An ongoing multicenter, phase 2 study (NCT04633278) of intratumoral administration of CMP-001, a virus-like particle containing CpG-based TLR9 agonist, in combination with intravenous pembrolizumab is currently being evaluated in patients with recurrent or metastatic HNSCC [30]. Here, TLR9 is linked to head and neck squamous cell carcinoma.