Ezlopitant (CJ-11974) is a non-peptide neurokinin-1 receptor antagonist. Pfizer was developing ezlopitant for the potential treatment of irritable bowel syndrome and chemotherapy-induced emesis. Development of ezlopitant has been discontinued.

Pfizer was developing UK-396,082, an imidazole-propionic acid, as an oral treatment for thrombosis and pulmonary fibrosis. UK-396,082 is a potent and selective inhibitor of activated thrombin-activatable fibrinolysis inhibitor (activated TAFI; TAFIa) with Ki of 10 nM. UK-396,082 displays excellent selectivity over plasma carboxypeptidase N (>1,000-fold); exhibits antithrombotic efficacy in a rabbit model of venous thrombosis, yet has no effect on surgical bleeding in the rabbit; possesses excellent preclinical and clinical pharmacokinetic profile. UK-396,082 showed potential for the treatment of thrombosis and other fibrin-dependent diseases in humans, however its development was discontinued.

Gosogliptin (PF-734200) is a compound developed for treatment of type II diabetes and has been approved for use in Russia. It is a selective dipeptidyl peptidase 4 (DPP-4) inhibitor, with hypoglycemic activity. The drug is safe and well tolerated at all doses tested when added to metformin (a diabetes drug), and safely and effectively lowered HbA (1c) in subjects receiving metformin. A phase 3 study to study the safety and efficacy of gosogliptin has been completed. Gosogliptin has also been studied as potential drug for the treatment of renal insufficiency.

Merafloxacin (CI 934) is a quinolone antibacterial. It is an inhibitor of Type II DNA topoisomerase. It demonstrated excellent activity against gram-positive organisms, including Corynebacterium sp. In addition, although the activity of merafloxacin against gram-negative bacilli was less than that reported for similar agents, it was comparable to that of aminoglycosidic aminocyclitol antibiotics. Merafloxacin development has been discontinued.

Atagabalin, also known as PD-0200390, was studied in phase II clinical trials in patients with primary insomnia, but this trial was discontinued because of the unsatisfied results. Atagabalin is a ligand to the α(2)δ subunit of voltage-sensitive calcium channels

Filibuvir (PF-868554), being developed by Pfizer, is an orally administered, non-nucleoside inhibitor of the HCV NS5B RNA-dependent RNA polymerase for the potential treatment of chronic hepatitis C (HCV) infection. Filibuvir is a potent and specific inhibitor of the virally encoded NS5B polymerase, and inhibited genotype 1 sub genomic HCV replication in the cell-based replicon system. In phase I and a IIa clinical trial in treatment-naïve patients infected with genotype 1 HCV, filibuvir monotherapy or in combination with pegylated IFNα2a/ribavirin (the standard of care [SoC] for HCV infection) for up to 4 weeks significantly reduced HCV RNA levels compared with placebo or SoC alone. However, company stopped development of the drug and the decision to halt development of the non-nucleoside polymerase inhibitor, which was in mid-stage testing, was not related to any safety issues.

Teloxantrone (also known as DuP 937) was developed as an anthrapyrazole intercalator that inhibits DNA synthesis. Teloxantrone interacts with topoisomerase II, thereby inhibiting DNA replication and repair, as well as RNA and protein synthesis. The drug participated in phase II clinical trials in colorectal carcinoma, in non-small cell lung cancer, in metastatic malignant melanoma. However, these studied apparently were discontinued.

UK-432097 is a selective adenosine A2a agonist which was in development with Pfizer as an inhaled treatment for asthma and chronic obstructive pulmonary disease. UK-432097 had been in phase II clinical trials by Pfizer for the treatment of chronic obstructive pulmonary disease (COPD). However, this study was terminated prematurely due to futility based on results of interim analysis.

Esreboxetine (PNU-165442G) is the (S,S)-(+)-enantiomer of antidepressant reboxetine, a selective norepinephrine reuptake inhibitor. The (S,S)-enantiomer is a more potent inhibitor of norepinephrine transporter than (R,R)-enantiomer. Esreboxetine was being developed by Pfizer, primarily for the treatment of fibromyalgia.

Zaltidine (CP-57,361) is a guanidinothiazolylimidazole compound which is a highly specific H2-receptor antagonist. It potently inhibits gastric acid secretion. Zaltidine appears to be an effective treatment of duodenal ulcer in human studies. However, the incidence of hepatic damage (8%) seems higher than with commonly used H2-receptor antagonists.