Palovarotene (R-667, RO-3300074) was developed by Roche Holding AG as a selective retinoic acid receptor gamma agonist for the treatment of emphysema. Phase I clinical trials of palovarotene in patients with emphysema demonstrated that the drug is well tolerated, with improvements observed in markers of emphysema progression. Unlike all-trans retinoic acid, the pharmacokinetic profile of palovarotene appears to be dose-proportional. However, those studies were discontinued. Palovarotene is also being investigated in phase II of the clinical trial in the treatment of Fibrodysplasia Ossificans Progressiva (FOP). Palovarotene received Fast Track designation from the U.S. Food and Drug Administration (FDA) and orphan designations for the treatment of FOP from both the FDA and the European Medicines Agency (EMA).

Tauroursodeoxycholic acid (TUDCA) is an endogenous hydrophilic bile acid used clinically to treat certain liver diseases. It is approved in Italy and Turkey for the treatment of cholesterol gallstones and is an investigational drug in China, Unites States, and Italy. Tauroursodeoxycholic acid is being investigated for use in several conditions such as Primary Biliary Cirrhosis (PBC), insulin resistance, amyloidosis, Cystic Fibrosis, Cholestasis, and Amyotrophic Lateral Sclerosis. Tauroursodeoxycholate (TUDC) promote choleresis by triggering the insertion of transport proteins for bile acids into the canalicular and basolateral membranes of hepatocytes. In addition, Tauroursodeoxycholate exerts hepatoprotective and anti-apoptotic effects, can counteract the action of toxic bile acids and reduce endoplasmic reticulum stress. Tauroursodeoxycholate can also initiate the differentiation of multipotent mesenchymal stem cells (MSC) including hepatic stellate cells and promote their development into hepatocyte-like cells. Although the hepatoprotective and choleretic action of TUDC is empirically used in clinical medicine since decades, the underlying molecular mechanisms remained largely unclear.

Fluorodopa F-18 is the amino acid analog fluorodopa (FDOPA) labeled with fluorine F 18, a positron-emitting isotope. It is diagnostic PET agent, which has been used for decades in imaging the loss of dopaminergic neurons in Parkinson's disease, and more recently to detect, stage and restage neuroendocrine tumours and to search for recurrence of viable glioma tissue. Fluorodopa F-18 is able to cross the blood-brain barrier and is taken up by brain tumor cells. As uptake is higher in tumor cells, tumors may then be imaged using positron emission tomography (PET). Assessing tumor uptake of FDOPA may be beneficial for diagnosis, localization and in determining further treatment. The clinical usefulness of Fluorodopa F-18 has been evaluated and recognised in France and subsequently in several EU countries. Fluorodopa F-18 was registered in France in 2006. 6-fluoro-(18F)-L-3,4-dihydroxyphenylalanine (FDOPA) is a large, neutral amino acid that is transported into presynaptic neurons, where it is converted by the enzyme aromatic aminoacid decarboxylase [AAAD]) into fluorodopamine-(18F), which subsequently enters cathecholamine-storage vesicles. 6-fluoro(18F)-L-dopa crosses the blood-brain barrier; therefore, when injected into the blood stream, it reaches the dopaminergic cells in the brain and is used by the brain as a precursor for dopamine. This makes it possible to monitor intracerebral synthesis and uptake of dopamine by means of the positron-emitting 6-fluoro(18F)-L-3,4-dihydroxyphenylalanine (FDOPA), in conjunction with externally-placed devices suited for detection of annihilation photons, which progressively led to the most recent positron emission tomography (PET) units. Iasodopa, the commercial preparation of FDOPA that obtained a marketing authorisation in France in November 2006 (which is currently recognised by several other EU countries), is a solution for injection. The activity available at time of administration ranges from 0.1 GBq to 0.8 GBq per vial. The half-life of the radionuclide is 109.8 min with emission of positron radiation (Emax: 0.633 MeV) followed by photon annihilation radiations of 0.511 MeV.

Obeticholic acid (also known as INT-747), is a potent, orally bioavailable farnesoid X receptor (FXR) agonist. The key role of the farnesoid X receptor (FXR) as a regulator of bile and cholesterol metabolism in the liver, with preclinical data from numerous studies providing strong rationale for the advancement of FXR agonists as hepatoprotective therapeutics in chronic liver disease. Obeticholic acid is marketed under the trade name Ocaliva. Ocaliva is specifically indicated for the treatment of primary biliary cholangitis (PBC) in combination with ursodeoxycholic acid (UDCA) in adults with an inadequate response to UDCA, or as monotherapy in adults unable to tolerate UDCA.

Cholic acid is a primary bile acid synthesized from cholesterol in the liver. Endogenous bile acids including cholic acid enhance bile flow and provide the physiologic feedback inhibition of bile acid synthesis. The mechanism of action of cholic acid has not been fully established; however, it is known that cholic acid and its conjugates are endogenous ligands of the nuclear receptor, farnesoid X receptor (FXR). FXR regulates enzymes and transporters that are involved in bile acid synthesis and in the enterohepatic circulation to maintain bile acid homeostasis under normal physiologic conditions. U.S. Food and Drug Administration approved Cholbam (cholic acid) capsules, the first FDA approved treatment for pediatric and adult patients with bile acid synthesis disorders due to single enzyme defects, and for patients with peroxisomal disorders (including Zellweger spectrum disorders).

