Venetoclax-Rituximab in Relapsed or Refractory Chronic Lymphocytic Leukemia

Targeting p53 in chronic lymphocytic leukemia

INTRODUCTION

Genomic studies have allowed to identify molecular predictors for chronic lymphocytic leukemia (CLL) treatment tailoring. TP53 disruption is the strongest predictor of chemo-refractoriness and its assessment is the first decisional node in the disease treatment algorithm.

AREAS COVERED

The review covers the p53 biological pathway, its genetic alterations and clinical implications in CLL, and its druggable targets. The potential therapeutic options for TP53 disrupted patients are described, including: i) agents circumventing TP53 disruption; ii) targeted therapies restoring the physiological function of mutant p53; and iii) medicines potentiating p53 function.

EXPERT OPINION

The key approach to improve CLL outcome is treatment tailoring in individual patients. BCR and BCL2 inhibitors have significantly improved CLL survival, however TP53 disrupted patients still have a less favorable outcome than wild type cases, possibly because these novel drugs do not directly target p53 and do not restore the function of the disrupted p53 pathway. Emerging innovative molecules in cancer are able to restore the p53 mutant protein and/or potentiate the activity of the p53 wild type protein. If these compounds were confirmed as efficacious also for CLL, they would represent another step forward in the care of high risk CLL patients with TP53 abnormalities.

An update of venetoclax and obinutuzumab in chronic lymphocytic leukemia

In the last decade, the treatment of chronic lymphocytic leukemia (CLL) has shifted away from chemoimmunotherapy toward targeted novel agents such as small molecule inhibitors and antibodies. Here, we give an overview of the pharmacology of venetoclax and obinutuzumab and the evidence from early phase to Phase III trials that have shaped how they are used in the treatment of CLL. Venetoclax, an oral anti-apoptotic BCL-2 inhibitor, in combination with a CD20 antibody has shown superiority to chemoimmunotherapy in treatment-naive and relapsed/refractory CLL. Obinutuzumab is a novel anti-CD20 monoclonal antibody that has been safely combined with novel agents including venetoclax and Bruton tyrosine kinase inhibitors and has shown superiority over rituximab when combined with chlorambucil.

Protocol description of the HOVON 141/VISION trial: a prospective, multicentre, randomised phase II trial of ibrutinib plus venetoclax in patients with creatinine clearance ≥30 mL/min who have relapsed or refractory chronic lymphocytic leukaemia (RR-CLL) with or without TP53 aberrations

INTRODUCTION

Literature is scarce on the combination treatment of ibrutinib and venetoclax (IV) is scarce in relapsed or refractory chronic lymphocytic leukaemia (RR-CLL). Especially, the possibility of stopping ibrutinib in RR-CLL patients in deep remission is unclear.

METHODS AND ANALYSIS

In the HOVON 141/VISION trial, patients with RR-CLL are treated with 12 cycles of IV after a short induction with ibrutinib. Patients reaching undetectable minimal residual disease (uMRD) after 12 cycles of IV are randomised 1:2 to continue ibrutinib or stop treatment. The persistence of uMRD after stopping IV is studied. In addition, in patients who become positive for MRD again after stopping, IV treatment is reinitiated. The efficacy of this approach with regard to progression-free survival 12 months after randomisation is the primary endpoint of the study.

ETHICS AND DISSEMINATION

This protocol respects the Helsinki declaration and has been approved by the ethical committee of the Amsterdam Medical Center. Study findings will be disseminated through peer-reviewed papers. All patients who fulfil the inclusion criteria and no-exclusion criteria, and have signed the informed consent form are included in the study.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov Registry (NCT03226301).

Prevention and Treatment of Tumor Lysis Syndrome in the Era of Onco-Nephrology Progress

Background: Tumor lysis syndrome (TLS) is an oncologic emergency due to a rapid break down of malignant cells usually induced by cytotoxic therapy, with hyperuricemia, hyperkalemia, hyperphosphatemia, hypocalcemia, and serious clinical consequences such as acute renal injury, cardiac arrhythmia, hypotension, and death. Rapidly expanding knowledge of cancer immune evasion mechanisms and host-tumor interactions has significantly changed our therapeutic strategies in hemato-oncology what resulted in the expanding spectrum of neoplasms with a risk of TLS. Summary: Since clinical TLS is a life-threatening condition, identifying patients with risk factors for TLS development and implementation of adequate preventive measures remains the most critical component of its medical management. In general, these consist of vigilant laboratory and clinical monitoring, vigorous IV hydration, urate-lowering therapy, avoidance of exogenous potassium, use of phosphate binders, and – in high-risk cases – considering cytoreduction before the start of the aggressive agent or a gradual escalation of its dose. Key Messages: In patients with a high risk of TLS, cytotoxic chemotherapy should be given in the facility with ready access to dialysis and a treatment plan discussed with the nephrology team. In the case of hyperkalemia, severe hyperphosphatemia or acidosis, and fluid overload unresponsive to diuretic therapy, the early renal replacement therapy (RRT) should be considered. One must remember that in TLS, the threshold for RRT initiation may be lower than in other clinical situations since the process of cell breakdown is ongoing, and rapid increases in serum electrolytes cannot be predicted.

Neutralization of B-Cell Activating Factor (BAFF) by Belimumab Reinforces Small Molecule Inhibitor Treatment in Chronic Lymphocytic Leukemia

Simple Summary

Chronic lymphocytic leukemia (CLL) is the most common form of leukemia in Western countries. Despite the substantial progress achieved by the recent introduction of the novel small molecule inhibitors idelalisib, ibrutinib and venetoclax in CLL treatment, therapy resistance occurs frequently and the disease so far remains incurable. In the present study we report that BAFF, a member of the TNF protein family, protects CLL cells from treatment-induced cell death. In turn, the therapeutic effects of idelalisib, ibrutinib and venetoclax can be reinforced by neutralizing BAFF with belimumab, an antibody which presently is clinically approved for treatment of systemic lupus erythematosus. Based on the data presented in this study, a clinical study to evaluate whether drug repurposing of belimumab for BAFF neutralization can serve to improve response to small molecule inhibitor treatment in CLL is in preparation.

