Bluebird Bio (BLUE -1.07%) is a small company with big ideas. The clinical stage biotechnology company is researching novel treatments that seek to insert missing genes into patient stem cells.

The science behind  Bluebird's approach is so compelling that Celgene (CELG) inked a deal early last year that could prove worth hundreds of millions of dollars to Bluebird if the two succeed in developing cancer treatments using Bluebird's technology.

More recently, Bluebird's shares soared again last month, after the company reported that it will present data from a study involving its gene therapy treatment for beta-thalassemia patients at the 19th Annual Congress of the European Hematology Association, to be held in Milan later this week. Since that presentation is likely to spark renewed interest in the company, let's take a closer look at Bluebird, its clinical pipeline, and research surrounding gene therapy.

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Innovative treatment for rare disease
Bluebird has two clinical product candidates. The first is Lenti-D, a treatment for childhood cerebral adrenoleukodystrophy, or CCALD, that is in phase 2-3 trials.

CCALD is an ultra-rare, hereditary neurological disorder that affects young boys. Over time, the myelin sheath surrounding brain cells breaks down and the patient's adrenal glands fail to work properly, eventually resulting in death.

Source: Bluebird Bio.

Currently, patients are treated with stem cell transplants, in which stem cells are introduced to the body that contain the missing gene associated with the disease. However, fewer than 30% of donors are ideal matches and patients often suffer from complications tied to infection, graft failure, or graft versus host disease when non-matching donors are used.

Lenti-D circumvents those non-matching donor risks by modifying patients' own stem cells to include a functioning version of the missing gene. So far, Lenti-D has succeeded in four patients, all of whom have seen disease progression halted.

Bluebird is also studying LentiGlobin as a treatment for beta-thalassemia and sickle cell disease, and LentiGlobin will be the subject of this weekend's presentation.

LentiGlobin works similarly to Lenti-D by inserting a fully functional human beta-globin gene into patient stem cells to prevent rejection. Bluebird treated its first patient with Lenti-D in 2010 and started a phase 1-2 study in the U.S. in March.

Gene therapies' appeal
It's a bold approach, but gene therapy has been gaining momentum following the approval of Dendreon's (NASDAQ: DNDN) immunotherapy drug Provenge in 2010. While Provenge differs from gene-modifying drugs like Bluebird's (and its commercial success or failure is an ongoing debate), the approval of the therapy, which involves removing patient blood cells, modifying them to contain CD54+ T cells, and returning them to the patient, has given hope to researchers that cell-based therapies are viable. Provenge, which costs $93,000 per patient, posted $325 million in sales during 2012 and $284 million in sales last year.

Provenge's approval was followed in 2012 with the approval of uniQure's Glybera in the European Union. Glybera also targets an ultra-rare disease, familial lipoprotein lipase, by replacing a missing enzyme. While Glybera has yet to produce material sales for uniQure, its approval reinforces that gene therapies can win over regulators.

Amgen (AMGN -0.50%) hopes that regulators' willingness to consider gene therapies may help it secure approval of its own gene therapy candidate, T-VEC, a treatment for metastatic melanoma.

Amgen reported in March 2013 that 16% of 400 patients treated with T-VEC responded to the therapy, far outpacing the 2% response rate for patients treated in the control group. Amgen acquired T-VEC in its $425 million purchase of Biovex, a company formerly run by uniQure's President of U.S. operations, and Amgen is currently compiling evidence in support of a potential FDA filing later this year.

Fool-worthy final thoughts
Celgene paid Bluebird Bio $75 million upfront and agreed to pay Bluebird up to $225 million in fees and milestones for therapies resulting from its collaboration on modified T-cell gene therapies for cancer. That's a big endorsement; however, gene therapy remains in its infancy, and the two companies have yet to move any drugs from their collaboration into human trials. That suggests that Bluebird, while intriguing, remains highly speculative and suited only for the most aggressive investors.