"Our study shows that we may, may, in some way help patients with their memory, perhaps because we're keeping the microglia from overactivity," said study leader Dr. Joel Ross, president of the Memory Enhancement Centers of America in Eatontown, N.J.
Experts who were not involved in the research saw reasons for caution with the results.
"With  patients, you can't jump up and down about some symptoms improving in some patients," said Greg Cole, associate director of the Alzheimer's Center at the University of California, Los Angeles. "It's also not clear what the nature of the microglia modulation is exactly."
Study authors admit they don't know exactly how the drug works, either. But they said they're already planning larger studies to try to confirm their finding.
The second drug being presented at the meeting, a BACE inhibitor that's being developed by Merck, has the opposite problem. Researchers know exactly how it does what it does. They don't yet know whether it will help patients.
BACE inhibitors block an enzyme that cleaves a large protein in the brain into smaller pieces of sticky beta amyloid, a substance that forms telltale plaques in the brains of Alzheimer's patients. Blocking the enzyme blocks production of beta amyloid.
"It's been an important target. It took the drug companies at least a decade to develop this class of drugs," Rosenberg said. "Drug companies did a lot of black magic to get this drug into the brain. It's really compelling that this drug really does what it says it does."
In this study, which was mainly designed to check the safety of the drug, researchers assigned 30 patients to take one of three drug dosages or a placebo for seven days. Patients on the highest doses of the drug saw reductions in beta amyloid in their spinal fluid of over 80 percent. Researchers say they saw no evidence of adverse effects.
"We can reduce amyloid to unprecedented levels," said Dr. Mark Forman, a senior principal scientist at Merck, the company that's developing the drug.
The problem, skeptics say, is that medications have been used to reduce beta amyloid before, and those had no clinically meaningful benefits for patients, at least for those already diagnosed with the disease. There have been some signs that lowering beta amyloid may be helpful for people who haven't yet begun to show symptoms of memory loss.
Forman said he thinks BACE inhibitors have a better chance of working, however.
"BACE inhibitors blocks the generation of amyloid at the very first step in its production. It's very different from what some of the other studies have done with antibodies that are really promoting the clearance of beta amyloid after it's formed," he said.
Experts agreed that the drug seems to work well to lower beta amyloid.
But, "It remains to be seen when you can do that and for how long and achieve a useful, clinical benefit," Cole said. "That's what we don't know and it will be a long time before we can figure that out."
Research presented at medical meetings should be viewed as preliminary until published in a peer-reviewed journal.
To learn about medications available to treat Alzheimer's symptoms, head to the Alzheimer's Association.
Copyright © 2012 HealthDay. All rights reserved.