** Shares of Mesoblast MSB.AX trims early session's gains, trades 1.1% higher at A$1.8
** Stock had risen as much as 4.5% to its highest level since May 5
** Biotechnology firm receives seven years of orphan-drug exclusive approval from U.S. Food and Drug Administration (FDA) for Ryoncil
** Ryoncil is used to treat of steroid-refractory acute graft versus host disease (SR-aGvHD) in pediatric patients 2 months of age and older, condition that can occur after a person gets a blood cell transplant
** About 7.7 million shares change hands by 0255 GMT, about 1.2x 30-day average
** Stock down 42.6% this year, as of last close
(Reporting by Sherin Sunny in Bengaluru)
((Sherin.Sunny@thomsonreuters.com;))