** Shares of Prometheus Biosciences Inc RXDX.O surge 70.2%
to $194.01 premarket
** Merck & Co Inc MRK.N will buy RXDX for about $10.8 bln,
the drugmaker said on Sunday, as builds up its presence in the
market for therapies targeting disease of the immune system
** MRK to pay $200/shr, a 75% premium to Prometheus' last
closing price
** Through the deal, MRK gains access to RXDX's experimental
drug PRA023, which is being tested to treat ulcerative colitis
and Crohn's disease
** RXDX shares have more than tripled since co reported
positive data from two mid-stage studies of PRA023 in December
(Reporting by Manas Mishra)
((Manas.Mishra@thomsonreuters.com;))