** Shares of biotech firm Chimerix CMRX.O rise 70.2% to $8.42 premarket

** Jazz Pharmaceuticals JAZZ.O will acquire Chimerix for about $935 million to gain access to its experimental drug to treat a rare brain tumor, the companies say

** JAZZ will pay $8.55 per Chimerix share in an all-cash deal, which is expected to close in Q2; represents around 72% premium to its Tuesday's closing price

** CMRX has risen 320% in the past 12 months

(Reporting by Siddhi Mahatole)

((siddhi.mahatole@thomsonreuters.com))