Abstract

The introduction of idelalisib, ibrutinib and venetoclax for treatment of chronic lymphocytic leukemia (CLL) has greatly improved long term survival of patients. However, many patients do not achieve complete remission and suffer from development of resistance upon treatment with these small molecule inhibitors. Here we report that the TNF family member B-cell activating factor (BAFF) mediates resistance of CLL cells to idelalisib, ibrutinib and venetoclax by sustaining survival and preventing apoptosis of the malignant B cells as revealed by analysis of cellular ATP levels and mitochondrial membrane integrity as well as caspase activation, respectively. As BAFF also plays a prominent role in autoimmune diseases, the BAFF-neutralizing antibody belimumab was developed and approved for treatment of systemic lupus erythematosus (SLE). When we employed belimumab in the context of CLL treatment with idelalisib, ibrutinib and venetoclax, BAFF neutralization was found to significantly increase the sensitivity of the leukemic cells to all three small molecule inhibitors. Notably, BAFF neutralization proved to be beneficial independently of clinical stage according to Binet and Rai or IgVH mutational status. Our results identify drug repurposing of belimumab for neutralization of BAFF to complement small molecule inhibitor treatment as a promising therapeutic approach in CLL that is presently undergoing clinical evaluation.

Multiple BCL2 mutations cooccurring with Gly101Val emerge in chronic lymphocytic leukemia progression on venetoclax

The BCL2 inhibitor venetoclax has complete response rates of up to 50% in chronic lymphocytic leukemia patients, but secondary resistance reflecting acquired mutations in BCL2 can lead to treatment failure. Blombery et al report that an unexpectedly large number of patients carry multiple BCL2 mutations with subclonal variation in their occurrence.

Prognostic value of high-sensitivity measurable residual disease assessment after front-line chemoimmunotherapy in chronic lymphocytic leukemia

Measurable residual disease (MRD) status is widely adopted in clinical trials in patients with chronic lymphocytic leukemia (CLL). Findings from FILO group trials (CLL2007FMP, CLL2007SA, CLL2010FMP) enabled investigation of the prognostic value of high-sensitivity (0.7 × 10^-5) MRD assessment using flow cytometry, in blood (N = 401) and bone marrow (N = 339), after fludarabine, cyclophosphamide, and rituximab (FCR)-based chemoimmunotherapy in a homogeneous population with long follow-up (median 49.5 months). Addition of low-level positive MRD < 0.01% to MRD ≥ 0.01% increased the proportion of cases with positive MRD in blood by 39% and in bone marrow by 27%. Compared to low-level positive MRD < 0.01%, undetectable MRD was associated with significantly longer progression-free survival (PFS) when using blood (72.2 versus 42.7 months; hazard ratio 0.40, p = 0.0003), but not when using bone marrow. Upon further stratification, positive blood MRD at any level, compared to undetectable blood MRD, was associated with shorter PFS irrespective of clinical complete or partial remission, and a lower 5-year PFS rate irrespective of IGHV-mutated or -unmutated status (all p < 0.05). In conclusion, high-sensitivity (0.0007%) MRD assessment in blood yielded additional prognostic information beyond the current standard sensitivity (0.01%). Our approach provides a model for future determination of the optimal MRD investigative strategy for any regimen.

Bayesian Population Model of the Pharmacokinetics of Venetoclax in Combination with Rituximab in Patients with Relapsed/Refractory Chronic Lymphocytic Leukemia: Results from the Phase III MURANO Study

BACKGROUND

Venetoclax is a selective B-cell lymphoma-2 (BCL-2) inhibitor approved for use as monotherapy or with rituximab in patients with chronic lymphocytic leukemia (CLL). The objectives of the current analysis of observed data from adult patients randomized to venetoclax-rituximab in the phase III MURANO study were to characterize venetoclax pharmacokinetics (PKs) using a Bayesian approach, evaluate whether a previously developed population PK model for venetoclax can describe the PKs of venetoclax when administered with rituximab, and to determine post hoc estimates of PK parameters for the exposure-response analysis.

METHODS

Parameter estimates and uncertainty estimated by a population PK model were used as priors. Additional covariate effects (CLL risk status, geographic region, and 17p deletion [del(17p)] status) were added to the model. The updated model was used to describe venetoclax PKs after repeated dosing in combination with rituximab, and to determine post hoc estimates of PK parameters for exposure-response analysis.

RESULTS

The PK analysis included 600 quantifiable venetoclax PK samples from 182 patients in the MURANO study. Model evaluation using standard diagnostic plots, visual predictive checks, and normalized prediction distribution error plots indicated no model deficiencies. There was no significant relationship between venetoclax apparent clearance (CL/F) and bodyweight, age, sex, mild and moderate hepatic and renal impairment, or coadministration of weak cytochrome P450 3A inhibitors. The chromosomal abnormality del(17p) and CLL risk status had no apparent effect on the PKs of venetoclax. A minimal increase in venetoclax CL/F (approximately 7%) was observed after coadministration with rituximab. CL/F was 30% lower in patients from Central and Eastern Europe (n = 60) or Asia (n = 4) compared with other regions (95% confidence interval [CI] 21-39%). Apparent central volume of distribution was 30% lower (95% CI 22-38%) in females (n = 56) compared with males (n = 126). No clinically significant impact of region or sex was observed on key safety and efficacy outcomes.

CONCLUSIONS

The Bayesian model successfully characterized venetoclax PKs over time and confirmed key covariates affecting PKs in the MURANO study. The model was deemed appropriate for further use in simulations and for generating individual patient PK parameters for subsequent exposure-response evaluation.

Overview of the Side-Effects of FDA- and/or EMA-Approved Targeted Therapies for the Treatment of Hematological Malignancies

In the last decade there has been tremendous effort in offering better therapeutic management strategies to patients with hematologic malignancies. These efforts have ranged from biological to clinical approaches and resulted in the rapid development of new approaches. The main “problem” that comes with the high influx of newly approved drugs, which not only influences hematologists that frequently work with these drugs but also affects other healthcare professionals that work with hematologists in patient management, including intensive care unit (ICU) physicians, is they have to keep up within their specialty and, in addition, with the side-effects that can occur when encountering hematology-specific therapies. Nonetheless, there are few people that have an in-depth understanding of a specialty outside theirs. Thus, this manuscript offers an overview of the most common side-effects caused by therapies used in hematology nowadays, or that are currently being investigated in clinical trials, with the purpose to serve as an aid to other specialties. Nevertheless, because of the high amount of information on this subject, each chapter will offer an overview of the side-effects of a drug class with each reference of the section being intended as further reading.

