Bluebird Bio (BLUE) - Get Report removed a significant concern investors had about its gene therapy manufacturing process, sending shares higher Thursday.

The company announced the start of a new phase III study of its LentiGlobin gene therapy in patients with beta thalassemia, a rare blood disorder. Most importantly, Bluebird said the new study incorporates changes to the way LentiGlobin is made, aimed at improving the number of corrected genes infused into patients and boosting efficacy.

The U.S. Food and Drug Administration is allowing Bluebird to treat beta thalassemia patients with the revamped LentiGlobin gene therapy without requiring the company to start over with new preclinical data. This eliminates a lingering concern on the Street that Bluebird's gene therapy studies would be significantly delayed by the manufacturing changes.

Bluebird shares rose 6% To $55.89 in Thursday trading.

Bluebird announced last December that it was making improvements to its LentiGlobin gene therapy following disappointing results from the previous version.

The phase III study will enroll 15 patients with transfusion-dependent beta thalassemia, all of whom will be treated with the LentiGlobin gene therapy. The study's primary endpoint is transfusion independence, defined as a 12-month transfusion-free period after infusion with LentiGlobin.

If the study yields positive results, Bluebird will use the data as the basis for an approval filing in the U.S. European regulators are allowing Bluebird to seek approval there on the basis of an already ongoing study, but this new study will be confirmatory.

Bluebird also intends to incorporate the improved LentiGlobin into an ongoing study of sickle cell patients.

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