Sinapultide is a synthetic peptide used to mimic human lung surfactant protein B, the most important surfactant protein for a proper functioning of the respiratory system. Protein B lowers surface tension at the air-liquid interface of the alveolar surfaces during respiration and stabilizes the alveoli against collapse at resting transpulmonary pressures. A deficiency of pulmonary surfactant in premature infants results in respiratory distress syndrome. Sinapultide compensates for the deficiency of surfactant and restores surface activity to the lungs of these infants. Sinapultide was originally developed in the Scripps Research Institute and then licensed to Windtree Therapeutics (formerly Discovery Laboratories, Inc.). Sinapultide is the active ingredient of Lucinactant, a liquid medication to treat infant respiratory distress syndrome. Lucinactant was approved by the FDA in 2012 and sold under the trademark Surfaxin, but in 2015 it was discontinued by Discovery Laboratories, Inc in favor of Aerosurf, another drug containing Sinapultide.

Peginesatide (trade name Omontys, formerly Hematide), developed by Affymax and Takeda, is an erythropoietic agent, a functional analog of erythropoietin. It was approved by the U.S. Food and Drug Administration for treatment of anemia associated with chronic kidney disease (CKD) in adult patients on dialysis. Peginesatide is a synthetic peptide, attached to polyethylene glycol ("PEGylated"). It mimics the structure of erythropoietin, the human glycoprotein which promotes red blood cell development. Peginesatide binds to and activates the human erythropoietin receptor and stimulates erythropoiesis in human red cell precursors in vitro.

Gonadorelin is a synthetic decapeptide prepared using solid phase peptide synthesis. GnRH is responsible for the release of follicle stimulating hormone and leutinizing hormone from the anterior pitutitary. In the pituitary GnRH stimulates synthesis and release of FSH and LH, a process that is controlled by the frequency and amplitude of GnRH pulses, as well as the feedback of androgens and estrogens. The pulsatility of GnRH secretion has been seen in all vertebrates, and it is necessary to ensure a correct reproductive function. Thus a single hormone, GnRH, controls a complex process of follicular growth, ovulation, and corpus luteum maintenance in the female, and spermatogenesis in the male. Its short half life requires infusion pumps for its clinical use. Gonadorelin is used for the treatment of amenorrhea, delayed puberty, and infertility the administration of gonadorelin is used to simulate the physiologic release of GnRH from the hypothalamus in treatment of delayed puberty, treatment of infertility caused by hypogonadotropic hypogonadism, and induction of ovulation in those women with hypothalamic amenorrhea. This results in increased levels of pituitary gonadotropins LH and FSH, which subsequently stimulate the gonads to produce reproductive steroids.

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.

Somatorelin is 29 amino acid analogue of human growth hormone-releasing hormone used as a diagnostic agent for determining growth hormone deficiency. Growth-hormone-releasing hormone (GHRH, somatoliberin) is the hypothalamic peptide hormone that specifically stimulates synthesis and release of growth hormone (GH, somatotropin) by somatotrope cells of the anterior pituitary gland. The hypothalamic hormone growth hormone (GH)-releasing hormone (GHRH) acts on specific GHRH receptors (GHRH-R) in the anterior pituitary gland to stimulate the synthesis and secretion of GH and to promote somatotrope expansion. Somatorelin is applied to determine the somatotropic function of the anterior pituitary gland in cases of suspected growth hormone deficiency. The test distinguishes between pituitary and hypothalamic disorders but is not suitable as a screening test for growth hormone deficiencies. Somatorelin has been used in trials studying the treatment of Aging, Elderly, Sleep Disorders, Hormone Deficiency, and Mild Cognitive Impairment.