** Amneal Pharmaceuticals AMRX.O shares up 3.4% premarket to $14.30 as it's set to join S&P SmallCap 600 index .SPCY this week

** AMRX, maker of generic and specialty prescription drugs, to replace TTM Technologies TTMI.O in SPCY before the bell on Fri, Jan 30, S&P Dow Jones Indices said late Tues

** Printed circuit board maker TTMI migrating to S&P MidCap 400 .IDX to replace Civitas Resources CIVI.N, which is being acquired by SM Energy SM.N

** Stephens analyst Melissa Roberts points out in a note that she expects passive funds will need to buy ~22.9 mln AMRX shares, equating to 13 days of implied buying demand

** Bridgewater, New Jersey-based AMRX has ~314.4 mln shares outstanding for roughly $4 bln market cap

** Through Tues close, shares up about 60% over the past year

** All 5 analysts rate the stock "buy"; median PT $15, per LSEG data

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

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