Trial Outcomes & Findings for A Study to Determine the Efficacy and Safety of Luspatercept in Adults With Non Transfusion Dependent Beta (β)-Thalassemia (NCT NCT03342404)

Last Updated: 2023-12-20

Results Overview

Erythroid Response is defined as an increase from baseline ≥1.0 g/dL in mean of hemoglobin values over a continuous 12-week interval from Weeks 13 to 24 of treatment in the absence of transfusions. Baseline hemoglobin (Hb) is the average of 2 or more Hb measurements at least 1 week apart within 4 weeks prior to Dose 1.

Recruitment status

COMPLETED

Study phase

PHASE2

Target enrollment

145 participants

Primary outcome timeframe

From Week 13 to Week 24 of study treatment

Results posted on

2023-12-20

Participant Flow

Participant milestones

Participant milestones
Measure	Luspatercept Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Blinded Treatment Phase STARTED	96	49
Blinded Treatment Phase COMPLETED	68	18
Blinded Treatment Phase NOT COMPLETED	28	31
Open-Label Phase STARTED	0	38
Open-Label Phase COMPLETED	0	27
Open-Label Phase NOT COMPLETED	0	11

Reasons for withdrawal

Reasons for withdrawal
Measure	Luspatercept Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Blinded Treatment Phase Withdrawal by Subject	17	10
Blinded Treatment Phase Lack of Efficacy	2	17
Blinded Treatment Phase Adverse Event	5	4
Blinded Treatment Phase Noncompliance with study drug	1	0
Blinded Treatment Phase Other reasons	1	0
Blinded Treatment Phase Physician Decision	1	0
Blinded Treatment Phase Death	1	0
Open-Label Phase Lost to Follow-up	0	1
Open-Label Phase Other reasons	0	1
Open-Label Phase Adverse Event	0	3
Open-Label Phase Withdrawal by Subject	0	6

Baseline Characteristics

A Study to Determine the Efficacy and Safety of Luspatercept in Adults With Non Transfusion Dependent Beta (β)-Thalassemia

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	Luspatercept n=96 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=49 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.	Total n=145 Participants Total of all reporting groups
Age, Continuous	39.3 Years STANDARD_DEVIATION 13.24 • n=5 Participants	41.1 Years STANDARD_DEVIATION 11.90 • n=7 Participants	39.9 Years STANDARD_DEVIATION 12.79 • n=5 Participants
Sex: Female, Male Female	56 Participants n=5 Participants	26 Participants n=7 Participants	82 Participants n=5 Participants
Sex: Female, Male Male	40 Participants n=5 Participants	23 Participants n=7 Participants	63 Participants n=5 Participants
Ethnicity (NIH/OMB) Hispanic or Latino	2 Participants n=5 Participants	1 Participants n=7 Participants	3 Participants n=5 Participants
Ethnicity (NIH/OMB) Not Hispanic or Latino	94 Participants n=5 Participants	48 Participants n=7 Participants	142 Participants n=5 Participants
Ethnicity (NIH/OMB) Unknown or Not Reported	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants
Race/Ethnicity, Customized Race · Asian	31 Participants n=5 Participants	13 Participants n=7 Participants	44 Participants n=5 Participants
Race/Ethnicity, Customized Race · White	59 Participants n=5 Participants	28 Participants n=7 Participants	87 Participants n=5 Participants
Race/Ethnicity, Customized Race · Other	6 Participants n=5 Participants	8 Participants n=7 Participants	14 Participants n=5 Participants

PRIMARY outcome

Timeframe: From Week 13 to Week 24 of study treatment

Population: All treated participants. Placebo participants are assessed up to crossing over to luspatercept. The luspatercept group does not include placebo participants who crossed over to luspatercept.

