The purpose of this study is to explore safety and efficacy of varlitinib administered as monotherapy in Japanese subjects with advanced or metastatic solid tumors, and administered as combination with capecitabine in Japanese subjects with advanced or metastatic biliary tract cancer. Also to evaluate pharmacokinetics (PK) of varlitinib, capecitabine and its metabolite.

Inclusion Criteria:

• Study I: Subjects with a solid tumour (excluding haematologic tumors) in advanced or metastatic stage
• Study II: Subjects with advanced (unresectable) or metastatic biliary tract cancer (IHCC, EHCC, gallbladder cancer or ampullary carcinoma)

Exclusion Criteria:

• Subjects with concurrent multiple primary cancers.
• Subjects with a history of (non-infectious) pneumonitis that required steroids or current pneumonitis, or with a history of interstitial lung disease or current interstitial lung disease
• Subjects receiving proton pump inhibitors for established, symptomatic gastro-duodenal ulceration or gastroesophageal reflux disease (including the preventive use)