Key Points • Rondaptivon pegol is a first-in-class prohemostatic molecule that prolongs the half-life of both endogenous FVIII and substituted FVIII.• Rondaptivon pegol could be used to enable once-weekly substitution therapy in severe hemophilia A or as prophylaxis in nonsevere hemophilia A.

Key Points The aptamer rondoraptivon pegol improved VWF/FVIII levels, multimer patterns, and thrombocytopenia in type 2B von Willebrand disease. Once weekly subcutaneous injections of rondoraptivon pegol may in the future be used for prophylaxis or treatment of VWD.

von Willebrand factor (VWF) and factor VIII (FVIII) circulate in a noncovalent complex in blood and promote primary hemostasis and clotting, respectively. A new VWF A1-domain binding aptamer, BT200, demonstrated good subcutaneous bioavailability and a long half-life in non-human primates. This first-in-human, randomized, placebo-controlled, double-blind trial tested the hypothesis that BT200 is well tolerated and has favorable pharmacokinetic and pharmacodynamic effects in 112 volunteers. Participants received one of the following: a single ascending dose of BT200 (0.18-48 mg) subcutaneously, an intravenous dose, BT200 with concomitant desmopressin or multiple doses. Pharmacokinetics were characterized, and the pharmacodynamic effects were measured by VWF levels, FVIII clotting activity, ristocetin-induced aggregation, platelet function under high shear rates, and thrombin generation. The mean half-lives ranged from 7-12 days and subcutaneous bioavailability increased dose-dependently exceeding 55% for doses of 6-48 mg. By blocking free A1 domains, BT200 dose-dependently decreased ristocetin-induced aggregation, and prolonged collagen-adenosine diphosphate and shear-induced platelet plug formation times. However, BT200 also increased VWF antigen and FVIII levels 4-fold (P<0.001), without increasing VWF propeptide levels, indicating decreased VWF/FVIII clearance. This, in turn, increased thrombin generation and accelerated clotting. Desmopressin-induced VWF/FVIII release had additive effects on a background of BT200. Tolerability and safety were generally good, but exaggerated pharmacology was seen at saturating doses. This trial identified a novel mechanism of action for BT200: BT200 dose-dependently increases VWF/FVIII by prolonging half-life at doses well below those which inhibit VWF-mediated platelet function. This novel property can be exploited therapeutically to enhance hemostasis in congenital bleeding disorders.

Abstract Background von Willebrand factor (VWF) is crucial for arterial thrombosis and its plasma levels are increased in acute coronary syndromes (ACSs). The effects of conventional platelet inhibitors are compromised by elevated VWF under high shear rates. BT200 is a third-generation aptamer that binds and inhibits the A1 domain of human VWF. This article aims to study whether VWF is a predictor of mortality in ACS patients under potent P2Y12 blocker therapy and to examine the effects of a VWF inhibiting aptamer BT200 and its concentrations required to inhibit VWF in plasma samples of patients with ACS. Methods VWF activity was measured in 320 patients with ACS, and concentration effect curves of BT200 were established in plasma pools containing different VWF concentrations. Results Median VWF activity in patients was 170% (interquartile range % confidence interval [CI]: 85–255) and 44% of patients had elevated (> 180%) VWF activity. Plasma levels of VWF activity predicted 1-year (hazard ratio [HR]: 2.68; 95% CI: 1.14–6.31; p < 0.024) and long-term (HR: 2.59; 95% CI: 1.10–6.09) mortality despite treatment with potent platelet inhibitors (dual-antiplatelet therapy with aspirin and prasugrel or ticagrelor). Although half-maximal concentrations were 0.1 to 0.2 µg/mL irrespective of baseline VWF levels, increasing concentrations (0.42–2.13 µg/mL) of BT200 were needed to lower VWF activity to < 20% of normal in plasma pools containing increasing VWF activity (p < 0.001). Conclusion VWF is a predictor of all-cause mortality in ACS patients under contemporary potent P2Y12 inhibitor therapy. BT200 effectively inhibited VWF activity in a target concentration-dependent manner.

Abstract Osteoprotegerin (OPG) regulates bone metabolism by reducing the activation of osteoclasts, but may also be involved in blood vessel calcification and atherosclerosis. Within endothelial cells OPG is stored in Weibel–Palade bodies (WPBs). Blood kinetics of OPG are essentially unknown. We aimed to assess these using two distinct in vivo models; one after stimulation with desmopressin (DDAVP) and another after stimulation with lipopolysaccharide (LPS). Both clinical trials were conducted at the Department of Clinical Pharmacology at the Medical University of Vienna, Austria. Participants received desmopressin (0.3 µg/kg), LPS (2 ng/kg), or placebo (sodium chloride 0.9%) with subsequent blood sampling at time points up to 24 hours after administration. The primary objective of this study was to investigate the plasma kinetics of OPG after stimulation with desmopressin and LPS. Secondary analyses included the release of other WPB contents including von Willebrand factor (vWF). This analysis included 31 healthy volunteers (n = 16 for desmopressin and placebo, n = 15 for LPS). Infusion of desmopressin did not increase OPG concentrations compared with placebo, while LPS infusion significantly increased OPG levels, both compared with desmopressin (p < 0.0001) and to placebo (p = 0.004), with a maximum of ∼twofold increase in OPG levels ∼6 hours after infusion. von Willebrand factor levels increased after both desmopressin and LPS infusion (p < 0.0001), with a maximum of ∼threefold increase 2 hours after desmopressin and a maximum of ∼twofold increase 6 hours after LPS administration. In conclusion, we report that, in contrast to vWF, OPG is not released upon stimulation with desmopressin, but increases significantly during experimental endotoxemia.

Background: The effect of conventional anti-platelet agents is limited in secondary stroke prevention, and their effects are further blunted under conditions of high shear stress in the presence of increased levels of circulating VWF. VWF mediates platelet adhesion to collagen under high shear stress and is thereby critically involved in thrombus formation at sites of stenotic extracranial intracranial arteries (reviewed by Buchtele et al. 2018). We have created a novel anti-VWF aptamer (BT200) which could be useful for secondary stroke prevention, because the anti-VWF aptamer ARC1779 effectively reduced cerebral embolization after carotid endarterectomy (Markus et al. 2011). Aims: To characterize the effects of BT200 in blood of patients with large artery atherosclerosis stroke. Methods: Blood samples were obtained from 30 patients with acute stroke Inhibition of VWF activity by BT200 was quantified by REAADS ELISA and VWF ristocetin cofactor activity (VWF:RCo), platelet function under high shear rates with the PFA-100, and ristocetin-induced platelet aggregation in whole blood. Results: The majority of stroke patients had elevated VWF:RCo levels (mean: 198%; range 55-330%). Of 15 patients receiving clopidogrel with or without aspirin, only two had a prolonged collagen adenosine diphosphate closure time (CADP-CT) >123s, and only one patient had a ristocetin induced aggregation of <20U. BT200 concentration dependently inhibited VWF activity to <3% and VWF dependent platelet function (p<0.001): BT200 invariably prolonged CADP-CT to target levels of >300s, and decreased aggregation to <20U in blood samples from all patients. Conclusions: BT200 effectively inhibits VWF activity and VWF-dependent platelet function in blood from patients with acute stroke. Results from this study proved useful for planning of the ongoing phase I and planned phase II trial.