Those of us readying our winning lottery tickets in hopes of buying the medicinal key to immortality might need to wait a little longer.

Earlier today, a study published in Cell Metabolism concluded that, contrary to recent research, increased levels of the protein Growth Differentiation Factor 11 (GDF-11) actually predicted worsening muscle regeneration in mice. Far from announcing GDF-11 as a potential candidate for the fountain of youth, as Harvard University researchers did in 2013 when they theorized that GDF-11 might be responsible for rejuvenating older mice who received blood transfusions from their younger kin, the study authors found that GDF-11 does the exact opposite in mice, and possibly humans.

One of the problems with the earlier positive research on GDF-11 was one of specificity, the authors explain. Previous studies which had observed decreasing levels of GDF-11 in aging mice, found in the blood, did so by using tests that weren’t specific enough. GDF-11 is remarkably similar (90 percent) in molecular composition to another common protein, myostatin, and it was actually levels of myostatin that were decreasing. Once the authors created tests that could specifically measure GDF-11, they found that if anything, the amount of GDF-11 circulating in the blood only increased with age in both mice and people.

As they go on to elaborate, it was rather peculiar that GDF-11 was considered a potential agent for reversing the muscle loss that comes with aging in the first place, considering its similarity to myostatin, already known to weaken muscle growth. And in further trials, including injecting young mice with GDF-11, their suspicions proved to be well-founded. “Our study shows that GDF11, similar to myostatin, inhibits muscle regeneration,” study author Dr. David Glass of the Novartis Institutes for BioMedical Research told Medical Daily.

But not all hope is lost for our fountain seekers. There’s already been research into drugs that serve as myostatin inhibitors, with early promising results. The authors, noting that several of the older people they studied had high levels of GDF-11, believe that stemming the protein in high GDF-11 individuals suffering from muscle-related disorders could prove to be an avenue of treatment. And if nothing else, these results don’t invalidate the Harvard mice studies at all, they only suggest that we’ve been looking in the wrong places. That key to agelessness might still be lying around somewhere. We just have to find it.

Source: Egerman M.A., et al. GDF11 increases with age and inhibits skeletal muscle regeneration. Cell Metabolism. 2015.