FRONTIER1: a partially randomized phase 2 study assessing the safety, pharmacokinetics, and pharmacodynamics of Mim8, a factor VIIIa mimetic

BACKGROUND

Mim8 (denecimig) is a factor VIII (FVIII) mimetic bispecific antibody in development for the treatment of hemophilia. Data from the phase 1 part of FRONTIER1 (EudraCT: 2019-000465-20, NCT04204408, and NN7769-4513) suggested that Mim8 was well tolerated in healthy participants and exhibited pharmacokinetic (PK) properties consistent with dose proportionality.

OBJECTIVES

The partially randomized, phase 2, multiple ascending dose (MAD) part of FRONTIER1 aimed to evaluate the safety, PK, pharmacodynamics (PD), and exploratory efficacy of Mim8 in participants with hemophilia A with or without FVIII inhibitors.

METHODS

The MAD part of FRONTIER1 consisted of 42 participants, assigned to 5 cohorts, with participants in cohorts 3 and 4 randomized 1:1 to dosing weekly or every 4 weeks, respectively. Four of the 42 participants (9.5%) had FVIII inhibitors prior to study enrolment. The primary endpoint was treatment-emergent adverse events (TEAEs). PK and PD were evaluated by Mim8 plasma concentration and thrombin generation, respectively. Exploratory efficacy was assessed via the number of treated bleeds. Safety and PD parameters were also evaluated from an exploratory cohort treated with emicizumab.

RESULTS

Mim8 was well tolerated, with 1 serious TEAE (anxiety-related chest pain) deemed unrelated to Mim8. There was no dose dependency on the number, causality, type, or severity of TEAEs. PK/PD properties supported weekly to monthly dosing approaches, and few participants experienced treated bleeds beyond the lowest dose cohort (1 in cohorts 2 and 3, and 3 in cohort 5).

CONCLUSION

These data support the continued clinical development of Mim8, and FRONTIER1 has proceeded onto an extension phase.

Hemostatic performance of chitosan-based hydrogel and its study on biodistribution and biodegradability in rats

Hemostasis is of great significance regardless of the smooth operation or postoperative recovery. Therefore, it is urgent to develop a hemostatic material with excellent biodegradability and biocompatibility. It is well known that both carboxymethyl chitosan and hyaluronic acid with biodegradability and biocompatibility have wound healing promoting property. Here, a degradable chitosan-based hydrogel was prepared based on carboxymethyl chitosan and cross-linked by oxidized hyaluronic acid. The hemostatic performance of the hydrogel in rat liver resection injury was evaluated which results showed that the hydrogel exhibited comparable hemostatic properties compared with Fibrin Sealant. In addition, the hydrogel proved to be rapidly absorbed by the body without significant accumulation in vivo, demonstrating good biodegradability and biocompatibility. The overall results suggested the hydrogel will be a promising hemostatic hydrogel for controlling bleeding.

Prophylactic administration of glycoPEGylated factor IX provides protection and joint outcome superior to recombinant factor IX after induced joint bleeding

BACKGROUND

Following induced joint hemorrhage, hemophilia B results in the abnormal persistence of iron deposition, inflammation, and neovascularity of the synovial tissue, as well as deterioration of the bone articular surface and strength. Previously, we demonstrated that a factor IX (FIX) replacement protein with extended circulating FIX activity, glycoPEGylated FIX nonacog beta pegol (N9-GP), could improve synovial and osteochondral parameters in F9 knockout mice when administered after joint injury.

OBJECTIVE

We explored the use of N9-GP prior to unilateral joint hemorrhage and compared to unmodified recombinant FIX (rFIX).

METHODS

Pharmacodynamics, histology, and microcomputed tomography were used to assess the effects of prophylactic administration of glycoPEGylated FIX.

RESULTS

In comparison to rFIX, N9-GP significantly improved soft tissue histological parameters, as well as bone outcome at 2 weeks post injury, while performing equally in reduction of blood present in the joint space assessed 1 day after injury.

CONCLUSIONS

These results indicate that, in comparison to rFIX, the prophylactic use of extended half-life FIX provides superior protection from bleeding-induced joint damage, manifested by improved correction of histologic parameters.

Functional polymorphisms in the LDLR and pharmacokinetics of Factor VIII concentrates

BACKGROUND

Optimization of factor VIII (FVIII) infusion in hemophilia A would benefit from identification of FVIII pharmacokinetics (PK) determinants. The low-density lipoprotein receptor (LDLR) contains an FVIII-binding site and might influence FVIII clearance. Consistently, LDLR polymorphisms have been associated with FVIII levels.

OBJECTIVE

To investigate the relationships between individual FVIII PK and functional LDLR polymorphisms.

PATIENTS/METHODS

Thirty-three hemophilia A patients (FVIII coagulant activity [FVIII:C] ≤2 IU/dL) without inhibitors underwent 85 FVIII single-dose (21.4-51.8 IU/kg) PKs with different FVIII concentrates. Twenty patients underwent repeated PKs (2-6).

FVIII

C measured up to 72 hours was analyzed by two-compartment model. Parameters were evaluated in relation to F8 mutations, ABO blood-group and LDLR genotypes.

RESULTS

F8 mutation types were not associated with PK parameters. ABO and LDLR c.1773C/T polymorphism were associated with Alpha, Alpha HL, CLD2, K1-2, and K2-1 parameters, suggesting an influence on the FVIII initial distribution phase. Regression analysis showed an independent association of both ABO and LDLR c.1773C/T with PK parameters (Alpha, β-coefficient -0.311 vs 0.348; CLD2, β-coefficient -0.335 vs 0.318), giving rise to an additive effect in subjects stratified by combined phenotypes. Differently, the LDLR c.81C/T was associated with FVIII clearance and volume of distribution at steady state, which could be related to distinct effects of polymorphisms, potentially linked to LDLR intracellular distribution and FVIII binding behavior.

CONCLUSIONS

With the limitation of different FVIII concentrates and low number of patients, our data show plausible associations of LDLR polymorphisms with FVIII PK parameters, thus supporting their investigation as candidate functional determinants of FVIII PK.

Comparative pharmacokinetics of two extended half-life FVIII concentrates (Eloctate and Adynovate) in adolescents with hemophilia A: Is there a difference?

Essentials The PK parameters of Eloctate vs Adynovate were compared using one-stage and chromogenic assays in 25 boys (12-18 years). The FVIII levels were taken at 3, 24, 48, and 72 hours following a dose of either FVIII; levels analyzed by WAPPS PK program. The PK profiles (half-life, clearance, and time to 5%, 3%, and 1%) were not statistically different for the two EHL FVIIIs. The significant interpatient variability in PK is mainly related to VWF levels (and blood group).

BACKGROUND

A head-to-head comparison of the pharmokinetcs (PK) of extended half-life (EHL) factor VIII (FVIII) concentrates in the same subjects has not been reported. Recently, boys (ages 12-18 years) with hemophilia A in Canada were required to switch from Eloctate to Adynovate.

OBJECTIVES

Compare the PK profiles of Eloctate vs Adynovate in the same boys.

METHODS

Boys switching from Eloctate to Adynovate prophylaxis had FVIII levels sampled at 3, 24, 48, and 72 hours following a regular prophylactic infusion of Eloctate and then 1-3 months later, of Adynovate. Testing was done by one-stage assay (OSA) and chromogenic assay (CA). The PK parameters were determined with the Web Accessible Population Pharmacokinetic Service (WAPPS)-Hemo PK tool.

RESULTS

Twenty-five boys (mean age 15.3 years; range: 12.1-18.4; 9 O blood group) underwent switching. Mean (range) terminal half-lives with the OSA were 16.1 hours (10.4 to 23.4; Eloctate) and 16.7 hours (11.0 to 23.6; Adynovate) (NS). With the CA, these were 18.0 hours (12.0 to 25.5; Eloctate) and 16.0 hours (10.3 to 22.9; Adynovate) (P = 0.001). There were no significant differences between the two EHL-FVIIIs in clearance, area under the concentration vs time curve (AUC), Vss, or time for FVIII levels to drop to 5%, 3%, and 1%. At the 72-h time point, mean observed FVIII levels following a mean dose of 39.3 IU/kg of Eloctate were 4.4% (OSA) and 4.4% (CA). For Adynovate, these were 5.1% (OSA) and 5.3% (CA) following similar doses. There was considerable interpatient variation in PK, mainly explained by differences in blood group/von Willebrand factor (VWF) levels.

CONCLUSIONS

Eloctate and Adynovate have almost identical PK parameters. When switching from one to another no prophylaxis regimen change is needed.

