** Shares of Mesoblast MSB.AX slumps as much as 58.3% to
A$0.455, on track for worst day ever, if losses hold
** Drug developer says it got a response from US FDA for its
Biologics License Application for remestemcel-L, used for
treatment of pediatric steroid refractory acute graft versus
host disease
** MSB says US FDA requires more data to support the market
approval
** Co says it will conduct a targeted, controlled study to
obtain the data needed to support approval
** Stock hits its lowest since Aug. 10, 2005
** Stock is the biggest percentage loser on the ASX All
Ordinaries index .AORD
** Stock has risen 25.3% this year as of last close
(Reporting by Navya Mittal in Bengaluru)
((navya.mittal@thomsonreuters.com))