An update on recent patents on thrombin inhibitors (2010 – 2013)

Self-assembled, bivalent aptamers on graphene oxide as an efficient anticoagulant

Graphene oxide (GO) has unique structural properties, can effectively adsorb single-strand DNA through π-π stacking, hydrogen bonding and hydrophobic interactions, and is useful in many biotechnology applications. In this study, we developed a thrombin-binding-aptamers (15- and 29-mer) conjugated graphene oxide (TBA15/TBA29-GO) composite for the efficient inhibition of thrombin activity towards the formation of fibrin from fibrinogen. The TBA15/TBA29-GO composite was simply obtained by the self-assembly of TBA15/TBA29 hybrids on GO. The high density and appropriate orientation of TBA15/TBA29 on the GO surface enabled TBA15/TBA29-GO to acquire an ultrastrong binding affinity for thrombin (dissociation constant = 2.9 × 10-12 M). Compared to bivalent TBA15h20A20/TBA29h20A20 hybrids, the TBA15/TBA29-GO composite exhibited a superior anticoagulant potency (ca. 10-fold) against thrombin-mediated coagulation as a result of steric blocking effects and a higher binding affinity for thrombin. In addition, the prolonged thrombin clotting time, prothrombin time (PT), and activated partial thromboplastin time (aPTT) of TBA15/TBA29-GO were at least 2 times longer than those of commercially available drugs (heparin, argatroban, hirudin, and warfarin). The in vitro cytotoxicity and hemolysis analyses revealed the high biocompatibility of TBA15/TBA29-GO. The rat-tail bleeding assay of the hemostasis time and ex vivo PT and aPTT further revealed that TBA15/TBA29-GO is superior (>2-fold) to heparin, which is commonly used in the treatment and prevention of thrombotic diseases. Our multivalent, oligonucleotide-modified GO nanocomposites are easy to prepare, cost-effective, and highly biocompatible and they show great potential as effective anticoagulants for the treatment of thrombotic disorders.

Enzymatic and chemical synthesis of new anticoagulant peptides

In this study we report the enzymatic synthesis of N-α-[Carbobenzyloxy]-Tyr-Gln-Gln (Z-YQQ), a new anticoagulant tripeptide. It was obtained using phytoproteases from the stems and petioles of Asclepias curassavica L. as catalyst in an aqueous-organic biphasic system formed by 50% (v/v) ethyl acetate and 0.1 M Tris-HCl buffer pH 8. The resulting peptide was compared with the analogous peptide Tyr-Gln-Gln (YQQ) produced by solid-phase chemical synthesis. The in vitro anticoagulant activity of the aforementioned peptides was determined using Wiener Lab Test (Wiener, Argentina). The toxicological activity of the peptides was also determined. The enzymatically synthesized Z-YQQ peptide acted on the extrinsic pathway of the coagulation cascade, delaying the conversion time of prothrombin to thrombin and fibrinogen to fibrin by 136 and 50%, respectively, with respect to the controls. The chemically synthesized YQQ peptide acted specifically on the intrinsic pathway of the coagulation cascade, affecting factors VIII, IX, XI, and XII from such cascade, and increasing the coagulation time by 105% with respect to the control. The results suggest that two new anticoagulant peptides (Z-YQQ and YQQ) can be useful for safe pharmaceutical applications. Nevertheless, some aspects related to peptide production should be optimized. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 2018 © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1093-1101, 2018.

Rapid magnetic solid-phase extraction combined with ultra-high performance liquid chromatography and quadrupole-time-of-flight mass spectrometry for analysis of thrombin binders from a crude extract and injection of Erigeron breviscapus

Thrombin, which acts as a serine protease that converts soluble fibrinogen into insoluble strands of fibrin, plays crucial roles in the blood coagulation pathway.

