• At least 18 years of age.

• Locally advanced, unresectable, or metastatic solid tumors based on most recent imaging.

• HER2 expression.

• ECOG performance status of 0-1.

• Must provide an adequate FFPE tumor sample to centrally determine HER2 status and other correlatives.

• Has measurable target disease assessed by the investigator based on RECIST 1.1.

• Adequate organ function and bone marrow within 14 days before enrollment.

• Contraceptive use by males or females should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies.

• Capable of giving signed informed consent.

• Provision of signed and dated written ICF prior to mandatory study-specific procedures, sampling, or analyses.

• Evidence of post-menopausal status or negative serum pregnancy test for females of childbearing potential who are sexually active with a non-sterilized male partner.