The Longevity Marketplace

In both halves of the series, the first step holds up in people. In small studies, short on-and-off courses of dasatinib and quercetin lowered markers of senescent cells in tissue and were generally tolerated, and oral NMN and NR reliably raise NAD+ in the blood and have looked safe over weeks to a few months. The next step, a benefit in daily life, is where the evidence thins out. No senolytic has been approved to treat aging. A 2025 pooled analysis of NMN and NR trials, led by Konstantinos Prokopidis at the University of Liverpool, found no consistent gain in grip strength or muscle mass in older adults. At the University of Delaware, Christopher Martens led a trial in which 52 older adults with amnestic mild cognitive impairment, a mild but measurable memory problem, took 500 milligrams of NR twice a day for 12 weeks. Their blood NAD+ roughly doubled. Blood flow rose in the left hippocampus, a memory center of the brain, but their memory scores did not improve by a statistically significant margin.

Part 3 first called a 2025 phase 2b trial of a senolytic injected into the eye for diabetic macular edema, a swelling at the back of the eye caused by diabetes, more encouraging, and it now carries a correction. The trial was Unity Biotechnology's ASPIRE study of a drug called UBX1325, in 52 patients. By the company's own May 2025 announcement, the drug missed its main goal of matching the standard treatment, aflibercept, on vision averaged over weeks 20 and 24, though it did match it at week 36. In the same announcement Unity said it was laying off its entire workforce and exploring what it called strategic alternatives, such as a sale. On Sept. 18, 2025, according to the company's filing with the Securities and Exchange Commission, its stockholders approved a plan to dissolve Unity.

NMN's legal footing has held steady. After the September 2025 reversal, the FDA sent letters on Dec. 2, 2025, reinstating the new dietary ingredient notifications of two NMN makers, SyncoZymes and Inner Mongolia Kingdomway Pharmaceutical. NMN is now a lawful supplement ingredient, though a company putting it in a new product is still expected to file a notification first, the paperwork the FDA requires before anyone sells an ingredient that was not in supplements before 1994. We found no further FDA action on NMN this year. Separately, the FDA said in December 2025 that it is considering a rule letting the "not evaluated by the FDA" disclaimer appear once on a label instead of on every panel that makes a claim. The disclaimer itself would stay.

Part 4 turns the checking into a few plain questions. Does the capsule hold the same ingredients as the trials, at doses anywhere near theirs, taken on the same on-and-off schedule? Has this formula ever been tested in people? With NMN and NR, the matching question is whether a study showed more than a higher number on a blood test. The Amsterdam work adds a doubt. If NAD+ in the blood holds steady with age, the drop the pills are meant to fix would have to be in muscle or the brain, and a blood test does not measure those. At the clinic end, Part 7 points out that the measures with the strongest evidence for a longer, healthier life, such as controlling blood pressure and staying physically active, need no membership.

The answers will come from larger trials. Part 3 notes that bigger randomized studies of dasatinib and quercetin in Alzheimer's disease are under way or planned, and Kirkland, who has since moved from Mayo to Cedars-Sinai in Los Angeles to direct its Center for Advanced Gerotherapeutics, leads the Translational Geroscience Network, which Cedars-Sinai says was overseeing nearly 90 active clinical trials as of April 2025. For NMN and NR, the open question is whether a longer trial can show NAD+ rising in muscle or brain tissue and, with it, a change people can feel, in walking speed or on a memory test.