Of the 12 patients treated with ALT-803 subcutaneously, 11 patients had either stable disease, or partial or complete responses. All 11 patients remained on study and were in consolidation or follow-up and have not relapsed, Dr. Fehniger reported.
Among the five rituximab-refractory patients, the researchers observed one complete response, two patients with stable disease (45% and 36% tumor volume decrease), and two patients with partial disease. The durability of the responses can only be understood with longer follow-up, Dr. Fehniger said.
The peripheral blood of the patients was analyzed via flow cytometry and mass cytometry. Over the duration of four weekly doses, there was an increase in percentage (sixfold, P less than .001) and absolute number (10-fold, P less than .001) of natural killer cells at the 15-mcg/kg and 20-mcg/kg subcutaneous dose levels of ALT-803.
These results suggest that further studies of ALT-803 with other therapeutic targeting mAbs, or other immunotherapy modalities, are warranted, the researchers concluded.
Dr. Fehniger reported research funding from Altor BioScience.
SOURCE: Fehniger TA et al. AACR Annual Meeting, .