Ibrutinib Plus Venetoclax for First-Line Treatment of Chronic Lymphocytic Leukemia: Primary Analysis Results From the Minimal Residual Disease Cohort of the Randomized Phase II CAPTIVATE Study

Flow Cytometric MRD Detection in Selected Mature B-Cell Malignancies

The quantification of submicroscopic minimal residual disease (MRD) after therapy proved to have independent prognostic significance in many mature B-cell malignancies. With the advent of routine benchtop cytometers capable of simultaneously analyzing ≥8 colors and with improved standardization, flow cytometry has become the method of choice for MRD assessments in some lymphoma entities. Herein we describe general aspects of flow cytometric standardization. Chronic lymphocytic leukemia (CLL) and multiple myeloma (MM) are used as examples to explain the technical standardization of flow cytometry for MRD detection according to EuroFlow strategies. MRD data acquisition and detailed analysis in MM and CLL is a particular focus of this chapter.

Recent Advances in the Molecular Biology of Chronic Lymphocytic Leukemia: How to Define Prognosis and Guide Treatment

Chronic Lymphocytic Leukemia (CLL) is the most frequent type of leukemia in Western countries. In recent years, there have been important advances in the knowledge of molecular alterations that underlie the disease's pathogenesis. Very heterogeneous prognostic subgroups have been identified by the mutational status of immunoglobulin heavy variable genes (IGVH), FISH analysis and molecular evaluation of TP53 mutations. Next-generation sequencing (NGS) technologies have provided a deeper characterization of the genomic and epigenomic landscape of CLL. New therapeutic targets have led to a progressive reduction of traditional chemoimmunotherapy in favor of specific biological agents. Furthermore, in the latest clinical trials, the minimal residual disease (MRD) has emerged as a potent marker of outcome and a guide to treatment duration. This review focuses on recent insights into the understanding of CLL biology. We also consider the translation of these findings into the development of risk-adapted and targeted therapeutic approaches.

Utilizing risk factors to guide treatment decisions in chronic lymphocytic leukemia

INTRODUCTION

In the era of chemo-immunotherapy, high-risk factors unequivocally predicted inferior outcomes for patients with CLL. The widespread adoption of BTK inhibitors has challenged the practical implications of such testing, as many patients have improved outcomes despite the presence of high-risk features. The impact of adverse prognostic factors, such as unmutated IGHV, on survival has been ameliorated by continuous treatment with BTK inhibitors, but not by finite-duration therapy with venetoclax-based combinations. Furthermore, TP53 abnormalities continue to be associated with worse outcomes in the era of novel agents. New treatment modalities, such as pirtobrutinib, lisocabtagene maraleucel, and ongoing studies combining BTK inhibitors with venetoclax, raise new questions on the significance of prognostic factors of survival for patients with CLL.

AREAS COVERED

Herein, we summarized the available literature on patients with CLL harboring high-risk biomarkers, with a focus on data from key clinical trials.

EXPERT OPINION

Testing for prognostic biomarkers will remain relevant to identify patients who may have increased benefit from novel therapeutic strategies, such as combination therapies and novel agents. Patients with high-risk disease should be encouraged to participate in clinical trials.

Current Approaches and Novel Agents in the Treatment of Chronic Lymphocytic Leukemia

The treatment of CLL has evolved from traditional chemoimmunotherapy (CIT) to an increasing number of targeted and biologic approaches. Randomized trials have demonstrated superiority of covalent bruton tyrosine kinase inhibitors (cBTKis) over CIT, and second-generation compounds such as acalabrutinib and zanubrutinib appear to have a more favorable efficacy/safety profile than ibrutinib. The noncovalent BTKi, pirtobrutinib, has shown impressive activity after failure of the cBTKis and is quite tolerable. The Bcl-2 inhibitor venetoclax plus a CD20, generally obinutuzumab, provides a high level of efficacy as initial treatment or after failure on a cBTKi, with many patients achieving a state of undetectable minimal residual disease. Promising novel approaches include BTK degraders, bispecific antibodies, and chimeric antigen receptor T-cell (CAR-T)-cell therapy. What is clear is that CIT is archaic, and current and future targeted approaches will continue to improve the outcome for patients with chronic lymphocytic leukemia.

The Economic Impact of Treatment Sequencing in Chronic Lymphocytic Leukemia in Canada Using Venetoclax plus Obinutuzumab

BACKGROUND

Bruton tyrosine kinase inhibitors (BTKis) represent an advancement in chronic lymphocytic leukemia; however, these agents are administered continuously until disease progression or unacceptable toxicity, raising concerns about their affordability. Venetoclax in combination with obinutuzumab (VO) is a fixed-duration (12-month) treatment, approved in Canada in 2020. This study estimated the total cumulative cost of different treatment sequences and evaluated the economic impact of introducing treatment sequences with/without VO, from a Canadian health care system perspective.

METHODS

A 10-year partitioned survival model was developed, considering key clinical parameters and direct medical costs. Results were stratified by TP53 aberration.

RESULTS

Treatment sequences starting with first-line (1L) VO resulted in lower 10-year cumulative costs compared to sequences starting with BTKis administered until disease progression, across both TP53 aberration subgroups. With a maximum of three lines of treatment over a 10-year period, cumulative costs were largely determined by the first two lines of treatment. When comparing sequences with the same 1L treatment, sequences with BTKis in second-line incurred greater costs compared to fixed-duration regimens.

CONCLUSIONS

Overall, the economic impact of treating all patients with VO led to 10-year cumulative savings of CAD 169,341 and CAD 293,731 per patient, without and with TP53 aberration, respectively. These savings are mainly due to reductions in treatment costs associated with fixed treatment duration.

PI3K Inhibitors in Hematology: When One Door Closes…

The PI3K signaling pathway regulates key cellular processes and is one of the most aberrantly activated pathways in cancer. The class I PI3K catalytic subunits p110γ and p110δ are highly enriched in leukocytes, providing an additional rationale for targeting these PI3Ks in hematologic malignancies. In 2014, the PI3Kδ inhibitor idelalisib was the first of four PI3K inhibitors (PI3Ki) to receive regulatory approval for relapsed B-cell malignancies. This was followed by approvals of the pan-class I inhibitor copanlisib (2017), the dual PI3Kγ/δ inhibitor duvelisib (2018), and the PI3Kδ and casein kinase 1ε inhibitor umbralisib (2021). Copanlisib and umbralisib received accelerated approvals, whereas idelalisib and duvelisib received initial accelerated approvals followed by full approvals. The accelerated approvals were based on overall response rates; however, follow-up studies showed increased risk of death and serious side effects. Furthermore, the confirmatory trial with copanlisib failed to show an improvement in progression-free survival when compared with chemoimmunotherapy. These developments led to black box warnings for idelalisib and duvelisib and withdrawal of copanlisib and umbralisib from the market by their manufacturers. Given the uncertain future of this drug class, additional manufacturers terminated ongoing phase III trials with novel PI3Kis. In this study, we review the development and current status of PI3Kis in hematology, limitations to their use, and our perspective on whether there is a future for PI3Kis in hematology.

Pharmacological management of chronic lymphocytic leukemia: current and emerging therapies

INTRODUCTION

Chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL), characterized by its monoclonal lymphoproliferative nature, is an indolent but incurable malignancy. The treatment landscape of CLL/SLL has drastically transformed in the last decade since the introduction of targeted therapy and immune-effector T-cell therapy. The paradigm shift from chemoimmunotherapy to targeted and cellular therapies was largely driven by improved efficacy and safety. With the success of targeted therapies, novel agents and combinations are rapidly emerging on the horizon.

AREAS COVERED

In this review, we will summarize clinical evidence supporting current and emerging therapies with emphasis on investigational therapies and novel combinations of commercial agents. Clinical trials were identified via clinicaltrials.gov, and a PubMed literature search was last performed in June 2024.

EXPERT OPINION

With the availability of more effective and better-tolerated treatments for CLL/SLL, the role of early intervention should be further investigated due to its potential to alter disease course, delay progression, and improve overall survival rates. With many highly effective agents and combinations expected to become commercially available, attention to safety profiles and careful selection of patients for each treatment will be critical, with consideration of comorbidities, logistical issues, and financial burden of treatment.

