Roche will pay $74 a share for InterMune, which represents a 38% premium to Friday's closing price of $53.80, in an all-cash deal.
Ariad was up 6.43% to $6.62 at 12:35 p.m. More than 8.3 million shares had changed hands to edge the average volume of 8,129,760.
Must Read: Warren Buffett's 25 Favorite Stocks
EXCLUSIVE OFFER: See inside Jim Cramer's multi-million dollar charitable trust portfolio to see the stocks he and Stephanie Link think could be potentially HUGE winners. Click here to see the holdings for FREE.