Care For Chronic Lymphocytic Leukemia Research Articles

Depletion of the Mitochondrial E3 Ligase MARCH5 Induces Synthetic Lethality to BCL2 Inhibitor (Venetoclax) Therapy in Cell Lines Representative of Diverse Blood Cancers

Combination therapies incorporating the BCL2 inhibitor, venetoclax (VEN), are standards of care in chronic lymphocytic leukemia (CLL) and acute myeloid leukemia (AML), and display promising activity against mantle cell lymphoma (MCL), multiple myeloma (MM) and many other hematologic malignancies. However, primary resistance is observed in some diseases and even across responsive malignancies, enduring cells typically persist, ultimately driving relapse and precluding cure. Genome wide CRISPR/Cas9 screens have the potential to identify novel mediators of venetoclax resistance. However, conventional knock-out/drop out (KO/DO) screens have several limitations including the frequent identification of common essential genes as false positives and the large scale required to detect DO with high statistical confidence. We devised a novel augmentation on the conventional CRISPR/Cas9 KO/DO screen utilizing two MCL cell lines (Jeko1, Z138) which were both resistant to apoptosis induced by VEN +/- ibrutinib (IBR)(Fig 1). Rather than detecting sensitizing hits through DO, we positively enriched for sensitizing hits by flow-sorting the rare (~10%) population of cells initiating apoptosis as indicated by AnnexinV positivity after brief (6hr) BH3-mimetic exposure. At this early time point, cells whose KO had led to a lowered apoptotic threshold could be identified without sufficient time for DNA degradation. DNA yield from dying cells approached 100% efficiency. sgRNA frequencies among the control cells and those undergoing early apoptosis were analyzed using MAGecKE-MLE. This method was anticipated to reduce common essential gene contamination, increase statistical power to detect sensitizing hits due to enrichment rather than DO of relevant genes, and identify targets likely to exhibit synthetic lethality (i.e. neither VEN nor KO alone are lethal, but combination achieves potent killing). The screens in both cell lines demonstrated significant depletion of common essential genes defined by DepMap by D14 (prior to treatment). Consistent with the increased power expected from a positive selection screen, both yielded >50 statistically significant VEN-sensitizing hits, after correction for multiple hypothesis testing. These included the expected KOs of MCL1 and BCL2L1 (BCL-X L), confirming the validity of the method. sgRNAs resulting in KO of the E3 ligase MARCH5 were among the most enriched within dying (VEN-sensitized) cells in both Jeko1 and Z138 screens, with either VEN only or VEN+IBR treatment (Fig 1). The screen method was repeated in Jeko1 cells using the MCL1 inhibitor AMG176 and BCL-X L inhibitor A1331853, and again yielded BCL2 as well as novel hits, including MARCH5 KO as a sensitizing hit to BCL-X L inhibition. KO of MARCH5 markedly sensitized multiple human blood cancer cell lines to venetoclax (Table 1), including sensitive and resistant lines, with and without functional TP53. In Jeko1 (MCL) cells, which are highly resistant to BCL2 or BCL-X L inhibition when wildtype (10-20% apoptosis at 6µM), MARCH5 KO induced marked sensitization to single-agent VEN (LC50 8nM) or A1331853 (LC50 375nM).By introducing a degron dTAG MARCH5 construct into MARCH5 KO Jeko1 cells, we demonstrated dose-dependent sensitisation to VEN with MARCH5 depletion, marked synergy (mean Bliss score: 22.97) and synthetic lethality. Degron dTAG-mediated depletion of MARCH5 demonstrated synergy with venetoclax in MOLM13 (AML) and Z138 (MCL) cell lines, and enhanced in vitro killing of MOLM13 by VEN + azacytidine, and killing of Jeko1 and Z138 by VEN + IBR. CRISPR “death” represents a powerful modification to conventional CRISPR KO screens, with reduced common essential gene false positives, increased statistical power and enrichment for synthetic lethal hits. We demonstrate the pan-hematologic, dose-dependent VEN-sensitization achieved by MARCH5 depletion across multiple blood cancer lines with and without normal TP53 function. MARCH5 depletion also sensitizes blood cancer cell lines to BCL-X L inhibition. Addition of MARCH5 depletion to VEN-combination treatment improved MCL and AML killing in vitro and this target should be prioritized for accelerated drug development.

A History of Targeted Therapy Development and Progress in Novel-Novel Combinations for Chronic Lymphocytic Leukemia (CLL).

Over the last 10 years, the traditional treatment paradigms for CLL have been upended as the use of traditional chemoimmunotherapy regimens has declined in favor of novel targeted therapies. Targeted therapies have become the new standard of care in CLL given their superior progression-free survival (and overall survival, in some cases) when compared with chemoimmunotherapy, as well as their improved toxicity profiles. Targeted agents are FDA approved for the treatment of CLL including ibrutinib, acalabrutinib, zanubrutinib, and venetoclax. Importantly, as opposed to traditional chemotherapy regimens, the benefits of these targeted therapies appear to be consistent regardless of high-risk mutational status. In this review, we discuss the pivotal CLL studies of the last decade and the data supporting doublet and triplet novel-novel combinations. We explore the use of new surrogate end points for PFS/OS in targeted therapies such as undetectable minimal residual disease (uMRD) and their potential role in minimizing toxicity by permitting earlier treatment discontinuation. We also highlight areas that warrant further exploration and future studies that may help address some of these key questions.