Outcome measures

Outcome measures
Measure	Luspatercept n=96 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=49 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Percentage of Participants Achieving Erythroid Response (Week 13 to Week 24)	77.1 Percent of Participants Interval 67.4 to 85.0	0.0 Percent of Participants Interval 0.0 to 7.3

SECONDARY outcome

Timeframe: Baseline and over a continuous 12 week period (from week 13 through week 24)

Population: All treated participants with available measurements at Baseline and from Week 13 to Week 24. Placebo participants are assessed up to crossing over to luspatercept. The luspatercept group does not include placebo participants who crossed over to luspatercept.

The NTDT-PRO assesses the severity of anemia-related symptoms with a daily recall of symptoms composed of 6 items: 1. Tiredness (lack of energy) when not doing physical activity 2. Tiredness when doing physical activity 3. Weakness (lack of strength) when not doing physical activity 4. Weakness when doing physical activity 5. Shortness of breath when not doing physical activity 6. Shortness of breath when doing physical activity. The Tiredness/Weakness (T/W) domain score is the average score of items 1 through 4 above. T/W domain score ranges from 0 (best outcome, no tiredness/weakness) to 10 (worst outcome, extreme tiredness/weakness). Weekly T/W Scores are the average of daily scores for that week. The mean of weekly scores over a continuous 12-week period (from Week 13 to Week 24) are compared to the T/W Domain Score at baseline. Baseline is defined as the last value taken on or before the first dose of study drug administered in Week 13.

Outcome measures

Outcome measures
Measure	Luspatercept n=94 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=48 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Mean Change From Baseline in Non-Transfusion Dependent β-thalassemia-Patient Reported Outcome (NTDT-PRO) Tiredness and Weakness (T/W) Domain Score (Week 13 to Week 24)	-0.68 Score on a scale Standard Error 0.176	-0.20 Score on a scale Standard Error 0.240

SECONDARY outcome

Timeframe: Baseline and over a continuous 12 week period (from week 13 through week 24)

Population: All treated participants with available measurements at Baseline and From Week 13 to Week 24. Placebo participants are assessed up to crossing over to luspatercept. The luspatercept group does not include placebo participants who crossed over to luspatercept.

Mean change from baseline in mean of hemoglobin (Hb) values over a continuous 12-week interval from Week 13 to Week 24 in the absence of transfusions. Baseline was defined as the average of 2 or more Hb measurements at least 1 week apart within 4 weeks before Dose 1 Day 1.

Outcome measures

Outcome measures
Measure	Luspatercept n=96 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=47 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Mean Change From Baseline in Hemoglobin Values in the Absence of Transfusion (Week 13 to Week 24)	1.48 g/dL Standard Error 0.078	0.07 g/dL Standard Error 0.108

SECONDARY outcome

Timeframe: Assessed over a continuous 12 week period (from week 37 through week 48)

Erythroid Response is defined as an increase from baseline ≥1.0 g/dL in mean of hemoglobin values over a continuous 12-week interval from Weeks 37 to 48 of treatment in the absence of transfusions. Baseline hemoglobin (Hb) is the average of 2 or more Hb measurements at least 1 week apart within 4 weeks prior to Dose 1.

Outcome measures

Outcome measures
Measure	Luspatercept n=96 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=49 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Percentage of Participants Achieving Erythroid Response (Week 37 to Week 48)	70.8 Percentage of Participants Interval 60.7 to 79.7	2.0 Percentage of Participants Interval 0.1 to 10.9

SECONDARY outcome

Timeframe: Baseline and over a continuous 12 week period (from week 13 through week 24)

Population: All treated participants with available measurements at Baseline and at least one post-baseline FACIT-F questionnaire completed. Placebo participants are assessed up to crossing over to luspatercept. The luspatercept group does not include placebo participants who crossed over to luspatercept.

