Luspatercept side effects: what 2,455 FDA adverse event reports show

Luspatercept · Reblozyl · 34 reaction terms · 962 drug–reaction co-reports · data 2026-09-14

Drug class

Erythroid Maturation Agent

FDA label (Established Pharmacologic Class)

Brand names

Reblozyl

openFDA label

Who reports

2,455 reports · 62% serious · 393 with death outcome · 43% female

openFDA FAERS counts, all years, deduplication not applied

Used for

REBLOZYL is an erythroid maturation agent indicated for the treatment of: • Anemia in adult patients with beta thalassemia who require regular red blood cell (RBC) transfusions ( 1.1 ). • Anemia without previous erythropoiesis stimulating agent use (ESA-naïve) in adult patients with very low- to intermediate-risk myelodysplastic syndromes (MDS) who may require regular red blood cell (RBC) transfusions ( 1.2 ).

FDA label, Indications and Usage

What it is

Luspatercept-aamt is an erythroid maturation agent. Luspatercept-aamt is a receptor fusion protein consisting of a modified extracellular domain of the human activin receptor type IIB linked to a human IgG1 Fc domain with a calculated molecular mass of approximately 76 kD.

FDA label, Description section

Boxed warning

None in the current label

How to read this page. FAERS is a spontaneous-reporting system: counts are not incidence rates and a signal is not proof of causation. Each reaction below is run through an automated screen — is the term in the FDA label (known), in the indications (the disease being treated), an administrative/coding term, or none of these (unlabeled)? That screen is mechanical text matching, not a causality assessment. The 30 hand-written Bradford Hill assessments are on the causality assessment page. Not medical advice.

Causality screen of the 19 strongest signals

Labeled adverse reaction 1Labeled (related wording) 1Likely indication confounding 1Reporting / coding artifact 5Lab value / disease marker 5Outcome field, not a reaction 1Not in label — unassessed 5

What the badges mean

Labeled adverse reaction The exact term appears in the label's warnings or adverse-reactions sections: a known, expected effect. The FAERS signal confirms the label rather than discovering anything.
Labeled (related wording) The label describes this effect under different wording (e.g. 'neutropenia' for 'neutrophil count decreased'). Treated as known.
Likely indication confounding The term appears in the label's indications: reports probably describe the disease being treated (or its progression), not a drug effect. Classic confounding by indication.
Reporting / coding artifact An administrative, monitoring or exposure term (product issue, off-label use, 'test normal', overdose...). Not a biological reaction; a high PRR here reflects how reports are coded.
Lab value / disease marker A laboratory result, investigation or disease-activity marker (antibody positive, CRP abnormal, swollen joint count) not described in the label. These usually mirror the monitored disease or testing protocol rather than a drug effect; not screened further.
Outcome field, not a reaction Death is a report outcome, not a reaction term. It is dominated by the underlying illness; see the seriousness profile and the boxed warning instead.
Not in label — unassessed Not found in the label text, not an artifact pattern. This is a genuine candidate for a formal causality assessment (Bradford Hill / WHO-UMC); it has NOT had one here.

Strongest disproportionality signals

Flagged terms (PRR ≥ 2, χ² ≥ 4, n ≥ 10), ranked by PRR; infinite PRRs (no comparator reports) excluded. The EBGM column is a second, shrinkage-based estimate (MGPS) with its 5th percentile EB05 and the BCPNN IC025; a pair flagged by PRR alone is marked PRR-only and should be read as fragile. The strata column recomputes the PRR on serious reports only and flags pairs whose reports are unusually skewed by sex or come mostly from consumers rather than clinicians. 15 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.