Distinct immune composition in lymph node and peripheral blood of CLL patients is reshaped during venetoclax treatment

Morbidity and mortality due to immunosuppression remain among the foremost clinical challenges in chronic lymphocytic leukemia (CLL). Although immunosuppression is considered to originate within the lymph node (LN) microenvironment, alterations in T and natural killer (NK) cells have almost exclusively been studied in peripheral blood (PB). Whereas chemoimmunotherapy further deteriorates immune function, novel targeted agents like the B-cell lymphoma 2 inhibitor venetoclax potentially spare nonmalignant lymphocytes; however, the effects of venetoclax on nonleukemic cells have not been explored. We address these unresolved issues using a comprehensive analysis of nonmalignant lymphocytes in paired LN and PB samples from untreated CLL patients, and by analyzing the effects of venetoclax-based treatment regimens on the immune system in PB samples from previously untreated and relapsed/refractory patients. CLL-derived LNs contained twice the amount of suppressive regulatory T cells (T_regs) and CLL supportive follicular T helper (T_fh) cells compared with PB. This was accompanied by a low frequency of cytotoxic lymphocytes. The expression of PD-1 by CD8⁺ T cells was significantly higher in LN compared with PB. Venetoclax-based treatment led to deep responses in the majority of patients, but also to decreased absolute numbers of B, T, and NK cells. T_fh cell, T_reg, and PD-1⁺ CD8⁺ T cell numbers were reduced more than fivefold after venetoclax-based therapy, and overproduction of inflammatory cytokines was reduced. Furthermore, we observed restoration of NK cell function. These data support the notion that the immunosuppressive state in CLL is more prominent within the LN. Venetoclax-based regimens reduced the immunosuppressive footprint of CLL, suggesting immune recovery after the elimination of leukemic cells.

Bcl-2/Bcl-xL inhibitor navitoclax increases the antitumor effect of Chk1 inhibitor prexasertib by inducing apoptosis in pancreatic cancer cells via inhibition of Bcl-xL but not Bcl-2

In our previous study, we showed that prexasertib, a checkpoint kinase 1 (Chk1) inhibitor, enhances the effects of standard drugs for pancreatic cancer, including gemcitabine (GEM), S-1, and the combination of GEM and S-1 (GS). The combination of prexasertib and GS has a strong antitumor effect and induces apoptosis in pancreatic cancer cells by downregulating anti-apoptotic protein Bcl-2. In the present study, we investigated the combined effect of GEM, S-1, and prexasertib with a selective Bcl-2 inhibitor (venetoclax) and a non-selective Bcl-2 inhibitor (navitoclax) in SUIT-2 pancreatic cancer cells. An MTT assay revealed that the combination of prexasertib with navitoclax showed a synergistic effect but the combination with venetoclax did not. Investigation of the pancreatic cancer cell lines SUIT-2, MIA PaCa-2, and BxPC-3 revealed that BxPC-3 also showed a high synergistic effect when combined with prexasertib and navitoclax but not venetoclax. Mechanistic analysis of the combined effect showed that apoptosis was induced. Bcl-2 knockdown with siRNA and prexasertib treatment did not induce apoptosis, whereas Bcl-xL knockdown with siRNA and prexasertib treatment resulted in strong induction of apoptosis. In addition, among the three cell lines, the combined effect of prexasertib and navitoclax resulted in increased apoptotic cell death because the protein expression levels of Bcl-xL and Chk1 were higher. Our results demonstrate that the combination of prexasertib and navitoclax has a strong antitumor effect and induces apoptosis in pancreatic cancer cells by downregulating Bcl-xL. Simultaneous inhibition of Chk1 and Bcl-xL could be a new strategy for treating pancreatic cancer.

Chronic lymphocytic leukemia: from molecular pathogenesis to novel therapeutic strategies

Chronic lymphocytic leukemia is a well-defined lymphoid neoplasm with very heterogeneous biological and clinical behavior. The last decade has been remarkably fruitful in novel findings elucidating multiple aspects of the pathogenesis of the disease including mechanisms of genetic susceptibility, insights into the relevance of immunogenetic factors driving the disease, profiling of genomic alterations, epigenetic subtypes, global epigenomic tumor cell reprogramming, modulation of tumor cell and microenvironment interactions, and dynamics of clonal evolution from early steps in monoclonal B cell lymphocytosis to progression and transformation into diffuse large B-cell lymphoma. All this knowledge has offered new perspectives that are being exploited therapeutically with novel target agents and management strategies. In this review we provide an overview of these novel advances and highlight questions and perspectives that need further progress to translate into the clinics the biological knowledge and improve the outcome of the patients.

Safety considerations with targeted therapy drugs for B-cell non-Hodgkin lymphoma

INTRODUCTION

B-cell non-Hodgkin lymphomas (B-NHLs) are the most frequent hematologic malignant cancers. Molecular targeted therapy is an important aspect of B-NHL treatment alongside cytotoxic chemotherapy, radiotherapy, and immunotherapy.

AREAS COVERED

Molecular targeted therapies have changed the landscape of treatment strategies for B-NHLs since the approval of rituximab, an anti-CD20 monoclonal antibody, by the US Food and Drug Administration in 1997. Currently, several targeted therapies have been approved or are in the later-phase of clinical trials including naked antibodies, antibody-drug conjugates, and small molecules, such as Bruton's tyrosine kinase (BTK) inhibitors, phosphatidylinositol 3-kinase (PI3 K) inhibitors, enhancer of zeste homolog 2 (EZH2) inhibitors, and B-cell lymphoma 2 (Bcl-2) inhibitors. These drugs have various toxicities because of their unique mechanisms of action. In this review, the available toxicity data of the targeted therapies for B-NHLs have been summarized.

EXPERT OPINION

Recent clinical developments of targeted therapies for B-NHLs have provided several useful effective therapeutic options for patients. However, there are unique toxicities that need to be resolved. It is necessary to find out the toxicity mechanism; optimal treatment strategy for these toxicities; and novel targeted therapies that might potentially overcome the toxicities of previously approved targeted therapies.

