bluebird may miss sickle cell gene therapy goal waiting for FDA feedback

March 30, 2023

Massachusetts-based biotech bluebird bio announced this week that due to communication delays from the FDA, it is likely to miss its action goal date for its sickle cell disease gene therapy candidate, lovo-cel.

“Our file is completely written and ready for submission, but we are awaiting feedback from the FDA on CMC [chemistry, manufacturing and controls], the company’s CEO Andrew Obenshain said on a conference call, adding, “speaking plainly, we will likely miss the Q1 2023 submission goal.” 

Lovo-cel is a personalized gene therapy treatment, in which the patents own blood stem cells are modified with a virus to add a new version of a gene, which is supposed to help prevent sickle cell anemia. Because bluebird bio has refined its manufacturing processes for the drug as it has developed, the agency asked for comparability data from its CMC practices in both commercial manufacturing facilities as well as clinical trials. 

In the call, Obenshain explained that in December the company completed a drug product comparability analysis, for which they received feedback from the FDA in February. Bluebird says they responded the first week of March, and while the FDA has committed to a timely response, there is no set timeline.

Bluebird remains optimistic. “Our clinical data reflects the most robust data available with the longest follow-up across any gene therapy program for sickle cell disease,” Obenshain said, “We believe that this could ultimately set the stage for a smooth review.”

During the 2-year study, 28 out of 29 patients who received lovo-cel infusion achieved complete resolution of their severe Vaso-Occlusive Events (VOEs), which are painful episodes that occur in individuals with sickle cell disease and can cause organ damage and other complications. This result was compared to 3.5 annual VOEs that occurred in the 2 years prior to the patients' enrollment in the study. In a long-term follow-up study, no severe VOEs were reported and certain markers of hemolysis, which is the breakdown of red blood cells, approached normal levels.