A Phase 2 trial just began testing whether a GLP-1 drug can slow brain shrinkage in progressive MS, and it could finally answer a question diabetes researchers have been circling for years – Image for illustrative purposes only (Image credits: Pixabay)
A Phase 2 clinical trial has started enrolling adults with progressive multiple sclerosis at Johns Hopkins University. Researchers aim to determine whether pegsebrenatide, a GLP-1 receptor agonist, can slow the rate of brain tissue loss over two years. The study addresses a long-standing observation from diabetes care that these medications may offer unexpected neurological benefits beyond blood sugar control.
Observational Clues from Diabetes Patients
Endocrinologists have tracked cognitive outcomes in people taking GLP-1 drugs for Type 2 diabetes for more than a decade. Several large analyses found modest reductions in dementia risk and slower cognitive decline among long-term users compared with those on other treatments. One review of roughly 9,000 participants showed a 14 percent lower risk of cognitive decline with dulaglutide. Danish cohort studies reported dementia risk reductions ranging from 11 to 53 percent, though sample sizes for confirmed dementia cases remained limited in some datasets. The pattern held across different populations even after accounting for weight loss and cardiovascular improvements. Still, these findings came from observational data rather than trials designed to measure brain volume directly.
Proposed Mechanisms Inside the Brain
GLP-1 receptor agonists influence several processes linked to neurodegeneration. Animal research indicates they can enhance synaptic plasticity, reduce neuroinflammation, and limit oxidative stress on neurons. The drugs also improve vascular health by lowering blood pressure, blood sugar, and stroke risk, which may indirectly preserve white-matter integrity. A separate line of evidence points to insulin signaling. Genetic studies have linked higher insulin resistance to poorer cognitive performance and changes in brain structure, independent of diagnosed diabetes. If GLP-1 drugs act on brain insulin pathways, they could address an upstream driver of cell loss rather than merely providing side benefits.
Structure and Goals of the TAG-MS Study
The trial, known as TAG-MS, will randomize about 120 adults with progressive MS who have been clinically stable on existing therapy for at least one year. Participants receive weekly subcutaneous injections of pegsebrenatide or placebo for 96 weeks, with doses starting at 5 mg and increasing to 10 mg. The primary measure is change in normalized brain parenchymal volume on MRI, a precise marker of overall brain tissue loss. Secondary outcomes include regional brain volumes and retinal nerve fiber layer thickness, which serves as a non-invasive window into central nervous system damage. Ellen Mowry leads the study at Johns Hopkins. Pegsebrenatide was specifically engineered to target microglia and astrocytes, the brain support cells whose chronic activation contributes to progressive disability in MS. Earlier Phase 2 data in Parkinson’s disease suggested the drug may slow motor decline, particularly in younger patients. Whether similar effects appear in MS will become clearer when results are available in roughly two years.
Current Limits and Next Steps
No GLP-1 medication is approved for any cognitive or neurodegenerative indication. Human evidence for Alzheimer’s remains mixed, with animal models showing reductions in amyloid and tau but limited clinical trial success once symptoms are established. The TAG-MS design deliberately focuses on progressive MS to test brain-volume preservation in a population where neurodegeneration occurs without frequent relapses. If the trial meets its primary endpoint, it would provide the first randomized confirmation that a GLP-1 drug can measurably slow brain atrophy. Additional Parkinson’s and Alzheimer’s prevention studies are expected to report around the same time, helping clarify whether the observed signals represent a class-wide effect or depend on specific drug design and timing of intervention.