• Male or female 18 years or older.

• Patients must have a diagnosis of myelodysplastic syndrome (MDS), or MDS / myeloproliferative neoplasm (MPN), chronic myelomonocytic leukemia (CMML) as defined by the World Health Organization (WHO) criteria.

• Intermediate, high, or very-high risk by the Revised International Prognostic Scoring System (IPSS-R).

• Eastern Cooperative Oncology Group (ECOG) performance status of 0-2 (0-3 if performance status is considered due to MDS).

• Patient must have a body weight of at least 50 kg.

• Patient must meet the following screening clinical laboratory values as specified below:

• a. Hematologic: white blood cell (count) (WBC) below 30 x 109/L. Hydroxyurea can be used to achieve this level b. Hepatic: i. Total bilirubin ≤1.5 x upper limit of normal (ULN). Patients with Gilbert's syndrome can enroll if conjugated bilirubin is within normal limits.

• ii. Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤3 x ULN.

• c. Renal: Serum creatinine ≤1.5 x ULN.

• Patient is able to swallow oral medications.

• Female subjects who:

∙ Are postmenopausal for at least one year before the screening visit, OR

‣ Are surgically sterile, OR

‣ If they are of childbearing potential:

• i. Agree to practice one highly effective method and one additional effective (barrier) method of contraception, at the same time, from the time of signing the informed consent through six months after the last dose of study drug (female and male condoms should not be used together), OR ii. Agree to practice true abstinence, when this is in line with the preferred and usual lifestyle of the subject. (Periodic abstinence \[e.g., calendar, ovulation, symptothermal, post-ovulation methods\], withdrawal, spermicides only, and lactational amenorrhea are not acceptable methods of contraception).

• iii. Agree to not to donate or freeze egg(s) during the course of this study or within 180 days after receiving their last dose of study drug.

• Male subjects, even if surgically sterilized (i.e., status post vasectomy), who:

∙ Agree to practice effective barrier contraception during the entire study treatment period from the time of signing the informed consent through and through six months after the last dose of study drug (female and male condoms should not be used together), OR

‣ Agree to practice true abstinence, when this is in line with the preferred and usual lifestyle of the subject. (periodic abstinence \[e.g., calendar, ovulation, symptothermal, post-ovulation methods for the female partner\] withdrawal, spermicides only, and lactational amenorrhea are not acceptable methods of contraception.)

‣ Agree to not to donate or freeze sperm during the course of this study or within 180 days after receiving their last dose of study drug.

⁃ Ability to provide informed consent or have a legally authorized representative provide consent.