Smilagenin (also known as PYM50028 and Cogane) is a constituent of Jamaican sarsaparilla (Smilax ornata) and is a neuroprotectant that has been evaluated in Phase II clinical trials in Parkinson's disease and Alzheimer's disease. On 27 September 2011, the European Commission to Phytopharm plc, United Kingdom, granted orphan designation for smilagenin for the treatment of amyotrophic lateral sclerosis. The details of the mechanism of action of smilagenin are incomplete but involve the upregulation of neurotrophic factors including Glial cell line-derived neurotrophic factor and brain-derived neurotrophic factor.

Velusetrag (TD-5108) is a potent, selective high intrinsic activity serotonin 5-HT(4) receptor agonist. Velusetrag has achieved proof-of-concept in patients with chronic idiopathic constipation and was on phase II of clinical trial for the treatment of Alzheimer's disease and constipation, when studies were discontinued. In addition, velusetrag is on the phase II of clinical trial for the treatment of gastroparesis.

PF-03654746 is a potent, selective antagonist of the human H3 receptor, developed by Pfizer. It was in the clinical trial phase II for the treatment of excessive daytime sleepiness (EDS) associated with narcolepsy, Tourette syndrome as well as potential anti-allergy applications and in phase I of clinical trial for the treatment of Schizophrenia and Alzheimer's disease, but these investigations were discontinued.

VX-745 (Neflamapimod) is a brain-penetrant highly selective, orally bioavailable drug that inhibits the intracellular enzyme p38 mitogen-activated protein kinase alpha (MAPKa). It is currently in phase 2 clinical studies in patients with early Alzheimer's disease. The targeting of p38 MAPK by VX-745 was associated with the suppression of the release of inflammatory mediators, including interleukin (IL)-1β and tumor necrosis factor (TNF)α, known to be implicated in exacerbating the pathophysiology of rheumatoid arthritis (RA). The drug was in phase II of the clinical trial for RA, but that studies were discontinued.

Bryostatin 1 is a macrocyclic lactone which can be isolated from the marine bryozoan, Bugula neritina. The effects of bryostatin 1 are attributed to its ability to selectively modulate the activity of two of the three subgroups of protein kinase C (PKC) isozymes. PKC isozymes are divided into three subgroups which differ in their molecular structures and co-factor requirements: classical PKC (cPKC), novel PKC (nPKC), and atypical PKC (aPKC). Bryostatin-1 modulates nPKC activity independent of a Ca2+ signaling. It activates cPKC only when associated with Ca2+ signaling. And, aPKC activity is not sensitive to bryostatin-1 administration. Ca2+ signals play an important role in synaptic transmission and information processing which creates a biological environment where Bryostatin-1 possesses a unique action profile. Bryostatin-1 will not affect cPKC activity in neurons which are not functioning as an active part of the signaling processing circuit with significant Ca2+influx and intracellular Ca2+ release. Bryostatin 1 is in phase II clinical trials for investigation as an anticancer agent; specifically for treatment of metastatic or recurrent head and neck cancer, ovarian epithelial cancer that has not responded to previous chemotherapy, and myelodysplastic syndrome. Bryostatin 1 has also generated interest as an investigational compound for the treatment of Alzheimer's disease.

CX 516, a compound synthesized by Cortex Pharmaceuticals using Ampakine® technology licensed from the University of California, was in clinical investigations for the treatment of Alzheimer's disease, schizophrenia, fragile X syndrome and autism, and sleep disorders, however, development of this drug candidate has been discontinued. CX 516 had an extremely short halflife in humans, very low potency and failed to show any benefits in phase II studies. The compound did have a good safety profile, reducing concerns about the toxicity of excess glutamate. Cortex subsequently terminated clinical development of CX 516.

Tenilsetam (CAS 997: ( /-)-3-(2-thienyl)-2-piperazinone), a cognition-enhancing drug successfully used for the treatment of patients suffering from Alzheimer's disease. According to the mechanism proposed, it inhibits advanced glycation end-product (AGE) formation. The beneficial effect of tenilsetam in Alzheimer's disease could come from the interference with AGE-derived crosslinking of amyloid plaques and a decreased inflammatory response to diminished activation of phagocytosing microglia. In addition was shown, that the long-term treatment with tenilsetam inhibited the formation of acellular capillaries without correcting pericyte loss. Was suggested that tenilsetam could be useful for the treatment of early diabetic retinopathy, but then these studies were discontinued.

Nefiracetam is a cyclic derivative of gamma-aminobutyric acid (GABA). It is thought to act by normalising dysfunctional acetylcholine, GABA and possibly monoamine neurotransmitter systems, but it may also facilitate N/L-type calcium channel opening. Nefiracetam has received attention as a treatment for seizures, depression, and dementia. Nefiracetam was found to be extremely testicular toxic in both rats and dogs; it was found to significantly decrease the levels of testicular testosterone leading to atrophy and malformation of sperm.

Epothilone D (KOS-862 or BMS-241027) is an intermediary obtained in the synthesis of members of the epothilone family and is a small-molecule microtubule stabilizer. It was investigated in Phase II trials in colorectal, metastatic breast and non-small-cell lung cancers. However, development was discontinued in 2007 in favor of a second-generation analog with a better safety profile. This drug also was studied for the treatment of Alzheimer's disease. The study ended in October 2013, and evaluation of epothilone D for Alzheimer's disease was subsequently discontinued. The mechanism by which epothilones induce microtubule polymerization appears to be similar to that of paclitaxel, in that epothilones compete with paclitaxel for binding to microtubules and suppress microtubule dynamics in a manner similar to that of paclitaxel.

Eltanolone (pregnanolone) is an endogenous neuro active steroid that is biosynthesized from progesterone. It is a positive allosteric modulator of the GABAA receptor, as well as a negative allosteric modulator of the glycine receptor. There is strong evidence that it is involved in the pathophysiology of premenstrual syndrome, catamenial epilepsy, major depression, and stress-sensitive brain disorders and is known to have sedative, anxiolytic, anesthetic, and anticonvulsant effects. It was investigated for clinical use as a general (intravenous) anesthetic. It produced unwanted side effects such as convulsions on occasion, and for that reason was not marketed. Pregnanolone possesses neuroprotective and neurotrophic properties thus has been through a number of clinical trials including for treatment of traumatic brain injury (TBI), Alzheimer disease, cognitive impairment and fragile X-associated tremor/ataxia syndrome.