Retinoids appear to have anti-proliferative effects on multiple myeloma lines. All trans retinoic acid (ATRA) given at high dose according to an intermittent schedule has better pharmacokinetically sustained levels. We studied 10 patients with relapsed/refractory MM who were treated with ATRA and interferon (IFN). We failed to demonstrate that this combination has clinically significant activity. Interleukin-6 (IL-6) receptor was not downregulated by ATRA in the patients we studied. Significant hematologic and neurotoxicity were encountered. This regimen of intermittent ATRA and IFN is ineffective and poorly tolerated.
