(Updates)
** Shares of drug developer Prometheus Biosciences Inc
RXDX.O hit a record high; stock last up 69.3% at $192.98
** Merck & Co Inc MRK.N said on Sunday it would buy RXDX
for about $10.8 bln, as the drugmaker 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
** About 5.5 mln shares change hands, more than 10 times the
stock's monthly average trading volume
** MRK shares down 0.2% at $115.05
** RXDX stock up 75.28% YTD
(Reporting by Rupali Chaudhary in Bengaluru)
((Rupali.chaudhary@thomsonreuters.com))