Show: hide coding/lab/outcome terms hide indication terms unlabeled only hide PRR-only

Reaction	Reports	PRR 95% CI · ROR · χ²/p	EBGM EB05 · IC025	Label screen	Serious-only & strata	Trial cross-check
Myelodysplastic syndrome	68	40.2 31.8–50.8ROR 41.3 · χ² 2,548 / p <1e-300	39.6 EB05 32.3 · IC025 +4.6 3/3 methods agree	Likely indication confounding term in indications; also in warnings	serious PRR 37.1	no trial data cached
Product preparation error	37	15.2 11.1–21.0ROR 15.4 · χ² 477 / p 4e-106	15.0 EB05 11.2 · IC025 +3.1 3/3 methods agree	Reporting / coding artifact	serious n=1 · 92% clinician	no trial data cached
Full blood count decreased	36	15.2 11.0–21.1ROR 15.4 · χ² 464 / p 4e-103	15.0 EB05 11.1 · IC025 +3.1 3/3 methods agree	Lab value / disease marker	serious PRR 18.2	no trial data cached
Haemoglobin decreased	142	11.8 10.0–13.8ROR 12.4 · χ² 1,392 / p <1e-300	11.7 EB05 10.1 · IC025 +3.2 3/3 methods agree	Labeled (related wording) related wording	serious PRR 9.4	no trial data cached
Acute myeloid leukaemia	21	11.5 7.5–17.6ROR 11.6 · χ² 191 / p 1e-43	10.6 EB05 6.9 · IC025 +2.5 3/3 methods agree	Not in label — unassessed	serious PRR 10.8 · 90% clinician	no trial data cached
Platelet count increased	15	9.8 5.9–16.2ROR 9.8 · χ² 110 / p 6e-26	8.4 EB05 5.1 · IC025 +2.1 3/3 methods agree	Lab value / disease marker	serious PRR 6.4	no trial data cached
Product storage error	84	8.3 6.7–10.2ROR 8.5 · χ² 531 / p 8e-118	8.0 EB05 6.6 · IC025 +2.6 3/3 methods agree	Reporting / coding artifact	95% clinician	no trial data cached
Hepatic cytolysis	11	7.7 4.2–13.8ROR 7.7 · χ² 57 / p 2e-14	6.1 EB05 3.6 · IC025 +1.5 3/3 methods agree	Not in label — unassessed	serious PRR 7.2	no trial data cached
Fracture	16	7.2 4.4–11.7ROR 7.2 · χ² 79 / p 3e-19	6.1 EB05 3.9 · IC025 +1.8 3/3 methods agree	Not in label — unassessed	serious PRR 7.4	no trial data cached
Therapy non-responder	37	7.1 5.1–9.7ROR 7.2 · χ² 187 / p 7e-43	6.6 EB05 5.0 · IC025 +2.2 3/3 methods agree	Reporting / coding artifact	serious PRR 5.8	no trial data cached
Bone pain	45	6.5 4.9–8.7ROR 6.6 · χ² 206 / p 5e-47	6.2 EB05 4.8 · IC025 +2.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 4.3	no trial data cached
Blood pressure systolic increased	12	5.2 3.0–9.2ROR 5.2 · χ² 37 / p 7e-10	4.4 EB05 2.7 · IC025 +1.2 3/3 methods agree	Lab value / disease marker	serious PRR 4.0	no trial data cached
Blood bilirubin increased	16	5.0 3.1–8.2ROR 5.1 · χ² 48 / p 2e-12	4.4 EB05 2.9 · IC025 +1.3 3/3 methods agree	Lab value / disease marker	serious PRR 3.4	no trial data cached
Laboratory test abnormal	17	4.9 3.1–7.9ROR 4.9 · χ² 49 / p 1e-12	4.4 EB05 2.9 · IC025 +1.3 3/3 methods agree	Reporting / coding artifact	serious PRR 2.6	no trial data cached
White blood cell count increased	22	4.9 3.2–7.4ROR 4.9 · χ² 64 / p 7e-16	4.4 EB05 3.1 · IC025 +1.4 3/3 methods agree	Lab value / disease marker	serious PRR 4.0	no trial data cached
Prescribed overdose	10	4.4 2.4–8.2ROR 4.4 · χ² 23 / p 8e-7	3.7 EB05 2.2 · IC025 +0.8 3/3 methods agree	Not in label — unassessed	serious PRR 7.0	no trial data cached
Adverse event	43	4.0 3.0–5.3ROR 4.0 · χ² 93 / p 3e-22	3.8 EB05 3.0 · IC025 +1.4 3/3 methods agree	Reporting / coding artifact	serious PRR 1.9	no trial data cached
Jaundice (yellowing of skin/eyes)	10	3.2 1.7–5.9ROR 3.2 · χ² 13 / p 2e-4	2.8 EB05 1.7 · IC025 +0.4	Not in label — unassessed	serious PRR 3.1	no trial data cached
Death	233	2.3 2.0–2.6ROR 2.4 · χ² 178 / p 8e-41	2.3 EB05 2.1 · IC025 +1.0 3/3 methods agree	Outcome field, not a reaction	serious PRR 2.1	no trial data cached

