Yartemlea

Yartemlea is used to treat hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA) in adults and children 2 years of age and older. It is given as an intravenous infusion once or twice a week, depending on response.

Yartemlea gained FDA approval on December 23, 2025.

Yartemlea is administered once weekly as an intravenous infusion by a healthcare professional.

• The infusion takes 30 minutes.
• The frequency may be increased to twice weekly if TA-TMA signs and symptoms don't improve adequately.

Before receiving Yartemlea, tell your healthcare provider about all your medical conditions, including if you:

• Have any active infections or signs of infection (fever, chills, cough, etc.)
• Have a history of frequent or serious infections
• Have a weakened immune system
• Have recently had or plan to have any vaccinations
• Have had an allergic reaction to narsoplimab or any ingredients in Yartemlea
• Are pregnant or planning to become pregnant. It is unknown if Yartemlea will harm an unborn baby.
• Are breastfeeding or planning to breastfeed. It is unknown if Yartemlea passes into breastmilk.

Common side effects

The most common side effects of Yartemlea are:

• Viral infections
• Sepsis
• Bleeding (hemorrhage)
• Diarrhea
• Vomiting
• Nausea
• Neutropenia (low neutrophil levels)
• Fever
• Fatigue
• Low potassium levels (hypokalemia).

Serious side effects and warnings

Serious Infections

Yartemlea can increase your risk of serious, potentially life-threatening infections. In clinical trials, 36% of patients developed serious infections, including sepsis, pneumonia, bloodstream infections, and fungal infections. Watch for these infection warning signs and seek medical care immediately:

• Fever or chills
• Persistent cough or trouble breathing
• Unusual fatigue or weakness
• Painful urination or frequent urination
• Diarrhea or abdominal pain
• Skin redness, warmth, or swelling
• Confusion or mental changes

If you have an active infection when starting Yartemlea, your doctor will monitor you closely. Don't ignore symptoms—report any signs of infection to your healthcare provider right away.

To report suspected adverse reactions, contact Omeros Corporation at 1-844-YARTEM1 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Yartemlea (narsoplimab) works by blocking a specific enzyme (MASP-2) in one branch of the immune system's complement pathway. This prevents immune-triggered damage to blood vessel linings and cells, which occurs in TA-TMA, which is a transplant complication. Yartemlea only targets this one pathway, leaving other immune functions intact.

Yartemlea belongs to the drug class called MASP-2 inhibitors.

Dose of Yartemlea for TA-TMA

Weighing 50 kg or more:

• 370 mg given as an intravenous (IV) infusion over 30 minutes once weekly
• Increase to twice weekly if TA-TMA signs and symptoms don't improve adequately

Weighing less than 50 kg:

• 4 mg/kg given as an intravenous (IV) infusion over 30 minutes once weekly
• Increase to twice weekly if TA-TMA signs and symptoms don't improve adequately.

Tell your healthcare provider or pharmacist about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

No formal clinical drug interaction studies have been performed with Yartemlea.

Yartemlea is manufactured by Omeros Corporation, 201 Elliott Avenue West, Seattle, WA 98119. US license 2141.