Piriprost (U-60, 257) is a structural analog of prostaglandin I2 (PGI2) with low IP receptor-mediated activity. It inhibits 5-LO (5-lipoxygenase). Piriprost inhibits the release of histamine and leukotrienes, implicating its role in inflammation and allergic responses. However, it was shown, that piriprost did not influence the airway responses after allergen in asthma. Nevertheless, even more, the drug was irritant to the respiratory tract than was placebo.

Yohimbinic acid, also known as yohimbic acid is an indole alkaloid, which was isolated from dried roots of Rauwolfia serpentina. Yohimbinic acid is a potent inhibitor of a human DNA Topoisomerase I and can inhibit cancer cells growth.

Safingol, the synthetic L-threo-stereoisomer of endogenous (D-erythro-) sphinganine, is an inhibitor of protein kinase C and sphingosine kinase in vitro, and in some cell types has been implicated in ceramide generation and induction of apoptosis. Safingol inhibits enzymatic activity and 3H-phorbol dibutyrate binding of purified rat brain PKC (IC50 = 37.5 uM and 31uM, respectively). Inhibits human PKCα, the major overexpressed isoenzyme in MCF-7 DOXR cells (IC50 = 40 uM). Safingol enhances the cytotoxic effect of the chemotherapeutic agent Mitomycin C (MMC) in gastric cancer cells by promoting drug-induced apoptosis. Safingol is an inhibitor of SphK (Sphingosine kinase). Safingol has been shown to act synergistically with other chemotherapeutic agents and may potentiate chemotherapy drug-induced apoptosis in vitro and in vivo.

Orazipone (also known as OR-1384 or OR-1958) was developed by Orion Company as thiol-modulating, anti-inflammatory agent. Orazipone inhibits activation of inflammatory transcription factors nuclear factor-kappa B and signal transducer and activator of transcription 1 and decreases inducible nitric-oxide synthase expression and nitric oxide production in response to inflammatory stimuli. This drug had completed phase I clinical studies in Finland for possible use in inflammatory bowel disease, asthma, and chronic obstructive pulmonary disease. In addition, orazipone was studied for the treatment of Crohn's disease. However, all these studies were discontinued.

OPINIAZIDE (also known as saluzid) was used for the treatment of meningeal tuberculosis in adults and in children. Information about the current use of this drug is not available.

Omidoline, an antiparkinsonian agent that has never been marketed. Information about the current use of this drug is not available.

Pidobenzone, an amino acid ester of hydroquinone, is a second-generation worldwide patented depigmenting agent, reliable and free of collateral risks. Pidobenzone 4% lipogel represents a useful, reliable, and safe treatment of the different types of melasma. No data are available regarding the efficacy of pidobenzone as monotherapy for solar lentigines. The combination of cryotherapy and pidobenzone 4% has been found to be the most useful treatment of solar lentigines and the prevention of eventual posttreatment hyperchromia.

Piflutixol is a thioxanthene neuroleptic which combines a very potent dopamine antagonistic effect with a potent effect in tests for sedative properties. It was found to have a very strong antagonistic effect against stereotypies induced by dopamine agonists in mice, rats and dogs as well as against apomorphine induced vomiting in dogs. This indicates that piflutixol must be considered as one of the most potent dopamine receptor blocking agents. Piflutixol seems to be the hitherto most potent inhibitor of dopamine-stimulated adenylate cyclase. There was a linear relationship between D-1 dopamine receptor occupation by [3H]piflutixol and inhibition of dopamine sensitive adenylate cyclase. Piflutixol markedly antagonizes the effect of noradrenaline, 5-HT and to some extent histamine, whereas the affinity for muscarinic receptors was rather weak. Piflutixol has a high affinity for dopamine structures within the brain. It is a compound with a very long duration of action.

CPI-1189 is a synthetic benzamide with antioxidant properties that blocks tumor necrosis factor-alpha (TNFalpha) effects in animal models. It has neuroprotective properties in model systems for HIV-associated neurotoxicity and thus is a candidate for neuroprotective therapy in humans with HIV-associated CNS disease. CPI-1189 was at the phase II stage of clinical development for the treatment of dementia associated with Parkinson's disease and AIDS Dementia Complex, however, development has been discontinued.