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Sangamo Gene Therapy Shown to Be Safe in First Study in HIV

Sangamo Biosciences Inc.’s experimental gene therapy was used safely in six patients infected with HIV in the first trial of a new approach aimed at blocking the virus so patients won’t need antiviral drugs.

After a year, five of the six had “significant and largely sustained” increases in the number of infection-fighting t-cells in their system, said study leader Jacob Lalezari, director of Quest Clinical Research, a San Francisco clinical trial center. The patients kept taking drugs to suppress the virus during the study because the research first must assess whether the therapy is safe.

The treatment modifies patients’ t-cells to disable a protein called CCR5 that HIV uses to enter the cells. Without the entry point, HIV might not be able to kill off the immune system cells and they will outlast or eventually overpower the virus, Lalezari said. If the therapy cuts HIV levels in patients who aren’t taking antiviral drugs, it may gain approval by late 2013, said Liana Moussatos of Wedbush Securities in San Francisco.

“When that data comes at the end of this year, we should have an idea whether the efficacy is durable enough and potent enough,” Moussatos, a biotechnology analyst, said in a Feb. 25 telephone interview. If approved, the drug may have sales of $750 million a year, she said.

Shares Rise

Sangamo fell 23 cents, or 2.7 percent, to $8.27 at 4 p.m. in Nasdaq Stock Market composite trading. The Richmond, California-based company has gained 65 percent in the past 12 months.

Findings from the company-funded trial were presented today in Boston at the Conference on Retroviruses and Opportunistic Infections, a meeting of infectious disease doctors.

“This isn’t for mass production or fully ready for prime time,” said Scott Hammer, a professor of medicine at Columbia University in New York, in an interview yesterday. “This is early work that takes molecular biology into the clinic. Like everything else in science and HIV, it’s an early and important finding, but we shouldn’t be raising the flag to say we’ve solved the problem yet.”

All six patients, before the trial began, had low levels of the key immune system cells that orchestrate the fight against HIV. Previous therapy had made the virus undetectable in the patients. Researchers were able to modify an average of 26 percent of the t-cells in the laboratory before returning them to the patients.

Cells Take Hold

The modified cells took hold and accounted for 1 percent to 6 percent of the peripheral blood in five patients two weeks after treatment. The genetically-engineered cells lasted throughout the study. The number of immune system cells overall also increased in all five patients, the study found.

One patient had a muted response because his body fought off the virus used to deliver the therapy, Lalezari said in an interview.

More information is needed about how the immune system and the virus react to treatment before it will be clear if the approach works, Lalezari said. If it doesn’t reduce the amount of HIV in people with high levels of the virus, it may have little real impact on the disease, he said.

“These results are about as good as you could hope for,” he said. “Unequivocally, the safety looks good. But it could all amount to nothing unless we move viral load. Then it’s just an interesting experiment.”

Sangamo is presenting another study on Wednesday that tracked patients who stopped taking their HIV drugs after getting the gene-therapy to better understand how it works.

Curing AIDS

The therapy tries to replicate the successful treatment of an American, Timothy Brown, who in 2007 received a stem-cell transplant aimed at curing his leukemia and his HIV. The transplant donor was among the 1 to 2 percent of people with mutations that inactivate both copies of their CCR5 gene.

The transplant worked and Brown stopped taking antiviral medication. Four years later, he has no detectable virus in his system, according to his doctor, Gero Hutter, now with the German Red Cross in Mannheim, Germany.

In Sangamo’s process, doctors draw patients’ blood and remove the infection-fighting white blood cells called t-cells. They are sent to Sangamo and modified using naturally occurring proteins called zinc fingers that cut into patients’ DNA in the middle of the CCR5 gene. The modified cells are then returned to the patient through an infusion.

Reservoir of Cells

While the therapy won’t eliminate the CCR5 protein from all of a patient’s t-cells, it may create a reservoir of cells that are resistant to HIV, helping suppress the virus, Lalezari said.

The Sangamo therapy is “a way to delay or replace antiviral therapy” with one or more treatments, Lalezari said. “To my mind, the importance of this is the extent to which it contributes to a cure.”

There are 1.1 million Americans living with the Human Immunodeficiency Virus that causes AIDS, and 34 million are infected worldwide, according to the U.S. Centers for Disease Control and Prevention.

Antiviral drugs, led by Atripla and Truvada, made by Gilead Sciences Inc., of Foster City, California, and Reyataz, sold by New York-based Bristol-Myers Squibb Co., generated $15.1 billion in worldwide sales last year, according to IMS Health Inc., a Norwalk, Connecticut-based industry research company.

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