To investigate if PARP activity was related to HRR status and hence sensitivity to talazoparib, 3 further CLL samples (193, 199 and 208) with high, medium or low PARP activity and low or high endogenous PAR levels (Table 1) were stimulated to proliferate on a CD40L-expressing layer, and exposed to talazoparib (0 nM - 1,000 nM) after a 72 hr talazoparib pre-exposure period (method 2). Here, PARP1 is linked to B-cell chronic lymphocytic leukemia.