Current treatments for Graves’ hyperthyroidism (GH) and Graves’ orbitopathy (GO) are ineffective. Researchers assessed the preclinical in vitro efficacy of SYD-5115 (Byondis BV), a novel low-molecular-weight thyrotropin receptor (TSH-R) antagonist. The compound comprises an N-acetylated dihydropyrrole pyrimidine core with various substituents, including a difluorinated-spirocyclohexyl ring and a chiral carbamate group on the pyrimidine ring.