Injectable Peptides: Out of the Back Alley and Into the Light? Berkley Lifesciences 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 The U.S. Food and Drug Administration is moving toward allowing compounding pharmacies to produce more than a dozen injectable peptides that were banned because of potentially significant safety risks, the New York BPC 157: Miracle Healing Peptide or Hidden Danger?