Clinical pharmacology, efficacy and safety study of a triple-secured fibrinogen concentrate in adults and adolescent patients with congenital fibrinogen deficiency

Essentials A novel fibrinogen concentrate was evaluated in patients with congenital fibrinogen deficiency. An open-label, phase 2-3 trial studied pharmacology, efficacy, and safety in patients >6 years. The product offers safe and effective therapy in the treatment and prophylaxis of bleeding. Data in recovery show the need of adjusted treatment and further investigation in children. SUMMARY: Background Single-factor replacement therapy is considered the most suitable treatment option for hereditary fibrinogen deficiency. A triple-secured plasma-derived human fibrinogen product was developed to increase the safety of the former fibrinogen concentrate. Objectives This non-randomized, open-label, prospective study investigated pharmacokinetics, efficacy, and safety of a novel fibrinogen concentrate (FibCLOT® /CLOTTAFACT® LFB, France) in inherited deficiency. Patients/Methods Fourteen patients ≥40 kg received fibrinogen concentrate for pharmacology and 16 ≥ 23 kg received treatment for bleeding or surgery. Each treatment was followed by a 3-week safety observation period. Key outcomes included number of infusions, dose, bleeding control, daily assessment, hemoglobin, blood loss, transfusions, and physicians' global assessment of response. Results Incremental recovery was 2.35 mg mL-1  per mg kg-1 and maximal concentration 1.41 g L-1 (geometric mean) after 0.060 g kg-1 infusion in 14 afibrinogenemic patients. Terminal half-life was 69.3 h (non-compartmental analysis). The maximum clot firmness was increased by a mean of 10.3 mm from baseline to maximal effect. Sixteen patients participated to the efficacy phase: 32 bleeding episodes were treated in 9 patients, and 15 patients underwent 38 surgical/invasive procedures. All patients achieved appropriate hemostasis: response to treatment was successful in all bleeds (95% CI, 0.89-1.00) and procedures (95% CI, 0.91-1.00). Most (94%) bleeds were controlled with a single infusion (median 0.050 g kg-1 ). Two patients experienced asymptomatic distal venous thromboses identified by systematic ultrasound. Conclusion FibCLOT® /CLOTTAFACT® showed a pharmacokinetic profile comparable to that of other fibrinogen concentrates and provides safe and clinically effective substitution therapy for fibrinogen-deficient patients.

Administration of recombinant FVIIa (rFVIIa) to concizumab-dosed monkeys is safe, and concizumab does not affect the potency of rFVIIa in hemophilic rabbits

Essentials Hemophilia patients on concizumab prophylaxis may need rFVIIa to treat breakthrough bleeds. Effect and safety of concizumab + rFVIIa were tested in vitro and in vivo. Concizumab + rFVIIa had no additive effects on bleeding in hemophilic rabbits. High steady-state levels of concizumab did not affect the safety of rFVIIa in cynomolgus monkeys. SUMMARY: Background Concizumab is a monoclonal antibody (mAb) against tissue factor pathway inhibitor (TFPI), currently in clinical development as a subcutaneous prophylactic therapy for hemophilia A/B with and without inhibitors. In patients with inhibitors, the treatment choice for breakthrough bleeding will comprise bypassing agents, e.g. activated recombinant FVIIa (rFVIIa) or activated prothrombin complex concentrates. Objectives To explore the effect and safety of concizumab and rFVIIa when they are simultaneously present. Methods Human blood made hemophilic with a FVIII antibody was spiked with increasing concentrations of concizumab, rFVIIa, or concizumab and rFVIIa in combination, and this was followed by thrombin generation test or thromboelastography. Blood loss in hemophilic rabbits was measured when concizumab, rFVIIa or concizumab + rFVIIa was administered either before or during cuticle bleeding. In a safety study, cynomolgus monkeys were exposed to high steady-state concizumab concentrations and given three doses of rFVIIa, and then subjected to full necropsy and histopathological examination. Results In human blood, concizumab + rFVIIa had more pronounced procoagulant effects under hemophilic conditions than the sum of individual responses. In contrast, concizumab + rFVIIa had no additional effects on blood loss in hemophilic rabbits as compared with rFVIIa or concizumab alone. In cynomolgus monkeys, the macroscopic and microscopic pathological examinations revealed no thrombi or other signs of excessive coagulation activation. Both rFVIIa and concizumab caused increases in thrombin-antithrombin and D-dimer concentrations; this effect tended to be additive with concomitant administration. Conclusions Concizumab did not affect the potency or safety of rFVIIa in vivo. These results support a clinical evaluation of rFVIIa at standard dose (90 μg kg-1 ) to treat breakthrough bleeds in concizumab clinical trials.

Zeolite-loaded alginate-chitosan hydrogel beads as a topical hemostat

Hemorrhage is the leading cause of preventable death after a traumatic injury, and the largest contributor to loss of productive years of life. Hemostatic agents accelerate hemostasis and help control hemorrhage by concentrating coagulation factors, acting as procoagulants and/or interacting with erythrocytes and platelets. Hydrogel composites offer a platform for targeting both mechanical and biological hemostatic mechanisms. The goal of this work was to develop hydrogel particles composed of chitosan, alginate, and zeolite, and to assess their potential to promote blood coagulation via multiple mechanisms: erythrocyte adhesion, factor concentration, and the ability to serve as a mechanical barrier to blood loss. Several particle compositions were synthesized and characterized. Hydrogel bead composition was optimized to achieve the highest swelling capacity, greatest erythrocyte adhesion, and minimal in vitro cytotoxicity. These results suggest a polymer hydrogel-aluminosilicate composite material may serve as a platform for an effective hemostatic agent that incorporates multiple mechanisms of action. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1662-1671, 2018.

Pharmacokinetics and the transition to extended half-life factor concentrates: communication from the SSC of the ISTH

Extended half-life proteins (EHL) are increasingly used in clinical practice, but there is no standardized approach to sampling, interpretation and implementation of pharmacokinetics (PK) data to maximize treatment benefit. The goal of EHL treatment is to attain a trough level sufficient to protect against spontaneous bleeds and reduce infusion frequency and limitations on individual activity and lifestyle. Performing classical PK assessments requires multiple blood samples, which is burdensome for patients and providers. Herein we review a population pharmacokinetic (popPK) approach to estimate individual PK parameters to transition patients from standard half-life (SHL) to EHL concentrates. We propose that a minimum of two to four post-infusion samples is sufficient to estimate individual PK profiles, with sufficient certainty to maintain factor levels above 1% and achieve bleed-free lifestyles. We also survey current PK use in patients transitioning to EHL, review key PK parameters and popPK models, and recommend an approach to using PK in patients initiating or switching to EHL.

Preclinical pharmacokinetics and biodistribution of subcutaneously administered glycoPEGylated recombinant factor VIII (N8-GP) and development of a human pharmacokinetic prediction model

Essentials N8-GP is an extended half-life recombinant factor VIII (FVIII) for the treatment of hemophilia A. Subcutaneous (SC) FVIII dosing might reduce the treatment burden of prophylaxis. SC N8-GP has a favorable PK profile in animal models and disappears from skin injection sites. Combined animal (SC) and clinical (IV) data suggest that daily SC dosing may provide prophylaxis.

SUMMARY

Background N8-GP is an extended half-life recombinant factor VIII (FVIII) for the treatment of hemophilia A. Subcutaneous administration of FVIII may reduce the treatment burden of prophylaxis; however, standard FVIII products have low bioavailability after subcutaneous dosing in animals. Objective To evaluate the pharmacokinetics, effectiveness and local distribution of subcutaneously administered N8-GP in preclinical models and predict the human pharmacokinetic (PK) profile. Methods The pharmacokinetics of subcutaneously administered N8-GP were evaluated in FVIII knockout (F8-KO) mice and cynomolgus monkeys; a human PK prediction model in hemophilia A patients was developed. The hemostatic effect was evaluated in a tail vein bleeding model in F8-KO mice. The injection-site distribution and absorption of subcutaneously administered N8-GP were assessed in F8-KO mice by the use of temporal fluorescence imaging and immunohistochemistry. Results Subcutaneously administered N8-GP had a bioavailability, a first-order absorption rate and a half-life, respectively, of 24%, 0.094 h-1 and 14 h in F8-KO mice, and 26%, 0.33 h-1 and 15 h in cynomolgus monkeys. A dose-dependent effect of subcutaneously administered N8-GP on blood loss was observed in mice. A minimal amount of N8-GP was detected at the injection site 48-72 h after single or multiple dose(s) in F8-KO mice. Subcutaneously administered N8-GP was localized to the skin around the injection site, with time-dependent disappearance from the depot. PK modeling predicted that subcutaneously administered N8-GP at a daily dose of 12.5 IU kg-1 will provide FVIII trough levels of 2.5-10% in 95% of patients with severe hemophilia A. Conclusions Subcutaneously administered N8-GP may provide effective hemophilia A prophylaxis. A phase I clinical trial is underway to investigate this possibility.

