Introduction

Most patients with myelofibrosis (MF) will develop anemia, contributing to poor quality of life and reduced survival. In the phase 2 ACE-536-MF-001 study (NCT03194542), luspatercept, a first-in-class erythroid maturation agent, was shown to increase hemoglobin levels and red blood cell transfusion (RBCT) independence, and reduce transfusion burden in patients with MF (Gerds AR, et al. Blood Advances 2024). Luspatercept is currently included in the NCCN Clinical Practice Guidelines in Oncology for Myeloproliferative Neoplasms as a category 2A recommended treatment for the management of MF-associated anemia. However, real-world (RW) evidence regarding the effect of luspatercept on transfusion burden in patients with MF-associated anemia requiring RBCTs is limited.

Guidelines referenced with permission from the NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines®) for Myeloproliferative Neoplasms v.2.2025. © National Comprehensive Cancer Network, Inc. 2025. All rights reserved. Accessed July 18, 2025. To view the most recent and complete version of the guideline, go online to NCCN.org. NCCN makes no warranties of any kind whatsoever regarding their content, use or application and disclaims any responsibility for their application or use in any way.Aim

To describe baseline characteristics, treatment patterns, and outcomes of patients with MF-related anemia requiring RBCT who were treated with luspatercept in the RW setting.Methods

This non-interventional cohort study utilized the Optum Clinformatics® Data Mart Database to identify adult patients (≥ 18 years) in the US, with MF diagnosis on or after Jan 1, 2010, and anemia diagnosis within 3 months prior to or any time after MF diagnosis. Patients were included if they initiated 1 or more luspatercept treatments (index date) after Jan 1, 2020, and received at least 1 RBCT (RBCT event defined as ~ 2 transfusion units) within 12 weeks prior to the index date. Continuous medical and pharmacy enrollment was required for ≥ 6 months before and after the index date. Key outcomes included the proportion of patients who were RBCT-free over any consecutive 12-week or 16-week period (RBC-TI 12, RBC-TI 16) starting between index date and week 24, duration of RBC-TI response, and RBCT reduction.Results

At the end of data availability (Dec 31, 2024), 99 patients who received luspatercept were identified, of whom 19 also received overlapping JAKi treatment. The median (range) age was 77 years (55–87), 54.6% were male, and 41.4% had primary MF. The majority (74.7%) of patients were White, 14.1% were Black, 3.0% were Asian, and 8.1% were classified as other races. The median (IQR) time between MF diagnosis and index date was 1.2 years (0.4–3.7) and median (IQR) follow-up time post-index was 12.3 months (6.7–20.7). Thirty-one (31.3%) patients were treated with JAKi at any time post-MF diagnosis and 54 (54.6%) patients were deceased by the end of data availability. Median (IQR) number of RBCT events was 3 (2–5) and 77 (77.8%) patients were considered transfusion dependent (TD: ≥ 2 RBCT events) at baseline.

The median time to treatment discontinuation per Kaplan–Meier estimate was 33.6 weeks (95% CI 25.1–51.7). The probability of remaining on treatment was 55.7% at 6 months and 35.8% at 12 months.

The proportion of patients who achieved RBC-TI 12 and RBC-TI 16 after luspatercept initiation was 38.4% (n = 38) and 33.3% (n = 33). The median (95% CI) duration of both RBC-TI 12 and RBC-TI 16 was 37.4 weeks (30.4–NR). Sixty-six (66.7%) patients achieved ≥ 50% RBCT reduction by 24 weeks.Conclusions

In this RW study, MF patients who required RBCT treated with luspatercept showed clinically meaningful benefits: nearly 40% achieved 12-week RBC-TI and two-thirds experienced ≥ 50% RBCT reduction within 24 weeks of luspatercept initiation. The findings of this RW study generally corroborate and supplement previous clinical trial results, indicating that luspatercept can be effective in increasing RBC-TI and reducing transfusion burden in this population.

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2025
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