Omeros (OMER) Announces Positive OMS721 Phase 2 Data in HSCT-TMA; TMA Markers Improved Over Time

October 20, 2016 10:30 AM EDT

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Omeros Corporation (Nasdaq: OMER) announced positive results in patients with hematopoietic stem cell transplant-associated thrombotic microangiopathy (HSCT-TMA) from the company's Phase 2 clinical trial of OMS721 in TMAs, with clinically meaningful improvement in measures of red blood cell destruction, specifically lactate dehydrogenase (LDH) and haptoglobin levels (p < 0.01 and p < 0.06, respectively). Severe HSCT-TMAs carry a high mortality rate. OMS721 is Omeros' lead human monoclonal antibody targeting mannan-binding lectin-associated serine protease-2 (MASP-2). In addition to its Phase 2 clinical program in TMAs, OMS721 is currently in a Phase 3 program for patients suffering from atypical hemolytic uremic syndrome and in a Phase 2 program for renal diseases, including immunoglobulin A (IgA) nephropathy (or Berger’s disease) and membranous nephropathy.

All HSCT-TMA patients in the Phase 2 open-label clinical trial are adults who had received stem-cell transplantation for hematological malignancies. Inclusion criteria for these patients included low platelet count, hemolytic anemia (i.e., destruction of red blood cells within small blood vessels) and the requirement that the patients had not responded to attempted treatment of the TMA with modification of their immunosuppressive drugs. Changing the immunosuppressive regimen is common practice in HSCT patients who develop a TMA, and those who do not respond to these drug changes frequently die. Three HSCT-TMA patients, all of whom had failed immunosuppressive modification, completed treatment with OMS721 for up to 8 weeks. Two other patients discontinued OMS721 early in their treatment courses, one later relapsed and the other’s treatment was changed to palliative care only.

Across all three patients completing treatment, mean TMA markers improved over time. The mean LDH level decreased from a baseline of 672 U/L by as much as 380 U/L (p < 0.01). The mean haptoglobin increased over 1.54 g/L from a baseline of 0.33 g/L (p < 0.06). LDH and haptoglobin are measures of hemolytic anemia. The mean platelet count increased as much as 57,000/μL from a baseline of 18,000/μL but did not reach statistical significance in this small number of patients. Creatinine remained normal or improved, nearly normalizing, in two patients; one did not show improvement in creatinine but was receiving concomitant nephrotoxic drugs. On extended follow up, two patients remain stable and one experienced graft failure, which the investigator considers unrelated to OMS721 treatment.

No significant safety concerns have been observed. The most commonly reported adverse events in these patients have been abdominal pain, diarrhea, neutropenia and hypokalemia, all commonly seen in this patient population. An abstract has been submitted for presentation at the February 2017 Tandem Meeting of the American Society of Blood and Marrow Transplantation and the Center for International Blood and Marrow Transplant Research.

“These data are exciting,” stated Samer Khaled, M.D., Assistant Clinical Professor of Hematology and Hematopoietic Cell Transplantation at City Of Hope in Duarte, California, and OMS721 clinical investigator. “The response in our patient was impressive, particularly since the patient had failed previous treatments. Lectin pathway inhibition could play a role in other post-transplant complications, and I look forward to continued development of OMS721 in stem cell transplantation.”

Approximately 20,000 HSCT procedures are performed in the U.S. annually, and TMA is reported to occur in approximately 10 to 25 percent of HSCT patients. TMA most commonly affects the kidney but can also damage the lungs, gastrointestinal tract and central nervous system. Mortality in patients who develop severe HSCT-TMA is greater than 90 percent.

“In addition to the data being collected in aHUS patients, these HSCT-TMA results expand the potential benefits of OMS721 to multiple thrombotic microangiopathy indications,” stated Gregory A. Demopulos M.D., chairman and chief executive officer of Omeros. “Stem cell transplantation is an expanding field and represents an attractive medical and commercial opportunity. We plan to discuss with FDA and international regulatory agencies the design of a single Phase 3 trial for HSCT-TMA and look forward to OMS721 addressing the significant unmet needs of patients across a wide range of hematologic, renal and other therapeutic indications.”



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