308
W. Li et al.
and anemia were observed in this study [128]. Further study has been terminated due
to slow enrollment. (NCT00742612) (https://clinicaltrials.gov).
Convergent SELEX techniques were applied to isolate several RNA aptamers
targeting vWF with high affinity, which can significantly inhibit vWF-mediated
platelet adhesion and aggregation. They demonstrated that these aptamers identified
and bound to the same A1 region of vWF (SPI and SPIII fragments) associated with
platelet aggregation. The interaction of vWF-platelet GPIb and platelet adhesion
to subendothelial collagen were disturbed, and a key signal transduction pathway
leading to platelet aggregation through GP IIb/IIIa was blocked [129, 130]. They
demonstrated that two 40 nucleotides aptamer clones vWF R9.3 (targeting vWF
SPIII domain) and R9.14 (targeting both the vWF SPI and SPIII domains) inhibited
platelet aggregation at concentrations higher than 40 nM in a PFA-100 assay and
ristocetin-induced platelet aggregation assays as measured by RIPA at concentrations higher than 250 nM. They had no effect in other agonist-mediated aggregation
assays [131]. Moreover, these aptamers were evaluated in ristocetin, ADP, thrombin
(SFLLRN peptide), and collagen-mediated platelet aggregation assays. The experiments showed that both clones R9.3 and R9.14 inhibited platelet aggregation through
blockage of GP Ib-IX-V-vWF interaction, which is important for high shear stress
areas. Furthermore, several antidote oligonucleotides were designed to improve the
safety of aptamer R9.14. Antidote oligonucleotide 6 (AO6) was the most effective
one that could rapidly and completely reverse the antiplatelet activity of aptamer
R9.14 to background levels and restore platelet function, and was effective for at
least 4 h in a PFA-100 assay. This aptamer-antidote pair can potentially give physicians a rapid, effective, safer, and continual means to regulate antiplatelet therapy
[131].
Nimjee et al. reported a potent antiplatelet agent, RNA aptamer Ch-9.14-T10
against vWF that attenuated thrombosis in a murine model of FeCl 3 vascular injury
thrombosis. Aptamer Ch-9.14-T10 could maintain vessel patency for more than
1 h and histopathologic analysis showed a minimal platelet accumulation at the
damaged carotid artery. They further developed the antidotes that could rapidly
reverse the antiplatelet activity of Ch-9.14-T10 to improve the safety profile of
aptamers. The results showed that antidote oligonucleotides and β-cyclodextrin
containing polycation (CDP) both reversed the antiplatelet effect of the aptamer
in vitro. They also demonstrated that antidote oligonucleotides Aos and universal
antidotes could neutralize the antiplatelet activity of Ch-9.14-T10 in mice model and
thereby prevented bleeding in surgically challenged animals. The vWF aptamer and
its antidotes could enable clinicians to improve the medical management of patients
who require antiplatelet treatment in the perioperative setting [118].
In a study, ARC5692 (anti-P-selectin aptamer) and ARC15105 (anti-vWF
aptamer) were both compared to standard LWMH and enoxaparin to test the
inhibitory efficacy of P-selectin or vWF in promoting thrombus resolution and
preventing vein wall fibrosis in a baboon model of venous thrombosis. Animal models
received prophylactic aptamers ARC5692 and ARC15105 demonstrated improved
vein recanalization by MRV, suggesting both aptamers improved valve function but
ARC5692 improved iliac vein recanalization better than ARC15105 and enoxaparin.
W. Li et al.
and anemia were observed in this study [128]. Further study has been terminated due
to slow enrollment. (NCT00742612) (https://clinicaltrials.gov).
Convergent SELEX techniques were applied to isolate several RNA aptamers
targeting vWF with high affinity, which can significantly inhibit vWF-mediated
platelet adhesion and aggregation. They demonstrated that these aptamers identified
and bound to the same A1 region of vWF (SPI and SPIII fragments) associated with
platelet aggregation. The interaction of vWF-platelet GPIb and platelet adhesion
to subendothelial collagen were disturbed, and a key signal transduction pathway
leading to platelet aggregation through GP IIb/IIIa was blocked [129, 130]. They
demonstrated that two 40 nucleotides aptamer clones vWF R9.3 (targeting vWF
SPIII domain) and R9.14 (targeting both the vWF SPI and SPIII domains) inhibited
platelet aggregation at concentrations higher than 40 nM in a PFA-100 assay and
ristocetin-induced platelet aggregation assays as measured by RIPA at concentrations higher than 250 nM. They had no effect in other agonist-mediated aggregation
assays [131]. Moreover, these aptamers were evaluated in ristocetin, ADP, thrombin
(SFLLRN peptide), and collagen-mediated platelet aggregation assays. The experiments showed that both clones R9.3 and R9.14 inhibited platelet aggregation through
blockage of GP Ib-IX-V-vWF interaction, which is important for high shear stress
areas. Furthermore, several antidote oligonucleotides were designed to improve the
safety of aptamer R9.14. Antidote oligonucleotide 6 (AO6) was the most effective
one that could rapidly and completely reverse the antiplatelet activity of aptamer
R9.14 to background levels and restore platelet function, and was effective for at
least 4 h in a PFA-100 assay. This aptamer-antidote pair can potentially give physicians a rapid, effective, safer, and continual means to regulate antiplatelet therapy
[131].
Nimjee et al. reported a potent antiplatelet agent, RNA aptamer Ch-9.14-T10
against vWF that attenuated thrombosis in a murine model of FeCl 3 vascular injury
thrombosis. Aptamer Ch-9.14-T10 could maintain vessel patency for more than
1 h and histopathologic analysis showed a minimal platelet accumulation at the
damaged carotid artery. They further developed the antidotes that could rapidly
reverse the antiplatelet activity of Ch-9.14-T10 to improve the safety profile of
aptamers. The results showed that antidote oligonucleotides and β-cyclodextrin
containing polycation (CDP) both reversed the antiplatelet effect of the aptamer
in vitro. They also demonstrated that antidote oligonucleotides Aos and universal
antidotes could neutralize the antiplatelet activity of Ch-9.14-T10 in mice model and
thereby prevented bleeding in surgically challenged animals. The vWF aptamer and
its antidotes could enable clinicians to improve the medical management of patients
who require antiplatelet treatment in the perioperative setting [118].
In a study, ARC5692 (anti-P-selectin aptamer) and ARC15105 (anti-vWF
aptamer) were both compared to standard LWMH and enoxaparin to test the
inhibitory efficacy of P-selectin or vWF in promoting thrombus resolution and
preventing vein wall fibrosis in a baboon model of venous thrombosis. Animal models
received prophylactic aptamers ARC5692 and ARC15105 demonstrated improved
vein recanalization by MRV, suggesting both aptamers improved valve function but
ARC5692 improved iliac vein recanalization better than ARC15105 and enoxaparin.