Comparative pharmacokinetics of rVIII-SingleChain and octocog alfa (Advate(®) ) in patients with severe haemophilia A.

BACKGROUND: rVIII-SingleChain, a novel recombinant factor VIII (rFVIII), has been designed as a B-domain truncated construct with covalently bonded heavy and light chains, aiming to increase binding affinity to von Willebrand factor (VWF). Preclinical studies confirmed greater affinity for VWF, giving improved pharmacokinetic and pharmacodynamic properties compared with full-length rFVIII. AIM: To investigate the pharmacokinetics of rVIII-SingleChain and compare them against those of full-length rFVIII. METHODS: This study enrolled 27 patients with severe haemophilia A in the AFFINITY clinical trial programme. After a 4-day washout period, all patients received a single infusion of 50 IU kg(-1) octocog alfa (Advate(®) ); after a ≥4-day postinfusion washout period, they received a single infusion of 50 IU kg(-1) rVIII-SingleChain. Blood samples for pharmacokinetic assessments of each product were collected before infusion (predose) and at 0.5, 1, 4, 8, 10, 24, 32, 48 and 72 h postinfusion for both products. RESULTS: rVIII-SingleChain had a longer mean half-life (t1/2 ) (14.5 vs. 13.3 h), lower mean clearance (CL) (2.64 vs. 3.68 mL h(-1) kg(-1) ), higher mean residence time (20.4 vs. 17.1 h) and larger mean AUCinf (2090 vs. 1550 IU?h dL(-1) ) than octocog alfa, respectively. The mean AUCinf after rVIII-SingleChain infusion was ~35% larger than after octocog alfa. A similar pattern was observed for AUC0-last . No serious adverse events or inhibitors were reported. CONCLUSIONS: rVIII-SingleChain has a favourable pharmacokinetic profile compared with octocog alfa and was well tolerated. The prolonged t1/2 , larger AUC and reduced CL of rVIII-SingleChain may permit longer dosing intervals, thereby improving patient adherence to prophylactic treatment.

Desmopressin (DDAVP) in the management of patients with congenital bleeding disorders.

Bleeding disorders, including haemophilia, von Willebrand disease, and platelet function abnormalities pose a substantial, ongoing management challenge. Patients with these disorders not only require treatment during bleeding events but also need effective management strategies to prepare for events ranging from minor dental procedures to major surgery and childbirth. Moreover, women with bleeding disorders often require ongoing treatment to prevent menorrhagia during childbearing years. Desmopressin (DDAVP), a synthetic derivative of the antidiuretic hormone l-arginine vasopressin, has become a well-established tool for the management of patients with bleeding disorders in a variety of clinical settings. However, despite the widespread use of DDAVP, the available clinical evidence on its efficacy and safety in these settings is limited, and there has not been a recent comprehensive review of its role in the clinical management of patients with bleeding disorders. As such, this article provides a review of the mechanism of action and pharmacokinetic properties of DDAVP, followed by a concise summary of the available evidence for its use in the treatment and prevention of bleeding.

Physician preferences for medication attributes for the prophylactic treatment of patients with severe haemophilia A with inhibitors to factor VIII.

Prophylaxis may be beneficial for patients with severe haemophilia A who have developed inhibitors to factor VIII. The aim of this study was to determine physicians' preferences for medication attributes in the prophylactic treatment of this patient population. Haematologists from Europe (EU) and the United States (US) participated in a discrete choice exercise to explore their preferences for medication attributes (efficacy, cost, scientific evidence, dosing frequency and administration time) associated with prophylaxis for severe haemophilia A in patients with inhibitors to factor VIII. Physicians' preferences for medication attributes were assessed through completion of 25 trade-off tasks that included a choice between two hypothetical medications each comprised of one randomized level of each medication attribute. Participants also completed a sociodemographic questionnaire. Data were analysed using a random effects logit model. Participants (N = 36: US = 19; EU = 17) were 80.6% men, had a mean of 19.8 years (SD ± 8.1) [range 6-35] of practice experience. The physicians treated an average of 5.7 (± 5.5) patients with severe haemophilia A and inhibitors per month and reported treating 36.2% of these patients prophylactically. The most important medication attributes for prophylactic treatment were efficacy [Relative Importance (RI) = 35.0%] and scientific evidence (RI = 34.1%), whereas treatment cost (12.0%), dosing frequency (10.8%) and administration time (8.2%) were less important. Results were similar across the EU and US. Efficacy and scientific evidence are the primary considerations for physicians' choice of prophylactic medications for use in this patient population.

