Metabolic & Weight Lilly Turned the Receptor On, Amgen Turned It Off, and Both Strip Weight. The Map Came Four Years Late.
Eli Lilly's tirzepatide switches the gut-hormone receptor on. Amgen's MariTide blocks it. Both drive weight loss, and until a publicly funded Cambridge mouse study, no one had cleanly mapped how one receptor works in both directions.
By Lena Marshall · August 16, 2026