Disposition, metabolism and mass balance of [14C]apremilast following oral administration

1. Apremilast is a novel, orally available small molecule that specifically inhibits PDE4 and thus modulates multiple pro-and anti-inflammatory mediators, and is currently under clinical development for the treatment of psoriasis and psoriatic arthritis. The pharmacokinetics and disposition of [C-14]apremilast was investigated following a single oral dose (20 mg, 100 mu Ci) to healthy male subjects. 2. Approximately 58% of the radioactive dose was excreted in urine, while faeces contained 39%. Mean C-max, AUC(0-infinity) and t(max) values for apremilast in plasma were 333 ng/mL, 1970 ng*h/mL and 1.5 h. Apremilast was extensively metabolized via multiple pathways, with unchanged drug representing 45% of the circulating radioactivity and <7% of the excreted radioactivity. 3. The predominant metabolite was O-desmethyl apremilast glucuronide, representing 39% of plasma radioactivity and 34% of excreted radioactivity. The only other radioactive components that represented >4% of the excreted radioactivity were O-demethylated apremilast and its hydrolysis product. Additional minor circulating and excreted compounds were formed via O-demethylation, O-deethylation, N-deacetylation, hydroxylation, glucuronidation and/or hydrolysis. The major metabolites were at least 50-fold less pharmacologically active than apremilast. Metabolic clearance of apremilast was the major route of elimination, while non-enzymatic hydrolysis and excretion of unchanged drug were involved to a lesser extent.