From randomization until BICR confirmed progressive disease or death due to any cause, whichever occurs first

Adverse events (AEs) will be graded according to the CTCAE v5.0

Adverse events (AEs) will be graded according to the CTCAE v5.0

Infection rates will be summarized by classification and will include a count and proportion.

AEs will be graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) version 5.0. All reported AEs will be coded using the Medical Dictionary for Regulatory Activities (MedDRA), using the latest version.

SAEs related to study drug will be collected irrespective of the time of onset. AEs will be graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) version 5.0.

QT interval, using Fridericia's formula \[QTcF\], to average QTc interval \> 480 to 500msec (Grade 2) or worse, as seen during an ECG. This is classified as an Adverse Event of Special Interest (AESI) for this study.

ECOG PS scoring consists of Grade 0 - 5, with 0 being the patient is fully active and 5 being the patient is dead. Descriptive statistics of ECOG PS over time will be summarized by frequency. Shift tables may be provided for ECOG PS from baseline to worst value of post-baseline assessments.

Total number of AEs that result in discontinuation from treatment or death. AEs will be graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) version 5.0.

Listing of all laboratory hematology, coagulation, and chemistry data with values flagged as abnormal to show the corresponding NCI-CTCAE grades and the classifications relative to the laboratory normal ranges.

Abnormalities will be classified by using National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) version 5.0 grading scale or the low/normal/high classifications based on laboratory normal ranges. Shift tables using NCI-CTCAE grades to compare baseline to the worst on-treatment value will be used. For laboratory tests, including hematology, coagulation, and chemistry, where NCI-CTCAE grades are not defined, shift tables using the low/normal/high \[low and high\] classification to compare baseline to the worst on treatment may be generated. On-treatment is considered from Day 1 of Cycle 1 through 28 days after the last dose.

Vital signs include systolic and diastolic blood pressure, heart rate, respiratory rate, and temperature.

On-treatment is considered from Day 1 of Cycle 1 through 28 days after the last dose. Vital signs include systolic and diastolic blood pressure, heart rate, respiratory rate, and temperature.

Proportion of subjects who are alive and progression-free (using RECIST v1.1) at 6 months after Day 1 (C1D1) per Independent Radiology Center (IRC)

Will be evaluated according to a modified version of the IWG 2006 Criteria for Hematologic Improvement for patients with MDS on clinical trials * Erythroid response (pretreatment, \<11 g/DL) * Hemoglobin (Hgb) increase by ≥1.5 g/dL * Relevant reduction of units of RBC transfusions by an absolute number of at least 4 RBC transfusions/8 weeks, compared with the pretreatment transfusion number in the previous 8 weeks. Only RBC transfusions given for an Hgb of ≤9.0 g/dL pretreatment will count in the RBC transfusion response evaluation * Platelet response (pretreatment, \<100 x 10\^9/L) * Absolute increase of ≥30 × 10\^9/L for patients starting with \>20 × 10\^9/L platelets. * Increase from \<20 × 10\^9/L to \>20 × 10\^9/L and by at least 100%. * Neutrophil response (pretreatment, \<1.0 x 10\^9/L): * At least 100% increase and an absolute increase \>0.5 × 10\^9/L. If pegfilgrastim being used prior to initiation of study, define response as no longer requiring pegfilgrastim to maintain ANC \>500.