Case studies in the management of refractory bleeding in patients with haemophilia A and inhibitors.

In haemophilia patients with well-established high-titer inhibitors, even seemingly minor acute bleeding episodes or surgical procedures may become refractory to treatment and transform into limb- or life-threatening situations. In the absence of evidence-based treatment guidelines, this article presents 10 cases of difficult to control acute and surgical bleeding and offers consensus opinions regarding their management from a panel of experienced haemophilia treaters.

Health-related quality of life in patients with haemophilia and inhibitors on prophylaxis with anti-inhibitor complex concentrate: results from the Pro-FEIBA study.

Patients with haemophilia A and inhibitors are at high risk for severe bleeding, progression of joint disease and deterioration of health-related quality of life (HRQoL). To determine the impact of prophylaxis with an activated prothrombin complex concentrate (aPCC) on HRQoL, HRQoL was assessed using the Short-Form (SF)-36 Health Survey and the EQ-5D questionnaire in subjects ≥ 14 years participating in a prospective, randomized, crossover study comparing 6 months of aPCC prophylaxis with 6 months of on-demand therapy. Eighteen of 19 patients completed the survey or questionnaire before and after the on-demand therapy and prophylaxis periods. A general trend towards improved HRQoL after prophylaxis was observed for the 18 evaluable patients in all SF-36 dimensions except for vitality/energy and physical functioning. After prophylaxis, 'good responders,' defined as patients experiencing ≥ 50% reduction in bleeding, exhibited statistically and clinically significant differences in the physical component score (P = 0.021), role - physical (P = 0.042), bodily pain (P = 0.015), and social functioning (P = 0.036). Similarly, the EQ-5D health profile showed a trend towards improvement after prophylaxis in all evaluable patients. Among the good responders, improvements did not differ from those observed after on-demand treatment. EQ visual analogue scale values were slightly improved following prophylaxis for all evaluable patients and the EQ-5D utility index improved in the good responders only. During prophylaxis, patients missed significantly fewer days from school or work because of bleeding than during on-demand treatment (P = 0.01). In conclusion, by significantly reducing bleeding frequency in good responders, aPCC prophylaxis improved HRQoL compared with on-demand treatment.

Opinions on radiosynovectomy for chronic haemophilic synovitis: point/counterpoint.

Joint bleeding is the hallmark of severe haemophilia and the major cause of disability in patients with this coagulopathy. Repeated bleeding into the same joint can lead to chronic synovitis and progressive arthropathy. Radiosynovectomy is one option for the treatment of chronic haemophilic synovitis, but concerns about the risks of exposure to ionizing radiation have divided clinicians as to the safety and appropriate use of the procedure. This article presents two differing viewpoints, one from a pair of orthopaedic surgeons who collectively have performed more than 300 radiosynovectomies in patients with haemophilia. They maintain that radiosynovectomy is a simple, effective, safe and low-cost technique children and adults with chronic haemophilic synovitis. The other perspective is from an experienced haemophilia treater who directs a major US haemophilia treatment centre. She believes that unresolved questions about the safety of radiation exposure in children argue against the use of radiosynovectomy in paediatric patients with haemophilia.

Current prescription of prophylactic factor infusions and perceived adherence for children and adolescents with haemophilia: a survey of haemophilia healthcare professionals in the United States.

The primary goal of prophylaxis in patients with severe haemophilia is to convert the phenotype from severe to moderate and to prevent the development of chronic arthropathy. Prior studies have demonstrated that prophylaxis decreases episodes of joint bleeds and chronic arthropathy. Effectiveness depends on prescription of prophylaxis and adherence to the prescribed regimen. The aim of this study was to determine if prescription of prophylaxis for children with haemophilia and perceptions of adherence to prophylaxis have changed since publication of the Joint Outcome Study (JOS). A questionnaire was sent, in electronic and written formats, to health professionals who provide care to children with haemophilia at US haemophilia treatment centres (HTCs). The response rate was 56 of 128 (44%) of the targeted HTCs. There were a few missing data and denominators are provided. All responses agreed with the results of the JOS and 30/55 (55%) reported the JOS increased their prescription of prophylaxis. Nineteen of 56 (34%) physicians or HTC staff reported that they had not prescribed prophylaxis within the last year due to concerns about adherence, and 19/56 (34%) reported they had stopped prophylaxis due to concerns about adherence within the last year. Predicted adherence decreased with increasing age. Prescription of prophylaxis appears to be increasing since publication of the JOS. Strategies to improve adherence may increase the likelihood of physician prescription of prophylaxis and make prophylaxis easier to implement for individual patients, thereby improving the clinical outcome of children and adults with haemophilia.

