** OneSpaWorld Holdings' OSW.O shares up 6% at $21.26 before the bell ahead of health and wellness services firm's addition to S&P SmallCap 600 index .SPCY next week

** OSW to replace Dynavax Technologies DVAX.O in SPCY prior to market open on Tues, Feb 10, per S&P Dow Jones Indices

** DVAX being acquired by French drugmaker Sanofi SASY.PA in $2.2 bln deal expected to close soon

** Bahamas-based OSW has ~102 mln shares outstanding for about $2 bln market cap

** Last month, co issued preliminary Q4 and FY rev below consensus estimates and said it's in process of exiting its land-based operations in Asia

** Through Weds close, OSW shares off 3% YTD

** All 5 analysts covering the stock are bullish, including 3 "strong buy" ratings; median PT $25, per LSEG

(Lance Tupper is a Reuters market analyst. The views expressed are his own)

((lance.tupper@tr.com 1-646-279-6380))