This is a Phase 1, open-label, multicenter, FIH study to evaluate the safety, tolerability, recommended Phase 2 dose (RP2D), PK/PD, and preliminary anti-tumor activity of ISM6331 in participants with advanced or metastatic malignant mesothelioma or other solid tumors. The study consists of two parts, a dose escalation part (Part 1) and a dose selection optimization part (Part 2).

Inclusion Criteria:

1. Male or female participants with age ≥18 years at the time of signing the informed consent.
2. Histologically confirmed unresectable advanced or metastatic malignant mesothelioma or other solid tumors, who have failed standard therapy or for whom no effective standard therapy exists, participants for part 1 is regardless of the presence or absence of the genetic alterations of the Hippo pathway, but for part 2 participants with solid tumors other than mesothelioma, genetic testing documentation must demonstrate Hippo signaling pathway dysregulation.
3. Participants with malignant mesothelioma must have prior exposure to at least immune checkpoint therapy and platinum-based chemotherapy.
4. Presence of at least one evaluable lesion in Part 1 or one measurable target lesion in Part 2 according to Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1) for participants with non-pleural mesothelioma or other solid tumors and modified RECIST (mRECIST) v1.1 for participants with malignant pleural mesothelioma.
5. Eastern Cooperative Oncology Group (ECOG) performance status (PS) ≤1.
6. Life expectancy of ≥12 weeks as judged by the investigator.
7. Adequate organ function as determined by medical assessment (within 7 days prior to the first dose of study treatment).
8. Capable of providing signed informed consent form (ICF) and complying with the requirements and restrictions listed in the ICF and in this study protocol.

Exclusion Criteria:

1. Participants who have previously received a TEAD inhibitor.
2. Participation in other therapeutic clinical studies within 28 days or 5 half-lives (whichever is shorter) prior to first dose of study treatment.
3. Anti-tumor therapy within 28 days or 5 half-lives (whichever is shorter) prior to first dose of study treatment.
4. Known active central nervous system (CNS) primary tumor or untreated CNS metastases.
5. As judged by the investigator, any evidence of severe or uncontrolled systemic diseases.
6. Unwillingness or unable to comply with the requirements of oral drug administration, or presence of a gastro-intestinal condition
7. Have prior or ongoing clinically significant illness, medical condition, surgical history, physical finding, laboratory abnormality or any other conditions that, in the investigator's opinion, would not be in the best interest of the participant; or that could alter the absorption, distribution, metabolism, or excretion of the study treatment; or impair the assessment of study result.
8. Currently receiving any of Strong inhibitors or inducers of P-gp, or Sensitive substrates of P-gp, CYP1A2, CYP2B6, and CYP3A4 that cannot be discontinued 14 days or 5 half-lives for inhibitors or substrates (whichever is shorter) prior to the first dose of study treatment.

Other protocol inclusion and exclusion criteria may apply.