Chemotherapy-free frontline therapy for CLL: is it worth it?

Discovery of the Clinical Candidate Sonrotoclax (BGB-11417), a Highly Potent and Selective Inhibitor for Both WT and G101V Mutant Bcl-2

The approval of venetoclax, a B-cell lymphoma-2 (Bcl-2) selective inhibitor, for the treatment of chronic lymphocytic leukemia demonstrated that the antiapoptotic protein Bcl-2 is a druggable target for B-cell malignancies. However, venetoclax's limited potency cannot produce a strong, durable clinical benefit in other Bcl-2-mediated malignancies (e.g., diffuse large B-cell lymphomas) and multiple recurrent Bcl-2 mutations (e.g., G101V) have been reported to mediate resistance to venetoclax after long-term treatment. Herein, we described novel Bcl-2 inhibitors with increased potency for both wild-type (WT) and mutant Bcl-2. Comprehensive structure optimization led to the clinical candidate BGB-11417 (compound 12e, sonrotoclax), which exhibits strong in vitro and in vivo inhibitory activity against both WT Bcl-2 and the G101V mutant, as well as excellent selectivity over Bcl-xL without obvious cytochrome P450 inhibition. Currently, BGB-11417 is undergoing phase II/III clinical assessments as monotherapy and combination treatment.

CTP Synthase 1 Is a Novel Therapeutic Target in Lymphoma

Lymphoma is the most common hematological malignancy and is among the 10 most prevalent cancers worldwide. Although survival has been improved by modern immunochemotherapeutic regimens, there remains a significant need for novel targeted agents to treat both B-cell and T-cell malignancies. Cytidine triphosphate synthase 1 (CTPS1), which catalyzes the rate-limiting step in pyrimidine synthesis, plays an essential and nonredundant role in B-cell and T-cell proliferation but is complemented by the homologous CTPS2 isoform outside the hemopoietic system. This report describes the identification and characterization of CTPS1 as a novel target in B- and T-cell cancers. A series of small molecules have been developed which show potent and highly selective inhibition of CTPS1. Site-directed mutagenesis studies identified the adenosine triphosphate pocket of CTPS1 as the binding site for this small molecule series. In preclinical studies, a potent and highly selective small molecule inhibitor of CTPS1 blocked the in vitro proliferation of human neoplastic cells, showing the highest potency against lymphoid neoplasms. Importantly, pharmacological CTPS1 inhibition induced cell death by apoptosis in the majority of lymphoid cell lines tested, thus demonstrating a cytotoxic mechanism of action. Selective CTPS1 inhibition also inhibited the growth of neoplastic human B- and T- cells in vivo. These findings identify CTPS1 as a novel therapeutic target in lymphoid malignancy. A compound from this series is in phase 1/2 clinical studies for the treatment of relapsed/refractory B- and T-cell lymphoma (NCT05463263).

A real-world study to assess the association of cardiovascular adverse events (CVAEs) with ibrutinib as first-line (1L) treatment for patients with chronic lymphocytic leukaemia (CLL) in the United States

Ibrutinib, a Bruton's tyrosine kinase inhibitor, is often used as first-line (1L) treatment of chronic lymphocytic leukaemia (CLL); however, it is associated with an increased risk for cardiovascular adverse events (CVAEs). This real-world study adds to existing literature by simultaneously investigating the correlation between pre-existing CV risk factors and the relative cardiotoxicity of ibrutinib vs other therapies in CLL/small lymphocytic lymphoma (SLL). Using a real-world database, the risk of subsequent CVAEs (any CVAE, atrial fibrillation [AF], or hypertension) were compared among patients who received 1L ibrutinib monotherapy or another type of non-ibrutinib therapy, grouped as intensive (IT) or non-intensive therapy (NIT). Each patient's baseline CV risk was estimated using the Framingham risk score. Inverse probability treatment weighting was incorporated into a logistic regression model to reduce baseline imbalance. Results showed ibrutinib was significantly associated with higher risk of CVAEs regardless of baseline CV risk. Compared with IT, odds ratios of any CVAE, hypertension, or AF were 2.61, 3.66, and 3.02, respectively vs 1.88, 2.13, and 2.46, respectively, with NIT. Sensitivity analyses confirmed the findings were robust. These results suggest clinical caution should be taken when selecting ibrutinib for patients with CLL/SLL, especially in those with high baseline CV risk.

Outcomes for Patients With Chronic Lymphocytic Leukemia (CLL) Previously Treated With Both a Covalent BTK and BCL2 Inhibitor in the United States: A Real-World Database Study

PURPOSE

This study describes the treatment patterns and outcomes of patients with CLL/SLL in a de-identified real-world oncology electronic health records database.

METHODS

Adult patients with CLL/SLL were eligible if they had received cBTKi therapy, both a cBTKi and a BCL2i, or all 4 drug classes (cBTKi, BCL2i, rituximab, and chemotherapy) at any time during the first 5 lines of therapy. Time-to-event outcomes were evaluated using Kaplan Meier method. No statistical comparisons were conducted; all analyses were descriptive and conducted using SAS Enterprise.

