 This is an open-label, Phase I, dose-escalation study to determine the recommended Phase 2 dose RPTD, maximum tolerated dose MTD, and evaluate the safety and pharmacokinetic PK profile of ABBV-181. This study will also evaluate the safety and tolerability of ABBV-181 in combination with Rovalpituzumab Tesirine. The study will consist of 2 parts: ABBV-181 monotherapy dose escalation and expansion, and ABBV-181 in combination with Rovalpituzumab Tesirine. 