Improved Innate Immune Function in Patients with Chronic Lymphocytic Leukemia Treated with Targeted Therapy in Clinical Trials.

PURPOSE: CLL patients have increased risk of severe infections. While adaptive immune dysfunction is well-described, clinical tools for identifying patients at risk are lacking, warranting investigation of additional immune components. In contrast to chemotherapy, targeted agents could spare or even improve innate immune function. Therefore, we investigated innate immune phenotypes and function in CLL patients before and during targeted treatment. EXPERIMENTAL DESIGN: Baseline and consecutive blood samples were collected from CLL patients treated with acalabrutinib (n=17) or ibrutinib+venetoclax (n=18) in clinical trials. Innate immune function was assessed by TruCulture, a whole-blood ligand-stimulation assay quantifying cytokine release in response to standardized stimuli. Innate immune phenotypes were characterized by flow cytometry. As a proxy for infections, we mapped antimicrobial use before and during treatment. RESULTS: At baseline, CLL patients displayed impaired stimulated cytokine responses to the endotoxin lipopolysaccharide (LPS) along with deactivated monocytes, enrichment of myeloid derived suppressor cells and metamyelocytes, and elevated (unstimulated) proinflammatory cytokines. Two/three cycles of acalabrutinib or ibrutinib normalized LPS-stimulated responses, in parallel with decreased duration of infections. Innate immune profiles and elevated proinflammatory cytokines further normalized during longer-term acalabrutinib or ibrutinib+venetoclax, paralleled by decreased infection frequency. CONCLUSIONS: Innate immune impairment and infection susceptibility in CLL patients were restored in parallel during targeted therapy. Thus, targeted treatment may reduce the risk of infections in CLL, as currently under investigation in the PreVent-ACaLL phase 2 trial of acalabrutinib+venetoclax for high risk CLL (NCT03868722).

Identifying CLL patients at high risk of atrial fibrillation on treatment using machine learning.

An increased risk of developing atrial fibrillation (AF) has been observed in patients with chronic lymphocytic leukemia (CLL) who were treated with ibrutinib and other BTK inhibitors. Previous studies have explored the prevalence of AF in CLL and the risk of developing AF at time of diagnosis. However, the interaction between treatment type with other risk factors on risk of developing atrial fibrillation at the time of treatment initiation has not been investigated. This becomes particularly crucial in CLL, as there is often a substantial time gap between diagnosis and treatment, unlike many other cancers. We propose a treatment-aware approach using predictive modeling to identify the risk factors associated with AF at time of treatment initiation. Moreover, the model provides treatment-dependent risk factors by including the interaction between the treatment types and other risk factors. The results demonstrated that the treatment-aware modeling including interactions outperformed currentrisk scores.

Fixed-duration ibrutinib-venetoclax versus chlorambucil-obinutuzumab in previously untreated chronic lymphocytic leukaemia (GLOW): 4-year follow-up from a multicentre, open-label, randomised, phase 3 trial.

