** Metsera MTSR.O shares plunge 15.7% to $70.12 premarket after a fierce bidding war for the drugmaker ended late on Friday

** MTSR accepts Pfizer's PFE.N $10 bln acquisition bid, and co-bidder Novo Nordisk NOVOb.CO said it would exit the race

** PFE agrees to pay $86.25/share in cash, a 3.69% upside to Metsera's Friday close

** Metsera accepted Pfizer's sweetened offer citing "unacceptably high legal and regulatory risks" in Novo's bid

** Bernstein says Pfizer's $10 billion valuation is optimistic, requiring $11 billion in revenue by 2040

** MTSR shares had surged nearly 60% last week amid bidding war

** MTSR shares have climbed more than threefold since their January IPO, while PFE stock is down 7.82% YTD, as of last close

(Reporting by Tharuniyaa Lakshmi and Pranav Kashyap in Bengaluru)

((tharuniyaa@thomsonreuters.com))