Etretinate
Etretinate is a synthetic oral retinoid that is a prodrug of acitretin.  Etretinate activates retinoid receptors, causing an induction of cell differentiation, inhibition of cell proliferation, and inhibition of tissue infiltration by inflammatory cells.  Etretinate is no longer commercially available in the U.S. due to the extended potential for teratogenic effects related to its long half-life. (NCI04)