** U.S. shares of Bellus Health Inc BLU.O surge 97.6% at
$14.35 premarket - biggest pct gainer across U.S. stock
exchanges
** GSK GSK.L plans to buy the Canada-based drug developer
in an all-cash deal for $2 billion as the British drugmaker
expands its bet on respiratory therapies
** GSK's offer of $14.75/share is more than double BLU's
closing price of $7.26/share on Nasdaq on Monday
** Through the deal, GSK gains access to BLU's experimental
drug, camlipixant, which is in late-stage development as a
treatment for refractory chronic cough
** BLU deal expands GSK's existing respiratory portfolio,
including Nucala and Trelegy, which together generated more than
3 bln pounds ($3.73 bln) last year
** As of last close, U.S. shares of BLU were down ~12% YTD
(Reporting by Khushi Mandowara in Bengaluru)
((Khushi.Mandowara@thomsonreuters.com;))