The FACIT-F is a multidimensional, self-report quality of life instrument which includes the Functional Assessment of Cancer Therapy - General (FACT-G) questionnaire (27 items over 4 different domains), and the Fatigue subscale (FS) component (13 items). FACIT-F version 4 has been used for this study. For the Fatigue subscale, each of the 13 items is scored from 0 ("not at all") to 4 ("very much"). The scores from individual items are summed to generated the final FS score, which ranges from 0 (best outcome) to 52 (worst outcome). The questionnaire is completed every other dose, and the mean of FS scores from Week 13 to Week 24 is compared to the FS score at baseline (last score available before start of study treatment). Baseline is defined as the last value taken on or before the first dose of study drug administered in Week 13.

Outcome measures

Outcome measures
Measure	Luspatercept n=90 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=43 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Mean Change From Baseline in Mean Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) Fatigue Subscale Score (Week 13 to Week 24)	1.64 Score on a scale Standard Error 0.774	0.26 Score on a scale Standard Error 1.066

SECONDARY outcome

Timeframe: Baseline and over a continuous 12 week period (from week 13 through week 24)

The NTDT-PRO V2.1 assess the severity of anemia-related symptoms associated with NTD β-thalassemia. It is a daily electronic diary with recall of symptoms during the past 24 hours, composed of 6 items: 1. Tiredness (lack of energy) when not doing physical activity 2. Tiredness (lack of energy) when doing physical activity 3. Weakness (lack of strength) when not doing physical activity 4. Weakness (lack of strength) when doing physical activity 5. Shortness of breath when not doing physical activity 6. Shortness of breath when doing physical activity. The Shortness of Breath (SoB) domain score represents the average score of items 5 and 6 above. SoB domain score ranges from 0 (best outcome, no shortness of breath) to 10 (worst outcome, extreme shortness of breath). Weekly SoB Scores represent the average of daily scores for that week. The mean of weekly scores over a continuous 12 week period (from Week 13 to Week 24) are compared to the SoB Domain Score at baseline.

Outcome measures

Outcome measures
Measure	Luspatercept n=94 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=48 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Mean Change From Baseline in Non-Transfusion Dependent β-thalassemia-Patient Reported Outcome (NTDT-PRO) Shortness of Breath (SoB) Domain Score (Week 13 to Week 24)	-0.46 Score on a scale Standard Error 0.168	0.02 Score on a scale Standard Error 0.228

SECONDARY outcome

Timeframe: Baseline and over a continuous 12 week period (from week 37 through week 48)

Population: All treated participants with available measurements at Baseline and From Week 37 to Week 48. Placebo participants are assessed up to crossing over to luspatercept. The luspatercept group does not include placebo participants who crossed over to luspatercept.

Mean change from baseline in mean of hemoglobin (Hb) values over a continuous 12-week interval from Week 37 to Week 48 in the absence of transfusions. Baseline was defined as the average of 2 or more Hb measurements at least 1 week apart within 4 weeks before Dose 1 Day 1.

Outcome measures

Outcome measures
Measure	Luspatercept n=91 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=34 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Mean Change From Baseline in Hemoglobin Values in the Absence of Transfusion (Week 37 to Week 48)	1.50 g/dL Standard Error 0.083	0.01 g/dL Standard Error 0.130

SECONDARY outcome

Timeframe: Baseline and over a continuous 12 week period (from week 37 through week 48)

The FACIT-F is a multidimensional, self-report quality of life instrument which includes the Functional Assessment of Cancer Therapy - General (FACT-G) questionnaire (27 items over 4 different domains), and the Fatigue subscale (FS) component (13 items). FACIT-F version 4 has been used for this study. For the Fatigue subscale, each of the 13 items is scored from 0 ("not at all") to 4 ("very much"). The scores from individual items are summed to generated the final FS score, which ranges from 0 (best outcome) to 52 (worst outcome). The questionnaire is completed every other dose, and the mean of FS scores from Week 37 to Week 48 is compared to the FS score at baseline (last score available before start of study treatment). Baseline is defined as the last value taken on or before the first dose of study drug administered in Week 37.

