Characterization of Target mRNA Reduction Through In Situ RNA Hybridization in Multiple Organ Systems Following Systemic Antisense Treatment in Animals

Advances in the medicinal chemistry of antisense oligonucleotide drugs have been instrumental in achieving and optimizing antisense activity in cell types other than hepatocytes, the cell type that is most sensitive to antisense effects following systemic treatment. To broadly characterize the effects of antisense drugs on target messenger RNA (mRNA) levels in different organs and cell types in animals, we have developed a sensitive RNA in situ hybridization technique using the noncoding RNA metastasis associated lung adenocarcinoma transcript 1 (MALAT1) as a surrogate target. We have used this technique to evaluate the effects of 2'-O-methoxy ethyl (MOE) and constrained ethyl bicyclic nucleic acid (cEt) gapmer antisense oligonucleotides (ASOs). ASO tissue distribution was also characterized using immunohistochemical techniques, and MALAT1 mRNA reductions were confirmed by quantitative real time-polymerase chain reaction. Our findings demonstrate that systemic antisense drug administration in both mice and non-human primates resulted in marked reductions in MALAT1 RNA in many tissues and cell types other than liver including kidney, muscle, lung, adipose, adrenal gland, and peripheral nerve tissue. As expected, ASOs with cEt chemistry were more efficacious than MOE ASO in all tissues examined.