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.

OBJECTIVE: Concizumab, a humanized monoclonal antibody against tissue factor pathway inhibitor (TFPI), is being developed as a subcutaneously (s.c.) administered treatment for haemophilia. It demonstrated a concentration-dependent procoagulant effect in functional TFPI assays; however, global haemostatic assays, such as the thrombin generation assay (TGA), offer a more complete picture of coagulation. We investigated how concizumab affects thrombin generation following ex vivo spiking in plasma from haemophilia patients using the TGA, and if the assay can detect the effect of multiple s.c. concizumab doses in healthy subjects.
METHODS: For the ex vivo spiking study, platelet-poor plasma (PPP) from 18 patients with severe haemophilia was spiked with 0.001-500 nm concizumab. For the multiple-dosing study, four healthy males received concizumab 250 μg kg-1 s.c. every other day for eight doses; blood was collected before and after dosing and processed into PPP. In both studies, thrombin generation was measured using a Calibrated Automated Thrombogram® system with 1 pm tissue factor.
RESULTS: In spiked samples from haemophilia patients, peak thrombin and endogenous thrombin potential (ETP) increased concentration dependently, reaching near-normal levels at concizumab concentrations >10 nm. Repeated s.c. doses of concizumab in healthy subjects increased both peak thrombin and ETP; these effects were sustained throughout the dosing interval.
CONCLUSIONS: Thrombin generation assay demonstrated increased thrombin generation with concizumab after ex vivo spiking of haemophilia plasma and multiple s.c. doses in healthy subjects, supporting both the utility of the TGA in evaluating concizumab treatment and the potential of s.c. concizumab as a novel haemophilia therapy.

BACKGROUND: Prophylaxis with either intravenous (i.v.) factor VIII (FVIII) or FIX is the gold standard of care for patients with severe hemophilia. A monoclonal antibody (concizumab) targeting tissue factor pathway inhibitor (TFPI) that can be administered subcutaneously (s.c.) has the potential to alter current concepts of prophylaxis in hemophilia.
OBJECTIVE: To evaluate the safety and describe the pharmacokinetics and pharmacodynamics of single-dose concizumab in healthy volunteers and patients with hemophilia A or B.
METHODS: In this first human dose, phase 1, multicenter, randomized, double-blind, placebo-controlled trial escalating single i.v. (0.5-9000 μg kg(-1) ) or s.c. (50-3000 μg kg(-1) ) doses of concizumab were administered to healthy volunteers (n = 28) and hemophilia patients (n = 24).
RESULTS: Concizumab had a favorable safety profile after single i.v. or s.c. administration. There were no serious adverse events and no anti-concizumab antibodies. No clinically relevant changes in platelets, prothrombin time, activated partial thromboplastin time, fibrinogen, or antithrombin were found. A dose-dependent procoagulant effect of concizumab was seen as increased levels of D-dimers and prothrombin fragment 1 + 2. Nonlinear pharmacokinetics of concizumab was observed due to target-mediated clearance. A maximum mean AUC0-∞ of 33 960 h μg mL(-1) and a maximum mean concentration of 247 μg mL(-1) was measured at the highest dose.
CONCLUSIONS: Concizumab showed a favorable safety profile after i.v. or s.c. administration and nonlinear pharmacokinetics was observed due to target-mediated clearance. A concentration-dependent procoagulant effect of concizumab was observed, supporting further study into the potential use of s.c. concizumab for hemophilia treatment.

BACKGROUND: Concizumab (mAb 2021) is a monoclonal IgG4 antibody (mAb) that binds to the Kunitz-type protease inhibitor (KPI) 2 domain of TFPI thereby blocking the interaction of this domain with the active site of FXa. The objective of the present study was to characterize the pharmacokinetics of concizumab in Cynomolgus monkeys after intravenous (iv) and subcutaneous (sc) administration.
METHODS: Data from two studies were included in the modelling, all in all data from 52 monkeys distributed into 9 groups. Three groups received three escalating sc doses of concizumab with a one week dosing interval, two groups were administered a single dose, and four groups received multiple doses over 13 weeks of concizumab. The plasma concentration was measured using a standard ELISA, and pharmacokinetic data were analysed using NONMEM.
RESULTS: The pharmacokinetics of concizumab were characterised by a high bioavailability (93%) after sc administration. The time course of the elimination of concizumab from the circulation was well described by the proposed target mediated drug disposition (TMDD) model. The clearance of concizumab was estimated to be 0.14 ml/h/kg, the target clearance was characterized by a 50% saturation level of 0.54 μg/ml (Km), and the clearance at target saturation was estimated to be 11 μg/h/kg.
CONCLUSIONS: Concizumab displays a typical TMDD profile with important implications for a putative treatment regime in haemophilia patients. Compared to current standard haemophilia treatment, concizumab has a high bioavailability after sc administration and may provide a viable alternative to intravenous dosing for the treatment of haemophilia.