Study to Evaluate Imetelstat (GRN163L) in Participants With International Prognostic Scoring System (IPSS) Low or Intermediate-1 Risk Myelodysplastic Syndrome (MDS)

Percentage of participants without any RBC transfusion during any consecutive 8 weeks (56 days) starting from Study Day 1 until subsequent anti-cancer therapy if any were reported. Study Day 1 is defined as the day of the first dose for participants enrolled in Phase 2. The 95% confidence interval (CI) was calculated using Clopper-Pearson method. Percentages were rounded off to the nearest single decimal place.

Percentage of participants without any RBC transfusion during any consecutive 8 weeks (56 days) starting from Study Day 1 until subsequent anti-cancer therapy if any were reported. Study Day 1 is defined as the day of the first dose for participants enrolled in Phase 2. The 95% confidence interval (CI) was calculated using Clopper-Pearson method. Percentages were rounded off to the nearest single decimal place.

Percentage of participants without any RBC transfusion during any consecutive 8 weeks (56 days) starting from Study Day 1 until subsequent anti-cancer therapy if any were reported. Study Day 1 is defined as the day of the first dose for participants enrolled in Phase 2. The 95% CI was calculated using Clopper-Pearson method. Percentages were rounded off to the nearest single decimal place.

TEAEs were defined as those events that 1) occurred after the first dose of study drug, through the treatment phase, and for 30 days following the last dose of study drug or until subsequent anti-cancer therapy if earlier; 2) any event that was considered study drug-related regardless of the start date of the event; or 3) any event that was presented at baseline but worsened in severity or was subsequently considered drug-related by the investigator. Serious TEAEs are any TEAEs that result in death, is life-threatening, requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect, is a suspected transmission of any infectious agent via a medicinal product, is medically important. Any clinically significant vital sign measurements, clinical laboratory values, and electrocardiogram (ECG) findings were reported as TEAEs. TEAEs included both serious and non-serious TEAEs.

Percentage of participants without any RBC transfusion during any consecutive 24 weeks (168 days) starting from Study Day 1 until subsequent anti-cancer therapy if any were reported. Study Day 1 is defined as the day of the first dose for participants enrolled in Phase 2 and the day of randomization for participants enrolled in Phase 3. The 95% CI was calculated using Clopper-Pearson method. Percentages were rounded off to the nearest single decimal place.

Time to 8-week RBC TI was defined as the interval from Study Day 1 to the first day of the first 8-week RBC TI period.

Time to 24-week RBC TI was defined as the interval from Study Day 1 to the first day of the first 24-weeks RBC TI period.

Duration of RBC TI was defined as the first day of the longest RBC TI period to the date of the first RBC transfusion after the TI period started. The 95% CI was based on Kaplan-Meier product limit estimates.

As per IWG Response Criteria 2006: HI-E was defined as a hemoglobin (Hb) increase by greater than or equal to (≥)1.5 grams per deciliter (g/dL) relevant reduction of units of RBC transfusions by an absolute number of at least 4 RBC transfusion units/8 weeks compared with the pretreatment transfusion number in the previous 8 weeks. Only RBC transfusions given for a Hb of less than or equal to (≤)9 g/dL pretreatment were counted in the RBC transfusion response evaluation. The 95% CI was calculated using Clopper-Pearson method. Percentages were rounded off to the nearest single decimal place.

As per the IWG Response Criteria 2006, CR was defined as Bone marrow: ≤5% myeloblasts with normal maturation of all cell lines; Peripheral blood (PB): Hb ≥11 g/dL; platelets ≥100 x 10^9/dL; neutrophils ≥1.0 x 10^9/liter; blasts: 0%. PR was defined as Bone marrow: ≤5% myeloblasts and decrease by ≥50% over pretreatment; cellularity and morphology not relevant. mCR was defined as Bone marrow: ≤5% myeloblasts and decreased by ≥50% over pre-treatment PB. Percentages were rounded off to the nearest single decimal place. All participants in Phase 2 were evaluated by the Investigator for CR/PR/mCR regardless of bone marrow blasts at baseline.

