Study to Assess Adverse Events and Change in Disease Activity in Adult Participants With Advanced Solid Tumors Receiving Intravenous (IV) ABBV-400 as Monotherapy and in Combination With IV Bevacizumab

Cancer is a condition where cells in a specific part of body grow and reproduce uncontrollably. The purpose of this study is to assess adverse events and change in disease activity when ABBV-400 is given to adult participants to treat advanced solid tumors. ABBV-400 is an investigational drug being developed for the treatment of advanced solid tumors. Study doctors put the participants in groups called treatment arms. The Recommended Phase 2 dose (RP2D) will be explored. Each treatment arm receives a different dose of ABBV-400. This study will include a dose escalation phase to determine the best dose of ABBV-400, followed by a dose expansion phase to confirm the dose and combination with bevacizumab. Approximately 500 adult participants with NSCLC, gastroesophageal adenocarcinoma/gastroesophagel junction adenocarcinoma (GEA) and colorectal cancer (CRC) or advanced solid tumors, will be enrolled in the study in approximately 7-10 sites in the Dose Escalation phase and 85-95 sites in the Dose Expansion phase worldwide. Dose escalation arms, participants will receive intravenous (IV) escalating doses of ABBV-400 monotherapy. Dose expansion arms, participants in the following advanced solid tumor indications: non-squamous NSCLC with wildtype EGFR-expression (wtEGFR NSCLC) \[Part 2i\] or mutated EGFR-expression (mutEGFR NSCLC) \[Part 2ii\], squamous NSCLC \[Part 2iii\], GEA \[Part 3\] will receive intravenous (IV) ABBV-400 monotherapy, participants CRC will receive IV ABBV-400 monotherapy in expansion \[Part 4\], participants MET amplification will receive IV ABBV-400 monotherapy in expansion \[Part 5\], participants MET mutation will receive IV ABBV-400 monotherapy in expansion \[Part 6\], participants CRC safety lead in will receive escalating doses of IV ABBV-400 in combination with IV bevacizumab \[Part 7a\], and participants CRC dose optimization in will the low or high dose of IV ABBV-400 determined in Part 7a in combination with IV bevacizumab or oral triflurid