Emerging drugs for the treatment of light chain amyloidosis

INTRODUCTION

Systemic AL amyloidosis is a protein-misfolding disorder that is characterized by the deposition of insoluble amyloid fibrils derived from kinetically unstable light chains. Achieving a rapid and deep hematologic response is critical for long-term survival.

AREAS COVERED

This review covers the existing and emerging treatment options for systemic AL, divided into anti-plasma cell and fibril-directed therapies. The anti-CD38 monoclonal antibody daratumumab has demonstrated an unprecedented hematologic response rate and will become the new standard-of-care in newly diagnosed patients in combination with CyBorD/VCD. Other plasma cell-directed drugs that have prospective data on safety and efficacy in AL include proteasome inhibitors [bortezomib and ixazomib], immunomodulatory drugs [lenalidomide and pomalidomide], and alkylating agents [melphalan and bendamustine]. A major unmet need is the development of fibril-directed therapies with the goal of eliminating amyloid fibrils that are already deposited in vital organs.

EXPERT OPINION

The treatment of newly diagnosed AL in the future will likely include daratumumab-based therapy in conjunction with fibril-directed therapy. The most promising second line drugs are venetoclax [for t(11;14)] and pomalidomide, with several others in the pipeline, including antibody-drug conjugates. Minimal residual disease will emerge as a new endpoint for drug development and will potentially guide treatment duration.

Combining T-cell-based immunotherapy with venetoclax elicits synergistic cytotoxicity to B-cell lines in vitro

Alterations of B-cell lymphoma 2 (BCL-2) family proteins contribute to the survival of B-cell malignancies. Recently, venetoclax, a BCL-2 inhibitor, was approved for B-cell chronic lymphocytic leukemia therapy and is being investigated in clinical trials for a variety of hematologic cell malignancies. Furthermore, combination therapy with other molecularly targeted drugs was reported to be more effective than monotherapy. However, combining venetoclax with immunotherapy based on T-cells has not been tested. Because both venetoclax and granzyme B activate the mitochondrial apoptosis pathway by targeting different BCL-2 family molecules, it is possible that combinations of venetoclax with immunotherapy will be effective treatments. We examined the effect of combining venetoclax with immunotherapy using an in vitro model system involving cytomegalovirus (CMV) pp65 antigen-specific cytotoxic T-cells (CMV-CTLs) as the effector cells and CMVpp65 antigen-expressing B-cell lines as the target cells. Cytotoxicity of CMV-CTLs to the target B-cell lines was enhanced by venetoclax with combination index values of 0.47-0.83. This suggests that venetoclax synergizes with T-cell-based immunotherapy to affect B-cell malignancies. Interestingly, venetoclax synergized not only with antigen-specific cytotoxicity but also with nonspecific cytotoxicity. Importantly, CMV-CTLs could be expanded in the presence of venetoclax at the maximum concentration (5 μM) that induced apoptosis in resting CMV-CTLs. B-cell lymphoma-extra large (BCL-xL) expression in CMV-CTLs increased transiently after activation by CMVpp65-transfected B-cell lines, indicating that the expression of BCL-xL was important for the effectiveness of combination treatment with venetoclax. These findings suggest that T-cell-based immunotherapy combined with venetoclax is effective against B-cell malignancies.

Cost-effectiveness of New Targeted Agents in the Treatment of Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is the most common adult leukemia and is clinically heterogeneous. Integration of oral targeted therapies (OTTs) in the management of CLL has fundamentally altered CLL treatment pathways and improved outcomes for patients with CLL.We review the cost-effectiveness of OTTs in the treatment of CLL. We used MeSH (Medical Subject Heading) terms and keywords to search the National Library of Medicine online MEDLINE database (PubMed) for articles related to cost-effectiveness of OTTs in CLL care.Oral targeted therapies add considerable expense to the treatment of CLL for patients and the health care system. Cost-effectiveness analyses of OTTs are not uniform in their conclusions and depend on patient groups selected for analysis. Given the substantial increase in expense associated with integration of OTTs in CLL treatment, cost reduction methods are needed to ensure equitable access to novel therapies for all patients with CLL.

Relevance of Minimal Residual Disease in the Era of Targeted Agents

The evaluation of minimal residual disease (MRD) in chronic lymphocytic leukemia (CLL) has evolved in parallel with the enormous progresses in the therapeutic armamentarium and the application of cutting-edge diagnostic techniques the CLL community witnessed in the past few years. Minimal residual disease is considered an objective measure of disease status defined by the number of residual leukemic cells detected in a sample of peripheral blood and/or bone marrow as proportion of the total white blood cells and defined undetectable if fewer than 1 CLL cell among 10,000 white blood cells (10 or 0.01%) is detected. In this review, we aim at shedding light on how to evaluate MRD, what we already know about MRD from the experience with chemoimmunotherapy, and why MRD evaluation remains still relevant in the era of targeted agents.

Resistance Mechanisms to Targeted Agents in Chronic Lymphocytic Leukemia

Agents that specifically target pathologic mechanisms of survival have now been approved for the treatment of chronic lymphocytic leukemia in both the treatment-naive and relapsed/refractory settings. These 4 agents include the Bruton tyrosine kinase inhibitor ibrutinib, the B-cell leukemia/lymphoma-2 inhibitor venetoclax, and the phosphatidylinositol-3 kinase inhibitors idelalisib and duvelisib. Although clinical outcomes are improved with all of these inhibitors, acquired resistance does occur and leads to progression of disease. Resistance to targeted therapy can occur through direct mutations of the target or through the overexpression of alternative cell survival pathways not affected by the specific inhibitor. Determining which patients will develop resistance, why resistance occurs, how to overcome resistance, and when to test for resistance are all subjects of ongoing research. In this review, we describe the current data relative to the development of resistance to targeted therapies in CLL.

Phase II Study of Combination Obinutuzumab, Ibrutinib, and Venetoclax in Treatment-Naïve and Relapsed or Refractory Chronic Lymphocytic Leukemia

PURPOSE

The development of highly effective targeted agents for chronic lymphocytic leukemia offers the potential for fixed-duration combinations that achieve deep remissions without cytotoxic chemotherapy.

