Sources: U.S. Food and Drug Administration (FDA) Compounding and the FDA (503A & 503B guidance) FDA warning letters on unapproved peptide products National Institutes of Health (NIH) PubMed fda warning bpc 157 peptide products New Details 157 People are turning themselves into lab rats': the injectable peptides craze sweeping the US Well actually The Guardian FDA Targets GLP 1 and Peptide Compounding, Advertising and 'Research Use Only' Labeling Gray Market Peptides: So Much Hype, So Little Data The FDA has issued warning letters to multiple companies marketing compounded Retatrutide, an investigational drug from Eli Lilly still in Phase II trials. While early studies have shown promising weight loss results, Retatrutide