VTP-194204 (NRX 194204, IRX4204) is a second-generation retinoid X receptor (RXR) agonist that has no cross-reactivity with retinoic acid receptors, farnesoid X receptor, liver X receptors or peroxisome proliferator-activated receptor PPARγ. Rexinoid NRX 194204 selectively binds to and activates RXRs. Because RXRs can form heterodimers with several nuclear receptors (NRs), RXR activation by this agent may result in a broad range of gene expression depending on the effector DNA response elements activated. Rexinoid NRX 194204 may inhibit the tumour-necrosis factor (TNF)-mediated release of nitric oxide (NO) and interleukin 6 (IL6) and may inhibit tumour cell proliferation. This agent appears to be less toxic than RAR-selective ligands. VTP-194204 (IRX-4204) is in phase II clinical trials by Io Therapeutics for the treatment of prostate cancer. It is also in preclinical trials for the treatment of Alzheimer's disease, autoimmune diseases and multiple sclerosis.

Epinine or deoxyepinephrine is an active form of Ibopamine, which is used as a cardiovascular agent in congestive heart failure. Epinine is a stimulant of alpha-adrenoceptor activities: alpha-1 and alpha-2. Experiments on pig’s eyes have shown that epinine can be a promising candidate substance for intraoperative (e.g., cataract surgery) intracameral use in humans.

MK-212 is a 5HT2C-receptor agonist. It displays selectivity for 5-HT2C over 5-HT2A (IC50 values are 0.028 and 0.42 uM for human 5-HT2C and 5-HT2A receptors expressed in HEK293 cells respectively). A dose-dependent the effect of 5HT2C-receptor agonist MK-212 on mouse behavior was demonstrated. Intraperitoneal injection of MK-212 in high doses (0.5 and 1.0 mg/kg) increased blood level of corticosterone in mice and reduced their motor activity. In low doses of 0.1 and 0.2 mg/kg, the agonist reduced anxiety, but had no effect on motor activity. It is hypothesized that low doses of MK-212 exhibited anxiolytic activity in mice.

Taprenepag isopropyl (also known as PF-04217329) a prodrug of CP-544326 (active acid metabolite), a potent and selective EP(2) receptor agonist. Taprenepag isopropyl was studied in a clinical trials phase II involving patients with primary open angle glaucoma. According to Pfizer’s pipelines in May 2011, the study was discontinued.

Parafluorofentanyl is a selective mu-opioid agonist, an analog of fentanyl, developed by Janssen. The drug was not developed for human use but is produced and abused illegally.

Nisterime is a dihydrotestosterone derivative. Nisterime acetate (ORF-9326) was shown to inhibit implantation in several species. It is also interrupts the postimplantation stage of gestation.

Mirfentanil was developed as CNS analgesic with a short duration of action. It induced antinociception predominately through mu opioid receptors. It was shown that at doses larger than those, which exert opioid effects, mirfentanil had nonopioid analgesic effects. The drug was successfully encapsulated in liposomes having a variety of compositions. The lipid composition of the formulation was varied to optimize the stabilization of liposomes and the encapsulation of solutes. Mirfentanil participated in phase II clinical trials for the treatment of pain. However, this study was discontinued.

Naxagolide (MK-458; L 647,339; (+)-PHNO) is a dopamine D2/D3-receptor agonist, which was studied for the treatment of patients with Parkinson's disease, but further study was discontinued. In addition, was discovered, that Naxagolide C-11 ([(11)C]-(+)-PHNO) was a potential radiotracer for imaging the high-affinity state of dopamine D2 receptors with positron emission tomography (PET) in human subjects. This radiotracer is a suitable for imaging the agonist binding sites (denoted D(2HIGH) and D(3)) of these receptors. PET studies in nonhuman primates documented that, in vivo, [(11)C]-(+)-PHNO displays a relative selectivity for D(3) compared with D(2HIGH) receptor sites and that the [(11)C]-(+)-PHNO signal is enriched in D(3) contribution compared with conventional ligands such as [(11)C] raclopride. Recently was published article reflects the relationship between social attachment and dopamine D2/3 receptor availability in the brains of healthy humans using [11C]-(+)-PHNO.

Talsaclidine (WAL-2014) is a selective full agonist of M1 muscarinic receptor, having partial agonist activity on the M2 and M3 subtypes (with no in vivo consequences). The general receptor profile of talsaclidine demonstrates a nearly specific interaction with muscarinic receptors, having only weak binding affinity for alpha1- and nicotinic receptors. The drug is being tested in phase III of clinical trials for the treatment of Alzheimer's disease.