Studie zur Beurteilung von Imetelstat (GRN163L) bei Patienten mit niedrigem oder mittlerem IPSS-1-Risiko mit myelodysplastischem Syndrom (MDS).

Drug: Imetelstat;Drug: Placebo

Gender: All
Maximum age: N/A
Minimum age: 18 Years
Inclusion Criteria:

- Man or woman greater than or equal to (>=) 18 years of age

- Diagnosis of myelodysplastic syndrome (MDS) according to World Health Organization
(WHO) criteria confirmed by bone marrow aspirate and biopsy within 12 weeks prior to
Cycle 1 Day 1 (C1D1) (Part 1) or randomization [Part 2 (Main Study)]. In Part 2
(Ventricular Repolarization Substudy), diagnosis of MDS or
myelodysplastic/myeloproliferative neoplasm with ring sideroblasts and
thrombocytosis (MDS/MPN-RS-T) according to WHO criteria confirmed by bone marrow
aspirate and biopsy within 12 weeks prior to C1D1

- International Prognostic Scoring System (IPSS) low Risk or intermediate-1 risk MDS

- Red blood cell (RBC) transfusion dependent, defined as requiring at least 4 RBC
units transfused over an 8-week period during the 16 weeks prior to Study Entry;
pre-transfusion hemoglobin (Hb) should be less than or equal to 9.0 gram per
deciliter (g/dL) to count towards the 4 units total

- Eastern Cooperative Oncology Group (ECOG) performance status 0, 1 or 2

Exclusion Criteria:

- Participant has known allergies, hypersensitivity, or intolerance to imetelstat or
its excipients

- Participant has received an investigational drug or used an invasive investigational
medical device within 30 days prior to Study Entry or is currently enrolled in an
investigational study

- Prior treatment with imetelstat

- Have received corticosteroids greater than (>) 30 milligram per day (mg/day)
prednisone or equivalent, or growth factor treatment within 4 weeks prior to study
entry

- Has received an erythropoiesis-stimulating agent (ESA) or any chemotherapy,
immunomodulatory, or immunosuppressive therapy within 4 weeks prior to study entry
(8 weeks for long-acting ESAs)

- Part 2 (Main Study): a) Prior treatment with a hypomethylating agent (example [eg],
azacitidine, decitabine); b) Prior treatment with lenalidomide

Additional Exclusion Criteria for Part 2 (Ventricular Repolarization Substudy)

- Concurrent therapy with medications known to prolong the QT interval and have been
associated with Torsade de pointes arrhythmia (TdP)

- Cardiac function abnormalities on screening ECG as follows:

- Resting heart rate outside of 50 to 100 beats per minute

- QTcF >470 millisecond (msec) (or QTcF >490 msec in the presence of a right
bundle branch block or ventricular conduction delay [QRS >119 msec]),
determined by central assessment based on the average value of a triplicate set
of ECGs

- Diagnosed or suspected congenital long QT syndrome

- Family history of sudden unexpected death from cardiac-related causes if
indicative of a pathogenic mutation of cardiac ion channels

- Family history of congenital long QT syndrome

- History of Mobitz II second degree or third degree heart block

- Implantable pacemaker or automatic implantable cardioverter defibrillator

- Complete left bundle branch block

- Chronic or persistent atrial arrhythmia including atrial fibrillation and
atrial flutter

- History or presence of clinically relevant heart rhythm disturbances including
atrial, junctional, re-entry, and ventricular tachycardia

- Unusual T-wave morphology (i.e., bifid T-wave) likely to interfere with QT
measurements

- History or evidence for any of the following: severe or unstable angina, myocardial
infarction, symptomatic congestive heart failure, arterial or venous thromboembolic
events (example, pulmonary embolism, cerebrovascular accident including transient
ischemic attacks) within 12 months prior to Cycle 1 Day 1, New York Heart
Association (NYHA) Class II to IV heart disease

- Presence of uncontrolled hypertension (persistent systolic blood pressure [BP] =160
mmHg or diastolic BP =100 mmHg). Participants with a history of hypertension are
permitted, provided that BP is controlled to within these limits by
anti-hypertensive treatment

- Any skin condition likely to interfere with electrocardiographic electrode placement
or adhesion

- History of thoracic surgery likely to cause abnormality of the electrical conduction
through thoracic tissues