Severe infections in patients with chronic lymphocytic leukemia included in trials investigating BTK and BCL2 inhibitors

Bruton tyrosine kinase inhibitors (BTKi) and the BCL-2 inhibitor venetoclax have significantly improved the prognosis of patients with chronic lymphocytic leukemia (CLL). However, the incidence of severe infections in patients receiving these agents needs to be better understood. Our review aimed to provide an overview of grade ≥3 infections in patients with CLL who received BTKi and venetoclax-based therapy in prospective trials. Infection rates were influenced by the age of patients and the duration of follow-up. For treatment-naive (TN) patients receiving BTKi, infection rates ranged between 11.4 % and 27.4 % and were close to 30 % in relapsed/refractory (R/R) patients. TN and R/R patients receiving fixed-duration venetoclax-based treatments showed variable rates, with maximum values around 20 %. Opportunistic and fatal infections were uncommon. In conclusion, infections remain a concern in patients with CLL receiving targeted agents. A better definition of factors increasing infection vulnerability could help identify those patients who require infection prophylaxis.

Measurable Residual Disease and Clinical Outcomes in Chronic Lymphocytic Leukemia: A Systematic Review and Meta-Analysis

Importance

Measurable residual disease (MRD) refers to the presence of disease at low levels not detected by conventional pathologic analysis. The association of MRD status as a surrogate end point of clinical outcome in chronic lymphocytic leukemia (CLL) has not been established in the era of targeted agents. Assessing the association of MRD with progression-free survival (PFS) may improve its role as a surrogate marker and allow its use to accelerate drug development.

Objective

To assess the association between MRD and PFS in CLL using data from prospective clinical trials that studied targeted agents or obinutuzumab-based treatment.

Data Sources

Clinical studies on CLL were identified via searches of PubMed, Embase, Scopus, and Web of Science from inception through July 31, 2023.

Study Selection

Prospective, single-arm, and randomized clinical trials that assessed targeted agents or obinutuzumab-based treatment and reported PFS by MRD status were included. Studies with insufficient description of MRD information were excluded.

Data Extraction and Synthesis

Study sample size, median patient age, median follow-up time, line of treatment, MRD detection method and time points, and survival outcomes were extracted.

Main Outcomes and Measures

Analyses of survival probabilities and hazard ratios (HRs) were conducted for PFS according to MRD status. Meta-analyses were performed using a random-effects model.

Results

A total of 11 prospective clinical trials (9 randomized and 2 nonrandomized) including 2765 patients were analyzed. Achieving undetectable MRD (uMRD) at 0.01% was associated with an HR of 0.28 (95% CI, 0.20-0.39; P < .001) for PFS. Median PFS was not reached in both groups (uMRD vs MRD), but the estimated 24-month PFS was better in the uMRD group (91.9% [95% CI, 88.8%-95.2%] vs 75.3% [95% CI, 64.7%-87.6%]; P < .001). The association of uMRD with PFS was observed in subgroup analyses in the first-line treatment setting (HR, 0.24; 95% CI, 0.18-0.33), relapsed or refractory disease setting (HR, 0.34; 95% CI, 0.16-0.71), and trials using time-limited therapy (HR, 0.28; 95% CI, 0.19-0.40).

Conclusions and Relevance

The findings of this systematic review and meta-analysis suggest that assessing MRD status as an end point in clinical trials and as a surrogate of PFS may improve trial efficiency and potentially allow for accelerated drug registration.

End Point Surrogacy in First-Line Chronic Lymphocytic Leukemia

PURPOSE

Surrogate end points are commonly used to estimate treatment efficacy in clinical studies of chronic lymphocytic leukemia (CLL). This patient- and trial-level analysis describes the correlation between progression-free survival (PFS) and minimal residual disease (MRD) with overall survival (OS) in first-line trials for CLL.

PATIENTS AND METHODS

First, patient-level correlation was confirmed using source data from 12 frontline German CLL Study Group (GCLLSG)-trials. Additionally, a joint-frailty copula model was fitted to validate correlation in the setting of targeted therapies (TT). Second, a meta-analysis of first-line phase III trials in CLL from 2008 to 2024 was performed. Treatment effect correlation was quantified from seven GCLLSG and nine published trials, using hazard ratios (HRs) for time-to-event and odds ratios for binary end points.

RESULTS

The GCLLSG analysis set comprised 4,237 patients. Patient-level correlation for PFS/OS was strong with Spearman Rho >0.9. The joint-frailty copula indicated a weak correlation for chemotherapy/chemoimmunotherapy (C/CIT) with a tau of 0.52 (95% CI, 0.49 to 0.55) while the correlation was strong for TT (tau, 0.91 [95% CI, 0.89 to 0.93). The meta-analysis set contained a total of 8,065 patients including 5,198 (64%) patients treated with C/CIT and 2,867 (36%) treated with TT. Treatment-effect correlation of the HRs for PFS and OS was R = 0.75 (95% CI, 0.74 to 0.76, R2 = 0.56) while correlation of end-of-treatment MRD with PFS and OS was R = 0.88 (95% CI, -0.87 to 0.89; R2 = 0.78) and 0.71 (95% CI, 0.69 to 0.73; R2 = 0.5), respectively.

CONCLUSION

Patient-level correlation was confirmed in the setting of TTs while treatment-effect correlation between PFS and OS remains uncertain. MRD response status showed a high treatment-effect correlation with PFS but not OS, with the caveat of a limited number of randomized trials with available MRD data.

Chronic lymphocytic leukaemia

The last decade has seen remarkable progress in our understanding of disease biology of chronic lymphocytic leukaemia (CLL) and the development of novel targeted therapies. Randomised clinical trials have reported improved progression-free survival and overall survival with targeted therapies compared with chemoimmunotherapy, and thereby the role of chemoimmunotherapy in todays' era for treatment of CLL is limited. Bruton tyrosine kinase (BTK) inhibitors, BCL2 inhibitors, and CD20 monoclonal antibodies have been established as appropriate therapy options for patients with CLL, both as the first-line treatment and in the treatment of relapsed or refractory CLL. Several ongoing phase 3 trials are exploring different combinations of targeted therapies, and the results of these trials might change the treatment framework in first-line treatment of CLL. Non-covalent BTK inhibitors, chimeric antigen receptor T-cell therapy, and other therapeutic strategies are being investigated in relapsed CLL. Some of the therapies used in relapsed CLL, such as non-covalent BTK inhibitors, are now being pursued in earlier lines of therapy, including first-line treatment of CLL.

Measurable residual disease (MRD)-testing in haematological cancers: A giant leap forward or sideways?

Measurable residual disease (MRD)-testing is used in many haematological cancers to estimate relapse risk and to direct therapy. Sometimes MRD-test results are used for regulatory approval. However, some people including regulators wrongfully believe results of MRD-testing are highly accurate and of proven efficacy in directing therapy. We review MRD-testing technologies and evaluate the accuracy of MRD-testing for predicting relapse and the strength of evidence supporting efficacy of MRD-guided therapy. We show that at the individual level MRD-test results are often an inaccurate relapse predictor. Also, no convincing data indicate that increasing therapy-intensity based on a positive MRD-test reduces relapse risk or improves survival. We caution against adjusting therapy-intensity based solely on results of MRD-testing.

Unmutated IGHV at diagnosis in patients with early stage CLL independently predicts for shorter follow-up time to first treatment (TTFT)

The mutational status of the IGHV gene is routinely assessed in patients with chronic lymphocytic leukaemia (CLL), since it is both prognostic of clinical outcome and predictive of response to treatment. This study evaluates the IGHV mutational status, assessed in newly diagnosed CLL patients, as a stand-alone predictor of time to first treatment (TTFT). We analysed the data of 236 CLL patients, diagnosed at our centre between January 2004 and September 2020, with a minimum follow-up period of 3.0 years, Binet A-B and Rai 0-II stages. IGHV was unmutated in 38.1 % and mutated in 61.9 % of cases. The univariate analysis showed a statistically significant difference (p < 0.001) in TTFT based on unmutated (85.2 % at 14 years, 95 % CI = 63.3-94.5 %) or mutated (41.3 % at 14 years, 95 % CI = 29.5-51.8 %) and the need for treatment at 1, 3 and 5 years was of 20.0 % vs 4.1 % (p < 0.001), 42.7 % vs 11.4 % (p < 0.001) and 55.8 % vs 20.0 % (p < 0.001) in unmutated and mutated IGHV patients, respectively. Multivariate analysis confirmed that unmutated IGHV status negatively affects TTFT (p < 0.001), in addition to high-risk genomic aberration (p = 0.025), Rai stage I (p = 0.007) and II (p-value < 0.001). The difference in TTFT based on unmutated or mutated IGHV status remains statistically significant also when considering the subgroups by the genomic aberrations and Rai stages. Our findings suggest that, with the single analysis of the IGHV mutational status at CLL diagnosis, along with clinical and laboratory data, and without karyotype and TP53 data, clinicians will have prognostic and predictive indications for the first clinical treatment and appropriate follow-up of patients.

