Human recombinant activated protein C-coated stent for the prevention of restenosis in porcine coronary arteries.

Activated protein C (APC), an endogenous protein, inhibits inflammation and thrombosis and interrupts the coagulation cascade. Here, we investigated the effect of human recombinant APC on the development of neointimal hyperplasia in porcine coronary arteries. Yukon Choice bare metal stents were coated with 2.6 µg APC/mm(2). Under general anesthesia, APC-coated and bare stents were implanted in the left anterior descending and circumflex coronary arteries of 10 domestic pigs. During the 4-week follow-up, animals were treated with dual antiplatelet therapy and neointimal hyperplasia was evaluated via histology. Scanning electron microscopy indicated successful but unequal coating of stents with APC; nearly complete drug release occurred within 4 h. Enzyme-linked immunosorbent assay revealed that intracoronary stent implantation rapidly increased the levels of monocyte chemoattractant protein-1, an effect that was inhibited by APC release from the coated stent. Fibrin deposition and adventitial inflammation were significantly decreased 1 month after implanting APC-coated stents versus bare stents, paralleled by significantly smaller neointimal area (0.98 ± 0.92 vs. 1.44 ± 0.91 mm(2), P = 0.028), higher lumen area (3.47 ± 0.94 vs. 3.06 ± 0.91 mm(2), P = 0.046), and lower stenosis area (22.2 ± 21.2% vs. 32.1 ± 20.1%, P = 0.034). Endothelialization was complete with APC-coated but not bare (90%) stents. P-selectin immunostaining revealed significantly fewer activated endothelial cells in the neointima in the APC group (4.6 ± 1.9 vs. 11.6 ± 4.1%, P < 0.001). Thus, short exposure of coronary arteries to APC reduced inflammatory responses, neointimal proliferation, and in-stent restenosis, offering a promising therapy to improve clinical outcomes of coronary stenting. However, coating stents with APC for prolonged, controlled drug release remains technically challenging.

The effect of activated protein C on plasma cytokine levels in a porcine model of acute endotoxemia.

OBJECTIVE: To assess the anti-inflammatory effects of recombinant human activated protein C (rhAPC) in a porcine model of acute endotoxemia. DESIGN AND SETTING: Animal randomized controlled study at the Laboratory of Clinical Institute, Aarhus University Hospital. SUBJECTS: Eighteen female landrace pigs (30 kg). INTERVENTIONS: By pairwise randomization, pigs were given either LPS or LPS and rhAPC. Both groups received a stepwise increasing LPS infusion for 30[Symbol: see text]min; whereafter the infusion continued at a lower rate (300 min LPS in both groups). The LPS+rhAPC group received rhAPC (100 microg/kg per hour) 15 min before the LPS infusion began and throughout the trial period. RESULTS: While rhAPC showed no modifying effects on peak plasma levels of pro- or anti-inflammatory cytokines (TNF-alpha, IL-6, IL-8, IL-10), TNF-alpha and IL-10 peaked significantly later in the rhAPC-treated animals. The profibrinolytic effects of rhAPC were confirmed by decreased plasminogen activator inhibitor 1 levels, while no differences were found in other coagulation markers, hemodynamic, metabolic, or leukocyte data between the two groups. CONCLUSIONS: We found no significant effect of rhAPC on plasma levels of either pro- or anti-inflammatory cytokines in this porcine model of acute endotoxemia. However, TNF-alpha and IL-10 peaked significantly later in the rhAPC-treated animals.

Efficacy and safety of protein C concentrate to treat purpura fulminans and thromboembolic events in severe congenital protein C deficiency.

