290
W. Li et al.
10.2.3.1 RA-36
In a study, turbidimetric assay and coagulation tests including thrombin time (TT) and
PT tests were conducted to evaluate the inhibitory activity of aptamers constructed
by exchanging the modules between 31TBA and NU172. The results showed RA36 DNA aptamer (dGGTTGGTGTGGTTGGTGGTTGGTGTGGTTGG·2 KCl) has
two joint pharmacophore entities which also interplay with the functional nonequivalence, suggesting a possible asymmetric structure of RA-36. Among them,
5
-truncated RA-36 has half of the activity of RA-36, and the same activity of 15TBA. 3
-truncated RA-36 has intermediate activity between 15-TBA and RA-36.
These results suggested that the inhibitory activity of G-quadruplex is regulated by
additional modules, as well as joined pharmacophore modules [51].
RA-36 has a bimodular structure with several special properties, in which the
first G-quadruplex recognizes and inhibits thrombin and the second G-quadruplex
regulates the properties of the first. The bimodular structure makes the bleeding risk
to be potentially decreased in a favorable dose–effect dependent manner. The anticoagulant, antithrombotic activity, and pharmacokinetics of RA-36 were compared
to bivalirudin in animal models. Bivalirudin showed tenfold higher anticoagulant
and antithrombotic activity, whereas RA-36 was found to be twenty-fold faster in
elimination from blood with a half-life of 1 min. Currently, the pharmacokinetics,
conjugation, and modification are under investigation to improve dosage profile and
to reduce the renal clearance rate of RA-36. The study suggested that RA-36 may be
an alternative to bivalent peptide bivalirudin and is a promising candidate for a new
generation of anticoagulants [52].
RA-36 was intravenously injected in high doses at 1.4–7.1 mmol/kg (14–
70 mg/kg) to explore its antithrombotic effect in a murine model of thrombosis. The
comparative study revealed that both RA-36 aptamer and bivalirudin had similar
antithrombotic effects in the murine thrombosis model, while the anticoagulation
activity of bivalirudin was several times higher than RA-36 in vitro. The results
suggested that both RA-36 aptamer and bivalirudin are direct thrombin inhibitors
with different potency, but possible interactions between the two thrombin-inhibitor
and blood coagulation complex may affect their physiological antithrombotic effects
[53].
10.2.3.2 RE31
RE31 is a 31-mer ssDNA aptamer containing the sequence of the core residues of 15mer TBA and with the mixed duplex/quadruplex oligonucleotide that can effectively
prolong thrombin time.
RE31 inhibited both thrombin formation in human plasma catalyzed by exogenous
and endogenous thrombin and thrombin-induced human platelet aggregation but did
not modify the state of enzyme active center. The experiment of clotting inhibiting
W. Li et al.
10.2.3.1 RA-36
In a study, turbidimetric assay and coagulation tests including thrombin time (TT) and
PT tests were conducted to evaluate the inhibitory activity of aptamers constructed
by exchanging the modules between 31TBA and NU172. The results showed RA36 DNA aptamer (dGGTTGGTGTGGTTGGTGGTTGGTGTGGTTGG·2 KCl) has
two joint pharmacophore entities which also interplay with the functional nonequivalence, suggesting a possible asymmetric structure of RA-36. Among them,
5
-truncated RA-36 has half of the activity of RA-36, and the same activity of 15TBA. 3
-truncated RA-36 has intermediate activity between 15-TBA and RA-36.
These results suggested that the inhibitory activity of G-quadruplex is regulated by
additional modules, as well as joined pharmacophore modules [51].
RA-36 has a bimodular structure with several special properties, in which the
first G-quadruplex recognizes and inhibits thrombin and the second G-quadruplex
regulates the properties of the first. The bimodular structure makes the bleeding risk
to be potentially decreased in a favorable dose–effect dependent manner. The anticoagulant, antithrombotic activity, and pharmacokinetics of RA-36 were compared
to bivalirudin in animal models. Bivalirudin showed tenfold higher anticoagulant
and antithrombotic activity, whereas RA-36 was found to be twenty-fold faster in
elimination from blood with a half-life of 1 min. Currently, the pharmacokinetics,
conjugation, and modification are under investigation to improve dosage profile and
to reduce the renal clearance rate of RA-36. The study suggested that RA-36 may be
an alternative to bivalent peptide bivalirudin and is a promising candidate for a new
generation of anticoagulants [52].
RA-36 was intravenously injected in high doses at 1.4–7.1 mmol/kg (14–
70 mg/kg) to explore its antithrombotic effect in a murine model of thrombosis. The
comparative study revealed that both RA-36 aptamer and bivalirudin had similar
antithrombotic effects in the murine thrombosis model, while the anticoagulation
activity of bivalirudin was several times higher than RA-36 in vitro. The results
suggested that both RA-36 aptamer and bivalirudin are direct thrombin inhibitors
with different potency, but possible interactions between the two thrombin-inhibitor
and blood coagulation complex may affect their physiological antithrombotic effects
[53].
10.2.3.2 RE31
RE31 is a 31-mer ssDNA aptamer containing the sequence of the core residues of 15mer TBA and with the mixed duplex/quadruplex oligonucleotide that can effectively
prolong thrombin time.
RE31 inhibited both thrombin formation in human plasma catalyzed by exogenous
and endogenous thrombin and thrombin-induced human platelet aggregation but did
not modify the state of enzyme active center. The experiment of clotting inhibiting