Evaluation of human anti-mouse antibody response in normal volunteers following repeated injections of fanolesomab (NeutroSpec), a murine anti-CD15 IgM monoclonal antibody for imaging infection

BACKGROUND: Fanolesomab (NeutroSpec) is a murine monoclonal Tc labelled anti-CD15 IgM antibody that localizes collections of human polymorphonuclear neutrophils (PMNs) at sites of infection. OBJECTIVES: The objectives of this study were to evaluate the safety of repeated injections of fanolesomab and the extent of induction of human anti-mouse antibody (HAMA) response. METHODS: Thirty healthy adults (15 men and 15 women) were enrolled in the study. Subjects were injected on two separate occasions, separated by 21 days, with 125 microg of fanolesomab that had been labelled with decayed Tc. HAMA assays were performed on blood samples drawn prior to each injection, and at 7 and 28 days following the second injection. Safety was determined by monitoring for adverse events, and for changes in vital signs, physical examination and clinical laboratory measurements. RESULTS: Five subjects exhibited induction of HAMA (16.7%; 95% CI, 6.3-34.2%). Two were considered marginal responses (increase from 5 to 31, and 5 to 20 and 24 ng x ml), and three were considered moderate (7 to 228, 7 to 140 and 270, and 7 to 35 and 450 ng x ml). There were no strong responses (greater than 1000 ng x ml). Seven subjects experienced adverse events, most of which were coincidental to administration of fanolesomab. There were no serious or severe adverse events. CONCLUSIONS: Repeated fanolesomab injections at clinically useful doses does not appear to induce a strong HAMA response nor does it present a risk for serious adverse events.