to investigate host resistance factors. Using a genome-wide approach, we did not detect any significant associations between SNPs and HIV-1 susceptibility, indicating that common genetic variants of major effect are unlikely to explain the observed resistance phenotype in this population.