FDA CRL - Omeros Corporation

On October 15, 2021, the U.S. Food and Drug Administration (FDA) issued a Complete Response Letter to Omeros Corporation regarding its Biologics License Application for OMS721, intended to treat hematopoietic stem cell transplantation-thrombotic microangiopathy (HSCT-TMA). Under the regulatory framework of the Public Health Service Act, the FDA determined that the application could not be approved in its current form because the data failed to demonstrate substantial evidence of effectiveness.

Major issues identified by the agency included significant flaws in clinical trial conduct, where nearly 40% of patients did not meet enrollment criteria. The FDA noted that concurrent illnesses and changes in other medications made it difficult to prove that patient improvements were directly caused by OMS721. Furthermore, the agency recalculated the treatment success rate to be 43%, significantly lower than the company’s reported 61%, after concluding that five patients were incorrectly classified as responders. The FDA also found the company's historical literature comparisons to be methodologically weak and noted a lack of data showing that lab results translate into actual clinical benefits.

To move forward, Omeros must provide additional clinical data, such as a new randomized controlled trial or a more robust analysis using a valid comparison group. The company is also required to submit a comprehensive safety update, justify dosing for patients undergoing plasma exchange, and provide further manufacturing data regarding product stability and container safety. Omeros must address these deficiencies within one year to continue the approval process.