Outcome measures

Outcome measures
Measure	Luspatercept n=83 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=33 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Mean Change From Baseline in Mean Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) Fatigue Subscale Score (Week 37 to Week 48)	2.43 Score on a scale Standard Error 0.763	0.24 Score on a scale Standard Error 1.150

SECONDARY outcome

Timeframe: Baseline and over a continuous 12 week period (from week 37 through week 48)

Population: All treated participants with available measurements at Baseline and at Week 37 to Week 48. Placebo participants are assessed up to crossing over to luspatercept. The luspatercept group does not include placebo participants who crossed over to luspatercept.

NTDT-PRO V2.1 assess the severity of anemia-related symptoms. It's a daily recall of symptoms during the past 24 hours, composed of 6 items: 1. Tiredness (lack of energy) when not doing physical activity 2. Tiredness when doing physical activity 3. Weakness (lack of strength) when not doing physical activity 4. Weakness when doing physical activity 5. Shortness of breath when not doing physical activity 6. Shortness of breath when doing physical activity. The Tiredness/Weakness (T/W) domain score represents the average score of items 1 through 4 above. T/W domain score ranges from 0 (best outcome, no tiredness/weakness) to 10 (worst outcome, extreme tiredness/weakness). Weekly T/W Scores represent the average of daily scores for that week. The mean of weekly scores over a continuous 12-week period (from Week 37 to Week 48) are compared to the T/W Domain Score at baseline. Baseline is defined as the last value taken on or before the first dose of study drug administered in Week 37.

Outcome measures

Outcome measures
Measure	Luspatercept n=72 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=28 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Mean Change From Baseline in Non-Transfusion Dependent β-thalassemia-Patient Reported Outcome (NTDT-PRO) Tiredness and Weakness (T/W) Domain Score (Week 37 to Week 48)	-0.78 Score on a scale Standard Error 0.229	0.01 Score on a scale Standard Error 0.347

SECONDARY outcome

Timeframe: Baseline and over a continuous 12 week period (from week 37 through week 48)

NTDT-PRO V2.1 assess the severity of anemia-related symptoms. It is a daily recall of symptoms during the past 24 hours, composed of 6 items: 1. Tiredness (lack of energy) when not doing physical activity 2. Tiredness when doing physical activity 3. Weakness (lack of strength) when not doing physical activity 4. Weakness when doing physical activity 5. Shortness of breath when not doing physical activity 6. Shortness of breath when doing physical activity. The Shortness of Breath (SoB) domain score represents the average score of items 5 and 6 above. SoB domain score ranges from 0 (best outcome, no shortness of breath) to 10 (worst outcome, extreme shortness of breath). Weekly SoB Scores represent the average of daily scores for that week. The mean of weekly scores over a continuous 12-week period (from Week 37 to Week 48) are compared to the SoB Domain Score at baseline. Baseline is defined as the last value taken on or before the first dose of study drug administered in Week 37.

Outcome measures

Outcome measures
Measure	Luspatercept n=72 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=28 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Mean Change From Baseline in Non-Transfusion Dependent β-thalassemia-Patient Reported Outcome (NTDT-PRO) Shortness of Breath (SoB) Domain Score (Week 37 to Week 48)	-0.59 Score on a scale Standard Error 0.212	0.47 Score on a scale Standard Error 0.320

SECONDARY outcome

Timeframe: Baseline and over a continuous 12 week period (from week 13 through week 24)

The FACIT-Fatigue, is a multidimensional, self-report quality of life instrument. It consists of 27 core items, the Functional Assessment of Cancer Therapy - General (FACT-G) questionnaire, which assesses patient function in 4 domains: Physical, Social/Family, Emotional, and Functional well-being, which is further supplemented by a 13-item measure designed to capture cancer-related fatigue, the Fatigue subscale (FS). The items are measured on a response scale with five options (0 = not at all to 4 = very much). Participants completed the questionnaire at screening and every other dose. Baseline is defined as the last value taken on or before the first dose of study drug administered in Week 13. Score is calculated by multiplying the sum of item scores by the n of items in the scale, then divided by n of items answered.