PATIENTS AND METHODS

This phase II study tested a combination regimen of obinutuzumab, ibrutinib, and venetoclax for a total of 14 cycles in both patients with treatment-naïve (n = 25) and relapsed or refractory (n = 25) chronic lymphocytic leukemia to determine the response to therapy and safety.

RESULTS

The primary end point was the rate of complete remission with undetectable minimal residual disease by flow cytometry in both the blood and bone marrow 2 months after completion of treatment, which was 28% in both groups. The overall response rate at that time was 84% in treatment-naïve patients and 88% in relapsed or refractory patients. At that time, 67% of treatment-naïve patients and 50% of relapsed or refractory patients had undetectable minimal residual disease in both the blood and marrow. At a median follow-up of 24.2 months in treatment-naïve patients and 21.5 months in relapsed or refractory patients, the median progression-free and overall survival times were not yet reached, with only 1 patient experiencing progression and 1 death. Neutropenia and thrombocytopenia were the most frequent adverse events, followed by hypertension. Grade 3 or 4 neutropenia was experienced by 66% of patients, with more events in the relapsed or refractory cohort. There was only 1 episode of neutropenic fever. A favorable impact on both perceived and objective cognitive performance during treatment was observed.

CONCLUSION

The combination regimen of obinutuzumab, ibrutinib, and venetoclax offers time-limited treatment that results in deep remissions and is now being studied in phase III cooperative group trials.

Azole antifungals and new targeted therapies for hematological malignancy

PURPOSE OF REVIEW

With the introduction of new targeted therapies for hematological malignancies comes the challenges of both assessing the risk of developing an IFD while being treated with these agents, as well as managing the drug--drug interactions between azole antifungals and the agents.

RECENT FINDINGS

New targeted therapies for hematological malignancy include chimeric antigen receptor T cells (CAR T cells), Bi-specific T-cell Engager (BiTE) blinatumomab, and the antibody-drug conjugate (ADC) of calicheamicin inotuzumab ozogamicin for acute lymphoblasic leukemia (ALL) and lymphoma; the Bruton's tyrosine kinase (BTK) inhibitor ibrutinib and phosphatidylinositol 3-kinase (PI3Kδ) inhibitor idelalisib for lymphoma and graft-versus-host disease (GVHD); FMS-like tyrosine kinase 3 (FLT3) inhibitors, such as midostaurin, sorafenib and gilteritinib for acute myeloid leukemia (AML); and the BCL-2 inhibitor venetoclax for a range of hematological malignancies including lymphoma and leukemia. This review summarizes recommendations for IFD prophylaxis using these therapies and evidence for managing concomitant azole administration.

SUMMARY

Whilst some evidence exists to guide IFD prophylaxis using new targeted therapies for hematological malignancies, there is an overall lack of descriptive, robust studies specifically describing IFD risk and management. With the emergence of novel agents, clinical judgment must be used to assess the risk of developing an IFD. Care must also be taken when administering azoles with drug--drug interactions, often requiring dose adjustment of the cancer therapies.

Recent advances in chronic lymphocytic leukemia therapy

Chronic lymphocytic leukemia is a genetically heterogeneous disease, and a complex set of genetic alterations is associated with its pathogenesis. CLL is the most common leukemia in the western countries, whereas it is rare in Asia, including Korea. The prognostic models integrate the traditional staging systems developed by Rai et al. and Binet et al. with biochemical and genetic markers. With the advent of molecular biology, a variety of targeted agents, including anti-CD20 antibodies, inhibitors of BCR signaling pathway, and BCL-2 inhibitors, have been introduced, which has changed the landscape of CLL treatment greatly. This review will focus on the risk stratification and the management of CLL in the era of novel small molecules.

The combination of venetoclax and rituximab for the treatment of patients with recurrent chronic lymphocytic leukemia

INTRODUCTION

In patients with recurrent chronic lymphocytic leukemia (CLL), treatment with targeted agents such as Bruton tyrosine kinase inhibitors and the Bcl-2 inhibitor venetoclax is rapidly replacing chemo-immunotherapy regimens. Venetoclax has demonstrated efficacy as monotherapy in patients with previously treated CLL and has been evaluated in combination with the anti-CD20 monoclonal antibody rituximab.

AREAS COVERED

This review focuses on the activity and toxicity of the time-limited combination of venetoclax plus rituximab for the treatment of relapsed or refractory CLL, presenting clinical trial results and data from correlative studies, with the aim of highlighting the strengths of this treatment approach and discuss weaknesses and possible areas of improvement. Data from PubMed indexed papers as well as from abstracts presented at major international conferences are included.

EXPERT OPINION

Deep responses with venetoclax-based regimens have been shown to allow time-limited treatment and prolonged remission off-therapy in patients with CLL. The clinical benefit of venetoclax and rituximab over chemo-immunotherapy has been demonstrated in recurrent CLL. Potential advantages of time-limited treatment approaches include avoidance of long-term toxicities, high drug costs, and the selection of resistant subclones.

Comparison of Access to Novel Drugs for Lymphoma and Chronic Lymphocytic Leukemia Between India and the United States

This review will compare and contrast the costs and access to novel drugs for treating chronic lymphocytic leukemia (CLL) and lymphoma in the United States and India during the last 5 years. Clinical outcomes for patients with hematologic malignancies have improved significantly since the approval of immunotherapeutic and targeted therapies. These new treatments have had an impact on overall outcomes and have helped determine the design for translational research and future trials. Although most of these novel drugs called “innovators” are initially approved and marketed in the United States, several have also become available in countries such as India. With the expiration of patents, generic versions of innovator drugs have increased and accessibility has improved for patients. The advent of biosimilars is another route for expanding access to biologic compounds. As a result, the development costs for developing these drugs are lower, and consequently, the costs for the patient are often lower. Although the delivery of cancer care is not the same in India as it is in the United States, the introduction of biosimilars and generics has helped bridge the gap. This has made treatment of CLL and lymphoma similar in both countries and has had the same impact on patient outcomes and quality of life. Compulsory licensing for essential medications, as stipulated by the Doha Declaration, and capping of drug prices could improve global access to treatments for CLL and lymphoma.

