Pexiganan is a 22-amino-acid synthetic cationic peptide. It is an analog of magainin 2, which is a host defense peptide isolated from frog skin. The drug is thought to act by disturbing the permeability of the cell membrane or cell wall. Pexiganan exhibited in vitro broad-spectrum antibacterial activity when it was tested against 3,109 clinical isolates of gram-positive and gram-negative, anaerobic and aerobic bacteria. It is currently in phase 3 clinical trials as a topical antimicrobial agent for the treatment of mild infections associated with diabetic foot ulcers. In vitro data for pexiganan acetate suggest that the drug does have hemolytic activity at concentrations relevant for antibacterial activity. In association with tigecycline, pexiganan administration could overcome antibiotic resistance and increase the effectiveness of treatment against P. aeruginosa sepsis.

Avitriptan (BMS-180048), a new 5-HT 1B/1D receptor agonist, has been studied in phase II clinical trials in patients with migraine headaches. Later experiments have confirmed antimigraine activity together with coronary side-effect potential that is why further studies were discontinued.

Sibrafiban (G-7453) is the orally administered, nonpeptide, double-prodrug of Ro 44-3888 which is a selective glycoprotein IIb/IIIa receptor antagonist. Sibrafiban is a double prodrug that undergoes bioconversion to the inactive prodrug Ro 48-3656 and to the active IIb/IIIa antagonist, Ro 44-3888, after oral administration. Sibrafiban was undergoing clinical trials for secondary prevention of cardiac events in patients stabilised after acute coronary syndromes. Sibrafiban has been shown to have comparable efficacy to aspirin in preventing recurrent ischemic events in patients suffering from acute coronary syndromes. Sibrafiban was under development by Genentech and Hoffmann-La Roche, and in phase III trials as an antithrombotic. The development of sibrafiban was discontinued in 1999 following unfavorable Phase III efficacy data.

Nepicastat (SYN-117) is a potent and selective inhibitor of dopamine-β-hydroxylase. This compound in Phase 2 of clinical trial for the treatment cocaine addiction and posttraumatic stress disorder.

Biricodar (also known as VX-710) was developed by Vertex as a chemosensitizing agent designed to restore the effectiveness of chemotherapeutic agents in tumor multidrug resistance. The phase II trials had commenced for biricodar, in combination with chemotherapy, for five common cancer indications: breast, ovarian, soft-tissue sarcomas, small cell lung cancer, and prostate cancer. In spite of completed trials, development of biricodar was discontinued because of the adverse effects.

Ibutamoren (L-163,191 MK-0677) is a spiropiperidine agonist of the ghrelin receptor and a growth hormone secretagogue. Ibutamoren mimics the actions of growth hormone releasing peptide-6 to increase serum levels of serum insulin-like growth factor-I (IGF-I). Orally active Ibutamoren was being developed by Merck & Co. for a variety of indications, including fibromyalgia, muscle wasting/weakness in patients with chronic kidney disease, Alzheimer's disease and fractures.However, there has been no recent development reported or development has been discontinued for these indications.

Moxilubant is an orally active leukotriene B4 antagonist patented by Ciba-Geigy A.-G. and studied for psoriasis, rheumatoid arthritis, and chronic obstructive pulmonary disease treatment. Moxilubant inhibits LTB4 signaling with a potency of 2–4 nM. In a phase 1 study in 10 healthy volunteers, Moxilubant was administered orally once or twice daily for 7 days at doses ranging from 100 to 500 mg. At dose levels of 150 mg and above, LTB4 pathway inhibition reached at least 75%. At doses of 300 mg and above, pathway inhibition reached 100%. A Phase 2 study was conducted in 24 patients with COPD treated with 240 mg/day Moxilubant for 4 weeks. In this study, there were no changes in sputum cell counts or biomarkers or in spirometry measures, even though plasma levels of Moxilubant were sufficient to significantly reduce pathway signaling.

Roxifiban (also known as DMP754), a potent antiplatelet agent in inhibiting platelet aggregation, and has a high specificity and affinity for human platelet glycoprotein IIb/IIIa complex (GPIIb/IIIa) receptors. Roxifiban participated in clinical trials phase III for the treatment of peripheral arterial disorders. This drug was also well tolerated in patients with chronic stable angina pectoris and was studied in the treatment of heparin-induced thrombocytopenia, and thrombosis. However, the development of this drug appears to have been discontinued.

Phencyclidine is an illegal, hallucinogenic drug that was initially used as an anesthetic agent in the 1950s and early 1960s, but was then withdrawn in 1965 because of dissociative hallucinogenic effects that were often disturbing and sometimes severe and prolonged. Phencyclidine is a noncompetitive NMDA (N-methyl-D-aspartate) receptor antagonist and glutamate receptor antagonist, but also interacts with other receptor sites, and may have effects with dopamine, opioid and nicotinic receptors. Phencyclidine disrupts the functioning of receptors for the neurotransmitter glutamate, which plays a major role in the perception of pain as well as in learning, memory, and emotion. It also influences the actions of the neurotransmitter dopamine, which causes the euphoria associated with drug use. Phencyclidine overdose deaths may occur after taking a large dose, though many phencyclidine related deaths result from delusions and other psychological consequences of the drug’s use. There have been reports of death due to accidental drowning, leaping from high places, and motor vehicle accidents in addition to violent episodes of self-mutilation, suicides, and homicides.