Participants with MF and spliceosome mutations or ring sideroblasts present received 2 cycles (Cycles 1-2) of imetelstat 7.5 mg/kg, IV as 2-hour infusion on Day 1 of a 28-day cycle followed by maintenance therapy with the same regimen or the possibility of dose escalation to imetelstat 9.4 mg/kg weekly if response to the initial dose was insufficient up to 9 cycles in the Core Phase. Participants could receive imetelstat beyond Cycle 9 in the Extension Phase if they did not meet any of the withdrawal criteria, did not have disease progression and were receiving clinical benefit from treatment as determined by the investigator. Following treatment discontinuation, participants entered the Event Monitoring Phase for collection of survival status, disease status, and subsequent treatment information (Up to approximately 5.7 years).

Participants with MF without spliceosome mutations or ring sideroblasts present received 2 cycles (Cycles 1-2) of imetelstat 9.4 mg/kg, IV as 2-hour infusion on Day 1 of a 28-day cycle followed by maintenance therapy with the same regimen or imetelstat 7.5 mg/kg twice weekly on Days 1, 3 for 2 cycles of 28-day cycle (Cycles 3-4) followed by imetelstat 7.5 mg/kg 3-times-weekly on Days 1, 3, 5 of Cycles 5 and beyond of 28-day cycle up to 9 cycles in the Core Phase. Participants could receive imetelstat beyond Cycle 9 in the Extension Phase if they did not meet any of the withdrawal criteria, did not have disease progression and were receiving clinical benefit from treatment as determined by the investigator. Following treatment discontinuation, participants entered the Event Monitoring Phase for collection of survival status, disease status, and subsequent treatment information (Up to approximately 5.7 years).

Participants with either myelodysplastic syndromes/ myeloproliferative neoplasm (MDS/MPN) or MDS and spliceosome mutations or ring sideroblasts present received 2 cycles of 28-day cycle (Cycles 1-2) of imetelstat 7.5 mg/kg, IV as 2-hour infusion on Day 1 of a 28-day cycle followed by maintenance therapy with the same regimen or the possibility of dose escalation to imetelstat 9.4 mg/kg weekly if response to the initial dose was insufficient up to 9 cycles in the Core Phase. Participants could receive imetelstat beyond Cycle 9 in the Extension Phase if they did not meet any of the withdrawal criteria, did not have disease progression and were receiving clinical benefit from treatment as determined by the investigator. Following treatment discontinuation, participants entered the Event Monitoring Phase for collection of survival status, disease status, and subsequent treatment information (Up to approximately 5.7 years).

Spleen response per IWG-MRT criteria defined as baseline splenomegaly that is palpable at 5-10 cm, below the LCM, becomes not palpable, OR A baseline splenomegaly that is palpable at >10 cm, below the LCM, decreases by ≥50%. Baseline splenomegaly that is palpable at <5 cm, below the LCM, is not eligible for spleen response. Confirmation by Magnetic resonance imaging (MRI) or computerized tomography (CT) showing ≥35% spleen volume reduction is recommended (but not required). Spleen response was assessed only in participants with MF.

Transfusion dependency was defined by a history of at least 2 units of red blood cell transfusions in the last month for a hemoglobin level of less than 85 g/L that was not associated with clinically overt bleeding. A participant who was transfusion dependent at baseline was considered transfusion independent if the participant met either of the following conditions: Received no more than 1 unit of red blood cell transfusions in a rolling time interval of 30 days or more, and had a hemoglobin level increase over baseline more than 2 g/dL if participant baseline hemoglobin level was less than 85 g/L and received no transfusion. Anemia response per IWG-MRT Criteria- Transfusion-independent participants: a ≥20 g/L increase in hemoglobin level. Transfusion-dependent participants: becoming transfusion-independent. Data is reported separately for arms assessed as per the IWG-MRT criteria.

