FDA Approves Yartemlea, the First and Only Treatment for Transplant-Related Blood Vessel Damage

Yartemlea (narsoplimab-wuug) is a new medicine approved by the FDA for treating a rare and serious condition called transplant-associated thrombotic microangiopathy (TA-TMA) in adults and children ages 2 years or older.

TA-TMA is a serious complication that happens when the inner lining of blood vessels is damaged by things such as transplant treatments, infections, medicines (immunosuppressants), or transplant-related problems such as graft versus host disease or other complications. This damage triggers the lectin pathway of the complement system (a part of your immune system), which plays a major role in this disease. TA-TMA can happen after both self-donor (autologous) and donor (allogeneic) stem cell transplants, but it’s more common after allogeneic transplants.

Around 30,000 allogeneic transplants are done each year in the U.S. and Europe, and up to 56% of patients may develop TA-TMA. The damage caused by TA-TMA can lead to low platelet counts, kidney problems, and even organ failure, with the death rate exceeding 90% in severe cases. Survivors often face long-term kidney issues, sometimes requiring lifelong dialysis.

Yartemlea is the first and only approved drug that targets the lectin pathway of the immune system. It works by blocking MASP-2, an enzyme that activates the lectin pathway, leading to injury of small blood vessels and clot formation in conditions such as TA-TMA. So, by selectively inhibiting this pathway, Yartemlea helps prevent further cell damage and reduces complications like clotting or kidney problems, without affecting normal functions of other essential pathways in the complement system that are required for fighting infections.

This approval matters because TA-TMA can be a life-threatening and frequently fatal complication that doesn’t have many treatment options. Yartemlea offers quick and reliable access to a treatment option that may help manage TA-TMA in more patients, especially in critically ill children ages 2 years or older who have organ damage and have not responded to previous therapies.

Why Was It Approved?

The FDA’s approval of Yartemlea was based on clinical studies that showed that it was safe and effective in treating high-risk TA-TMA, significantly improving patient outcomes and survival, especially for those who haven’t responded to other treatments.

Approval was based on a pivotal study involving 28 adults with TA-TMA and supported by additional data from an expanded access program (EAP) that included 221 patients (adults and children) either for whom Yartemlea was a first-line treatment or who were critically ill with high‑risk TA‑TMA and had failed or stopped other therapies. Results showed that a complete response, meaning significant improvements in lab results (platelet counts and lactate dehydrogenase levels) plus better organ functioning or no longer needing transfusions, was seen in 61% of patients in the pivotal study and in 68% of evaluable patients in the EAP. The 100-day survival rate was 73% in the main study and 74% in the evaluable EAP patients. Yartemlea also showed a significant survival benefit, with 50% in the EAP surviving for a year, compared to less than 20% with previous therapies.

Common side effects included a higher chance of getting viral infections, sepsis (a serious infection in the blood), bleeding, diarrhea, vomiting, nausea, fever, fatigue, and low potassium levels and white blood cell counts. More than a third of people in the study had serious side effects, including kidney problems, confusion, breathing failure, severe infections, sepsis, septic shock, and fluid in the lungs (pulmonary edema). Some also had life-threatening problems like sepsis or septic shock. No new safety concerns were found in patients treated with Yartemlea in the EAP.

What Do I Need to Know?

Yartemlea is given through an intravenous (IV) infusion, which means it goes directly into a vein. Most people get it once a week, but if your condition doesn’t improve, your health care provider may increase your dose to twice a week. The dose depends on your body weight, and each infusion takes about 30 minutes. If you miss a dose, take it as soon as you can and then go back to your usual schedule. This medicine must be prepared and given by trained staff. It should not be mixed with other medicines in the same IV line.

There are no known conditions that can prevent you from taking Yartemlea. But serious infections, including viral illnesses, pneumonia, fungal infections, blood infections (sepsis), stomach infections, lung infections, and urinary tract infections, can happen during treatment. Your health care provider will watch for signs of infection and treat them quickly if needed.

Let your health care provider know about your medical conditions, any present or recurrent infections, and all the medicines that you take, including over-the-counter products, herbal remedies, and vitamin supplements. The effects of this medicine during pregnancy and breastfeeding are not yet known, so it is important to consult with a health care provider before using it in these situations.

Contact your health care provider right away if you notice any signs or symptoms of infection such as a fever, sweating or chills, flu-like symptoms, coughing or trouble breathing, or pain while urinating.

Yartemlea may not be available everywhere yet, and insurance coverage can vary. If you’ve had a stem cell transplant and are diagnosed with TA-TMA, talk with your health care provider to see if this treatment might be right for you.