Chronic Lymphocytic Leukemia: Prognostic Factors in the Era of Novel Drugs

Novel drugs have profoundly changed the outcomes in chronic lymphocytic leukemia (CLL) patients, and the traditional prognostic factors that were identified in the era of chemoimmunotherapy need to be validated in the context of these new targeted therapies. Currently, the most important prognostic genetic biomarkers are the immunoglobulin heavy chain variable (IGHV) mutational status, genetic aberrations including del(17p)/TP53 abnormalities, and the complex karyotype. In this review, we discuss the prognostic role of these genomic markers in relation to novel treatments. Moreover, we present and discuss new scoring systems that were elaborated and validated in the era of new drugs. In routine clinical practice, the application of an extensive genomic work-up with validated prognostic markers could improve the identification of "very high-risk" CLL patients who could benefit from novel, more effective targeted treatments.

Acalabrutinib, venetoclax, and obinutuzumab in relapsed/refractory CLL: final efficacy and ctDNA analysis of the CLL2-BAAG trial

ABSTRACT

The phase 2 CLL2-BAAG trial tested the measurable residual disease (MRD)-guided triple combination of acalabrutinib, venetoclax, and obinutuzumab after optional bendamustine debulking in 45 patients with relapsed/refractory chronic lymphocytic leukemia (CLL). MRD was measured by flow cytometry (FCM; undetectable MRD <10-4) in peripheral blood (PB) and circulating tumor DNA (ctDNA) using digital droplet polymerase chain reaction of variable-diversity-joining (VDJ) rearrangements and CLL-related mutations in plasma. The median number of previous treatments was 1 (range, 1-4); 18 patients (40%) had received a Bruton tyrosine kinase inhibitor (BTKi) and/or venetoclax before inclusion, 14 of 44 (31.8%) had TP53 aberrations, and 34 (75.6%) had unmutated immunoglobulin heavy-chain variable region genes. With a median observation time of 36.3 months and all patients off-treatment for a median of 21.9 months, uMRD <10-4 in PB was achieved in 42 of the 45 patients (93.3%) at any time point, including 17 of 18 (94.4%) previously exposed to venetoclax/BTKi and 13 of 14 (92.9%) with TP53 aberrations. The estimated 3-year progression-free and overall survival rates were 85.0% and 93.8%, respectively. Overall, 585 paired FCM/ctDNA samples were analyzed and 18 MRD recurrences (5 with and 13 without clinical progression) occurred after the end of treatment. Twelve samples were first detected by ctDNA, 3 by FCM, and 3 synchronously. In conclusion, time-limited MRD-guided acalabrutinib, venetoclax, and obinutuzumab achieved deep remissions in almost all patients with relapsed/refractory CLL. The addition of ctDNA-based analyses to FCM MRD assessment seems to improve early detection of relapses. This trial was registered at www.clinicaltrials.gov as #NCT03787264.

What clinicians should know about surrogate end points in hematologic malignancies

ABSTRACT

Use of surrogates as primary end points is commonplace in hematology/oncology clinical trials. As opposed to prognostic markers, surrogates are end points that can be measured early and yet can still capture the full effect of treatment, because it would be captured by the true outcome (eg, overall survival). We discuss the level of evidence of the most commonly used end points in hematology and share recommendations on how to apply and evaluate surrogate end points in research and clinical practice. Based on the statistical literature, this clinician-friendly review intends to build a bridge between clinicians and surrogacy specialists.

Realizing precision medicine in chronic lymphocytic leukemia: Remaining challenges and potential opportunities

Patients with chronic lymphocytic leukemia (CLL) exhibit diverse clinical outcomes. An expanding array of genetic tests is now employed to facilitate the identification of patients with high-risk disease and inform treatment decisions. These tests encompass molecular cytogenetic analysis, focusing on recurrent chromosomal alterations, particularly del(17p). Additionally, sequencing is utilized to identify TP53 mutations and to determine the somatic hypermutation status of the immunoglobulin heavy variable gene. Concurrently, a swift advancement of targeted treatment has led to the implementation of novel strategies for patients with CLL, including kinase and BCL2 inhibitors. This review explores both current and emerging diagnostic tests aimed at identifying high-risk patients who should benefit from targeted therapies. We outline existing treatment paradigms, emphasizing the importance of matching the right treatment to the right patient beyond genetic stratification, considering the crucial balance between safety and efficacy. We also take into consideration the practical and logistical issues when choosing a management strategy for each individual patient. Furthermore, we delve into the mechanisms underlying therapy resistance and stress the relevance of monitoring measurable residual disease to guide treatment decisions. Finally, we underscore the necessity of aggregating real-world data, adopting a global perspective, and ensuring patient engagement. Taken together, we argue that precision medicine is not the mere application of precision diagnostics and accessibility of precision therapies in CLL but encompasses various aspects of the patient journey (e.g., lifestyle exposures and comorbidities) and their preferences toward achieving true personalized medicine for patients with CLL.

Ibrutinib followed by ofatumumab consolidation in previously untreated patients with chronic lymphocytic leukemia (CLL): GELLC-7 trial from the Spanish group of CLL (GELLC)

Background

BTK inhibitors have been concurrently administered with anti-CD20 monoclonal antibodies (mAbs) in chronic lymphocytic leukemia (CLL). However, the optimal regimen for combining these two drugs remains pending.

Methods

This multi-center phase 2 study aimed to analyze whether consolidation with ofatumumab improved the response in patients with CLL receiving front-line treatment with ibrutinib. Patients received 12 cycles of ibrutinib monotherapy. Those who achieved CR after this induction were maintained on ibrutinib. Conversely, those who did not attain CR continued with ibrutinib in addition to a consolidation, which involved 7 doses of ofatumumab. The primary objective was the complete response (CR) rate at cycle 20. This study is registered within the EU Clinical Trials Register (EudraCT 2016-004937-26).

Findings

Between September 8, 2017, and May 21, 2018, 84 patients (median age, 69 years) were included. After completion of 12 cycles of ibrutinib (n = 80), 4 patients (5%) were in CR, 67 (84%) in partial response (PR), and 6 patients (7%) had a PR with lymphocytosis (PRL). After consolidation with ofatumumab, 20 patients improved the response from PR to CR and 6 patients with PRL obtained a PR. Seventy-one patients (85%) completed 20 cycles of treatment, with a CR rate of 24/71 (34%). According to the intention-to-treat analysis at cycle 20, the ORR was 69/84 (82.2%), with a CRR of 24/84 (28.6%). Progression-free survival and overall survival at 48-months were 89.9% (CI: 82.4-95.5) and 92.2% (CI: 85.3-97.1), respectively.

Interpretation

These findings underscore the potential for a consolidation strategy in CLL, wherein the addition of a mAb in patients with low tumor burden might enhance the quality of the response.

Funding

The study was funded by Janssen that also supplied ibrutinib, whereas ofatumumab was supplied by Novartis.

Automated quantification of measurable residual disease in chronic lymphocytic leukemia using an artificial intelligence-assisted workflow

Detection of measurable residual disease (MRD) in chronic lymphocytic leukemia (CLL) is an important prognostic marker. The most common CLL MRD method in current use is multiparameter flow cytometry, but availability is limited by the need for expert manual analysis. Automated analysis has the potential to expand access to CLL MRD testing. We evaluated the performance of an artificial intelligence (AI)-assisted multiparameter flow cytometry (MFC) workflow for CLL MRD. We randomly selected 113 CLL MRD FCS files and divided them into training and validation sets. The training set (n = 41) was gated by expert manual analysis and used to train the AI model. We then compared the validation set (n = 72) MRD results obtained by the AI-assisted analysis versus those by expert manual analysis using the Pearson correlation coefficient and Bland-Altman plot method. In the validation set, the AI-assisted analysis correctly categorized cases as MRD-negative versus MRD-positive in 96% of cases. When comparing the AI-assisted analysis versus the expert manual analysis, the Pearson r was 0.8650, mean bias was 0.2237 log10 units, and the 95% limit of agreement (LOA) was ±1.0282 log10 units. The AI-assisted analysis performed sub-optimally in atypical immunophenotype CLL and in cases lacking residual normal B cells. When excluding these outlier cases, the mean bias improved to 0.0680 log10 units and the 95% LOA to ±0.2926 log10 units. An automated AI-assisted workflow allows for the quantification of MRD in CLL with typical immunophenotype. Further work is required to improve performance in atypical immunophenotype CLL.

