Antibodies neutralize Catalyst's Factor IX variant, crater stock

Catalyst Biosciences Inc. (NASDAQ:CBIO) fell $16.14 (64%) to $9.11 Monday when it reported that two patients developed neutralizing antibodies to CB 2679d (ISU 304). The antibodies were observed after treatment in the sixth and latest dose cohort of a Phase I/II trial evaluating the next-generation Factor IX variant to treat severe hemophilia B.

The cohort was the first of the trial to treat patients with a loading dose of CB 2679d, President and CEO Nassim Usman said on a conference call Monday. The two patients received a loading dose of 75 IU/kg IV CB 2679d 30 minutes prior to the first of nine daily subcutaneous 150 IU/kg CB 2679d doses. The company had not detected CB 2679d neutralizing antibodies in the previous five cohorts. ...