Glucagon is a polypeptide hormone identical to human glucagon that increases blood glucose and relaxes smooth muscle of the gastrointestinal tract. Glucagon is synthesized in a special non-pathogenic laboratory strain of Escherichia coli bacteria that has been genetically altered by the addition of the gene for glucagon. Glucagon generally elevates the concentration of glucose in the blood by promoting gluconeogenesis and glycogenolysis. Glucagon also decreases fatty acid synthesis in adipose tissue and the liver, as well as promoting lipolysis in these tissues, which causes them to release fatty acids into circulation where they can be catabolised to generate energy in tissues such as skeletal muscle when required. Glucose is stored in the liver in the form of the polysaccharide glycogen, which is a glucan (a polymer made up of glucose molecules). Liver cells (hepatocytes) have glucagon receptors. When glucagon binds to the glucagon receptors, the liver cells convert the glycogen into individual glucose molecules and release them into the bloodstream, in a process known as glycogenolysis. As these stores become depleted, glucagon then encourages the liver and kidney to synthesize additional glucose by gluconeogenesis. Glucagon turns off glycolysis in the liver, causing glycolytic intermediates to be shuttled to gluconeogenesis. Glucagon also regulates the rate of glucose production through lipolysis. Glucagon induces lipolysis in humans under conditions of insulin suppression (such as diabetes mellitus type 1). Glucagon increases blood glucose concentration and is used in the treatment of hypoglycemia. Glucagon administered through a parenteral route relaxes smooth muscle of the stomach, duodenum, small bowel, and colon. Glucagon is also indicated as a diagnostic aid in the radiologic examination of the stomach, duodenum, small bowel, and colon when diminished intestinal motility would be advantageous.

ZIRCONIUM ZR-89 is used in specialized diagnostic applications using positron emission tomography (PET). An increasing interest in zirconium-89 can be attributed to the isotope's half-life, which is compatible with antibody imaging. ZR-89 as a radioimmunoconjugate, [89Zr]DFO-HuMab-5B1 was used in preclinical animal models of lung, colorectal, and pancreatic malignancies for PET imaging and was in a phase I trial for pancreatic cancer. In addition, the use of 89Zr-DFO-nimotuzumab that had low organ absorbed dose and effective dose made it suitable for potential human use for immunoPET imaging of epidermal growth factor receptor I. It is known, that epidermal growth factor receptor upregulation is associated with enhanced proliferation and drug resistance in a number of cancers.

Saralasin is an angiotensin II analogue which was developed for the treatment of hypertension in 1970s. For many years saralasin was supposed to be angiotensin receptors blocker, but recent studies have revealed that its pharmacological action can be explained by agonistic behavior toward angiotensin II receptor. The drug was approved by FDA under the name Sarenin, however, it is no longer available on the market.

Seractide is a polypeptide hormone corresponding to thirty-nine amino acids of human corticotropin that differs from full-length human corticotropin at four positions. Seractide is potent endogenous melanocortin receptor 2 (MC ) agonist. Seractide stimulates the cortex of the adrenal gland and boosts the synthesis of corticosteroids, mainly glucocorticoids but also sex steroids (androgens). Seractide, was approved by FDA in 1978, but was never marketed. The Seractide, that was ultimately withdrawn by FDA in 2014 for safety reasons.