Activity of MDI-301, a novel synthetic retinoid, in xenografts.

The efficacy of MDI-301, a non-toxic novel synthetic retinoid, was found to be equivalent to the natural 9-cis-retinoic acid (RA) in vitro against estrogen-dependent MCF7 and T47D breast cancer cell lines which express RA receptor (RAR) alpha. Both retinoids also showed similar efficacy against established PC-3 prostate carcinoma xenografts. MCF7 tumor xenografts showed a reduction in tumor growth of 48% without systemic side-effects upon treatment with MDI-301 compared with MCF7 controls. Tumor xenografts derived from MDA-MB-231, an estrogen-independent breast cancer cell line that expresses low levels of RARalpha, were unresponsive. This study demonstrates that MDI-301 is as efficacious as 9-cis-RA against cancer cells with RARalpha, with no signs of toxicity in vivo, making it a potential candidate for cancer therapy.