1. Field of the Invention
The present invention relates to novel oligonucleotide analogues, which exhibit antisense or antigene activity having excellent stability, or exhibit excellent activity as a detection agent (probe) for a specific gene or as a primer for starting amplification, and to novel nucleoside analogues which are intermediates for their production.
2. Background Information
Oligonucleotide analogues, which have excellent antisense or antigene activity and which are stable in the body are expected to be useful pharmaceuticals. In addition, oligonucleotide analogues having a high degree of stable complementary chain formation ability with DNA or mRNA are useful as detection agents for a specific gene or as primers for starting amplification.
In contrast, naturally-occurring oligonucleotides are known to be quickly decomposed by various nucleases present in the blood and cells. In some cases, naturally-occurring oligonucleotides may not have sufficient sensitivity for use as detection agents for specific genes or as primers for starting amplification due to limitations on their affinity with complementary base sequences.
In order to overcome these shortcomings, various non-naturally-occurring oligonucleotide analogues have been produced, and have been attempted to be developed for use as pharmaceuticals or detection agents for specific genes. Namely, known examples of such non-naturally-occurring oligonucleotide analogues include those in which an oxygen atom attached to a phosphorus atom in a phosphodiester bond of an oligonucleotide is replaced with a sulfur atom, those in which said oxygen atom is replaced with a methyl group, those in which said oxygen atom is replaced with a boron atom, and those in which a sugar moiety or base moiety of an oligonucleotide is chemically modified. For example, ISIS Corp. has developed thioate-type oligonucleotide ISIS2922 (Vitravene) as a therapeutic agent for human cytomegalovirus retinitis and ISIS2922 has been put on the open market in the United States.
However, in consideration of the potency of the antisense or antigene activity in the above non-naturally-occurring oligonucleotide analogues, namely the ability to form a stable complementary chain with DNA or mRNA, stability with respect to various nucleases, and the manifestation of adverse side effects due to non-specific bonding with various proteins in the body, there has been a need for a non-naturally-occurring oligonucleotide analogue having even better stability in the body, a low incidence of adverse side effects and a high ability to form complementary chains.