This assay enables the pharmacodynamic and pharmacokinetic properties of bypassing therapies to be monitored, thus helping to optimize treatment.

Factor VIII (FVIII)-bypassing agents have complex modes of action but all control bleeding in inhibitor patients by triggering the generation of thrombin. No routine test is available for monitoring this therapy in patients with inhibitors against FVIII. We present an assay that records FEIBA- or FVIIa-mediated changes in thrombin generation (TG) in FVIII inhibitor plasma samples. In plasma samples spiked with FEIBA TG was normalized above 0.4 U/ml, while for recombinant FVIIa (rFVIIa) more than 12.5 µg/ml were required to induce TG in the absence of tissue factor (TF). Addition of TF increased the TG potential of rFVIIa in vitro. This assay seems suitable for monitoring the pharmacokinetics of inhibitor bypassing agents during treatment and possibly for predicting responses to treatment.

No abstract

Activated protein C (APC) is a potent physiologic anticoagulant with profibrinolytic properties, and has been shown to prevent thrombosis in different experimental models. We investigated the effect of human APC on thrombin-induced thromboembolism in mice, a model of acute intravascular fibrin deposition leading to death within minutes. APC given intravenously (i.v.) as a bolus 2 min before thrombin challenge (1,250 U/kg) reduced mortality in a dose-dependent manner despite the lack of thrombin inhibitor activity. Significant inhibition of thrombin-induced death was observed at the dose of 0.05 mg/kg, and maximal protection was obtained with 2 mg/kg (> 85% reduction in mortality rate). Histology of lung tissue revealed that APC treatment (2 mg/kg) reduced significantly vascular occlusion rate (from 89.2 to 46.6%, P < 0.01). The protective effect of APC was due to the inhibition of endogenous thrombin formation as indicated by the fact that (a) the injection of human thrombin caused a marked decrease in the coagulation factors of the intrinsic and common pathways (but not of Factor VII), suggesting the activation of blood clotting via the contact system; (b) APC pretreatment reduced markedly prothrombin consumption; (c) the lethal effect of thrombin was almost abolished when the animals were made deficient in vitamin K-dependent factors by warfarin treatment, and could be restored only by doubling the dose of thrombin, indicating that the generation of endogenous thrombin contributes significantly to death; and (d) APC failed to protect warfarin-treated animals, in which mortality is entirely due to injected thrombin, even after protein S supplementation. Other results suggest that APC protects from thrombin-induced thromboembolism by rendering the formed fibrin more susceptible to plasmin degradation rather than by reducing fibrin formation: in thrombin-treated mice, fibrinogen consumption was not inhibited by APC; and inhibition of endogenous fibrinolysis by epsilon-aminocaproic or tranexamic acid resulted in a significant reduction of the protective effect of APC. Since APC did not enhance plasma fibrinolytic activity, as assessed by the measurement of plasminogen activator (PA) or PA inhibitor (PAI) activities, PAI-1 antigen, or 125I-fibrin degrading activity, we speculate that the inhibition of additional (endogenous) thrombin formation by APC interrupts thrombin-dependent mechanisms that make fibrin clots more resistant to lysis, so that the intravascular deposited fibrin can be removed more rapidly by the endogenous fibrinolytic system.

Objectives: We aimed to evaluate the factors influencing true adult height (HT) after long-term (from 1987 to 2000) GH treatment in Ullrich -Turner syndrome (UTS) based on modalities conceived in the 1980s. Design: Out of 347 near-adult (.16 years) patients from 96 German centres, whose longitudinal growth was documented within KIGS (Pharmacia International Growth Database), 188 (45, X ¼ 59%; bone age .15 years) were available for further anthropometric measurements. Results: At a median GH dose of 0.88 (10th/90th percentiles: 0.47/1.06) IU/kg per week, a gain of 6.0 (2 1.3/+13) cm above the projected adult height was recorded. Variables were recorded at GH start, after 1 year GH, puberty onset, and last visit on GH therapy. At these visits, the median ages were 11.7, 12.7, 14.2, 16.6 and 18.7 years; and median heights, 0.4, 1.1, 1.7, 1.7 and 1.3 SDS (UTS) respectively. Height gain (DHT) after GH discontinuation was 1.5 cm. Total DHT correlated ðP , 0:001Þ negatively with bone age and HT SDS at GH start, but positively with DHT after the first year, DHT at puberty onset, and GH duration. Final HT correlated ðP , 0:001Þ positively with HT at GH start, first-year DHT, and HT at puberty onset. Body mass index increased slightly ðP , 0:05Þ; with values at start and adult follow-up correlating highly ðR ¼ 0:70; P , 0:001Þ: No major side effects of GH occurred. Conclusions: GH dosages conceived in the 1980s are safe but too low for most UTS patients. HT gain and height are determined by age and HT at GH start. Height gain during the first year on GH is indicative of overall height gain. After spontaneous or induced puberty, little gain in height occurs.