Outcome measures

Outcome measures
Measure	Luspatercept n=94 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=47 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Percentage of Participants With an Increase From Baseline ≥ 3 in Mean Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) Fatigue Subscale Score (Week 13 to Week 24)	40.4 Percent of Participants Interval 30.4 to 51.0	27.7 Percent of Participants Interval 15.6 to 42.6

SECONDARY outcome

Timeframe: Baseline and over a continuous 12 week period (from week 37 through week 48)

The FACIT-Fatigue, is a multidimensional, self-report quality of life instrument. It consists of 27 core items, the Functional Assessment of Cancer Therapy - General (FACT-G) questionnaire, which assesses patient function in 4 domains: Physical, Social/Family, Emotional, and Functional well-being, which is further supplemented by a 13-item measure designed to capture cancer-related fatigue, the Fatigue subscale (FS). The items are measured on a response scale with five options (0 = not at all to 4 = very much). Participants completed the questionnaire at screening and every other dose. Baseline is defined as the last value taken on or before the first dose of study drug administered in Week 37. Score is calculated by multiplying the sum of item scores by the n of items in the scale, then divided by n of items answered.

Outcome measures

Outcome measures
Measure	Luspatercept n=94 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=47 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Percentage of Participants With an Increase From Baseline ≥ 3 in Mean Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) Fatigue Subscale Score (Week 37 to Week 48)	36.2 Percent of Participants Interval 26.5 to 46.7	21.3 Percent of Participants Interval 10.7 to 35.7

SECONDARY outcome

Timeframe: From baseline to Week 24 and from baseline to Week 48 of study treatment

Population: All treated participants with available measurements at Baseline, at Week 24 and at Week 48. Placebo participants are assessed up to crossing over to luspatercept. The luspatercept group does not include placebo participants who crossed over to luspatercept.

The SF-36v2 is a 36-item generic PRO questionnaire used to assess patient-reported outcomes. The SF-36 yields scores for 8 domains of health: Physical Functioning (PF), Role-Physical (RP), Bodily Pain (BP), General Health (GH), Vitality (VT), Social Functioning (SF), Role Emotional (RE), and Mental Health (MH) as well as physical component summary (PCS) and mental component summary (MCS) scores. Scores from each of the 8 domains of health are first normalized based on US general population means, then aggregated and transformed so that the scores from each of the 8 domains of health will contribute differently to the determination of PCS and MCS summary scores. PCS and MCS scores range from 0 to 100, with higher scores indicating a better quality of life. Baseline is defined as the last value taken on or before the first dose of study drug administered.

Outcome measures

Outcome measures
Measure	Luspatercept n=76 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=37 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Mean Change From Baseline in the Physical Component Summary (PCS) and Mental Component Summary (MCS) Scores of the Medical Outcomes Study 36-Item Short Form (SF-36) Physical Component Summary (PCS) up to Week 24	1.00 Score on a scale Standard Error 0.499	-0.38 Score on a scale Standard Error 0.684
Mean Change From Baseline in the Physical Component Summary (PCS) and Mental Component Summary (MCS) Scores of the Medical Outcomes Study 36-Item Short Form (SF-36) Physical Component Summary (PCS) up to Week 48	1.23 Score on a scale Standard Error 0.571	-0.52 Score on a scale Standard Error 0.822
Mean Change From Baseline in the Physical Component Summary (PCS) and Mental Component Summary (MCS) Scores of the Medical Outcomes Study 36-Item Short Form (SF-36) Mental Component Summary (MCS) up to Week 24	0.83 Score on a scale Standard Error 0.674	-0.71 Score on a scale Standard Error 0.947
Mean Change From Baseline in the Physical Component Summary (PCS) and Mental Component Summary (MCS) Scores of the Medical Outcomes Study 36-Item Short Form (SF-36) Mental Component Summary (MCS) up to Week 48	0.81 Score on a scale Standard Error 0.784	-1.89 Score on a scale Standard Error 1.152

