Transplant drug raised brain blood flow in people with an Alzheimer's gene

A drug best known for stopping the body from rejecting transplanted organs raised blood flow in the brains of healthy middle-aged people who carry the main genetic risk factor for Alzheimer’s disease, according to a small study from the University of Missouri.¹ After four weeks of a daily low dose of rapamycin, only carriers of the gene variant, called APOE4, showed a rise in brain blood flow, and women carriers showed the biggest gains.² The study was a pilot with a single treatment group and no placebo, and it did not test whether the drug protects memory or prevents dementia.¹

What happened

The study was led by Ai-Ling Lin, a professor in the University of Missouri School of Medicine and College of Arts and Science, and an investigator at the university’s Roy Blunt NextGen Precision Health building.¹ It was published in the Journal of Cerebral Blood Flow & Metabolism under the title “Rapamycin increases cerebral blood flow and modulates metabolic, inflammatory, and microbiome profiles in healthy middle-aged APOE4 carriers: a pilot single-arm trial.”¹ The university announced the results on September 30, 2026.¹

The volunteers were adults aged 45 to 65 who had been screened for the APOE4 gene.² None had memory problems or signs of dementia.² People with and without the gene variant took a low dose of rapamycin every day for four weeks.¹ Brain scans then showed that blood flow rose significantly only in the APOE4 carriers; people without the variant who took the same drug did not show a comparable change.²

“Alzheimer’s tends to happen more in older people, especially for those with APOE4. If we can slow down aging in the brain for those people most at risk, maybe we can reduce the risk of them developing Alzheimer’s disease.”

That is how Lin described the aim of the work.¹

Why researchers look at brain blood flow

APOE4 is the strongest known genetic risk factor for late-onset Alzheimer’s, the common form that appears later in life.² Neuroscience News reported that carrying one copy triples lifetime risk and carrying two copies can raise it twelvefold.² An earlier summary of the research gave a range of a 2- to 3-fold higher chance for one copy, and the same 12-fold figure for two copies.³

People with APOE4 often have reduced blood flow to certain parts of the brain years before memory problems appear, which makes low brain blood flow a possible early warning sign of Alzheimer’s risk.¹ Nerve cells depend on a steady supply of blood for oxygen and for clearing waste.² The idea behind the study is that if this early shortfall can be changed, it might be one way to intervene long before symptoms start.²

Rapamycin is an FDA-approved drug used to prevent organ transplant rejection and to treat rare lung conditions.² It works by blocking a cell-signaling pathway called mTOR, which is involved in cell growth and has been studied widely in aging research.² Before moving to Missouri, Lin’s lab reported that the drug slowed brain aging and improved brain blood flow in mice engineered to carry APOE4.¹

The finding in women

The researchers reported that women with APOE4 had the largest increase in brain blood flow.¹

“We also found that females with APOE4 saw the greatest improvement in brain blood flow, which is significant given that nearly two-thirds of people with Alzheimer’s are women.”

Lin said this, adding that the work was “an example of precision medicine, as we work to identify who can benefit from this drug the most.”¹ Neuroscience News noted that women carrying APOE4 tend to show faster mental decline than men with the same gene.²

The study also looked at changes in the body beyond the brain. According to the paper’s title, rapamycin “modulates metabolic, inflammatory, and microbiome profiles,” meaning researchers saw shifts in blood markers of metabolism and inflammation and in gut bacteria.¹ The sources read for this article do not give the details of those changes.

What it does not show yet

Several limits matter when reading this result:

• No placebo group. The paper describes itself as a “pilot single-arm trial,” meaning everyone got the drug and no one got a dummy pill for comparison.¹ The comparison was between people with and without the gene, both on rapamycin.²
• Small and short. It was a pilot study lasting four weeks.² IQgenio, which summarized the work, called it “small and preliminary.”⁴ The sources read for this article do not give the number of participants.
• A scan measure, not a health outcome. The study measured blood flow in the brain. It did not show that memory improved or that anyone’s chance of developing Alzheimer’s went down. The university’s statement says the result “suggest[s]” the drug could help preserve thinking skills; that remains a hope to be tested.¹
• Not approved for this use. Rapamycin is not approved for Alzheimer’s prevention, and IQgenio noted that its long-term safety in healthy adults is still being studied.⁴

Some write-ups went further than the data. Neuroscience News wrote that the drug “acts directly upon” the blood vessel weakness caused by the variant, and that the findings show vascular problems “can be therapeutically modified decades before” symptoms.² A short, uncontrolled pilot measuring blood flow does not by itself establish either point.

Who is behind it

The work comes from Lin’s group at the University of Missouri, based at the Roy Blunt NextGen Precision Health building, which the university says brings researchers and clinicians together to move lab findings into human trials.¹ The university’s news office, which published the main announcement, describes the study as offering “new hope” and as part of Mizzou’s Alzheimer’s research leadership.¹ The sources read for this article do not say who funded the study or whether any researchers have commercial ties to rapamycin.

How it fits the field

This is not the Missouri group’s first human report. In early 2025, a paper in Alzheimer’s & Dementia by Flemister and colleagues, also from the University of Missouri, described giving rapamycin for four weeks to three cognitively normal middle-aged people with two copies of APOE4 and two people with the more common APOE3 version.³ In that very small group, brain blood flow and the size of two memory-related brain areas, the hippocampus and caudate, increased in the APOE4 carriers but not in the APOE3 carriers.³ The sources do not say whether those five people were also part of the new study.

Rapamycin has drawn interest in aging research largely because of animal results: one review cited by NAD.com reported that it extended mouse lifespan by 26% and eased aging in several organ systems in animals.³ Those are animal findings, and the Missouri studies are among the first tests of the drug’s effects on the aging brain in people.³

What to watch next

Lin and her colleagues say they plan larger and longer trials.² The goal is to find out whether keeping brain blood flow up over time with drugs like rapamycin can delay or prevent Alzheimer’s in people at high genetic risk.² Key questions for those studies include whether the effect holds up against a placebo, whether it lasts beyond four weeks, whether the stronger response in women is confirmed in a larger group, and whether changes in blood flow lead to any difference in memory or dementia rates years later.

For a related approach, Biohack recently covered a trial testing an Alzheimer’s drug in healthy people to see if it can prevent the disease.