Ipamorelin is a new and potent synthetic pentapeptide which has distinct and specific growth hormone (GH)-releasing properties. Ipamorelin mimics ghrelin and binds to the ghrelin receptor (or GH secretagogue receptor, GHSR) in the brain, thereby selectively stimulating the release of GH from the pituitary gland. This results in increased plasma GH levels, which would affect many biological processes. Besides its presence in the brain, GHSR can also be found in the gastrointestinal tract, heart, lung, liver, kidney, pancreas, adipose tissue and immune cells. Unlike other GH releasing peptides, ipamorelin only stimulates GH release in a manner very similar to that of growth hormone releasing hormone.

Ibutamoren (L-163,191 MK-0677) is a spiropiperidine agonist of the ghrelin receptor and a growth hormone secretagogue. Ibutamoren mimics the actions of growth hormone releasing peptide-6 to increase serum levels of serum insulin-like growth factor-I (IGF-I). Orally active Ibutamoren was being developed by Merck & Co. for a variety of indications, including fibromyalgia, muscle wasting/weakness in patients with chronic kidney disease, Alzheimer's disease and fractures.However, there has been no recent development reported or development has been discontinued for these indications.

Anamorelin is a first-in-class, orally active ghrelin receptor agonist that binds and stimulates the growth hormone secretagogue receptor centrally, thereby mimicking the appetite-enhancing and anabolic effects of ghrelin. Anamorelin is under development by Helsinn Therapeutics for the treatment of cancer cachexia and anorexia. Anamorelin has completed phase III clinical trials for the treatment of cancer cachexia and anorexia associated with non-small-cell lung carcinoma. Results of the studies were positive, and the drug is now in preregistration with the European Medicines Agency.

BAY85-8102 (widely known as (18)F-DPA-714) is a specific radioligand for the translocator protein (TSPO). TSPO, formerly known as the peripheral benzodiazepine receptor, is dramatically upregulated under pathologic conditions. BAY85-8102 in combination with positron emission tomography imaging participated in phase I clinical trials for investigation of neuroinflammation in Alzheimer's patients. However, this study was terminated early. Clinical pharmacology/efficacy parameters planned in the protocol were not evaluated at the end of the study