Vitamin K is known to most people as a blood clotting vitamin, barely anyone as a nerve growth factor. A research team at Shibaura Institute of Technology in Tokyo deliberately modified vitamin K's molecular structure by replacing its natural side chain with a retinoic acid chain. The result: the new compound converts three times more neural stem cells into neurons than natural vitamin K and crosses the blood-brain barrier, a feat that previous drugs against Alzheimer's and Parkinson's rarely achieved.
Vitamin K Beyond Blood Clotting
Vitamin K is primarily known as a clotting vitamin. Since the early 2000s, studies have shown it also performs neuroprotective functions in the nervous system and can stimulate neural progenitor cells: those cells from which neurons develop. The problem is low potency and difficulty reliably getting natural vitamin K through the blood-brain barrier.
Neurodegenerative diseases like Alzheimer's and Parkinson's gradually destroy nerve cells in the brain. According to the World Health Organization, Alzheimer's accounts for 60 to 70 percent of all dementia diseases, with roughly 55 million people affected worldwide. Therapeutics that halt the disease process have only been available since 2023. Once lost, neurons do not grow back.
Hybrid Structure from Two Vitamins
The team led by Associate Professor Yoshihisa Hirota and Professor Yoshitomo Suhara from the Department of Bioscience and Engineering at Shibaura Institute of Technology synthesized 12 vitamin K analogs. In these, as the researchers published in ACS Chemical Neuroscience, the natural side chain of vitamin K was replaced with a chain of retinoic acid. Retinoic acid is the active form of vitamin A and a well-known strong regulator of cell differentiation.
The most promising molecule, designated compound 7 in the publication, achieved approximately three times the activity of natural vitamin K in converting neural progenitor cells to neurons in cell experiments. The mechanism of action: the compounds activate the mGluR1 receptor, which controls differentiation of these stem cells. In pharmacological mouse studies, the substances showed effective penetration of the blood-brain barrier without toxic effects at the doses tested so far.
In Comparison With Previous Alzheimer's Research
Previously approved Alzheimer's therapies target amyloid plaques, degraded protein fragments that damage nerve cells. Lecanemab (Leqembi), which the FDA approved in 2023, slowed cognitive decline according to the CLARITY-AD study in the New England Journal of Medicine by 27 percent versus placebo over 18 months. This is significant progress. Lost neurons do not regenerate from this.
Stem cell therapies for the brain follow a different path: cells are cultured outside the body and transplanted, which means high costs and rejection risks and remains experimental. The Japanese vitamin K compounds instead stimulate the body's own neural stem cells directly and from within. A comparable idea had decades-long research on brain-stimulating growth factor BDNF (Brain-Derived Neurotrophic Factor). This barely crosses the blood-brain barrier reliably, which is why no drug from this class has yet been approved. That the new compounds cross exactly this obstacle is the decisive difference from many previous approaches.
From Mouse to Human: Three Prerequisites
The path from a cell experiment to clinical application takes longer for central nervous system diseases than in most other areas. Three conditions must be met before the new compounds can be tested in humans.
First, efficacy and safety must be demonstrated in a primate model, since results from mouse studies frequently do not reproduce in humans. The research team plans further animal studies as an immediate next step. Second, systematic dosing data is needed. Retinoic acid compounds are potent and at too high concentrations can themselves damage cells. Compound 7 showed no toxicity in previous experiments, but dose-finding studies are completely lacking. Third, the clinical indication must be clearly defined. Alzheimer's and Parkinson's differ substantially in affected brain regions and cell types. Whether a single drug class can address both diseases or whether specific variants are needed remains open.
If all three steps succeed, a first clinical Phase I study could begin in a few years. For a disease group that has so far barely benefited from restorative approaches, that would be a qualitatively new step.