298
W. Li et al.
Szlam et al. evaluated the in vitro effects of RB006, pegnivacogin, in combination
with warfarin. Results of simulation of coagulation undergoing warfarin induction
showed that RB006 significantly decreased thrombin generation propagation in the
setting of FVII and protein C deficiency. RB006 effectively inhibited both TF and
activation of intrinsic coagulation pathway in the setting of low F VII in warfarin
therapy.In addition, RB006 did not inhibit protein C and increase PT values but
increased APTT values in a dose-dependent manner, suggesting that warfarin therapy
can be monitored without interrupting the aptamer infusion. The data suggested
that RB006 may be an alternative therapeutic strategy when warfarin was used in
patients at thrombotic risks, especially under the condition of protein C deficiency
or in perioperative period. Further studies are necessary to evaluate the efficacy and
safety of RB006 as an adjuvant agent during the initiation of warfarin therapy [71].
Intravenous tissue-type plasminogen activator in acute ischemic stroke is underutilized partly for life-threatening hemorrhage. Ch-9.3t is a 35 nucleotides RNA aptamer
against human FIXa with modification of 2
-fluoropyrimidines and a 3
inverted
thymidine cap for nuclease resistance, as well as a 5
-end cholesterol moiety to
increase its half-life. The mutant aptamer Ch-9.3tM is Ch-9.3t with exception of
2
nucleotides blocking aptamer-FIXa binding. 5-2C is 2
-O-methyl RNA antidote
oligonucleotide that inhibits Ch-9.3t-FIXa binding and then neutralizes aptamer’s
anticoagulant activity. To meet the clinical need for safer stroke therapy, Blake and
his group developed aptamer-based therapeutics to facilitate cerebral reperfusion in
a C57Bl/6 J murine model of ischemic stroke induced by transient middle cerebral
artery occlusion (MCAO). The results demonstrated that intravenous injection of Ch9.3t aptamer drug after 60 min of cerebral ischemia and reperfusion could effectively
improve neurological function after stroke because of reduced thrombin generation
and inflammation. Moreover, antidote 5-2C reduced hemorrhage grade as well as
mortality after a subarachnoid hemorrhage (SAH) under the condition of intracranial hemorrhage. These aptamer-antidote pairs may be a novel and safer approach
for the treatment of stroke [83].
Sullenger and his colleagues elucidated the molecular mechanism of anti-FIXa
aptamer 9.3t. They found that the aptamer bound FIXa and blocked FX activation regardless of FVIIIa, thus increased the clotting time in human plasma. These
results showed that aptamer 9.3t blocked the interaction between FIXa and its macromolecular substrate while partly blocked interaction with small molecular substrate
cleavage active site probes. Thereby, unlike other small molecule drugs, aptamers
may bind surfaces surrounding an active site and therefore sterically interfere with
enzyme activity. Aptamers 9.3t may be applied to probe extended surfaces on target
proteins and to block substrate-binding exosites of enzymes. FIXa aptamer may be
a potent anticoagulant through inhibiting binding between FX and the FIXa-VIIIa
complex and FX activation in clinical settings [84].
W. Li et al.
Szlam et al. evaluated the in vitro effects of RB006, pegnivacogin, in combination
with warfarin. Results of simulation of coagulation undergoing warfarin induction
showed that RB006 significantly decreased thrombin generation propagation in the
setting of FVII and protein C deficiency. RB006 effectively inhibited both TF and
activation of intrinsic coagulation pathway in the setting of low F VII in warfarin
therapy.In addition, RB006 did not inhibit protein C and increase PT values but
increased APTT values in a dose-dependent manner, suggesting that warfarin therapy
can be monitored without interrupting the aptamer infusion. The data suggested
that RB006 may be an alternative therapeutic strategy when warfarin was used in
patients at thrombotic risks, especially under the condition of protein C deficiency
or in perioperative period. Further studies are necessary to evaluate the efficacy and
safety of RB006 as an adjuvant agent during the initiation of warfarin therapy [71].
Intravenous tissue-type plasminogen activator in acute ischemic stroke is underutilized partly for life-threatening hemorrhage. Ch-9.3t is a 35 nucleotides RNA aptamer
against human FIXa with modification of 2
-fluoropyrimidines and a 3
inverted
thymidine cap for nuclease resistance, as well as a 5
-end cholesterol moiety to
increase its half-life. The mutant aptamer Ch-9.3tM is Ch-9.3t with exception of
2
nucleotides blocking aptamer-FIXa binding. 5-2C is 2
-O-methyl RNA antidote
oligonucleotide that inhibits Ch-9.3t-FIXa binding and then neutralizes aptamer’s
anticoagulant activity. To meet the clinical need for safer stroke therapy, Blake and
his group developed aptamer-based therapeutics to facilitate cerebral reperfusion in
a C57Bl/6 J murine model of ischemic stroke induced by transient middle cerebral
artery occlusion (MCAO). The results demonstrated that intravenous injection of Ch9.3t aptamer drug after 60 min of cerebral ischemia and reperfusion could effectively
improve neurological function after stroke because of reduced thrombin generation
and inflammation. Moreover, antidote 5-2C reduced hemorrhage grade as well as
mortality after a subarachnoid hemorrhage (SAH) under the condition of intracranial hemorrhage. These aptamer-antidote pairs may be a novel and safer approach
for the treatment of stroke [83].
Sullenger and his colleagues elucidated the molecular mechanism of anti-FIXa
aptamer 9.3t. They found that the aptamer bound FIXa and blocked FX activation regardless of FVIIIa, thus increased the clotting time in human plasma. These
results showed that aptamer 9.3t blocked the interaction between FIXa and its macromolecular substrate while partly blocked interaction with small molecular substrate
cleavage active site probes. Thereby, unlike other small molecule drugs, aptamers
may bind surfaces surrounding an active site and therefore sterically interfere with
enzyme activity. Aptamers 9.3t may be applied to probe extended surfaces on target
proteins and to block substrate-binding exosites of enzymes. FIXa aptamer may be
a potent anticoagulant through inhibiting binding between FX and the FIXa-VIIIa
complex and FX activation in clinical settings [84].