CLL treatment shifts toward fixed-duration and MRD-guided targeted regimens

Chronic lymphocytic leukemia (CLL), the most common leukemia in Western countries, is undergoing a therapeutic transformation that is rewriting how doctors decide who to treat, when to treat, and for how long. A new comprehensive review published in Blood Research synthesizes the latest clinical trial evidence and international guidelines, describing a field that has moved decisively away from traditional chemoimmunotherapy toward targeted agents that modulate B-cell receptor signaling and apoptosis regulation. The review, authored by Jongheon Jung, frames CLL management as a precision-medicine paradigm in which genetic risk factors, particularly TP53 and IGHV mutation status, now serve as the key determinants of frontline treatment selection.

The biological foundation of this shift lies in the disease itself. CLL arises through a multistep process initiated by lymphoid priming of hematopoietic stem cells, followed by clonal expansion of B-cell progenitors and the acquisition of genetic and chromosomal abnormalities that drive clinically overt disease. Cytogenetic alterations have long served as prognostic markers: del(13q) as the sole abnormality is the most frequent alteration and carries the most favorable outcomes, while del(17p) marks aggressive disease and poor prognosis. Diagnosis requires at least 5 × 10⁹/L clonal CD5-positive, CD19-positive, CD23-positive B cells in the peripheral blood, typically with low CD20 expression and weak surface immunoglobulin, and peripheral blood flow cytometry is sufficient in most cases.

Risk stratification has likewise evolved beyond the traditional Rai and Binet clinical staging systems toward integrated models such as the CLL International Prognostic Index, which combines TP53 status, IGHV mutation status, serum β2-microglobulin levels, clinical stage, and patient age into a composite score. The index assigns substantial weight to the biological factors, but the review notes that its prognostic utility may be reduced in the current era of targeted agents, because Bruton tyrosine kinase (BTK) and B-cell lymphoma 2 (BCL2) inhibitors can improve outcomes even in patients with high-risk genetic features. For asymptomatic early-stage patients, watch-and-wait remains the standard of care, supported by serial monitoring every three to six months and treatment initiation only when International Workshop on CLL criteria are met, including progressive marrow failure, symptomatic lymphadenopathy or splenomegaly, constitutional symptoms, or autoimmune cytopenias.

The most striking evidence against routine early intervention comes from the phase 3 CLL12 trial, which compared ibrutinib with placebo in asymptomatic, treatment-naïve patients at high risk of progression. At a median follow-up of 69.3 months, ibrutinib significantly prolonged event-free survival and delayed progression to symptomatic disease compared with placebo, with a hazard ratio of 0.276 and p less than 0.001. Yet these benefits did not translate into an overall survival advantage: five-year overall survival was 93.3 percent versus 93.6 percent, estimated ten-year overall survival was 89.8 percent versus 86.5 percent, and the difference was not statistically significant. The ibrutinib group also had substantially higher rates of cardiovascular adverse events, including cardiac arrhythmias and hypertension, even though overall incidences of adverse and serious adverse events were similar between groups.

Ongoing trials are now testing whether that conclusion might eventually change for carefully selected subgroups. The phase 3 SWOG-EVOLVE study is evaluating whether early intervention with a fixed-duration combination of venetoclax plus obinutuzumab improves overall survival compared with deferred treatment upon progression in newly diagnosed, high- or very-high-risk asymptomatic patients stratified by the CLL-IPI. Meanwhile, the phase 2/3 PreVent-ACaLL trial uses a machine learning-based infection model to identify asymptomatic patients at high risk of infection or rapid progression and is testing whether a twelve-week preemptive course of acalabrutinib and venetoclax can restore immune competence and prolong infection-free survival without long-term toxicity. The results of these studies will be critical in determining whether risk-adapted finite-duration early interventions can challenge the watch-and-wait paradigm in well-defined high-risk subgroups.