Continuous infusion of recombinant factor VIIa for surgery in patients with deficiency of factor VII

The administration of recombinant activated factor VII (rFVIIa) by continuous infusion has provided a safe and convenient alternative to bolus injections in haemophiliacs with inhibitors, but it has only been reported in a single case with congenital factorVII (FVII) deficiency. The results of 12 consecutive surgical procedures in 7 patients with congenital FVII deficiency are reported here. rFVIIa was always given in continuous infusion, aiming at plasma FVII activity of 0.5 IU/mL. Treatment was given for 2 to 7 days with a mean total dose of 7.8 mg rFVIIa. Blood loss was as expected from the different types of procedures and the only thromboembolic complication was a superficial thrombophlebitis at the infusion site. This mode of substitution was therefore safe, effective and well tolerated.

In silico evaluation of limited blood sampling strategies for individualized recombinant factor IX prophylaxis in hemophilia B patients

Essentials Individual pharmacokinetic (PK) parameters can be obtained by limited sampling strategies (LSSs). Following 100 IU kg-1 rFIX, LSSs with 1 to 3 samples were evaluated in 5000 simulated subjects. For all LSSs, estimated individual PK parameters showed acceptable bias and precision. One sample between 10 min-3 h and two between 48 h-56 h showed best predictive performance.

SUMMARY

Background Patients with severe hemophilia B regularly administer prophylactic intravenous doses of clotting factor IX concentrate to maintain a trough level of at least 0.01 IU mL-1 in order to prevent joint bleeds. Assessment of individual pharmacokinetic (PK) parameters allows individualization of the recombinant factor IX (rFIX) dose. Aim To evaluate the predictive performance of limited sampling strategies (LSSs) with one to three samples to estimate individual PK parameters of rFIX. Methods Monte Carlo simulations were performed to obtain 5000 concentration-time profiles by the use of population PK parameters for rFIX from literature. Eleven LSSs were developed with one, two or three samples taken within an 80-h interval following administration of 100 IU kg-1 rFIX. Clearance (CL), half-life (t1/2 ), time to 1% and steady-state distribution volume (Vss ) were estimated for each simulated individual by the use of Bayesian analysis. Results For each LSS, average bias was small for CL (range - 1.5% to 1.4%), t1/2 (range - 4.5% to - 0.7%), time to 1% (range - 2.9% to 0%), and Vss (range - 3.7% to 0.3%). Imprecision for these parameters ranged from 6.4% to 11.9%, from 10.3% to 15.6%, from 7.3% to 10.9%, and from 9% to 20.1%, respectively. The best predictive performance was achieved with one sample taken between 10 min and 3 h and two samples taken between 48 h and 56 h after administration of rFIX. Conclusions This study demonstrates that limited sampling strategies, used for individualized dosing of rFIX in hemophilia B patients, can be developed and evaluated by in silico simulation.

[Topical haemostatic agents in neurosurgery]

Haemostasis is of fundamental significance in neurosurgery, and insufficient control of bleeding is associated with morbidity and mortality. Topical haemostatic agents play an important role, as the characteristics of neuronal tissue limit the use of classical surgical haemostasis techniques. Appropriate choice of agent depends on the location and type of bleeding, but also on knowledge of the products' mechanisms of action, indications, price and accessibility. Biological products are superior to the mechanical in efficacy but require more preparation and are significantly more cost-intensive.

Delayed Absorption of Oxidized Cellulose (Surgicel) in Post-Thyroidectomy Patients

Delayed absorption of oxidized cellulose (Surgicel; Johnson & Johnson, New Brunswick, NJ) may mimic a pseudoabscess or a recurrent mass on sonography after tumor surgery. Here we present 3 cases of thyroidectomy in which Surgicel was still apparent on sonography after 26 to 47 months of follow-up. We show sonographic findings and discuss the utility of sonography for diagnosis of delayed absorption of Surgicel in post-thyroidectomy patients.

Modelling of vitamin K half-life in patients treated with vitamin K antagonists before hip fracture surgery

BACKGROUND

Guidelines recommend treatment with vitamin K in patients requiring reversal of the effect of vitamin K antagonists (VKA) before semi-urgent surgery. In clinical practice, the time for reversal of the international normalized ratio (INR) to values adequate for surgery is often reported longer than the expected 12-24 hours, which may delay surgery and increase the risk of complications.

METHODS

In order to optimize the management of elderly patients treated with VKA and undergoing hip fracture surgery, we aimed to model the vitamin K half-life in this specific population. Files for patients admitted between 2006 and 2008 for hip fracture surgery and chronically treated with VKA were retrospectively studied. Only patients with an INR superior to 1.5 upon arrival were included in the study. The effect of vitamin K on the decrease in INR was modelled after a PK/PD analysis using NONMEM. Thirty-one patients' files were analysed.

RESULTS

Despite management in accordance with guidelines, 31% of the patients had a delayed return to INR values<1.5 resulting in delayed surgery. Time to INR<1.5 was longer than 24 hours in 50% of the patients. The calculated half-life of vitamin K was 24.7 hours in this population.

CONCLUSION

The vitamin K half-life in elderly patients treated with VKA and undergoing hip fracture surgery was prolonged. The use of vitamin K or of a more rapid acting alternative should be discussed, depending on the urgency of the surgery.

Longer-acting clotting factor concentrates for hemophilia

Hemophilia, when severe, leads to spontaneous life-threatening bleeding episodes. Current therapy requires frequent intravenous infusions. Most patients must limit their physical activities to avoid bleeding when the factor activity levels are below normal. In 2014, new therapeutic factor VIII and IX products were approved in Canada and the U.S. Over the next couple of years, other new factor products will likely be approved. These new factors have been engineered to have improved pharmacokinetic properties, including extended half-life in circulation, thus providing major therapeutic advances for patients with hemophilia. In the completed clinical trials, over 700 patients have successfully used these longer acting products regularly for more than one year. These promising new therapies should allow patients with hemophilia to use fewer infusions to prevent spontaneous bleeding or to treat bleeding episodes, and to provide appropriate clotting factor levels for different physical activities.

Half-life extended factor VIII for the treatment of hemophilia A

Prophylactic infusion of factor VIII (FVIII) prevents joint bleeding and other hemorrhages in patients with hemophilia A. Conventional FVIII concentrates have a short half-life, with an average of about 12 h in adults, ranging in individual patients between 6 and 24 h, and even shorter in younger children. Therefore, effective prophylaxis requires frequent intravenous injection, usually three times per week or every other day. Several technologies are currently under investigation to extend the half-life of FVIII, including Fc fusion (Eloctate, Elocta, efmoroctocog alfa), addition of polyethylene glycol (turoctocog alfa pegol [N8-GP], BAY 94-9027, BAX 855), and a single-chain construct (CSL627). This review summarizes characteristics of products in clinical development and discusses their potential benefits.

Soy phosphatidylinositol containing nanoparticle prolongs hemostatic activity of B-domain deleted factor VIII in hemophilia A mice

Factor VIII (FVIII) replacement therapy in hemophilia A (HA) is complicated by a short half-life and high incidence of inhibitory antibody response against the protein. Phosphatidylinositol (PI) containing lipidic nanoparticles have previously been shown to reduce the immunogenicity and prolong the half-life of full length FVIII. It has not been established whether this prolongation in half-life improves hemostatic efficacy and whether this approach could be extended to the B-domain deleted form of FVIII (BDD FVIII). In the current study, we evaluated the pharmacokinetics (PK), hemostatic efficacy, and immunogenicity of BDD FVIII associated with PI nanoparticles (PI-BDD FVIII) in HA mice. Comparative human PK was predicted using an "informed scaling" approach. PI-BDD FVIII showed an approximate 1.5-fold increase in terminal half-life compared with free BDD FVIII following i.v. bolus doses of 40 IU/kg. PI-BDD FVIII-treated animals retained hemostatic efficacy longer than the free FVIII-treated group in a tail vein transection model of hemostasis. PI association reduced the development of inhibitory and binding antibodies against BDD FVIII after a series of i.v. injections. The combined improvements in circulating half-life and hemostatic efficacy could significantly prolong the time above clinically established therapeutic thresholds of prophylactic FVIII replacement therapy in humans.

Prophylactic efficacy and pharmacokinetically guided dosing of a von Willebrand factor/factor VIII concentrate in adults and children with von Willebrand's disease undergoing elective surgery: a pooled and comparative analysis of data from USA and European Union clinical trials

BACKGROUND

Surgical intervention may pose significant risk of life-threatening bleeding in patients with von Willebrand's disease; prophylactic treatment with von Willebrand factor/factor VIII concentrate is generally indicated for von Willebrand's disease characterized by moderate to severe qualitative and quantitative deficiencies of Willebrand factor to raise and maintain both Willebrand factor and FVIII at haemostatic levels for surgical prophylaxis.

