AbTis has prevailed in a U.S. patent invalidity fight over AbClick, the company's core antibody-drug conjugate, or ADC, platform. The U.S. Patent Trial and Appeal Board, or PTAB (U.S. patent tribunal), rejected all arguments raised by Japan's Ajinomoto in an inter partes review, or IPR (administrative patent challenge), allowing AbTis to keep the U.S. patent protection behind the platform. The dispute centered on AbClick, a site-specific ADC platform that attaches drugs to a designated lysine site, Lys248, in an antibody's Fc region. AbTis says that approach is designed to produce a uniform drug-to-antibody ratio, or DAR (number of drugs attached per antibody), supporting more consistent ADC quality. Ajinomoto had challenged the patent on written description, enablement, definiteness, novelty and non-obviousness grounds under Sections 112, 102 and 103 of U.S. patent law. AbTis, a Dong-A ST subsidiary developing ADC drug candidates and platform technology, said the ruling preserves a core U.S. patent protecting AbClick. CEO Choi Hyung-seok said the decision validates the platform's patent position and would support broader global partnerships, technology commercialization and continued ADC drug development.