In the frontline setting, the treatment landscape has transitioned from chemoimmunotherapy to highly effective targeted strategies, and the review documents a clear preference shift. Second-generation covalent BTK inhibitors such as acalabrutinib and zanubrutinib are now preferred over ibrutinib based on pivotal head-to-head randomized trials. In the ELEVATE-RR trial, acalabrutinib demonstrated non-inferior progression-free survival compared with ibrutinib, with significantly lower incidence of atrial fibrillation or flutter at 9.4 percent versus 16.0 percent and hypertension at 9.4 percent versus 23.2 percent. The ALPINE trial established the superiority of zanubrutinib over ibrutinib, showing significantly prolonged progression-free survival with a hazard ratio of 0.68, an advantage particularly pronounced in patients with del(17p) and/or TP53 mutations at a hazard ratio of 0.51, along with a markedly lower rate of atrial fibrillation or flutter at 7.1 percent versus 17.0 percent and no cardiac deaths compared with six in the ibrutinib arm.

Continuous BTK inhibitor therapy has demonstrated high efficacy across trials. In the SEQUOIA arm C, zanubrutinib effectively overcame the poor prognosis typically associated with TP53 aberrations, achieving a 60-month progression-free survival of 72.2 percent in del(17p) patients and 70.7 percent in IGHV-unmutated patients. The RESONATE-2 trial showed that continuous ibrutinib overcame the adverse prognostic impact of unmutated IGHV, and long-term follow-up in patients aged 65 and older without del(17p) confirmed a favorable safety profile, with adverse events generally manageable and no evidence of significant cumulative toxicity over time. Nevertheless, the clinical paradigm is increasingly shifting toward time-limited fixed-duration regimens that offer the potential for treatment-free intervals.

The pivotal foundation for that shift is the CLL14 trial, which validated a one-year fixed-duration combination of venetoclax and obinutuzumab. Six-year follow-up showed a median progression-free survival of 76 months, significantly outperforming obinutuzumab plus chlorambucil chemoimmunotherapy, with an undetectable measurable residual disease rate of 76 percent at the end of treatment. The CLL17 trial extended this by comparing fixed-duration regimens, venetoclax–obinutuzumab or venetoclax–ibrutinib, with continuous ibrutinib monotherapy in patients with unmutated IGHV. The fixed-duration arms achieved substantially higher bone marrow undetectable MRD rates at 62.0 percent and 40.0 percent versus 0 percent, and higher complete response rates at 51.5 percent and 46.2 percent versus 8.3 percent, while demonstrating non-inferior three-year progression-free survival of 75.8 percent and 78.9 percent versus 79.7 percent. However, with a median follow-up of only 34.2 months in this interim analysis, the review cautions that longer follow-up is necessary to confirm whether comparable disease control is maintained, particularly in high-risk genomic subgroups where progression-free survival may decline as data mature.

The all-oral venetoclax–ibrutinib approach was reinforced by the CAPTIVATE fixed-duration cohort, which achieved undetectable MRD rates of 77 percent in peripheral blood and 60 percent in bone marrow with two-year progression-free survival of 95 percent in young, fit patients, and by the GLOW trial in older or comorbid populations. The phase III AMPLIFY trial then demonstrated the efficacy of a fixed-duration acalabrutinib–venetoclax backbone in treatment-naïve patients without del(17p), showing that adding obinutuzumab increased end-of-treatment undetectable MRD rates from 45 percent to 95 percent and mitigated the adverse prognostic impact of unmutated IGHV. That intensification carried a safety tradeoff, with grade 3 or higher infections at 23.6 percent versus 12.4 percent and coronavirus disease-related deaths at 5.3 percent versus 2.7 percent compared with the doublet, mirroring the CLL13 trial, in which the venetoclax–obinutuzumab–ibrutinib triplet showed higher rates of severe infections than doublet or chemoimmunotherapy regimens. The acalabrutinib lead-in strategy successfully mitigated the clinical risk of tumor lysis syndrome.

Measurable residual disease (MRD)-guided strategies represent the next frontier, using response depth to determine treatment duration. The FLAIR trial employed an MRD-guided strategy with ibrutinib and venetoclax, achieving a five-year progression-free survival of 94 percent and overall survival of 96 percent, significantly outperforming continuous ibrutinib and chemoimmunotherapy, with benefits extending to patients with unmutated IGHV. The GAIA/CLL13 trial showed estimated four-year progression-free survival of 85.5 percent for an MRD-guided triplet and 81.8 percent for the venetoclax–obinutuzumab doublet, versus 62.0 percent for chemoimmunotherapy and 70.1 percent for venetoclax–rituximab, though the triplet carried higher exposure-adjusted incidence of severe infections and cardiovascular toxicities. For high-risk patients with TP53 aberrations, a phase II trial of an MRD-tailored acalabrutinib–venetoclax–obinutuzumab triplet achieved bone marrow undetectable MRD of 71 percent at cycle 16 with four-year progression-free and overall survival of 70 percent and 88 percent in the TP53-aberrant subset, while the CLL2-GIVe trial reported 36-month progression-free survival of 79.9 percent and overall survival of 92.6 percent using a fixed-duration triplet exclusively in untreated del(17p) or TP53-mutated patients.

