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FDA approves expanded testing for HIV 'cure' |
by Mike Andrew -
SGN Staff Writer
The federal Food and Drug Administration (FDA) has approved expanded testing for what has been called an 'effective cure' for HIV.
The method uses genetic modification to create a specific mutation in the patient's T-cells which replicates naturally-occurring mutations in the rare people known to be immune to HIV infection.
Stem cells are taken from HIV-positive patients and their gene sequence is altered to modify the CCR5 protein found on the surface of T-cells.
HIV initially uses CCR5 receptors to enter and infect new cells. Individuals who are naturally resistant to HIV - known as 'elite controllers' - have a mutation of CCR5, which rejects HIV and thus protects them against infection.
This mutation occurs naturally in a small percentage of the world's population and gives these individuals a life-long resistance to HIV infections. Although the virus may enter and remain in their bodies, without being able to enter the T-cells it cannot replicate and therefore will stay at low numbers, without harming the individual's immune system.
In theory, genetically edited stem cells can be introduced into HIV patients, duplicating natural immunity. The modified cells will then repopulate the body with cells possessing the same mutation. This would give patients the same lifetime resistance to HIV as those with natural immunity have, and with only one medical procedure.
The method was developed by Sangamo BioSciences Inc., but has also been tested in early human clinical trials by drug research company Calimmune.
Initial clinical trials found that a number of patients controlled the virus for up to four years. An increase in T-cells was also noted, which was unexpected due to the cessation of HIV drugs.
Because initial human tests were done on a very small sample of 12 subjects, once it was established that the method was safe and showed promise, the FDA approved expanded testing on 70 additional subjects.
Besides expanding the current trial, the FDA also approved two more US-based trials.
One is a more aggressive method to disable CCR5 so that HIV cannot latch onto new cells, and the other uses the original strategy but is aimed at people who have failed current HIV drug regimens.
Although the antiretroviral drugs that are now standard HIV therapies do control the virus, they can have side effects and a number people are resistant to certain drugs.
Antiretrovirals work by stopping the replication of HIV in the body and achieving an 'undetectable' viral load by using powerful and toxic drugs. The new genome editing method aims to stop the HIV from infecting new cells without drugs.
Research into genome therapy took off after the 'Berlin Patient,' Timothy Ray Brown, was effectively 'cured' of HIV after a stem cell transplant from a donor with natural HIV fighting genes.
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