The prognostic significance of genomic complexity in patients with CLL

Chromosomal aberrations are a common feature of cancer and can fuel cancer progression and treatment resistance. In chronic lymphocytic leukemia (CLL), the presence of multiple chromosomal aberrations is commonly referred to as "genomic complexity" or "complex karyotype"- (CKT). In the context of chemo- and chemoimmunotherapy, genomic complexity is associated with poor response to treatment and short survival, while some targeted therapies are able to mitigate its adverse prognostic impact. This article reviews currently available data and literature on the role of genomic complexity in CLL. The currently established tools to measure genomic complexity in patients with CLL are summarized and their strengths and weaknesses for routine diagnostics are evaluated. Moreover, possible definitions of CKT as an indicator for genomic complexity are discussed. Finally, data on the impact of CKT on clinical outcomes of patients with CLL are reviewed and the implications for patient stratification are presented.

First-line venetoclax combinations versus chemoimmunotherapy in fit patients with chronic lymphocytic leukaemia (GAIA/CLL13): 4-year follow-up from a multicentre, open-label, randomised, phase 3 trial

BACKGROUND

In the primary analysis report of the GAIA/CLL13 trial, we found that venetoclax-obinutuzumab and venetoclax-obinutuzumab-ibrutinib improved undetectable measurable residual disease (MRD) rates and progression-free survival compared with chemoimmunotherapy in patients with previously untreated chronic lymphocytic leukaemia. However, to our knowledge, no data on direct comparisons of different venetoclax-based combinations are available.

METHODS

GAIA/CLL13 is an open-label, randomised, phase 3 study conducted at 159 sites in ten countries in Europe and the Middle East. Eligible patients were aged 18 years or older, with a life expectancy of at least 6 months, an Eastern Cooperative Oncology group performance status of 0-2, a cumulative illness rating scale score of 6 or lower or a single score of 4 or lower, and no TP53 aberrations. Patients were randomly assigned (1:1:1:1), with a computer-generated list stratified by age, Binet stage, and regional study group, to either chemoimmunotherapy, venetoclax-rituximab, venetoclax-obinutuzumab, or venetoclax-obinutuzumab-ibrutinib. All treatments were administered in 28-day cycles. Patients in the chemoimmunotherapy group received six cycles of treatment, with patients older than 65 years receiving intravenous bendamustine (90 mg/m2, days 1-2), whereas patients aged 65 years or younger received intravenous fludarabine (25 mg/m2, days 1-3) and intravenous cyclophosphamide (250 mg/m2, days 1-3). Intravenous rituximab (375 mg/m2, day 1 of cycle 1; 500 mg/m2, day 1 of cycles 2-6) was added to chemotherapy. In the experimental groups, patients received daily venetoclax (400 mg orally) for ten cycles after a 5-week ramp-up phase starting on day 22 of cycle 1. In the venetoclax-rituximab group, intravenous rituximab (375 mg/m2, day 1 of cycle 1; 500 mg/m2, day 1 of cycles 2-6) was added. In the obinutuzumab-containing groups, obinutuzumab was added (cycle 1: 100 mg on day 1, 900 mg on day 2, and 1000 mg on days 8 and 15; cycles 2-6: 1000 mg on day 1). In the venetoclax-obinutuzumab-ibrutinib group, daily ibrutinib (420 mg orally, from day 1 of cycle 1) was added until undetectable MRD was reached in two consecutive measurements (3 months apart) or until cycle 36. The planned treatment duration was six cycles in the chemoimmunotherapy group, 12 cycles in the venetoclax-rituximab and the venetoclax-obinutuzumab group and between 12 and 36 cycles in the venetoclax-obinutuzumab-ibrutinib group. Coprimary endpoints were the undetectable MRD rate in peripheral blood at month 15 for the comparison of venetoclax-obinutuzumab versus standard chemoimmunotherapy and investigator-assessed progression-free survival for the comparison of venetoclax-obinutuzumab-ibrutinib versus standard chemoimmunotherapy, both analysed in the intention-to-treat population (ie, all patients randomly assigned to treatment) with a split α of 0·025 for each coprimary endpoint. Both coprimary endpoints have been reported elsewhere. Here we report a post-hoc exploratory analysis of updated progression-free survival results after a 4-year follow-up of our study population. Safety analyses included all patients who received at least one dose of study treatment. This study is registered with ClinicalTrials.gov, NCT02950051, recruitment is complete, and all patients are off study treatment.

FINDINGS

Between Dec 13, 2016, and Oct 13, 2019, 1080 patients were screened and 926 were randomly assigned to treatment (chemoimmunotherapy group n=229; venetoclax-rituximab group n=237; venetoclax-obinutuzumab group n=229; and venetoclax-obinutuzumab-ibrutinib group n=231); mean age 60·8 years (SD 10·2), 259 (28%) of 926 patients were female, and 667 (72%) were male (data on race and ethnicity are not reported). At data cutoff for this exploratory follow-up analysis (Jan 31, 2023; median follow-up 50·7 months [IQR 44·6-57·9]), patients in the venetoclax-obinutuzumab group had significantly longer progression-free survival than those in the chemoimmunotherapy group (hazard ratio [HR] 0·47 [97·5% CI 0·32-0·69], p<0·0001) and the venetoclax-rituximab group (0·57 [0·38-0·84], p=0·0011). The venetoclax-obinutuzumab-ibrutinib group also had a significantly longer progression-free survival than the chemoimmunotherapy group (0·30 [0·19-0·47]; p<0·0001) and the venetoclax-rituximab group (0·38 [0·24-0·59]; p<0·0001). There was no difference in progression-free survival between the venetoclax-obinutuzumab-ibrutinib and venetoclax-obinutuzumab groups (0·63 [0·39-1·02]; p=0·031), and the proportional hazards assumption was not met for the comparison between the venetoclax-rituximab group versus the chemoimmunotherapy group (log-rank p=0·10). The estimated 4-year progression-free survival rate was 85·5% (97·5% CI 79·9-91·1; 37 [16%] events) in the venetoclax-obinutuzumab-ibrutinib group, 81·8% (75·8-87·8; 55 [24%] events) in the venetoclax-obinutuzumab group, 70·1% (63·0-77·3; 84 [35%] events) in the venetoclax-rituximab group, and 62·0% (54·4-69·7; 90 [39%] events) in the chemoimmunotherapy group. The most common grade 3 or worse treatment-related adverse event was neutropenia (114 [53%] of 216 patients in the chemoimmunotherapy group, 109 [46%] of 237 in the venetoclax-rituximab group, 127 [56%] of 228 in the venetoclax-obinutuzumab group, and 112 [48%] of 231 in the venetoclax-obinutuzumab-ibrutinib group). Deaths determined to be associated with study treatment by the investigator occurred in three (1%) patients in the chemoimmunotherapy group (n=1 due to each of sepsis, metastatic squamous cell carcinoma, and Richter's syndrome), none in the venetoclax-rituximab and venetoclax-obinutuzumab groups, and four (2%) in the venetoclax-obinutuzumab-ibrutinib group (n=1 due to each of acute myeloid leukaemia, fungal encephalitis, small-cell lung cancer, and toxic leukoencephalopathy).

INTERPRETATION

With more than 4 years of follow-up, venetoclax-obinutuzumab and venetoclax-obinutuzumab-ibrutinib significantly extended progression-free survival compared with both chemoimmunotherapy and venetoclax-rituximab in previously untreated, fit patients with chronic lymphocytic leukaemia, thereby supporting their use and further evaluation in this patient group, while still considering the higher toxicities observed with the triple combination.

FUNDING

AbbVie, Janssen, and F Hoffmann-La Roche.