SECONDARY outcome

Timeframe: Week 24 and Week 48 of study treatment

Iron overload was measured by Liver Iron Concentration (LIC) and Iron Chelation Therapy (ICT) daily dose. Improvement is defined as: - For participants with baseline LIC ≥3 mg/g: ≥20% reduction in LIC or ≥ 33% decrease in ICT daily dose - For participants with baseline LIC \<3 mg/g: no increase in LIC \>1 mg/g and not starting treatment with ICT, or no increase in ICT daily dose ≥ 33% (if on ICT at baseline)

Outcome measures

Outcome measures
Measure	Luspatercept n=96 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=49 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Percentage of Participants With Improvement of Iron Overload Week 24	44.8 Percent of participants	49.0 Percent of participants
Percentage of Participants With Improvement of Iron Overload Week 48	34.4 Percent of participants	49.0 Percent of participants

SECONDARY outcome

Timeframe: Week 24 and Week 48 of study treatment

Population: All treated participants with available measurements at Baseline and at week 24 or week 48. Placebo participants are assessed up to crossing over to luspatercept. The luspatercept group does not include placebo participants who crossed over to luspatercept.

Baseline mean serum ferritin is calculated during the 24 weeks on or prior to dose 1 day 1. Post-baseline mean serum ferritin is calculated as mean of ferritin values during the last 24 weeks on or prior to the end date of the first 24 week or 48 week treatment

Outcome measures

Outcome measures
Measure	Luspatercept n=92 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=44 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Mean Change From Baseline in Serum Ferritin Week 24	29.32 ug/L Standard Error 22.949	2.18 ug/L Standard Error 32.217
Mean Change From Baseline in Serum Ferritin Week 48	84.94 ug/L Standard Error 23.120	71.48 ug/L Standard Error 32.457

SECONDARY outcome

Timeframe: Week 24 and Week 48 of study treatment

LIC was measured by Magnetic Resonance Imaging (MRI). Baseline is defined as the last value on or before the first dose of study drug is administered; Postbaseline is defined as the closest visit at Week 24 or Week 48. Participants with LIC value \>43 are not included in the analysis.

Outcome measures

Outcome measures
Measure	Luspatercept n=87 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=45 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Mean Change From Baseline in Liver Iron Concentration (LIC) Week 24	-0.30 mg/g dry weight Standard Error 0.125	-0.21 mg/g dry weight Standard Error 0.169
Mean Change From Baseline in Liver Iron Concentration (LIC) Week 48	-0.34 mg/g dry weight Standard Error 0.233	-1.00 mg/g dry weight Standard Error 0.329

SECONDARY outcome

Timeframe: From first dose to Week 24

Transfusion free is defined as the absence of any transfusion during Week 1-24 of study treatment. Participants who discontinued treatment prior to Week 24 were not considered as transfusion free during Week 1-24.

Outcome measures

Outcome measures
Measure	Luspatercept n=96 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=49 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Percentage of Participants Who Are Transfusion-Free Over 24 Weeks	89.6 Percent of Participants	67.3 Percent of Participants

SECONDARY outcome

Timeframe: From first dose to Week 48

Transfusion free is defined as the absence of any transfusion during Week 1-48 of study treatment. Participants who discontinued treatment prior to Week 48 were not considered as transfusion free during Week 1-48.

Outcome measures

Outcome measures
Measure	Luspatercept n=96 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=49 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Percentage of Participants Who Are Transfusion-Free Over 48 Weeks	82.3 Percent of Participants	44.9 Percent of Participants

SECONDARY outcome

Timeframe: From baseline up to approximately 56 months

Population: All participants with a mean hemoglobin increase ≥1.0 g/dL. Placebo participants are assessed up to crossing over to luspatercept. The luspatercept group does not include placebo participants who crossed over to luspatercept.

