A Study of a Selective ERBB2 Inhibitor (CGT4255), in Patients With Advanced Solid Tumors

Inclusion Criteria

• Have histologically confirmed diagnosis of:
• Part A: Locally advanced, metastatic, and/or unresectable solid tumor with documented ERBB2-activating alteration or NRG1 gene fusion in blood and/or tumor or HER2 overexpression in tumor
• Part B: Locally advanced, metastatic, and/or unresectable NSCLC with documented ERBB2 mutation in blood and/or tumor
• Part C: Locally advanced, metastatic and/or unresectable breast cancer with documented ERBB2 mutation in blood and/or tumor or HER overexpression in tumor
• Have measurable disease per RECIST v1.1.
• Eastern Cooperative Oncology Group (ECOG) Performance Status 0 to 1 for Part A. For Parts B and C, ECOG Performance Status must be 0 to 2.
• Have clinically acceptable local laboratory screening results (clinical chemistry and hematology) within certain limits.

Exclusion Criteria

• Received small molecule chemotherapy or anticancer therapies or radiotherapy within certain timeframes before first dose of study drug.
• Major surgeries (eg, craniotomy and thoracotomy) within 4 weeks of the first dose of study drug.
• Treatment with palliative focal radiotherapy (cranial or extracranial) (eg, stereotactic radiosurgery or intensity-modulated radiation therapy) ≤2 weeks before the first dose of study drug; treatment with whole-brain radiotherapy ≤4 weeks before the first dose of study drug.
• Clinically significant cardiac disease.
• Resolution of toxicities from prior therapy to ≤Grade 1 (or baseline), including resolution of clinically significant laboratory abnormalities, before the first dose of study drug.
• Restrictions on use of corticosteroid use to manage neurologic symptoms in different parts of the study.