Transfusion dependency was defined by a history of at least 2 units of red blood cell transfusions in the last month for a hemoglobin level of less than 85 g/L that was not associated with clinically overt bleeding. A participant who was transfusion dependent at baseline was considered transfusion independent if the participant met either of the following conditions: Received no more than 1 unit of red blood cell transfusions in a rolling time interval of 30 days or more, and had a hemoglobin level increase over baseline more than 2 g/dL if participant baseline hemoglobin level was less than 85 g/L and received no transfusion. HI responses included: 1) Erythroid: Hgb increase ≥1.5 g/dL, Relevant reduction of RBC units transfusions by absolute number of >=4 RBC transfusions/8 week compared with pretreatment transfusion number in previous 8 week. Only RBC transfusions given for Hgb of ≤9.0 g/dL. Data is reported separately for arm assessed as per IWG criteria.

Time to response was defined as the duration from study Day 1 to the earliest date that a response is first documented. The response CI/CR/PR was assessed by IWG-MRT criteria.

Time to response was defined as the duration from study Day 1 to the earliest date that a response is first documented. Response was defined as achievement of a leukemic response (i.e. a clinically meaningful reduction in Blast cells). This was quantified as <5% peripheral blood and bone marrow blasts % that lasts for at least two months. Data for time to response is reported as per criteria of response assessment.

Time to response was defined as the duration from study Day 1 to the earliest date that a response is first documented. Response was defined as HI, PR or CR per IWG criteria. Data for time to response is reported as per criteria of response assessment.

DOR measured from time of initial response (CR/PR/CI) until documented PD or death whichever occurs first. If no PD/death occurs DOR is censored at last disease evaluation date for responders. CR:BM: <5%blasts; ≤Grade 1 MF, AND Peripheral blood:Hb≥100 g/L and <UNL;Neutrophil count≥1x10^9/L and <UNL;PLT count≥100x10^9/L and <UNL;<2% IMCs, AND Clinical:Resolution of disease symptoms;Spleen and liver not palpable;No evidence of EMH.PR:All CR criteria plus peripheral blood:Hb≥85 but <100g/L and <UNL;NC≥1x10^9/L and <UNL;PLTcount ≥50 but<100x10^9/L and<UNL;<2%IMCs. CI:achievement of anemia(≥20 g/L increase Hb level),spleen(baseline splenomegaly-palpable at 5-10cm,below LCM,becomes not palpable) or symptoms response(50% reduction in total symptom score) without PD(appearance of new splenomegaly- palpable[>= 5 cm below LCM) or increase in severity of anemia, thrombocytopenia or neutropenia. Data is reported separately for arms whose DOR was assessed per IWG-MRT. Kaplan-Meier method was used.](streamdown:incomplete-link)

DOR was measured from the time of initial response until documented disease progression or death whichever occurs first. If no PD/death occurs the DOR is censored at last disease evaluation date for responders. Response is defined as achievement of <5% peripheral blood and bone marrow blast % that lasts for at least two months. PD is the appearance of new splenomegaly that is palpable at least 5 cm below the LCM. Data is reported separately for arm whose DOR was assessed by a specific criterion. Kaplan-Meier method was used.

DOR: time of initial response (CR/PR/HI) until documented PD/death whichever occurs first. If no PD/death occurs DOR is censored at last disease evaluation date for responders. Data reported separately for arm assessed per IWG. Kaplan-Meier method was used.

OS was defined as the as the interval from Study Day 1 to the date of 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. Overall Survival was estimated by Kaplan-Meier method.

Participants with MF regardless of spliceosome mutation status or presence of ring sideroblasts received imetelstat 9.4 mg/kg, IV as 2-hour infusion on Days 1, 8, and 15 of 21-day cycle in Cycle 1 followed by 9.4 mg/kg on Day 1 of each 21-day cycle up to 9 cycles in the Core Phase. Participants could receive imetelstat beyond Cycle 9 in the Extension Phase if they did not meet any of the withdrawal criteria, did not have disease progression and were receiving clinical benefit from treatment as determined by the investigator. Following treatment discontinuation, participants entered the Event Monitoring Phase for collection of survival status, disease status, and subsequent treatment information (Up to approximately 5.7 years).

