Apremilast inhibits TNFα release from LPS-stimulated monocytes and human rheumatoid synovial membrane cultures. Human peripheral blood monocytes were treated with increasing concentrations of apremilast, 30 minutes before stimulating with 10 ng/ml lipopolysaccharide (LPS) for 24 hours. (a) Culture supernatants were assayed for TNFα by ELISA. Data is representative of three donors. Human rheumatoid arthritis (RA) synovial membrane cells were cultured for 48 hours in the presence of apremilast, rolipram or controls and spontaneous production of (b) TNFα, (c) IL-6 and (d) IL-10 in culture supernatants was measured by ELISA. Means and standard errors of percent inhibition, from five (apremilast) or two (rolipram) donors are plotted. As a positive control, cells were treated with a combination of anti-TNFα mAb and IL-1RA. Statistical analysis was calculated by one-way analysis of variance and Dunnett's multiple comparison test. Each test group was compared to (a) cells + LPS, or (b to d) cells only. * P < 0.05, ** P < 0.01, *** P < 0.001.