Dive Brief:

  • Bluebird bio is likely to miss its goal for submitting an experimental gene therapy for sickle cell disease to the Food and Drug Administration by the end of this month, disclosing Wednesday that it’s still awaiting feedback from the agency on how it manufactures the treatment.


  • On a conference call, Bluebird CEO Andrew Obenshain said his company “continue[s] to progress” its application for the therapy, known as lovo-cel. “But, speaking plainly, we will likely miss the Q1 2023 submission goal,” he added. “Our file is completely written and ready for submission, but we are awaiting feedback from the FDA on [chemistry, manufacturing and controls].”


  • The feedback relates to data Bluebird submitted to the agency comparing production processes it used in clinical testing of lovo-cel to those it plans to use if the therapy is approved for commercial sale. The FDA responded with further questions in February, to which Bluebird replied in March. The company anticipates hearing back “within a matter of weeks.”

Dive Insight:

Bluebird is now several months into launching two rare disease gene therapies for which it won FDA approval last fall. But its progress on that front was overshadowed Wednesday by news of the delay for the company’s sickle cell treatment, which is viewed by analysts and investors as more consequential to its future success as a business.

Bluebird expects the delay to be slight, emphasizing that it continues to forecast an expedited FDA review of lovo-cel and, if approved, an early 2024 launch. Still, it’s another setback for a program that’s hit a number of clinical and safety-related hurdles as it has progressed through development.

Shares in Bluebird, which are a fraction of what they were worth several years ago, fell by more than 25% in Wednesday morning trading.

“While there is no set timeline for the FDA to respond, the agency has made a commitment to a timely response,” said Obenshain. “We believe that this could ultimately set the stage for a smooth review.”

In testing, lovo-cel showed the potential to dramatically alter the impact of sickle cell, an inherited blood disorder that causes debilitating pain crises and over time can damage organs. The treatment consists of a patient’s own stem cells, which are removed from the body and altered to express a gene that produces anti-sickling hemoglobin protein.

Because it’s personalized and involves a complex production process, manufacturing is a crucial component and a key concern for regulators. As it’s developed lovo-cel, Bluebird has refined how it makes the drug, changes that the company says will help it meet eventual patient demand once approval is secured.

But the FDA requires companies prove that new production processes can deliver the same result as earlier ones used in clinical testing, a hurdle Bluebird is now trying to clear.

“We believe that this complete data package supports comparability and addresses the questions asked,” said Obenshain.

Yet, for some analysts, the news adds to doubts about the treatment. Mani Foroohar, an analyst at SVB Securities, wrote in a note to clients that he lowered his estimated probability of success for lovo-cel, citing the FDA’s information request and filing delay.

Bluebird also has competition in seeking FDA approval for a sickle cell gene therapy. Vertex Pharmaceuticals and CRISPR Therapeutics are working to submit an application for their gene editing treatment, which they expect to complete by the end of this month.