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Sangamo BioSciences Initiates Gene Therapy Trials Toward A Cure For HIV

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Published: Jan 10, 2012 9:58 am
Sangamo BioSciences Initiates Gene Therapy Trials Toward A Cure For HIV

Sangamo BioSciences announced yesterday that it is initiating two Phase 2 clinical trials of its gene therapy treatments for people with HIV. The trials will test two different strategies for increasing the effectiveness of the therapy, with the goal of creating a cure for HIV.

“We are delighted to be able to open these two important clinical studies ahead of schedule,” said Geoff Nichol, executive vice president of research and development at Sangamo, in a press release.

Both trials are testing gene therapy approaches to curing HIV. In the field of HIV/AIDs, gene therapy involves modifying a person’s DNA (the genetic information in cells) so that it becomes, for example, resistant to HIV infection (see related AIDS Beacon news).

In both trials, cells will be taken from the patient’s body, genetically modified in the laboratory, and then injected back into the patient.

Altogether, Sangamo anticipates recruiting around 29 people with HIV for both clinical trials.

Gene therapy as a cure for HIV is a somewhat controversial approach. Some researchers believe the technique is too risky and expensive for widespread use. Others, however, think that gene therapy may be the only way to cure HIV, and that the science behind it is developing rapidly enough to make it a viable treatment option (see related AIDS Beacon news).

The gene therapy approach being tested by Sangamo is an attempt to mimic the success of “The Berlin Patient,” a man who received a bone marrow transplant from a carefully selected donor with a mutated form of the CCR5 gene.

HIV requires the CCR5 protein, which is located on the surface of white blood cells, in order to attach to and infect the cell. People naturally born with an alternate form of the CCR5 gene are almost entirely immune to HIV. Since his transplant, no sign of HIV has been detected in The Berlin Patient.

In the Sangamo trials, investigators will genetically modify immune cells, called T-cells, to remove CCR5. The researchers hope that the genetically modified T-cells will be immune to the virus and thus able to block viral entry and replication. They also hope the cells will multiply to make other HIV-resistant T-cells. The goal is to eventually attain a “functional cure” for HIV: a remission state with long-term control of HIV, including low viral loads (amount of HIV in the blood) in the absence of antiretroviral therapy.

Results from a Phase 1 trial showed that the technique successfully reduced viral loads in patients with HIV. One study participant, who already naturally had one copy of the HIV-resistant CCR5 gene form, achieved undetectable viral loads with the treatment.

“Both of these new Phase 2 clinical trials are specifically designed to confirm and further investigate these findings,” said Nichol.

In the Phase 2 trials, Sangamo will test two approaches to improve the efficacy of their technique.

In the first trial, the researchers will further explore the gene therapy’s effects on people who naturally have one copy of the HIV-resistant CCR5 gene. Up to 20 HIV-positive adults on antiretroviral therapy who have the alternate gene will be enrolled.

Study participants will receive one course of the gene therapy treatment. After two months, they will then stop antiretroviral therapy for 16 weeks while the researchers monitor their CD4 (white blood cell) counts and viral loads.

Participants whose CD4 counts drop below 350 or whose viral loads rise above 100,000 copies per milliliter will restart therapy, as will participants with detectable viral loads after 16 weeks. However, participants who retain undetectable viral loads will remain off therapy until their viral loads become detectable or their CD4 counts drop below 350.

In the second trial, researchers will test whether an initial preparative regimen of cyclophosphamide (Cytoxan) prior to the gene therapy treatment improves its efficacy.

Cyclophosphamide is used in cancer patients to improve the outcome of stem cell transplants by killing a patient’s existing T-cells. The goal of the trial is to determine if depleting these cells will allow the gene therapy-modified T-cells to better take hold and multiply.

The trial will enroll at least nine participants and will test three different dosages of cyclophosphamide a day prior to the gene therapy treatment. After the gene therapy treatment, study participants will then undergo a 16 week antiretroviral treatment interruption with the same guidelines as in the first trial, but with a more stringent CD4 count cutoff of 500 cells per microliter.

For more information, please see the Sangamo BioSciences press release.

Photo by victor_sween on Flickr – some rights reserved.
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  • bobby williams said:

    where can i find out about clinical trials in houston texas,