Angiotensin III (Ang III) is a bioactive heptapeptide that is formed from the degradation of the Angiotensin II peptide by aminopeptidase A. In peripheral Angiotensin systems, Angiotensin II is the main effector peptide in the systemic circulation, although exogenous Angiotensin III can be as potent as Angiotensin II in, for example, stimulating aldosterone secretion or inhibiting renin release. In the rat brain, Angiotensin III was found to be equipotent with Angiotensin II as a pressor agent or dipsogen and was bound as avidly to the nervous system as Angiotensin II. Angiotensin receptor subtype AT1 has the greater affinity towards Angiotensin II and is also responsive to Angiotensin III, while the AT2 receptor subtype appears to be more sensitive to Angiotensin III but less responsive to Angiotensin II. Angiotensin III enhances blood pressure, vasopressin release and thirst when it is centrally administrated. Angiotensin III infusion increases blood pressure in healthy volunteers and hypertensive patients as well as augments aldosterone release. Although Angiotensin III does not change renal function in humans, it induces natriuresis in AT, receptor-blocked rats likely by binding to AT2 receptors. In addition, in cultured renal cells, this peptide stimulates the expression of many growth factors, proinflammatory mediators, and extracellular matrix proteins.

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 The Seractide, that was ultimately withdrawn by FDA in 2014 for safety reasons.

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.

Thymopentin is a synthetic pentapeptide which is the active site of the naturally occurring hormone thymopoietin with immunomodulating properties. Thymopentin can specifically promote the differentiation and maturation of thymic T cells and natural killer cells (NK) and enhance the function of T helper cells. thymic can achieve a two-way adjustment to the immune system by increasing the levels of intracellular cyclic adenosine monophosphate, elevating the activity of T cells, and regulating the proportions of T cell subsets. As an immunomodulating agent, Thymopentin is clinically used in the treatments of autoimmune diseases, such as e.g. atopic dermatitis, chronic lymphocytic leukemia, Sezary's syndrome, rheumatoid arthritis, as well as decreased immune competency in elder surgical patients. Due to poor membrane permeability, extensive metabolism in the GI, and extremely short half-life of 30 s, repeated injections or i.v infusions of Thymopentin are necessary which greatly restrict its clinical applications.