Tetherex Pharmaceuticals Inc., a rare Oklahoma City-based biotech, raised $50 million in a private placement of series B stock led by MPM Capital. The funds will support a phase II trial of the company's lead candidate, SEL-K2, for the potential treatment of venous thromboembolism (VTE) in patients undergoing total knee replacement surgery and a second midstage study in Crohn's disease, another inflammatory indication, or cancer. The financing follows an initial raise of about $4.4 million in convertible debt in 2014.