NEW YORK (360Dx) – Agilent Technologies announced on Tuesday that the US Food and Drug Administration has expanded its approval of the firm's Dako PD-L1 IHC 22C3 pharmDx assay as a companion diagnostic test for Merck's anti-PDL-1 immunotherapy pembrolizumab (Keytruda) for head and neck squamous cell carcinoma (HNSCC).