Severe congenital protein C (PC) deficiency (SCPCD) is associated with disseminated intravascular coagulation (DIC), purpura fulminans (PF), and vascular thromboembolic events (TE), often leading to organ failure and death. PC replacement therapy offers a safe, effective treatment for thromboembolic complications of SCPCD and secondary prophylaxis for recurrent DIC, PF, and TEs. A prospective, multi-centre, open-label, phase 2/3 study was conducted to demonstrate the safety and efficacy of protein C concentrate for treatment of PF and acute TEs. Fifteen enrolled patients with SCPCD received protein C concentrate; 11 received treatment for acute TEs (PF, 18 events; PF and other coumarin-related vascular thromboembolic events [coumarin-induced skin necrosis; CISN], 1 event; venous thrombosis, 5 events). Pre-defined efficacy criteria for treatment of acute TEs were compared with a historical control arm (i. e. patients receiving conventional therapy without protein C replacement). PF/CISN was demonstrated by pre-defined primary and secondary efficacy ratings. Primary ratings of protein C concentrate-treated episodes were significantly higher (p=0.0032) than in the historical control. For 19 PF/CISN episodes in 11 patients, 94.7 % of treatments were rated effective and 5.3 % effective with complications (not related to protein C concentrate). In a secondary efficacy rating, all treatments were rated effective (68.4 % excellent; 21.1 % good; 10.5 % fair). For 5/24 vascular thrombosis episodes, 80 % of treatments were rated excellent and 20 % were rated good. No treatment-related adverse events or serious adverse events occurred. In conclusion, protein C concentrate provides an efficacious, safe treatment for PF, CISN, and other TEs in SCPCD patients.

The effects of supra-normal protein C levels on markers of coagulation, fibrinolysis and inflammation in a human model of endotoxemia.

The protein C pathway serves as a modulating system with both anti-inflammatory and anticoagulant properties and is intimately involved in the pathophysiology of inflammation and sepsis. Treatment with recombinant human activated protein C (rhAPC) can reduce the mortality of severe sepsis. We investigated whether an elevation of plasma protein C levels to supra-normal levels by infusion of a protein C zymogen concentrate has an effect on coagulation, protein C activation or inflammation in a human endotoxemia model. Eleven healthy male volunteers were enrolled in a double-blind, placebo-controlled two-way cross-over trial. Ten minutes after infusion of 2ng/kg endotoxin each volunteer received either placebo or a plasma-derived protein C zymogen concentrate (Ceprotin, Baxter) (150 U/kg as a slow bolus infusion followed by 30 U/kg/h continuous infusion until 4 hours after LPS-infusion). Protein C antigen and activity increased 4- to 5-fold after infusion of the concentrate. APC was generated during endotoxin-induced inflammation in the placebo (1.6 fold increase) and the protein C period (4.0-fold increase). The increase of APC levels correlated with the TNF-alpha and IL-6 release in both periods (r = 0.65-0.68; p < 0.05) and paralleled the protein C antigen and activity levels in the period with supranormal protein C levels. Supra normal protein C levels resulted in slightly, although non-significant, lower tissue factor mRNA expression and thrombin generation (TAT, F1+2). Systemic inflammation (TNF-alpha, IL-6) was not influenced by protein C zymogen concentrate administration. Infusion of protein C zymogen was safe and no adverse effects occurred. The increase of protein C levels several fold above the normal range resulted in a proportional increase of the APC levels, but had no major anticoagulant, anti-inflammatory or profibrinolytic effects. Low grade endotoxemia itself induces significant protein C activation, which correlates with the TNF release.

Modeling behavior of protein C during and after subcutaneous administration.

Protein C is an important blood factor protein that regulates the blood coagulation process. Deficiency of protein C can lead to excessive coagulation that results in lack of tissue oxygenation, causing conditions such as deep vein thrombosis, pulmonary embolism, and stroke. Human protein C has been approved as a treatment for congenital protein C deficiency; however, the therapy requires frequent injections, due to the short residence time of the protein. Subcutaneous administration has been examined as an alternative to increase residence time and decrease injection frequency, thereby creating a more patient-friendly dosing regimen. In order to design an efficient injection or infusion protocol for subcutaneously administered proteins, it is important to accurately model the behavior (absorption, distribution, elimination) of these proteins in the body. However, several factors involved in a subcutaneous injection of the protein make modeling this behavior a challenging task. For example, absorption of the drug from the subcutaneous site into the blood stream can be variable depending on the site of injection, physical activity of the patient, etc. Furthermore, degradation of the protein can occur at the site of injection and further modify its absorption. The objective of this work was to demonstrate the utility of frequency response modeling as an alternative method to analyze the behavior of subcutaneously administered protein C. The results of our study indicate that if the dose range yielding the constant clearance of protein C is identified for the patient, models of that type, as presented in our study, can be used to adjust optimal dosing of protein C necessary to reach prescribed levels of the protein in this patient at desired time points, both specified by treatment requirements.

