Somatostatin (also known as growth hormone-inhibiting hormone) is a naturally-occurring peptide hormone that regulates the endocrine system. Somatostatin is produced in gastrointestinal (GI) tract, pancreas, hypothalamus, and central nervous system (CNS) and some other organs. Somatostatin is initially secreted as a 116 amino acid precursor, preprosomatostatin, which undergoes endoproteolytic cleavage to prosomastatin. Prosomastatin is further process into two active forms, shorter isoform somatostatin-14 works primarily in the brain, while the longer somatostatin-28 (SST-28) form operates in the GI tract. Somatostatin produces predominantly neuroendocrine inhibitory effects across multiple systems. It is known to inhibit GI, endocrine, exocrine, pancreatic, and pituitary secretions, as well as modify neurotransmission and memory formation in the CNS. Somatostatin binds to six different receptors in various systems and cells throughout the body to produce its regulatory effect. These receptors are specific to somatostatin and classify as G-protein coupled receptors (GPCR). Somatostatin half-life is between 1 to 3 minutes. Due to its short half-life, somatostatin has been formulated exogenously in much more stable forms with a longer half-life; this allows for its primary clinical use, which is the treatment of neuroendocrine tumors.

Norgestomet is a synthetic derivative of progesterone with improved oral activity due to its 17α-acetate side chain. In veterinary medicine norgestomet is used for the synchronisation of oestrus in cattle. It is administered as a subcutaneous ear implant (containing 3 mg norgestomet; to be removed after 9 to 10 days), in combination with a single intramuscular injection containing 3 mg norgestomet and 5 mg oestradiol valerate. The injection is to be given immediately after application of the implant. Norgestomet is not used in human medicine. It is a steroidal progestin of the 19-norprogesterone group.

Levomethadyl acetate (LAAM) is a synthetic opioid agonist with actions qualitatively similar to morphine (a prototypic mu agonist) and affecting the central nervous system (CNS) and smooth muscle. Principal actions include analgesia and sedation. Tolerance to these effects develops with repeated use. An abstinence syndrome generally occurs upon cessation of chronic administration similar to that observed with other opiates, but with slower onset, more prolonged course, and less severe symptoms. LAAM exerts its clinical effects in the treatment of opiate abuse through two mechanisms. First, LAAM cross-substitutes for opiates of the morphinetype, suppressing symptoms of withdrawal in opiate-dependent individuals. Second, chronic oral administration of LAAM can produce sufficient tolerance to block the subjective “high” of usual doses of parenterally administered opiates. Since the introduction of levomethadyl in 1995, the manufacturer has received increasing reports of severe cardiac-related adverse events, including QT interval prolongation, Torsades de Pointes and cardiac arrest. Other cardiac-related adverse events have also been reported, including arrhythmias, syncope, and angina. These events led to the removal of levomethadyl from the European market in March 2001. A very small number of patients may benefit from levomethadyl, but the risk of continued distribution and use no longer outweighs the overall benefits.

Vapreotide (Sanvar) is cyclic octapeptide analog of somatostatin with higher metabolic stability than the parent hormone and developed by Debiopharm Group for the treatment of esophageal variceal bleeding in patients with cirrhotic liver disease and AIDS-related diarrhea. Somatostatin inhibits the secretion of vasodilatory peptides from the gastrointestinal tract, including glucagon, which has been shown to contribute to the maintenance of portal hypertension. While natural somatostatin has a very short half-life (3 min), the elimination half-life of vapreotide is reported to be approximately 10 times longer than that of its parent compound. Pharmacodynamic studies of healthy volunteers demonstrated suppression of gastric acid secretion and inhibition of the secretion of pancreatic enzyme, which is similar to somatostatin. Vapreotide has demonstrated efficacy in the early management of acute variceal hemorrhage but only based on combined primary endpoints of hemostasis and survival after 5 days. In addition, vapreotide’s efficacy is limited to only one major study performed in Europe and not yet in the United States. Although it did not show a significant reduction in mortality, vapreotide’s observed the effect on hemostasis, as well as its favorable safety profile. Adverse effects that occurred in the vapreotide trials were generally mild and primarily included gastrointestinal symptoms and alterations of the gastrointestinal hormonal system. Vapreotide not recommended for approval by an FDA Advisory Panel due to Insufficient evidence that the drug provided a benefit in the treatment for acute esophageal variceal bleeding.