In the relapsed or refractory setting, molecular assessment at relapse is critical because acquired resistance to covalent BTK inhibitors is often mediated by mutations in BTK, such as C481S, and PLCG2, the most common drivers of secondary resistance. European guidelines adopt a 36-month cut-off to distinguish early from late relapse after venetoclax-based time-limited therapy, influencing whether to rechallenge or switch class. Final MURANO analysis showed venetoclax-based retreatment was impressively effective in patients with durable remission after prior fixed-duration treatment, and CAPTIVATE analysis found no resistance mutations in patients who relapsed after first-line ibrutinib plus venetoclax, with retreatment achieving two-year progression-free survival of 91 percent and overall survival of 100 percent in those progressing more than two years after completing initial therapy. The BRUIN CLL-321 trial established pirtobrutinib, a non-covalent BTK inhibitor, for patients who progressed on covalent BTK inhibitors, though resistance can develop via BTK T474x or L528W mutations. The randomized phase 3 BRUIN CLL-322 trial then showed that a fixed-duration triplet of pirtobrutinib, venetoclax, and rituximab significantly improved progression-free survival over venetoclax–rituximab, with a hazard ratio of 0.547 and 24-month rates of 86.9 percent versus 71.8 percent, sustained across high-risk genomic subsets including TP53 aberrations and complex karyotypes.

Beyond inhibitors, the review highlights emerging modalities designed to overcome resistance. Proteolysis-targeting chimeric BTK degraders can circumvent both enzymatic and scaffolding resistance mutations. Tacabrutideg demonstrated high clinical activity and tolerability in the phase 1/2 CaDAnCe-101 trial and is being evaluated head-to-head against pirtobrutinib in the randomized phase 3 CaDAnCe-304 trial for covalent BTK inhibitor-pretreated patients. Bexobrutideg has shown rapid and durable BTK degradation across phase 1 trials and is under investigation in the pivotal phase 2 DAYBreak CLL-201 study for patients previously treated with covalent BTK inhibitors, non-covalent BTK inhibitors, and BCL2 inhibitors. Cellular immunotherapy remains a vital salvage strategy: lisocabtagene maraleucel achieved an objective response rate of 43 percent and a complete response rate of 18 percent in heavily pretreated patients in the TRANSCEND-CLL-004 study, with emerging data suggesting that concurrent or periprocedural BTK inhibitor use may enhance CAR-T efficacy by improving T-cell fitness and anti-CLL immunity. The review also addresses Richter transformation, the aggressive evolution of CLL into high-grade lymphoma, emphasizing that clonality assessment is essential because clonally unrelated cases, roughly 20 percent of the total, may be managed as de novo diffuse large B-cell lymphoma and may have better outcomes than clonally related disease, which typically requires intensive chemoimmunotherapy or allogeneic stem cell transplantation. The reported high prevalence of TP53 disruption in both clonally related and unrelated transformation underscores, the author argues, an urgent need for collaborative clinical trials integrating novel therapies such as bispecific antibodies and advanced cellular immunotherapies to improve long-term outcomes in this population.

Subject of Research: Recent advances and emerging therapeutic strategies in chronic lymphocytic leukemia

Article Title: Chronic lymphocytic leukemia: recent advances and emerging therapeutic strategies

Article References: Jung, J. (2026). Chronic lymphocytic leukemia: recent advances and emerging therapeutic strategies. Blood Research, 61(1), Article 70. https://doi.org/10.1007/s44313-026-00183-w

Image Credits: AI Generated

DOI: 10.1007/s44313-026-00183-w

Keywords: chronic lymphocytic leukemia, BTK inhibitors, venetoclax, MRD-guided therapy, fixed-duration regimens, TP53 aberrations, Richter transformation, CAR-T therapy, BTK degraders, relapsed refractory CLL, CLL14 trial, precision medicine