Shares of Catalyst Biosciences $CBIO were badly damaged in the wake of an alert that two patients in one cohort of their early-stage hemophilia drug study developed a neutralizing antibody after a course of therapy with their Factor IX (FIX) candidate CB 2679d/ISU304.
Investigators have now suspended treatment in cohort 6 and will stay on hold until they figure out what went wrong. The two patients were able to resume treatment with their prescribed IV FIX prophylaxis therapies.
On the bright side, the South San Francisco-based company also gave a thumbs up to the efficacy they’ve been seeing. On the down side, the stock was hit hard on the safety alarm. Shares plunged 64% on the notice in pre-market trading Monday.
“The most recent data from the ongoing Phase 1/2 trial have demonstrated clinical proof of concept for subcutaneous dosing of a potent FIX as a treatment for hemophilia B. Patients in Cohort 6 of the trial were able to maintain Factor IX levels over 30% which is at the upper end of mild hemophilia and higher than currently approved extended half-life (EHL) intravenous Factor IXs,” said Nassim Usman, chief executive officer of Catalyst, in a statement. “Our next steps will be to carefully identify the cause and nature of the antibodies and provide further updates once we have the results of our analysis.”
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