Phosphorothioate monoester modified oligomers

#The present invention relates to oligomeric compounds having at least one phosphorothioate monoester modification. The oligomeric compounds of the present invention typically have enhanced RNase H activation properties compared to oligomeric compounds without the modification. The oligomeric compounds are useful for investigative and therapeutic purposes.

#It is well known that most of the bodily states in mammals, including most disease states, are affected by proteins. Classical therapeutic modes have generally focused on interactions with such proteins in an effort to moderate their disease-causing or disease-potentiating functions. Recently, however, attempts have been made to moderate the actual production of such proteins by interactions with molecules that direct their synthesis, such as intracellular RNA. By interfering with the production of proteins, maximum therapeutic effect and minimal side effects may be realized. It is the general object of such therapeutic approaches to interfere with or otherwise modulate gene expression leading to undesired protein formation.

#One method for inhibiting specific gene expression is the use of oligonucleotides. Oligonucleotides are now accepted as therapeutic agents with great promise. Oligonucleotides are known to hybridize to single-stranded DNA or RNA molecules. Hybridization is the sequence-specific base pair hydrogen bonding of nucleobases of the oligonucleotide to the nucleobases of the target DNA or RNA molecule. Such nucleobase pairs are said to be complementary to one another. The concept of inhibiting gene expression through the use of sequence-specific binding of oligonucleotides to target RNA sequences, also known as antisense inhibition, has been demonstrated in a variety of systems, including living cells. See, Wagner et al., Science (1993) 260: 1510-1513; Milligan et al., J. Med. Chem., (1993) 36:1923-37; Uhlmann et al., Chem. Reviews, (1990) 90:543-584; Stein et al., Cancer Res., (1988) 48:2659-2668.

#General:

#Phosphoramidites (including 5′-DMT-thymidine-3′-O-(2-cyanoethyl)-N,N-diisopropylphosphoramidite; 5′-DMT-N2-isobutyryl-2′-deoxyguanosine-3′-O-(2-cyanoethyl)-N,N-diisopropylphosphoramidite; 5′-DMT-N4-benzoyl-2′-deoxycytidine-3′-O-(2-cyanoethyl)-N,N-diisopropylphosphoramidite; and 5′-DMT-N6-benzoyl-2′-deoxy-adenosine-3′-O-(2-cyanoethyl)-N,N-diisopropylphosphoramidite) and other reagents used in the automated synthesis of oligonucleotides were purchased from commercial sources (Glen Research, Sterling, Va.; Amersham Pharmacia Biotech Inc., Piscataway, N.J.; Cruachem Inc., Aston, Pa.; Chemgenes Corporation, Waltham, Mass.; Proligo LLC, Boulder, Colo.; PE Biosystems, Foster City Calif.; Beckman Coulter Inc., Fullerton, Calif.).

#General Procedure for the Preparation of an Oligomeric Compound having a Phosphorothioate Monoester at the 3′-Terminus (Preparation of Deoxyphosphorothioate: SEQ ID NO: 1, GCCCAAGCTG GCATCCGTCA, ISIS #2302)