AT06

AT06 is a bispecific antibody-drug conjugate (ADC) developed by Axcynsis Therapeutics, designed to target both Delta-like ligand 3 (DLL3) and seizure-related homolog 6 (SEZ6). These antigens are highly co-expressed in small cell lung cancer (SCLC) and other high-grade neuroendocrine neoplasms (NENs), but have minimal expression in normal tissues. The drug utilizes a 2+2 VHH (nanobody) format fused to a human Fc region, conjugated via a hydrophilic enzyme-cleavable linker to a proprietary topoisomerase I inhibitor payload. This dual-targeting approach aims to overcome tumor heterogeneity and antigen downregulation, which are common resistance mechanisms in single-target ADC therapies. Preclinical studies in SCLC models have demonstrated potent internalization and durable tumor growth inhibition.