Checkpoint therapy with PD-(L)1 and CTLA4-directed monoclonal antibodies has shown to be extremely effective for many patients with a variety of tumors. PD-1 testing, alone, however, are lacking in selecting patients for therapy – up to 17% of patients who do not meet criteria for PD-1 positivity respond to treatment, and many patients with PD-1 tumors do not respond well to checkpoint therapy. Continue reading →