BACKGROUND: In the GLOW study, fixed-duration ibrutinib-venetoclax showed superior progression-free survival versus chlorambucil-obinutuzumab in patients with previously untreated chronic lymphocytic leukaemia who were older or had comorbidities, or both, at a median follow up of 27·7 months. In this Article, we report updated outcomes from GLOW after a 46-month median follow-up. METHODS: GLOW was a randomised, multicentre, phase 3 study done at 67 hospital centres across 14 countries. Patients aged 65 years and older or 18-64 years with previously untreated chronic lymphocytic leukaemia and a cumulative illness rating scale score of more than 6 or creatinine clearance less than 70 mL/min, or both, and an Eastern Cooperative Oncology Group performance status of 2 or less were randomly assigned (1:1) via an interactive web system with permuted blocks (block size of four) and stratified by IGHV mutational status and the presence of del11q aberration to the ibrutinib-venetoclax group (three cycles of ibrutinib lead-in [420 mg/day, orally], followed by 12 cycles of ibrutinib plus venetoclax [400 mg/day, orally, including a 5-week dose ramp-up]) or the chlorambucil-obinutuzumab group (six cycles of chlorambucil [0·5 mg/kg, orally, on days 1 and 15 of each cycle], and obinutuzumab [1000 mg, intravenously, on days 1 (or 100 mg on day 1 and 900 mg on day 2), 8, and 15 of cycle 1 and day 1 of cycles 2-6]). The primary endpoint was progression-free survival in the intention-to-treat population, assessed by an independent review committee. The safety population included all randomised patients who received at least one dose of the study treatment. This study is registered with ClinicalTrials.gov (NCT03462719) and the EU Clinical Trials Register (EudraCT 2017-004699-77). FINDINGS: Between May 4, 2018, and April 5, 2019, 211 patients (122 [58%] were male and 89 [42%] were female) were randomly assigned to receive ibrutinib-venetoclax (n=106) or chlorambucil-obinutuzumab (n=105). At a median of 46 months (IQR 43-47) of follow-up, progression-free survival remained superior for the ibrutinib-venetoclax group (hazard ratio 0·214 [95% CI 0·138-0·334]; p<0·0001); 42-month progression-free survival rates were 74·6% (95% CI 65·0-82·0) for ibrutinib-venetoclax and 24·8% (16·5-34·1) for chlorambucil-obinutuzumab. Following the primary analysis, one patient in the chlorambucil-obinutuzumab group had a serious adverse event of myelodysplastic syndrome. Treatment-related deaths were reported in one patient receiving ibrutinib-venetoclax (cardiac failure, pneumonia, and sinus node dysfunction) and in one patient receiving chlorambucil-obinutuzumab (pneumonia). There were 15 deaths in the ibrutinib-venetoclax group (of which three were due to post-treatment infections) and 30 deaths in the chlorambucil-obinutuzumab group (of which 10 were due to post-treatment infections). INTERPRETATION: After 4 years of follow-up, ibrutinib-venetoclax continues to significantly prolong progression-free survival (vs chemoimmunotherapy) in patients with previously untreated chronic lymphocytic leukaemia, supporting its use as a first-line option. FUNDING: Janssen Research & Development and Pharmacyclics.

Impact of Minimal Residual Disease on Progression-Free Survival Outcomes After Fixed-Duration Ibrutinib-Venetoclax Versus Chlorambucil-Obinutuzumab in the GLOW Study.

PURPOSE: In GLOW, fixed-duration ibrutinib + venetoclax showed superior progression-free survival (PFS) versus chlorambucil + obinutuzumab in older/comorbid patients with previously untreated chronic lymphocytic leukemia (CLL). The current analysis describes minimal residual disease (MRD) kinetics and any potential predictive value for PFS, as it has not yet been evaluated for ibrutinib + venetoclax treatment. METHODS: Undetectable MRD (uMRD) was assessed by next-generation sequencing at <1 CLL cell per 10,000 (<10-4) and <1 CLL cell per 100,000 (<10-5) leukocytes. PFS was analyzed by MRD status at 3 months after treatment (EOT+3). RESULTS: Ibrutinib + venetoclax achieved deeper uMRD (<10-5) rates in bone marrow (BM) and peripheral blood (PB), respectively, in 40.6% and 43.4% of patients at EOT+3 versus 7.6% and 18.1% of patients receiving chlorambucil + obinutuzumab. Of these patients, uMRD (<10-5) in PB was sustained during the first year post-treatment (EOT+12) in 80.4% of patients receiving ibrutinib + venetoclax and 26.3% receiving chlorambucil + obinutuzumab. Patients with detectable MRD (dMRD; ≥10-4) in PB at EOT+3 were more likely to sustain MRD levels through EOT+12 with ibrutinib + venetoclax versus chlorambucil + obinutuzumab. PFS rates at EOT+12 were high among patients treated with ibrutinib + venetoclax regardless of MRD status at EOT+3: 96.3% and 93.3% in patients with uMRD (<10-4) and dMRD (≥10-4) in BM, respectively, versus 83.3% and 58.7% for patients receiving chlorambucil + obinutuzumab. PFS rates at EOT+12 also remained high in patients with unmutated immunoglobulin heavy-chain variable region (IGHV) receiving ibrutinib + venetoclax, independent of MRD status in BM. CONCLUSION: Molecular and clinical relapses were less frequent during the first year post-treatment with ibrutinib + venetoclax versus chlorambucil + obinutuzumab regardless of MRD status at EOT+3 and IGHV status. Even for patients not achieving uMRD (<10-4), PFS rates remained high with ibrutinib + venetoclax; this is a novel finding and requires additional follow-up to confirm its persistence over time.