MATERIALS AND METHODS

Since prospective clinical data in such situations were lacking, two recent, prospective, multicentre studies evaluated the prophylactic perioperative use of the on Willebrand factor/ factor VIII concentrates, Humate-P® and Haemate P. Despite some differences in the two studies, one conducted in the USA (n =35) and one in the European Union (n =27), the designs were similar enough to allow for a limited pooled analysis of data. In both studies, preoperative loading doses and subsequent maintenance doses were calculated using individual subject-derived incremental in vivo recovery values, although von Willebrand factor:ristocetin cofactor and FVIII:coagulation activity target levels differed between the protocols. Efficacy was rated daily by the investigator as excellent, good, moderate, or poor.

RESULTS

Overall haemostatic efficacy (rating of excellent/good), assessed 24 hours after the last infusion (USA) or taken as the worst rating between surgery and day 14 (EU), was achieved in 95% of the pooled population of 62 adults and children. Efficacy did not appear to be affected by dosing variations. The rate of possibly related adverse events was low (8 subjects; 13%); one of these events was considered serious (pulmonary embolism).

DISCUSSION

This pooled analysis of a relatively large number of patients for a rare disease confirms the feasibility of pharmacokinetically guided dosing of von Willebrand factor/factor VIII concentrate and highlights its efficacy and safety in the prevention of excessive perioperative bleeding.

Calibrated bioresorbable microspheres: a preliminary study on the level of occlusion and arterial distribution in a rabbit kidney model

PURPOSE

To assess the level of occlusion and arterial distribution of calibrated bioresorbable microspheres (BRMS-I and BRMS-II) compared with tris-acryl gelatin microspheres (TGMS) after renal embolization.

MATERIALS AND METHODS

Six rabbits underwent renal embolization with 100-300 µm BRMS-I and TGMS; three rabbits received partial occlusion (group 1, n = 3), and three rabbits received total occlusion (group 2, n = 3). Four other rabbits received 100-300 µm BRMS-II (with higher cross-linking density than BRMS-I) in the left kidneys reaching total occlusion (group 3, n = 4). Coronal sections of the kidneys were histologically analyzed. Ease of injection, microsphere deformation, vessel sizes, and arterial distribution were assessed.

RESULTS

The injection of BRMS-I, BRMS-II, and TGMS through microcatheters went smoothly without any clogging. In group 1, BRMS identification was easier than TGMS. In group 2, both BRMS-I and TGMS were observed in all three arterial levels (interlobar, arcuate, and interlobular arteries) without a significant difference (P = .84). BRMS-I were not significantly different from TGMS in the mean diameter of vessels occluded (197 µm ± 23 vs 158 µm ± 21, P = .25) or the microsphere deformation (8.85% ± 0.53% vs 11.80% ± 0.64%, P = .071). In group 3, the arterial distribution of BRMS-II was significantly different from BRMS-I and TGMS (P < .0001).

CONCLUSIONS

In occluding arteries, 100-300 µm BRMS-I were not significantly different from 100-300 µm TGMS. Arterial distribution of BRMS can be influenced by their cross-linking density.

The old and new: PCCs, VIIa, and long-lasting clotting factors for hemophilia and other bleeding disorders

What is the correct use of established clotting factors, prothrombin complex concentrates (PCCs), and activated factor VII in bleeding complications of trauma, surgery, and old and new oral anticoagulants? How will new clotting factors, specifically the long-acting factors, change the hemostatic management of coagulation deficiency disorders? From bench to bedside, comparative coagulation studies and clinical trials of modified clotting factors are providing insights to help guide hemostatic management of congenital and acquired bleeding disorders. Comparative thrombin-generation studies and preclinical and clinical trials suggest that PCCs and fresh-frozen plasma are effective in reversing the anticoagulant effects of warfarin, yet there are few data to guide reversal of the new oral anticoagulants dabigatran and rivaroxaban. Although coagulation studies support the use of PCCs to reverse new oral anticoagulants, correlation with clinical response is variable and clinical trials in bleeding patients are needed. For congenital bleeding disorders, exciting new technologies are emerging from the bench. Data from clinical trials of molecularly modified coagulation factors with extended half-lives suggest the possibility of fewer infusions, reduced bleeds, and better quality of life in persons with hemophilia. Preclinical studies of other novel prohemostatic approaches for hemophilia and other congenital coagulation disorders include RNA interference silencing of antithrombin, monoclonal anti-tissue factor pathway inhibitor (anti-antibody, anti-tissue factor pathway inhibitor) aptamer, bispecific anti-IXa/X antibody, and fucoidans. Understanding the comparative coagulation studies of established prohemostatic agents, the pharmacokinetics of new long-acting clotting factors, and their correlation with bleeding outcomes will provide opportunities to optimize the hemostatic management of both congenital and acquired hemostatic disorders.

Human target validation of phosphoinositide 3-kinase (PI3K)β: effects on platelets and insulin sensitivity, using AZD6482 a novel PI3Kβ inhibitor

BACKGROUND

Based on in vitro and animal data, PI3Kβ is given an important role in platelet adhesion and aggregation but its role in insulin signaling is unclear.

OBJECTIVE

To strengthen the PI3Kβ target validation using the novel, short-acting inhibitor AZD6482.

METHODS AND RESULTS

AZD6482 is a potent, selective and ATP competitive PI3Kβ inhibitor (IC(50) 0.01 μm). A maximal anti-platelet effect was achieved at 1 μm in the in vitro and ex vivo tests both in dog and in man. In dog, in vivo AZD6482 produced a complete anti-thrombotic effect without an increased bleeding time or blood loss. AZD6482 was well tolerated in healthy volunteers during a 3-h infusion. The ex vivo anti-platelet effect and minimal bleeding time prolongation in the dog model translated well to data obtained in healthy volunteers. AZD6482 inhibited insulin-induced human adipocyte glucose uptake in vitro (IC(50) of 4.4 μm). In the euglycemic hyperinsulinemic clamp model, in rats, glucose infusion rate was not affected at 2.3 μm but reduced by about 60% at a plasma exposure of 27 μm. In man, the homeostasis model analysis (HOMA) index increased by about 10-20% at the highest plasma concentration of 5.3 μm.

CONCLUSIONS

This is the first human target validation for PI3Kβ inhibition as anti-platelet therapy showing a mild and generalized antiplatelet effect attenuating but not completely inhibiting multiple signaling pathways with an impressive separation towards primary hemostasis. AZD6482 at 'supratherapeutic' plasma concentrations may attenuate insulin signaling, most likely through PI3Kα inhibition.

Improved kinetics of rIX-FP, a recombinant fusion protein linking factor IX with albumin, in cynomolgus monkeys and hemophilia B dogs

BACKGROUND

Prophylaxis of hemophilia B, at present, requires multiple infusions of human factor (F)IX concentrates per week. A FIX molecule with a prolonged half-life has the potential to greatly improve the convenience of, and adherence to, prophylaxis.

OBJECTIVES

The aim of our studies was to investigate the pharmacokinetic (PK) and pharmacodynamic (PD) profile of a recombinant fusion protein linking coagulation FIX with albumin (rIX-FP).

METHODS

Cynomolgus monkeys and hemophilia B dogs received single intravenous doses of rIX-FP (50-500 IU kg(-1)). rIX-FP plasma levels were determined by an activity-based assay (dogs only) and anti-FIX ELISA methods. Additionally, activated partial thromboplastin time (APTT) was determined in hemophilia B dogs. Data were compared with a direct study comparator (recombinant FIX [rFIX]) or previously published data.

RESULTS

The terminal half-life of rIX-FP was prolonged in both species compared with FIX reference data. In hemophilia B dogs, human FIX antigen levels remained above 0.05 IU mL(-1) more than three times longer after rIX-FP (7.3 days) compared with rFIX (2.3 days), whereas respective calculations based on activity levels confirmed the observed superior profile. Prolonged PDs of rIX-FP were demonstrated with APTT<60 s sustained around four times longer with rIX-FP (5.9 days) than rFIX (1.5 days).

CONCLUSIONS

These studies indicate that the recombinant albumin fusion technology successfully improves the PK profile of FIX. Clinical studies will test whether the improved kinetics result in a significant half-life extension in patients with hemophilia B.

Relative antithrombotic and antihemostatic effects of protein C activator versus low-molecular-weight heparin in primates

The anticoagulant and anti-inflammatory enzyme, activated protein C (APC), naturally controls thrombosis without affecting hemostasis. We therefore evaluated whether the integrity of primary hemostasis was preserved during limited pharmacological antithrombotic protein C activator (PCA) treatment in baboons. The double-mutant thrombin (Trp215Ala/Glu217Ala) with less than 1% procoagulant activity was used as a relatively selective PCA and compared with systemic anticoagulation by APC and low-molecular-weight heparin (LMWH) at doses that inhibited fibrin deposition on thrombogenic segments of arteriovenous shunts. As expected, both systemic anticoagulants, APC (0.028 or 0.222 mg/kg for 70 minutes) and LMWH (0.325 to 2.6 mg/kg for 70 minutes), were antithrombotic and prolonged the template bleeding time. In contrast, PCA at doses (0.0021 to 0.0083 mg/kg for 70 minutes) that had antithrombotic effects comparable with LMWH did not demonstrably impair primary hemostasis. PCA bound to platelets and leukocytes, and accumulated in thrombi. APC infusion at higher circulating APC levels was less antithrombotic than PCA infusion at lower circulating APC levels. The observed dissociation of antithrombotic and antihemostatic effects during PCA infusion thus appeared to emulate the physiological regulation of intravascular blood coagulation (thrombosis) by the endogenous protein C system. Our data suggest that limited pharmacological protein C activation might exhibit considerable thrombosis specificity.

Plasma pharmacokinetics of desmopressin following sublingual administration: an exploratory dose-escalation study in healthy male volunteers

OBJECTIVE

Desmopressin is usually administered intranasally in the treatment of central diabetes insipidus or nocturnal enuresis. The sublingual administration of desmopressin is expected to be an alternative to the intranasal route with advantages to children and to patients with allergic rhinitis or chronic rhinosinusitis. Therefore, the present study was carried out to explore the time-versus-concentration profile of desmopressin in plasma after sublingual administration to healthy volunteers.

SUBJECTS AND METHODS

A total of 16 healthy male volunteers were enrolled in this open, exploratory, 1-period, randomized, dose-escalation study. Volunteers received a single sublingual dose of either 20, 40, 80, 160, 240 or 320 microg of desmopressin acetate. Desmopressin plasma concentrations were measured over a 12-hour period using a validated radioimmunoassay method. Safety and tolerability were assessed simultaneously.

RESULTS

Plasma concentrations of desmopressin were below the lower limit of quantification (LLOQ) of 5 pg/ml for doses lower than 80 microg. For the doses of 160 - 320 microg the time-versus-concentration profiles were higher than the LLOQ. The area under the curve from 0 - 12 h (AUC0-12h) was 54.66 +/- 25.92 pg x h/ml after the 160 microg dose, 104.38 +/- 79.10 pg x h/ml following the 240 microg dose and 133.18 +/- 181.84 pg x h/ml following the 320 microg dose. Given the data from previous experiments, the time-versus-concentration profile of desmopressin in plasma after a sublingual dose of 240 microg appeared to be in the range of previously published data on an intranasal dose of 20 microg. Sublingual administration of desmopressin proved to be safe and was well tolerated by all volunteers.

CONCLUSION

A very high inter-individual variability in desmopressin plasma concentrations was detected after sublingual administration. A sublingual dose of 240 microg of desmopressin appeared to result in a pharmacokinetic profile comparable to 20 microg administered intranasally. These data, however, need to be verified in a separate well-designed prospective clinical study.

Oral absorption of ginsenoside Rb1 using in vitro and in vivo models

This research attempts to clarify the cause for poor oral absorption of ginsenoside Rb1 (Rb1), one main ingredient of the well known Panax notoginseng saponins (PNS) for curing hemorrhage. Caco-2 cell monolayers were used as an in vitro model to reveal the transport mechanism of Rb1 across the intestinal mucosa. Moreover, the serum concentration-time profiles of Rb1 after tail venous (IV), portal venous (PV), intraduodenal (ID) and peroral (PO) administration to rats were compared to evaluate the first-pass effects of stomach, intestine and liver. In vitro experiments showed that uptake by Caco-2 cell monolayers was temperature dependent, but was not influenced by cyclosporine A and ketoconazole. The change in the apical pH showed no obvious effects on the uptake of Rb1. The uptake and transport were non-saturable, and flux from the apical compartment to the basolateral compartment (A-B) increased linearly with increasing concentration, which indicated a passive transport. Meanwhile, an apparent permeability coefficient of (5.90 +/- 1.02) x 10(-8) cm/s (C0 = 1 mg/mL) predicted an incomplete absorption. The investigation on the pharmacokinetic behavior of Rb1 after different routes of administration to rats showed a significant difference between PO (F(PO) was 0.64%), ID (F(ID) was 2.46%) and PV (F(PV) was 59.49%) administration, and the first-pass effect of the intestine is more significant than that of the stomach and liver in the absorption process. In summary, elimination in the stomach, large intestine and liver contributed to the poor absorption of Rb1, but the low membrane permeability might be a more important factor dominating the extent of absorption.

Hemostatic Effects of Phospholipid Vesicles Carrying Fibrinogen γ Chain Dodecapeptide in Vitro and in Vivo

We studied prototypes of platelet substitutes that bear on their surface a dodecapeptide, HHLGGAKQAGDV (H12). The peptide is a fibrinogen gamma chain carboxy-terminal sequence (gamma400-411) and recognizes specifically the active form of glycoprotein (GP) IIb/IIIa on the surface of activated platelets. We conjugated H12 to the end of poly(ethylene glycol) chains on the surface of a phospholipid vesicle with an average diameter of 220 nm to prepare H12-PEG-vesicles. The half-life of the H12-PEG-vesicles was significantly prolonged by PEG modification, and the ability of H12 on the surface of the vesicle to recognize GPIIb/IIIa was maintained even though the surface was modified with PEG chains. The H12-PEG-veiscles enhanced the in vitro thrombus formation of platelets that were adhering to a collagen-immobilized plate, when thrombocytopenia-imitation blood was passed over the plate. Based on the flow cytometric analyses of PAC-1 binding and P-selectin expression, the H12-PEG-vesicles were shown not to cause platelet activation. Furthermore, the H12-PEG-vesicles dose-dependently shortened the tail bleeding time of thrombocytopenic rats. It was confirmed that the H12-PEG-vesicles had a hemostatic effect and may be a suitable candidate for an alternative to human platelet concentrates transfused into thrombocytopenic patients.

Novel delivery of oligonucleotides using a topical hydrogel tissue sealant in a murine partial nephrectomy model

PURPOSE

Ischemia/reperfusion injury is a leading cause of renal damage and antisense gene therapy has been shown to ameliorate its effects. However, this approach has been limited by current delivery methods that require high concentrations of intravenous nucleic acids lacking specificity for targeting tissues. To overcome these limitations we developed a novel murine partial nephrectomy model to evaluate polyethylene-glycol (PEG) hydrogel tissue sealant as a topical oligonucleotide delivery system.

MATERIALS AND METHODS

A total of 18 male C57BL/6 mice underwent left partial nephrectomy with vascular occlusion. Hydrogel primer and then sealant were applied to the cut surface and photopolymerized. Using this method 16 additional mice received hydrogel primer mixed with Cy5 labeled fluorescent oligonucleotide (10 to 100 microg). Kidneys were harvested at various time points and assessed for oligonucleotide penetration using fluorescence microscopy.

RESULTS

A survival rate of 100% (34 subjects) was obtained using this mouse model of partial nephrectomy. PEG hydrogel provided adequate protection against renal hematoma and intraperitoneal blood. Fluorescent images revealed that 50 microg was the minimum dose resulting in complete progressive cellular penetration with time. In addition to direct diffusion from the application site, movement of oligonucleotide through the subcapsular space into the cortex was an observed mechanism of distribution.

CONCLUSIONS

A murine partial nephrectomy model was successfully created using PEG hydrogel. In addition to achieving hemostasis, hydrogel served as a successful depot for delivering oligonucleotides throughout the kidney.

A pharmacokinetic and pharmacodynamic study of desmopressin: evaluating sex differences and the effect of pre-treatment with piroxicam, and further validation of an indirect response model

Desmopressin is a synthetic vasopressin analogue mainly used in treatment of diabetes insipidus and nocturia. Studies in rats have revealed a sex difference in the response to a vasopressin infusion, which was diminished after treatment with an NSAID. This study was performed in man to investigate the influence of sex and concomitant treatment of piroxicam on the pharmacokinetics and dynamics of desmopressin, and to validate a previously described indirect response model. Eight healthy males and eight healthy females participated in the trial, which was conducted in a pharmacokinetic (PK) part followed by a pharmacodynamic (PD) part. Desmopressin was administered intravenously as a single dose (PK = dose 2 microg, PD = dose 0.2 microg). Piroxicam was administered to achieve steady state. The pharmacokinetic parameters of desmopressin were estimated and calculated by means of two-compartmental analysis. In the dynamic part a study design based on an oral hydration model was used. Parameters for urine flow and urine osmolality were estimated. Individual estimates of the pharmacokinetic parameters served as input to the indirect response model that subsequently was fitted to urine osmolality data. The pharmacokinetics of desmopressin after a fixed bolus injection was neither influenced by piroxicam nor sex of the subject. The pharmacodynamics of desmopressin showed a sex difference where females exhibited a more pronounced antidiuretic effect than males, which was statistically significant when the effects were submaximal (>4.5 h after dose). The sex differences were diminished after pre-treatment with piroxicam, indicating a prostaglandin PGE(2)-mediated mechanism. The indirect response model was confirmed, although the modelling could not distinguish a sex difference, indicating a limitation of this model compared with traditional descriptive statistics.

