• Able to understand and comply with the study procedures, understand the risks involved in the study, and provide legally effective informed consent before the first study-specific procedure; specifically able to comply with the PK assessment schedule during the first treatment cycle.

• Participants must have histologically or cytologically confirmed malignancy as follows:

‣ A solid tumor that is metastatic or unresectable and for which standard life-prolonging measures are not available.

⁃ AML or MDS.

⁃ A hematologic malignancy other than AML or MDS for which standard life-prolonging measures are not available.

• For participants with AML/MDS only:

‣ Cytologically or histologically confirmed diagnosis of AML (except M3 acute promyelocytic leukemia) or MDS according to the 2008 World Health Organization (WHO) classification

⁃ Participants with frontline MDS or treatment naïve AML not suitable for induction therapy (e.g., age \>75 years, Eastern Cooperative Oncology Group \[ECOG\] performance ≥2, severe pulmonary disorder, total bilirubin 1.5 X upper limit of normal \[ULN\]);

⁃ Platelet count ≥25,000/per microliter (μL);

⁃ Absolute neutrophil count (ANC) ≥100 cells/μL.

• For participants with only hematologic malignancies other than AML or MDS, or solid tumors:

‣ Platelet count ≥100,000/μL;

⁃ ANC ≥1000 cells/μL.

• ECOG performance status of 0 to 2.

• Adequate hepatic function defined as:

‣ Total or direct bilirubin ≤1.5X upper limit of normal (ULN);

⁃ Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤2.5X ULN.

• Participants must have a body surface area (BSA)-adjusted CLcr using to the Cockcroft-Gault equation:

‣ Participants without renal impairment (Group B): ≥80 mL/min/1.73m\^²;

⁃ Participants with severe renal impairment (Group A): \<30 mL/min/1.73m\^², not requiring dialysis;

⁃ CLcr must be stable with \<30% deviation allowed from Screening to Baseline (Day -1). Participants shifting outside the prospected renal function category (normal renal function or severe renal function) at Baseline need to be agreed by Taiho medical expert whether they are allowed to remain in the original category that was assessed at Screening.

• No major surgery within 30 days of first administration of oral decitabine and cedazuridine.

• Life expectancy of at least 3 months.

• Women of childbearing potential (according to recommendations of the Clinical Trial Facilitation Group) must not be pregnant or breastfeeding and must have a negative pregnancy test at Screening.

• Women of childbearing potential must agree to practice 1 highly effective contraceptive measure of birth control with low user dependency and must agree not to become pregnant for 6 months after completing treatment.

• Male participants with female partners of childbearing potential must agree to use a male condom and advise his partner to practice 1 highly effective contraceptive measure of birth control (user dependent or with low user dependency) and must agree not to father a child while receiving treatment with oral decitabine and cedazuridine for at least 3 months after completing treatment.