Inside the First FDA-Cleared Stem Cell Trial for Alzheimer’s

Alzheimer’s treatments are notoriously difficult to develop. One major reason: the blood-brain barrier, a natural defense system that keeps harmful substances out of the brain but also blocks many promising drugs from reaching their target.

Stem cells have long intrigued scientists for their potential to regenerate or protect brain cells. These “master cells” can mature into many specialized types, raising the possibility that they could one day repair damaged tissue — including in the brain.

Now, an FDA-cleared stem cell trial for Alzheimer’s disease has advanced to Phase 2. The study is led by veteran neurosurgeon Dr. Christopher Duma, medical director of Hoag Memorial Presbyterian Hospital’s Brain Tumor Program in Newport Beach, California, and president and founder of Regeneration Biomedical Inc.

Stem cell research is often described as both promising and perilous. While credible, carefully monitored trials are underway, many unregulated clinics also sell expensive, unproven stem cell procedures marketed to patients with Alzheimer’s and other serious illnesses.

“There’s a lot of snake oil sales that are going on out there with stem cells,” Duma told Being Patient. But if done right, Duma believes stem cells are an opportunity to push the boundaries of neurodegenerative treatment after decades of limited progress in the field. To separate his work from shady efforts, Duma sought FDA oversight for his trial.

Other stem cell efforts for Alzheimer’s and Parkinson’s

Duma’s study isn’t the only one exploring stem cells for neurodegenerative diseases. Other teams are testing different types of cells and delivery methods in early animal and human studies, with mixed results so far.

One company, Skin2Neuron, has developed neuronal stem cells by reprogramming cells taken from hair follicles. In a small study of dogs with dementia, injecting these cells into the brain improved symptoms in some animals. The company is now exploring trials in people with neurodegenerative diseases.

Another company, Longeveron, has developed Lomecel-B, an intravenous infusion of mesenchymal stem cells, taken from the bone marrow of healthy young adults, intended to reduce inflammation and support brain repair. In a Phase 2 study of 49 participants, the company reported that the therapy was safe and hinted at cognitive gains.

Longeveron previously settled a 2021 investor lawsuit over allegedly misleading statements about earlier trials testing Lomecel-B to treat age-related frailty. The company completed an early Phase 2 trial for Alzheimer’s in 2023 but has not released full results or announced a follow-up study. 

The treatment isn’t FDA-approved, and no Phase 3 trial has been registered. It continues to be offered at cost at stem cell clinics in the Bahamas, where paying participants are enrolled in a registry.

“It is unethical to charge patients who enroll in a trial for an unproven therapy,” said Dr. Arnold Kriegstein, a UCSF neurologist and stem cell expert. “It also creates bias that can influence the outcome.”

Researchers are also studying stem cell–based therapies for Parkinson’s disease. Earlier attempts involved transplanting fetal brain cells, but those cells often failed to become the dopamine-producing neurons the disease destroys.

“In Parkinson’s disease, there’s a very specific nerve cell type, a dopamine-producing nerve cell that is selectively vulnerable and dies early on,” Kriegstein explained. “The idea of cell replacement therapy is to make those dopamine neurons out of pluripotent stem cells and then graft them into the patient’s brain.” 

Two trials published in April 2025 reported encouraging early results: the procedures appeared generally safe, though some participants experienced side effects from the required immunosuppressants. Because these studies were small and not designed to test efficacy, researchers say much larger trials are needed.

Meanwhile, BlueRock Therapeutics plans a 100-person, Phase 3 trial later this year to test whether the treatment delivers lasting cognitive and functional benefits — and whether transplanted cells survive long-term.

A new approach: Stem cells straight into the brain

Duma’s trial at Regeneration Biomedical takes a different approach from most stem cell studies. Instead of injecting stem cells intravenously, he and his team administer them directly into the brain’s ventricles, fluid-filled cavities that circulate cerebrospinal fluid.

This is the first trial to deliver autologous, fat-derived mesenchymal stem cells — cells taken from a patient’s own fat tissue — into the ventricles to treat a neurodegenerative disease.

The goal, Duma said, is to overcome one of neuroscience’s biggest challenges: getting treatments into the brain and keeping them there long enough to work. “We’re trying to thwart that little barrier and break through it by directly injecting the cells into the cavities of the brain,” he said.

Phase 1 of the trial, which focused on safety, enrolled people with mild to moderate Alzheimer’s (stages four and five of the disease’s seven stages).

“Since [they are] the first people to ever get this type of treatment, we want to make sure that it’s safe,” he said. “For Phase 1, it’s just a single injection, just to see if the patients do well. Not one of our patients even got a headache from the injection. They all did beautifully in terms of safety.”

He added that tau and beta-amyloid levels decreased in most patients, and cognitive scores improved following the injection. The team used the Mini-Mental State Examination (MMSE) and the Alzheimer’s Disease Assessment Scale–Cognitive Subscale (ADAS-Cog) — “the gold standard of cognitive testing” — to measure cognition.

“If they improve by even the smallest amount, that’s a first in this field of medicine,” Duma said. “So we were very excited that the majority of our patients improved.” 

Duma’s team reported that some participants’ scores dropped from the 70s into the 30s on the cognitive scale — a range in which higher numbers indicate more severe impairment. Duma emphasized that these findings are preliminary and come from a small safety study. They will need to be confirmed in a much larger group before any conclusions can be drawn.

Phase 2, which was cleared by the FDA in September, will expand the trial to 115 participants at multiple sites across the U.S. It will determine whether the therapy’s apparent effects are statistically significant.

Duma discusses the trial and research so far, here:

Looking ahead

No stem cell therapy has yet been approved for Alzheimer’s or any other neurodegenerative disease, but Duma is optimistic that this could change.

“There’s no 100 percent in my field, but I am 95 percent confident that we will be using stem cells specifically for these neurodegenerative diseases,” he said. “The sky’s the limit when it comes to stem cells.”