Covalent Bruton's Tyrosine Kinase Inhibitors in Chronic Lymphocytic Leukemia

Inhibitors of Bruton's tyrosine kinase (BTK) are among the most widely used therapies for chronic lymphocytic leukemia (CLL) and established a new expectation for efficacy and safety in the treatment of this disease. Currently there are 3 covalent inhibitors of BTK approved for the treatment of CLL: ibrutinib, acalabrutinib, and zanubrutinib. The first-in-class covalent BTK inhibitor is ibrutinib, which as monotherapy has excellent efficacy in the front-line setting with a 7-year progression free survival (PFS) of 59%. Ibrutinib-based therapies have also demonstrated superiority over standard chemoimmunotherapy in the front-line and the relapsed/refractory setting. Acalabrutinib is a second-generation BTK inhibitor that has higher selectivity to BTK. Acalabrutinib has efficacy in both frontline and relapsed CLL and is associated with a decreased incidence of atrial fibrillation and hypertension when compared to ibrutinib. Like acalabrutinib, zanubrutinib was designed to be more selective for BTK than ibrutinib and to maximize BTK inhibition in tissues. Zanubrutinib has demonstrated clinical efficacy in first line and relapsed/refractory setting. These agents are indicated as monotherapy, with dosing until disease progression or intolerable toxicity, and are mainly differentiated by safety profile, although efficacy differences may exist as well. Combination with CD20 monoclonal antibodies and/or BCL2 inhibitors are alternative options for use. Here we will review efficacy and safety considerations with these agents.

Monitoring Response and Resistance to Treatment in Chronic Lymphocytic Leukemia

The recent evolution in chronic lymphocytic leukemia (CLL) targeted therapies led to a progressive change in the way clinicians manage the goals of treatment and evaluate the response to treatment in respect to the paradigm of the chemoimmunotherapy era. Continuous therapies with BTK inhibitors achieve prolonged and sustained control of the disease. On the other hand, venetoclax and anti-CD20 monoclonal antibodies or, more recently, ibrutinib plus venetoclax combinations, given for a fixed duration, achieve undetectable measurable residual disease (uMRD) in the vast majority of patients. On these grounds, a time-limited MRD-driven strategy, a previously unexplored scenario in CLL, is being attempted. On the other side of the spectrum, novel genetic and non-genetic mechanisms of resistance to targeted treatments are emerging. Here we review the response assessment criteria, the evolution and clinical application of MRD analysis and the mechanisms of resistance according to the novel treatment strategies within clinical trials. The extent to which this novel evidence will translate in the real-life management of CLL patients remains an open issue to be addressed.

Treatment Sequencing in Chronic Lymphocytic Leukemia in 2024: Where We Are and Where We Are Headed

As treatments with BTK inhibitors and BCL2 inhibitors have replaced the use of chemoimmunotherapy in CLL in both first-line and relapsed patients, it becomes critical to rationalize their use and exploit the full potential of each drug. Despite their proven, robust, and manifest efficacy, BTKis and BCL2is fail to provide long-term disease control in some categories of patients, and to date this is an unmet clinical need that is critical to recognize and address. Ongoing clinical trials are evaluating new treatment algorithms and new molecules to progressively thin this population. In this review for each category of patients we explicate the different possible patterns of treatment sequencing based on currently available evidence, starting from the frontline to currently ongoing trials, in order to optimize therapies as much as possible.

Chronic Lymphocytic Leukemia: Management of Adverse Events in the Era of Targeted Agents

The treatment landscape for CLL has undergone a profound transformation with the advent of targeted agents (TAs) like Bruton's Tyrosine Kinase inhibitors (BTKis) and BCL-2 inhibitors (BCL-2is). These agents target crucial cellular pathways in CLL, offering superior efficacy over traditional chemo-immunotherapy, which has led to improved progression-free and overall survival rates. This advancement promises enhanced disease control and potentially normal life expectancy for many patients. However, the journey is not without challenges, as these TAs are associated with a range of adverse events (AEs) that can impact treatment efficacy and patient quality of life. This review focuses on detailing the various AEs related to TA management in CLL, evaluating their frequency and clinical impact. The aim is to present a comprehensive guide to the effective management of these AEs, ensuring optimal tolerability and efficacy of TAs. By reviewing the existing literature and consolidating findings, we provide insights into AE management, which is crucial for maximizing patient outcomes in CLL therapy.

BTK inhibitors in CLL: second-generation drugs and beyond

ABSTRACT

BTK inhibitors (BTKis) are established standards of care in multiple B-cell malignancies including chronic lymphocytic leukemia, mantle cell lymphoma, and Waldenstrom macroglobulinemia. The first-generation BTKi ibrutinib demonstrated superiority over standard chemoimmunotherapy regimens in multiple randomized trials but is limited by cardiovascular side effects such as atrial fibrillation and hypertension. Second-generation BTKis have improved selectivity and demonstrate reduced rates of cardiovascular complications in 3 head-to-head ibrutinib studies. The emergence of BTK C481S mutation has led to the development of noncovalent, "reversible" BTKis, such as pirtobrutinib, which are agnostic to the C481S mutation. However, these inhibitors are associated with resistant mutations outside the C481 hot spot. These variant non-C481 mutations are of great clinical interest because some are shared among pirtobrutinib, zanubrutinib, and acalabrutinib, with potential implications for cross resistance and treatment sequencing. Finally, BTK protein degraders with in vitro activity against C481 and non-C481 mutations are currently in clinical development. Here, we review the evolution of therapeutic BTK-targeting and discuss future directions for clinical research.

Clinical pharmacokinetics and pharmacodynamics of venetoclax, a selective B-cell lymphoma-2 inhibitor

Venetoclax, a highly potent BCL-2 inhibitor, is indicated for treatment of some hematologic malignancies as monotherapy, and/or in combination with other agents. Venetoclax pharmacokinetics has been extensively characterized in patients and healthy participants. After oral dosing, the median time to reach maximum plasma concentration ranged from 5 to 8 h and harmonic mean half-life ranged from 14 to 18 h. Food increases venetoclax bioavailability by 3-5-fold and venetoclax should be administered with food to ensure adequate and consistent bioavailability. Venetoclax is eliminated via cytochrome P450 (CYP)3A metabolism, and a negligible amount of unchanged drug is excreted in urine. Strong CYP3A/P-glycoprotein inhibitors increased venetoclax exposures (AUC) by 1.44- to 6.90-fold while a significant decrease (71%) has been observed when dosed with strong CYP3 inducers. Venetoclax does not inhibit or induce CYP enzymes or transporters. Venetoclax pharmacokinetics is not appreciably altered by age, weight, sex, but the exposure is up to twofold higher in participants from Asian countries. Mild-to-severe renal impairment or end-stage renal disease do not alter venetoclax exposures, and venetoclax is not cleared by dialysis. Although mild-to-moderate hepatic impairment does not affect venetoclax exposures, twofold higher exposure was observed in subjects with severe hepatic impairment. Venetoclax exposure is comparable across patients with different hematologic malignancies and healthy participants. Overall, venetoclax exposure is only affected by food and CYP3A modulators and is only higher in Asian subjects and subjects with severe hepatic impairment. Venetoclax exposure-response relationships are malignancy-dependent and can be different between monotherapy and combination therapy.

Performance of a novel eight-color flow cytometry panel for measurable residual disease assessment of chronic lymphocytic leukemia

BACKGROUND

Measurable residual disease (MRD) is an important prognostic indicator of chronic lymphocytic leukemia (CLL). Different flow cytometric panels have been developed for the MRD assessment of CLL in Western countries; however, the application of these panels in China remains largely unexplored.

METHODS

Owing to the requirements for high accuracy, reproducibility, and comparability of MRD assessment in China, we investigated the performance of a flow cytometric approach (CD45-ROR1 panel) to assess MRD in patients with CLL. The European Research Initiative on CLL (ERIC) eight-color panel was used as the "gold standard."

RESULTS

The sensitivity, specificity, and concordance rate of the CD45-ROR1 panel in the MRD assessment of CLL were 100% (87/87), 88.5% (23/26), and 97.3% (110/113), respectively. Two of the three inconsistent samples were further verified using next-generation sequencing. In addition, the MRD results obtained from the CD45-ROR1 panel were positively associated with the ERIC eight-color panel results for MRD assessment (R = 0.98, p < 0.0001). MRD detection at low levels (≤1.0%) demonstrated a smaller difference between the two methods (bias, -0.11; 95% CI, -0.90 to 0.68) than that at high levels (>1%). In the reproducibility assessment, the bias was smaller at three data points (within 24, 48, and 72 h) in the CD45-ROR1 panel than in the ERIC eight-color panel. Moreover, MRD levels detected using the CD45-ROR1 panel for the same samples from different laboratories showed a strong statistical correlation (R = 0.99, p < 0.0001) with trivial interlaboratory variation (bias, 0.135; 95% CI, -0.439 to 0.709). In addition, the positivity rate of MRD in the bone marrow samples was higher than that in the peripheral blood samples.

CONCLUSIONS

Collectively, this study demonstrated that the CD45-ROR1 panel is a reliable method for MRD assessment of CLL with high sensitivity, reproducibility, and reliability.

