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New Platforms for Therapeutics

Ribozyme changes its name and hops on the RNAi bandwagon.

Sirna Therapeutics, a public company founded on ribozyme-based gene-silencing technology, is abandoning its original platform (and its original name, Ribozyme Pharmaceuticals) to focus on another, similar technology called RNA interference (RNAi). This makes Sirna one of at least a dozen companies that now market themselves with this fairly new and fashionable technology.

Compared to ribozyme technology, RNAi is immature; the naturally occurring process was identified in nematodes in 1998 and has been used for drug target validation just within the last three years. Only within the past year have researchers begun to develop the technology for therapeutics.

Like ribozymes and antisense, its antecedent technologies, RNAi is a method to shut down gene expression. Gene silencing in RNAi is mediated by double-stranded RNA (dsRNA). If a dsRNA segment is homologous to, or matches up with, a region within a gene, this dsRNA "interferes" with the expression of that gene by targeting its messenger RNA (mRNA, the intermediary between the gene and its protein product) for degradation. Interfering with mRNA stability thus holds great potential for therapeutics if it can block the production of the protein associated with a disease. Since discovering RNAi, researchers have quickly found it to be superior to ribozymes or antisense for use in gene-specific silencing, at least for target validation. The reasons for this are still debated, but it is assumed that, because the molecules responsible for RNAi utilize a natural mechanism in the cell, the technology has led to higher specificity, better efficacy, and lower toxicity. Investors in RNAi companies hope these features will lead to faster development of therapeutics.

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