Furthermore, a phase I clinical trial showed that the combination of the IDO-1 inhibitor navoximod (GDC-0919) with atezolizumab (PD-L1 inhibitor) is characterized by good tolerability and acceptable anti-tumour activity in patients with solid tumours, including one patient with HNSCC [482]. The gene discussed is IDO1; the disease is head and neck squamous cell carcinoma.