GDC-0853 preserves NK cell–mediated ADCC in response to anti-CD20 antibodies. NK cells treated with 1 µM BTK inhibitor were cocultured with CLL cells loaded with radioactive chromium in the presence of alemtuzumab, rituximab, ofatumumab, or obinutuzumab at a concentration of 10 µg/mL. Supernatant fluids were collected after 4 hours and measured for radioactivity to determine the efficacy of CLL cell lysis by NK cell–mediated ADCC (N = 4). **P ≤ .01; ***P ≤ .001.