A Study of TAS-116 in Patients With Solid Tumors

Inclusion Criteria: 1. Male or females with an age ≥ 18 years (≥ 20 years in Japan) 2. Patients with histological- or cytological-confirmed, advanced unresectable breast, gastric, or non-small cell lung cancer, who have progressed on (or not been able to tolerate) standard therapy or for whom no standard anticancer therapy exists. a. Part C: Only the following subtype of tumors with the molecular/genetic alterations will be enrolled: HER2 positive MBC Advanced NSCLC, harboring EGFR mutations after progression on osimertinib Advanced NSCLC, harboring ALK translocations after treatment with alectinib or at least 2 ALK inhibitors 3. Has At least one measurable lesion as defined by RECIST criteria 4. Is able to take medications orally (e.g., no feeding tube). 5. Is able to agree to and sign informed consent and to comply with the protocol 6. Has adequate organ function Exclusion Criteria: 1. Has a serious illness or medical condition(s) 2. Has received treatment with any prescribed treatments within specified time frames prior to study drug administration 3. Significant ophthalmologic abnormality, 4. Impaired cardiac function or clinically significant cardiac disease