Omeros says four deaths occur during Phase 2 study of OMS721
Omeros Corporation announced new results from the company's ongoing Phase 2 study of OMS721 evaluating patients with hematopoietic stem cell transplant-associated thrombotic microangiopathy. The data demonstrate an increase in median overall survival in HCT-TMA patients treated with OMS721 compared to a matched historical control. Historical control data are typically used for comparison when it is impractical or unethical to include a placebo arm in a clinical trial. In addition to and consistent with the survival data reported today, updated assessments of platelet count, lactate dehydrogenase and haptoglobin - all markers of TMA activity - continue to demonstrate clinically meaningful and statistically significant improvements in the HCT-TMA patients treated with OMS721. A total of 19 HCT-TMA patients have been treated to date with OMS721, 18 in the ongoing study and one patient under a compassionate use protocol. An historical control that best matched the OMS721-treated population was identified from the literature. The literature reference selection criteria were those studies that specified: individual patient data, adult and/or adolescent populations, allogeneic stem cell transplant recipients only, and no or partial response to immunosuppressive regimen modification. Overall median survival demonstrated greater than 16-fold improvement in survival in the OMS721-treated group. Markers of TMA activity in study participants, specifically mean platelet count, mean LDH, and mean haptoglobin, continue to demonstrate statistically and clinically significant improvements following OMS721 treatment. At the end of protocol-allowed treatment, the mean platelet count increased from 18,100 x 106/mL at baseline to 52,300 x 106/mL. The mean LDH decreased from 591 U/L at baseline to 250 U/L. The mean haptoglobin increased from 8 mg/dL at baseline to 141 mg/dL. Mean creatinine remained stable at approximately 120 mumol/L but a majority of patients had co-existing conditions for which they were receiving nephrotoxic medications. Other serious co-existing conditions included graft versus host disease, cytomegalovirus and human herpes virus 6 infections, prior sepsis, diffuse alveolar hemorrhage, and residual underlying malignancies. OMS721 has been well tolerated and no safety concerns have been identified. The most commonly reported adverse events were diarrhea and neutropenia. Four deaths occurred during the study: one due to progression of acute myeloid leukemia, two due to neutropenic sepsis, and one due to acute renal and respiratory failure. Only one of these deaths - the acute renal and respiratory failure - was considered "possibly drug-related" because an association could not be definitively ruled out by the investigator. These are common complications of HCT. The other three deaths were deemed not to be related to OMS721.