BTK and B-cell chronic lymphocytic leukemia: In late-stage CLL (R/R disease or patients with adverse genetics), continuous BTK inhibition or finite venetoclax-based regimens can achieve durable control; choice is individualized by mutation profile, comorbidities (especially cardiac disease and bleeding risk with BTK inhibitors), and polypharmacy (drug–drug interactions via Cytochrome P450 [CYP] pathways).