Omeros has announced positive data using OMS721, the lead human monoclonal antibody for its mannan-binding lectin-associated serine protease-2 (MASP-2) program, to inhibit thrombus formation in an ex vivo pathophysiologic system of human atypical hemolytic uremic syndrome (aHUS), a form of thrombotic microangiopathy (TMA).

TMAs are a family of rare, debilitating and life-threatening disorders characterized by excessive thrombi (clots) in the microcirculation of the body's organs, most commonly the kidney and brain. OMS721 currently is in a phase II clinical program evaluating the drug's efficacy in treating TMAs, including aHUS.

The data resulted from studies in a well-established experimental model of TMA aimed at assessing the potential therapeutic benefits of OMS721 in TMA using serum samples from aHUS patients with different etiologies obtained during the acute phase of disease as well as during remission. The experimental model is based on the finding that sera from aHUS patients promote the formation of thrombi on human microvascular endothelial cells, the defining pathological feature of TMA.

The studies reported showed that OMS721 significantly inhibited thrombus formation when added to serum samples from aHUS patients obtained during the acute phase of disease (p<0.01) as well as during remission (p<0.0001). OMS721 was as effective at inhibiting thrombus formation as the positive control in the studies - soluble complement receptor 1, an agent that completely blocks the complement system.

Earlier this year, Omeros reported that OMS721 also significantly inhibited complement deposition compared to control treatment in an experimental ex vivo pathophysiologic system of complement activation in TMA, again using serum samples from aHUS patients obtained during the acute phase of disease (p<0.01) and during remission (p<0.001).

"We believe that the notable anti-complement and anti-thrombotic activities of OMS721 in serum samples from aHUS patients bode well for the therapeutic potential of OMS721 in thrombotic microangiopathies," said prof. Remuzzi, M.D., FRCP, research coordinator at the Mario Negri Institute.