Coluracetam (code name BCI-540; formerly MKC-231) is a nootropic agent of the racetam family. It was initially developed and tested by the Mitsubishi Tanabe Pharma Corporation for Alzheimer's disease. After the drug failed to reach endpoints in its clinical trials it was in-licensed by BrainCells Inc for investigations into major depressive disorder (MDD). Like most racetam compounds, Coluracetam increases choline uptake, but it also increases uptake in damaged neurons. Specifically, Coluracetam interacts with the HACU process, which is responsible for absorbing choline into the neurons. This increased uptake occurs during the Acetylcholine synthesis process. Since Coluracetam improves choline preservation during this process, a larger amount is converted into Acetylcholine. This results in increased memory, attention and alertness. It is important to note here, that these benefits were only seen in subjects with previously impaired neurons, not in subjects with normally functioning neurons. Coluracetam is also shown to improve AMPA potentiation, which is a process that triggers cognitive function and alertness. Although Coluracetam interacts with choline transporters as well, there isn’t enough evidence to explain why or how this interaction occurs, or what occurs after the interaction. Coluracetam has been in phase II clinical trials for the treatment of major depression and anxiety. However, this research has been discontinued.

Etazolate (EHT-0202) is a selective, positive GABAA receptor modulator has completed phase II clinical trials in patients with Alzheimer's disease. It is also a selective phosphodiesterase-4 inhibitor that is specific for cAMP. Etazolate showed anxiolytic and antidepressant activity and could be useful in managing post-traumatic stress disorder.

Azeliragon is an orally bioavailable small molecule that inhibits the receptor for advanced glycation endproducts (RAGE). RAGE has been proposed to contribute to Alzheimer's disease pathology by promoting vascular leakage, promoting influx of peripheral amyloid beta into brain, mediating amyloid beta induced oxidative stress, mediating AGE induced hyperphosphorylation of tau and amyloid beta mediated neuronal death. Azeliragon is in Phase III clinical trial for the treatment of mild Alzheimer's disease.

Tarenflurbil (Flurizan or R-flurbiprofen) is the single enantiomer of the racemate NSAID flurbiprofen. Tarenflurbil is a first in class, selective amyloid-beta42 (A42) lowering agent (SALA), which acts by modulating the activity of gamma-secretase, an enzyme that converts amyloid precursor protein to amyloid-beta. The reduction of A42 may prevent the development of the amyloid plaques thought to be a key pathological process associated with Alzheimer’s disease. For several years, research and trials for the drug were conducted by Myriad Genetics, to investigate its potential as a treatment for Alzheimer's disease. In a brief statement issued June 30, Myriad Genetics reports that tarenflurbil (Flurizan) failed to have a significant effect in a phase 3 trial of patients with mild Alzheimer's disease (AD). The failure of Flurizan™ is generally attributed to its insufficient pharmacodynamics, i.e., inadequate ability to penetrate the brain and engage its target protein at doses sufficient to yield an effect. Two additional Phase 3 trials were terminated and further development of Flurizan™ was discontinued. Separate clinical development of Flurizan™ for prostate cancer has also been discontinued following negative Phase 2 results. Tarenflurbil activates c-Jun N terminal kinase, increases AP-1 binding to DNA, and downregulates cyclin D1 expression, resulting in the arrest of tumour cells in the G1 phase of the cell cycle and apoptosis. This agent also affects the expression of nuclear factor kappa B, a rapid response transcription factor that stimulates the immune response to tumour cells. Tarenflurbil does not inhibit the enzyme cyclooxygenase. The Fraunhofer Institute for Molecular Biology and Applied Ecology is currently developing tarenflurbil for the treatment of relapsing, remitting multiple sclerosis.

Ensaculin is related to naturally occurring benzopyranones like scoparone. The compound is a potent functional antagonist of excitatory amino acid-induced convulsions and mortality. In receptor-binding studies, Ensaculin showed high affinity to dopaminergic (D2, D3), serotoninergic (5-HT1A, 5-HT7), and adrenergic (A1a, A1b) receptors in the nanomolar range. Ensaculin antagonizes NMDA responses in a voltage-dependent manner. Various studies support the notion that this compound could indeed have a broad range of nootropic properties. Although few patients presented postural hypotension and dizziness after receiving ensaculin in phase I clinical trials, this drug candidate was further discontinued in phase III due to potential side effects.

Xanomeline (LY-246,708) is an orthosteric muscarinic acetylcholine receptor (mAChR) agonist, often referred to as M1/M4-preferring. It is also known to act as a M5 receptor antagonist. Xanomeline was studied in clinical trials phase I in schizophrenia. In Phase II clinical trials in Alzheimer’s patients, xanomeline significantly improved several measures of cognitive function, yet produced unwanted side effects that limited patient compliance. The side effects seem to be associated with rapid metabolism of the alkyloxy side chain following oral administration, resulting in a nonselective, yet active compound with limited therapeutic utility. Despite a second Phase II clinical trial with a patch formulation, the liabilities of xanomeline still outweigh its benefits.

Conessine is a plant steroid alkaloid that acts as a potent and specific antagonist of histamine H3 receptors. Conessine displayed high affinity at both rat and human H3 receptors (pKi = 7.61 and 8.27) and generally high selectivity against other sites, including histamine receptors H1, H2, and H4. Conessine was found to efficiently penetrate the CNS and reach very high brain concentrations. Although the very slow CNS clearance and strong binding to adrenergic receptors discouraged focus on conessine itself for further development, its potency and novel steroid-based skeleton motivated further chemical investigation. Modification based on introducing diversity at the 3-nitrogen position generated a new series of H3 antagonists with higher in vitro potency, improved target selectivity, and more favorable drug-like properties. Conessine also has high affinity for the adrenergic receptors. Conessine has being shown to possess anti-malarial activity. In India conessine finds therapeutic use for treatment of dysentery and helminthic disorders.

Tesofensine (also known as NS-2330) is a novel triple monoamine reuptake inhibitor with intrinsic inhibitory activity on norepinephrine (NE), serotonin (5-HT), and dopamine (DA) transporter function. It was development by NeuroSearch as a potential therapy for Alzheimer's disease (AD) and Parkinson's diseases, but these efforts have been discontinued. In phase II clinical trials with tesofensine in obese individuals, dose-related reductions in body weight, body fat and waist circumference, as well as improvements in other obesity-related endocrine factors were observed and the FDA recently endorsed the phase III trial program for this agent.

Pozanicline is an alpha4-beta2 neuronal nicotinic receptor partial agonist. It had been in phase II clinical trials for the treatment of attention hyperactivity disorder and Alzheimer’s disease. It was tested for the treatment of schizophrenia too. All these studies were discontinued. Modulation of hippocampal learning and memory using Pozanicline in animal model was effective as novel therapeutic strategies for nicotine addiction. However future clinical trial was terminated.

Alvameline is a partial agonist of the M1 mAChR that also displays M2/M3 antagonist effects. It readily crosses the blood-brain barrier. It has an effect profile that makes it of interest to test its ability to counteract bladder overactivity in humans. Behaviorally, alvameline has been shown to significantly improve Morris water maze (MWM) performance in both young and ageimpaired rats. It failed to improve cognition in patients with mild to moderate Alzheimer's disease.