Trial evidence (ClinicalTrials.gov)

Trial cross-check not yet run for this drug (ClinicalTrials.gov pull covers the 800 most-reported drugs first).

Most frequently reported reactions

By raw co-report count, regardless of disproportionality. Common terms here are often the illness itself or generic outcomes.

Reaction	Reports	PRR 95% CI · ROR · χ²/p	EBGM EB05 · IC025	Label screen	Serious-only & strata	Trial cross-check
Death	233	2.3 2.0–2.6ROR 2.4 · χ² 178 / p 8e-41	2.3 EB05 2.1 · IC025 +1.0 3/3 methods agree	Outcome field, not a reaction	serious PRR 2.1	no trial data cached
Haemoglobin decreased	142	11.8 10.0–13.8ROR 12.4 · χ² 1,392 / p <1e-300	11.7 EB05 10.1 · IC025 +3.2 3/3 methods agree	Labeled (related wording) related wording	serious PRR 9.4	no trial data cached
Product storage error	84	8.3 6.7–10.2ROR 8.5 · χ² 531 / p 8e-118	8.0 EB05 6.6 · IC025 +2.6 3/3 methods agree	Reporting / coding artifact	95% clinician	no trial data cached
Myelodysplastic syndrome	68	40.2 31.8–50.8ROR 41.3 · χ² 2,548 / p <1e-300	39.6 EB05 32.3 · IC025 +4.6 3/3 methods agree	Likely indication confounding term in indications; also in warnings	serious PRR 37.1	no trial data cached
Bone pain	45	6.5 4.9–8.7ROR 6.6 · χ² 206 / p 5e-47	6.2 EB05 4.8 · IC025 +2.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 4.3	no trial data cached
Adverse event	43	4.0 3.0–5.3ROR 4.0 · χ² 93 / p 3e-22	3.8 EB05 3.0 · IC025 +1.4 3/3 methods agree	Reporting / coding artifact	serious PRR 1.9	no trial data cached
Therapy non-responder	37	7.1 5.1–9.7ROR 7.2 · χ² 187 / p 7e-43	6.6 EB05 5.0 · IC025 +2.2 3/3 methods agree	Reporting / coding artifact	serious PRR 5.8	no trial data cached
Product preparation error	37	15.2 11.1–21.0ROR 15.4 · χ² 477 / p 4e-106	15.0 EB05 11.2 · IC025 +3.1 3/3 methods agree	Reporting / coding artifact	serious n=1 · 92% clinician	no trial data cached
Full blood count decreased	36	15.2 11.0–21.1ROR 15.4 · χ² 464 / p 4e-103	15.0 EB05 11.1 · IC025 +3.1 3/3 methods agree	Lab value / disease marker	serious PRR 18.2	no trial data cached
White blood cell count increased	22	4.9 3.2–7.4ROR 4.9 · χ² 64 / p 7e-16	4.4 EB05 3.1 · IC025 +1.4 3/3 methods agree	Lab value / disease marker	serious PRR 4.0	no trial data cached
Acute myeloid leukaemia	21	11.5 7.5–17.6ROR 11.6 · χ² 191 / p 1e-43	10.6 EB05 6.9 · IC025 +2.5 3/3 methods agree	Not in label — unassessed	serious PRR 10.8 · 90% clinician	no trial data cached
Laboratory test abnormal	17	4.9 3.1–7.9ROR 4.9 · χ² 49 / p 1e-12	4.4 EB05 2.9 · IC025 +1.3 3/3 methods agree	Reporting / coding artifact	serious PRR 2.6	no trial data cached
Blood bilirubin increased	16	5.0 3.1–8.2ROR 5.1 · χ² 48 / p 2e-12	4.4 EB05 2.9 · IC025 +1.3 3/3 methods agree	Lab value / disease marker	serious PRR 3.4	no trial data cached
Fracture	16	7.2 4.4–11.7ROR 7.2 · χ² 79 / p 3e-19	6.1 EB05 3.9 · IC025 +1.8 3/3 methods agree	Not in label — unassessed	serious PRR 7.4	no trial data cached
Platelet count increased	15	9.8 5.9–16.2ROR 9.8 · χ² 110 / p 6e-26	8.4 EB05 5.1 · IC025 +2.1 3/3 methods agree	Lab value / disease marker	serious PRR 6.4	no trial data cached