This outcome measure is the cumulative mean of the duration of hemoglobin response for the ≥ 1.0 g/dL during any 12-week rolling period. Any hemoglobin values within 21 days after a transfusion were excluded from the analysis.

Outcome measures

Outcome measures
Measure	Luspatercept n=91 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=11 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Duration of the Mean Hemoglobin Increase From Baseline ≥1.0 g/dL	1136.0 Days Standard Deviation 491.86	203.3 Days Standard Deviation 170.82

SECONDARY outcome

Timeframe: From baseline to Week 24 and from baseline to Week 48 of study treatment

Population: All treated participants with available measurements at Baseline and at Week 24 or Week 48. Placebo participants are assessed up to crossing over to luspatercept. The luspatercept group does not include placebo participants who crossed over to luspatercept.

The 6MWT is typically used to objectively assess functional exercise capacity and response to medical interventions in patients with various moderate to severe diseases. Particiapnts are asked to walk as quickly as possible without running along a 30-meter corridor for six minutes, and the total distance covered during that time is measured. Baseline is defined as the last value on or before the first dose of study drug is administered. Postbaseline is defined as the closest visit at Week 24 or Week 48.

Outcome measures

Outcome measures
Measure	Luspatercept n=87 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=47 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Mean Change From Baseline in the 6-Minute Walk Test (6MWT) Distance 24 Weeks	7.20 Meters Standard Error 7.017	-8.96 Meters Standard Error 9.297
Mean Change From Baseline in the 6-Minute Walk Test (6MWT) Distance 48 Weeks	8.82 Meters Standard Error 5.907	-3.62 Meters Standard Error 8.141

SECONDARY outcome

Timeframe: From Week 13 to Week 24 of study treatment

Percentage of participants who have an increase from baseline ≥1.5 g/dL in mean of hemoglobin (Hb) values over a continuous 12-week interval from Week 13 to Week 24 in the absence of transfusions. Baseline was defined as the average of 2 or more Hb measurements at least 1 week apart within 4 weeks before Dose 1 Day 1.

Outcome measures

Outcome measures
Measure	Luspatercept n=96 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=49 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Percentage of Participants With an Increase From Baseline ≥1.5 g/dL in Mean Hemoglobin Values in the Absence of Transfusion	52.1 Percentage of Participants Interval 41.6 to 62.4	0.0 Percentage of Participants Interval 0.0 to 7.3

SECONDARY outcome

Timeframe: From Week 13 to Week 24 and from Week 37 to Week 48 of study treatment

Population: All treated participants with available measurements at Baseline and at the indicated 12-week periods. Placebo participants are assessed up to crossing over to luspatercept. The luspatercept group does not include placebo participants who crossed over to luspatercept.

The responder definition (RD) threshold is the individual participant score change over a predetermined time period that will be interpreted as a treatment benefit. The RD for the NTDT-PRO T/W domain score was defined as ≥ 1-point decrease (ie, RD = -1) from baseline over the time from Week 13 to Week 24 or from Week 37 to Week 48. Participants with missing NTDT-PRO T/W scores at the indicated 12-week period are classified as non-responders in the analysis.

Outcome measures

Outcome measures
Measure	Luspatercept n=96 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=49 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Percentage of Participants With a Decrease From Baseline ≥ RD (= 1) in the Non-Transfusion Dependent β-thalassemia-Patient Reported Outcome (NTDT-PRO) Tiredness and Weakness (T/W) Domain Score Week 13 to week 24	37.5 Percent of participants Interval 27.8 to 48.0	28.6 Percent of participants Interval 16.6 to 43.3
Percentage of Participants With a Decrease From Baseline ≥ RD (= 1) in the Non-Transfusion Dependent β-thalassemia-Patient Reported Outcome (NTDT-PRO) Tiredness and Weakness (T/W) Domain Score Week 37 to week 48	31.3 Percent of participants Interval 22.2 to 41.5	18.4 Percent of participants Interval 8.8 to 32.0

