Silence Therapeutics, formerly SP Pharma plc, is a European RNAi therapeutics company that is developing novel, proprietary siRNA molecules, AtuRNAi, and a proprietary systemic delivery system, AtuPLEX. The company was formed in October 1994 to act as a publicly traded holding company for Stanford Rook Ltd, a drug development company spun out from University College London. Stanford Rook Ltd specializes in immunotherapy and in particular developing products based upon Mycobacterium vaccae. The Company came into its current form in July 2005 when it acquired Atugen AG a company specializing in RNAi technology. In 2007, Silence Therapeutics changed its name from SP Pharma plc. Silence Therapeutics plc has two operating subsidiaries; Silence Therapeutics AG and Stanford Rook Limited. Silence Therapeutics is based in London, UK, and Berlin, Germany, and is listed on AiM (LSE:SLN).

Acquired Companies: Intradigm Corporation, SR Pharma plc