Glutamine is a non-essential amino acid present abundantly throughout the body and is involved in many metabolic processes. It is synthesized from glutamic acid and ammonia. It is the principal carrier of nitrogen in the body and is an important energy source for many cells. Supplemental L-glutamine's possible immunomodulatory role may be accounted for in a number of ways. L-glutamine appears to play a major role in protecting the integrity of the gastrointestinal tract and, in particular, the large intestine. During catabolic states, the integrity of the intestinal mucosa may be compromised with consequent increased intestinal permeability and translocation of Gram-negative bacteria from the large intestine into the body. The demand for L-glutamine by the intestine, as well as by cells such as lymphocytes, appears to be much greater than that supplied by skeletal muscle, the major storage tissue for L-glutamine. L-glutamine is the preferred respiratory fuel for enterocytes, colonocytes and lymphocytes. Therefore, supplying supplemental L-glutamine under these conditions may do a number of things. For one, it may reverse the catabolic state by sparing skeletal muscle L-glutamine. It also may inhibit translocation of Gram-negative bacteria from the large intestine. L-glutamine helps maintain secretory IgA, which functions primarily by preventing the attachment of bacteria to mucosal cells. L-glutamine appears to be required to support the proliferation of mitogen-stimulated lymphocytes, as well as the production of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma). It is also required for the maintenance of lymphokine-activated killer cells (LAK). L-glutamine can enhance phagocytosis by neutrophils and monocytes. It can lead to an increased synthesis of glutathione in the intestine, which may also play a role in maintaining the integrity of the intestinal mucosa by ameliorating oxidative stress. The exact mechanism of the possible immunomodulatory action of supplemental L-glutamine, however, remains unclear. It is conceivable that the major effect of L-glutamine occurs at the level of the intestine. Perhaps enteral L-glutamine acts directly on intestine-associated lymphoid tissue and stimulates overall immune function by that mechanism, without passing beyond the splanchnic bed. Glutamine is used for nutritional supplementation, also for treating dietary shortage or imbalance.

Sincalide is a synthetically-prepared C-terminal octapeptide of naturally occurring hormone cholecystokinin. Sincalide causes gallbladder contraction and stimulates secretion of pancreatic enzymes, and this property of the drug is used in diagnostic purposes. It is discussed that the drug acts by binding and stimulating the CCK-A receptor which is expressed in the target tissues. FDA approved sincalide under the name KINEVAC.

EC17 (also known as Folate-FITC) is conjugate consisting of fluorescein isothiocyanate (FITC) conjugated with folate with potential antineoplastic activity. EC17 binds to folate receptors, which are overexpressed on the surfaces of many cancer cells including kidney and ovarian cancer cells. Once bound to the cancer cell through the folate moiety of the conjugate, circulating anti-fluorescein antibodies recognize and bind to the FITC moiety, resulting in antibody-dependent cellular cytotoxicity. EC17 is participating in phase II clinical trials for the treatment of patients with endometrial cancer, endometriosis, lung cancer, renal cell carcinoma. In January 2018, On Target Laboratories initiated a phase III trial to evaluate the safety and efficacy of EC17 injection for patients with ovarian cancer.

Glutaurine is formed from the amino group of taurine with the gamma-carboxy group of L-glutamic acid. It was originally discovered in the parathyroid. Evidence has been found suggesting that glutaurine plays a role in peripheral thyroid hormonal regulation. Glutaurine increases triiodothyronine (T3) levels, but does not alter thyroxine (T4) levels. Glutaurine was also shown to prevent electroconvulsive shock-induced amnesia by counteracting the shock effect on the memory consolidation phase. Other roles that have been suggested for glutaurine include roles as a mouse metabolite, a mammalian metabolite, a human metabolite, an anticonvulsant, an anxiolytic drug and a hormone.

Antineoplaston (Phenylacetylglutamine) is the amino acid acetylation product of phenylacetate (or phenylbutyrate after beta-oxidation). The chemical structure of Antineoplaston AS2-5 corresponds to phenylacetylglutamine. Two synthetic derivatives of Antineoplaston A10 were named Antineoplaston AS2-1 and AS2-5. All antineoplaston formulations were submitted for Phase I clinical studies in advanced cancer patients. The treatment was free from significant side-effects and resulted in objective response in a number of advanced cancer cases. Antineoplastons are an experimental cancer therapy developed by S.R. Burzynski, MD, PhD. Chemically, antineoplastons are a mixture of amino acid derivatives, peptides, and amino acids found in human blood and urine. The developer originally isolated antineoplastons from human blood and later found the same peptides in urine. Urine was subsequently used because it was less expensive and easier to obtain. Since 1980, antineoplastons have been synthesized from commercially available chemicals at the Burzynski Research Institute. According to the developer, antineoplastons are part of a biochemical surveillance system in the body and work as "molecular switches." For the developer, cell differentiation is the key to cancer therapy. At the molecular level, abnormal cells that are potential cancer cells need to be "switched" to normal mode. Antineoplastons are the surveillance system that directs cancer cells into normal channels of differentiation. According to statements published by the developer, people with cancer lack this surveillance system because they do not have an adequate supply of antineoplastons.

Bombesin (BN), a neuropeptide that originally was purified from the skin of the European frog (Bombina bombina). It has many biological effects including hormone release, stimulation of pancreatic enzyme secretion, gallbladder contraction and bronchoconstriction. Bombesin is a highly specific marker of neuroendocrine differentiation and thus a valuable tumor marker. It activates three different G-protein-coupled receptors known as BBR1, -2, and -3.