Pharmaceutical giant GlaxoSmithKline has negotiated a deal to develop drugs aimed at four microRNA molecules that have been linked to inflammatory diseases such as rheumatoid arthritis and inflammatory bowel disease. The agreement, with Regulus Therapeutics in Carlsbad, California, marks the first time a large pharmaceutical company has announced a collaboration that is exclusively focused on microRNAs, which silence genes by intercepting messenger RNA molecules.

Unlike small interfering RNAs that also work in this way, microRNAs usually downregulate expression of many genes at once. They have thus been associated with diseases involving multiple changes in gene expression, including cancer and viral infections.

Regulus will initially earn US$20 million from the alliance, and then receive up to $144.5 million more for each of the four microRNA targets for which it meets drug-development milestones.