Participants with blast-phase MF/AML received imetelstat 9.4 mg/kg, IV as 2-hour infusion weekly on Days 1, 8, 15, 22 of a 28-day cycle up to 9 cycles in the Core Phase. Participants could receive imetelstat beyond Cycle 9 in the Extension Phase if they did not meet any of the withdrawal criteria, did not have disease progression and were receiving clinical benefit from treatment as determined by the investigator. Following treatment discontinuation, participants entered the Event Monitoring Phase for collection of survival status, disease status, and subsequent treatment information (Up to approximately 5.7 years).

Participants with MF and spliceosome mutations or ring sideroblasts present received 2 cycles (Cycles 1-2) of imetelstat 7.5 mg/kg, IV as 2-hour infusion on Day 1 of a 28-day cycle followed by maintenance therapy with the same regimen or the possibility of dose escalation to imetelstat 9.4 mg/kg weekly if response to the initial dose was insufficient up to 9 cycles in the Core Phase. Participants could receive imetelstat beyond Cycle 9 in the Extension Phase if they did not meet any of the withdrawal criteria, did not have disease progression and were receiving clinical benefit from treatment as determined by the investigator. Following treatment discontinuation, participants entered the Event Monitoring Phase for collection of survival status, disease status, and subsequent treatment information (Up to approximately 5.7 years).

Participants with MF without spliceosome mutations or ring sideroblasts present received 2 cycles (Cycles 1-2) of imetelstat 9.4 mg/kg, IV as 2-hour infusion on Day 1 of a 28-day cycle followed by maintenance therapy with the same regimen or imetelstat 7.5 mg/kg twice weekly on Days 1, 3 for 2 cycles of 28-day cycle (Cycles 3-4) followed by imetelstat 7.5 mg/kg 3-times-weekly on Days 1, 3, 5 of Cycles 5 and beyond of 28-day cycle up to 9 cycles in the Core Phase. Participants could receive imetelstat beyond Cycle 9 in the Extension Phase if they did not meet any of the withdrawal criteria, did not have disease progression and were receiving clinical benefit from treatment as determined by the investigator. Following treatment discontinuation, participants entered the Event Monitoring Phase for collection of survival status, disease status, and subsequent treatment information (Up to approximately 5.7 years).

Participants with either MDS/MPN or MDS and spliceosome mutations or ring sideroblasts present received 2 cycles of 28-day cycle (Cycles 1-2) of imetelstat 7.5 mg/kg, IV as 2-hour infusion on Day 1 of a 28-day cycle followed by maintenance therapy with the same regimen or the possibility of dose escalation to imetelstat 9.4 mg/kg weekly if response to the initial dose was insufficient up to 9 cycles in the Core Phase. Participants could receive imetelstat beyond Cycle 9 in the Extension Phase if they did not meet any of the withdrawal criteria, did not have disease progression and were receiving clinical benefit from treatment as determined by the investigator. Following treatment discontinuation, participants entered the Event Monitoring Phase for collection of survival status, disease status, and subsequent treatment information (Up to approximately 5.7 years).

Total of all reporting groups

ECOG Performance Status has 5 Scores.0= Fully active, able to carry on all predisease performance without restriction;1= Restricted in physically strenuous activity but ambulatory and able to carry out work on a light/sedentary nature,2= Ambulatory and capable of all self-care but unable to carry out any work activities. Up and about more than 50% of waking hours;3= Capable of only limited self-care; confined to bed/chair more than 50% of waking hours;4= Completely disabled. Cannot carry on any self-care.Totally confined to bed/chair;5= Dead. Number of participants for each score are reported.

