What changed, and where it is written down
FDA actions, litigation and trial readouts that affect peptide research, each summarized from the primary document with the source linked.
FDA in 2026: telehealth GLP-1 letters and a line on retatrutide
FDA sent 30 warning letters to telehealth firms over compounded GLP-1 marketing in March 2026, and its GLP-1 guidance page now states that retatrutide and cagrilintide cannot be used in compounding.
CagriSema in 2026: head-to-head results and a pending FDA decision
Novo Nordisk's cagrilintide/semaglutide combination missed non-inferiority to tirzepatide in REDEFINE 4, then reported superiority over a lower tirzepatide dose in REIMAGINE 5. An FDA decision is expected in Q4 2026.
Lilly files six lawsuits against US retatrutide sellers
On 12 August 2026 Eli Lilly announced six federal lawsuits against US businesses it says sell unapproved retatrutide, including sellers labelling the product "research use only". Retatrutide is not approved anywhere.
Retatrutide: Lilly reports TRIUMPH-2 and TRIUMPH-3 phase 3 results
On 23 July 2026 Lilly reported topline results from two more 80-week phase 3 trials of retatrutide and said it plans to submit the drug to FDA in the first quarter of 2027.