Regenerative medicine company Mesoblast Ltd.’s stock sank nearly 57% on the news that it received a second U.S. FDA complete response letter (CRL) following the resubmission of its BLA for allogeneic stem cell treatment remestemcel-L in children with steroid-refractory acute graft-vs.-host disease. In the CRL, issued a few days after the Aug. 2 PDUFA date, the agency said it requires more data to support approval.