Activated protein C: potential therapy for severe sepsis, thrombosis, and stroke.

Activated protein C (APC) reduced all-cause 28-day mortality by 19% in patients with severe sepsis (sepsis associated with acute organ dysfunction) in the Protein C Evaluation in Severe Sepsis (PROWESS) trial, leading to recent approval of recombinant APC for treatment of this condition in adults. This review summarizes current knowledge derived from studies of a variety of animal models in which infused human APC demonstrated beneficial activities. Based on in vivo and also in vitro data, APC manifests antithrombotic, profibrinolytic, anti-inflammatory, and antiapoptotic activities. APC is a normal circulating component of plasma, derived from the protein C zymogen, and is thus a natural endogenous protective homeostatic factor. Because of its multiple activities, APC has a potential role in the treatment of complex and challenging medical disorders, including thrombosis and stroke.

Pharmacokinetic-pharmacodynamic analysis of drotrecogin alfa (activated) in patients with severe sepsis.

OBJECTIVE: We aimed to characterize the pharmacokinetics and pharmacodynamics of drotrecogin alfa (activated) (recombinant human activated protein C) in patients with severe sepsis. METHODS: Patients (N = 1690) in a randomized, double-blind, placebo-controlled phase 3 trial received a 96-hour infusion of placebo (n = 840) or drotrecogin alfa (activated) (n = 850), 24 microg x kg(-1) x h(-1). Plasma samples from 680 patients were collected for pharmacokinetic assessment. Pharmacodynamic effects on activated partial thromboplastin time, D-dimer, protein C, and interleukin 6 were analyzed by drotrecogin alfa (activated) steady-state plasma concentration (C(ss)) quartile. RESULTS: Transient endogenous activated protein C concentrations above 10 ng/mL were observed in 11 placebo-treated patients (3.3%). In drotrecogin alfa (activated)-treated patients, the median C(ss) was 44.9 ng/mL and the median plasma clearance (CL(p)) was 40.1 L/h. C(ss) was reached within 2 hours after the infusion was started. Plasma concentrations were below the assay quantitation limit of 10 ng/mL within 2 hours after the infusion was stopped in 92% of patients. CL(p) increased with increasing body weight, so infusion rates should be based on predose body weight. Mean CL(p) associated with age, sex, or baseline hepatic or renal function differed by less than 30% from the mean CL(p) in all patients and resided within the interquartile range of CL(p) in all patients. Dose adjustment is not required on the basis of these factors alone or in combination. No correlation was detected between C(ss) quartile and bleeding risk or the magnitudes of effect on biomarkers of coagulopathy (D-dimers and protein C) and inflammation (interleukin 6). CONCLUSIONS: Plasma concentrations of drotrecogin alfa (activated) attain steady state rapidly after the infusion is started and decline rapidly after the infusion is stopped. The infusion rate should be based on predose body weight and not on any other demographic or baseline clinical covariate.

Inhibition of platelet thrombosis using an activated protein C-loaded stent: in vitro and in vivo results.

In high-risk and complicated coronary intervention, the risk of acute closure is unpredictable. Thrombus and platelet deposition at the intervention site may also have further effects on subsequent restenosis. In vivo infusion of activated protein C has previously been shown to achieve potent anticoagulation without any haemostatic side effects. We now evaluated the in vitro and in vivo efficacy of polymer-coated coronary stents loaded with purified rabbit Activated Protein C (APC). By measuring 125I-fibrinogen/fibrin deposition APC-loaded stent-wires were antithrombotic compared to albumin-loaded, inhibited-APC-loaded, plain polymer-coated and stainless steel stent-wires. In a balloon injury rabbit iliac artery model, APC-loaded stents did not occlude (0/14) compared to plain stents (9/15) and BSA-loaded stents (2/4). Relative 111In-labelled platelet deposition showed a similarly significant degree of inhibition. In conclusion, APC-loading could render stents significantly less thrombotic. Whether an effective antithrombogenic stent like this effectively reduces restenosis rates warrants further evaluation.

