Reporting at the Alzheimer’s Association International Conference in Washington, D.C., researchers showed some glimmers of hope in the potential benefit of two agents being tested in patients with mild to moderate Alzheimer’s disease. Currently, there are no treatments that address the root causes of the neurodegenerative condition, which include the build up of amyloid plaques in the brain and the formation of tau tangles once nerve cells start to die off.
One drug, from Eli Lilly, aims to soak up amyloid and thus prevent it from accumulating in the damaging plaques that suffocate neurons in the brain. But to test its effectiveness in a timely manner, the scientists adopted an unorthodox trial design — they divided participants with mild to moderate disease into two groups, one that took the drug, which is given via IV, and another that took placebo. After 18 months, there were no significant differences between the groups on cognitive tests, although people with mild disease seemed to show signs of improvement. So those on placebo were then switched to the study drug, called solanezumab, and followed for another 18 months to two years. The idea was that by the end of the study, the participants who had been taking the drug all along should show greater improvements in cognitive skills than those who switched midway through.
That’s what the researchers saw. In their report, they said that the two groups showed differences in their thinking abilities. But whether that gap can be attributed to the drug alone isn’t entirely clear—at least not yet. And whether that difference is enough to fuel further study, especially in people at the earliest stages of the disease, or form the basis of an approval by the Food and Drug Administration is even more uncertain.
The other experimental agent, aducanumab, also sops up amyloid, but was associated with brain swelling in earlier studies at higher doses. Scientists at Biogen, which is developing the compound, added an intermediate dose to get a better sense of how much of the drug could produce the most benefit without triggering side effects. The results were from an earlier stage of testing, and focused primarily on safety of these doses so developers could not say for certain whether the improvements they began to see in slowing cognitive decline were significant. But they were enough to warrant more study.
Both trials show that, while promising, the first-ever treatments for Alzheimer’s have a ways to go still on this long, and often precarious road.