Phenformin is a biguanide hypoglycemic agent with actions and uses similar to those of metformin. It activates AMP-activated protein kinase (AMPK) and inhibits mTORC1 signaling. Phenformin used for the treatment of diabetes. Phenformin was removed from the U.S. market 20 years ago because of a high incidence of lactic acidosis. Risk factors for the development of lactic acidosis include renal deficiency, hepatic disease, cardiac disease, and drug interaction such as cimetidine. Phenformin exerts potential anti-neoplastic action.

Orotic acid is a minor dietary constituent. Historically it was believed to be part of the vitamin B complex and was called vitamin B13, but it is now known that it is not a vitamin and is synthesized in the body, where it arises as an intermediate in the pathway for the synthesis of pyrimidine nucleotides. Orotic acid is converted to UMP by UMP synthase, a multifunctional protein with both orotate phosphoribosyl transferase and orotidylate decarboxylase activity. The most frequently observed inborn error of pyrimidine nucleotide synthesis is a mutation of the multifunctional protein UMP synthase. As a result, plasma orotic acid accumulates to high concentrations, and increased quantities appear in the urine. Orotic acid levels are elevated in the urea cycle defects ornithine transcarbamylase (OTC) deficiency, citrullinemia and argininosuccinic acidemia, as well as the mitochondrial transport disorder hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome. Orotic acid is also elevated in hereditary orotic aciduria, or uridine monophosphate synthase deficiency, an autosomal recessive disorder characterized by megaloblastic anemia and crystalluria. In addition, orotic acid in combination with leflunomide is in the phase II of clinical trial to evaluate the clinical efficacy and safety of a combination in kidney transplant patients with high levels of Polyoma BK viruria for the purpose of preventing polyoma BK viremia and nephropathy, that could lead to kidney transplant loss from viral damage, acute rejection or both.

Citrulline (name derived from citrullus, the Latin word for watermelon, from which it was first isolated) is an amino acid. It is made from ornithine and carbamoyl phosphate in one of the central reactions in the urea cycle. It is also produced from arginine as a by-product of the reaction catalyzed by nitric oxide synthase (NOS) family. Citrulline supplements have been claimed to promote energy levels, stimulate the immune system and help detoxify ammonia (a cell toxin). Citrulline is not involved in protein synthesis. Several pharmacokinetic studies have confirmed that citrulline is efficiently absorbed when administered orally. Oral citrulline could be used to deliver arginine to the systemic circulation or as a protein anabolic agent in specific clinical situations (for example in case of malnourishment), because recent data have suggested that citrulline, although not a component of proteins, stimulates protein synthesis in skeletal muscle through the mammalian target of rapamycin signaling pathway. Citrulline is converted to L-arginine by argininosuccinate synthase. L-arginine is in turn responsible for citrulline's therapeutic effects. Many of L-arginine's activities, including its possible anti-atherogenic actions, may be accounted for by its role as the precursor to nitric oxide (NO).

Evogliptin (Suganon) is an orally bioavailable, selective dipeptidyl peptidase-4 (DPP-4; CD26 antigen) inhibitor being developed by Dong-A ST for the treatment of type 2 diabetes mellitus. Evogliptin was approved in South Korea on 2 October 2015 for blood glucose lowering in patients with type 2 diabetes mellitus inadequately controlled by diet and exercise alone or by metformin plus diet and exercise. In July 2015, Dong-A ST signed a licensing out agreement for evogliptin with Geropharm for Russia, Ukraine and Kazakhstan markets. In April 2015, Dong-A ST signed a licensing agreement with Eurofarma Laboratorios of Brazil for 17 Latin America countries including Mexico. Evogliptin is a potent DPP-4 inhibitor with a 50 % inhibitory concentration (IC50) against soluble human DPP-4 of 0.98 nmol/L and an IC50 of 1.26 nmol/L against membrane-bound human DPP-4. It displayed 6000-fold higher potency for human DPP-4 than for human DPP-8 and DPP-9, and 20,000-fold greater potency for DPP-4 than for DPP-1, DPP-2 and other closely-related enzymes. Evogliptin is effective in improving glycosylated hemoglobin (HbA1c) and fasting plasma glucose without inducing hypoglycemia events, which potentially can improve adherence and prevent complications. It is also found that evogliptin has benefits on insulin secretory and β-cell functions. Based on the current clinical data, evogliptin has a neutral effect on body weight. These attributes contribute to the clinical practice in monotherapy or in combination with other antidiabetic agents. Evogliptin was generally well tolerated in clinical trials.

Gemigliptin, an orally active, CD26 antigen (dipeptidyl peptidase IV or DPP IV) antagonist, was developed by LG Life Sciences (Seoul, Korea) and was approved by the Ministry of Food and Drug safety in June 2012 for the treatment of Type 2 diabetes mellitus. Zemiglo is the brand name of gemigliptin. The company also signed licensing agreement with multinational pharmaceutical companies including Sanofi (Paris, France), and at present gemigliptin is approved in India, Columbia, Costa Rica, Panama, Ecuador and a few other countries. Registration studies are currently ongoing in several countries including Russia, Mexico and Thailand. Various studies have proven the efficacy and safety of gemigliptin for the treatment of T2DM, both as monotherapy as well as in combination with other anti-diabetic drugs. Gemigliptin binds to the S1, S2, and S2 extensive subsites of the DPP-4 enzyme. The piperidinone group of gemigliptin binds to the S1 subsite, where the upside F atom on the piperidin ring forms a hydrogen bond with the side chain of Tyr631 and the downside F atom makes a hydrophobic interaction with the side chain of Tyr666 and Tyr662. In addition, the key interaction occurs between the CF3 groups on the pyrimidino piperidine and the S2 extensive subsite of the DPP-4 substrate, which enhances the potency of the drug and increases its selectivity as well. Gemigliptin is a reversible and competitive inhibitor of DPP-4 enzyme with a Ki value of 7.25 ± 0.67 nM. It acts as a long-acting DPP-4 inhibitor which inhibits DPP-4 in a dose-dependent manner. In addition, it showed at least >23,000 fold selectivity for proteases such as DPP-8, DPP-9, and fibroblast activating protein – α. By preventing degradation of GLP-1 by DPP-4 inhibition, it increases insulin secretion, reduces glucagon secretion, decreases HbA1c, and prevents β-cell damage. Gemigliptin has also been investigated for the treatment of cancer and cisplatin adverse reaction.

Vildagliptin, previously identified as LAF237, is a new oral anti-hyperglycemic agent (anti-diabetic drug) of the new dipeptidyl peptidase-4 (DPP-4) inhibitor class of drugs. Vildagliptin inhibits the inactivation of GLP-1 and GIP by DPP-4, allowing GLP-1 and GIP to potentiate the secretion of insulin in the beta cells and suppress glucaon release by the alpha cells of the islets of Langerhans in the pancreas. It is currently in clinical trials in the U.S. and has been shown to reduce hyperglycemia in type 2 diabetes mellitus. While the drug is still not approved for use in the US, it was approved in Feb 2008 by European Medicines Agency for use within the EU and is listed on the Australian PBS with certain restrictions. Vildagliptin is marketed under the trade names Galvus, Zomelis.