Bolt Biotherapeutics Inc. has synthesized antibody-drug conjugates (ADCs) comprising cysteine-mutant antibodies targeting programmed cell death 1 ligand 1 (CD274; PD-L1) covalently bound to one or more Toll-like receptor 7 (TLR7) and/or TLR8 agonists through a linker reported to be useful for the treatment of cancer.