Bluebird posts more promising results for its rare disease therapy

Bluebird bio's experimental therapy for the genetic blood disorder beta-thalassemia major is working just as the biotech ($BLUE) planned, using a single dose to wean two more patients off of the chronic transfusions required to treat the disease.

The disorder results from a defective beta-globin gene that stops patients from producing the hemoglobin they need, often resulting in symptoms like severe anemia and an enlarged spleen. Bluebird's treatment, LentiGlobin BB305, uses a modified lentivirus to deliver a corrective copy of the gene through a one-time infusion, ideally getting beta-thalassemia major patients back to manufacturing beta-globin on their own.

And, so far, LentiGlobin BB305 is doing exactly that. In preliminary results presented at the annual the American Society of Hematology meeting, the first four patients treated with bluebird's therapy remain transfusion-free after at least three months follow up, affirming the treatment's promise as a functional cure for the disease. That adds two more transfusion-free patients to the two bluebird disclosed over the summer, news that sent its shares up more than 50% in June. Bluebird's latest update boosted its stock price as much as 60% after hours on Monday.

The new data come from two ongoing studies of LentiGlobin BB305. In the latest, bluebird has dosed 5 patients with beta-thalassemia major, finding that the first two are producing increasing amounts of beta-globin and have been transfusion-free for 5 and 3 months, respectively. The remaining three subjects need more time before bluebird can draw any conclusions on efficacy, the company said.

In the second study, involving two beta-thalassemia major patients and one with severe sickle cell disease, the two previously discussed subjects are still churning out beta-globin and remain free of the need for transfusions for 12 and 9 months, respectively. As for the sickle cell patient, bluebird said it's still too early to make efficacy inferences.

LentiGlobin BB305 has so far been well tolerated across both studies, the company said, with no gene therapy-related serious adverse events observed.

bluebird's David Davidson

Now bluebird, a 2012 Fierce 15 honoree, is working to complete enrollment in both studies next year, targeting 22 patients in total. As the data on LentiGlobin BB305 mature, the biotech plans to start working with experts, patient groups and authorities to map out a regulatory plan for the treatment, Chief Medical Officer Dr. David Davidson said.

LentiGlobin BB305 differs from many of the other gene therapies in development around the world, which involve inserting corrective genes directly into a patient. Instead, bluebird's method works by removing a patient's hematopoietic stem cells, equipping them with a functional beta-globin gene and then reinserting them through infusion.

About 40,000 children are born with beta-thalassemia around the world each year, according to bluebird.

- here's the release

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