One of the more important recent advances in antisense technology has been the demonstration the importance of protein binding to the pharmacological effects of ASOs or siRNAs that contain phophorothioates. Said simply: proteins determine the fate of PS ASOs (and siRNAs) in biological systems and PS ASOs (and siRNAs) can affect the fates of many of the proteins with which they interact. This means that if one finds a PS ASO located at a site in an animal or in a cell, there is a protein or proteins responsible for it being there. Furthermore, protein interactions are the factors determining in vivo distribution, cellular uptake and distribution and they may have significant affects on pharmacological and to toxicological effects as well. Remarkably, we have rapidly learned a great deal about the biochemistry of PS ASO-protein interactions and how to mitigate undesirable protein binding and protein mediated effects such as toxicity. We have also shown that PS ASOs can cause proteins to re-localize in cells and form a variety of, protein or RNP-ASO aggregates in cells and determined the compositions of several of these aggregates. Many of these lessons were recently summarized in a review my colleagues and I published in Nucleic Acid Research this year Crooke, S.T., et al., NAR, 2020.
Because of broad interest in our work, I was recently asked to write a perspectives article for JACs which is the “bible” for chemists. What I like about this article is that it gave me the opportunity to speculate a bit about what it all means and to pose some “next-generation “questions which we are busy answering. My colleagues and I have also recently written several more general reviews, in which we put the protein binding story holistically into a broad technological context and each review has a different focus. As they are published, I will write brief blogs to introduce them to those who are interested. Crooke, et al., JACS, 2020