Editorial [Hot Topic: Modified Nucleic Acid Substructures in Medicinal Chemistry and Drug Development (Guest Editor: Dr. Vaijayanti A. Kumar)]

It gives me great pleasure to forward this special theme issue devoted to the topic, ‘Modified Nucleic Acids as Substructures in Medicinal Chemistry and Drug Development’. With the discovery of siRNA being recognized by Nobel Prize in medicine in 2006, the topic warrants such attention. The collection of papers, contributed by several leading researchers, illustrates the generation of therapeutically driven chemical entities as mimics of nucleic acids. The common objective in each case is the evolution of nucleic acids into therapeutically viable oligonucleotide (ON) structures and to find some straightforward answers to several technical challenges. Each contributor has surpassed milestones on diverse roadmaps that lead to a common destination i.e application of antisnese (AS) principle for the therapeutic solution to several untreatable diseases. The authoritative articles by the contributors summarize their own research work and also aptly take note of the current relevant literature. Prakash and Bhat focus on the progress made in RNase H mediated antisense approach, Summerton comprises the morpholinos, their application and comparison with S-oligos, Koizumi details the ONs with restricted geometry in N-sugar conformation. Peptide nucleic acid, PNA, the highly competent DNA mimic is further exploited in application perspective. We have two distinct articles dedicated to the nucleobase and backbone PNA modifications by Hudson and Corradini, respectively. The P-chirality is a major issue in the phosphodiester modifications in ONs and Guga has extensively reviewed this topic for both chemistry and biology. Ganesh and myself divulge upon the literature that highlights nucleic acid structure-editing for RNA selectivity and the logic behind such selection. In addition to the knockdown/down-regulating AS therapeutics, the corrective AS principle needs such selection where small molecular therapies are not common. The important bottleneck for application of modified ONs as medicines is their cellular delivery. Lebleu and co-authors have given sufficient attention to the various ways of realizing this in their article. Considering the nature of the special issue, there are certain quite understandable overlaps, but authors have treated the topics in different perspectives. The issue thus covers concise efforts towards a common goal. It is interesting to see that we have articles from Canada, France, India, Italy, Japan, Russia, U.K. and U.S.A. that also incidentally represent all the continents. I hope this gives a comprehensive picture of today's modified oligonucleotide substructures and to some extent their biological evaluation. I trust that the readers will enjoy the special issue and it will be beneficial for the future research initiatives. I owe all the contributors special thanks for their efforts. I am personally grateful to Bentham Science Publications for giving me this opportunity to bring out this issue.