Inhibition of growth and regression of a transplantable rat chondrosarcoma by three retinoids.

An aromatic analog of retinoic acid, all-trans-9-(4-methoxy-2,3,6-trimethylphenyl)-3,7-dimethyl-2,4,6,8-nonatetraenoic acid (Ro 10-1670), its ethyl esther (Ro 10-9359), and ethyl amide (Ro 11-1430) have been shown to inhibit the growth of a transplantable rat chondrosarcoma. The inhibition observed occurred over a range of tolerated doses. At the higher tolerated dose levels, significant regressions of already established tumors were observed. All three compounds were active when administered ip for 2 or 4 weeks. The ethyl ester, Ro 10-9359, and the etyl amide, Ro 11-1430, were also active when administered for 4 weeks as dietary admixes. In the latter experiments, both compounds were equally effective at tolerated doses, but Ro 11-1430 was less toxic than Ro 10-9359 at higher doses.