Omeros Wins FDA Approval for YARTEMLEA, First-Ever Treatment for Often-Fatal Transplant Complication

December 24, 2025 · by Fintool Agent

OMERNVO

Omeros Corporation+1.27% stock surged 76% on Christmas Eve after the FDA granted approval to YARTEMLEA (narsoplimab), making it the first and only treatment ever approved for hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA)—an often-fatal complication that can affect up to 56% of transplant recipients and carries mortality rates exceeding 90% in severe cases. 1

The approval marks the culmination of a decade-long regulatory journey for the Seattle-based biotech, which previously received a Complete Response Letter from the FDA before resubmitting with compelling survival data showing 3- to 4-fold lower mortality risk compared to supportive care alone. 2

The Market Reaction

OMER shares closed at $15.36, up $6.61 (+76%) on massive volume of 24.5 million shares—nearly 10 times the average daily trading volume. The stock touched a new 52-week high of $17.65 intraday, a dramatic reversal from its 52-week low of $2.95 earlier this year.

The approval transforms Omeros from a clinical-stage biotech burning cash with no commercial products to a company with a first-in-class approved therapy addressing a significant unmet medical need. The company plans to launch YARTEMLEA in the U.S. in January 2026. 3

Ask Fintool AI Agent

Show me Omeros' stock price history and compare it to biotech indices over the past year

Clinical Data: A Breakthrough for Transplant Patients

The FDA's decision was supported by robust efficacy data showing complete response rates of 61% in the pivotal 28-patient trial and 68% in the 221-patient Expanded Access Program. 1

Perhaps more importantly, 100-day survival from TA-TMA diagnosis was approximately 73-74% across studies—remarkable given that all patients met international criteria for high-risk disease with poor prognosis. In peer-reviewed publications, YARTEMLEA treatment was associated with a 3- to 4-fold lower risk of mortality compared to external controls receiving only supportive care. 2

"This approval is a long-awaited breakthrough in hematopoietic cell transplantation and TA-TMA care," said Miguel-Angel Perales, M.D., Chief of the Adult Bone Marrow Transplantation Service at Memorial Sloan Kettering Cancer Center. "As the first and only drug approved for TA-TMA, narsoplimab is a practice-changing advance for patients facing this devastating complication." 8

Ask Fintool AI Agent

Pull Omeros' recent SEC filings and earnings call transcripts to see management commentary on the commercial launch strategy

A Differentiated Safety Profile

Unlike off-label C5 inhibitors such as eculizumab and ravulizumab that are sometimes used in TA-TMA, YARTEMLEA targets MASP-2—the effector enzyme of the lectin pathway of complement. This mechanism preserves classical and alternative pathway functions critical for immune defense against infection. 1

The distinction matters clinically: a retrospective study found that pediatric TA-TMA patients treated with the C5 inhibitor eculizumab had 8.5-fold higher bacteremia rates and 6-fold higher infection-related mortality compared to controls. 2

YARTEMLEA received approval without a Boxed Warning, without a Risk Evaluation and Mitigation Strategy (REMS), and without requiring pre-treatment vaccinations—a cleaner label than many complement-targeting therapies. 3

The Long Road to Approval

YARTEMLEA's path to approval was anything but straightforward. The FDA initially issued a Complete Response Letter, requesting additional efficacy data. Omeros responded by conducting a rigorous statistical analysis comparing survival in narsoplimab-treated patients to an external registry of TA-TMA patients from the Kyoto Transplant Group. 4

The results—showing highly significant, 3-fold improvement in overall survival—convinced the FDA to accept the resubmission and ultimately grant approval. 5

The Market Opportunity

Approximately 30,000 allogeneic stem cell transplants are performed annually in the U.S. and Europe. Recent studies estimate that TA-TMA develops in up to 56% of allogeneic transplant recipients. Mortality in severe TA-TMA can exceed 90%, and survivors frequently face long-term renal complications including dialysis dependence. 6

Until today, there was no approved treatment—physicians relied on supportive measures like modifying immunosuppressants, which can paradoxically increase the risk of graft-versus-host disease. 7

Omeros has secured dedicated billing and reimbursement codes: an ICD-10-CM diagnosis code (M31.11) specific to TA-TMA and ICD-10-PCS procedure codes for narsoplimab administration. The company also expects to receive a New Technology Add-on Payment (NTAP) from Medicare to support hospital reimbursement. 8

Ask Fintool AI Agent

What are analyst estimates and price targets for Omeros following this FDA approval?

Financial Transformation

The approval comes at a pivotal moment for Omeros. The company has been burning approximately $25-30 million per quarter with no commercial revenue, and as of Q3 2025 had only $2.4 million in cash and $36.1 million in cash and investments. 1

However, the company is set to receive $240 million in upfront cash from its October 2025 deal with Novo Nordisk-0.66%, in which the Danish pharma giant acquired global rights to Omeros' MASP-3 inhibitor zaltenibart for up to $2.1 billion in total potential value. 2

Upon closing the Novo Nordisk transaction (expected Q4 2025), Omeros will use proceeds to fully repay its $67.1 million secured term loan and the remaining $17.1 million of its 2026 convertible notes. Management has stated the company expects to potentially be cash flow positive in 2027. 7

Ask Fintool AI Agent

Compare Omeros' valuation to other rare disease biotechs with recently approved first-in-class therapies

What to Watch

January 2026 Launch: The commercial rollout will be the first test of Omeros' market access strategy. The company has assembled a hematology-experienced sales force and claims transplant centers are "ready to go" with identified champions for TA-TMA treatment. 1

European Decision (Mid-2026): A marketing authorization application is under review by the European Medicines Agency, which would significantly expand the addressable market. 2

Pipeline Advancement: With YARTEMLEA approved and the Novo Nordisk deal funding the balance sheet, Omeros can advance OMS1029 (long-acting MASP-2 antibody), its MASP-2 small molecule program, and its oncology platform—including OncotoX-AML, which the company expects to enter the clinic in 2027. 3

Conference Call: Management will host a call on December 29, 2025 at 4:30 p.m. ET to discuss the approval. 4

Related

• Omeros Corporation+1.27%
• Novo Nordisk A/s-0.66%