RESULTS

A total of 9578 patients were eligible: 52.0% (n = 4983) received at least one cBTKi, 6.1% (n = 581) received both a cBTKi and BCL2i, and 2.3% (n = 218) received all four therapies (cBTKi, BCL2i, rituximab, and chemotherapy). Of those who discontinued these treatments, only 39.5% (n = 1 206/3 577), 59.7% (n = 228/382), and 55.0% (n = 82/149) received subsequent therapy (post-cBTKi, post-cBTKi/post-BCL2i, and post-all 4 therapies, respectively). Median time from treatment discontinuation of these therapies to the discontinuation of subsequent therapy or death was 9.5 months (all patients who discontinued the cBTKi) 5.6 months (those who discontinued both a cBTKi and BCL2i) and 3.9 months (patients who discontinued all four therapies). The median duration of the next treatment among those who received additional therapy was post-cBTKi treatment duration = 4.1 months; post-cBTKi/post-BCL2i treatment duration = 5.5 months; and median duration of the immediate next therapy after discontinuation of all 4 therapies = 5.1 months.

CONCLUSIONS

The poor outcomes observed across cohorts in this study demonstrate the need for effective treatments that can improve outcomes in patients with CLL/SLL.

Ibrutinib Does Not Impact CCR7-Mediated Homeostatic Migration in T-Cells from Chronic Lymphocytic Leukemia Patients

Bruton's tyrosine kinase inhibitor ibrutinib has significantly changed treatment landscape in chronic lymphocytic leukemia (CLL). Growing evidence supports ibrutinib to work beyond the effect on tumor cells by means of, for example, restoring functionality of the T-cell compartment and increasing circulating T-cell numbers. Recent evidence suggests T-cell enhanced expansion, rather than increased egress from secondary lymphoid organs (SLO), as a root cause for ibrutinib-induced lymphocytosis. However, whether the latter physiological change is also a consequence of a forced retention in blood remains undisclosed. Since CCR7 is the main chemokine receptor taking over the homing of T-cells from peripheral compartments to lymph nodes and other SLO, we aimed to investigate the impact of ibrutinib on CCR7 functionality in T-cells. To this end, we documented receptor expression in T-cells from a large cohort of ibrutinib-treated CLL patients, and performed different in vivo and in vitro migration models. Overall, our data confirm that CCR7 expression or receptor-mediated migration in CLL T-cells is not affected by ibrutinib. Furthermore, it does not modulate CCR7-driven homing nor nodal interstitial migration. Together, our results support that ibrutinib-induced CLL T-cell accumulation in the blood stream is not derived from an impairment of CCR7-driven recirculation between the SLO and bloodstream, and therefore T-cell expansion is the most plausible cause.

International validation of the EORTC QLQ-CLL17 questionnaire for assessment of health-related quality of life for patients with chronic lymphocytic leukaemia

Selecting the most appropriate chronic lymphocytic leukaemia (CLL) treatment is challenging. Patient-reported health-related quality of life (HRQoL) is therefore a critical aspect to consider. This international study by the European Organization for Research and Treatment of Cancer (EORTC) tested the psychometric properties of a newly developed measure for CLL patients: the EORTC QLQ-CLL17 to supplement the core questionnaire (EORTC QLQ-C30). Patients with CLL (n = 341) from 12 countries completed the QLQ-C30, QLQ-CLL17 and a debriefing questionnaire. Sociodemographic and clinical data were recorded from medical records. A high percentage (30%-66%) reported symptoms and/or worries (e.g. aches/pains in muscles, lack of energy and worry/fears about health). Confirmatory factor analysis showed an acceptable to good fit of the 17 items on the three scales (i.e. symptom burden, physical condition/fatigue and worries/fears about health and functioning). Completion took on average 8 min. Test-retest and convergent validity was demonstrated. The QLQ-CLL17 differentiated between patients with an Eastern Cooperative Oncology group (ECOG) performance of 0 versus 1-3 (p's < 0.01 and clinically relevant). The newly developed EORTC QLQ-CLL17 will increase sensitivity of HRQoL assessment in patients with CLL. Implementation of this questionnaire both in clinical research and practice will help to generate unique clinically relevant data to better inform CLL treatment decision-making.

