CD33 Expression and Its Association with Gemtuzumab Ozogamycin Response: Results from AAML0531

Pollard, JA, (2016) Journal of Clinical Oncology (Link to abstract)

Gemtuzumab ozogamycin (Mylotarg) is a humanized antibody against CD33 with efficacy in acute myeloid leukemia at the expense of marked associated toxicity. This is a secondary analysis of the AAML0531 data which randomized children to standard therapy with or without gemtuzumab in induction and in consolidation. This study assessed whether CD33 expression in AML cells was associated with outcome in those who received gemtuzumab. Indeed, those with the highest expression had the lowest relapse with gemtuzumab and a better EFS with this drug whereas EFS was the same in those who got the drug but had low CD33 expression compared to those who didn’t get the drug.

* Gemtuzumab has a very important toxicity profile; targeting patients who will get the most benefit should therefore be the goal. This study indicates that CD33 expression level should probably be measured before allocating children to this treatment.