Yartemlea offers hope for TA-TMA patients who previously had no FDA-approved options
January 27th, 2026: First Commercial Sales AnnouncedNew here? Follow stories to track developments over time. Create a free account to get updates when stories you care about change.
For decades, patients who developed transplant-associated thrombotic microangiopathy (TA-TMA) after stem cell transplants faced a grim reality: a life-threatening complication with no approved treatment. Mortality rates for high-risk cases reached 80-90%. In December 2025, the FDA approved Yartemlea, the first therapy for this condition, marking Seattle-based Omeros Corporation's first drug approval after 31 years. The company launched commercially on January 2, 2026, announced pricing at $36,000 per vial on January 7, and by late January both adult and pediatric patients were receiving treatment at transplant centers nationwide.
Yartemlea works by blocking MASP-2, an enzyme in the complement immune system that drives the blood vessel damage underlying TA-TMA. Clinical trials showed 61% of patients achieved complete response, with 73% surviving at least 100 days—roughly triple the survival rate seen in untreated patients with similar disease severity. The drug's early commercial uptake includes patients who recently failed prior off-label C5-inhibitor regimens, demonstrating real-world adoption of its distinct mechanism. Medicare's new technology add-on payment is expected in October 2026 to facilitate hospital reimbursement, while European regulatory review continues with a decision anticipated mid-2026.
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Seattle-based biotech focused on complement pathway inhibitors for rare diseases.
Federal agency responsible for protecting public health through regulation of drugs, biologics, and medical devices.
Omeros announces patients are receiving Yartemlea treatment following completed distributor shipments. Both adult and pediatric TA-TMA patients being treated, including those who failed prior off-label C5-inhibitor therapy, in hospital and outpatient settings.
Yartemlea becomes fully available to patients, with patient support program expected in Q1 2026.
Company announces $36,000 per-vial wholesale acquisition cost for Yartemlea, with typical treatment requiring 8-10 vials. Stock rises approximately 4% on pricing news.
Omeros launches Yartemlea in the United States with dedicated billing codes in place for reimbursement.
After 31 years in business, Omeros receives its first major therapeutic drug approval for TA-TMA treatment.
Office of New Drugs recommends comparing trial results to external historical control registry data.
Company files formal dispute resolution request challenging the complete response letter.
Agency rejects initial application, citing difficulty estimating treatment effect from single-arm trial without a control group.
FDA accepts Omeros's biologics license application for narsoplimab in TA-TMA.
Agency recognizes OMS721's potential to address serious unmet medical need in stem cell transplant patients.
Phase 2 trial shows clinically meaningful improvements in stem cell transplant-associated TA-TMA patients.
Early results show OMS721 activity in patients with various thrombotic microangiopathies including TA-TMA.
Omeros initiates first-in-human testing of its MASP-2 inhibitor in healthy volunteers.
Gregory Demopulos founds Omeros Corporation to develop novel therapeutics.
Discussed by: Transplant medicine specialists, hematology publications
With no competing approved therapies and strong clinical data, Yartemlea achieves rapid adoption at major transplant centers. Medicare's new technology add-on payment (expected October 2026) removes reimbursement friction. Peak annual sales reach analyst estimates of approximately $300 million as the drug becomes integrated into standard TA-TMA management protocols.
Discussed by: Omeros investor communications, European Medicines Agency filings
The EMA is currently reviewing Omeros's marketing authorization application, with a decision expected mid-2026. European approval would significantly expand the addressable patient population and validate the drug across multiple regulatory jurisdictions.
Discussed by: Market analysts, transplant researchers
Although eculizumab is not FDA-approved for TA-TMA, some transplant centers already use it off-label based on pediatric data showing 56% one-year survival. If physicians remain comfortable with existing practice patterns, Yartemlea adoption could be slower than expected despite its approved status and different mechanism targeting MASP-2 rather than C5.
Discussed by: Omeros pipeline disclosures, nephrology researchers
Omeros is pursuing narsoplimab for IgA nephropathy (a kidney disease affecting millions globally) and has completed a Phase 1 trial of OMS1029, a long-acting MASP-2 inhibitor. Success in these larger indications would transform Omeros from a rare disease company into a major complement therapeutics player.
The FDA approved eculizumab (Soliris), developed by Alexion Pharmaceuticals, as the first complement inhibitor for paroxysmal nocturnal hemoglobinuria (PNH). The approval came through accelerated review based on small trials in 87 transfusion-dependent patients, demonstrating that complement-targeting drugs could reach market despite limited traditional evidence.
Eculizumab transformed PNH from a fatal disease into a manageable condition. Alexion priced it at approximately $400,000 per year, making it one of the world's most expensive drugs.
The approval validated complement inhibition as a therapeutic strategy and opened the door for drugs targeting different parts of the complement cascade, including Yartemlea's focus on the lectin pathway.
Eculizumab's approval despite small trial sizes set a regulatory precedent that Omeros eventually leveraged. Both drugs target complement-mediated diseases, but Yartemlea blocks MASP-2 while eculizumab blocks C5, representing different therapeutic approaches within the same biological system.
Before the Orphan Drug Act of 1983, only 38 drugs existed for rare diseases because pharmaceutical companies lacked economic incentives to develop treatments for small patient populations. The law provided tax credits, market exclusivity, and FDA fee waivers to encourage orphan drug development.
Orphan drug approvals increased from near zero to steady annual growth. By 2020, the FDA had approved 599 orphan products.
By 2022, drugs treating rare diseases represented nearly half (49%) of all novel FDA approvals. However, only about 5% of the estimated 7,000-10,000 known rare diseases have an approved treatment.
Yartemlea received orphan drug designation for TA-TMA, providing Omeros with seven years of market exclusivity and reduced regulatory fees. The approval adds TA-TMA to the growing list of rare diseases with their first-ever approved treatment.
Throughout the 2010s, the FDA increasingly approved cancer drugs based on single-arm trials measuring tumor response rather than placebo-controlled survival studies. This reflected a shift toward faster approvals for serious diseases with no existing treatments, though it also generated debate about evidence standards.
Dozens of cancer therapies reached patients years earlier than traditional trial designs would have allowed.
The approach established precedent for approving drugs in serious conditions where placebo controls would be unethical, though some approvals were later withdrawn when confirmatory trials failed.
The FDA initially rejected Yartemlea in 2021 because its single-arm trial made treatment effect difficult to estimate. Omeros succeeded by providing external historical comparison data, demonstrating how companies can navigate regulatory concerns about non-randomized evidence in rare disease settings.