The Preclinical Safety Evaluation of Human Monoclonal Antibody against Cytomegalovirus

The human monoclonal antibody against cytomegalovinis (Mab C23)was examined pharmacokinetically and toxicologically as partof the preclinical studies prior to approval for human use.Rats given repeated intravenous administrations of Mab C23 producedno antibodies against Mab C23 and maintained a blood Mab C23level in a dose-dependent manner. However, pregnant rabbitsproduced antibodies against Mab C23. The half-life of Mab C23in plasma was 15.9 days in rats, which was similar to that ofnormal human serum -globulin (NHSG). Neither behavioral effectsnor circulatory disturbance was found in mice, rats, and dogseven after a single intravenous injection of 100 or 200 mg/kg,which corresponds to 50 or 100 times the intended clinical dosage.The repeated doses of 2, 10, or 20 mg/kg of Mab C23 on six occasionswith 1- or 2-week intervals elicited a transient decrease inleukocyte counts in rats given 10 or 20 mg/kg, but no adverseeffects in cynomolgus monkeys. Mab C23 did not cause any reproductiveor developmental toxicity when administered to rats and rabbitsat dose levels of 20 mg/kg or less. However, pregnant animalsshowed lower plasma levels of Mab C23 than non-pregnant animals.The chromosomal aberration test disclosed no clastogenicityin human lymphocytes. An immunostaining for Mab C23 revealedno localizations in several tissues of cynomolgus monkeys givenintravenous doses of Mab C23. The preclinical safety evaluationin animals other than rabbits, which produced no antibodiesagainst Mab C23, showed that the behavior of Mab C23 is pharmacokineticallysimilar to that of NHSG and is as safe as NHSG, which has longbeen used as a biological agent. However, because there wasa difference in blood levels of Mab C23 between pregnant andnonpregnant animals, its clinical administration to pregnantpatients should differ from that to non-pregnant patients.