Effect of protein C and activated protein C on coagulation and fibrinolysis in normal human subjects.

Although protein C (PC) and activated protein C (APC) have been postulated to be useful for treating patients with thrombosis, their critical effect remains to be studied in human subjects. To examine whether purified PC or APC are useful for treating patients with thrombosis without showing any adverse effect, we studied effects on coagulation and fibrinolysis in normal human subjects. When highly purified human PC was administered intravenously to healthy subjects, plasma levels of immunoreactive PC decreased with a half-life of 10.9 h. Intravenously administered APC decreased with a half-life of 23 min as measured by prolongation of activated partial thromboplastin time (APTT). However, 1.7 h was obtained for the plasma half-life of APC when it was measured immunologically. These findings suggested that a significant fraction of the administered APC was rapidly inhibited by plasma inhibitor. Upon administration of APC, APTT was prolonged and plasma levels of clotting factor VIII (F-VIII) decreased transiently as measured by clotting assay. However, when determined by a chromogenic assay method in which 120-fold diluted plasma samples were used, plasma levels of F-VIII remained unchanged. Plasma levels of F-V did not decrease after APC administration. These findings suggested that prolongation of APTT and apparent decrease in plasma F-VIII clotting activity might be due to the in vitro-effect of APC present in plasma samples used. Diurnal fluctuation of plasminogen activator inhibitor in normal subject was not affected by administration of APC. Thus, PC or APC seems to function selectively at the site of thrombin-formation without lowering plasma levels of coagulation factors.

Homozygous protein C deficiency: description of a new mutation and successful treatment with low molecular weight heparin.

We present a kindred with a new mutation of the protein C gene, in which the proband had an unusual clinical presentation. The relationship between warfarin induced skin necrosis and level of anticoagulation was investigated. The pharmacokinetics of protein C concentrate was assessed to determine frequency of replacement therapy. The clinical and biochemical efficacy of therapy with low molecular weight heparin (LMWH) was assessed. The effect of long-term LMWH on bone density in the growing child was monitored using whole body densitometry. Warfarin therapy required an INR of greater than 3.5 to avoid skin necrosis. If protein C replacement was to be used, doses of 100 U/kg/day would have been required to maintain protein C levels consistently at or above 0.20 U/ml. While receiving prophylactic therapy with LMWH for almost 3 years, there were no episodes of recurrent thrombosis, no skin necrosis and no bleeding. Biochemical markers of in vivo thrombin generation were suppressed and within the normal range. Bone density continued to increase at the normal rate throughout the treatment period. LMWH is an effective form of long-term therapy for homozygous protein C deficient patients with measurable protein C levels.

Drotrecogin alfa (activated).

Drotrecogin alfa (activated), recombinant human activated protein C, inhibits coagulation and inflammation and promotes fibrinolysis in patients with severe sepsis. 850 patients with severe sepsis treated with intravenous drotrecogin alfa (activated) 24 microg/kg/h for 96 hours had a significantly greater reduction in 28-day all-cause mortality (24.7%) than 840 placebo recipients (30.8%) in a randomised, double-blind, placebo-controlled study. The drug was associated with a 19.4% reduction in the relative risk of death at 28 days compared with placebo. Baseline characteristics of and pre-existing conditions in patients with sepsis appeared to have no effect on the efficacy of drotrecogin alfa (activated). A significantly greater reduction in median percentage change from baseline plasma D-dimer levels (a coagulation marker) was seen with drotrecogin alfa (activated) treatment than with placebo on study days 1 to 7 in patients with severe sepsis. On study days 1, 4, 5, 6 and 7, a significantly greater median reduction in interleukin-6 levels (an inflammation marker) from baseline was seen with drotrecogin alfa (activated) treatment than placebo. Drotrecogin alfa (activated) was associated with an increased incidence of serious bleeding events during the infusion period [2.4% vs 1.0% with placebo; p = 0.024] and the 28-day study period (3.5 vs 2.0%; p = 0.06) of the efficacy trial. This increase was primarily related to procedure-related events; there were no significant differences between the treatment groups in nonprocedure-related serious bleeding events. The most frequent site of bleeding was the gastrointestinal tract. With the exception of bleeding events, there were no clinically significant differences between treatment groups in the efficacy trial in the incidence of adverse events. Of the 210 deaths in patients with severe sepsis treated with drotrecogin alfa (activated) 24 microg/kg/h in the efficacy trial, four deaths due to haemorrhage and one due to cerebral oedema were possibly related to the study drug.

