MB is only one part of the puzzle In the document below you'll see that efficacy is only one factor influencing the FDA decision. That is why those mentions in the PR like: "Clinical data demonstrates a positive benefit for patients in septic shock", " it did demonstrate beneficial treatment effects across multiple end points", "cardiovascular function improved and the use of vasopressors decreased", "The trial clearly showed that the Toraymyxin™ medical device is safe", "The overall data from our pivotal Phase III trial clearly demonstrates a clinically relevant impact on patient lives", become very important. I understand that even a device showing 0% MB over standard of care could be approved if it's safe and improves patient conditions.
https://www.fda.gov/medicaldevices/deviceregulationandguidance/guidancedocuments/ucm267829.htm