As per the IWG Response Criteria 2006, CR was defined as Bone marrow: ≤5% myeloblasts with normal maturation of all cell lines; PB: Hb ≥11 g/dL; platelets ≥100 x 10^9/dL; neutrophils ≥1.0 x 10^9/liter; blasts: 0%. PR was defined as Bone marrow: ≤5% myeloblasts and decrease by ≥50% over pretreatment; cellularity and morphology not relevant. mCR was defined as Bone marrow: ≤5% myeloblasts and decreased by ≥50% over pre-treatment PB. CR, PR and mCR were assessed by IRC in Phase 3 and participants were required to fit at least one of the following criteria (participants with >5% baseline blasts per central pathology reviewer assessment; participants with CR, PR, mCR, or cytogenetic response as assessed by the investigator) and have at least one post-baseline assessment.

OS was defined as the interval from Study Day 1 to death from any cause. Survival time of living participants was censored on the last date a participant is known to be alive or lost to follow-up. The Kaplan-Meier method was used to estimate overall survival.

Progression free survival was defined as the time interval from study Day 1 to the first date of disease progression or death from any cause, whichever occurs first. Disease progression as per IWG criteria was defined as: at least one of the following: at least 50 % decrement from maximum response levels in granulocytes or platelets; reduction in hemoglobin by ≥1.5 g/dL; transfusion dependence.

Time to progression to AML was defined as the interval from Study Day 1 to the date of AML diagnosis. Participants who did not progress to AML and were still alive at the cutoff date for the analysis or who withdrew from the study (withdrawal of consent or lost to follow-up), data was censored at the date of the last disease evaluation.

Amount of RBC transfusions for 8-week interval was defined as the total number of RBC transfusion units in a given 8-week interval during study. The best 8-week interval is a post-baseline 8-week interval where the participant had the fewest post-Study Day 1 RBC transfusion units. A valid 8-week period must start before the date of last dose of study drug + 30 days or end of treatment (EOT) visit whichever occurs first and ends before the first transfusion in post-treatment follow-up or the first day of subsequent anti-cancer therapy whichever occurs first.

Relative percent change in RBC transfusions per 8-week = (amount of RBC transfusions per 8-week - prior RBC transfusion burden) / prior RBC transfusion burden multiplied by 100%. Prior RBC transfusion burden was defined as the maximum number of RBC units transfused over any consecutive 8 weeks prior to study entry.

Percentage of participants who received any myeloid growth factors starting from Study Day 1 were reported. Percentages were rounded off to the nearest single decimal place.

Duration of myeloid growth factor administered starting from Study Day 1 was reported.

As pre-specified in the statistical analysis plan (SAP), participants in the imetelstat sodium arm group of Phase 2 and Phase 3 were pooled for pharmacokinetic (PK) data collection and analyses in this outcome measure. PK parameters were determined by population PK model.

As pre-specified in the statistical analysis plan (SAP), participants in the imetelstat sodium arm group of Phase 2 and Phase 3 were pooled for PK data collection and analyses in this outcome measure. PK parameters were determined by population PK model.

As pre-specified in the SAP, participants in the imetelstat sodium arm group of Phase 2 and Phase 3 were pooled for immunogenicity data collection and analyses in this outcome measure. Percentages were rounded off to the nearest single decimal place.

Outpatient medical encounters included various sites of care: a) emergency room (ER) visits, b) hospital outpatient visits, c) home care visit, d) visit to lab, e) visit to doctor's office, f) other visits. Percentages were rounded off to the nearest single decimal place.

Hospitalization included any medical encounter defined as hospice, hospital inpatient department, and intensive care unit (ICU). Hospitalizations without end dates were not counted in the calculation of length of stay. If any participant had multiple readmissions, duration was calculated as the sum of all hospital stays.

Baseline was defined as the mean of the measured ECG intervals collected at 3 time points (-1 hour, -0.5 hour, and 0 hour) prior to treatment administration on Cycle 1 Day 1 (Cycle length= 28 days)

An adverse event (AE) was any untoward medical occurrence in a clinical study participant administered a medicinal product. An AE does not necessarily have a causal relationship with the treatment. An AE can therefore be any unfavorable and unintended sign (including an abnormal finding), symptom, or disease temporally associated with the use of a medicinal product, whether or not related to that medicinal product. AEs included clinically significant vital signs measurements, clinical laboratory values and electrocardiograms (ECGs) changes.

Progression free survival will be assessed as the time interval from the end of the Phase 3 study until death, withdrawal of consent, study termination, or until a subject is lost to follow-up. As per IWG criteria disease progression is defined as: at least one of the following: at least 50 percent (%) decrement from maximum response levels in granulocytes or platelets; reduction in hemoglobin by greater than or equal to ≥1.5 g/dL; transfusion dependence.