Combined antithrombin and protein C supplementation in meningococcal purpura fulminans: a pharmacokinetic study.

PURPOSE: To document in patients with meningococcal purpura fulminans (PF), the effects of a combined supplementation with antithrombin (AT) and protein C (PC) plasma concentrates and to estimate the pharmacokinetics and dose requirements of each inhibitor. DESIGN: Retrospective study of 15 patients. SETTING. One paediatric and one adult ICU in a university hospital. INTERVENTIONS: In addition to standard intensive care, all patients received a 100 IU/kg loading dose of AT and PC concentrates, followed by a continuous infusion (AT: 100-150 IU.kg.day; PC: 100 IU.kg.day in adults, and 400 IU/kg in infants). MEASUREMENTS: Clinical data, coagulation, and fibrinolysis parameters, AT and PC activities, and free protein S (PS) levels were sequentially measured. Restitution ratio, median increment after supplementation, and half-life of clearance from plasma were calculated for the two plasma substitutes. RESULTS. At admission, all patients had a severe decrease in AT, PC, and PS levels. The supplementation regimen induced a substantial increase in AT and PC activities, peaking at H18 and H48, respectively. The supplementation procedure did not modify free PS levels. The median values of AT and PC restitution ratio, increment in plasma activity observed after 100 IU/kg concentrate, and apparent half-life of clearance from plasma were 0.85 U.ml.U.kg and 0.59 U.ml.U.kg, 23% and 21%, 16 h and 6 h, respectively. CONCLUSION: If AT and PC concentrates are to be given in fulminant meningococcemia, the doses of supplementation should be at least 150 IU/kg AT and 250 IU/kg PC as loading dose and 150 IU/kg AT and 200 IU/kg PC as daily maintenance therapy. Taking into account the individual variability in inhibitor deficiency and restitution ratio, repeated measurements of plasma levels are mandatory to obtain a patient-based adjustment of the supplementation.

Removal of a dimeric form of surfactant protein C from mouse lungs: its acceleration by reduction.

Clearance of hydrophobic surfactant-associated protein C (SP-C) and its dimeric form ([SP-C]2) was investigated. SP-C and [SP-C]2 obtained from proteinosis patients were fluorescently labeled and were instilled into mouse lungs as lipid-protein complexes. [SP-C]2 was removed more slowly than SP-C, with apparent half-lives of 30 and 18 h, respectively. A significant amount of [SP-C]2 was removed as SP-C, and the conversion rate was 0.22 micrograms.h-1.mouse-1. By correcting the removal as SP-C, we obtained 38 h for a possible half-life of [SP-C]2. Conversion from SP-C to [SP-C]2 seemed very slow. Decrease in glutathione (GSH) in the lung inhibited the conversion of [SP-C]2 to SP-C and GSH-treatment of liposomes accelerated clearance of [SP-C]2. These results suggest that the removal of [SP-C]2 from lung is accelerated by reduction and that GSH acts as a reducing agent in the lung.

Pharmacokinetics and clinical use of drotrecogin alfa (activated) in patients with severe sepsis.