Final analysis of the CLL2-GIVe trial: obinutuzumab, ibrutinib, and venetoclax for untreated CLL with del(17p)/TP53mut.

The final analysis of the open-label, multicenter phase 2 CLL2-GIVe trial shows response and tolerability of the triple combination of obinutuzumab, ibrutinib, and venetoclax (GIVe regimen) in 41 previously untreated patients with high-risk chronic lymphocytic leukemia (CLL) with del(17p) and/or TP53 mutation. Induction consisted of 6 cycles of GIVe; venetoclax and ibrutinib were continued up to cycle 12 as consolidation. Ibrutinib was given until cycle 15 or up to cycle 36 in patients not achieving a complete response and with detectable minimal residual disease. The primary end point was the complete remission rate at cycle 15, which was achieved at 58.5% (95% CI, 42.1-73.7; P < .001). The last patient reached the end of the study in January 2022. After a median observation time of 38.4 months (range, 3.7-44.9), the 36-month progression-free survival was 79.9%, and the 36-month overall survival was 92.6%. Only 6 patients continued ibrutinib maintenance. Adverse events of concern were neutropenia (48.8%, grade ≥3) and infections (19.5%, grade ≥3). Cardiovascular toxicity grade 3 occurred as atrial fibrillation at a rate of 2.4% between cycles 1 and 12, as well as hypertension (4.9%) between cycles 1 and 6. The incidence of adverse events of any grade and grade ≥3 was highest during induction and decreased over time. Progressive disease was observed in 7 patients between cycles 27 and 42. In conclusion, the CLL2-GIVe regimen is a promising fixed-duration, first-line treatment for patients with high-risk CLL with a manageable safety profile.

First-Line Venetoclax Combinations in Chronic Lymphocytic Leukemia.

BACKGROUND: Randomized trials of venetoclax plus anti-CD20 antibodies as first-line treatment in fit patients (i.e., those with a low burden of coexisting conditions) with advanced chronic lymphocytic leukemia (CLL) have been lacking. METHODS: In a phase 3, open-label trial, we randomly assigned, in a 1:1:1:1 ratio, fit patients with CLL who did not have TP53 aberrations to receive six cycles of chemoimmunotherapy (fludarabine-cyclophosphamide-rituximab or bendamustine-rituximab) or 12 cycles of venetoclax-rituximab, venetoclax-obinutuzumab, or venetoclax-obinutuzumab-ibrutinib. Ibrutinib was discontinued after two consecutive measurements of undetectable minimal residual disease or could be extended. The primary end points were undetectable minimal residual disease (sensitivity, <10-4 [i.e., <1 CLL cell in 10,000 leukocytes]) as assessed by flow cytometry in peripheral blood at month 15 and progression-free survival. RESULTS: A total of 926 patients were assigned to one of the four treatment regimens (229 to chemoimmunotherapy, 237 to venetoclax-rituximab, 229 to venetoclax-obinutuzumab, and 231 to venetoclax-obinutuzumab-ibrutinib). At month 15, the percentage of patients with undetectable minimal residual disease was significantly higher in the venetoclax-obinutuzumab group (86.5%; 97.5% confidence interval [CI], 80.6 to 91.1) and the venetoclax-obinutuzumab-ibrutinib group (92.2%; 97.5% CI, 87.3 to 95.7) than in the chemoimmunotherapy group (52.0%; 97.5% CI, 44.4 to 59.5; P<0.001 for both comparisons), but it was not significantly higher in the venetoclax-rituximab group (57.0%; 97.5% CI, 49.5 to 64.2; P = 0.32). Three-year progression-free survival was 90.5% in the venetoclax-obinutuzumab-ibrutinib group and 75.5% in the chemoimmunotherapy group (hazard ratio for disease progression or death, 0.32; 97.5% CI, 0.19 to 0.54; P<0.001). Progression-free survival at 3 years was also higher with venetoclax-obinutuzumab (87.7%; hazard ratio for disease progression or death, 0.42; 97.5% CI, 0.26 to 0.68; P<0.001), but not with venetoclax-rituximab (80.8%; hazard ratio, 0.79; 97.5% CI, 0.53 to 1.18; P = 0.18). Grade 3 and grade 4 infections were more common with chemoimmunotherapy (18.5%) and venetoclax-obinutuzumab-ibrutinib (21.2%) than with venetoclax-rituximab (10.5%) or venetoclax-obinutuzumab (13.2%). CONCLUSIONS: Venetoclax-obinutuzumab with or without ibrutinib was superior to chemoimmunotherapy as first-line treatment in fit patients with CLL. (Funded by AbbVie and others; GAIA-CLL13 ClinicalTrials.gov number, NCT02950051; EudraCT number, 2015-004936-36.).

