** Shares of Sarepta Therapeutics SRPT.O up 6.1% at $123.32 early Thurs as co set to join S&P MidCap 400 index .IDX week
** Stock tracking biggest daily pct gain since Apr 24
** SRPT to replace Shockwave Medical Inc SWAV.O in IDX effective Mon, Jun 1, according to S&P Dow Jones Indices announcement
** Shockwave being acquired by Johnson & Johnson JNJ.N in $13 bln deal
** Sarepta has current market cap of approx $11.7 bln, LSEG data shows
** Earlier this month, Sarepta said U.S. FDA to decide on application seeking traditional approval for Elevidys, its muscle-wasting disorder gene therapy by June 21
** With move on the session, SRPT up ~28% YTD and up ~50% over the past six months
** Avg rating among 22 analysts covering stock is "buy" and median PT is $168 - LSEG
(Lance Tupper is a Reuters market analyst. The views expressed are his own)
((lance.tupper@thomsonreuters.com
lance.tupper@tr.com 1-646-279-6380))