What are the indications, recommended dosing, monitoring parameters, and treatment criteria for luspatercept in adult patients with transfusion‑dependent anemia due to myelodysplastic syndromes with ring sideroblasts or β‑thalassemia?

Luspatercept for Transfusion-Dependent Anemia in MDS and β-Thalassemia

Luspatercept is indicated for adults with transfusion-dependent anemia due to lower-risk MDS with ring sideroblasts (RS ≥15% or RS ≥5% with SF3B1 mutation) and β-thalassemia, administered subcutaneously at 1.0 mg/kg every 3 weeks with dose escalation up to 1.75 mg/kg based on response. 1

Indications

Myelodysplastic Syndromes

For MDS-RS patients, luspatercept is now a Category 1 preferred first-line option alongside imetelstat (if serum EPO >500 mU/mL), representing a paradigm shift from the previous ESA-first approach. 2 The 2025 NCCN guidelines position luspatercept as preferred therapy for:

• Lower-risk MDS (very low, low, or intermediate risk by IPSS-R)
• Ring sideroblasts ≥15% OR RS ≥5% with SF3B1 mutation
• Transfusion-dependent anemia
• Can be used as first-line therapy (ESA-naïve) or after ESA failure 2

The ESMO guidelines (2021) recommend luspatercept specifically after ESA failure in RBC transfusion-dependent MDS-RS patients [Level I, A evidence]. 3

β-Thalassemia

Approved for adults with transfusion-dependent β-thalassemia requiring regular RBC transfusions (≥4 units per 8 weeks). 1, 4

Dosing Recommendations

Starting Dose

• 1.0 mg/kg subcutaneously every 3 weeks 1

Dose Modifications

• Escalate by 0.25 mg/kg increments if inadequate response after 2 consecutive doses (minimum 3 weeks between escalations)
• Maximum dose: 1.75 mg/kg 1
• Dose reduction: Decrease by 0.25 mg/kg if hemoglobin increases >2 g/dL within 3 weeks or reaches ≥11.5 g/dL
• Hold dose if hemoglobin ≥11.5 g/dL; resume at reduced dose when hemoglobin <11 g/dL

Treatment Duration

Continue until disease progression or unacceptable toxicity. Responses typically occur within 8 months of initiation, with many being long-lasting. 5 Assess response at 3-6 months per NCCN guidelines. 2

Treatment Selection Algorithm

First-Line Therapy (MDS-RS)

Check serum EPO level first:

• Serum EPO ≤500 mU/mL: Luspatercept (Category 1, preferred) OR ESAs (epoetin alfa/darbepoetin) 2
• Serum EPO >500 mU/mL: Imetelstat preferred; luspatercept is alternative 2

The 2025 NCCN update represents a major shift—luspatercept is now preferred first-line regardless of ESA exposure, based on MEDALIST trial data showing 38% achieved ≥8 weeks transfusion independence. 2, 6

After ESA Failure

Luspatercept is Category 1 preferred option regardless of serum EPO level 2, 3

Patient Selection Factors Predicting Better Response

• Lower transfusion burden (<4 units/8 weeks): 72.9% achieve 8-week TI 7
• RS-positive disease: 57.8% achieve 8-week TI 7
• Serum EPO <100 mU/mL: Associated with higher response rates 8
• Fewer baseline mutations: Better overall survival in responders 5

Monitoring Parameters

Baseline Assessment

• Complete blood count with differential and reticulocyte count
• Serum EPO level
• Bone marrow with iron stain, cytogenetics, and molecular testing (SF3B1 mutation status)
• Blood pressure
• Pregnancy test (females of reproductive potential)

During Treatment

• CBC weekly until stable hemoglobin achieved, then before each dose
• Blood pressure before each dose (hypertension is common adverse event)
• Transfusion requirements tracked continuously
• Response assessment at 16-24 weeks minimum 5

Response Criteria (IWG 2018)

• Transfusion independence (TI): No transfusions for ≥8 consecutive weeks
• Hematologic improvement-erythroid (HI-E): Hemoglobin increase ≥1.5 g/dL OR reduction in transfusion burden ≥4 units over 8 weeks

Efficacy Data

MDS-RS Population

• 8-week TI: 51.2% overall; 57.8% in RS+ patients 7
• 12-week TI: 57.0% 7
• 24-week TI: 35.8% 7
• Real-world data: 44.3% achieved >8 weeks TI, with median response duration 58.3 weeks 5

β-Thalassemia

• ≥33% transfusion burden reduction: 21.4% vs 4.5% placebo (BELIEVE trial) 4
• Transfusion independence: Achieved in 11% of patients 4

Safety Profile and Management

Most Common Adverse Events (Any Grade)

• Fatigue (most common)
• Diarrhea
• Peripheral edema (17.8%) 7
• Asthenia
• Nausea
• Dizziness
• Bone pain
• Headache
• Myalgia 6, 9

Important: Adverse event incidence decreases over time with continued therapy. 6

Serious Adverse Events

Occur in 28% of patients but are generally manageable 7

Critical Warnings

Thrombosis/Thromboembolism: Monitor for signs/symptoms; use caution in patients with history of thrombotic events 1

Hypertension: Common—monitor blood pressure before each dose and manage appropriately 1, 8

Extramedullary Hematopoietic Masses: May occur in β-thalassemia patients; monitor clinically 1

Embryo-Fetal Toxicity: Contraindicated in pregnancy; verify negative pregnancy test before initiation and use effective contraception 1

Discontinuation

• 8% discontinue due to adverse events (shortness of breath, falls, fatigue, hypertension) 8
• 11% progress to higher-risk MDS or AML during treatment 8

Common Pitfalls and Caveats

1. Don't wait for ESA failure: The 2025 NCCN guidelines now support luspatercept as first-line therapy in appropriate MDS-RS patients 2

2. Verify iron stores: Ensure adequate iron repletion before starting any erythroid therapy 2

3. Response timing: All responses occur within 8 months; if no response by 6 months, consider alternative therapy 5

4. Transfusion burden matters: Patients with lower baseline transfusion requirements respond better (72.9% TI rate in low transfusion burden) 7

5. Don't use in del(5q) without RS: Lenalidomide remains preferred for del(5q) MDS without ring sideroblasts 2, 3

6. Monitor for progression: 11% progress to higher-risk disease; maintain surveillance 8

7. Blood pressure monitoring is mandatory: Hypertension is a common, manageable adverse event requiring proactive management 1, 8

Treatment Sequencing After Luspatercept Failure

If no response after 3-6 months or relapse occurs:

• Serum EPO ≤500 mU/mL: Imetelstat (Category 1, preferred) or ESAs ± G-CSF 2
• Serum EPO >500 mU/mL: Imetelstat (if not previously used) or consider lenalidomide 2
• Clinical trial enrollment or hypomethylating agents (azacitidine) for progression 2