Sangamo Shows Early Promise Against HIV, Hemophilia at Gene Therapy Revival Meeting
Word on the street in Seattle last week was that Big Pharma was sniffing around quite a bit at the American Society of Gene & Cell Therapy annual meeting being held downtown. There was a lot more optimism at this confab than in years past, and Richmond, CA-based Sangamo Biosciences was one of the companies capturing some of the buzz.
Sangamo (NASDAQ: SGMO) had 20 different presentations of data, mostly of the early/preliminary kind, at this meeting. Scientists were there to hear more about Sangamo’s proprietary “zinc-finger protein technology,” which is designed to edit specific DNA sequences inside a cell, to, say, turn off a disease activity. Many investors are waiting to see if Sangamo can deliver the goods on this concept later this year when results are due from a trial of an experimental drug of this variety in 170 patients with diabetic neuropathy—a big potential application of the technology. But most of Sangamo’s presentations at the gene therapy meeting in Seattle focused on using its technology in a number of other diseases, like HIV, hemophilia, and retinal neurodegeneration, to name a few.
Most gene therapy approaches, for those who don’t follow the field every day, involve modifying viruses to carry copies of genes into cells where they can replace missing or faulty genes at the root cause of certain diseases. Gene therapy was hyped in the early 1990s as a potential cure-all for all kinds of ailments that have evaded traditional drug-based approaches. Safety concerns have popped up more than once, and there still aren’t any FDA approved gene therapies, although there have been some encouraging results lately that have sparked a bit of a comeback.
“I’ve been coming to this meeting since 1990,” Sangamo CEO Edward Lanphier said during a break at a downtown hotel on Friday. “It goes up and down in terms of what’s hot and what’s not.”
Here’s a couple key programs that Sangamo highlighted at the conference, and which I discussed with Lanphier.
—Sangamo scientist Michael Holmes presented data from a study in mice which showed encouraging results in a specific type of hemophilia. In this case, the disease comes from a deficiency of a protein known as Factor IX. Scientists gave a single injection of one of Sangamo’s zinc-finger compounds and found that mice who got the injection were able to produce Factor IX on their own in high enough levels to achieve normal blood clotting, Lanphier says.
“The efficiency is impressive and resulted in sustained therapeutic levels of Factor IX in the mice,” says Barrie Carter, the president of the ASGCT, and a member of Sangamo’s scientific advisory board.
Mice aren’t the same as human beings, so this program obviously has a long way to go. But if Sangamo can efficiently deliver its zinc-finger drug into human cells, it could have a big impact. A treatment like this may enable patients to quit taking regular injections of Factor IX protein replacement therapy, enabling them to save those drugs for emergency use. “Those data were very well received, absolutely remarkable,” Lanphier says.
—One other Sangamo programs that caught attention at the conference was a treatment for HIV. This drug, SB-728, is designed to make it so T-cells of the immune system no longer produce a protein on their surface, called CCR5, which serves as a gateway for the HIV virus to infect and damage the immune system.
Data from nine patients in a Phase I clinical trial presented at the conference showed that the treatment appeared safe. More complete data on the first 18 patients in the trial is expected by the end of 2011, Lanphier says.
What’s interesting about this approach is that it works differently than the other one against hemophilia, which is directly injected into the body. In the case of HIV, blood is withdrawn from a patient, T-cells get filtered out in a common lab process, and those filtered cells get treated with Sangamo’s zinc-finger protein drug. The cells then get re-infused into the patient, where they resist HIV infection, and retain their ability to fight off the virus, Lanphier says. Data from this trial suggest that patients who got the re-infusion had an overall stronger immune defense than they did before, he says.
Pfizer already has an HIV drug on the market to block the CCR5 receptor, called maraviroc (Selzentry). But as Lanphier notes, the average T-cell has 1,000 to 2,000 of these receptors on the surface, and a healthy individual may have 100 billion T cells, so it’s thought to be pretty hard to get enough drug into the system to protect every cell. That’s one reason why researchers are hopeful about creating a process to treat those T-cells in an efficient process outside the body, and re-infuse them back into the patient, Lanphier says.