Myelofibrosis subtypes included MDS/MPN or MDS, blast-phase myelofibrosis, primary myelofibrosis, post-ET myelofibrosis, and Post-PV myelofibrosis. Number of participants for each subtype are reported.

DIPSS stratifies primary myelofibrosis (PMF) into four risk categories (low, intermediate 1, intermediate 2, and high risk), based on 5 clinical factors; Age>65, Hemoglobin <10 grams per deciliter (gm/dL), Leukocytes >10 (9)/L, circulating blasts ≥1%, and constitutional symptoms. Participants for each status are reported. Only categories with data are reported.

Number analyzed is the number of participants with data available for DIPSS-Plus risk status.

Spliceosome mutations represent a group of acquired genetic alterations that affect both myeloid and lymphoid malignancies.

Number analyzed is the number of participants with data available for spliceosomal mutation status.

Spliceosome mutations represent a group of acquired genetic alterations that affect both myeloid and lymphoid malignancies. Spliceosomal mutation type included SF3B1, SRSF2 and U2AF1. Number of participants for each type are reported.

Number analyzed is the number of participants with data available for spliceosomal mutation type.

Ring sideroblasts are erythroblasts with iron-loaded mitochondria visualized by Prussian blue staining (Perls' reaction) as a perinuclear ring of blue granules. Refractory anemia with ring sideroblasts (RARS) is a type of MDS that is characterized by anemia and the presence of at least 15 percent ring sideroblasts in the marrow.

Number analyzed is the number of participants with data available for ringed sideroblasts present.

JAK2 V617F mutation is an acquired, somatic mutation present in the majority of participants with myeloproliferative cancer (myeloproliferative neoplasms) i.e. nearly 100% of participants with polycythemia vera and in about 50% of participants with essential thrombocytosis and primary myelofibrosis.

Number analyzed is the number of participants with data available for JAK2V617F Mutation.

Transfusion dependency was defined by a history of at least 2 units of red blood cell transfusions in the last month for a hemoglobin level of less than 85 grams per deciliter (g/dL) that was not associated with clinically overt bleeding.

For this pilot study, overall response was defined as achievement of a leukemic response (i.e. a clinically meaningful reduction in Blast cells). This was quantified as <5% peripheral blood and bone marrow blasts % that lasts for at least two months. Data is reported separately for this arm where response was assessed by this specific criterion.

All Treated Analysis Set included all participants who received at least one dose of study drug. Data is reported for Arm D: Imetelstat 9.4 mg/kg (Blastic MF/AML) participants whose overall response was assessed by a specific criterion.

OR: HI/PR/CR per IWG. CR: BM:≤5% myeloblasts (all cell lines normal maturation), Peripheral blood:Hgb ≥11g/dL, PLTs ≥100x10^9/L, Neutrophils ≥1.0x10^9/L, Blasts 0%. PR: All CR criteria if abnormal before treatment except- BM blasts decreased ≥50% over pretreatment but still >5%, Cellularity, morphology not relevant. HI responses:1) Erythroid: Hgb increase ≥1.5 g/dL, Relevant reduction of red blood cell(RBC) units transfusions by absolute ≥4 RBC transfusions/8 week (wk) compared with pretreatment transfusion number in previous 8 wk. Only RBC transfusions given for Hgb of ≤9.0 g/dL.2)PLTs:Absolute increase ≥30x10^9/L starting >20x10^9/L PLTs; Increase from <20x10^9/L to >20x10^9/L and by ≥100%; 3)Neutrophil: ≥100% increase, absolute increase >0.5x10^9/L; 4)Progression/relapse after HI:≥1 of following:≥50% decrement from maximum response levels in granulocytes/PLTs, Reduction in Hgb ≥1.5 g/dL,Transfusion dependence. Data is reported separately for arm whose response was assessed per IWG.

All Treated Analysis Set included all participants who received at least one dose of the study drug. Data is reported for Arm G: Imetelstat 9.4 mg/kg (MDS/MPN or MDS and spliceosome mutations or ring sideroblasts) participants whose overall response was assessed by IWG criteria.