Therapeutic targeting of apoptosis in chronic lymphocytic leukemia

Therapeutic targeting of apoptosis with small molecule B-cell lymphoma 2 (BCL-2) inhibition with venetoclax is highly efficacious in CLL, leading to sustained deep responses, particularly among patients with treatment-naïve disease with favorable prognostic markers. Patients with unfavorable genetic characteristics such as TP53 aberration and unmutated IGHV may also derive durable benefits, but their remission duration after time-limited venetoclax-containing combination therapy is shorter, particularly in patients with relapsed/refractory disease. Emerging data indicate that the context of disease progression after initial treatment with venetoclax may define the success of re-treatment with venetoclax. Specifically, continuous venetoclax exposure may select for resistant disease due to genetic mechanisms such as BCL2 mutations and functional resistance mechanisms such as hyperphosphorylation of BCL-2 family proteins, which decrease the affinity of venetoclax binding to the target or lead to increased MCL-1 dependence and concomitant decrease in BCL-2 dependence. These patients may be best served by switching to a different class of targeted agents at the time of progression. In contrast, relapsed CLL that arises while being off therapy after a period of time-limited venetoclax-based regimens maintains sensitivity to re-treatment with venetoclax for the majority of patients. Novel strategies related to therapeutic targeting of apoptosis include next-generation BCL-2 inhibitors with improved potency and pharmacokinetic profiles, direct targeting of anti-apoptotic BH3 family proteins beyond BCL-2 such as MCL-1, and indirect targeting of MCL-1 through mechanisms such as small molecule cyclin-dependent kinase 9 inhibitors.

Prognostication in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most common type of leukemia in Western countries. CLL is a highly heterogeneous disease: some patients may never require therapy and others relapse several times after different therapeutic strategies. Therefore, in CLL, prognostic markers are essential to capture high-risk patients for different clinical endpoints including early treatment requirement, early progression after BTK or BCL2 inhibitors and Richter transformation. In early stage CLL, different biological and clinical biomarkers have been identified to predict time to treatment requirement that could be used to identify the most appropriate population for early intervention clinical trial. However, at the moment, the standard of care for early stage CLL remains watch & wait since no survival benefit has been identified in clinical trials with chemoimmunotherapy and with BTK inhibitors. In patients requiring treatment TP53 disruptions identify high-risk patients who benefit the most from long-term continuous therapy with BTKi. On the opposite side of the spectrum, IGHV mutated patients devoid of TP53 disruption benefit the most from fixed-duration therapy with venetoclax-obinutuzumab. In between, the highly heterogenous subgroup of patients with IGHV unmutated genes represents the group in which further efforts are needed to identify additional prognostic biomarkers aimed at selecting patients who can benefit from fixed-duration and patients who can benefit from long term BTKi therapy. In the context of the aggressive transformation of CLL, namely Richter syndrome, the clonal relationship to the CLL counterpart represents the strongest prognostic biomarker. Clonally related Richter syndrome still represents an unmet clinical need which requires further efforts to identify new therapeutic strategies.

Innovative Combinations, Cellular Therapies and Bispecific Antibodies for Chronic Lymphocytic Leukemia: A Narrative Review

In the last few years, several agents targeting molecules that sustain the survival and the proliferation of chronic lymphocytic leukemia (CLL) cells have become clinically available. Most of these drugs target surface proteins, such as CD19 or CD20, via monoclonal or bispecific monoclonal antibodies (BsAbs), CAR T cells, intracellular proteins like BTK by using covalent or non-covalent inhibitors or BCL2 with first or second generation BH3-mimetics. Since the management of CLL is evolving quickly, in this review we highlighted the most important innovative treatments including novel double and triple combination therapies, CAR T cells and BsAbs for CLL. Recently, a large number of studies on novel combinations and newer strategic options for CLL therapy have been published or presented at international conferences, which were summarized and linked together. Although the management of treatment with a single continuous agent is easier, the emergence of protein mutations, long-term toxicities and costs are important concerns that favor the use of a fixed duration therapy. In the future, a measurable residual disease (MRD)-guided treatment cessation and MRD-based re-initiation of targeted therapy seems to be a more feasible approach, allowing identification of the patients who might benefit from continuous therapy or who might need a consolidation with BsAbs or CAR T cells to clear the neoplastic clone.

Taking the Next Step in Double Refractory Disease: Current and Future Treatment Strategies for Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is a monoclonal B-cell lymphoproliferative disease with a high annual incidence in Western countries. As B-cell receptor (BCR) signaling and intrinsic apoptotic resistance play critical roles in the development and survival of CLL cells, therapeutic approaches targeting these pathways have been extensively investigated to tackle this incurable disease. Over the last decade, several Phase 3 trials have confirmed the superior efficacy of covalent Bruton tyrosine kinase inhibitors (cBTKis) and venetoclax, a selective B-cell lymphoma 2 (BCL2) inhibitor, over chemoimmunotherapy. This has been demonstrated in both the treatment-naïve and relapsed/refractory (RR) settings and includes patients with high-risk molecular features. However, these drugs are not curative, with patients continuing to relapse after treatment with both cBTKis and BCL2is, and the optimal treatment strategy for these patients has not been defined. Several novel agents with distinct mechanisms have recently been developed for CLL which have demonstrated efficacy in patients who have previously received cBTKis and BCL2i. In particular, novel BCR-signaling targeting agents have shown promising efficacy in early-phase clinical trials for RR-CLL. Furthermore, cancer immunotherapies such as bispecific antibodies and chimeric antigen receptor T-cells have also shown anti-tumor activity in patients with heavily pretreated RR-CLL. Personalised approaches with these novel agents and combination strategies based on the understanding of resistance mechanisms have the potential to overcome the clinical challenge of what to do next for a patient who has already had a cBTKi and venetoclax.

Fixed-duration therapy comes of age in CLL: long-term results of MURANO and CLL14 trials

INTRODUCTION

Chronic lymphocytic leukemia (CLL) management has witnessed a transformative shift with the advent of time-limited venetoclax and anti-CD20 monoclonal antibody (mAb) regimens, as exemplified by the groundbreaking MURANO and CLL14 trials.

AREA COVERED

This article delves into the long-term follow-up data of fixed duration (FD) venetoclax combined with anti-CD20 mAb across various lines of CLL therapy. The data discussed here, not yet available in current literature, was unveiled at the 23rd European Hematological Association (EHA) congress held in Frankfurt in June 2023.

EXPERT OPINION

Combinations of venetoclax with anti-CD20 mAbs represent a compelling therapeutic option due to their finite treatment duration and remarkable achievement of undetectable minimal residual disease (uMRD). This not only ensures more enduring responses but also presents a manageable toxicity profile that suits a broad spectrum of CLL patients, including those who are elderly or less medically fit.Importantly, the integration of venetoclax/anti-CD20 mAb FD regimens may diminish the likelihood of CLL patients developing target mutations. This, in turn, enhances the potential for eliciting secondary clinical responses upon retreatment with venetoclax. Additionally, from an economic perspective, the cost-effectiveness of targeted therapy may further advocate for the selection of FD therapy as a frontrunner in CLL treatment.

Non-coding RNAs in disease: from mechanisms to therapeutics

Non-coding RNAs (ncRNAs) are a heterogeneous group of transcripts that, by definition, are not translated into proteins. Since their discovery, ncRNAs have emerged as important regulators of multiple biological functions across a range of cell types and tissues, and their dysregulation has been implicated in disease. Notably, much research has focused on the link between microRNAs (miRNAs) and human cancers, although other ncRNAs, such as long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs), are also emerging as relevant contributors to human disease. In this Review, we summarize our current understanding of the roles of miRNAs, lncRNAs and circRNAs in cancer and other major human diseases, notably cardiovascular, neurological and infectious diseases. Further, we discuss the potential use of ncRNAs as biomarkers of disease and as therapeutic targets.