Assessment of the Efficacy of Therapies Following Venetoclax Discontinuation in CLL Reveals BTK Inhibition as an Effective Strategy

PURPOSE

Venetoclax-based therapy is a standard-of-care option in first-line and relapsed/refractory chronic lymphocytic leukemia (CLL). Patient management following venetoclax discontinuation remains nonstandard and poorly understood.

EXPERIMENTAL DESIGN

To address this, we conducted a large international study to identify a cohort of 326 patients who discontinued venetoclax and have been subsequently treated. Coprimary endpoints were overall response rate (ORR) and progression-free survival for the post-venetoclax treatments stratified by treatment type [Bruton's tyrosine kinase inhibitor (BTKi), PI3K inhibitor (PI3Ki), and cellular therapies].

RESULTS

We identified patients with CLL who discontinued venetoclax in the first-line (4%) and relapsed/refractory settings (96%). Patients received a median of three therapies prior to venetoclax; 40% were BTKi naïve (n = 130), and 81% were idelalisib naïve (n = 263). ORR to BTKi was 84% (n = 44) in BTKi-naïve patients versus 54% (n = 30) in BTKi-exposed patients. We demonstrate therapy selection following venetoclax requires prior novel agent exposure consideration and discontinuation reasons.

CONCLUSIONS

For BTKi-naïve patients, selection of covalently binding BTKis results in high ORR and durable remissions. For BTKi-exposed patients, covalent BTK inhibition is not effective in the setting of BTKi resistance. PI3Kis following venetoclax do not appear to result in durable remissions. We conclude that BTKi in naïve or previously responsive patients and cellular therapies following venetoclax may be the most effective strategies.See related commentary by Rogers, p. 3501.

A retrospective comparison of venetoclax alone or in combination with an anti-CD20 monoclonal antibody in R/R CLL

Venetoclax (VEN) is approved for relapsed/refractory (R/R) chronic lymphocytic leukemia (CLL) as monotherapy (VENmono) or in combination with rituximab. Whether VEN plus anti-CD20 (VENcombo) is superior to VENmono is unknown. We conducted a multicenter, retrospective cohort analysis comparing 321 CLL patients treated with VENmono vs VENcombo across the United States and the United Kingdom. We examined demographics, baseline characteristics, dosing, adverse events, response rates, and outcomes. The primary endpoints were progression-free survival (PFS) and overall survival (OS), estimated by Kaplan-Meier method, in patients treated with VENmono vs VENcombo. Univariate and bivariate analyses were performed with COX regression. Three hundred twenty-one CLL patients were included (3 median prior treatments, 78% prior ibrutinib). The overall response rates (ORRs) were similar (VENmono, 81% ORR, 34% complete remission [CR] vs VENcombo, 84% ORR, 32% CR). With a median follow-up of 13.4 months, no differences in PFS and OS were observed between the groups. In unadjusted analyses, the hazard ratios (HRs) for PFS and OS for VENmono vs VENcombo were HR 1.0 (95% confidence interval [CI], 0.6-1.8; P = .7) and HR 1.2 (95% CI, 0.6-2.3; P = .5), respectively. When adjusting for differences between the cohorts, the addition of an anti-CD20 antibody in combination with VEN did not impact PFS (HR, 1.0; 95% CI, 0.5-2.0; P = .9) or OS (HR, 1.1; 95% CI, 0.4-2.6; P = .8). We demonstrate comparable efficacy between VENmono and VENcombo in a heavily pretreated, high-risk, retrospective cohort, in terms of both response data and survival outcomes. Prospective studies are needed to validate these findings.

Venetoclax – The Game-changer in Hematology

The introduction of small molecule inhibitors in many hematological malignancies made a landmark achievement in this field with a dramatic change in the survival outcome. Venetoclax is a B-cell lymphoma-2 inhibitor which has become the game-changer molecule in chronic lymphocytic leukemia and acute myeloid leukemia. This review is intended to summarize the mechanism of action, side effects, dosage, and different phases of clinical trials of this drug with review of literature.

Targeting apoptosis in cancer therapy

For over three decades, a mainstay and goal of clinical oncology has been the development of therapies promoting the effective elimination of cancer cells by apoptosis. This programmed cell death process is mediated by several signalling pathways (referred to as intrinsic and extrinsic) triggered by multiple factors, including cellular stress, DNA damage and immune surveillance. The interaction of apoptosis pathways with other signalling mechanisms can also affect cell death. The clinical translation of effective pro-apoptotic agents involves drug discovery studies (addressing the bioavailability, stability, tumour penetration, toxicity profile in non-malignant tissues, drug interactions and off-target effects) as well as an understanding of tumour biology (including heterogeneity and evolution of resistant clones). While tumour cell death can result in response to therapy, the selection, growth and dissemination of resistant cells can ultimately be fatal. In this Review, we present the main apoptosis pathways and other signalling pathways that interact with them, and discuss actionable molecular targets, therapeutic agents in clinical translation and known mechanisms of resistance to these agents.

Medical comorbidities in patients with chronic lymphocytic leukaemia treated with idelalisib: analysis of two large randomised clinical trials

Comorbidities influence survival in patients with chronic lymphocytic leukaemia (CLL) treated with chemo-immunotherapy or ibrutinib. While idelalisib has been studied in patients with comorbidities, their impact has not been investigated. We analysed 481 patients treated with idelalisib on two randomised trials (NCT01659021 and NCT01539512). Comorbidities were assessed using the Cumulative Illness Risk Scale (CIRS). Patients received idelalisib + anti-CD20 (rituximab or ofatumumab; n = 284) or anti-CD20 alone (n = 197). The median age was 69 years. We found that comorbidities did not significantly affect outcomes of idelalisib therapy. The objective response rate (ORR) was 79·3% versus 85·8%, the median progression-free survival (PFS) was 16·3 versus 19·1 months, and the median overall survival (OS) was 39·8 versus 49·8 months in patients treated with idelalisib who had a CIRS score of >6 versus ≤6, correspondingly. Treatment with idelalisib + anti-CD20 was associated with superior PFS and ORR when compared to anti-CD20 monotherapy in patients who had high comorbidities (CIRS score of >6) or at least one severe comorbidity (median PFS 16·3 vs. 6·9 months and 16·6 vs. 6·5 months; odds ratio 20·1 and 33·2; P < 0·0001). Thus, comorbidities do not portend inferior outcomes in patients with CLL treated with idelalisib in combination with anti-CD20 therapy.

