Treatment of acute ischemic stroke (AIS) with the thrombolytic/antithrombotic agent tissue plasminogen activator (tPA, Activase(R)) is limited due to the potential for severe hemorrhagic side effects. The first symptoms of acute ischemia to tPA treatment (time to needle) can span hours, even in developed urban areas, since an established diagnosis in a hospital setting is required before thrombolytic therapy. Consequently, there is a major unmet medical need for safe antithrombotic agents with no risk of bleeding that can be administered immediately as an emergency measure upon signs of acute cardio- and cerebrovascular events. To directly address this need, our company has been developing a novel antithrombotic agent for the safe treatment of AIS. The product candidate is a bioengineered recombinant selective protein C activator enzyme (PCA) that has potent antithrombotic effects without increasing hemorrhagic risks. Our proprietary PCA molecule, ProCase (E-WE thrombin) has been designed to act in part by increasing the surface concentration of the anticoagulant, profibrinolytic, and cytoprotective enzyme, endogenous activated protein C (APC), at the site of developing blood clots via targeted cellular delivery. This unique mechanism of action allows E-WE thrombin to target pathological blood clots without disabling vital hemostasis. In primates, doses as low as 1 ?g/kg are antithrombotic without systemic anticoagulation or any antihemostatic effects. The first toxicity and stability batch of E-WE thrombin has now been released, and a pre-investigational new drug (pre-IND) meeting with the FDA is being scheduled for late 2013. All of the critical milestones for our Fast-Track SBIR Phase I/II grant have been reached by: 1) Demonstrating that early treatment of experimental AIS with our prototype PCA, WE thrombin, improves neurological outcomes without hemostatic impairment in mice, 2) Establishing a pharmaceutically acceptable dosage form of E-WE thrombin, 3) Developing a serum-free production process, and 4) Determining that E-WE thrombin lacks demonstrable toxicity at >100-fold the expected human dosage in a preclinical acute dose escalation study at Charles River Labs. We have also established the appropriate scale-up methodology to produce E-WE thrombin in bulk amounts sufficient to perform all preclinical and human studies. Our Phase IIB aims that will support critical product development milestones are to: 1) Complete preclinical GLP toxicology studies of ProCase, 2) Manufacture a cGMP lot of ProCase for GLP stability and human clinical studies, 3) Prepare and file an IND application to test ProCase in acute ischemic stroke, and 4) Evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of ProCase in healthy volunteers in a phase 1 clinical trial. This SBIR Phase IIB Bridge Award, matched by already secured funds, will ultimately support the completion of a phase 1 first-in-human safety study investigating this unique and potentially life-saving antithrombotic drug candidate.

Public Health Relevance

Ischemic stroke remains a leading cause of death and chronic disability in part because early treatment with the clot-busting drug tissue plasminogen activator (tPA, Activase(R)) is limited by its associated risk of serious bleeding. To address this problem, we are developing a novel protein C activator enzyme, ProCase' (E-WE thrombin), which is a first-of-its-kind blood clot-specific antithrombotic drug candidate that coul be used early in the treatment of stroke since it does not increase bleeding. 1

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Small Business Innovation Research Grants (SBIR) - Phase II (R44)
Project #
Application #
Study Section
Special Emphasis Panel (ZHL1)
Program Officer
Warren, Ronald Q
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Aronora, Inc.
United States
Zip Code
Vogt, Austin D; Di Cera, Enrico (2013) Conformational selection is a dominant mechanism of ligand binding. Biochemistry 52:5723-9
Pozzi, Nicola; Vogt, Austin D; Gohara, David W et al. (2012) Conformational selection in trypsin-like proteases. Curr Opin Struct Biol 22:421-31
Vicente, Cristina P; Weiler, Hartmut; Di Cera, Enrico et al. (2012) Thrombomodulin is required for the antithrombotic activity of thrombin mutant W215A/E217A in a mouse model of arterial thrombosis. Thromb Res 130:646-8
Vogt, Austin D; Di Cera, Enrico (2012) Conformational selection or induced fit? A critical appraisal of the kinetic mechanism. Biochemistry 51:5894-902
Leung, Philberta Y; Hurst, Sawan; Berny-Lang, Michelle A et al. (2012) Inhibition of Factor XII-Mediated Activation of Factor XI Provides Protection Against Experimental Acute Ischemic Stroke in Mice. Transl Stroke Res 3:381-9
Niu, Weiling; Chen, Zhiwei; Gandhi, Prafull S et al. (2011) Crystallographic and kinetic evidence of allostery in a trypsin-like protease. Biochemistry 50:6301-7
Gohara, David W; Di Cera, Enrico (2011) Allostery in trypsin-like proteases suggests new therapeutic strategies. Trends Biotechnol 29:577-85
Pozzi, Nicola; Chen, Raymond; Chen, Zhiwei et al. (2011) Rigidification of the autolysis loop enhances Na(+) binding to thrombin. Biophys Chem 159:6-13
Di Cera, Enrico (2011) Thrombin as an anticoagulant. Prog Mol Biol Transl Sci 99:145-84
Rana, Sadhna; Pozzi, Nicola; Pelc, Leslie A et al. (2011) Redesigning allosteric activation in an enzyme. Proc Natl Acad Sci U S A 108:5221-5

Showing the most recent 10 out of 22 publications