TEAEs defined as those events that 1) occur on or 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 is considered study drug-related regardless of the start date of the event; or 3) any event that is present at baseline but worsens in severity or is subsequently considered drug-related by the investigator. Grade >=3 TEAE defined as events that are severe, life-threatening or disabling, or fatal and considered related to imetelstat as per National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE) Version 4.03. An AE was considered related to the study drug if the event was assessed by the investigator as probably or possibly related.

All Treated Analysis Set included all participants who received at least one dose of imetelstat.

Spleen response per IWG-MRT criteria defined as baseline splenomegaly that is palpable at 5-10 cm, below the LCM, becomes not palpable, OR A baseline splenomegaly that is palpable at >10 cm, below the LCM, decreases by ≥50%. Baseline splenomegaly that is palpable at <5 cm, below the LCM, is not eligible for spleen response. Confirmation by Magnetic resonance imaging (MRI) or computerized tomography (CT) showing ≥35% spleen volume reduction is recommended (but not required). Spleen response was assessed only in participants with MF.

Arms A, B, E and F: Eligible Analysis Set included subset of all participants who received at least one dose of study drug that excludes ineligible participants who did not satisfy each and every eligibility criteria for study entry. Arm D: All Treated Analysis Set included all participants who received at least one dose of imetelstat.

Transfusion dependency was defined by a history of at least 2 units of red blood cell transfusions in the last month for a hemoglobin level of less than 85 g/L that was not associated with clinically overt bleeding. A participant who was transfusion dependent at baseline was considered transfusion independent if the participant met either of the following conditions: Received no more than 1 unit of red blood cell transfusions in a rolling time interval of 30 days or more, and had a hemoglobin level increase over baseline more than 2 g/dL if participant baseline hemoglobin level was less than 85 g/L and received no transfusion. Anemia response per IWG-MRT Criteria- Transfusion-independent participants: a ≥20 g/L increase in hemoglobin level. Transfusion-dependent participants: becoming transfusion-independent. Data is reported separately for arms assessed as per the IWG-MRT criteria.

Arms A, B, E, F: Eligible Analysis Set included subset of all participants who received at least one dose of study drug that excludes ineligible participants who did not satisfy each and every eligibility criteria for study entry. Arm D: All Treated Analysis Set included all participants who received at least one dose of imetelstat, assessed per IWG-MRT.

Transfusion dependency was defined by a history of at least 2 units of red blood cell transfusions in the last month for a hemoglobin level of less than 85 g/L that was not associated with clinically overt bleeding. A participant who was transfusion dependent at baseline was considered transfusion independent if the participant met either of the following conditions: Received no more than 1 unit of red blood cell transfusions in a rolling time interval of 30 days or more, and had a hemoglobin level increase over baseline more than 2 g/dL if participant baseline hemoglobin level was less than 85 g/L and received no transfusion. HI responses included: 1) Erythroid: Hgb increase ≥1.5 g/dL, Relevant reduction of RBC units transfusions by absolute number of >=4 RBC transfusions/8 week compared with pretreatment transfusion number in previous 8 week. Only RBC transfusions given for Hgb of ≤9.0 g/dL. Data is reported separately for arm assessed as per IWG criteria.

All Treated Analysis Set included all participants who received at least one dose of study drug. Data is reported for Arm G: Imetelstat 9.4 mg/kg (MDS/MPN or MDS and spliceosome mutations or ring sideroblasts) participants whose transfusion independence (HI by erythroid response) was assessed by IWG criteria.

Time to response was defined as the duration from study Day 1 to the earliest date that a response is first documented. The response CI/CR/PR was assessed by IWG-MRT criteria.

Eligible Analysis Set included subset of all participants who received at least one dose of study drug that excludes ineligible participants who did not satisfy each and every eligibility criteria for study entry. Data is reported for arm groups (Arms A, B, E and F) whose overall response was assessed by IWG-MRT criteria. Only responders were analyzed for this outcome measure.