High karyotypic complexity is an independent prognostic factor in patients with CLL treated with venetoclax combinations.

Complex karyotypes have been associated with inferior outcomes in chronic lymphocytic leukemia (CLL) treated with chemoimmunotherapy (CIT), whereas their prognostic impact in the context of venetoclax-based treatments is still debated. In this prospective analysis on karyotype complexity in CLL, we evaluated the impact of complex (≥3 chromosomal aberrations [CAs], CKTs) and highly complex karyotypes (≥5 CAs; hCKTs) as well as specific aberrations in previously untreated patients without TP53 aberrations undergoing either CIT or time-limited venetoclax-based therapies in the phase 3 GAIA/CLL13 trial. Karyotype analyses were available for 895 of 926 patients (96.7%), of whom 153 (17%) had a CKT and 43 (5%) hCKT. In the CIT arm, CKT was associated with shorter progression-free survival (PFS) (hazard ratio [HR] 2.58; 95% confidence interval [95% CI], 1.54-4.32; P < .001) and overall survival (HR, 3.25; 95% CI, 1.03-10.26; P = .044). In the pooled venetoclax arms, a multivariable analysis identified hCKTs (HR, 1.96; 95% CI, 1.03-3.72; P = .041), but not CKTs, as independent adverse prognosticators for PFS. The presence of translocations (unbalanced and/or balanced) was also independently associated with shorter PFSs in the venetoclax arms. CIT led to the acquisition of additional CAs (mean CAs, 2.0-3.4; from baseline to CLL progression), whereas karyotype complexity remained stable after venetoclax-based treatments (2.0, both time points). This analysis establishes highly complex karyotypes and translocations as adverse prognostic factors in the context of venetoclax-based combination treatments. The findings of this study support the incorporation of karyotyping into the standard diagnostic workup of CLL, because it identifies patients at high risk of poor treatment outcomes and thereby improves prognostication. This trial was registered at www.clinicaltrials.gov as #NCT02950051.

Ibrutinib sensitizes CLL cells to venetoclax by interrupting TLR9-induced CD40 upregulation and protein translation.