The effect of silver nitrate on nasal septal cartilage

Epistaxis from the anterior septum is frequently treated with a topical application of silver nitrate, which cauterizes the bleeding vessel. However, this treatment causes a septal perforation in a small percentage of patients. We report our study of the histologic effect of topical silver nitrate on samples of septal tissue obtained from 11 patients. We found that 30 seconds of exposure allowed silver nitrate to penetrate to a depth of approximately 1 mm. Longer exposure (45 and 60 sec) resulted in no significant additional penetration. Similarly, the amount of silver nitrate deposition into the chondrocytic lacunae did not vary significantly with the length of exposure. On the other hand, the depth of deposition into the extracellular matrix was positively associated with the duration of exposure. We found no direct evidence that silver nitrate exerted any damaging effect on septal cartilage. Instead, the development of septal perforations in patients who receive topical silver nitrate may be attributable to necrosis of the septal cartilage following damage to the overlying perichondrium, from which it derives its blood supply.

Effect of acyl chains of phosphatidylcholines on the pharmacokinetics of menatetrenone incorporated in O/W lipid emulsions prepared with phosphatidylcholines and soybean oil in rats

Oil-in-water (O/W) lipid emulsions were prepared with phosphatidylcholines (PCs) of various acyl chains and soybean oil (SO) using a microfluidizer system, and the pharmacokinetics of menatetrenone incorporated in these oil particles were examined at the clinical injection volume (0.1 mL kg(-1)) in rats. The plasma half-life of menatetrenone incorporated in the oil particles prepared with SO and dipalmitoylphosphatidylcholine (DPPC) (SO/DPPC) was longer than that prepared with SO and eggyolk phosphatides (EYP) (SO/EYP) by 3 fold, while those of menatetrenone as oil particles prepared with SO and either dilauroyl phosphatidylcholine (DLPC), dimyristoyl phosphatidylcholine (DMPC), distearoyl phosphatidylcholine (DSPC), dioleoyl phosphatidylcholine (DOPC) or dilinoleoyl phosphatidylcholine (DLoPC) (SO/DLPC, SO/DMPC, SO/DSPC, SO/DOPC and SO/DLoPC, respectively) were similar to that of menatetrenone as SO/EYP. The menatetrenone uptake by the liver was not significantly different from that as SO/EYP in all SO/PCs examined, but the menatetrenone uptake by the spleen as SO/DPPC and SO/DSPC was higher than that as SO/EYP. The menatetrenone uptake by the lungs as SO/DPPC was also higher than that as SO/EYP. These findings suggest that SO/DPPC is a good candidate drug carrier for the prolonged plasma circulation of lipophilic drugs.

Prolonged circulation of menatetrenone by emulsions with hydrogenated castor oils in rats

Previously, we reported that plasma half-lives of a drug incorporated in lipid emulsions prepared with soybean oil (SO), a long-chain triglyceride, and hydrogenated castor oils (HCOs) (SO/HCOs) were markedly longer, while those as SO/polyoxyethylene sorbitan esters (SO/PSs) were similar, compared to that as SO/egg yolk phosphatides (SO/EYP) [J. Pharm. Pharmacol. 54 (2002) 1357; J. Drug Target. 11 (2003) 37]. In the present study, lipid emulsions were prepared with Miglyol 812 (MO), a medium-chain triglyceride, and HCOs, and the kinetics of the incorporated drug, menatetrenone, were examined. The plasma half-lives and the liver uptake of menatetrenone as MO/polyoxyethylene-(10)-hydrogenated castor oils (MO/HCO10s) were similar to and larger than those as MO/EYP, respectively. On the other hand, the plasma half-lives and liver uptake of menatetrenone as MO/polyoxyethylene-(20)-hydrogenated castor oils (MO/HCO20s) or MO/polyoxyethylene-(60)-hydrogenated castor oils (MO/HCO60s) were markedly longer and lower than those as MO/EYP, respectively. The pretreatment of dextran sulfate 500,000, a reticuloendothelial system suppressor, raised the plasma concentration and inhibited liver uptake of menatetrenone as MO/HCO10, but not for MO/HCO20. These findings suggest that the minimum number of oxyethylene units within HCOs for the prolonged plasma circulation of menatetrenone was 20 for MO/HCOs, similarly to SO/HCOs.

Tissue-Specific Utilization of Menaquinone-4 Results in the Prevention of Arterial Calcification in Warfarin-Treated Rats

The effects of vitamin K (phylloquinone: K1 and menaquinone-4: MK-4) on vascular calcification and their utilization in the arterial vessel wall were compared in the warfarin-treated rat model for arterial calcification. Warfarin-treated rats were fed diets containing K1, MK-4, or both. Both K1 and MK-4 are cofactors for the endoplasmic reticulum enzyme gamma-glutamyl carboxylase but have a structurally different aliphatic side chain. Despite their similar in vitro cofactor activity we show that MK-4 and not K1 inhibits warfarin-induced arterial calcification. The total hepatic K1 accumulation was threefold higher than that of MK-4, whereas aortic MK-4 was three times that of K1. The utilization of K1 and MK-4 in various tissues was estimated by calculating the ratios between accumulated quinone and epoxide species. K1 and MK-4 were both equally utilized in the liver, but the aorta showed a more efficient utilization of MK-4. Therefore, the observed differences between K1 and MK-4 with respect to inhibition of arterial calcification may be explained by both differences in their tissue bioavailability and cofactor utilization in the reductase/carboxylase reaction. An alternative explanation may come from an as yet hypothetical function of the geranylgeranyl side chain of MK-4, which is a structural analogue of geranylgeranyl pyrophosphate and could interfere with a critical step in the mevalonate pathway.

Increased clearance of von Willebrand factor antigen post-DDAVP in Type 1 von Willebrand disease: is it a potential pathogenic process?

The mechanism of von Willebrand factor (VWF) clearance is not fully understood. The factors that affect VWF clearance, and the normal in vivo mechanism of clearance, may be relevant to the pathogenesis of Type 1 von Willebrand disease (VWD), in which there is a partial deficiency of VWF. In order to investigate the clearance of VWF in Type 1 VWD, the current study assessed the half-life of VWF antigen (t(1/2) VWF:Ag) in Type 1 VWD patients and individuals with mild hemophilia A following the administration of 1-deamino-8-d-arginine vasopressin (DDAVP; desmopressin). To date 20 individuals have been assessed, 13 with Type 1 VWD and seven with mild hemophilia A. The median t(1/2) VWF:Ag in the Type 1 VWD and mild hemophilia A groups were 4.6 h and 9.5 h, respectively. The difference between the t(1/2) VWF:Ag for the two groups was significant, P < 0.02. Analysis of the data showed a correlation between the t(1/2) VWF:Ag and the baseline VWF:Ag level prior to administration of DDAVP: lower baseline VWF:Ag levels were associated with a shorter t(1/2) VWF:Ag. These data suggest that increased clearance of VWF may be the pathogenic mechanism in some cases of Type 1 VWD.

Aprotinin: antifibrinolytic and anti-inflammatory mechanisms of action in cardiac surgery with cardiopulmonary bypass

Cardiopulmonary bypass results in activation of the coagulation, fibrinolytic, inflammatory, and complement cascades. These activated cascades result in a decrease in the number of circulating coagulation factors, hyperfibrinolysis, thrombocytopenia, platelet defects, coagulopathies, and an acute inflammatory response. Patients experiencing cardiac surgery with cardiopulmonary bypass are at risk for many potential problems. The use of aprotinin, an antifibrinolytic agent, has multiple effects that tend to reduce hematological defects and blunts the inflammatory response that is associated with cardiac surgery. The pathophysiological consequences of cellular activation associated with cardiopulmonary bypass, basic mechanisms of action of aprotinin, pharmacodynamic and pharmacokinetic properties, dosing, adverse reactions, and cost/benefit ratio are discussed in this article. Critical care nurses need to know about aprotinin to understand its role in reducing blood loss and transfusions during and after cardiac surgery.

