89bio soars on Roche's deal to buy co for up to $3.5 bln

** Shares of biotech firm 89Bio ETNB soar 85% to $14.95 premarket

** Swiss drugmaker Roche (ROGS.S) to acquire co in a deal worth about $2.4 bln, which could go up to $3.5 billion when including a non-tradeable contingent value right

** ROGS to buy ETNB common shares for $14.50 a piece, representing a premium of about 80% to stock's last close, as per Reuters' calculations

** Swiss co says 89Bio could also receive payments of $6 per share, if certain milestones are met

** ETNB valued at $1.2 bln, as per last close on Wednesday, according to data compiled by LSEG

** ROGS says deal to help co grow in a field related to booming weight-loss market

** Up to last close, ETNB up 3.32% YTD, compared with Nasdaq Biotechnology Index's NNBI 10.13% gain