Chronic lymphocytic leukemia (CLL) cells upregulate Bcl-2 proteins within the lymph node (LN) microenvironment. Signaling via B-cell receptor, Toll-like receptors and CD40 collectively reduce sensitivity to the BCL-2 inhibitor venetoclax. Time-limited treatment with venetoclax plus the BTK-inhibitor ibrutinib results in deep remissions, but how this combination affects LN-related signaling is not yet completely clear. Therefore, samples obtained from the HOVON141/VISION phase 2 clinical trial were used to analyze this. Two cycles of lead-in ibrutinib monotherapy resulted in decreased protein expression of Bcl-2 proteins in circulating CLL cells. Strikingly, at this timepoint CD40-induced venetoclax resistance was strongly attenuated, as was expression of CD40. Since CD40 signaling occurs within the CLL LN, we tested various LN-related signals that could affect CD40 signaling. While BCR stimulation had only a minor effect, TLR9 stimulation via CpG led to significantly increased CD40 expression and importantly, reverted the effects of ibrutinib treatment on venetoclax sensitivity by inducing overall protein translation. Together, these findings identify a novel effect of ibrutinib: interruption of TLR9-induced CD40 upregulation and translation of pro-survival proteins. This mechanism may potentially further inhibit priming of CLL cells in the LN microenvironment for venetoclax resistance.

The protective role of the microenvironment in hairy cell leukemia treatment: Facts and perspectives.

Hairy cell leukemia (HCL) is an incurable, rare lymphoproliferative hematological malignancy of mature B cAlthough first line therapy with purine analogues leads to positive results, almost half of HCL patients relapse after 5-10 years, and standard treatment may not be an option due to intolerance or refractoriness. Proliferation and survival of HCL cells is regulated by surrounding accessory cells and soluble signals present in the tumor microenvironment, which actively contributes to disease progression. In vitro studies show that different therapeutic approaches tested in HCL impact the tumor microenvironment, and that this milieu offers a protection affecting treatment efficacy. Herein we explore the effects of the tumor microenvironment to different approved and experimental therapeutic options for HCL. Dissecting the complex interactions between leukemia cells and their milieu will be essential to develop new targeted therapies for HCL patients.

Real-world outcomes upon second-line treatment in patients with chronic lymphocytic leukaemia.

For chronic lymphocytic leukaemia (CLL), targeted drugs have become the standard of care, in particular for second-line treatment. In this study, overall survival (OS), treatment-free survival (TFS) and adverse events (AE) were registered retrospectively in a Danish population-based cohort upon second-line treatment for CLL. Data were collected from medical records and the Danish National CLL register. For 286 patients receiving second-line treatment, three-year TFS was higher upon targeted treatment (ibrutinib/venetoclax/idelalisib) [63%, 95% confidence interval (CI) 50%-76%] compared with fludarabine, cyclophosphamide and rituximab or bendamustine and rituximab (FCR/BR) (37%, CI: 26%-48%) and chlorambucil+/-CD20-antibody (CD20Clb/Clb) (22%, CI: 10%-33%). Upon targeted treatment, three-year OS estimates were higher for targeted treatment (79%, CI: 68%-91%) compared with FCR/BR (70%, CI: 60%-81%) or CD20Clb/Clb (60%, CI: 47%-74%). The most common AEs were infections and haematological AEs; 92% of patients treated with targeted drugs had AEs, 53% of which were severe. Upon FCR/BR and CD20Clb/Clb, AEs were present for 75% and 53% respectively, of which 63% and 31% were severe. These real-world data demonstrate higher TFS and a tendency towards higher OS following targeted second-line treatment for CLL compared to chemoimmunotherapy, also for patients who may be frailer and more comorbid.

SOHO State of the Art Updates and Next Questions | Infections in Chronic Lymphocytic Leukemia Patients: Risks and Management.