Time to response was defined as the duration from study Day 1 to the earliest date that a response is first documented. Response was defined as achievement of a leukemic response (i.e. a clinically meaningful reduction in Blast cells). This was quantified as <5% peripheral blood and bone marrow blasts % that lasts for at least two months. Data for time to response is reported as per criteria of response assessment.

All Treated Analysis Set included all participants who received at least one dose of the study drug. Only responders were analyzed for this outcome measure. Data is reported for Arm D: Imetelstat 9.4 mg/kg (Blastic MF/AML) participants whose overall response was assessed by a specific criterion.

Time to response was defined as the duration from study Day 1 to the earliest date that a response is first documented. Response was defined as HI, PR or CR per IWG criteria. Data for time to response is reported as per criteria of response assessment.

All Treated Analysis Set included all participants who received at least one dose of the study drug. Only responders were analyzed for this outcome measure. Data is reported for Arm G: Imetelstat 9.4 mg/kg (MDS/MPN or MDS and spliceosome mutations or ring sideroblasts) participants whose overall response was assessed by IWG criteria.

DOR measured from time of initial response (CR/PR/CI) until documented PD or death whichever occurs first. If no PD/death occurs DOR is censored at last disease evaluation date for responders. CR:BM: <5%blasts; ≤Grade 1 MF, AND Peripheral blood:Hb≥100 g/L and <UNL;Neutrophil count≥1x10^9/L and <UNL;PLT count≥100x10^9/L and <UNL;<2% IMCs, AND Clinical:Resolution of disease symptoms;Spleen and liver not palpable;No evidence of EMH.PR:All CR criteria plus peripheral blood:Hb≥85 but <100g/L and <UNL;NC≥1x10^9/L and <UNL;PLTcount ≥50 but<100x10^9/L and<UNL;<2%IMCs. CI:achievement of anemia(≥20 g/L increase Hb level),spleen(baseline splenomegaly-palpable at 5-10cm,below LCM,becomes not palpable) or symptoms response(50% reduction in total symptom score) without PD(appearance of new splenomegaly- palpable[>= 5 cm below LCM) or increase in severity of anemia, thrombocytopenia or neutropenia. Data is reported separately for arms whose DOR was assessed per IWG-MRT. Kaplan-Meier method was used.](streamdown:incomplete-link)

Eligible Analysis Set included subset of all participants who received at least one dose of study drug that excludes ineligible participants who did not satisfy each and every eligibility criteria for study entry. Data is reported for arm groups whose DOR was assessed by IWG-MRT criteria. Only responders were analyzed for this outcome measure.

DOR was measured from the time of initial response until documented disease progression or death whichever occurs first. If no PD/death occurs the DOR is censored at last disease evaluation date for responders. Response is defined as achievement of <5% peripheral blood and bone marrow blast % that lasts for at least two months. PD is the appearance of new splenomegaly that is palpable at least 5 cm below the LCM. Data is reported separately for arm whose DOR was assessed by a specific criterion. Kaplan-Meier method was used.

All Treated Analysis Set included all participants who received at least one dose of the study drug. Data is reported for Arm D: Imetelstat 9.4 mg/kg (Blastic MF/AML) participants whose DOR was assessed by a specific criterion. Only responders were analyzed for this outcome measure.

DOR: time of initial response (CR/PR/HI) until documented PD/death whichever occurs first. If no PD/death occurs DOR is censored at last disease evaluation date for responders. Data reported separately for arm assessed per IWG. Kaplan-Meier method was used.

All Treated Analysis Set included all participants who received at least one dose of the study drug. Data is reported for Arm G: Imetelstat 9.4 mg/kg (MDS/MPN or MDS and spliceosome mutations or ring sideroblasts) participants whose DOR was assessed by IWG criteria. Only responders were analyzed for this outcome measure.

