Federal health advisers are meeting to review a group of controversial chemicals called peptides. The unapproved injections have become a popular wellness trend, promoted by influencers and celebrities for building muscle, healing injuries and other uses.

The committee will discuss whether compounding pharmacies can make the peptides in question. But FDA scientists say there’s little — if any — evidence they work in humans.

As regulators weigh whether pharmacies can legally compound wellness peptides, companies are preparing for a repeat of the GLP-1 boom—only this time with even murkier science.