Alovudine (3’ -deoxy-3’ fluorothymidine) is a nucleoside reverse transcriptase inhibitor (NRTI) initially tested in the early 1990s, before the era of combination therapy and before the availability of plasma viral load measurement. Initial toxicity studies showed that the primary target organ of toxicity was the bone marrow. A lack of clear advantages in activity over zidovudine, the only drug approved in the early 1990s, and the potential for bone marrow toxicity caused alovudine development to be stopped [6]. However, later in vitro studies found alovudine to be very effective at suppressing several NRTI-resistant HIV-1 mutants, including isolates with multiple thymidine-associated mutations (TAMs) or multi-NRTI-resistance mutations. Alovudine at a dose of 7.5 mg/day added to a failing antiretroviral combined regimen in patients with isolates resistant to other NRTIs yielded a median viral load decline after a 4-week period in patients not receiving concomitant stavudine. In July 2003, Medivir out-licensed it's HIV antiviral MIV-310 to Boehringer Ingelheim. Under the terms of the agreement, Boehringer Ingelheim will make upfront and milestone payments to Medivir totaling up to 122 million euro in the event that all development and performance milestones are met. In March 2005, Boehringer Ingelheim recently completed a clinical trial of MIV-310 (alovudine) in HIV/AIDS. The efficacy exhibited by MIV-310 at the doses tested showed antiviral activity but did not achieve the target level of efficacy which had previously been defined. Boehringer Ingelheim, therefore, decided to stop the development of this investigational drug.

Mexoprofen was studied as an analgesic agent. This compound has never been marketed.

Clogestone Acetate (AY-11440) is a steroidal progestin that was synthesized in 1964 and was investigated as a progestin-only contraceptive but was never marketed.

Crisnatol is a derivative of arylmethylaminopropanediol with significant antineoplastic activity in a variety of murine and human tumor models. Crisnatol functions as a DNA intercalator, with the presence of additional basic amine groups in the sidechain enhancing binding to DNA due to electrostatic interactions. Crisnatol did not show antitumor efficacy in patients with ovarian carcinoma. In another clinical study, 2 of 26 patients with glioma showed complete long-lasting responses to the drug. The dose-limiting side effect was neurotoxicity.

Bertosamil was developed as an anti-ischemic and anti-arrhythmic drug that inhibits the atrial potassium channels Kv1.2, Kv1.4 and Kv1.5. However, the development of this drug has been discontinued.

Endixaprine (SR 41378 or 3-(4-hydroxy-1-piperidinyl)-6-(2,4-dichlorophenyl)-pyridazine) is a aminopyridazine derivative. Endixaprine is a nonbenzodiazepine compound with a pharmacological profile similar to barbiturates and benzodiazepines. It possesses anticonflict, anticonvulsant, antianxiety and hypnotic activities in rodents.

Emitefur or BOF-A2 is a fluorinated pyrimidine antimetabolite exerting antineoplastic properties. It is a compound composed of 5-fluorouracil (5-FU) and 3-cyano-2,6-dihydroxypyridine (CNDP), an inhibitor of 5-FU degradation by dihydrouracil dehydrogenase in order to prolong the blood 5-FU level as well as increase selective toxicity to a tumor. Emitefur demonstrated clinical activity in preliminary studies in Japan. Emitefur development for the treatment of solid tumors has been discontinued.

Salmefamol is a beta2-adrenoceptor agonist that was studied in asthmatic patients. In clinical trials, the drug had shown marked efficacy with low toxicity and was generally well tolerated. However, information about the further development of salmefamol as a bronchodilator drug is not available.

Metrifudil (previously known as Y-341) is a synthetic adenosine analog that is acid stable and has a prolonged duration of action. Metrifudil is a selective adenosine A2 receptor agonist and has anticonvulsant activity against seizures. The drug is also studied for the treatment of glomerulonephritis. However, no recent development has been reported.