Checkmate Pharmaceuticals, Inc. announced that patient dosing was initiated in the anti-PD-1 refractory cutaneous squamous cell carcinoma (CSCC) arm of a Phase 2 multi-indication study evaluating the efficacy and safety of vidutolimod in combination with cemiplimab for the treatment of patients with anti-PD-1 refractory CSCC. Vidutolimod is an advanced generation Toll-like receptor 9 (TLR9) agonist, delivered as a biologic virus-like particle utilizing a CpG-A oligodeoxynucleotide as a key component.