BTK degradation by NRX-0492 in CLL cells is sustained and equally achieved in high and standard-risk disease. (A) Immunoblots of CLL PBMCs that were treated with 0.5 nM hook or 0.5 nM NRX-0492 for 4 hours and then cultured for the indicated times after drug washout, with (B) quantification of BTK relative to loading control (GAPDH) over time. (C, D) Mean (± SEM) BTK levels in CLL PBMCs 48 hours after drug washout of vehicle (DMSO) or NRX-0492 with samples divided by (C) IGHV status into mutated CLL and unmutated CLL or (D) cytogenetic risk group, del13q (low risk), del17p (high risk). Comparisons over time by paired t test, comparisons between treatment subgroups by unpaired t test; ns, not significant. (E) Representative immunoblot showing BTK in CLL PBMCs treated as indicated: lane 1 DMSO only; lanes 2 to 4, cells were treated with DMSO, MLN4924, or harness for 1 hour followed by 2 nM NRX-0492 treatment for 4 hours. Lanes 5 to 8, cells were treated with NRX-0492 for 4 hours followed by drug washout (WO). 24 hours post washout, DMSO, MLN4924, or harness were added for an additional 24 hours. (F) Summary of experiments using cells from 3 different patients, statistics by paired t test.