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.

Tetrahydrouridine is a potent competitive reversible inhibitor of cytidine deaminase. Tetrahydrouridine can inhibit cell proliferation by regulation of the cell cycle independent of cytidine deaminase (CDA) expression levels. Tetrahydrouridine may be useful for researching potential treatments for high CDA-expressing tumors. Tetrahydrouridine use, alone or in combination with the DNA methyltransferase inhibitor 5-fluoro-2’-deoxycytidine, is being evaluated in animal models and clinical trials for diseases, including cancer and mitochondrial DNA depletion syndrome.