Drotrecogin alfa (activated) pharmacokinetics have been reported in healthy volunteers and in patients with severe sepsis. Clearance is rapid and appears to increase with weight; consequently, drotrecogin alfa (activated) is dosed on a weight basis. Drotrecogin alfa (activated) promotes fibrinolysis and inhibits thrombin production to produce an anticoagulant effect. The primary adverse events are related to its pharmacologic activity, with serious bleeding reported in 3.5% of patients receiving the drug in a multicenter phase III trial compared with 2.0% for patients receiving placebo. Monitoring parameters correspond with bleeding and should include international normalized ratio, platelet count, hematocrit, and overt signs of bleeding. Because of the protein nature of drotrecogin alfa (activated), pharmacists should be aware of the proper preparation and stability issues in order to afford efficient, cost-effective administration. As further data on drotrecogin alfa (activated) therapy become available, dosing and monitoring strategies may be altered to optimize the clinical benefits.

Pharmacology, clinical efficacy, and safety of drotrecogin alfa (activated).

The protein C pathway, which plays an important role in maintaining normal hemostasis and is a critical link between the inflammatory and procoagulant host responses to infection, is involved in modulating the coagulation and inflammation associated with severe sepsis. Recombinant human activated protein C (APC), or drotrecogin alfa (activated), shares the intrinsic pharmacologic activity of endogenous APC. In the Recombinant Human Activated Protein C Worldwide Evaluation in Severe Sepsis (PROWESS) trial, drotrecogin alfa (activated) decreased absolute mortality by 6% and relative risk of mortality by 19% compared with placebo. Drotrecogin alfa (activated) is an important advancement in the treatment of adult patients with severe sepsis.

Physical and chemical compatibility of drotrecogin alfa (activated) with 34 drugs during simulated Y-site administration.

PURPOSE: The physical and chemical compatibility of drotrecogin alfa (activated) (recombinant human activated protein C) during simulated Y-site administration with drugs commonly used to treat patients with severe sepsis was determined. METHODS: Thirty-four drugs were investigated for visual compatibility with drotrecogin alfa, and included cardiovascular agents, conscious sedative agents, antibiotics, blood products, and other supportive care drugs. The physical and chemical compatibility of drotrecogin alfa with these drugs was determined using a well-established experimental model to simulate Y-site administration. Drotrecogin alfa (activated) was prepared as 100- and 1000-microg/mL solutions in 0.9% sodium chloride injection. All other drugs were prepared at maximum concentrations commonly administered in the clinical setting. Visual compatibility was assessed by visual inspection (observations of haziness, color change, or precipitate formation) and pH measurement at 0, 30, 60, and 240 minutes after mixing. RESULTS: Of the 34 test drugs, 8 were defined as visually compatible with drotrecogin alfa; these drugs were further assessed for chemical compatibility with drotrecogin alfa. The protein content, potency, and purity of drotrecogin alfa were determined at 0, 60, and 240 minutes after Y-site mixing as indicators of chemical compatibility. Six drugs (ceftriaxone, cisatracurium, fluconazole, nitroglycerin, potassium chloride, and vasopressin) were determined to be chemically compatible with drotrecogin alfa; two drugs (cyclosporine and ticarcillin-clavulanate) were chemically incompatible with drotrecogin alfa after Y-site mixing. CONCLUSION: Ceftriaxone, cisatracurium, fluconazole, nitroglycerin, potassium chloride, and vasopressin were physically and chemically compatible with drotrecogin alfa in a simulated Y-site infusion; 28 other drugs were incompatible with drotrecogin alfa.

Recombinant human activated protein C in severe sepsis.

The role of activated protein C (APC) in coagulation, inflammation, and fibrinolysis and the pharmacology, pharmacokinetics, and trials of recombinant human activated protein C (rhAPC), or drotrecogin alfa (activated), in sepsis are described. Protein C, a naturally occurring vitamin K-dependent serine protease in the blood, remains inactive until exposed to the thrombin-thrombomodulin complex. This change between the inactive and active forms occurs constantly in humans and serves to balance the coagulation cascade. APC functions in concert with protein S as an anticoagulant, a fibrinolytic agent, and an antiinflammatory agent. In response to serious infection, a procoagulant process is activated leading to thrombin and fibrin deposition in small vessels that results in decreased blood flow, decreased oxygen delivery, and organ failure. The body's natural defense during severe sepsis is to activate protein C through the thrombin-thrombomodulin complex in an attempt to restore the imbalance of the hemostatic systems. However, APC has a short half-life, and the pool of circulating protein C is rapidly depleted in severe sepsis. Low protein C levels have been correlated with poor outcome in patients with severe sepsis and in animal models. These observations led to a Phase III safety and efficacy trial of drotrecogin alfa (activated) that demonstrated a significant improvement in mortality compared with placebo (24.7% versus 30.8%). This 6.1% absolute difference in mortality translates to a 19.4% reduction in relative risk of death in the treated patients. The proper use of drotrecogin alfa (activated) will require careful consideration of appropriate patients to treat and further studies in patient populations that were excluded from the Phase III trial, as well as possible modification of dosing schemes on the basis of patient response.

