PDCD1 and Merkel cell skin cancer: A Phase II study using off-the-shelf activated NK (aNK) cells in combination with ALT-803, an IL-15 superagonist, in Merkel cell carcinoma showed excellent tolerability of the combination and promising efficacy, with objective responses in 2 of 7 patients with refractory MCC, including reversal of PD-1 refractoriness in one patient [68].