Post-mortem analysis of formic acid disposition in acute methanol intoxication

Fifteen cases of fatal massive methanol intoxication have been investigated. Victims received either no treatment or ethanol therapeutic treatment. Methanol poisoning cases were classified in three groups according to survival time: more than 3 days (group 1), up to 3 days (group 2) and few hours (group 3). Body distribution of methanol and formic acid, as the main metabolite, was analyzed in blood and in different organs (brain, kidney, lung and liver). Relationships between formic acid concentration in the different tissues, survival time and type of treatment applied to victims were studied. Formic acid in blood and tissues was analyzed by head space gas chromatography (head space-GC) with FID detector, previous transformation in methyl formate, essentially as described by Abolin. Formic acid concentration was between 0.03 and 1.10g/l in the samples under study. A good correlation between blood and brain, but poor between blood and the remaining tissues was found. Obtained data suggested that the use of blood and brain could help to improve the analysis of formic acid intoxication. The best correlation among organs was found between lung and kidney for all groups (r(2)=0.91, 0.84 and 0.87, corresponding to groups 1, 2 and 3, respectively). Lethality index was defined as LI = (concentration of formic acid in blood in (g/l)/0.5) x 100, taking into account that 0.5g/l is the concentration reported by Mahieu in severe methanol poisoning. LI parameter was used to estimate formic acid incidence on the lethality of methanol poisoning cases. LI showed a good correlation with total formic acid concentration of the different tissues analyzed (r(2)=0.80). Furthermore, LI allowed us to discriminate between individuals that received therapeutic treatment and survived different periods. LI>100 indicated a severe intoxication and short survival time if the victim was assisted with ethanol therapy and hemodialysis was not applied. With regard to victims who received no therapeutic treatment and died in few hours, LI was in the range 40-100. LI was below 40 for individuals that survived more than 3 days and hemodialysis was not performed. Results showed the importance of performing formic acid analysis to diagnose severe methanol intoxication in post-mortem cases.

A prospective study of recombinant activated factor VII administered by continuous infusion to inhibitor patients undergoing elective major orthopaedic surgery: a pharmacokinetic and efficacy evaluation

After surgery in haemophilia, haemostasis is difficult to maintain in the presence of an antifactor VIII antibody. This study assessed the pharmacokinetics of recombinant activated factor VII (rFVIIa) and its efficacy in securing post-operative haemostasis in haemophiliacs with inhibitors. Continuous infusion of rFVIIa was evaluated for elective major orthopaedic surgery in nine patients with neutralizing antibodies to FVIII and at high risk of bleeding. After an initial preoperative bolus of 90 micro g/kg, rFVIIa was infused at a fixed rate of 50 micro g/kg/h for a median of 20 d (range 7-20 d). The median plasma FVII coagulant activity (FVII:C) at 24 h, 72 h and 20 d after surgery was 38 IU/ml (range 22-169 IU/ml), 45 IU/ml (range 17-88 IU/ml) and 31 IU/ml (range 27-46 IU/ml) respectively. The median plasma FVIIa:C at the same time points was 51 (range 24-211), 63 (range 22-99) and 44 (range 28-76) IU/ml respectively. Median total rFVIIa clearance remained stable during the rFVIIa continuous infusion period and was 40 (range 9-70), 34 (range 17-86) and 48 (range 32-55)ml/kg/h at the end of 24 h, 72 h and 20 d infusion respectively. Post-operatively, there were bleeds in six patients, which settled readily after a single bolus of rFVIIa (60 micro g/kg). There was a good clinical outcome for all patients. These data indicate that rFVIIa infusion at 50 micro g/kg/h achieves continuous plasma FVII procoagulant activity in excess of 30 IU/ml (12-15 nmol/l) and provides adequate haemostatic control for inhibitor patients during major orthopaedic surgery.

The effect on the middle-ear cavity of an absorbable gelatine sponge alone and with corticosteroids

The objectives of this study were to establish whether there is an obvious difference between intact mucosa and abraded mucosa of the middle-ear cavity in respect to the potential side effects from the application of absorbable gelatine sponge (Gelfoam) and to investigate if Gelfoam combined with corticosteroid ointment (cortimycine, sterile 1% hydrocortisone acetate) can reduce the occurrence of these effects. Twenty Albino rats were used in the study. These animals were divided into four groups, with ten ears in each group. In group A, the middle-ear mucosa was kept intact, and Gelfoam was inserted into the middle-ear cavity. In group B, the middle-ear mucosa was abraded, and Gelfoam was inserted. In group C, Gelfoam with corticosteroid was implanted over the intact mucosa, and in group D, the mucosa was abraded prior to the insertion of Gelfoam with corticosteroid. The changes were evaluated 8 weeks postoperatively. In group A, there was a minimal increase in fibroblastic activity, vascular proliferation with mild to moderate fibrosis and all but two tympanic membranes were perfectly normal. However, in group B, we encountered a significant increase in fibroblastic activity, vascular proliferation and fibrosis, and we observed that all tympanic membranes were moderately to severely thickened. These histopathologic changes related to Gelfoam were noted to be decreased in group C and especially in group D. As previously reported in the literature, Gelfoam was found to promote the formation of connective tissue in the middle-ear cavity regardless of the status of the mucosa. The unwanted effects of this material may be decreased if it is combined with corticosteroids in the middle-ear cavity.

Formate-stimulated NaCl absorption in the proximal tubule is independent of the pendrin protein

A significant fraction of active chloride reabsorption across the apical membrane of the proximal tubule is mediated by a chloride/formate exchange process, whereby intracellular formate drives the transport of chloride into the cell. When chloride/formate exchange operates in parallel with Na(+)/H(+) exchange and H(+)-coupled recycling of formate, the net result is electroneutral NaCl reabsorption. Pendrin is the protein product of the PDS gene (SLC26A4) and functions in several different anion exchange modes, including chloride/formate exchange. Pendrin is expressed in the kidney and may serve as the transporter responsible for formate-dependent NaCl reabsorption. In the present study, Pds-knockout mice were used to determine the role of pendrin in proximal tubule chloride reabsorption. We show that formate-dependent NaCl absorption in microperfused proximal tubules is similar between wild-type and pendrin-deficient mice. In addition, there is no difference in the rate of formate-mediated chloride transport in brush-border membrane vesicles isolated from wild-type and pendrin-deficient mice. These studies demonstrate that pendrin is not responsible for formate-dependent NaCl reabsorption in the proximal tubule.

Effect of oxyethylene moiety in polyoxyethylene sorbitan esters on the pharmacokinetics of menatetrenone incorporated in O/W lipid emulsions prepared with polyoxyethylene sorbitan esters and soybean oil in rats

Oil-in-water (O/W) lipid emulsions are suitable drug carriers for lipophilic drugs; however, the effects of numbers or chains of oxyethylene units within a surfactant molecule such as polyoxyethylene sorbitan esters (PSs) on the biological fate of these lipid emulsions have not yet been clarified. In this study, a series of PSs and soybean oil (SO) were utilized to prepare menatetrenone-incorporated lipid emulsions (SO/PSs), and the biological fate of menatetrenone administered as SO/PSs was studied at a clinical injection volume (0.1 mL kg(-1)) in rats. The plasma concentration and organ uptake of menatetrenone administered as SO/20OE-PSs (PSs with 20 oxyethylene units) was similar to that of SO/egg-yolk phosphatides (SO/EYP). The plasma concentration of menatetrenone was extensively lower for SO/6OE-PSs (PSs with 6 oxyethylene units) and SO/20OE-3FA-PSs (PSs with 20 oxyethylene units and 3 fatty acid chains) than that for SO/EYP, and menatetrenone uptake by the liver and spleen was higher for SO/6OE-PSs and SO/20OE-3FA-PSs, respectively, than those for SO/EYP. Furthermore, menatetrenone uptake by the lungs was also increased for SO/6OE-PS and SO/20OE-3FA-PS with double bonds in the fatty acid moieties of the PSs. These findings suggested that shortening the oxyethylene units or decreasing the oxyethylene chain numbers of emulsifiers resulted in a rapid clearance of the lipid emulsions from the circulation by extensive uptake via the liver, spleen or lungs.

Evaluation of high concentration intranasal and intravenous desmopressin in pediatric patients with mild hemophilia A or mild-to-moderate type 1 von Willebrand disease

OBJECTIVES

The objective of the study was to evaluate the safety and efficacy of high-concentration intranasal desmopressin (HCIN-DDAVP) 1.5 mg/mL, in patients weighing < or = 50 kg with mild hemophilia A or mild type 1 von Willebrand disease (VWD).

STUDY DESIGN

This was a single-center, nonrandomized, open-label, single-dose trial of HCIN-DDAVP. Nine boys with hemophilia A, 8 girls with mild VWD, and 8 boys with mild VWD were evaluated. HCIN-DDAVP responses were compared with historic IV-DDAVP responses in 13 of the patients.

RESULTS

HCIN-DDAVP administration resulted in statistically significant mean increases in factor VIII procoagulant activity, ristocetin cofactor, and von Willebrand factor antigen levels in each of the 3 study groups. Mean (+/- 1 SD) increase in factor VIII procoagulant activity was 25.7 +/- 11.9 U/dL in mild hemophilia A. Ristocetin cofactor increased 108.5 +/- 53.8 U/dL in girls and 95.8 +/- 36.0 U/dL in boys with mild VWD. Intravenous desmopressin acetate responses were comparable to HCIN-DDAVP responses in patients who received both preparations. Adverse events were mild and resolved without intervention.

