Sabarubicin (previously known as MEN-10755), a disaccharide analog of doxorubicin that was developed by Menarini Pharmaceuticals for the treatment of solid tumors, including small cell lung cancer and prostate cancer. Sabarubicin exhibits a superior antitumor efficacy, presumably related to the activation of p53-independent apoptosis. The drug participated in phase II clinical trials to study its effectiveness in treating patients who have progressive prostate cancer that has not responded to hormone therapy and in chemotherapy-naive patients with extensive stage small cell lung cancer. On 21 December 2004, the European Commission granted the orphan designation to Menarini for sabarubicin for the treatment of small cell lung cancer.

Liarozole is an imidazole-containing compound that inhibits the cytochrome P-450-dependent metabolism of all-trans-retinoic acid (RA). Liarozole, a retinoic acid (RA) metabolism-blocking agent (RAMBA) in clinical development, has been granted orphan drug designation for congenital ichthyosis by the European Commission and the U.S. Food and Drug Administration. Later, based on the mixed results from a phase II/III trial of liarozole for the treatment of ichthyosis, Barrier decided to discontinue the development of liarozole. Liarozole displays antitumor activity against androgen-dependent and independent rat prostate carcinomas.A large phase III international study was completed comparing liarozole 300 mg twice daily with cyproterone acetate (CPA) 100 mg twice daily in a total of 321 patients with metastatic prostate cancer in relapse after first-line endocrine therapy. The results indicate that liarozole might be a possible treatment option for prostate cancer (PCA) following failure of first-line endocrine therapy.

Perifosine is an orally active alkyl-phosphocholine compound with potential antineoplastic activity. Perifosine is an Akt inhibitor, which targets the pleckstrin homology domain of Akt, thereby preventing its translocation to the plasma membrane. Perifosine exerts Akt-dependent and Akt-independent effects, and although many preclinical studies have documented Akt inhibition by perifosine, clinical validation of these findings is lacking. Perifosine is in phase II and III clinical trials for the treatment of neuroblastoma, glioblastoma multiforme and other solid tumors.

Seocalcitol (EB 1089) is a vitamin D analog, and agonist of the vitamin D receptor. Antineoplastic activity of seocalcitol was tested in clinical trials against hepatocellular carcinoma, pancreatic, breast and colorectal cancer. Due to inconsistent results of clinical trials, development of seocalcitol was discontinued by Leo Pharma.

Rebeccamycin analog (RA, Becatecarin/ BMS 181176, rebeccamycin derivative, NSC 655649) is an antitumor antibiotic with inhibitory activity against both topoisomerase I and II, and DNA-intercalating properties. The mechanism of action of becatecarin is not exactly known, but it is thought that by inhibiting (blocking) the function of topoisomerase enzymes, it will destroy cancer cells and slow down the growth of the tumour. On 25 July 2006, orphan designation (EU/3/06/388) was granted by the European Commission to Helsinn Birex Pharmaceuticals Ltd, Ireland, for becatecarin for the treatment of cancers of the biliary tree.

Tanespimycin (17-allylamino-17-demethoxygeldanamycin, 17-AAG) is a synthetic analogue of geldanamycin, an antibiotic first purified in 1970 from Streptomyces hygroscopicus. Tanespimycin is an Hsp90 inhibitor that has demonstrated the potential to disrupt the activity of multiple oncogenes and cell signaling pathways implicated in tumor growth, including HER2, a key pathway in breast cancer. Tanespimycin was being under development by Kosan Biosciences. It was in phase 3 clinical development with bortezomib for the treatment of multiple myeloma (MM). However, in 2010 the company halted development of tanespimycin, during late-stage clinical trials as a potential treatment for multiple myeloma. While no definitive explanation was given, it has been suggested that Bristol-Myers Squibb halted development over concerns of the financial feasibility of tanespimycin development given the 2014 expiry of the patent on this compound, and the relative expense of manufacture.

Fenretinide (4-HPR) is an orally-active synthetic phenylretinamide analogue of retinol (vitamin A) with potential antineoplastic and chemopreventive activities. Fenretinide binds to and activates retinoic acid receptors (RARs), thereby inducing cell differentiation and apoptosis in some tumor cell types. This agent also inhibits tumor growth by modulating angiogenesis-associated growth factors and their receptors and exhibits retinoid receptor-independent apoptotic properties. Phase III clinical trial data has suggested that fenretinide reduces breast cancer relapse in pre-menopausal women. Fenretinide is the most studied retinoid in breast cancer chemoprevention clinical trials due to its selective accumulation in breast tissue and its favorable toxicological profile. This agent showed a significative reduction of the incidence of second breast tumors in premenopausal women confirmed after 15-year followups. Fenretinide, a drug being developed by Sirion Therapeutics, slowed the progression of advanced dry age-related macular degeneration (AMD) by 45 percent for people receiving a higher dose of the treatment in a Phase II clinical trial. Sirion has been granted a Fast Track designation for the treatment by the FDA. Fenretinide is in phase II clinical trials for the treatment of B-cell lymphoma, chronic lymphocytic leukemia. It is also in phase I clinical trials for the treatment of cystic fibrosis.

Kifunensine is an immunoactive compound originally produced by Kitasatosporia kifunense, which displays competitive inhibition against immunosuppressive factor in tumor-bearing mice. Kifunensine has also been shown to be a potent inhibitor of the purified glycoprotein processing enzyme, mannosidase I (MAN1), specifically MAN1A1, MAN1A2, MAN1B1 and MAN1C1. Kifunensine inhibits human endoplasmic reticulum α-1,2-mannosidase I and Golgi Class I mannosidases IA, IB and IC with Ki values of 130 and 23 nM, respectively. Enzymes of this class are important factors for the biosynthesis of various types of N-linked oligosaccharide structures. Inhibition of these structures by kifunensine can interfere with cell-to-cell adhesion, targeting of lysosomal hydrolases to lysosomes, and clearance of asialoglycoproteins from the serum. Kifunensine is used to suppress Endoplasmic Reticulum-Associated Degradation (ERAD) via the inhibition of endoplasmic reticulum-associated mannosidase activity. Kifunensine has shown potential for treatment of sarcoglycanopathies and lysosomal storage disorders. Orphan designation (EU/3/11/906) was granted by the European Commission to Généthon, France, for kifunensine for the treatment of beta sarcoglycanopathy, but it was withdrawn later. Kifunensine’s use as a therapeutic is currently being researched in several conditions that benefit from its ability to inhibit mannosidase I.