Nanterinone [UK 61260], a phosphodiesterase III inhibitor, was undergoing II evaluation with Pfizer in the US for the treatment of heart failure. Nanterinone is a positive inotropic and balanced-type vasodilating drug, only partially based on phosphodiesterase III inhibition. Preliminary data from controlled studies suggest satisfactory long-term efficacy and safety.

Elzasonan (CP 448187) is a serotonin 1B/1D receptor antagonist. Elzasonan was primarily metabolized via oxidative N‐demethylation, N‐oxidation, and aryl hydroxylation. Pfizer was developing elzasonan for the treatment of anxiety and affective disorders however development has been discontinued.

Pamaqueside, an 11-ketotigogenin cellobioside was developed as a cholesterol absorption inhibitor for the treatment of hypercholesterolemia. This drug participated in phase III clinical trial; however, information about the further development of this drug is not available.

Atizoram (CP-80633) is a phosphodiesterase IV inhibitor with bronchodilatory and antiinflammatory properties. It was in phase II trials with Pfizer in the US for the treatment of asthma, atopic dermatitis and psoriasis. Development of atizoram has been discontinued in the asthma indication and no recent development has been reported for the other indications. CP-80633 inhibits PDE4 isozymes (human lung IC50 = 1.27 uM) in the absence of effects on PDE1, PDE2, PDE3 and PDE5 isozymes (IC50 > 100 uM). It exhibits no significant selectivity for any single cloned PDE4A, B, C or D isoform.

Tiqueside is the synthetic spirostane-based steroid glycoside. It precipitates cholesterol from micellar solution in vitro and reduces plasma cholesterol absorption in rats through a mechanism that is currently thought to be independent of either association of the saponin with the intestinal mucosal surface or absorption of the saponin molecule. As a consequence of this inhibition, tiqueside has been shown to reduce plasma cholesterol concentrations in cynomolgus monkeys. Inhibition of cholesterol absorption by tiqueside produces profound effects on cholesterol metabolism without affecting bile acid metabolism, and these changes lead to reductions primarily in plasma non-HDL cholesterol concentrations. Tiqueside produced a dose-dependent reduction in plasma LDL cholesterol levels in the hypercholesterolemic patients. In the mechanistic study, it decreased fractional cholesterol absorption rates and increased fecal neutral sterol excretion rates, changes associated with trends toward lower LDL cholesterol levels. Other lipoprotein levels were unaffected, as were fecal fat and bile acid excretion and fat-soluble vitamin absorption. Thus tiquesidedose-dependently inhibits cholesterol absorption in humans, resulting in a reduction in serum LDL cholesterol levels.

PF-2545920 is an orally-active phosphodiesterase 10A (PDE10A) inhibitor originated by Pfizer, for the treatment of Huntington's disease. PF-2545920 was originally developed by Pfizer for the treatment of schizophrenia. But later clinical studies for Schizophrenia were discontinued. PF-2545920 is a potent and selective PDE10A inhibitor with IC50 of 0.37 nM, with >1000-fold selectivity over the PDE. PF-2545920 is active in a range of antipsychotic models, antagonizing apomorphine-induced climbing in mice, inhibiting conditioned avoidance responding in both rats and mice, and blocking N-methyl-D-aspartate antagonist-induced deficits in prepulse inhibition of acoustic startle response in rats, while improving baseline sensory gating in mice.

Dazmegrel [UK 38485] is a thromboxane synthetase inhibitor which was undergoing development in the treatment of thrombosis, ischaemic heart disease, arrhythmias and asthma. Pfizer were conducting phase II studies in Denmark and the UK, phase I studies in Germany and Italy, and preclinical studies in France. Later this research was discontinued.

UK-390957 is a selective serotonin reuptake inhibitor (SSRI) that was in phase II/III development in the USA, European Union and other territories with Pfizer, for the treatment of Premature ejaculation. UK-390957 represented a major development in sexual medicine, and offered patients the convenience of on-demand dosing, significant improvements in IELT, ejaculatory control, and sexual satisfaction with minimal adverse effects. However development of UK-390957 was discontinued.

Tolimidone, Lyn protein-tyrosine kinase stimulant, is in phase II clinical by Melior Discovery and Bukwang for the treatment of type 2 diabetes. It is also in phase II clinical by Pfizer for the treatment of ulcer. However, this research has been discontinued.

INCB-8761 (PF-4136309) is an orally available human chemokine receptor 2 (CCR2) antagonist with potential immunomodulating and antineoplastic activities. Upon oral administration, CCR2 antagonist INCB-8761 specifically binds to CCR2 and prevents binding of the endothelium-derived chemokine ligand CLL2 (monocyte chemoattractant protein-1 or MCP1) to its receptor CCR2, which may result in inhibition of CCR2 activation and signal transduction. This may inhibit inflammatory processes as well as angiogenesis, tumor cell migration, and tumor cell proliferation. INCB-8761 is a potent CCR2 antagonist with high selectivity, weak hERG activity, high free fraction in protein binding, and an excellent in vitro and in vivo ADMET (ADME and toxicology) profile. INCB-8761 entered human clinical trials. It is in phase I/II clinical trials for pancreatic cancer.