Five-year follow-up of a phase 2 study of ibrutinib plus fludarabine, cyclophosphamide, and rituximab as initial therapy in CLL

ABSTRACT

We previously reported high rates of undetectable minimal residual disease <10-4 (uMRD4) with ibrutinib plus fludarabine, cyclophosphamide, and rituximab (iFCR) followed by 2-year ibrutinib maintenance (I-M) in treatment-naïve chronic lymphocytic leukemia (CLL). Here, we report updated data from this phase 2 study with a median follow-up of 63 months. Of 85 patients enrolled, including 5 (6%) with deletion 17p or TP53 mutation, 91% completed iFCR and 2-year I-M. Five-year progression-free survival (PFS) and overall survival were 94% (95% confidence interval [CI], 89%-100%) and 99% (95% CI, 96%-100%), respectively. No additional deaths have occurred with this extended follow-up. No difference in PFS was observed by immunoglobulin heavy-chain variable region gene status or duration of I-M. High rates of peripheral blood (PB) uMRD4 were maintained (72% at the end of iFCR, 66% at the end of 2-year I-M, and 44% at 4.5 years from treatment initiation). Thirteen patients developed MRD conversion without clinical progression, mostly (77%) after stopping ibrutinib. None had Bruton tyrosine kinase (BTK) mutations. One patient had PLCG2 mutation. Six of these patients underwent ibrutinib retreatment per protocol. Median time on ibrutinib retreatment was 34 months. The cumulative incidence of atrial fibrillation was 8%. Second malignancy or nonmalignant hematologic disease occurred in 13%, mostly nonmelanoma skin cancer. Overall, iFCR with 2-year I-M achieved durably deep responses in patients with diverse CLL genetic markers. Re-emergent clones lacked BTK mutation and retained sensitivity to ibrutinib upon retreatment. This trial is registered at www.clinicaltrials.gov as #NCT02251548.

Ibrutinib and venetoclax as primary therapy in symptomatic, treatment-naïve Waldenström macroglobulinemia

ABSTRACT

Concurrent Bruton tyrosine kinase and BCL2 inhibition has not yet been investigated in Waldenström macroglobulinemia (WM). We performed an investigator-initiated trial of ibrutinib and venetoclax in symptomatic treatment-naïve patients with MYD88-mutated WM. Patients received ibrutinib 420 mg once daily (cycle 1), followed by a ramp-up of venetoclax to 400 mg daily (cycle 2). The combination was then administered for 22 additional 4-week cycles. The attainment of very good partial response (VGPR) was the primary end point. Forty-five patients were enrolled in this study. The median baseline characteristics were as follows: age 67 years, serum IgM 43 g/L, and hemoglobin 102 g/L. Seventeen patients (38%) carried CXCR4 mutations. Nineteen patients (42%) achieved VGPR. Grade 3 or higher adverse events included neutropenia (38%), mucositis (9%), and tumor lysis syndrome (7%). Atrial fibrillation occurred in 3 (9%), and ventricular arrhythmia in 4 (9%) patients that included 2 grade 5 events. With a median follow-up of 24.4 months, the 24-month progression-free survival (PFS) and overall survival (OS) rates were 76% and 96%, respectively, and were not impacted by CXCR4 mutations. The median time on therapy was 10.2 months, and the median time after the end of therapy (EOT) was 13.3 months. Eleven of the 12 progression events occurred after EOT, and the 12-month PFS rates after EOT were 79%; 93% if VGPR was attained, and 69% for other patients (P = .12). Ibrutinib and venetoclax induced high VGPR rates and durable responses after EOT, although they were associated with a higher-than-expected rate of ventricular arrhythmia in patients with WM, leading to early study treatment termination. This trial was registered at www.clinicaltrials.gov as #NCT04273139.

Chronic Lymphocytic Leukemia: Time-Limited Therapy in the First-Line Setting and Role of Minimal Residual Disease

PURPOSE OF REVIEW

In this review, we provide an overview of different time-limited combination therapies of chronic lymphocytic leukemia (CLL) and summarize the data of pivotal clinical studies. Furthermore, we discuss the relevance of MRD in clinical trials and summarize the challenges that arise in routine clinical care. Finally, we provide an outlook on studies and datasets needed to optimize the use of time-limited treatment strategies and MRD assessments in modern CLL management.

RECENT FINDINGS

In recent years, first-line treatment of CLL has undergone a considerable transformation, with targeted substances having largely replaced chemoimmunotherapy (CIT) as a time-limited strategy in the frontline setting. BTK inhibitors were the first class of targeted agents introduced in CLL, which achieved longer progression-free survival (PFS) and in some cases also overall survival (OS) than CIT. However, this required an indefinite drug intake until disease progression, while CIT is generally administered over the course of few months. In contrast to BTK inhibitors, BCL2 inhibitors, another class of targeted agents, can achieve high rates of undetectable minimal residual disease (uMRD) levels and induce deep molecular remissions with the potential to stop treatment while maintaining remissions. Combinations of BCL2 inhibitors with CD20 antibodies or with BTK inhibitors have been explored to establish time-limited treatment strategies with targeted agents. In this context, one of the strongest predictors of long-term outcomes is MRD status at the end of treatment, which has been shown to correlate closely with PFS and OS in most cases.

Overcoming Resistance in Chronic Lymphocytic Leukemia-Maybe Less Is More?

Acquired mutations in BTK, PLCG2, and BCL2 are associated with resistance to continuous targeted agent therapy in chronic lymphocytic leukemia (CLL). Here, we discuss new evidence that limiting the duration of CLL therapy may prevent the evolution of such resistance mutations, potentially facilitating effective retreatment strategies. See related article by Jain et al., p. 498.

Phase 2 study of ibrutinib plus venetoclax in Japanese patients with relapsed/refractory mantle cell lymphoma

BACKGROUND

Despite high response rates to initial therapy, most patients with mantle cell lymphoma (MCL) experience relapsed or refractory (R/R) disease. Here, we report the efficacy, safety, and pharmacokinetics of the Phase 2, single-arm M20-075 study (NCT04477486) of ibrutinib and venetoclax combination therapy in Japanese patients with R/R MCL.

METHODS

Patients received 560 mg ibrutinib and 400 mg venetoclax (after a 5-week ramp-up from 20 mg) once daily for up to 104 weeks. Primary endpoint was complete response (CR) rate by independent review committee (IRC). Secondary endpoints included overall response rate (ORR), duration of response (DOR), undetectable minimal residual disease (uMRD) rate, progression-free survival (PFS), overall survival (OS), safety including dose-limiting toxicity (DLT) assessment in the first six patients, and pharmacokinetic parameters. Full analysis set (FAS) comprised all treated patients. Per protocol set (PPS) excluded treated patients with non-evaluable disease at baseline by IRC.

RESULTS

Thirteen patients were treated (FAS n = 13; PPS, n = 12). Median age was 71 years, patients had a median of two prior treatments. After a median follow-up of 9.6 months, IRC-assessed CR rate and ORR were both 83% (PPS). All six MRD-evaluable patients had uMRD. Median DOR, PFS, and OS were unreached. The most common Grade ≥ 3 treatment-emergent adverse event (TEAE) was neutropenia (23%); 1 patient discontinued due to squamous cell carcinoma of the lung. No DLTs, tumor lysis syndrome, or deaths related to TEAEs were observed.

CONCLUSION

Ibrutinib plus venetoclax exhibited high response rates and a well-tolerated safety profile in Japanese patients with R/R MCL.

Absence of BTK, BCL2, and PLCG2 Mutations in Chronic Lymphocytic Leukemia Relapsing after First-Line Treatment with Fixed-Duration Ibrutinib plus Venetoclax

PURPOSE

Mutations in BTK, PLCG2, and BCL2 have been reported in patients with progressive disease (PD) on continuous single-agent BTK or BCL2 inhibitor treatment. We tested for these mutations in samples from patients with PD after completion of first-line treatment with fixed-duration ibrutinib plus venetoclax for chronic lymphocytic leukemia (CLL) in the phase II CAPTIVATE study.

PATIENTS AND METHODS

A total of 191 patients completed fixed-duration ibrutinib plus venetoclax (three cycles of ibrutinib then 12-13 cycles of ibrutinib plus venetoclax). Genomic risk features [del(11q), del(13q), del(17p), trisomy 12, complex karyotype, unmutated IGHV, TP53 mutated] and mutations in genes recurrently mutated in CLL (ATM, BIRC3, BRAF, CHD2, EZH2, FBXW7, MYD88, NOTCH1, POT1, RPS15, SF3B1, XPO1) were assessed at baseline in patients with and without PD at data cutoff; gene variants and resistance-associated mutations in BTK, PLCG2, or BCL2 were evaluated at PD.

RESULTS

Of 191 patients completing fixed-duration ibrutinib plus venetoclax, with median follow-up of 38.9 months, 29 (15%) developed PD. No baseline risk feature or gene mutation was significantly associated with development of PD. No previously reported resistance-associated mutations in BTK, PLCG2, or BCL2 were detected at PD in 25 patients with available samples. Of the 29 patients with PD, 19 have required retreatment (single-agent ibrutinib, n = 16, or ibrutinib plus venetoclax, n = 3); 17 achieved partial response or better, 1 achieved stable disease, and 1 is pending response assessment.

