Omeros’ efforts to get its transplant drug to market have already suffered one FDA rejection. Now, the biotech’s second shot at approval has been pushed back by three months.
Omeros had been given a deadline of Sept. 25 for the agency to reconsider whether to approve the anti-MASP-2 antibody narsoplimab for hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA). The potentially life-threatening complication of transplant procedures can lead to generalized endothelial dysfunction and multiorgan injury.
The FDA had requested further information in relation to Omeros’ application and, after receiving the biotech’s response, informed the company that the decision date has been pushed back to Dec. 26.
The agency explained that “assuming no major deficiencies are identified during its review, labeling discussions are planned to begin no later than Oct. 2025,” according to Omeros’ second-quarter earnings release.
“To date, all analyses requested by FDA as part of its review have been consistent with and have provided statistically significant support of narsoplimab’s benefit demonstrated in the analyses submitted as part of the BLA resubmission,” the company added.
Delays to FDA approval decisions have been making headlines this year, raising concerns that the approval system is being impacted by mass layoffs at the agency.
Omeros submitted the latest approval application off the back of a new data analysis that found the monoclonal antibody improved overall survival by 68%. The Seattle-based biotech had originally evaluated the drug among 28 patients with TA-TMA in a phase 2 trial that wrapped in 2020. Omeros then asked the FDA to approve narsoplimab based on the study, a request the agency rejected in 2021, raising concerns about estimating treatment effect based on the data provided and requesting additional information.
Undeterred, Omeros formally challenged the decision in an appeal that opened the door to a potential path forward in the indication. The FDA officially recommended Omeros compare overall survival from time of first dosing in the 28 patients from the pivotal trial to overall survival data from more than 100 TA-TMA patients included in an external control registry, none of whom received narsoplimab. Omeros took these data to the agency as part of the latest application in March.
“Working closely with FDA, we continue preparing for the anticipated approval and subsequent launch of narsoplimab in TA-TMA, an indication with an increasingly large and recognized unmet need for which there is no approved treatment,” Omeros CEO Gregory Demopulos, M.D., said in the release.
With its efforts focused on narsoplimab, Omeros announced earlier in the year that it was hitting pause on the next clinical steps for two other important assets—the MASP-3 inhibitor zaltenibart and a long-acting MASP-2 inhibitor dubbed OMS1029.
Zaltenibart has been readied for a phase 3 trial for paroxysmal nocturnal hemoglobinuria, while OMS1029 is being lined up for a phase 2 study in a yet-to-be-decided indication.
“With substantial industry interest across our assets, partnering discussions continue advancing, and we see a number of potential value-driving milestones lining up nicely throughout the remainder of 2025 and into 2026,” Demopulos said.