Maytansine is an ansamycin antibiotic originally isolated from the Ethiopian shrub Maytenus serrata. Maytansine inhibits the assembly of microtubules by binding to tubulin at or near the vinblastine-binding site, decreases microtubule dynamic instability and cause mitotic arrest in cells. It exerts cytotoxicity against a number of tumor cell lines and inhibits tumor growth in vivo. However, in human clinical trials, maytansine showed a small therapeutic window due to its neurotoxicity and harmful effects on the gastrointestinal tract. The potent cell killing ability of maytansine can be used in a targeted delivery approach, such as an antibody-drug conjugate, for the selective delivery of the drug and destruction of cancer cells.

LADIRUBICIN is an idarubicin derivative with potential antineoplastic activity. Its primary effect is a DNA alkylation with sequence specificity similar to that of conventional nitrogen mustards. It possesses a wide spectrum antitumor activity against rapidly proliferating murine leukemias and on slowly growing transplantable human tumor xenografts.

Duazomycin (N-acetyl-DON) is one of the few naturally occurring compounds containing an aliphatic alpha diazoketo group, and is produced by Streptomyces ambofaciens. It is a derivative of 6-diazo-5-oxo-L-norleucine (DON) which was initially isolated from an unidentified Streptomyces species and which is produced together with N-acetyl-DON and duazomycin B (azotomycin) by S. ambofaciens. Duazomycin inhibited purine biosynthesis and caused accumulation of phosphoribosyl-N-formylglycineamide (FGAR) at low levels of inhibitor; higher levels blocked the synthesis of FGAR, indicating that the antibiotic behaved essentially like DON. Duazomycin is readily deacetylated by mammalian acylase to DON. As a glutamine antagonist, duazomycin was used in combination with azathioprine for the treatment of patients with advanced Wegener’s granulomatosis with renal involvement. Prolonged survival, remission of systemic signs and symptoms, roentogenologic improvement of pulmonary lesions, reduction in proteinuria and arrest of progression of renal insufficiency were observed.

Ioglucol is a triiodoanilide derivative patented by Mallinckrodt, Inc. as nonionic -ray contrast media

Cetocycline (formerly chelocardin or cetotetrine) is tetracycline derivative with potent antibacterial activity against a number of Gram-positive and Gram-negative multi-resistant pathogens. Cetocycline was found to be more active than tetracycline against many clinical isolates of aerobic gram-negative bacilli, but is less active against staphylococci, and has no activity against Pseudomonas. At low concentrations, like classical tetracyclines, chelocardin induces the proteomic signature for peptidyl transferase inhibition demonstrating that protein biosynthesis inhibition is the dominant physiological challenge. At higher concentrations B. subtilis mainly responds to membrane stress indicating that at clinically relevant concentrations the membrane is the main antibiotic target of chelocardin.

Beperidium (also known as SX-810 ) is a competitive antagonist against acetylcholine. Experiments on animal have shown that this compound exhibited spasmolytic and antiulcerative activities without exerting systemic antimuscarinic side effects.

Oximonam (also known as SQ 82,291) was developed as a monobactam antibiotic that had shown good activity against different bacteria of the family Enterobacteriaceae and Haemophilus influenzae and was no activity at all against staphylococci and against Pseudomonas aeruginosa.

Retosiban is a small molecule oxytocin receptor antagonist that is under evaluation for treatment of premature labor. Retosiban was found to be safe in healthy non-pregnant volunteers in phase I studies. Intravenous retosiban also had good safety and tolerability in phase II studies and was suggested to prolong pregnancies in women with preterm labor. Phase III studies have been conducted to demonstrate the efficacy of retosiban to prolong pregnancy and improve neonatal outcomes, and compare effects with a similar drug atosiban, but these studies were terminated in 2018 (not due to adverse events).

Oxisuran was developed by Parke-Davis as an antineoplastic agent. It was shown that this drug was a differential inhibitor of cell-mediated hypersensitivity. Experiments on rodents with experimental autoimmune encephalomyelitis have revealed that oxisuran was pharmacologically effective. However, information about the further development of the compound is not available.