Progress in drug development of immunostimulatory CpG oligodeoxynucleotide ligands for TLR9

Oligodeoxynucleotides (ODNs) with unmethylated deoxycytosine-deoxyguanosine (CpG) motifs are recognised by Toll-like receptor (TLR)9 expressed in specialised cell subsets of the human immune system, B cells and plasmacytoid dendritic cells. TLR9-mediated stimulation of the immune system leads to a plethora of directed effects linking innate to adaptive immune responses. This allows the use of TLR9 agonists as highly effective targeted immunomodulatory drugs with broad potential applications as vaccine adjuvants, stand-alone therapy or in combination with other therapies in cancer, infectious diseases or asthma and allergy. TLR9 agonists represent a new class of small (8-30 bases long), easily synthesised, non-antisense ODN pharmaceuticals.