Alzheimer’s disease, a progressive neurodegenerative disorder that primarily affects memory and cognitive functions, is the most common cause of dementia, accounting for 60-70% of dementia cases.As per Alzheimer’s Association, in 2025, global Alzheimer’s statistics indicate a significant prevalence of the disease, with projections estimating that over 7 million Americans will be living with Alzheimer’s dementia. Globally, it is estimated that someone develops dementia every three seconds, and the number of people living with dementia is expected to reach 78 million by 2030.The progressive neurodegenerative disorder, long considered a therapeutic dead end, may soon find some hope of cure in an unlikely ally: cancer drugs.Recent research reveals that several oncology medications, originally designed to fight tumors, have shown promise in targeting key pathways of Alzheimer’s disease (AD), from protein aggregation to neuroinflammation and metabolic dysfunction.Let’s delve deeper into the newest discovery of the silver lining.
The medical breakthrough:
Scientists are exploring cancer drugs as a potential way to tackle Alzheimer’s disease, given that the options for treatment are quite limited. As cases of Alzheimer’s continue to rise in the US and around the world due to an aging population, there still isn’t a cure. Efforts to create new treatments that actually slow the disease’s progression have mostly fallen short.
Currently, only two drugs, Leqembi and Kisunla, are approved by the FDA to slow down early Alzheimer’s, but their effectiveness is very limited. Many pharmaceutical companies have even stopped developing Alzheimer’s drugs after unsuccessful trials, while others are experimenting with existing medications, including popular weight loss drugs.Researchers at the University of California, San Francisco, have taken a different approach. They searched through a database of over 1,300 various drugs, like antipsychotics and chemotherapy drugs, to find ones that could be repurposed for Alzheimer’s treatment. Their study, published in the journal Cell, highlighted two cancer drugs that showed promise in reducing Alzheimer’s risk. When tested together on mice, these drugs appeared to slow or even reverse Alzheimer’s symptoms.One drug is typically used for breast cancer, and the other works against colon and lung cancer. Alzheimer’s is known to cause significant changes in gene expression in the brain, which can disrupt brain function and lead to memory loss.From their database, fewer than 90 drugs successfully reversed markers related to Alzheimer’s in human brain cells. Of these, five drugs seemed particularly effective in lowering Alzheimer’s risk for actual patients, and the researchers focused on two FDA-approved cancer drugs to test in mice.According to the findings, letrozole, a breast cancer drug, appeared to influence gene expression in nerve cells, while irinotecan, used for colon and lung cancer, affected glial cells, which support the nervous system. Alzheimer’s can damage nerve cells and trigger an overgrowth of glial cells, leading to brain inflammation.Interestingly, past studies have shown that breast cancer patients on letrozole had a lower chance of developing Alzheimer’s, and colorectal cancer survivors treated with irinotecan also showed decreased risk, adding to the excitement around these findings.
The groundbreaking findings:
Researchers have been testing a combination of two cancer drugs in mice and found some promising results: the combo reversed brain degeneration and improved memory in mice showing signs of Alzheimer’s. However, because what works in mice doesn’t always work in humans, they plan to test these drugs in a clinical trial with Alzheimer’s patients.
Dr. Yadong Huang, a co-author of the study and a neurology professor at UCSF, noted the advantages of repurposing existing drugs: “Developing a new drug can take hundreds of millions, or even billions, of dollars, and on average takes more than 10 years. For this repurposed drug, usually, it just takes two or three years, and then you can go to the clinical trial, and the cost is much, much lower.” Despite this progress, he acknowledged, as reported by NBC News, “We still haven’t generated or produced any very effective drugs that can really slow down dramatically the cognitive decline.”Alzheimer’s remains a complex disease, and its exact cause is still a mystery. Currently, it isn’t clear why these cancer drugs might help with Alzheimer’s. One idea is that the breast cancer drug reduces estrogen production, which controls many genes. Another theory is that the colon and lung cancer drug might reduce inflammation in the brain by stopping glial cells from multiplying.Dr. Melanie McReynolds, a biochemistry assistant professor at Pennsylvania State University, who wasn’t involved in this study, added another angle. Her research suggests that another cancer drug can help Alzheimer’s by regulating glucose metabolism, which is how cells generate energy. “With aging, with stress, with diseases, that line of communication is disrupted,” she explained. She believes the drug combo could reverse metabolic decline, calling it “the secret for contributing to better outcomes with Alzheimer’s.”
What’s ahead:
Cancer drug repurposing opens a transformative chapter in Alzheimer’s treatment, where repurposing anticancer agents allows researchers to exploit existing toxicity and pharmacokinetic data, potentially accelerating human testing and reducing development costs.While these findings are exciting, the potential side effects need to be carefully considered. Letrozole can cause hot flashes, and irinotecan may lead to severe diarrhea. “These drugs have huge side effects, so you need to always balance and figure out whether those types of side effects would be amenable to somebody with Alzheimer’s,” Sirota cautioned. “It’s not that it’s a slam dunk.”