2024–2025 Clinical & Translational Update — BTK Degraders, Fixed-Duration Combinations, Bispecific Antibodies, CAR-T & MRD-Guided Strategies
CLL remains the most common leukemia in adults in the Western world. The treatment landscape has been fundamentally transformed over the past decade — from chemoimmunotherapy to oral targeted agents — and is now entering a new era defined by fixed-duration combinations, next-generation kinase degraders, and immunotherapeutic strategies. The central challenge in 2025 is managing patients who become double-refractory to both BTK and BCL-2 inhibitors.
Ibrutinib · Acalabrutinib · Zanubrutinib · Pirtobrutinib (non-covalent)
Venetoclax ± Obinutuzumab · ± Acalabrutinib
Bexobrutideg (NX-5948) · BGB-16673 · NX-2127
Epcoritamab (CD3×CD20) · Combinations under study
Liso-cel (CD19) · 3rd-gen CAR-T · CAR-NK
Ibrutinib + Venetoclax · FLAIR / CLL17 trials
Heavily pretreated patients (median 4 prior lines) with BTK, BCL-2 and CAR-T exposure. No patient profile showed intrinsic resistance. Active irrespective of TP53, PLCG2, or BCL2 mutation status. No dose-limiting toxicities; no new-onset AF/flutter.
Fixed-duration all-oral doublet vs chemoimmunotherapy in treatment-naïve CLL (excl. del17p/TP53 mut). 35% reduction in risk of progression or death over chemoimmunotherapy. sNDA submitted to FDA July 2025. Most common Grade ≥3 AE: neutropenia (26.8%).
Five-year follow-up from ASH 2024 confirms sustained PFS benefit of zanubrutinib over bendamustine-rituximab. Tolerability and long-term safety profile reinforce zanubrutinib as preferred second-generation BTKi. Dose reduction to 160mg tablet approved in 2025, improving adherence in older patients.
Subcutaneous epcoritamab (CD3×CD20) in patients post ≥2 lines including cBTKi. Updated data at ICML 2025 confirmed durable clinical activity. Epcoritamab combinations with venetoclax and pirtobrutinib under active investigation as next-generation fixed-duration immunotherapy approaches.
Patients refractory to both BTKi and venetoclax (BCL-2i) represent the most urgent unmet need in CLL. Prognosis is very poor. No standard approach exists — these patients require enrolment in clinical trials evaluating BTK degraders, bispecifics, CAR-T, and novel combinations.
With multiple effective agents, the order of BTKi → BCL-2i vs BCL-2i → BTKi profoundly affects resistance profiles. Cross-resistance patterns differ and remain under active study. The ReVenG trial is exploring venetoclax retreatment after first-line venetoclax-based therapy.
Fixed-duration regimens offer cost savings, resistance avoidance, and treatment-free time — but continuous BTKi therapy may provide superior MRD suppression in unmutated IGHV. CLL17 will provide the first direct head-to-head comparison to resolve this debate.
Ibrutinib-related atrial fibrillation, hypertension, and bleeding complicate long-term use. Zanubrutinib and acalabrutinib offer improved selectivity. Dose-modification strategies and multidisciplinary cardiovascular co-management are essential in older, comorbid patients.
Sequential therapy drives genomic evolution — acquisition of BTK C481S, PLCG2, and BCL-2 G101V resistance mutations. Whole-genome sequencing and liquid biopsy (ctDNA) are increasingly used to track clonal dynamics and guide treatment switches early.
Long-term oral therapy in an elderly, comorbid population (median age 70) presents adherence challenges. Pill burden, drug interactions, and financial toxicity affect real-world outcomes. The zanubrutinib 160mg tablet approval addresses pill burden directly.
Fit patients without del(17p)/TP53 mut: Fixed-duration venetoclax + obinutuzumab (CLL14) or venetoclax + acalabrutinib (AMPLIFY, pending approval); alternatively continuous zanubrutinib or acalabrutinib monotherapy. Mutated IGHV may favor venetoclax-based fixed-duration; unmutated IGHV may favor continuous BTKi.
del(17p) / TP53 mutant CLL: Continuous BTKi (zanubrutinib or acalabrutinib) — standard of care. Venetoclax ± antibody is an option. Avoid chemoimmunotherapy. High-risk patients may be considered for clinical trials of upfront combination strategies.
Post-BTKi relapse: Venetoclax + rituximab or obinutuzumab (if BCL-2i naïve). Pirtobrutinib if cBTKi failure but BCL-2i naïve. Consider MRD-guided retreat strategies (ReVenG trial data emerging for venetoclax retreatment).
Post-venetoclax relapse: BTKi or pirtobrutinib (if BTKi naïve). Epcoritamab (bispecific antibody) is emerging as an option post-cBTKi; CAR-T cell therapy (liso-cel) now FDA approved in R/R CLL/SLL post-BTKi and BCL-2i.
Post-BTKi + Post-BCL-2i: Enrol in clinical trial as priority. Investigational options: BTK degraders (NX-5948, BGB-16673 Phase 1 data encouraging), bispecific antibodies, CAR-T + ibrutinib combinations, novel BCL-2 inhibitors. No established standard outside trials.
CLL treatment is at an inflection point. Fixed-duration oral doublets (BTKi + venetoclax) are rapidly becoming the new standard of care, offering deep remissions with treatment-free intervals. The next frontier is the double-refractory patient — where BTK degraders, bispecific antibodies, and next-generation CAR-T therapies offer genuine therapeutic hope for the first time.
The integration of MRD as a treatment endpoint — rather than a prognostic marker — marks a paradigm shift. Therapy will increasingly be individualised by IGHV status, cytogenetic risk, MRD kinetics, and comorbidity profile. The era of one-size-fits-all CLL management is ending.
Key trials to watch: CLL17, FLAIR extension, NX-5948-301 Phase 1b/2 expansion, BRUIN CLL-321, and ongoing bispecific combination studies at ASH 2025 and beyond.