Phase 1 safety, tolerability and pharmacokinetics of 3K3A-APC in healthy adult volunteers.

BACKGROUND AND PURPOSE: Activated Protein C (APC) stimulates multiple cytoprotective pathways via the protease activated receptor-1 (PAR-1) and promotes anticoagulation. 3K3A-APC was designed for preserved activity at PAR-1 with reduced anticoagulation. This Phase 1 trial characterized pharmacokinetics and anticoagulation effects of 3K3A-APC. METHODS: Subjects (n=64) were randomly assigned to receive 3K3A-APC (n=4) at 6, 30, 90, 180, 360, 540 or 720 µg/kg or placebo (n=6) and were observed for 24 hr. After safety review additional subjects received drug every 12 hr for 5 doses (n=6 per group) at 90, 180, 360, or 540 µg/kg or placebo (n=8) and were observed for 24 hr. RESULTS: All subjects returned for safety assessments at 72 hours and 15 days. We found few adverse events in all groups. Systolic blood pressure increased in both active and placebo groups. Moderately severe headache, nausea and vomiting were reported in one of two subjects treated with 720 µg/kg so 540 µg/kg was considered the highest tolerated dose. Mean plasma concentrations increased in proportion to dose. Clearance ranged from 11,693 ± 807 to 18,701 ± 4,797 mL/hr, volume of distribution ranged from 4,873±828 to 6,971 ± 1,169 mL, and elimination half-life ranged from 0.211 ± 0.097 to 0.294 ± 0.054 hours. Elevations in aPTT were minimal. CONCLUSIONS: 3K3A-APC was well tolerated at multiple doses as high as 540 µg/kg. These results should be confirmed in stroke patients with relevant co-morbidities. Clinical Trial Registration-URL: http://www.clinicaltrials.gov. Unique identifier: NCT01660230.

High dose infusion of activated protein C (rhAPC) fails to improve neuronal damage and cognitive deficit after global cerebral ischemia in rats.

PURPOSE: Recent studies demonstrated anticoagulatory, antiinflammatory, antiapoptotic, and neuroprotective properties of activated protein C (APC) in rodent models of acute neurodegenerative diseases, suggesting APC as promising broad acting therapeutic agent. Unfortunately, continuous infusion of recombinant human APC (rhAPC) failed to improve brain damage following cardiac arrest in rats. The present study was designed to investigate the neuroprotective effect after global cerebral ischemia (GI) with an optimized infusion protocol. METHODS: Rats were subjected to bilateral clip occlusion of the common carotid arteries (BCAO) and controlled hemorrhagic hypotension to 40 mm Hg for 14 min and a subsequent 5h-infusion of rhAPC (2mg/kg bolus+6 mg/kg/h continuous IV) or vehicle (0.9% NaCl). The dosage was calculated to maintain plasma hAPC activity at 150%. Cerebral inflammation, apoptosis and neuronal survival was determined at day 10. RESULTS: rhAPC infusion did not influence cortical cerebral perfusion during reperfusion and failed to reduce neuronal cell loss, microglia activation, and caspase 3 activity. CONCLUSION: Even an optimized rhAPC infusion protocol designed to maintain a high level of APC plasma activity failed to improve the sequels following GI. Despite positive reports about protective effects of APC following, e.g., ischemic stroke, the present study supports the notion that infusion of APC during the early reperfusion phase does not result in sustained neuroprotection and fails to improve outcome after global cerebral ischemia.