Although chronic lymphocytic leukemia (CLL) is a malignancy characterized by accumulation of tumor cells in the blood, bone marrow, lymph nodes and secondary lymphoid tissues, the hallmark of the disease and the major cause of death for patients with CLL is actually immune dysfunction and associated infections. Despite improvement in treatment based on combination chemoimmunotherapy and targeted treatment with BTK and BCL-2 inhibitors leading to longer overall survival for patients with CLL, the mortality due to infections have not improved over the last 4 decades. Thus, infections are now the main cause of death for patients with CLL, posing threats to the patient whether during the premalignant state of monoclonal B lymphocytosis (MBL), during the watch & wait phase for treatment naïve patients, or upon treatment in terms of chemoimmunotherapy or targeted treatment. To test whether the natural history of immune dysfunction and infections in CLL can be changed, we have developed the machine learning based algorithm CLL-TIM.org to identify these patients. The CLL-TIM algorithm is currently being used for selection of patients for the clinical trial PreVent-ACaLL (NCT03868722), testing whether short-term treatment with the BTK inhibitor acalabrutinib and the BCL-2 inhibitor venetoclax can improve immune function and decrease the risk of infections for this high-risk patient population. We here review the background for and management of infectious risks in CLL.

Readmissions, Postdischarge Mortality, and Sustained Recovery Among Patients Admitted to Hospital With Coronavirus Disease 2019 (COVID-19).

BACKGROUND: Many interventional in-patient coronavirus disease 2019 (COVID-19) trials assess primary outcomes through day 28 post-randomization. Since a proportion of patients experience protracted disease or relapse, such follow-up period may not fully capture the course of the disease, even when randomization occurs a few days after hospitalization. METHODS: Among adults hospitalized with COVID-19 in eastern Denmark from 18 March 2020-12 January 2021 we assessed all-cause mortality, recovery, and sustained recovery 90 days after admission, and readmission and all-cause mortality 90 days after discharge. Recovery was defined as hospital discharge and sustained recovery as recovery and alive without readmissions for 14 consecutive days. RESULTS: Among 3386 patients included in the study, 2796 (82.6%) reached recovery and 2600 (77.0%) achieved sustained recovery. Of those discharged from hospital, 556 (19.9%) were readmitted and 289 (10.3%) died. Overall, the median time to recovery was 6 days (interquartile range [IQR]: 3-10), and 19 days (IQR: 11-33) among patients in intensive care in the first 2 days of admission. CONCLUSIONS: Postdischarge readmission and mortality rates were substantial. Therefore, sustained recovery should be favored to recovery outcomes in clinical COVID-19 trials. A 28-day follow-up period may be too short for the critically ill.

Chest x-ray imaging score is associated with severity of COVID-19 pneumonia: the MBrixia score.

Spatial resolution in existing chest x-ray (CXR)-based scoring systems for coronavirus disease 2019 (COVID-19) pneumonia is low, and should be increased for better representation of anatomy, and severity of lung involvement. An existing CXR-based system, the Brixia score, was modified to increase the spatial resolution, creating the MBrixia score. The MBrixia score is the sum, of a rule-based quantification of CXR severity on a scale of 0 to 3 in 12 anatomical zones in the lungs. The MBrixia score was applied to CXR images from COVID-19 patients at a single tertiary hospital in the period May 4th-June 5th, 2020. The relationship between MBrixia score, and level of respiratory support at the time of performed CXR imaging was investigated. 37 hospitalized COVID-19 patients with 290 CXRs were identified, 22 (59.5%) were admitted to the intensive care unit and 10 (27%) died during follow-up. In a Poisson regression using all 290 MBrixia scored CXRs, a higher MBrixia score was associated with a higher level of respiratory support at the time of performed CXR. The MBrixia score could potentially be valuable as a quantitative surrogate measurement of COVID-19 pneumonia severity, and future studies should investigate the score's validity and capabilities of predicting clinical outcomes.

Personalized survival probabilities for SARS-CoV-2 positive patients by explainable machine learning.

Interpretable risk assessment of SARS-CoV-2 positive patients can aid clinicians to implement precision medicine. Here we trained a machine learning model to predict mortality within 12 weeks of a first positive SARS-CoV-2 test. By leveraging data on 33,938 confirmed SARS-CoV-2 cases in eastern Denmark, we considered 2723 variables extracted from electronic health records (EHR) including demographics, diagnoses, medications, laboratory test results and vital parameters. A discrete-time framework for survival modelling enabled us to predict personalized survival curves and explain individual risk factors. Performance on the test set was measured with a weighted concordance index of 0.95 and an area under the curve for precision-recall of 0.71. Age, sex, number of medications, previous hospitalizations and lymphocyte counts were identified as top mortality risk factors. Our explainable survival model developed on EHR data also revealed temporal dynamics of the 22 selected risk factors. Upon further validation, this model may allow direct reporting of personalized survival probabilities in routine care.

