Compounding warning letters to 503A facilities between 2017 and 2021 ScienceDirect Beyond the Headlines: FDA Warning Letters to GLP 1 Compounders Spencer Fane 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 Is BPC 157 Banned? Oral vs. Injectable Forms Explained 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 FDA Targets GLP 1 and Peptide Compounding, Advertising and 'Research Use Only' Labeling