Scientists at the University of Colorado Anschutz have found that a drug long approved for other conditions may be repurposed to slow the neuronal loss associated with Alzheimer’s disease (AD) and cognitive decline.

The study, published in Cell Reports Medicine, shows that the drug—a synthetic version of the naturally occurring human protein GM-CSF—improved one measure of cognitive function and reduced blood markers of neuronal death in people with AD during an initial clinical trial.

The drug, known as sargramostim (also marketed as Leukine), has been used for more than 30 years to treat various conditions, including certain cancers. In the new study, it was administered to patients with Alzheimer’s disease. Blood analyses revealed a significant reduction in levels of the protein UCH-L1—a marker of neuronal death—bringing them down to levels typically seen in younger individuals. In addition, participants receiving the drug showed improvements on one cognitive test compared with those given a placebo.

The researchers also observed that, with age, blood levels of protein markers linked to neuronal damage and inflammation—such as UCH-L1—increase exponentially, particularly in women, although the reasons for these differences remain unclear. Elevated levels of the inflammatory protein GFAP were detected as early as age 40, pointing to a possible link between age-related neuroinflammation and accelerated cognitive decline.

GM-CSF, the protein on which sargramostim is based, stimulates the immune system by promoting the production of new immune cells in the bone marrow and brain, while also modulating inflammation. In animal models, this protein has shown the ability to reverse cognitive impairment and reduce the rate of neuronal loss within just a few weeks of treatment.

The scientists caution that while the early trial results are promising, they are still preliminary. After the treatment course ended, markers of neuronal death began to rise again, although improvements on cognitive tests persisted.