Minimal residual disease-guided stop and start of venetoclax plus ibrutinib for patients with relapsed or refractory chronic lymphocytic leukaemia (HOVON141/VISION): primary analysis of an open-label, randomised, phase 2 trial.

BACKGROUND: Targeted time-limited treatment options are needed for patients with relapsed or refractory chronic lymphocytic leukaemia. The aim of this study was to investigate the efficacy of minimal residual disease (MRD)-guided, time-limited ibrutinib plus venetoclax treatment in this patient group. METHODS: HOVON141/VISION was an open-label, randomised, phase 2 trial conducted in 47 hospitals in Belgium, Denmark, Finland, the Netherlands, Norway, and Sweden. Eligible participants were aged 18 years or older with previously treated chronic lymphocytic leukaemia with or without TP53 aberrations; had not been exposed to Bruton tyrosine-kinase inhibitors or BCL2 inhibitors; had a creatinine clearance rate of 30 mL/min or more; and required treatment according to International Workshop on Chronic Lymphocytic Leukemia 2018 criteria. Participants with undetectable MRD (<10-4; less than one chronic lymphocytic leukaemia cell per 10 000 leukocytes) in peripheral blood and bone marrow after 15 28-day cycles of oral ibrutinib (420 mg once daily) plus oral venetoclax (weekly ramp-up 20 mg, 50 mg, 100 mg, 200 mg, up to 400 mg once daily) were randomly assigned (1:2) to ibrutinib maintenance or treatment cessation. Patients who were MRD positive continued to receive ibrutinib monotherapy. Patients who became MRD (>10-2) during observation reinitiated treatment with ibrutinib plus venetoclax. The primary endpoint was progression-free survival at 12 months after random assignment in the treatment cessation group. Progression-free survival was analysed in the intention-to-treat population. All patients who received at least one dose of study drug were included in the safety assessment. The study is registered at ClinicalTrials.gov, NCT03226301, and is active but not recruiting. FINDINGS: Between July 12, 2017, and Jan 21, 2019, 230 patients were enrolled, 225 of whom were eligible. 188 (84%) of 225 completed treatment with ibrutinib plus venetoclax and were tested for MRD at cycle 15. After cycle 15, 78 (35%) patients had undetectable MRD and 72 (32%) were randomly assigned to a treatment group (24 to ibrutinib maintenance and 48 to treatment cessation). The remaining 153 patients were not randomly assigned and continued with ibrutinib monotherapy. Median follow-up of 208 patients still alive and not lost to follow-up at data cutoff on June 22, 2021, was 34·4 months (IQR 30·6-37·9). Progression-free survival after 12 months in the treatment cessation group was 98% (95% CI 89-100). Infections (in 130 [58%] of 225 patients), neutropenia (in 91 [40%] patients), and gastrointestinal adverse events (in 53 [24%] patients) were the most frequently reported; no new safety signals were detected. Serious adverse events were reported in 46 (40%) of 116 patients who were not randomly assigned and who continued ibrutinib maintenance after cycle 15, eight (33%) of 24 patients in the ibrutinib maintenance group, and four (8%) of 48 patients in the treatment cessation group. One patient who was not randomly assigned had a fatal adverse event (bleeding) deemed possibly related to ibrutinib. INTERPRETATION: These data point to a favourable benefit-risk profile of MRD-guided, time-limited treatment with ibrutinib plus venetoclax for patients with relapsed or refractory chronic lymphocytic leukaemia, suggesting that MRD-guided cessation and reinitiation is feasible in this patient population. FUNDING: AbbVie and Janssen.