OS was defined as the as the interval from Study Day 1 to the date of 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. Overall Survival was estimated by Kaplan-Meier method.

All Treated Analysis Set included all participants who received at least one dose of imetelstat.

Participants with MF regardless of spliceosome mutation status or presence of ring sideroblasts received imetelstat 9.4 mg/kg, IV as 2-hour infusion on Days 1, 8, and 15 of 21-day cycle in Cycle 1 followed by 9.4 mg/kg on Day 1 of each 21-day cycle up to 9 cycles in the Core Phase. Participants could receive imetelstat beyond Cycle 9 in the Extension Phase if they did not meet any of the withdrawal criteria, did not have disease progression and were receiving clinical benefit from treatment as determined by the investigator. Following treatment discontinuation, participants entered the Event Monitoring Phase for collection of survival status, disease status, and subsequent treatment information (Up to approximately 5.7 years).

Participants with blast-phase MF/AML received imetelstat 9.4 mg/kg, IV as 2-hour infusion weekly on Days 1, 8, 15, 22 of a 28-day cycle up to 9 cycles in the Core Phase. Participants could receive imetelstat beyond Cycle 9 in the Extension Phase if they did not meet any of the withdrawal criteria, did not have disease progression and were receiving clinical benefit from treatment as determined by the investigator. Following treatment discontinuation, participants entered the Event Monitoring Phase for collection of survival status, disease status, and subsequent treatment information (Up to approximately 5.7 years).

Participants with MF and spliceosome mutations or ring sideroblasts present received 2 cycles (Cycles 1-2) of imetelstat 7.5 mg/kg, IV as 2-hour infusion on Day 1 of a 28-day cycle followed by maintenance therapy with the same regimen or the possibility of dose escalation to imetelstat 9.4 mg/kg weekly if response to the initial dose was insufficient up to 9 cycles in the Core Phase. Participants could receive imetelstat beyond Cycle 9 in the Extension Phase if they did not meet any of the withdrawal criteria, did not have disease progression and were receiving clinical benefit from treatment as determined by the investigator. Following treatment discontinuation, participants entered the Event Monitoring Phase for collection of survival status, disease status, and subsequent treatment information (Up to approximately 5.7 years).

Participants with MF without spliceosome mutations or ring sideroblasts present received 2 cycles (Cycles 1-2) of imetelstat 9.4 mg/kg, IV as 2-hour infusion on Day 1 of a 28-day cycle followed by maintenance therapy with the same regimen or imetelstat 7.5 mg/kg twice weekly on Days 1, 3 for 2 cycles of 28-day cycle (Cycles 3-4) followed by imetelstat 7.5 mg/kg 3-times-weekly on Days 1, 3, 5 of Cycles 5 and beyond of 28-day cycle up to 9 cycles in the Core Phase. Participants could receive imetelstat beyond Cycle 9 in the Extension Phase if they did not meet any of the withdrawal criteria, did not have disease progression and were receiving clinical benefit from treatment as determined by the investigator. Following treatment discontinuation, participants entered the Event Monitoring Phase for collection of survival status, disease status, and subsequent treatment information (Up to approximately 5.7 years).

Participants with either MDS/MPN or MDS and spliceosome mutations or ring sideroblasts present received 2 cycles of 28-day cycle (Cycles 1-2) of imetelstat 7.5 mg/kg, IV as 2-hour infusion on Day 1 of a 28-day cycle followed by maintenance therapy with the same regimen or the possibility of dose escalation to imetelstat 9.4 mg/kg weekly if response to the initial dose was insufficient up to 9 cycles in the Core Phase. Participants could receive imetelstat beyond Cycle 9 in the Extension Phase if they did not meet any of the withdrawal criteria, did not have disease progression and were receiving clinical benefit from treatment as determined by the investigator. Following treatment discontinuation, participants entered the Event Monitoring Phase for collection of survival status, disease status, and subsequent treatment information (Up to approximately 5.7 years).