While Mirus, of Madison, Wis., touts itself on its website as a non-viral gene transfer company, selling tools for nucleic acid (including siRNA) transfection and labeling, the privately held company is also quietly trying to get into the business of making RNAi-based therapeutics.

But unlike most of the other RNAi-as-drugs firms, which develop siRNAs against specific targets and then try to figure out how to administer them, Mirus aims at perfecting its delivery methods first and going from there.