Outcomes of mentored, grant-funded fellowship training in haemostasis /thrombosis: findings from a nested case-control survey study.

Successful strategies by which to effectively recruit and retain academic subspecialists in benign haematology have not been established. To evaluate the effectiveness of a grant-funded, mentored fellowship with respect to retention and early career goals in haemostasis/thrombosis, we sought to compare outcomes for graduates of a grant-funded, mentored fellowship training programme in haemostasis/thrombosis [the National Hemophilia Foundation (NHF)-Baxter Clinical Fellowship Award] during conventional haematology/oncology fellowship training (cases), vs. their training peers who were graduates of conventional haematology/oncology fellowship training alone (controls), via a nested case-control survey study. Survey response rate was 85% (11/13) for cases and 90% (9/10) for controls. All respondents had pursued careers in academic haematology/oncology. Median (range) percent time spent in benign haematology postfellowship was 98% (70-100%) for cases vs. 0% (0-20%) for controls. Time spent in research was significantly greater among cases than controls (median 80% [range: 42-90%] vs. 55% [10-80%], respectively; P = 0.01). By years 3-4 postfellowship, median annual number of peer-reviewed publications was higher for cases than controls (3.5 vs. 1.0; P = 0.01). Cases were also more successful in grant funding (including K-awards). These data suggest that a grant-funded, mentored fellowship training programme in haemostasis/thrombosis may be superior to conventional haematology/oncology fellowship training alone with respect to outcomes of retention in clinical care/research, early-career grant funding and publication productivity.

Assessing the impact of age, race, ethnicity and inhibitor status on functional limitations of patients with severe and moderately severe haemophilia A.

Few data exist on the impact of age and inhibitor status on activity levels among patients with severe and moderately severe haemophilia A. The aim of this analysis was to assess the impact of age, race/ethnicity and inhibitor status on functional limitations through retrospective analysis of data from the Hemophilia and Thrombosis Research Society (HTRS) Registry. Functional status data from patients with haemophilia A with or without inhibitors who were enrolled in the HTRS Registry between October 1999 and July 2008 were analysed by age, race and ethnicity. Of the 2497 registrants, 1340 had congenital haemophilia A (333 with inhibitors). Functional status was available for 274 subjects with haemophilia A with current inhibitors and 247 subjects without inhibitors who had moderately severe (FVIII levels ≤ 2%). Functional impairment increased with age across five levels of functional status (P < 0.01). Inhibitors were associated with greater functional impairment in two age groups (13-21 years and older than 21 years) [unrestricted activity in 57.8% vs. 63.6% (P = 0.06) and 18.3% vs. 28.6% (P = 0.04), respectively]. Blacks had worse functional status than caucasians across all ages regardless of inhibitor status. Functional status decreases with age, and impairment is greater among patients with inhibitors beginning in adolescence. These results reaffirm the need for early eradication of inhibitors and early treatment of bleeds in inhibitor and non-inhibitor patients. This analysis highlights the benefit of ongoing study of these patients through data collected for the HTRS Registry.

A consensus statement on clinical trials of bypassing agent prophylaxis in inhibitor patients.

The haemophilia literature increasingly contains reports describing the use of bypassing agent prophylaxis (BAP) in patients with severe haemophilia A and inhibitors. However, it is difficult to interpret and compare the results and draw conclusions about treatment efficacy because of small patient numbers and a lack of standardization among BAP studies. This article presents consensus recommendations for standardizing future BAP clinical trials developed by an international panel of haemophilia opinion leaders.

Activity of granzyme A, a serine protease in the killing granules of cytotoxic T lymphocytes, is reduced in cells from HIV-infected hemophiliacs.

