Linaclotide (marketed under the trade name Linzess and Constella) is a peptide agonist of the guanylate cyclase 2C (GC-C). Once linaclotide and its active metabolite binds to GC-C, it has local effect on the luminal surface of the intestinal epithelium. Activation of GC-C by linaclotide results in the intra- and extracellular increase of cyclic guanosine monophosphate concentrations (cGMP). This elevation of cGMP levels stimulates the secretion of chloride and bicarbonate into the intestinal lumen via activation of cystic fibrosis transmembrane conductance regulator (CFTR) ion channel. The metabolite of linaclotide MM-419447 (CCEYCCNPACTGC) contributes to the pharmacologic effects of linaclotide. Ultimately, linaclotide helps patients with IBS (especially with constipation) as GI transit is accelerated and the release of intestinal fluid is increased. In animal models, a decrease in visceral pain after administration of linaclotide may be observed. A decrease in the activity of pain-sensing nerves occurs as a result of an increase in extracellular cGMP. It was approved by the FDA in August 2012 for the treatment of chronic idiopathic constipation and irritable bowel syndrome with constipation (IBS-C) in adults.

Liraglutide is an acylated human Glucagon-Like Peptide-1 (GLP-1) receptor agonist with 97% amino acid sequence homology to endogenous human GLP-1(7-37). GLP-1(7-37) represents <20% of total circulating endogenous GLP-1. Like GLP-1(7-37), liraglutide activates the GLP-1 receptor, a membranebound cell-surface receptor coupled to adenylyl cyclase by the stimulatory G-protein, Gs, in pancreatic beta cells. Liraglutide increases intracellular cyclic AMP (cAMP) leading to insulin release in the presence of elevated glucose concentrations. This insulin secretion subsides as blood glucose concentrations decrease and approach euglycemia. Liraglutide also decreases glucagon secretion in a glucose-dependent manner. The mechanism of blood glucose lowering also involves a delay in gastric emptying. GLP-1(7-37) has a half-life of 1.5-2 minutes due to degradation by the ubiquitous endogenous enzymes, dipeptidyl peptidase IV (DPP-IV) and neutral endopeptidases (NEP). Unlike native GLP-1, liraglutide is stable against metabolic degradation by both peptidases and has a plasma half-life of 13 hours after subcutaneous administration. The pharmacokinetic profile of liraglutide, which makes it suitable for once daily administration, is a result of self-association that delays absorption, plasma protein binding and stability against metabolic degradation by DPP-IV and NEP. Liraglutide, a subcutaneous, once-daily GLP-1 agonist, is approved for the treatment of type 2 diabetes in the United States and Europe. It also has been studied for weight loss. Liraglutide helps to induce and sustain weight loss in patients with obesity. Its efficacy is comparable to other available agents but it offers the unique benefit of improved glycemic control.

Tesamorelin is an analog of human growth hormone-releasing factor (GRF). The peptide precursor of tesamorelin acetate is produced synthetically and is comprised of the 44 amino acid sequence of human GRF. In vitro, tesamorelin binds and stimulates human GRF receptors with similar potency as the endogenous GRF. GRF, also known as growth hormone-releasing hormone (GHRH), is a hypothalamic peptide that acts on the pituitary somatotroph cells to stimulate the synthesis and pulsatile release of endogenous growth hormone (GH), which is both anabolic and lipolytic. GH exerts its effects by interacting with specific receptors on a variety of target cells, including chondrocytes, osteoblasts, myocytes, hepatocytes, and adipocytes, resulting in a host of pharmacodynamic effects. Some, but not all these effects, are primarily mediated by IGF-1 produced in the liver and in peripheral tissues. Tesamorelin is the first and, so far, only treatment indicated for the reduction of excess abdominal fat in patients with HIV-associated lipodystrophy. Tesamorelin is effective in improving visceral adiposity and body image in patients with HIV-associated lipodystrophy over 26-52 weeks of treatment. Potential limitations for its use include high cost and lack of long-term safety and adherence data. Tesamorelin provides a useful treatment option for management of patients with significant lipodystrophy related to HIV infection.

Lanreotide is a medication used in the management of acromegaly and symptoms caused by neuroendocrine tumors, most notably carcinoid syndrome. It is a long-acting analog of somatostatin. It is available in several countries, including the United Kingdom, Australia and Canada, and was approved for sale in the United States by the Food and Drug Administration on August 30, 2007. Lanreotide was developed in the lab of Dr. David H. Coy, School of Medicine. Dr. Coy serves as Director of the Peptide Laboratory. Lanreotide (as lanreotide acetate) is manufactured by Ipsen, and marketed under the trade name Somatuline. The mechanism of action of lanreotide is believed to be similar to that of natural somatostatin. Lanreotide has a high affinity for human somatostatin receptors (SSTR) 2 and 5 and a reduced binding affinity for human SSTR1, 3, and 4. Activity at human SSTR 2 and 5 is the primary mechanism believed responsible for GH inhibition. Like somatostatin, lanreotide is an inhibitor of various endocrine, neuroendocrine, exocrine and paracrine functions. Lanreotide inhibits the basal secretion of motilin, gastric inhibitory peptide and pancreatic polypeptide, but has no significant effect on the secretion of secretin. Lanreotide inhibits postprandial secretion of pancreatic polypeptide, gastrin and cholecystokinin (CCK). In healthy subjects, lanreotide produces a reduction and a delay in post-prandial insulin secretion, resulting in transient, mild glucose intolerance.

Pramlintide is an analog of human amylin. Amylin is co-secreted with insulin from pancreatic beta cells and acts centrally to slow gastric emptying, suppress postprandial glucagon secretion, and decrease food intake. These actions complement those of insulin to regulate blood glucose concentrations. Amylin is relatively deficient in patients with type 2 diabetes, depending on the severity of beta-cell secretory failure, and is essentially absent in patients with type 1 diabetes. Through mechanisms similar to those of amylin, pramlintide improves overall glycemic control, reduces postprandial glucose levels, and reduces bodyweight in patients with diabetes using mealtime insulin. SYMLIN® (pramlintide acetate) is indicated for patients with type 1 or type 2 diabetes who use mealtime insulin and have failed to achieve desired glycemic control despite optimal insulin therapy.