PDCD1 and cancer: We have already learnt from clinical trials testing anti-CTLA-4 and anti-PD1 that these drugs are largely futile in eradicating secondary tumours and extending the lifespan of most cancer patients with metastasis, due to inherent or acquired drug resistance.3 Consequently, alternative immunotherapeutic approaches are required to counteract metastasis in patients that are unresponsive to CTLA-4 and/or PD-1/PD-L1 inhibitors.