Omeros Reports Final Efficacy and Safety Data from the Narsoplimab Pivotal Trial in HSCT-TMA

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SEATTLE--(BUSINESS WIRE)-- Omeros Corporation (Nasdaq: OMER) today announced final data from its pivotal trial for narsoplimab in hematopoietic stem cell transplant-associated thrombotic microangiopathy (HSCT-TMA), an often-lethal complication of stem-cell transplantation for which there is no approved therapy. Narsoplimab, an inhibitor of mannan-binding lectin-associated serine protease-2 (MASP-2), the effector enzyme of the lectin pathway and activator of the coagulation cascade, is being studied for the treatment of HSCT-TMA patients at high risk for poor outcomes. Narsoplimab has been awarded Breakthrough Therapy designation by U.S. FDA and is the subject of a rolling Biologics License Application (BLA) for HSCT-TMA. The nonclinical and CMC modules of the rolling BLA have already been submitted, and the final sections of the clinical module are in the publishing phase during which finalized documents are electronically processed and integrated for submission in the format required by FDA.

Omeros previously presented preliminary data from its pivotal HSCT-TMA trial. The final data reported today are those that are included in the BLA. In the 28-patient single-arm, open-label pivotal trial in adult HSCT-TMA patients, treatment consisted of narsoplimab administered intravenously once weekly for up to 8 weeks with an extended follow-up period. The study’s patient population was very ill, with the large majority of study patients having multiple comorbidities at baseline (e.g., graft-versus-host disease, significant infections, multi-organ dysfunction, etc.). The FDA-agreed primary endpoint (complete response) required clinical improvement in TMA markers (platelet count and lactate dehydrogenase [LDH]) and in organ function (renal, pulmonary, gastrointestinal or neurological) or freedom from transfusion. Secondary endpoints included 100-day and overall survival as well as change from baseline for individual laboratory markers (platelets, LDH, haptoglobin, hemoglobin and creatinine).

The final results on primary and key secondary endpoints include:

• 61% (95% CI: 40.6% to 78.5%) complete response rate (CRR) in the full analysis set (FAS; patient receiving at least one dose of narsoplimab; p