Beloxepin (or ADL6906), a novel dual norepinephrine reuptake inhibitor and serotonin receptor antagonist, was investigated for the treatment of the pain and Major depressive disorder, but these studies were discontinued.

Fananserin is a potential antipsychotic compound with a high affinity for both D4 and 5-HT2A receptors, and negligible affinity for D2 receptors. Fananserin has been researched for the treatment of schizophrenia. Fananserin was the first selective D4/5-HT2A antagonist to undergo clinical trials for schizophrenia. It has a high affinity for D4 (Ki 2.9 nM) and 5-HT2A (Ki 0.37 nM) receptors and is over 100-fold selective versus H1, a1 adrenergic, 5-HT1A and D2 dopamine receptors. Development of this compound was halted following phase II clinical trials due to lack of efficacy.

Licostinel (ACEA 1021) is a potent competitive antagonist at the glycine site on the N-methyl-D-aspartate (NMDA) receptor. The robust efficacy of glycine/NMDA antagonists, such as ACEA 1021, in animal model of brain ischemia, together with good safety profile in animal models and in clinical trials, suggested that this class of NMDA antagonists should have good chance of success in the clinic as neuroprotectants. The clinical trial of ACEA 1021 for stroke was discontinued, mainly due to low solubility and lack of metabolism of the drug that led to the observation of crystals in the urine of some of the patients. In vivo ACEA 1021 reduced the rate of propagation of cortical spreading depression, an effect consistent with blockade of NMDA receptors. ACEA 1021 also decreased audiogenic myoclonus in resuscitated rats following cardiac arrest, and the minimum alveolar concentration for halothane, effects which suggest a reduction of excitatory amino acid neurotransmission. ACEA 1021 crosses the blood-brain barrier and blocks the pathophysiologic consequences of NMDA receptor overstimulation. It was neuroprotective with a favorable therapeutic window in models of transient and permanent cerebral ischemia, epilepsy and pain.

Eniluracil (5-ethynyluracil, GW 776, 776C85) is a potent irreversible inhibitor of dihydropyrimidine dehydrogenase, the first enzyme in the catabolic pathway of 5-fluorouracil (5-FU), the most widely used drug in cancer chemotherapy. Eniluracil increases the oral bioavailability of 5-FU to 100%, facilitating uniform absorption and predictable toxicity. Eniluracil was being developed as a novel modulator of 5-FU for the treatment of cancer.

Piclamilast (RP 73401), is a selective PDE4 inhibitor. It is comparable to other PDE4 inhibitors for its anti-inflammatory effects. It has been investigated for its applications to the treatment of conditions such as asthma, dermatitis, rheumatoid arthritis. Emesis is the most commonly cited side effect of piclamilast.