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Antisense, RNAi, and gene silencing strategies for therapy: mission possible or impossible?

ABSTRACT: Antisense oligonucleotides can regulate gene expression in living cells. As such, they regulate cell function and division, and can modulate cellular responses to internal and external stresses and stimuli. Although encouraging results from preclinical and clinical studies have been obtained and significant progress has been made in developing these agents as drugs, they are not yet recognized as effective therapeutics. Several major hurdles remain to be overcome, including problems with efficacy, off-target effects, delivery and side effects. The lessons learned from antisense drug development can help in the development of other oligonucleotide-based therapeutics such as CpG oligonucleotides, RNAi and miRNA.

SUBMITTER: Rayburn ER

PROVIDER: S-EPMC2497463 | biostudies-literature | 2008 Jun

REPOSITORIES: biostudies-literature

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Antisense, RNAi, and gene silencing strategies for therapy: mission possible or impossible?

Rayburn Elizabeth R ER Zhang Ruiwen R

Drug discovery today 20080503 11-12

Antisense oligonucleotides can regulate gene expression in living cells. As such, they regulate cell function and division, and can modulate cellular responses to internal and external stresses and stimuli. Although encouraging results from preclinical and clinical studies have been obtained and significant progress has been made in developing these agents as drugs, they are not yet recognized as effective therapeutics. Several major hurdles remain to be overcome, including problems with efficac ...[more]

PMID: 18549978

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Project description:Objective:In children many antiepileptic drugs (AEDs) are prescribed off-label due to a lack of well-designed randomized controlled trials (RCTs). We conducted a multicenter RCT in the Netherlands to compare levetiracetam and valproic acid as monotherapy in children with newly diagnosed epilepsy. After 2 years, we had to stop this investigator-initiated trial prematurely because the inclusion rate was too low. We analyzed the reasons for this failure, assessed the various issues involved in performing RCTs in children, and now give recommendations for future studies. Methods:A questionnaire was completed by all investigators involved in the study. It included questions about the motivation to participate and the perceived reasons for recruitment failure. We also studied literature about financial, logistic, legal, and ethical aspects of RCTs in children. Results:Main reasons for recruitment failure were overestimation of the number of eligible AED-naive children referred by general pediatricians; personal preferences of investigators for specific antiepileptic drugs; and the extensive administrative load due to extra regulations and guidelines for children. Fundraising for investigator-initiated trials is difficult and the majority of RCTs concerning AEDs are sponsored by pharmaceutical companies. Involving children requires balancing between protection and participation; the randomization procedure and obtaining informed consent are complex for both children and parents. Significance:Performing RCTs with AEDs in children is important but complicated by logistic, regulatory, legal, and ethical restrictions. Based on our recent experience, our advice to colleagues who are planning a similar trial would be to perform a feasibility pilot study; to set up intensive collaboration with referring pediatricians; to arrange support of a clinical trials unit and a local research nurse during the complete trial period; and to incorporate the possibility of extending the recruitment period. Major investments, both financially from governmental organizations and in time, are imperative for independent RCTs in children.

Project description:BackgroundInsecticides are still at the core of insect pest and vector control programmes. Several lines of evidence indicate that ABC transporters are involved in detoxification processes against insecticides, including permethrin and other pyrethroids. In particular, the ABCG4 gene, a member of the G subfamily, has consistently been shown to be up-regulated in response to insecticide treatments in the mosquito malaria vector Anopheles stephensi (both adults and larvae).MethodsTo verify the actual involvement of this transmembrane protein in the detoxification process of permethrin, bioassays on larvae of An. stephensi, combining the insecticide with a siRNA, specifically designed for the inhibition of ABCG4 gene expression were performed. Administration to larvae of the same siRNA, labeled with a fluorescent molecule, was effected to investigate the systemic distribution of the inhibitory RNA into the larval bodies. Based on siRNA results, similar experiments using antisense Vivo-Morpholinos (Vivo-MOs) were effected. These molecules, compared to siRNA, are expected to guarantee a higher stability in environmental conditions and in the insect gut, and present thus a higher potential for future in-field applications.ResultsBioassays using two different concentrations of siRNA, associated with permethrin, led to an increase of larval mortality, compared with results with permethrin alone. These outcomes confirm that ABCG4 transporter plays a role in the detoxification process against the selected insecticide. Moreover, after fluorescent labelling, it was shown the systemic dissemination of siRNA in different body districts of An. stephensi larvae, which suggest a potential systemic effect of the molecule. At the same time, results of Vivo-MO experiments were congruent with those obtained using siRNA, thus confirming the potential of ABCG4 inhibition as a strategy to increase permethrin susceptibility in mosquitoes. For the first time, Vivo-MOs were administered in water to larvae, with evidence for a biological effect.ConclusionsTargeting ABCG4 gene for silencing through both techniques resulted in an increased pyrethroid efficacy. These results open the way toward the possibility to exploit ABCG4 inhibition in the context of integrated programmes for the control An. stephensi mosquitoes and malaria transmission.

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Antisense, RNAi, and gene silencing strategies for therapy: mission possible or impossible?

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Antisense, RNAi, and gene silencing strategies for therapy: mission possible or impossible?

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