SECONDARY outcome

Timeframe: From first dose to 63 days after last dose (up to approximately 56 months)

An Adverse Event (AE) is defined as any new untoward medical occurrence or worsening of a pre-existing medical condition in a clinical investigation participant administered study treatment and that does not necessarily have a causal relationship with this treatment. Adverse events are graded on a scale from 1 to 5, with Grade 1 being mild and asymptomatic; Grade 2 is moderate requiring minimal, local or noninvasive intervention; Grade 3 is severe or medically significant but not immediately life-threatening; Grade 4 events are usually severe enough to require hospitalization; Grade 5 events are fatal.

Outcome measures

Outcome measures
Measure	Luspatercept n=96 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=49 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Number of Participants Experiencing Adverse Events Treatment-emergent adverse-event (TEAE)	96 Participants	48 Participants
Number of Participants Experiencing Adverse Events Serious TEAE	23 Participants	13 Participants
Number of Participants Experiencing Adverse Events Treatment-related TEAE	79 Participants	18 Participants
Number of Participants Experiencing Adverse Events Treatment-related Serious TEAE	4 Participants	0 Participants
Number of Participants Experiencing Adverse Events TEAE Leading to Death	1 Participants	0 Participants
Number of Participants Experiencing Adverse Events TEAE Leading to Dose Reduction	11 Participants	0 Participants
Number of Participants Experiencing Adverse Events TEAE Leading to Dose Delay	47 Participants	11 Participants
Number of Participants Experiencing Adverse Events TEAE Leading to Study Drug Discontinuation	5 Participants	4 Participants
Number of Participants Experiencing Adverse Events Treatment-related TEAE Leading to Death	0 Participants	0 Participants
Number of Participants Experiencing Adverse Events Treatment-related TEAE Leading to Dose Reduction	11 Participants	0 Participants
Number of Participants Experiencing Adverse Events Treatment-related TEAE Leading to Dose Delay	10 Participants	0 Participants
Number of Participants Experiencing Adverse Events Treatment-related TEAE Leading to Study Drug Discontinuation	4 Participants	0 Participants

SECONDARY outcome

Timeframe: From first dose and up to 2 years following last dose, up to approximately 56 months

Population: All treated participants. Placebo participants are assessed up to crossing over to luspatercept. The luspatercept group does not include placebo who crossed over to luspatercept.

Presence of anti-drug (ACE-536/Luspatercept) antibodies was assessed every 24 weeks from serum samples. A participant is counted as 'positive' if there is any positive result captured during the study.

Outcome measures

Outcome measures
Measure	Luspatercept n=96 Participants Luspatercept was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle). The starting dose level was 1.00 mg/kg and could be escalated to 1.25 mg/kg and/or reduced to 0.80, 0.60, and 0.45 mg/kg. Participants were treated for a minimum of 48 weeks.	Placebo n=49 Participants Placebo (0.9% sodium chloride for injection) was administered as subcutaneous injection once every 3 weeks (administered on Study Day 1 of each 21-day treatment cycle) for a minimum of 48 weeks. Eligible participants entered an open-label phase and started Luspatercept treatment for up to approximately 24 months.
Number of Participants With Anti-drug Antibody (ADA) Positive Test for Luspatercept	5 Participants	3 Participants

SECONDARY outcome

Timeframe: Doses 1 to 16: at predose (must be collected before first dose), Dose 2 Day 1, Dose 4 Day 1, Dose 6 Day 1, Dose 8 Day 1, Dose 12 Day 1, Dose 16 Day 1, Dose 6 Day 8, Dose 6 Day 15, and every 6 doses (at Dose 22, 28, etc.), up to approx. 48 months