Rozrolimupab, symphobodies against rhesus D, for the potential prevention of hemolytic disease of the newborn and the treatment of idiopathic thrombocytopenic purpura.

Currently under codevelopment by Symphogen and Swedish Orphan Biovitrum, rozrolimupab is the first in a new class of recombinant polyclonal antibodies, known as symphobodies, produced using a proprietary technology from Symphogen. Rozrolimupab is being investigated for the prevention of hemolytic disease of the fetus and newborn (HDFN) and for the treatment of idiopathic thrombocytopenic purpura (ITP). Rozrolimupab comprises 25 genetically unique IgG1 antibodies, all of which are specific for the rhesus D (RhD) erythrocyte protein. In preclinical studies, rozrolimupab demonstrated binding to erythrocytes that was comparable with that of two plasma-derived anti-D Ig preparations. In a phase I clinical trial in healthy male volunteers, treatment with rozrolimupab was not associated with serious adverse events. In a phase II clinical trial of rozrolimupab in healthy, male, RhD-negative volunteers, rozrolimupab dose-dependently cleared RhD-positive erythrocytes from the circulation. Phase II clinical trials in ITP and HDFN are currently ongoing. Phase III clinical trials are necessary to establish the efficacy and safety profile of rozrolimupab compared with standard plasma-derived anti-D Ig preparations.