Shares of Sangamo Biosciences (NASDAQ:SGMO) are up more than 20% today on the news that HIV patients who were given Bristol-Myers Squibb's (NYSE:BMY) drug Cytoxan responded better to Sangamo's drug SB-728-T, which is made up of the patient's own genetically modified cells.

However, in this video, Motley Fool health-care analyst David Williamson points to a few things that investors need to keep in mind that should temper some of the enthusiasm. Firstly, the success story here was only two patients, and secondly, with Sangamo's drug, the virus is stabilized, but still detectable. Comparing this against current anti-viral drugs, which bring the virus down to undetectable levels, means Sangamo will still need to do better if it wants patients to switch. David takes a close look at the company in this video, discusses its financial situation, and points to some key trials coming up that will give investors a much better idea whether they should be jumping in on this stock.

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