Therapy of epithelial tumors with an aromatic retinoic acid analog.

The properties of a new aromatic retinoic acid analog are described. The compound: all-trans-N-ethyl-9-(4-methoxy-2,3,6-trimethylphenyl)-3,7-dimethyl-2,4,6,8-nonatetraenamide = Ro 11-1430, exerts a therapeutic influence on chemically induced papillomas and carcinomas of the skin of mice. It leads to a marked regression of chemically induced epithelial tumors but does not inhibit the growth of transplantable tumors. The therapeutic use of retinoic acid and its analogs is limited by the appearance of the toxic side effects of the so-called hypervitaminosis A syndrome. The relationship between the anti-tumor activity and these toxic effects is considered a good inidicator for establishing the quality of a compound. The new retinoic acid analog posses a ten times more favorable therapeutic ratio than retinoic acid. The mechanism of action is discussed.