A naturally occurring serine derivative diazo compound with antineoplastic properties, Azaserine functions as a purine antagonist and glutamine analogue (glutamine amidotransferase inhibitor) that competitively inhibits pathways in which glutamine is metabolized. An antibiotic and antitumor agent, Azaserine was used in clinical studies as a potential antineoplastic agent. Azaserine is an inhibitor of glutamine: fructose-6-phosphate amidotransferase (GFAT), which is the rate-limiting enzyme in the hexosamine biosynthetic pathway. Azaserine is used to model pancreatic cancer in rodents.

Ozagrel is a thromboxane A2 synthesis inhibitor used for the treatment of cerebral vasospasm and asthma due to its antiplatelet and anti-inflammation properties.

Iclaprim is an investigational broad-spectrum diaminopyrimidine antibiotic in development for the treatment of acute bacterial skin and skin structure infections (ABSSSIs). Iclaprim acts on bacterial cells by competitively inhibiting dihydrofolate reductase (DHFR), a key enzyme in the folate cycle; the same mode of inhibition is exerted by trimethoprim. Iclaprim resistance is mainly determined by point mutations in the dfr gene as studied in S. aureus and S. pneumoniae. Surveillance studies demonstrate that the spectrum of activity of iclaprim includes many organisms indicated in cSSSI including S. aureus and S. pyogenes. Iclaprim is bactericidal in vitro, generally at concentrations equal to the MIC that are maintained in human plasma for several hours after a therapeutic dose. Bactericidal activity is primarily time-dependent and concentration independent. Due to its structural similarity with trimethoprim, iclaprim is synergistic with sulfonamides against a broad spectrum of bacterial species. The antimicrobial mechanism of action of iclaprim is mediated by competitive inhibition of bacterial DHFR, the same mode of inhibition exerted by TMP. The activity of iclaprim against TMP-R mutants of S. aureus and S. pneumoniae is attributable to additional hydrophobic interaction between iclaprim and the enzyme. The same mechanism of action of iclaprim, competitive inhibition with the natural substrate DHF, is seen against both TMP-S and -R enzymes. Iclaprim is well suited for use as a first-line empiric monotherapy in patients with ABSSSI who are comorbid with renal impairment for the following reasons. n July 2015, the U.S. Food and Drug Administration, or FDA, designated the IV formulation of iclaprim as a Qualified Infectious Disease Product (QIDP) for ABSSSI and HABP. QIDP status grants iclaprim regulatory Fast Track designation, Priority Review and, if approved, a five-year extension to the statutory market exclusivity period in the United States, resulting in 10 years of market exclusivity from the date of approval.

Eseridine (Geneserine) has been known for many years as an anticholinergic agent and used in therapy as a gastrointestinal antispastic. Eseridine salicylate is an inhibitor of cholinesterase activity that has been given by mouth in preparations for dyspepsia and other gastric disorders. It has also been studied for the treatment of Alzheimer’s disease.

Benserazide is a peripherally-acting aromatic L-amino acid decarboxylase (AADC) or DOPA decarboxylase inhibitor. Benserazide is only used in conjunction with L-dopa for the treatment of Parkinson's disease under the brand name Madopar in the UK. Madopar HBS (125 mg) is a controlled-release dosage form with 100 mg L-dopa and 25 mg benserazide.

Sivelestat is a neutrophil elastase inhibitor approved in Japan and the Republic of Korea for acute lung injury, including acute respiratory distress syndrome in patients with systemic inflammatory response syndrome. Sivelestat is marketed as Elaspol in Japan. Sivelestat competitively inhibited human neutrophil elastase (IC50 = 0.044 uM, Ki = 0.2 uM). It also inhibited leukocyte elastase obtained from rabbit, rat, hamster and mouse.

Zifrosilone (MDL 73745 or (2,2,2-trifluoro-1-(3-trimethylsilylphenyl)ethanone) is a acetylcholinesterase inhibitor. Zifrosilone was studied as a drug for the treatment of Alzheimer's disease however its development has been discontinued.

Fasudil is a potent Rho kinase inhibitor, which was developed by Asahi Kasei. The drug is used in Asia for the prevention of cerebral vasospasm in patients with subarachnoid hemorrhage.

Lazabemide is a reversible and selective inhibitor of monoamine oxidase B (MAO-B) that was under clinical development against Parkinson's disease, Alzheimer's disease and as an aid to smoking cessation. The development of the drug was discontinued due to liver toxicity.

Aceglatone (Glucaron/ 2.5-Di-O-acetyl-D-glucaro-1,4:6,3-dilactone/ DAGDL ) is a non-toxic natural inhibitor of beta-glucuronidase. Is an antineoplastic drug available in Japan, which is used for preventive therapy after preservative operation against bladder cancer.