Cytotoxic CD8+ lymphocytes (CTLs) kill virally infected target cells by releasing cytotoxic granules. The primary objective of this study was to determine whether the activity of granzyme A, a serine protease in the killing granules of CTLs is altered in HIV-infected hemophiliacs. A sensitive colorimetric assay that measures cleavage of a synthetic substrate, N alpha-benzyloxycarbonyl-L-lysine thiobenzyl ester (BLT), was used to quantitate granzyme A activity. Granzyme A activities from hemophiliacs were normalized to to granzyme A activities of healthy donors run concurrently. Granzyme A activity in CD8+ T cells from HIV-seropositive hemophiliacs was significantly lower than granzyme A activity in cells from HIV-seronegative hemophiliacs (0.48 units +/- 0.086/CD8+ T cell and 1.573 +/- 0.434 units/CD8+ T cell, respectively; p < 0.005). These results indicate that cytotoxic cells in HIV-infected hemophiliacs have reduced granzyme A activity, which may result in a defect in CTL-mediated cell killing in these patients.

Rituximab for treatment of inhibitors in haemophilia A. A Phase II study.

The development of antibodies against infused factor VIII (FVIII) in patients with haemophilia A is a serious complication leading to poorly controlled bleeding and increased morbidity. No treatment has been proven to reduce high titre antibodies in patients who fail immune tolerance induction or are not candidates for it. The Rituximab for the Treatment of Inhibitors in Congenital Hemophilia A (RICH) study was a phase II trial to assess whether rituximab can reduce anamnestic FVIII antibody (inhibitor) titres. Male subjects with severe congenital haemophilia A and an inhibitor titre ≥5 Bethesda Units/ml (BU) following a FVIII challenge infusion received rituximab 375 mg/m² weekly for weeks 1 through 4. Post-rituximab inhibitor titres were measured monthly from week 6 through week 22 to assess treatment response. Of 16 subjects who received at least one dose of rituximab, three (18.8%) met the criteria for a major response, defined as a fall in inhibitor titre to <5 BU, persisting after FVIII re-challenge. One subject had a minor response, defined as a fall in inhibitor titre to <5 BU, increasing to 5-10 BU after FVIII re-challenge, but <50% of the original peak inhibitor titre. Rituximab is useful in lowering inhibitor levels in patients, but its effect as a solo treatment strategy is modest. Future studies are indicated to determine the role of rituximab as an adjunctive therapy in immune tolerisation strategies.

Quantifying adherence to treatment and its relationship to quality of life in a well-characterized haemophilia population.

It is known that chronically ill patients adhere to medical treatment plans only 50% of the time. Adherence to treatment with factor infusion therapy in haemophilia patients is essential to stop bleeding. It also prevents both acute and chronic life and limb threatening complications. This study, performed in a well-described haemophilia population, was completed in an effort to understand the critical issue of adherence in patients with haemophilia. A major component of the methodology of this study was the development of a unique scoring system to quantify adherence. Adherence scores in patients on On-Demand treatment strategies were then compared to those on High Intensity treatment strategies. Quality of life (QoL) studies were also performed on the study population to assess the association of treatment regimen and adherence scores to QoL measures. Results of this study demonstrated that adherence to On-Demand therapy was significantly greater than adherence to High Intensity treatment regimens and in children, High Intensity treatment regimens, which included prophylaxis, correlated with better QoL scores in body pain. It is envisioned that the development of an objective scoring system for adherence will prove useful in future studies of adherence as well as in the development of intervention strategies that can overcome barriers to adherence in haemophilia patients.

Inhibitor development and successful immune tolerance in an HIV-infected patient with haemophilia A and after immune reconstitution with HAART.

This is the case of a 28-year-old man with severe congenital haemophilia A, who had a relatively mild bleeding course during early childhood, with limited factor VIII (FVIII) exposure. He was infected with HIV before the age of 7 years, and demonstrated profound immunodeficiency from childhood, with very low CD4+ cell counts for more than a decade. Following initiation of highly active anti-retroviral therapy (HAART) and gradually increasing CD4+ cells, he presented for the first time with a high-titre inhibitor at age 26, despite over 1000 previous FVIII exposures. Subsequently, his inhibitor was successfully eradicated with a standard immune tolerance protocol. It is likely that the effects of chronic HIV infection on T-lymphocyte pathways, and the partial immune reconstitution resulting from HAART, led to this patient's unusual inhibitor course. Such a case serves to augment knowledge gained in animal studies about the immunobiology of FVIII inhibitors.