Omeros is putting up its monoclonal antibody up for FDA approval—again. This time, the resubmission will be based on a new data analysis that found the investigational treatment improved overall survival by 68% for patients with a rare, life-threatening complication of a bone marrow transplant.
Given the results, Omeros hopes the anti-MASP-2 antibody narsoplimab will become the first treatment on the market in the indication, according to a Dec. 19 release.
The biotech’s stock has jumped 70% since market close yesterday, rising from $7.46 per share last night to $12.71 as of 11 a.m. ET today.
Omeros is testing narsoplimab as a treatment for hematopoietic stem cell transplant-associated thrombotic microangiopathy (TA-TMA) in both adults and children who have had hematopoietic stem cell transplantation (HSCT).
The Seattle-based biotech evaluated its candidate among 28 patients with TA-TMA in a phase 2 trial, dubbed OMS721-TMA-001, that wrapped in 2020. Omeros then asked the FDA to approve the monoclonal antibody 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. A resubmission would have to include “a comparison of the existing response data from the completed pivotal trial to a threshold derived from an independent literature analysis and evidence of increased survival from patients in the pivotal trial compared to an appropriate historical control group,” Omeros explained in 2022.
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 instructed an independent statistical group to incorporate the recommendation into the final analysis, with the findings shared today revealing that the anti-MASP-2 antibody hit the primary endpoint. Patients receiving the investigational treatment demonstrated a 68% increase in overall survival compared to the registry patients, a statistically significant finding (p-value less than 0.00001).
“As an investigator in the pivotal clinical trial and having since requested and used narsoplimab in a good number of very sick TA-TMA patients through the expanded access program, we have seen first-hand the impressive benefits of narsoplimab in these high-risk patients,” Alessandro Rambaldi, M.D., professor of hematology at the University of Milan and head of the hematology and bone marrow transplant unit at ASST Papa Giovanni XXIII, said in the release.
“While we do not use C5 inhibitors in our transplant patients, nearly 50 patients in the expanded access program received narsoplimab after failing or stopping C5 inhibitors and other off-label treatments, with TA-TMA resolving with narsoplimab in 46% and 50% of these adults and children, respectively, which is quite remarkable,” Rambaldi continued.
Across all related clinical trials to date, narsoplimab has been well tolerated, with no concerning safety signals identified, according to Omeros.
“Given the primary analysis results, we will resubmit the narsoplimab BLA for TA-TMA as quickly as possible followed by our planned submission of the corresponding European marketing authorization application in the second quarter of 2025,” Omeros CEO Gregory Demopulos, M.D., said in the release.
Additional analyses that will be included in a biologics license application for TA-TMA are being conducted and will be shared publicly when available, according to the biotech.
It’s been a long journey for narsoplimab, which has nabbed breakthrough therapy and orphan drug tags in the indication, for which no approved therapy or standard of care currently exists.
Previously, the investigational antibody was being tested in a phase 3 trial for kidney disease patients, but Omeros discontinued the study in 2023 after an interim analysis found it was destined to fail.
Omeros is still assessing narsoplimab’s potential in COVID-19 and acute respiratory distress syndrome, according to the company’s online pipeline.