Safety and Pharmacokinetics of Tucatinib (MK-7119) in Chinese Participants With Cancer (MK-7119-002)

Inclusion Criteria: * Histologically or cytologically confirmed HER2+ advanced breast cancer, gastric or GEC, and colorectal cancer * Have progressed at least one previous therapeutic regimen and either no longer are candidates for standard therapy, have no standard therapy available, or choose not to pursue standard therapy * Have a performance status of 0 or 1 on the Eastern Cooperative Oncology Group (ECOG) Performance within 7 days prior to allocation * Has life expectancy \>6 months in the opinion of the investigator * Have measurable disease per Response Evaluation Criteria in Solid Tumours (RECIST) 1.1 as assessed by the local site investigator/radiologist * Must test negative for hepatitis B surface antigen (HBsAg) * If there is a history of hepatitis C virus (HCV) infection, has undetectable HCV viral load at screening * For males, agree to be abstinent from heterosexual intercourse, or agree to use acceptable contraception, for the duration of study and 1 week after * For females, is not pregnant or breastfeeding AND one of the following applies: * Is not a woman of childbearing potential (WOCBP) * Is a WOCBP and uses highly effective contraception and is not pregnant Exclusion Criteria: * History of prior cancer within \<3 year, except for adequately treated basal cell or squamous cell carcinoma of the skin, cervical cancer in situ, or other in situ carcinomas which needs discussion between the investigator and the Sponsor * Participants with leptomeningeal dise…