By Mrinalika Roy (Reuters) – Bluebird bio’s blood disorder treatment demonstrates “clinically meaningful” benefit in patients, staff reviewers at the U.S. Food and Drug Administration said in briefing documents published on Tuesday. The company has applied for approval of beti-cel as a one-time gene therapy for the treatment of Beta-thalassemia patients dependent on blood transfusions. Data provided supports the effectiveness of beti-cel in these patients, the staff said https://www.fda.gov/media/159009/download, sending the company’s shares up 12% to $3.34. Through Monday’s close, the stock h…