MK-1903 is a potent and selective hydroxycarboxylic acid receptor 2 (HCA2, GPR109A) full agonist. Exhibits no binding at the GRP109B receptor. This drug had been in phase II clinical trial for the treatment of atherosclerosis and Dyslipidemia. But then, according to Merck, elevation of HDL cholesterol relative to placebo did not meet the trial's pre-specified primary objective for efficacy; no safety signals were implicated as drivers of the decision to discontinue development.

URB-597 (KDS-4103) is a highly potent and selective inhibitor of the enzyme fatty acid amide hydrolase (FAAH), which catalyzes the intracellular hydrolysis of the endocannabinoid anandamide. URB597 is one the best studied carbamate-based inhibitors. Early studies showed that the compound did not inhibit or bind related biological targets. Administration of URB597 to rats and subsequent in vivo evaluation of brain FAAH activity showed the compound elevated endogenous anandamide levels. Importantly, the compound did not produce catalepsy, hypothermia, or hyperphagia, three of the typical effects of exogenous cannabinoids. The compound did produce antinociceptive effects in the mouse hot-plate test, which were reversed by the CB1 antagonist rimonabant. These findings again support the expectation that inhibition of FAAH produces pharmacology distinct from an exogenous CB1 agonist. A more detailed study was published later showing time-course data in mice demonstrating elevation of anandamide, oleamide, and N-palmitoyl ethanolamine for 2–6 h after administration of URB597. In vivo administration of URB597 showed almost complete inhibition of FAAH by the compound, and the FAAH inhibition was still approximately 70% after 16 h. Complete recovery of CNS FAAH activity was observed 24 h after administration of URB597. In vivo administration of URB597 or the cannabinoid receptor agonist HU210 reduced both mechanical allodynia and thermal hyperalgesia in the CFA model of inflammatory pain. Effects in the inflammatory model were partially reversed by CB1 and CB2 antagonists. In a related study, the compound produced analgesic effects in the mouse CCI model (neuropathic) when administered orally. These effects were also reversed by both CB1 and CB2 antagonists.

DSM265 is an experimental antimalarial that selectively inhibits the parasite dihydroorotate dehydrogenase (DHODH). DSM265 is the first DHODH inhibitor to reach clinical development for treatment of malaria. DSM265 is highly selective toward DHODH of the malaria parasite Plasmodium, efficacious against both blood and liver stages of P. falciparum, and active against drug-resistant parasite isolates. The only possible DSM265-related adverse event was a moderate transient elevation in serum bilirubin.

GNF-156 (ganaplacide or KAF-156) is an antimalarial agent that is part of the imidazolopiperazine family. It exerts activity against pre-erythrocytic liver stages, asexual and sexual blood stages. An improvement compared to existing antimalarial drug combinations is that this compound shows promising single-dose antimalarial activity, and no serious safety and tolerability concerns in humans are known so far. Phase II clinical trials have been completed for GNF-156. Its potential is also being investigated in combination with lumefantrine (an aryl-amino alcohol) in LUM-KAF156.

MK 3577 is an orally active glucagon receptor antagonist which was under development by Merck & Co for the treatment of type 2 diabetes mellitus. MK 3577 demonstrate activity in cellular models and preclinical trials. In phase II clinical trials MK 3577 shows good efficacy and acceptable level of adverse events, but no further development reports were published.