Study to Evaluate VT3989 in Patients With Metastatic Solid Tumors

Inclusion Criteria: * Part 3 Combination Cohort A: Patients with pathologically diagnosed, metastatic or unresectable malignant mesothelioma (including both pleural and non-pleural) who have not received systemic therapy. * Part 3 Combination Cohort B: Patients with pathologically diagnosed incurable locally advanced (inoperable or recurrent), or metastatic NSCLC with exon 19 deletions or exon 21 L858R mutations, with or without prior treatment with Osimertinib. * Part 3 Combination Cohort C: Patients with pathologically diagnosed metastatic or unresectable malignant pleural mesothelioma who have not received systemic chemotherapy. * Measurable disease per RECIST v1.1 for non-pleural mesothelioma or other solid tumors or modified RECIST v1.1 for malignant pleural mesothelioma. mRECIST may be used for pleural extension of non-pleural mesothelioma or for mixed pleural and peritoneal (or other) mesothelioma. * ECOG: 0-1. * Adequate organ functions, including the liver, kidneys, and hematopoietic system. Exclusion Criteria: * Active brain metastases or primary CNS (central nervous system) tumors. * History of leptomeningeal metastases * Active or chronic, uncontrolled bacterial, viral, or fungal infection(s) requiring systemic therapy * Known HIV positive or active Hepatitis B or Hepatitis C * Clinically significant cardiovascular disease and prior exposure to cardiotoxic agents. * Corrected QT (QTcF) interval \> 470 msec (using Fridericia's correction formula). * Additional active malignancy that may confound the assessment of the study endpoints * Women who are pregnant or breastfeeding * Prior treatment with TEAD inhibitor.