** Commercial insurer W.R. Berkley's shares WRB.N fall ~1% to $70.47

** BofA Global Research downgrades WRB to "neutral" from "buy" following the recent stock surge

** WRB shares surged 7.5% on Friday to close at $71.27 after Japanese property and casualty insurance carrier Mitsui Sumitomo Insurance agreed to purchase 15% of the company's shares

** Brokerage says WRB shares are more closely nearing full valuation, despite advantages over its peer group

** Says Japanese insurer's move doesn't seem to be a prelude to a buyout in the foreseeable future, but it could signal an option for the very long-term

** 8 of 18 brokerages rate the stock "buy" or higher, 9 "hold" and 1 "sell"; median PT $68 - data compiled by LSEG

** As of last close, WRB stock up 21.6% YTD

(Reporting by Arasu Kannagi Basil in Bengaluru)

((ArasuKannagi.Basil@thomsonreuters.com;))