Development of Orally Active Thrombin Inhibitors for the Treatment of Thrombotic Disorder Diseases

Thrombotic disorders represent the major share of the various cardiovascular diseases, and significant progress has been made in the development of synthetic thrombin inhibitors as new anticoagulants. In addition to the development of highly potent and selective inhibitors with improved safety and suitable half-life, several allosteric inhibitors have been designed and synthesized, that did not fully nullify the procoagulant signal and thus could result in reduced bleeding complications. Furthermore, natural products with thrombin inhibitory activity have been isolated, and some natural products have been modified in order to improve their inhibitory activity and metabolic stability. This review summarizes the development of orally active thrombin inhibitors for the treatment of thrombotic disorder diseases, which could serve as a reference for the interested researchers.

Prolinamide derivatives as thrombin inhibitors for the treatment of thrombin-mediated diseases: a patent evaluation of US2013296245

INTRODUCTION

Thrombotic disorders can lead to deep vein thrombosis, myocardial infarction and stroke. Thrombin plays a vital role in cascade reaction of blood coagulation, inhibition of the activity of thrombin can block the formation of thrombus and direct thrombin inhibitor has a prospect to overcome the limitations in application of the traditional anticoagulant drugs.

AREAS COVERED

The current patent US2013296245 describes a series of prolinamide derivatives with formula (I) as thrombin inhibitors. These new compounds are defined to be pharmaceutically acceptable salts derived from pharmaceutically acceptable inorganic acid and organic acid, and pharmaceutically acceptable prodrug where N-alkoxycarbonyl is protected or carboxylic acid is protected by ester.

EXPERT OPINION

The patent used formamidine and its N-alkoxycarbonyl-protected derivatives as the P1 group; these groups were less basic compared with the traditional guanidine group, so their lipophilicity could be optimized to achieve oral absorption. Furthermore, these pharmaceutically acceptable prodrugs where N-alkoxycarbonyl is protected or carboxylic acid is protected by ester could achieve prolonged half-life for a convenient once- or twice-daily oral dosing. These efforts gave a new hope and confidence to treat thrombotic disorders with selective and orally active thrombin inhibitors.

A new peptide (Ruviprase) purified from the venom of Daboia russelii russelii shows potent anticoagulant activity via non-enzymatic inhibition of thrombin and factor Xa

Compounds showing dual inhibition of thrombin and factor Xa (FXa) are the subject of great interest owing to their broader specificity for effective anticoagulation therapy against cardiovascular disorders. This is the first report on the functional characterization and assessment of therapeutic potential of a 4423.6 Da inhibitory peptide (Ruviprase) purified from Daboia russelii russelii venom. The secondary structure of Ruviprase is composed of α-helices (61.9%) and random coils (38.1%). The partial N-terminal sequence (E(1)-V(2)-X(3)-W(4)-W(5)-W(6)-A(7)-Q(8)-L(9)-S(10)) of Ruviprase demonstrated significant similarity (80.0%) with an internal sequence of apoptosis-stimulating protein reported from the venom of Ophiophagus hannah and Python bivittatus; albeit Ruviprase did not show sequence similarity with existing thrombin/FXa inhibitors, suggesting its uniqueness. Ruviprase demonstrated a potent in vitro anticoagulant property and inhibited both thrombin and FXa following slow binding kinetics. Ruviprase inhibited thrombin by binding to its active site via an uncompetitive mechanism with a Ki value and dissociation constant (KD) of 0.42 μM and 0.46 μM, respectively. Conversely, Ruviprase demonstrated mixed inhibition (Ki = 0.16 μM) of FXa towards its physiological substrate prothrombin. Furthermore, the biological properties of Ruviprase could not be neutralized by commercial polyvalent or monovalent antivenom. Ruviprase at a dose of 2.0 mg/kg was non-toxic and showed potent in vivo anticoagulant activity after 6 h of intraperitoneal treatment in mice. Because of the potent anticoagulant property as well as non-toxic nature of Ruviprase, the possible application of the peptide as an antithrombotic agent for combating thrombosis-associated ailments appears promising.

Graphene oxide modified with aptamer-conjugated gold nanoparticles and heparin: a potent targeted anticoagulant

Synthesis of a nanocomposite of aptamer-conjugated gold nanoparticles and heparin co-immobilized graphene oxide that acts as a highly effective anticoagulant by controlling the thrombin activity towards fibrinogen.