Elan plans to spin-off of its discovery sciences unit from the main company. The transaction will create two independent public companies, Elan Corp. plc and Neotope Biosciences plc. Subject to certain conditions, the spin-offs will be complete by the end of 2012.   Elan Corp. will initially consist of three main assets: Tysabri (marketed in collaboration with Biogen Idec) for Multiple Sclerosis and other potential indications; ELND005, a small molecule in Phase II for a range of neuropsychiatry...