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

Inclusion Criteria:

1. Have histologically confirmed diagnosis of:

2. Part A: Locally advanced, metastatic, and/or unresectable solid tumor withdocumented ERBB2-activating alteration or NRG1 gene fusion in blood and/ortumor or HER2 overexpression in tumor

3. Part B: Locally advanced, metastatic, and/or unresectable NSCLC with documentedERBB2 mutation in blood and/or tumor

4. Part C: Locally advanced, metastatic and/or unresectable breast cancer withdocumented ERBB2 mutation in blood and/or tumor or HER overexpression in tumor

5. Have measurable disease per RECIST v1.1.

6. Eastern Cooperative Oncology Group (ECOG) Performance Status 0 to 1 for Part A. ForParts B and C, ECOG Performance Status must be 0 to 2.

7. Have clinically acceptable local laboratory screening results (clinical chemistryand hematology) within certain limits.

Exclusion Criteria:

1. Received small molecule chemotherapy or anticancer therapies or radiotherapy withincertain timeframes before first dose of study drug.

2. Major surgeries (eg, craniotomy and thoracotomy) within 4 weeks of the first dose ofstudy drug.

3. Treatment with palliative focal radiotherapy (cranial or extracranial) (eg,stereotactic radiosurgery or intensity-modulated radiation therapy) ≤2 weeks beforethe first dose of study drug; treatment with whole-brain radiotherapy ≤4 weeksbefore the first dose of study drug.

4. Clinically significant cardiac disease.

5. Resolution of toxicities from prior therapy to ≤Grade 1 (or baseline), includingresolution of clinically significant laboratory abnormalities, before the first doseof study drug.

6. Restrictions on use of corticosteroid use to manage neurologic symptoms in differentparts of the study.