Preclinical absorption, distribution, metabolism and excretion (ADME) characterization of ICAM1988, an LFA-1/ICAM antagonist, and its prodrug

Intercellular adhesion molecule (ICAM)-1988 is a small molecule lymphocyte function-associated antigen-1 (LFA-1) antagonist being considered for its anti-inflammatory properties. Following intravenous administration of ICAM1988, clearances in mice, rats, dogs, and monkeys were 17.8, 3.31, 15.4, and 6.85 ml min(-1) kg(-1), respectively. In mass balance studies using [(14)C]-ICAM1988 in rats dosed intravenously, unchanged ICAM1988 contributed to 25.1% of the dose. In rats, the systemic bioavailability of ICAM1988 was improved to 0.28 when the drug was administered orally as its isobutyl ester, ICAM2660. In rats, this was consistent with the complete in vitro conversion of ICAM2660 to ICAM1988 in plasma, and liver and intestinal S9. In dogs and monkeys, ICAM2660 did not improve the bioavailability of ICAM1988. This is consistent with limited in vitro conversion of ICAM2660 to ICAM1988 in plasma and liver S9. In human in vitro studies, ICAM2660 conversion to ICAM1988 in liver was similar to rats while no conversion in plasma and intestinal S9 fractions were observed. Based on the in vitro metabolism similarities of human and rat, it would be anticipated that in human oral administration of ICAM2660 would improve the systemic exposure of ICAM1988.