Clinical Trials of the BTK Inhibitors Ibrutinib and Acalabrutinib in Human Diseases Beyond B Cell Malignancies

The BTK inhibitors ibrutinib and acalabrutinib are FDA-approved drugs for the treatment of B cell malignances. Both drugs have demonstrated clinical efficacy and safety profiles superior to chemoimmunotherapy regimens in patients with chronic lymphocytic leukemia. Mounting preclinical and clinical evidence indicates that both ibrutinib and acalabrutinib are versatile and have direct effects on many immune cell subsets as well as other cell types beyond B cells. The versatility and immunomodulatory effects of both drugs have been exploited to expand their therapeutic potential in a wide variety of human diseases. Over 470 clinical trials are currently registered at ClinicalTrials.gov to test the efficacy of ibrutinib or acalabrutinib not only in almost every type of B cell malignancies, but also in hematological malignancies of myeloid cells and T cells, solid tumors, chronic graft versus host disease (cGHVD), autoimmune diseases, allergy and COVID-19 (http:www.clinicaltrials.gov). In this review, we present brief discussions of the clinical trials and relevant key preclinical evidence of ibrutinib and acalabrutinib as monotherapies or as part of combination therapies for the treatment of human diseases beyond B cell malignancies. Adding to the proven efficacy of ibrutinib for cGVHD, preliminary results of clinical trials have shown promising efficacy of ibrutinib or acalabrutinib for certain T cell malignancies, allergies and severe COVID-19. However, both BTK inhibitors have no or limited efficacy for refractory or recurrent solid tumors. These clinical data together with additional pending results from ongoing trials will provide valuable information to guide the design and improvement of future trials, including optimization of combination regimens and dosing sequences as well as better patient stratification and more efficient delivery strategies. Such information will further advance the precise implementation of BTK inhibitors into the clinical toolbox for the treatment of different human diseases.

Multifaceted Immunomodulatory Effects of the BTK Inhibitors Ibrutinib and Acalabrutinib on Different Immune Cell Subsets - Beyond B Lymphocytes

The clinical success of the two BTK inhibitors, ibrutinib and acalabrutinib, represents a major breakthrough in the treatment of chronic lymphocytic leukemia (CLL) and has also revolutionized the treatment options for other B cell malignancies. Increasing evidence indicates that in addition to their direct effects on B lymphocytes, both BTK inhibitors also directly impact the homeostasis, phenotype and function of many other cell subsets of the immune system, which contribute to their high efficacy as well as adverse effects observed in CLL patients. In this review, we attempt to provide an overview on the overlapping and differential effects of ibrutinib and acalabrutinib on specific receptor signaling pathways in different immune cell subsets other than B cells, including T cells, NK cells, monocytes, macrophages, granulocytes, myeloid-derived suppressor cells, dendritic cells, osteoclasts, mast cells and platelets. The shared and distinct effects of ibrutinib versus acalabrutinib are mediated through BTK-dependent and BTK-independent mechanisms, respectively. Such immunomodulatory effects of the two drugs have fueled myriad explorations of their repurposing opportunities for the treatment of a wide variety of other human diseases involving immune dysregulation.

Time-limited, Combined Regimen in Chronic Lymphocytic Leukemia: A Promising Strategy to Achieve a Drug Holiday

Chemoimmunotherapy (CIT) is defined as standard first line treatment for chronic lymphocytic leukemia (CLL) patients while patients with unfavorable biological characteristics such as unmutated immunoglobulin heavy chain (UM-IGHV) and TP53 aberration failed to benefit from it. The emergency of the small molecular targeted agents including Bruton's tyrosine kinase (BTK) inhibitor (BTKi) leads to a brand-new era, from a CIT to a chemo-free era in CLL. However, the treatment of target agents is not enough to attain a deep remission and high rate of complete remission (CR), especially in patients with high risks. The long duration brought about problems, such as cost, drug resistance and toxicity. To benefit CLL in progression free survival (PFS) and long-term remission, exploration of time-limited therapies, mainly with BTKi plus CIT and BCL2i based combination therapy has become a mainstream in clinical trials. The time-limited combination therapy shed light on the promising potentiality to attain sustainable deep remission and partly overcame the risk factors, although long term follow-up is required to consolidate the conclusion. In this review, we intend to introduce key results of clinical trials with combination therapy, discuss the achievements and limitations and put forward future direction for clinical trial design in this field.

Chemoimmunotherapy in the First-Line Treatment of Chronic Lymphocytic Leukaemia: Dead Yet, or Alive and Kicking?

The paradigm of first-line treatment of chronic lymphocytic leukaemia (CLL) is currently undergoing a radical change. On the basis of several randomised phase III trials showing prolongation of progression-free survival, chemoimmunotherapy is being replaced by treatment based on novel, orally available targeted inhibitors such as Bruton tyrosine kinase inhibitors ibrutinib and acalabrutinib or bcl-2 inhibitor venetoclax. However, the use of these agents may be associated with other disadvantages. First, with the exception of one trial in younger/fit patients, no studies have so far demonstrated benefit regarding the ultimate endpoint of overall survival. Second, oral inhibitors are extremely expensive and thus currently unavailable due to the absence of reimbursement in some countries. Third, treatment with ibrutinib and acalabrutinib necessitates long-term administration until progression; this may be associated with accumulation of late side effects, problems with patient compliance, and selection of resistant clones. Therefore, the identification of a subset of patients who could benefit from chemoimmunotherapy would be ideal. Current data suggest that patients with the mutated variable region of the immunoglobulin heavy chain (IGHV) achieve fairly durable remissions, especially when treated with fludarabine, cyclophosphamide, and rituximab (FCR) regimen. This review discusses current options for treatment-naïve patients with CLL.