Seattle Genetics announced the clinical hold placed on Phase I study of the drug – also known as SGN-CD33A – last night. The firm explained the US regulators' decision follows an independent review of data from the 300 patients treated so far. It also said it had agreed to make protocol changes.
Chief medical officer Jonathan Drachman said: “We will resume two phase 1 trials in AML and plan to initiate a randomized phase 2 trial during 2017 evaluating vadastuximab talirine in combination with standard of care chemotherapy in frontline, younger AML patients.
The US Food and Drug Administration (FDA) told Seattle Genetics to halt Phase I studies in December after the death of four patients enrolled in the programme who had exhibited signs of liver damage – hepatotoxicity.
Other programmes not covered by the clinical hold – specifically a Phase III study of SGN-CD33A in older patients with AML and a Phase I/II study examining the drug as a treatment for myelodysplastic syndrome – continue to enrol patients.
ADC candidate
Vadastuximab talirine is an antibody drug conjugate (ADC) that targets CD33 receptors on cancerous cells.
The drug combines a monoclonal antibody and a DNA binding agent called pyrrolobenzodiazepine (PBD), which are joined using Seattle’s site-specific conjugation technology, EC-mAb.
SGN-CD33A has orphan status in Europe and the US for the treatment of acute myeloid leukaemia (AML).