It isn't a coincidence, and it isn't necessarily a sign the compounds don't work. It's a predictable consequence of who funds clinical trials, and why.
A compound's evidence tier on Geroevidence reflects who can fund the trial that would prove it — almost as much as it reflects the underlying biology.
Look across Geroevidence's intervention index and a pattern is hard to miss: the two compounds with Strong, Phase III, hard-outcome evidence — GLP-1 agonists and SGLT2 inhibitors — are both patented pharmaceutical drug classes, developed and tested by companies that could recoup a multi-hundred-million-dollar trial cost through patent-protected sales. Taurine, berberine, spermidine, NMN, and NR are unpatentable or weakly patentable natural compounds, sold as supplements. No company has the same financial incentive to fund a decade-long, multi-thousand-patient outcome trial for a compound any competitor can sell the moment it shows positive results.
Academic labs and public funders like the NIA do study unpatentable compounds — the Interventions Testing Program exists for exactly this reason, testing candidates like rapamycin, acarbose, and 17α-estradiol in mice regardless of commercial patentability. But public and academic funding moves slower and reaches far fewer compounds than industry-funded drug trials. This is why so many supplements have a real, peer-reviewed mouse study (Singh 2023 for taurine is a clear example) but no equivalent human outcome trial: the mouse study was academically fundable; the decade-long human trial, for an unpatentable compound, generally isn't, absent a philanthropic or public funder stepping in specifically.
An Emerging or under-review tier on Geroevidence is not a verdict that a compound doesn't work — it's a description of how much, and what kind, of human trial evidence exists. Some of that gap is structural (no one can profit enough to fund the trial) rather than scientific (the early evidence looks weak). Both metformin's repurposed-drug funding advantage and the TAME trial's reliance on public and philanthropic backing illustrate how much trial funding, not just biology, shapes what tier a compound ends up at.
"Lacks human trial data" and "doesn't work" are different claims, and conflating them runs in both directions — it's just as much a mistake to assume an Emerging-tier compound is debunked as it is to assume it's validated. Geroevidence's evidence ladder is built to report the former honestly, without implying the latter either way.