A Study of JNJ-89402638 for Metastatic Colorectal and Gastric Cancers

For Part 1 (dose escalation), Part 2 (Arm A [JNJ-89402638 monotherapy]): Have histologically or cytologically confirmed diagnosis of colorectal adenocarcinoma (CRC) progressing after 2 or more prior lines of standard therapy in the metastatic/unresectable setting; For Part 2 Arm B (JNJ-89402638 + bevacizumab or biosimilar): Have histologically or cytologically confirmed diagnosis of CRC progressing after 2 or more prior lines of standard therapy in the metastatic/unresectable setting; For Part 2 Arm C (JNJ-89402638 + FOLFOX/bevacizumab or biosimilar): Have histologically or cytologically confirmed diagnosis of microsatellite stable (MSS) or proficient mismatch repair (pMMR) CRC progressing after 1 or more prior lines of standard therapy in the metastatic/unresectable setting. Participants must have previously received a fluoropyrimidine and irinotecan doublet (such as FOLFIRI); For Part 2 Arm D (JNJ-89402638 + FOLFIRI/bevacizumab or biosimilar): Have histologically or cytologically confirmed diagnosis of MSS or pMMR CRC progressing after 1 prior line of standard therapy in the metastatic/unresectable setting. Must not have received irinotecan previously for metastatic disease; For Part 2 Arm E (JNJ-89402638 monotherapy in mGAC): Have histologically or cytologically confirmed diagnosis of gastric adenocarcinoma or gastroesophageal junction adenocarcinoma progressing after 1 or more prior lines of standard therapy in the metastatic/unresectable setting

Have evaluable or measurable disease per response evaluation criteria in solid tumors (RECIST) version 1.1

Part 1: Must have either measurable or evaluable disease

Part 2: Must have at least 1 measurable lesion