OMS721 gains orphan designation for HSCT-associated thrombotic microangiopathy


The Food and Drug Administration has granted OMS721 orphan designation for the treatment of hematopoietic stem cell transplant–associated thrombotic microangiopathy (HSCT-TMA).

FDA icon

OMS721 is a monoclonal antibody targeting MASP-2, the effector enzyme of the lectin pathway of the complement system.

The FDA previously granted OMS721 breakthrough therapy designation for HSCT-TMA and orphan designation for the prevention of complement-mediated TMA, including HSCT-TMA.

Omeros, the company developing OMS721, has established a compassionate use program for OMS721, which is active in the United States and Europe.

Phase 3 clinical programs are in progress for OMS721 in atypical hemolytic uremic syndrome, immunoglobulin A nephropathy, and HSCT-TMA. Two phase 2 trials of OMS721 – one in TMA and one in immunoglobulin A nephropathy – are ongoing.

Omeros announced results from the phase 2 TMA trial (NCT02222545) in February. The study includes adults with HSCT-TMA persisting for at least 2 weeks following immunosuppressive regimen modification or more than 30 days post transplant. Patients receive weekly OMS721 treatments for 4-8 weeks at the discretion of the investigator.

At the time of Omeros’s announcement, 18 HSCT-TMA patients had been treated.

These patients had a significantly longer median overall survival at 347 days, compared with historical controls at 21 days (P less than .0001).

Omeros also reported that markers of TMA activity significantly improved following OMS721 treatment.

The mean platelet count increased from 18,100 x 106/mL at baseline to 52,300 x 106/mL (P = .017). The mean lactate dehydrogenase decreased from 591 U/L to 250 U/L (P less than .001). And the mean haptoglobin increased from 8 mg/dL to 141 mg/dL (P = .003).

The most commonly reported adverse events were diarrhea and neutropenia. Four deaths occurred during the study. One of these – attributable to acute renal and respiratory failure – was considered possibly related to OMS721.

Next Article: