Toll-likereceptor (TLR) 7 and 8agonists can potentially be used in the treatment of viral infections and are particularly promising for chronic hepatitis B virus (HBV) infection. An internal screening effort identified a pyrimidine Toll-likereceptor 7 and 8 dual agonist. This provided a novel alternative over the previously reported adenine and pteridone type of agonists. Structure–activity relationship