CONCLUSION

We conclude that administration of 150 microg of high concentration intranasal desmopressin is safe and effective in patients weighing < or = 50 kg with mild hemophilia A or mild type 1 VWD.

Magnetic resonance imaging study of the swelling kinetics of hydroxypropylmethylcellulose (HPMC) in water

Magnetic resonance imaging has been used to monitor the hydration of hydroxypropylmethylcellulose samples by two-dimensional mapping of properties such as spin density and relaxation times. The measurements were performed at two pH values of water: 2 and 6 and two temperatures 25 and 37 degrees C. It is shown that transport behavior of water into HPMC changes from being almost completely relaxation controlled (case II) at pH=2 to Fickian behavior for pH=6. It was also observed that radial swelling is larger for the system composed of HPMC and water at pH=6 than at pH=2.

A study of a weight-adjusted aprotinin dosing schedule during cardiac surgery

Aprotinin is effective during cardiac surgery for reducing blood loss and transfusion requirements, but it is expensive. Aprotinin is usually administered to adults according to a fixed protocol regardless of the patient's weight. We previously developed a weight-based dosing protocol for aprotinin. The purpose of this prospective observational study was to determine aprotinin levels in four patient groups (n = 10 each) using the new weight-based aprotinin dosing schedule that should achieve concentrations over 100, 150, 200, and 250 kallikrein inhibitory units/mL compared with full-dose aprotinin regimen (n = 10) by a simple functional aprotinin assay. There was no difference in patient demographic or surgical variables among groups. There was less within patient variation in plasma aprotinin concentrations over time in the new weight-based aprotinin dosing schedule groups compared with the full-dose aprotinin regimen group (P < 0.02 for all comparisons). The mean plasma aprotinin concentration achieved with the new weight-based aprotinin dosing schedule was similar to the desired concentrations, but we were unable to reduce between-patient variability in aprotinin concentrations.

IMPLICATIONS

The current dosing schedule for aprotinin results in a large variation in aprotinin plasma concentrations between patients and a large variation within each patient over time. A new weight-based dosing schedule reduced variation of aprotinin concentration over time, but was unable to reduce between-patient variability in aprotinin concentration.

Is perioperative plasma aprotinin concentration more predictable and constant after a weight-related dose regimen?

To determine whether a weight-related dose had advantages over a fixed, large-dose regimen, we measured plasma concentrations of aprotinin by using an enzyme-linked immunosorbent assay method at set time points in 30 patients having heart surgery with cardiopulmonary bypass. A weight-related dose comprising a preincision bolus injection of 40,000 kallikrein-inhibiting units (KIU)/kg (5.6 mg/kg) with the same amount given in the oxygenator prime was compared with a large-dose regimen of 2 x 10(6) KIU (280 mg) preincision bolus and addition to prime, together with an infusion of 500,000 KIU/h (70 mg/h). Peak plasma concentration in the Weight-Related group was less variable than with the fixed-dose regimen. Forty percent of patients allocated to the fixed-dose regimen had an aprotinin concentration of more than 400 KIU/mL, compared with none in the Weight-Related group; this suggests a relative overdosing in the early surgical period in the Fixed-Dose group. There was great individual variability between patients in the time-concentration curves for aprotinin, with no difference between the two regimens. The weight-related dose regimen benefited by not requiring an intraoperative infusion while achieving the same plasma concentrations of aprotinin.

IMPLICATIONS

Peak plasma concentrations of aprotinin were less variable with a weight-related dose schedule. This has implications for safety with regard to control of anticoagulation and cost in patients with small body mass. Plasma concentrations varied greatly with time between patients. This observation has implications for determining an optimal dose on the basis of aprotinin's currently known mechanisms of action.

The impact of renal dysfunction on aprotinin pharmacokinetics during cardiopulmonary bypass

Aprotinin is a serine protease inhibitor that undergoes metabolism in the kidney. Because elimination is almost entirely renal, the clearance of aprotinin may be reduced in patients with renal insufficiency. Unfortunately, there are no data regarding aprotinin pharmacokinetics in cardiac surgical patients with renal insufficiency or end-stage renal disease (ESRD) undergoing cardiopulmonary bypass (CPB). We, therefore, determined the clearance (ApCl) and elimination half-life (T1/2) of aprotinin in 26 cardiac surgical patients with normal and abnormal renal function (creatinine clearance [CrCl] 0-122 mL/min) undergoing CPB. Subjects were given a 2 million kallikrein inhibiting unit (KIU) initial dose of aprotinin, followed by a 0.25 million KIU/h infusion. No aprotinin was added to the pump prime. Plasma aprotinin concentrations were sampled at 30 min after completion of the loading dose, 30 and 60 min after the onset of CPB, at the end of CPB, and at 8, 24, and 32 h after completion of the loading dose. ApCl was directly related and the elimination T1/2 inversely related to CrCl (r = 0.75 and 0.42, respectively). In patients with a CrCl >50 mL/min, the T1/2 and ApCl were 7.8 h and 53 mL/min, respectively, compared with 19.9 h and 25 mL/min (P < 0.05, P < 0.002, respectively) for patients with ESRD. In conclusion, ApCl is reduced, and T1/2 is prolonged in patients with renal insufficiency or ESRD undergoing CPB. Dosing modifications may be necessary for patients with abnormal renal function undergoing cardiac surgery.

IMPLICATIONS

Because aprotinin is metabolized and eliminated in the kidney, its clearance may be reduced in patients with renal insufficiency. Our data suggest that aprotinin clearance is reduced, and aprotinin half-lives are prolonged in patients with renal insufficiency undergoing CPB. Dosing modification may therefore be indicated when aprotinin is administered to these patients for cardiac surgery.

Pharmacokinetics and hemostatic effects of saruplase in patients with acute myocardial infarction: comparison of infusion, single-bolus, and split-bolus administration

Saruplase, or unglycosylated, single-chain urokinase-type plasminogen activator (scu-PA) selectively activates fibrin-bound plasminogen, and is subsequently converted to its two-chain derivative tcu-PA (urokinase) by plasmin. The efficacy of a 20 mg IV bolus followed by an infusion of 60 mg over 1 hour (standard regimen) has been demonstrated in acute myocardial infarction (AMI). The Bolus Administration of Saruplase in Europe (BASE) study compared the efficacy of standard therapy, single bolus (80 mg), and split bolus (2 x 40 mg at 30-minute intervals) in AMI. In a substudy of BASE, the pharmacokinetics of total u-PA activity (amidolytic activity after plasmin treatment), high molecular weight (HMW) u-PA antigen, and tcu-PA activity were compared in patients receiving standard therapy (n = 4), single bolus (n = 4), or split bolus (n = 5). Total u-PA activity and HMW u-PA antigen were similar. The maximum concentration (C(max,), mean +/- SD) of total u-PA activity was 2.2 +/- 0.3 microg/mL after standard therapy, 16.3 +/- 3.9 microg/mL after single bolus, and 8.2 +/- 1.6 ug/mL after split bolus. The area under the concentration versus time curve (AUC) values of total u-PA activity were 1.7 +/- 0.1 microg/mL*h (standard therapy), 4.0 +/- 0.9 microg/mL*h (bolus), and 3.0 +/- 0.7 microg/mL*h (split bolus). The dominant initial half-lives (t(1/2) alpha) were 7.1 +/- 1.1 minutes (standard), 8.8 +/- 0.8 minutes (bolus), and 5.1 +/- 2.1 minutes (split bolus). Maximum plasma concentrations of of tcu-PA activity were observed at 5.2 +/- 7 minutes (standard), 21 +/- 10 minutes (bolus), and 42 +/- 2 minutes (split bolus). C(max) was lowest after standard therapy (0.6 +/- 0.3 microg/mL), highest after bolus (4.2 +/- 2.2 microg/mL), and approximately twice as high as standard therapy after split bolus (1. 3 +/- 0.8 microg/mL). After standard therapy the mean fibrinogen concentration decreased gradually from approximately 300 mg/dL to 70 mg/dL at 90 and 120 minutes. After a single bolus the fibrinogen concentration decreased below the limit of quantification within 30 minutes and remained there for at least 120 minutes. Directly after the second 40 mg dose of the split bolus, the fibrinogen levels had an accelerated and more pronounced decrease to approximately 65 mg/dL at 90 and 120 minutes. A single bolus results in very high early total u-PA activity, which accelerates the appearance of tcu-PA activity and fibrinogen consumption. The pharmacokinetics and hemostatic effects of the split-bolus regimen are more comparable with those of standard therapy.