Seattle Genetics, Inc. has received notice from the U.S. Food and Drug Administration (FDA) that a clinical hold or partial clinical hold has been placed on several early stage trials of vadastuximab talirine (SGN-CD33A) in acute myeloid leukemia (AML). The clinical holds were initiated to evaluate the potential risk of hepatotoxicity in patients who were treated with SGN-CD33A and received allogeneic stem cell transplant either before or after treatment. Six patients have been identified with hepatotoxicity, including several cases of veno-occlusive disease, with four fatal events. Overall, more than 300 patients have been treated with SGN-CD33A in clinical trials across multiple treatment settings. Seattle Genetics is working diligently with the FDA to determine whether there is any association between hepatotoxicity and treatment with SGN-CD33A, to promptly identify appropriate protocol amendments for patient safety and to enable continuation of these trials.
The phase 1/2 trial of SGN-CD33A monotherapy in pre- and post-allogeneic transplant AML patients has been placed on full clinical hold. Two phase 1 trials have been placed on partial clinical hold (no new enrollment, existing patients may continue treatment with re-consent). These studies are SGN-CD33A monotherapy, including a subset of older AML patients in combination with hypomethylating agents, and SGN-CD33A combination treatment with 7+3 chemotherapy in newly diagnosed younger AML patients. No new studies will be initiated until the clinical holds are lifted.
Seattle Genetics’ other ongoing trials of SGN-CD33A, including the phase 3 CASCADE trial in older AML patients and phase 1/2 trial in myelodysplastic syndrome, are proceeding with enrollment.