CONCLUSIONS

First-line fixed-duration combination treatment with ibrutinib plus venetoclax may mitigate development of resistance mechanisms associated with continuous single-agent targeted therapies, allowing for effective retreatment. See related commentary by Al-Sawaf and Davids, p. 471.

Treatment of Double-Refractory Chronic Lymphocytic Leukemia-An Unmet Clinical Need

Recent years have seen significant improvement in chronic lymphocytic leukemia (CLL) management. Targeting B-cell lymphoma (BCL-2) and Bruton's kinase (BTK) have become the main strategies to restrain CLL activity. These agents are generally well tolerated, but the discontinuation of these therapies happens due to resistance, adverse effects, and Richter's transformation. A growing population of patients who have previously used both BTK inhibitors and BCL2 suffer from the constriction of the following regimens. This review explores the resistance mechanisms for both ibrutinib and venetoclax. Moreover, we present innovative approaches evaluated for treating double-refractory CLL.

Chronic Lymphocytic Leukemia Therapy Guided by Measurable Residual Disease

BACKGROUND

The combination of ibrutinib and venetoclax has been shown to improve outcomes in patients with chronic lymphocytic leukemia (CLL) as compared with chemoimmunotherapy. Whether ibrutinib-venetoclax and personalization of treatment duration according to measurable residual disease (MRD) is more effective than fludarabine-cyclophosphamide-rituximab (FCR) is unclear.

METHODS

In this phase 3, multicenter, randomized, controlled, open-label platform trial involving patients with untreated CLL, we compared ibrutinib-venetoclax and ibrutinib monotherapy with FCR. In the ibrutinib-venetoclax group, after 2 months of ibrutinib, venetoclax was added for up to 6 years of therapy. The duration of ibrutinib-venetoclax therapy was defined by MRD assessed in peripheral blood and bone marrow and was double the time taken to achieve undetectable MRD. The primary end point was progression-free survival in the ibrutinib-venetoclax group as compared with the FCR group, results that are reported here. Key secondary end points were overall survival, response, MRD, and safety.

RESULTS

A total of 523 patients were randomly assigned to the ibrutinib-venetoclax group or the FCR group. At a median of 43.7 months, disease progression or death had occurred in 12 patients in the ibrutinib-venetoclax group and 75 patients in the FCR group (hazard ratio, 0.13; 95% confidence interval [CI], 0.07 to 0.24; P<0.001). Death occurred in 9 patients in the ibrutinib-venetoclax group and 25 patients in the FCR group (hazard ratio, 0.31; 95% CI, 0.15 to 0.67). At 3 years, 58.0% of the patients in the ibrutinib-venetoclax group had stopped therapy owing to undetectable MRD. After 5 years of ibrutinib-venetoclax therapy, 65.9% of the patients had undetectable MRD in the bone marrow and 92.7% had undetectable MRD in the peripheral blood. The risk of infection was similar in the ibrutinib-venetoclax group and the FCR group. The percentage of patients with cardiac serious adverse events was higher in the ibrutinib-venetoclax group than in the FCR group (10.7% vs. 0.4%).

CONCLUSIONS

MRD-directed ibrutinib-venetoclax improved progression-free survival as compared with FCR, and results for overall survival also favored ibrutinib-venetoclax. (Funded by Cancer Research UK and others; FLAIR ISRCTN Registry number, ISRCTN01844152; EudraCT number, 2013-001944-76.).

First-in-Human Study of the Reversible BTK Inhibitor Nemtabrutinib in Patients with Relapsed/Refractory Chronic Lymphocytic Leukemia and B-Cell Non-Hodgkin Lymphoma

Nemtabrutinib is an orally bioavailable, reversible inhibitor of Bruton tyrosine kinase (BTK) and C481S mutant BTK. We evaluated the safety, pharmacology, and antitumor activity of nemtabrutinib in relapsed/refractory hematologic malignancies. Forty-eight patients with chronic lymphocytic leukemia (CLL), B-cell non-Hodgkin lymphoma (NHL), or Waldenström macroglobulinemia (WM), relapsed/refractory after ≥2 prior therapies were enrolled in the open-label, single-arm, phase I MK-1026-001 study (NCT03162536) to receive nemtabrutinib 5 to 75 mg once daily in 28-day cycles. Dose finding progressed using a 3 + 3 dose escalation design. Primary endpoints were safety and the recommended phase II dose (RP2D). Among 47 treated patients, 29 had CLL, 17 had NHL, and 1 had WM. Grade ≥3 treatment-emergent adverse events occurred in 37 (89%), most commonly neutropenia (11; 23.4%), febrile neutropenia (7; 14.9%), and pneumonia (7; 14.9%). The RP2D was 65 mg daily. An overall response rate of 75% was observed in patients with CLL at 65 mg daily.

SIGNIFICANCE

This first-in-human phase I study demonstrates the safety and preliminary efficacy of nemtabrutinib in patients with relapsed/refractory B-cell malignancies. These data support further exploration of nemtabrutinib in larger clinical studies. This article is featured in Selected Articles from This Issue, p. 5.

Targeting TP53 disruption in chronic lymphocytic leukemia: Current strategies and future directions

In the modern era of Chronic Lymphocytic Leukemia (CLL) targeted therapy, the loss of p53 function due to genetic abnormalities remains a significant challenge. This is because even targeted agents, which are currently the mainstay of treatment for CLL, do not directly target p53 or restore its disrupted pathway. Consequently, resistance to therapy and unfavorable clinical outcomes often accompany these p53-related abnormalities. An essential goal of future clinical research should be to address the ostensibly "undruggable" p53 pathway. Currently, multiple therapeutic approaches are being explored to tackle TP53 dysfunction and improve outcomes in high-risk CLL. These approaches include the use of oncoprotein murine double minute 2 inhibitors, small-molecule p53 reactivators, exportin 1 (XPO1) inhibitors, and ataxia-telangiectasia mutated and Rad3-related (ATR) inhibitors. Combinations of these p53-targeting strategies, along with established novel therapies such as B-cell receptor or B-cell lymphoma-2 (BCL-2) inhibitors, may shape the future of therapeutic trials in this challenging-to-treat disease.

Treatment of Chronic Lymphocytic Leukemia in the Personalized Medicine Era

Chronic lymphocytic leukemia is a lymphoproliferative disorder marked by the expansion of monoclonal, mature CD5+CD23+ B cells in peripheral blood, secondary lymphoid tissues, and bone marrow. The disease exhibits significant heterogeneity, with numerous somatic genetic alterations identified in the neoplastic clone, notably mutated TP53 and immunoglobulin heavy chain mutational statuses. Recent studies emphasize the pivotal roles of genetics and patient fragility in treatment decisions. This complexity underscores the need for a personalized approach, tailoring interventions to individual genetic profiles for heightened efficacy. The era of personalized treatment in CLL signifies a transformative shift, holding the potential for improved outcomes in the conquest of this intricate hematologic disorder. This review plays a role in elucidating the evolving CLL treatment landscape, encompassing all reported genetic factors. Through a comprehensive historical analysis, it provides insights into the evolution of CLL management. Beyond its retrospective nature, this review could be a valuable resource for clinicians, researchers, and stakeholders, offering a window into the latest advancements. In essence, it serves as a dynamic exploration of our current position and the promising prospects on the horizon.

MRD-directed therapy in CLL: ready for prime time?

In recent years, the treatment paradigm for patients with chronic lymphocytic leukemia (CLL) has moved away from chemoimmunotherapy (CIT) toward the use of novel targeted agents. Commercially available drugs, including Bruton's tyrosine kinase inhibitors and the BCL2 inhibitor venetoclax, often used in combination with anti-CD20 monoclonal antibodies, are now the mainstay of therapy both in the frontline and in relapsed settings. As the landscape for CLL management evolves, therapeutic endpoints need to be redefined. Detection of measurable residual disease (MRD) is a sensitive tool to identify disease burden following treatment with several therapeutic regimens in CLL (including CIT, venetoclax-based regimens, and cellular therapies), and it has demonstrated prognostic value. Despite recent advances, the utility of MRD-directed therapy and attempts to eradicate it in routine clinical practice remain debated. There is little comparative data from clinical trials on the best assay to determine undetectable MRD (U-MRD) and whether its monitoring can lead to changes in treatment strategies. Our review discusses the definitions of MRD, assays for its detection, and its impact on long-term survival outcomes for patients with a CLL diagnosis.