TP53 dysfunction in chronic lymphocytic leukemia: clinical relevance in the era of B-cell receptors and BCL-2 inhibitors

INTRODUCTION

Patients with TP53 dysfunction, assessed by del(17p) or TP53 mutations, respond poorly to chemo-immunotherapy and fare better with the new therapies (BCR and BCL-2 inhibitors); however, it is unclear whether their response is similar to that of patients without anomalies or whether there is currently an adequate determination of TP53 dysfunction.

AREA COVERED

A literature search was undertaken on clinical trials and real-world experience data on patients with TP53 dysfunction treated with different protocols. Moreover, data on the TP53 biological function and on the tests currently employed for its assessment were reviewed.

EXPERT OPINION

Although TP53 dysfunction has less negative influence on the new biological therapies, patients with these alterations, particularly those with biallelic inactivation of TP53, have a worst outcome with these therapies than those without alterations. At present, a determination of TP53, particularly with next generation sequencing (NGS) methodologies, may be sufficient for the identifications of the patients unsuitable for chemo-immunotherapy, although integration with del(17p) would be advisable. For the future, more extensive determinations of the TP53 status, including functional assays, may become part of the current armamentarium for a better patient stratification and treatment with newer protocols.

A small-molecule ARTS mimetic promotes apoptosis through degradation of both XIAP and Bcl-2

Many human cancers over-express B cell lymphoma 2 (Bcl-2) or X-linked inhibitor of apoptosis (IAP) proteins to evade cell death. The pro-apoptotic ARTS (Sept4_i2) protein binds directly to both Bcl-2 and XIAP and promotes apoptosis by stimulating their degradation via the ubiquitin-proteasome system (UPS). Here we describe a small molecule, A4, that mimics the function of ARTS. Microscale thermophoresis assays showed that A4 binds XIAP, but not cellular inhibitor of apoptosis protein 1 (cIAP1). A4 binds to a distinct ARTS binding pocket in the XIAP-BIR3 (baculoviral IAP repeat 3) domain. Like ARTS, A4 stimulated poly-ubiquitylation and UPS-mediated degradation of XIAP and Bcl-2, but not cIAP1, resulting in caspase-9 and -3 activation and apoptosis. In addition, over-expression of XIAP rescued HeLa cells from A4-induced apoptosis, consistent with the idea that A4 kills by antagonizing XIAP. On the other hand, treatment with the SMAC-mimetic Birinapant induced secretion of tumour necrosis factor-α (TNFα) and killed ~50% of SKOV-3 cells, and addition of A4 to Birinapant-treated cells significantly reduced secretion of TNFα and blocked Birinapant-induced apoptosis. This suggests that A4 acts by specifically targeting XIAP. The effect of A4 was selective as peripheral blood mononuclear cells and normal human breast epithelial cells were unaffected. Furthermore, proteome analysis revealed that cancer cell lines with high levels of XIAP were particularly sensitive to the killing effect of A4. These results provide proof of concept that the ARTS binding site in XIAP is "druggable". A4 represents a novel class of dual-targeting compounds stimulating apoptosis by UPS-mediated degradation of important anti-apoptotic oncogenes.

The fading star of obinutuzumab-chlorambucil regimen in patients with comorbidities with chronic lymphocytic leukemia - are we ready for chemo-free immunotherapy approach?

INTRODUCTION

Chronic lymphocytic leukemia (CLL) is the most common leukemia in Western countries occurring typically in elderly patients. These patients often present with comorbidities limiting treatment options. During the last decade, the treatment paradigm has rapidly changed with the introduction of novel oral targeted agents and monoclonal antibodies.

AREAS COVERED

The review focuses on the combination of type II antiCD20 antibody obinutuzumab in combination with chemotherapy or oral targeted agents in patients not suited for fludarabine-based therapy because of comorbidities or age. The main focus of the review is whether classical immunochemotherapy with obinutuzumab-chlorambucil is still a valid therapeutic option or whether the combination of obinutuzumab and ibrutinib or venetoclax presents novel standard of care.

EXPERT OPINION

Both pivotal and registrational studies iLLLUMINATE study testing the combination of ibrutinib and obinutuzumab and CLL14 study testing the fixed combination of venetoclax and obinutuzumab have shown major benefit over chemoimmunotherapy approach in this population. Furthermore, they have excellent activity in high-risk subgroups of CLL paving the road toward a chemo-free immunotherapy approach in this setting. However, there are some pitfalls in these strategies warranting further research.

Frontline Therapy of Chronic Lymphocytic Leukemia: Changing Treatment Paradigm

PURPOSE OF REVIEW

The treatment landscape of treatment-naive chronic lymphocytic leukemia (TN-CLL) is rapidly evolving. As more and more new drugs and combinations are becoming part of therapeutic armamentarium, it becomes highly pertinent to understand the evidence for each of the treatment options to select the right drug for the right patient. We summarize the recent data of the available frontline treatment options.

RECENT FINDINGS

The novel agents can overcome adverse biological attributes and provide long-term disease control. MRD may become a reliable surrogate for survival in the evaluation of future therapies. FCR still remains one of the best options in a young fit CLL with mutated IGVH. Long-term follow-up data of ibrutinib confirm its efficacy and safety in both high-risk and elderly TN-CLL patients. A combination of venetoclax with obinutuzumab has provided the hope of fixed-duration therapy and the potential for functional cure in TN-CLL. Several other trials testing the efficacy of other targeted agents and the optimal sequencing approaches are underway. Chemoimmunotherapy holds its ground as an effective treatment in the IGVH-mutated CLL. The targeted agents either singly or in combination have become standard of care in many subsets of TN-CLL.

Novel BCL2 mutations in venetoclax-resistant, ibrutinib-resistant CLL patients with BTK/PLCG2 mutations

Lucas et al explored the clonal dynamics of chronic lymphocytic leukemia (CLL) patients following treatment and subsequent acquired resistance to ibrutinib and then venetoclax. They report different patterns of resistance mutations from previously reported changes following venetoclax treatment in the absence of prior BTK inhibitor therapy.

