Drug Update · Hematology

narsoplimab: FDA Approves for TA-TMA; 61% TMA Response

July 19, 2026

Approval date

2025-12-23

Indication

Treatment of adult and pediatric patients 2 years and older with hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA)

Primary efficacy result

TA-TMA response 17/28 (61%) in the TA-TMA Study

Pivotal study

TA-TMA Study (Study TMA-001; NCT02222545)

Clinical Perspective

This approval affects clinicians caring for adults and pediatric patients 2 years of age and older who develop hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA). The FDA decision is supported by a single-arm TA-TMA Study (Study TMA-001) showing a TA-TMA response of 61% and by expanded-access data reporting 67% response in pediatric patients and 69% in adult patients. What are the longer-term outcomes and optimal timing of narsoplimab relative to other TA-TMA management strategies?

Dr. Shruti Pandey · Hematology

The U.S. Food and Drug Administration approved Yartemlea (narsoplimab-wuug) injection to treat adult and pediatric patients 2 years of age and older with hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA) on December 23, 2025 ^[1]^[3]. The approval was supported by a single-arm, open-label TA-TMA Study (Study TMA-001) in which a TA-TMA response was achieved in 17/28 patients (61%) and by evaluable expanded access program data showing responses in pediatric and adult patients ^[1]^[2]^[3].

Clinical Context

Narsoplimab (Yartemlea) is a monoclonal antibody that inhibits mannan-binding lectin-associated serine protease 2 (MASP-2), the effector enzyme of the lectin pathway of complement, and is developed by Omeros Corporation ^[3]^[2]. The FDA described TA-TMA as a serious, life-threatening complication of hematopoietic stem cell transplant in which microvascular thrombosis can lead to organ damage including kidneys, cardiovascular system, and gastrointestinal tract ^[1]. The FDA press release and prescribing information note that Yartemlea is the first FDA-approved treatment specifically for TA-TMA ^[1]^[3]. Study evidence included a single-arm open-label trial of 28 adults plus evaluable patient-level data from an expanded access program ^[2]^[3].

Key Findings

The TA-TMA Study (Study TMA-001) showed a TA-TMA response of 17/28 (61%) in patients with TA-TMA; the primary efficacy assessment was TMA response defined by improvement in two laboratory TMA markers (LDH and platelet counts) and either organ function improvement or independence from transfusions ^[2]^[3].
In evaluable expanded access program patients, TA-TMA response was 4/6 (67%) in pediatric patients and 9/13 (69%) in adult patients using the same response criteria ^[3]^[1].
Component outcomes in the TA-TMA Study included improvement in platelet count (17/28; 61%) and LDH improvements; improvement in organ function was reported in 20/27 patients where data were evaluable ^[3].
In the TA-TMA Study, 100-day survival from time of TMA diagnosis was 73.4% (95% CI: 52.2, 86.4); in the expanded access cohort (N = 19), 100-day survival was 73.7% (95% CI: 47.9, 88.1) ^[3].

Safety & Tolerability

The most common adverse reactions reported were viral infections, sepsis, hemorrhage, diarrhea, vomiting, nausea, neutropenia, fever, fatigue, and low potassium ^[1]^[3].
The FDA and prescribing information advise monitoring patients for signs of serious infections ^[1]^[3].

Study Design

The approval was based on a single-arm, open-label study (TA-TMA Study; Study TMA-001) that enrolled 28 adult patients with TA-TMA following hematopoietic stem-cell transplantation and on evaluable patient-level data from 19 adult and pediatric patients enrolled in an expanded access program ^[2]^[3]. The primary efficacy assessment for both the TA-TMA Study and the EAP was TMA response defined as improvement in LDH and platelet counts plus either organ function improvement or independence from transfusions ^[2]^[3]. Additional study details and patient-level demographics are in the prescribing information and Drug Trials Snapshot ^[2]^[3].

FAQ

Q1 What is Yartemlea (narsoplimab) approved for?

Yartemlea (narsoplimab-wuug) is approved for the treatment of adult and pediatric patients 2 years of age and older with hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA). The FDA labeled Yartemlea as the first approved treatment for TA-TMA and stated the approval was based on a single-arm trial and expanded-access data demonstrating TMA responses in treated patients.

Q2 How does narsoplimab work?

Narsoplimab is a MASP-2 inhibitor that targets mannan-binding lectin-associated serine protease 2, the effector enzyme of the lectin pathway of complement. By inhibiting MASP-2, narsoplimab blocks lectin-dependent activation of complement component C3 and C4; in TA-TMA this mechanism is described as preventing lectin pathway-mediated cellular injury including endothelial cell injury in small blood vessels.

Q3 What is the recommended dose of Yartemlea?

For patients weighing greater than or equal to 50 kg the recommended dosage is 370 mg given as an intravenous infusion over 30 minutes once weekly; for patients weighing less than 50 kg the recommended dosage is 4 mg/kg given as an intravenous infusion over 30 minutes once weekly. The label allows increasing frequency to twice weekly if there is inadequate improvement in TA-TMA signs and symptoms. Clinicians should consult current prescribing information for complete dosing guidance.

Q4 What are the most common side effects of narsoplimab?

The most common adverse reactions reported in the FDA materials and prescribing information include viral infections, sepsis, hemorrhage, diarrhea, vomiting, nausea, neutropenia, fever, fatigue, and low potassium. The FDA and prescribing information advise monitoring patients for signs of serious infections during treatment with narsoplimab.

Clinicians should consult current prescribing information for complete dosing guidance.

narsoplimab: FDA Approves for TA-TMA; 61% TMA Response

narsoplimab: FDA Approves for TA-TMA; 61% TMA Response

Clinical Perspective

Clinical Context

Key Findings

Safety & Tolerability

Study Design

FAQ

References

Get weekly clinical updates for Hematology in your inbox.

Related Clinical Updates

AURORA: Bitopertin Reduced Protoporphyrin‑IX 49.8% in Erythropoietic Protoporphyria

FDA Approves Daratumumab for NDMM Ineligible for ASCT: 52.3% MRD

FDA Approves Fitusiran for Hemophilia A/B: Median Treated ABR 3.7

Verified HCP Portal