Alnylam, Merck and Sanofi’s Genzyme division played a bit of RNA musical chairs over the weekend, centering on Alnylam’s pipeline.

Among the moves of note: Sunday’s news that Merck sold Sirna Therapeutics to Alnylam, which will add RNAi therapies and siRNA-conjugates to Alnylam’s portfolio of fully owned assets. Merck gets $175 million from the deal, as well as up to $105 million in development and sales milestones and a single-digit cut of royalties for some candidates Merck had a hand in developing.

Meanwhile, Sanofi announced Monday that it put $700 million toward Alnylam’s pipeline, which will give Sanofi’s Genzyme division “significant rights to Alnylam’s portfolio of clinical and pre-clinical stage drug candidates.”

Alnylam and Genzyme paired up in 2012 to develop patisiran for the rare disease transthyretin familial amyloid polyneuropathy. Monday’s news gives Genzyme greater rights to this drug, the right to commercialize three Alnylam pipepline items, and the option to develop and commercialize all rare genetic-disease drugs outside of North America and Western Europe until 2020.