Head-to-head trials of BTK inhibitors have reported similar rates of anemia, thrombocytopenia, and neutropenia, with the exception of the ASPEN study, which reported a significantly higher rate of grade ≥3 neutropenia in the zanubrutinib versus ibrutinib arm (23.8% vs. 10.2%), although this did not translate into an increased risk of infection [30]. Here, BTK is linked to neutropenia.