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Gene Therapy for Sickle Cell Disease Shows Promise in Early Trial

Company provides ‘sneak peek’ at meeting abstract

Bluebird Bio, Inc. has announced that promising data from an ongoing phase I/II study of LentiGlobin BB305 will be presented in June at the 20th Congress of the European Hematology Association in Vienna, Austria.

The company also offered a “sneak peek” at the presentation abstract, noting that two patients with beta-thalassemia major have remained transfusion independent at 14 and 11 months post-transplant. In addition, a patient with sickle cell disease (SCD) has shown increased production of hemoglobin (Hb) AT87Q, which has anti-sickling properties, and has not required post-treatment hospitalization for a sickle cell disease-related event.

LentiGlobin BB305 extracts blood stem cells and infuses them with a working version of the malfunctioning gene that had caused the SCD. People with this disorder must undergo monthly blood transfusions to survive — but if the investigational gene therapy continues to be successful, they may be freed from that burden, Bluebird Bio says. Between 1,000 and 3,000 babies are born with SCD in the U.S. each year.

The subject with SCD entered the trial receiving chronic transfusions and began the process of being weaned from these transfusions after day 37, receiving the last transfusion on day 88. This was the first person with SCD to be treated with gene therapy. The subject had an HbAT87Q level of 24% after 4.5 months of follow-up compared with an HbAT87Q level of 9.6% at 3 months post-transplant. The subject did not engraft until after month 1, so his or her level of HbAT87Q production at months 3 and 4.5 are actually months 2 and 3.5 after engraftment.

At 4.5 months of follow-up, the total anti-sickling hemoglobin (HbAT87Q + HbF) level was 31.6%.

The subject with SCD has not had any hospitalizations for disease-related complications post-transplant. Moreover, none of the subjects has experienced a drug product-related adverse event.

Based on historical clinical observations in patients with SCD, Bluebird Bio believes that individuals who achieve an anti-sickling hemoglobin (HbAT87Q + HbF) level of 30% or greater have the potential to reduce or eliminate the life-threatening events associated with SCD.

In February 2015, the FDA granted LentiGlobin BB305 a “breakthrough therapy” designation, which is used to expedite the development and review of a potential drug candidate that is expected to be used to treat a serious or life-threatening disease.

Sources: Bluebird Bio; May 21, 2015; and BioSpace; May 21, 2015.

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