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Cambridge firm hopeful, cautious on gene therapy

By Carolyn Y. Johnson
Globe Staff / September 16, 2010

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A Cambridge biotechnology company has developed a gene therapy that successfully treated a 21-year-old French man who suffers from an inherited blood disorder called beta thalassemia, allowing him to forgo monthly transfusions that he has depended on since childhood.

The case, reported yesterday in the journal Nature, is the latest example of progress in the field of gene therapy. Bluebird Bio, the company developing the therapy, plans to recruit nine additional patients for its clinical trial, which will include patients with beta thalassemia and sickle cell anemia.

“Now, the patient has been without any transfusions for two years. . . . I must say we want to be cautious — nevertheless, at this point it’s good to see the patient lives a normal life for the first time, has a full-time job in a restaurant in Paris as a cook,’’ said Dr. Philippe Leboulch, a visiting professor at Harvard Medical School and a professor of medicine at the University of Paris, who is the senior author of the study.

Leboulch, who is a member of Bluebird’s scientific advisory board, said he began the work that led to the new therapy 20 years ago. In June 2007, researchers removed the patient’s bone marrow and used a virus to insert corrected copies of the defective gene in marrow cells. They gave the patient chemotherapy to eliminate his blood cell precursors that carried the genetic defect, before returning the modified cells to the patient.

Leboulch said that the results were promising, but emphasized that scientists were proceeding with caution and carefully monitoring the patient for side effects.

He noted that they are monitoring cells in the patient that overproduce a protein that has been found to contribute to tumors, but the patient is healthy.

Outside researchers said that this was an exciting success.

“This is a very significant study. Beta thalassemia is really challenging for gene therapy,’’ said Guangping Gao, the director of the gene therapy center at the University of Massachusetts Medical School, who was not involved in the study. “One patient is a very small study, but this is really a milestone.’’

Bluebird Bio was until very recently known as Genetix Pharmaceuticals, and for the company the trial is part of a larger thrust into gene therapy. The company recently received $35 million in venture capital funding.

Beta thalassemia is a genetic disease that causes anemia, and patients need monthly blood transfusions over their lifetime. Those transfusions cause iron to build up in the body, potentially damaging organs and requiring further treatment.

The disease is more common out side the United States, and 60,000 children worldwide are diagnosed with it each year.

“This is a huge public health problem outside the US,’’ said Nick Leschly, the chief executive of Bluebird.

The company also has a program in gene therapy treatments for adrenoleukodystrophy, a brain-wasting disease. Researchers published a paper in the journal Science last year showing positive results in two patients with that illness.

In an accompanying opinion piece published in Nature, Derek A. Parsons of the St. Jude Children’s Research Hospital in Memphis noted that a decade ago, gene therapy research paused. Viruses that were used to deliver the genes caused leukemia in some patients.

Most prominently, Jesse Gelsinger, an 18-year-old with a genetic liver disease, died after being treated with gene therapy in 1999, when viruses triggered a massive immune response.

But recently, gene therapy has had a string of successes, including against a rare disease that causes blindness, called Leber’s congenital amaurosis. Researchers have also reported good results with “bubble boy disease,’’ a lack of natural immunity that leaves children vulnerable to infections.

“I think the work started too fast in the field, because the name coined — gene therapy — was appealing to many. People wanted to have cures tomorrow,’’ Leboulch said. “But it took a little bit of time to try the waters.’’

Carolyn Y. Johnson can be reached at cjohnson@globe.com.