Atosiban (brand name Tractocile) is a competitive antagonist of human oxytocin at receptor level. In rats and guinea pigs, atosiban was shown to bind to oxytocin receptors, to decrease the frequency of contractions and the tone of the uterine musculature, resulting in a suppression of uterine contractions. Atosiban was also shown to bind to the vasopressin receptor, thus inhibiting the effect of vasopressin. Tractocile is indicated to delay imminent pre-term birth in pregnant adult women with: − regular uterine contractions of at least 30 seconds duration at a rate of ≥ 4 per 30 minutes − a cervical dilation of 1 to 3 cm (0-3 for nulliparas) and effacement of ≥ 50% − a gestational age from 24 until 33 completed weeks − a normal foetal heart rate. Atosiban does not have U.S. Food and Drug Administration (FDA) approval for use in the United States.

Buserelin is a synthetic peptide analog of the luteinizing hormone-releasing hormone (LHRH) agonist, which stimulates the pituitary gland's gonadotrophin-releasing hormone receptor (GnRHR). Buserelin is used for palliative treatment of prostate cancer, and for treatment of endometriosis. Buserelin is also used for infertility treatment to prepare the pituitary gland before starting treatment with gonadotrophins (FSH and LH) to artificially stimulate ovulation.

Avorelin is a superagonist of natural luteinizing-hormone-releasing-hormone. Avorelin has been formulated in high molecular weight polylactic glycolic acid to afford protracted and continuous release of the peptide from subcutaneous implants. Avorelin has been in phase II clinical trials by Mediolanum for the treatment of prostate cancer, breast cancer and endometriosis. However, this research has been discontinued. Adverse events mainly related to androgen suppression (hot flushes, decreased libido and impotence) or the nature of the disease (skeletal pain).

Cu-64 is an isotope of copper with potential use in PET imaging and the targeted radiotherapy of cancer. It has a complex decay scheme, with electron capture, beta-emission and positron emission branches. Cu-64 in the most simple salt form as well as linked to a variety of bioactive molecules can be used as theranostic agents in human malignancies such as prostate, glioblastoma, melanoma, breast cancers) and also diagnosis of human copper-associated diseases such as atherosclerosis, Alzheimer’s etc. There are some examples of investigational Cu-64-based radiopharmaceuticals: Cu-64-ATSM for imaging hypoxia, Cu-64-labeled peptides for tumor-receptor targeting, Cu-64-labeled monoclonal antibodies for targeting tumor antigens, and Cu-64-labeled nanoparticles for cancer targeting.

Anecortave is a novel angiogenesis inhibitor used in the treatment of the exudative (wet) form of age-related macular degeneration. It will be marketed by Alcon as anecortave acetate (AA) for depot suspension under the trade name Retaane. In 2007 they received their letter of approval for Retaane’s indication to treat wet age-related macular degeneration (AMD), but final approval would require the completion of an additional clinical study. As a result, the Anecortave Acetate Risk-Reduction Trial (AART) was continued to be supported by Alcon. This study looked at the efficacy of Retaane to reduce the progression of the dry from of AMD to the wet-form. In 2008, Alcon Inc. announced they were terminating the development of anecortave acetate for the prevention of developing sight-threatening choroidal neovascularization secondary to age-related macular degeneration. In 2009, Alcon Inc. announced they would terminate the development of the drug for the reducing intraocular pressure associated with glaucoma. Currently, anecortave acetate is not on the market or being made for therapeutic use by Alcon Inc.[7] This could be due to the lack of efficacy of clinical trials with anecortave acetate or because of newer more efficacious products that are currently on the market. Anecortave acetate functions as an antiangiogenic agent, inhibiting blood vessel growth by decreasing extracellular protease expression and inhibiting endothelial cell migration. Its angiostatic activity does not seem to be mediated through any of the commonly known pharmacological receptors. RETAANE blocks signals from multiple growth factors because it acts downstream and independent of the initiating angiogenic stimuli and inhibits angiogenesis subsequent to the angiogenic stimulation. Recently was discovered, that phosphodiesterase 6-delta (PDE6D) was a molecular binding partner of AA and this provided insight into the role of this drug candidate in treating glaucoma.