Thermodynamic criteria for high hit rate antisense oligonucleotide design

Antisense oligonucleotides are used for therapeutic applications and in functional genomic studies. In practice, however, many of the oligonucleotides complementary to an mRNA have little or no antisense activity. Theoretical strategies to improve the 'hit rate' in antisense screens will reduce the cost of discovery and may lead to identification of antisense oligonucleotides with increased potency. Statistical analysis performed on data collected from more than 1000 experiments with phosphorothioate-modified oligonucleotides revealed that the oligo-probes, which form stable duplexes with RNA (DeltaG(37)(o) less than or equal to -30 kcal/mol) and have small self-interaction potential, are more frequently efficient than molecules that form less stable oligonucleotide-RNA hybrids or more stable self-structures. To achieve optimal statistical preference, the values for self-interaction should be (DeltaG(37)(o)) greater than or equal to -8 kcal/mol for inter-oligonucleotide pairing and (DeltaG(37)(o)) greater than or equal to -1.1 kcal/mol for intra-molecular pairing. Selection of oligonucleotides with these thermodynamic values in the analyzed experiments would have increased the 'hit rate' by as much as 6-fold.