FDA Approves First Treatment for Fatal Complication of Stem Cell Transplants

A significant breakthrough in the treatment of a severe complication from stem cell transplants has occurred with the FDA’s approval of the first therapy specifically designed for this condition. The therapy, developed by the biotechnology company Omeros, targets hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA), a rare but often fatal complication affecting both adults and children aged two and older.

On December 24, 2023, the FDA granted approval for narsoplimab, marketed under the brand name Yartemlea. This condition arises from blood clots forming in small vessels, leading to damage in vital organs. Previously, treatment options were mainly supportive, leaving a significant gap in effective therapies.

The Seattle-based company focuses on drugs that influence the complement system, an integral part of the immune system. Yartemlea functions by inhibiting MASP-2, a critical enzyme within the lectin pathway of the complement system. This inhibition is believed to prevent cellular damage in small blood vessels caused by the pathway’s activity, while preserving another pathway essential for immune responses.

Yartemlea is administered as a weekly infusion, with dosages adjusted according to the patient’s weight. The FDA’s approval was based on a single-arm, open-label study involving 28 adults with TA-TMA. The findings indicated a complete response in 61% of participants, with 17 out of 28 adults showing notable improvement in key laboratory markers associated with the condition. Additionally, data from an expanded access program involving 19 patients showed a complete response rate of 68%.

Survival rates were also promising. Within 100 days of diagnosis, the survival rate stood at 73% for the TA-TMA study and 74% for the expanded access program. All patients in the clinical trials had multiple risk factors, with various adverse reactions reported, including viral infections, sepsis, and diarrhea. Importantly, no new significant safety issues emerged during the trials, and Yartemlea does not carry a black box warning.

The FDA approval marks a pivotal moment for Omeros, as Yartemlea becomes the company’s first product to receive regulatory endorsement. A U.S. launch is anticipated for January 2024, with a regulatory decision in Europe expected by mid-2026. Omeros has scheduled a conference call to discuss the approval and its implications on December 29, 2023.

In addition to Yartemlea, Omeros is advancing its research and development of complement system drugs, which recently led to the creation of a MASP-3 inhibitor named zaltenibart. In October 2023, Novo Nordisk acquired global rights to zaltenibart for $240 million, positioning it for Phase 3 testing in a rare blood disorder known as paroxysmal nocturnal hemoglobinuria.

This approval follows a series of significant regulatory decisions from the FDA, enhancing the treatment landscape for various conditions. For instance, recent approvals included new drugs for obesity, heart conditions, and rare diseases, showcasing a growing commitment to addressing unmet medical needs.

As the landscape of medical treatments evolves, Omeros’s Yartemlea represents a crucial step forward in managing a previously challenging complication of stem cell transplants, offering new hope to patients and their families.