Deep and durable remissions were produced by the combination of SGN-CD33A and hypomethylating agents (HMAs) among patients with acute myeloid leukemia (AML). These findings were presented at the European Hematology Association 21st Congress.1
AML is an aggressive blood cancer with a 5-year survival rate of only 26%. Most cases of AML express CD33 on the surface of the leukemia cells.
Although AML is diagnosed at an average age of 67 years, it is challenging to treat because older patients do not tolerate intensive chemotherapy well. Furthermore, only modest response rates come from treatment with standard therapies such as the hypomethylating agents azacitidine and decitabine.
This presentation shared data from an ongoing phase 1 trial evaluating vadastuximab talirine (SGN-CD33A; 33A) in combination with standard therapies (azacitidine, decitabine) in older patients with AML who have declined intensive frontline therapy. 33A is an antibody-drug conjugate (ADC) targeted to CD33. It is comprised of a novel antibody system stably linked to a highly potent cell-killing agent. CD33 is expressed on leukemic blasts in nearly all patients with AML and expression is generally consistent regardless of age, risk factors, or disease characteristics.
A total of 53 patients with AML (median age, 75 years) who were treated with this combination were included in the analysis. Efficacy could be evaluated in 49 of the patients; the composite complete remission rate (CR+CRi) was 73%. This rate compares favorably with historical studies of HMA monotherapy in this population.
Mortality rates were 2% at 30 days and 8% at 60 days. The most common grade 3 or higher treatment-emergent adverse events were febrile neutropenia, thrombocytopenia, anemia, and neutropenia.
The combination of 33A and HMAs was well-tolerated and yielded encouraging response rates in older patients with AML.
1. Fathi A, Erba H, Lancet J, et al. SGN-CD33A in combination with hypomethylating agents: a novel, well-tolerated regimen with high remission rate in older patients with AML. Presentation at: European Hematology Association 21st Congress; June 9-12, 2016; Copenhagen, Denmark. Abstract S503.