Atrial fibrillation in patients with chronic lymphocytic leukemia (CLL) treated with ibrutinib: risk prediction, management, and clinical outcomes

BACKGROUND

Ibrutinib therapy is associated with an increased risk of atrial fibrillation (AF) in chronic lymphocytic leukemia (CLL). Risk assessment tools and outcomes of AF in these patients are not well described.

METHODS

We performed a retrospective review of patients with CLL treated with ibrutinib at Mayo Clinic between October 2012 and November 2018.

RESULTS

Two hundred ninety-eight patients were identified with a median time on ibrutinib of 19 months (range 0.23-69.7 months). Fifty-one patients developed treatment-emergent AF; the risk of treatment-emergent AF at 6 months, 1 year, and 2 years was 9%, 12%, and 16%, respectively. The following were associated with an increased risk of treatment-emergent AF on multivariable analyses: past history of AF (hazard ratio [HR] 3.5, p = 0.0072) and heart failure (HR 3.4, p = 0.0028). Most patients are able to continue ibrutinib therapy (dose reduced in 43%). Development of treatment-emergent AF was associated with shorter event-free survival (EFS; HR 2.0, p = 0.02) and shorter overall survival (OS; HR 3.2, p = 0.001), after adjusting for age, prior treatment status, TP53 disruption, heart failure, valvular disease, and past history of AF.

CONCLUSIONS

Patient comorbidities, rather than CLL-related factors, predict risk of treatment-emergent AF in patients treated with ibrutinib. Although the vast majority of patients with treatment-emergent AF are able to continue ibrutinib (with dose reduction in 43%), treatment-emergent AF appears to be associated with worse outcomes, independent of other adverse prognostic factors.

ASCEND: Phase III, Randomized Trial of Acalabrutinib Versus Idelalisib Plus Rituximab or Bendamustine Plus Rituximab in Relapsed or Refractory Chronic Lymphocytic Leukemia

PURPOSE

Acalabrutinib, a highly selective, potent, Bruton tyrosine kinase inhibitor, was evaluated in this global, multicenter, randomized, open-label, phase III study in patients with relapsed/refractory (R/R) chronic lymphocytic leukemia (CLL).

METHODS

Eligible patients, aged ≥ 18 years with R/R CLL, were randomly assigned 1:1 centrally and stratified by del(17p) status, Eastern Cooperative Oncology Group performance status score, and number of prior lines of therapy. Patients received acalabrutinib monotherapy or investigator's choice (idelalisib plus rituximab [I-R] or bendamustine plus rituximab [B-R]). The primary end point was progression-free survival (PFS) assessed by an independent review committee (IRC) in the intent-to-treat population. Key secondary end points included IRC-assessed overall response rate, overall survival, and safety.

RESULTS

From February 21, 2017, to January 17, 2018, a total of 398 patients were assessed for eligibility; 310 patients were randomly assigned to acalabrutinib monotherapy (n = 155) or investigator's choice (n = 155; I-R, n = 119; B-R, n = 36). Patients had received a median of two prior therapies (range, 1-10). After a median follow-up of 16.1 months (range, 0.03-22.4 months), median PFS was significantly longer with acalabrutinib monotherapy (PFS not reached) compared with investigator's choice (16.5 months [95% CI, 14.0 to 17.1 months]; hazard ratio, 0.31 [95% CI, 0.20 to 0.49]; P < .0001). Estimated 12-month PFS was 88% (95% CI, 81% to 92%) for acalabrutinib and 68% (95% CI, 59% to 75%) for investigator's choice. Serious adverse events occurred in 29% of patients (n = 44 of 154) treated with acalabrutinib monotherapy, 56% (n = 66 of 118) with I-R, and 26% (n = 9 of 35) with B-R. Deaths occurred in 10% (n = 15 of 154), 11% (n = 13 of 118), and 14% (n = 5 of 35) of patients receiving acalabrutinib monotherapy, I-R, and B-R, respectively.

CONCLUSION

Acalabrutinib significantly improved PFS compared with I-R or B-R and has an acceptable safety profile in patients with R/R CLL.

Promises and pitfalls of targeted agents in chronic lymphocytic leukemia

Targeted agents have significantly improved outcomes for patients with chronic lymphocytic leukemia, particularly high-risk subgroups for whom chemoimmunotherapy previously offered limited efficacy. Two classes of agent in particular, the Bruton tyrosine kinase inhibitors (e.g., ibrutinib) and the B-cell lymphoma 2 inhibitor, venetoclax, induce high response rates and durable remissions in the relapsed/refractory and frontline settings. However, maturing clinical data have revealed promises and pitfalls for both agents. These drugs induce remissions and disease control in the majority of patients, often in situations where modest efficacy would be expected with traditional chemoimmunotherapy approaches. Unfortunately, in the relapsed and refractory setting, both agents appear to be associated with an inevitable risk of disease relapse and progression. Emerging patterns of resistance are being described for both agents but a common theme appears to be multiple sub-clonal drivers of disease progression. Understanding these mechanisms and developing effective and safe methods to circumvent the emergence of resistance will determine the longer-term utility of these agents to improve patients' quality and length of life. Rational drug combinations, optimised scheduling and sequencing of therapy will likely hold the key to achieving these important goals.

Inhibition of Anti-Apoptotic Bcl-2 Proteins in Preclinical and Clinical Studies: Current Overview in Cancer

The dynamic interplay between pro-death and pro-survival Bcl-2 family proteins is responsible for a cell’s fate. Due to the recognized relevance of this family in cancer progression and response to therapy, different efforts have made in recent years in order to develop small molecules able to target anti-apoptotic proteins such as Bcl-2, Bcl-xL and Mcl-1. The limitations of the first Bcl-2 family targeted drugs, regarding on-target and off-target toxicities, have been overcome with the development of venetoclax (ABT-199), the first BH3 mimetic inhibitor approved by the FDA. The purpose of this review is to discuss the state-of-the-art in the development of drugs targeting Bcl-2 anti-apoptotic proteins and to highlight the potential of their application as single agents or in combination for improving anti-cancer therapy, focusing in particular on solid tumors.