By Robb M. Stewart

Bluebird bio Inc.'s shares were sharply lower early Monday after the Food and Drug Administration placed a partial hold on the company's clinical program for lovotibeglogene autotemcel gene therapy for sickle cell disease.

The partial, temporary suspension for patients under the age of 18 relates to an investigation by bluebird bio into an adolescent patient with persistent, non-transfusion-dependent anemia following treatment with lovo-cel, now 18 months post-treatment, the company said.

In premarket trading, the shares were 20% lower after closing last week at $10.62, down more than 60% since the end of last year.

Bluebird said the adolescent patient is clinically well and there is no evidence of malignancy or clonal predominance.

Enrollment and dosing for patients 18 and older living with sickle cell disease in its HGB-206, HGB-210 and LTF-307 clinical studies, as well as follow up for treated patients of all ages in all studies, are continuing as planned, the company said.

"We have paused enrollment and treatment of patients younger than 18 in our SCD clinical program, and we will continue to work collaboratively with the FDA to understand and address their concerns," Chief Medical Officer Richard Colvin said.

The company said it expects written questions from the FDA in early 2022 and will work quickly to respond in order to resolve the partial hold. It said it is evaluating what impact, if any, the partial clinical hold may have on its first quarter 2023 projected timing for the lovo-cel biologics license application submission.

Write to Robb M. Stewart at robb.stewart@wsj.com

(END) Dow Jones Newswires

12-20-21 0908ET