Unexpected hepatotoxicity in a phase I study of TAS266, a novel tetravalent agonistic Nanobody® targeting the DR5 receptor

Purpose TAS266 is a novel agonistic tetravalentNanobody® targeting the DR5 receptor. In preclinical studies, TAS266 was more potent than a cross-linked DR5 antibody or TRAIL. This first-in- human studywas designed to evaluate the safety and tolerability, maximum tolerated dose, pharmacokinetics, pharmacodynamics, immunogenicity, and preliminary efficacy of TAS266.