The study will determine the recommended Phase 2 dose (RP2D) of livmoniplimab (ABBV-151) administered as monotherapy and in combination with budigalimab (ABBV-181) as well as to assess the safety, tolerability, pharmacokinetics (PK), and preliminary efficacy of livmoniplimab alone and in combination with budigalimab. The study will consist of 2 parts: dose escalation and dose expansion.