RNA as a drug target: recent patents on the catalytic activity of trans-splicing ribozymes derived from group I intron RNA.

The importance of RNA in vital cellular events like gene expression, transport, self-splicing catalytic activity etc., renders them an alternative target for drugs and other specific RNA binding ligands. RNA targets gain significance for the fact that targeting DNA with therapeutics sooner leads to drug resistance and severe side effects by impairing essential function of the genes. However the unique structural features of the RNA facilitate targeting in two different approaches: 1) targeting the catalytic activity of the RNA (ribozyme) 2) exploiting the catalytic functions of ribozyme to target other cellular RNA of our interest. The first strategy leads to the inhibition of ribozyme catalysis by small molecule drugs or RNA binders. This would be very much effective in terms of unique target for specific RNA binders as ribozymes are present in certain pathogens and nonexistent in humans. Apart from targeting ribozymes by therapeutics the second strategy explores that ribozymes by itself can act as therapeutics to correct the defective cellular RNA by trans-splicing activity and are renowned as equivalent as that of any gene therapy for genetic disorders or it can be a "gene inhibitor" as it can cleave the target RNA. In this series many trans-splicing ribozymes are engineered and patented for their vital catalytic activity. However here the focus has been given to recent patents on group I intron-derived trans-splicing ribozymes, and their catalytic functions as therapeutics are discussed.