Phase 1b is AMG 820 dose determining and aimed at assessing the safety and tolerability of the selected starting dose of AMG 820 in combination with pembrolizumab. Phase 2 of the study will further evaluate safety and tolerability and additionally test whether AMG 820 can enhance the anti-tumor activity observed historically with pembrolizumab alone and/or overcome lack of response to pembrolizumab monotherapy in subjects with select solid tumors.