Unlabeled candidate signals

These flagged terms were not found in the FDA label text and do not match an artifact pattern. They are the pairs that would merit a structured assessment (temporality, dose-response, biological plausibility, consistency across databases, trial or cohort evidence). The screen has not done that; string-matching misses label wording, and a strong PRR can still be stimulated reporting, co-medication, or the disease itself.

Acute myeloid leukaemia — n=21, PRR 11.5

Want to assess one of these properly? The runbook describes the Bradford Hill / trial-evidence workflow used on the assessment page, and handoff_top1000_signals.csv lists the strongest unassessed pairs across all drugs.

Common questions

What are the most reported side effects of Luspatercept?

In FDA FAERS, the most frequently co-reported reaction terms for Luspatercept are haemoglobin decreased, myelodysplastic syndrome, bone pain, full blood count decreased, white blood cell count increased, acute myeloid leukaemia. These are report counts, not rates: FAERS has no denominator, reporting is voluntary and uneven, and a term can be reported because of the illness being treated rather than the drug.

Does Luspatercept have an FDA boxed warning?

No. The FDA label retrieved for Luspatercept has no boxed warning; see the label's Warnings and Precautions for the recognised risks.

Do FAERS signals prove that Luspatercept causes these side effects?

No. A disproportionality signal (PRR, ROR) means a reaction is reported more often with this drug than with others in the database. That can reflect a real effect, but also the disease being treated, stimulated reporting after news or litigation, co-medications, or how reports are coded. Causality needs temporality, dose-response, biological plausibility, consistency across data sources and, ideally, trial or cohort evidence. This page screens each term against the FDA label and ClinicalTrials.gov results; it does not establish causation.

Sources & methods

FDA label via openFDA (set ID 82f4d266-3f52-41eb-86ba-0abf3cf468e8, effective 20260227; matched on openfda.generic_name.exact:"LUSPATERCEPT")
Bayesian shrinkage measures computed offline over all 1,317,300 cached pairs: BCPNN information component (IC, with Norén closed-form IC025) and MGPS empirical-Bayes geometric mean (EBGM, EB05) with a two-component gamma prior fitted by maximum marginal likelihood (α₁=0.57, β₁=0.02, α₂=1.42, β₂=0.70, w=0.17); unstratified
FAERS pair statistics from the OpenPV build of 2026-09-14 (openFDA count= aggregation, field patient.drug.openfda.generic_name.exact, 34 reaction terms, min 3 co-reports); PRR/ROR with 95% CI, chi-square with Yates correction
Serious-only and stratified counts (serious:1, patient.patientsex, primarysource.qualification) from openFDA count queries; serious-only PRR uses the drug serious report total and the term global serious total (N_serious=11,882,979); strata shown only when n ≥ 20
Seriousness and sex counts from openFDA count=serious, patient.patientsex, seriousnessdeath

Page generated 2026-10-08. Label and PubChem text are retrieved automatically and may lag the current label; always check the current prescribing information. OpenPV is a beta research tool of the Open Source Medicine Foundation.