Triheptanoin (also known as C7 oil) is an investigational medical food or supplement. Triheptanoin is thought to have an anaplerotic role, meaning that it can replenish substances involved in the tricarbolic acid cycle, a pathway used by cells to produce energy, providing an alternative source of energy to the brain. It supplies the body with heptanoate which can either be oxidized to propionyl-CoA directly or is metabolized by the liver to the“C5 ketones”, β-ketopentanoate and/or β-hydroxypentanoate, which are released into the blood. After one month of triheptanoin use, the level of energy production in the brain during visual stimulation had become normal in Huntington’s patients. Triheptanoin was anticonvulsant in two chronic mouse models and increased levels of anaplerotic precursor metabolites in epileptic mouse brains. Despite the unknown mechanism of triheptanoin’s anticonvulsant action, the fact that triheptanoin has been used safely in several animals and for various metabolic diseases in children and adults should expedite the ethical and regulatory approval processes for a clinical trial in medically refractory patients with epilepsy. Triheptanoin is phase II clinical trial for the treatment of glycogen storage disease type V, Huntington's disease, Rett syndrome and amyotrophic lateral sclerosis.

Carglumic acid is a Carbamoyl Phosphate Synthetase 1 (CPS 1) allosteric modulator. CPS1 is found in the mitochondria and is the first enzyme of the urea cycle, which converts ammonia into urea. Carglumic acid acts as a replacement for NAG in NAGS deficiency patients by activating CPS1 but it does not help to regulate the urea cycle. Carglumic acid under the trade name Carbaglu indicated as adjunctive therapy for the treatment of acute hyperammonemia due to the deficiency of the hepatic enzyme N-acetylglutamate synthase (NAGS). In addition, as maintenance therapy for the treatment of chronic hyperammonemia due to the deficiency of the hepatic enzyme N-acetylglutamate synthase (NAGS). This rare genetic disorder results in elevated blood levels of ammonia, which can eventually cross the blood–brain barrier and cause neurologic problems, cerebral edema, coma, and death.

Pralatrexate (PDX or 10-propargyl-10-deazaaminopterin) is a folate analogue that is internalised by the reduced folate carrier 1 (RFC-1) protein, and polyglutamylated by the enzyme folylpolyglutamyl synthetase (FPGS), resulting in accumulation of the antifolate. Pralatrexate, a methotrexate analogue, is intended as an inhibitor of dihydrofolate reductase (DHFR), an enzyme which catalyses the reduction of dihydrofolic acid to tetrahydrofolic acid. Inhibition of DHFR leads to a depletion of intracellular reduced folate stores, thereby leading to a disruption of DNA synthesis. Preclinical studies in vitro and in models of B-cell lymphomas, T-cell lymphomas and NSCLC indicated that pralatrexate exhibited antitumor activity that was superior to the activity of other antifolates. FOLOTYN (pralatrexate injection) is indicated for the treatment of patients with relapsed or refractory peripheral T-cell lymphoma.

Vigabatrin is an anticonvulsant chemically unrelated to other anticonvulsants. Vigabatrin prevents the catabolism of GABA by irreversibly inhibiting the enzyme GABA transaminase. It is an analog of GABA, but it is not a receptor agonist. However, vigabatrin is not a potent inhibitor of GABA-T with a Ki of 10 mM. Vigabatrin increases brain concentrations of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter in the CNS, by irreversibly inhibiting enzymes that catabolize GABA (gamma-aminobutyric acid transaminase, GABA-T). Duration of action is determined by rate of GABA-T re-synthesis. Vigabatrin may also work by suppressing repetitive neuronal firing through inhibition of voltage-sensitive sodium channels. Although administered as a racemic mixture, only the S(+) enantiomer is pharmacologically active. Vigabatrin is sold under the trade name SABRIL, it is indicated as adjunctive therapy for adults and pediatric patients 10 years of age and older with refractory complex partial seizures who have inadequately responded to several alternative treatments and for whom the potential benefits outweigh the risk of vision loss.

Febuxostat (ULORIC) is a novel, xanthine oxidase/dehydrogenase (XO/XDH) inhibitor being developed by Teijin, TAP Pharmaceuticals, and Ipsen for the treatment of gout. The currently available XO inhibitor, allopurinol, has been associated with serious instances of severe hypersensitivity, in some cases leading to fatalities. There is some suggestion that febuxostat is less prone to excacerbate systemic inflammatory events in animal studies. Febuxostat, a xanthine oxidase inhibitor, achieves its therapeutic effect by decreasing serum uric acid. Febuxostat is not expected to inhibit other enzymes involved in purine and pyrimidine synthesis and metabolism at therapeutic concentrations. Febuxostat is used for the treatment of hyperuricemia in patients with gout.