Population-wide patterns of care in chronic lymphocytic leukemia in Australia: An analysis of the pharmaceutical benefits scheme dataset.

e19518 Background: The treatment landscape in patients with chronic lymphocytic leukemia (CLL) is changing with the approvals of Bruton’s tyrosine kinase inhibitors (BTKis) in Australia. We sought to understand the practice impact of the introduction of publicly funded novel agents for the treatment of CLL. The objective of this study was to describe the evolving treatment patterns of Australian patients with CLL over the last 10 years using population-wide prescription records. Methods: Patients who initiated a treatment for CLL between 01/01/2011 and 07/31/2021 were extracted from the Services Australia 10% Pharmaceuticals Benefits Scheme (PBS) dataset. This dataset includes the dispensing records for 10% of the Australian population and captures all publicly funded treatments in Australia. The index date was defined as the commencement of any drug for the treatment of CLL. First-line (1L) therapy was defined as the first treatments prescribed for CLL. A patient was defined as relapsed/refractory (R/R) if they had commenced a drug which was in a different therapeutic category, or if they re-started the same regimen after a gap of more than 180 days. Descriptive analyses were conducted to examine the use of treatment regimens for the overall 10-year population by line of therapy. Analyses by calendar year were also performed to assess changes in treatment patterns. Results: Overall, 803 patients with CLL were identified. The majority of patients were male (65%) and age > 60 years (77%), with most being aged 70-79 years (33% of total). Many patients were receiving comedications at baseline, including antihypertensives (47%), antipsychotics or antidepressants (17%), and/or anticoagulants (13%). In the overall population (2011-2021), the majority of patients had received 1L treatment with fludarabine-cyclophosphamide-rituximab (FCR, 49%), chlorambucil ± CD20 (27%), or CD20 monotherapy (17%). The most commonly used regimens in R/R patients at any subsequent episode of treatment included CD20 monotherapy (56%), BTKi (41%) or FCR (33%). A trend in adoption of novel agents was observed throughout the years following their PBS listing. Analysis by calendar year showed that from 2011 to 2020 use of FCR in 1L decreased from 78% to 10%; and use of BTKis in R/R increased from 0% to 62%. Conclusions: CLL treatment patterns have significantly changed in Australia since the introduction of the BTKis (e.g., ibrutinib, acalabrutinib). The use of FCR in 1L CLL has decreased and use of BTKis in R/R patients has increased.

Long-Term Sustained Responses Following Ibrutinib Discontinuation after Frontline Therapy with Obinutuzumab Plus Ibrutinib in Patients with Chronic Lymphocytic Leukemia

Single oral targeted therapies have emerged as a standard of care in chronic lymphocytic leukemia (CLL). However, accessibility, side effects, and financial burden associated with long term administration limit their clinical use. Mainly, it is unclear in what clinical situation discontinuation of oral therapy can be recommended. The combination of type II anti-CD20 antibody obinutuzumab-Gazyva® with ibrutinib (GI) has shown a significant progression-free survival benefit in patients (pts) with CLL, including those with high-risk genomic aberrations. We conducted a phase 1b/2, single-arm, open-label trial to evaluate the safety and efficacy of GI as first-line treatment in 32 CLL pts. We report the outcome in pts that discontinued ibrutinib (either after 3 years of sustained complete response (CR) as stipulated in the clinical protocol, or due to other reasons). CLL pts enrolled in this protocol were ≥65 years old, or unfit/unwilling to receive chemotherapy. Pts received GI for six cycles, followed by daily single-agent ibrutinib. The protocol was designed to ensure that pts with a sustained CR after 36 months were allowed to discontinue ibrutinib. The median age was 66 years (IQR 59-73), and 6% of the evaluated pts had 17p deletion. All pts were able to complete the six planned cycles of obinutuzumab. The combination regimen was well-tolerated, and the most common adverse events (>5% CTCAE grade 3-4) were neutropenia, thrombocytopenia, and hyperglycemia. The rate and severity of infusion-related reactions (IRR) were much lower than expected (Grade≥ 3, 3%), and pts without IRR had lower serum levels of cytokines/chemokines CCL3 (P=0.0460), IFN-γ (P=0.0457), and TNF-α (P=0.0032) after infusion. The overall response rate was 100%, with nine pts (28%) achieving a CR, and four pts (12.5%) with undetectable minimal residual disease (uMRD) in the bone marrow, defined as <10-4 CLL cells on multicolor flow cytometry. At a median follow-up of 35.5 months (IQR 24.5-42.7) after starting treatment, 91% of the enrolled pts remain in remission with a 100% overall survival. Sixteen pts have completed a long-term follow-up of 36 months. Six pts showed CR, with three of them achieving uMRD in the bone marrow. Ten of these pts were in PR, and only one had disease progression and started treatment for symptomatic stage I disease with obinutuzumab plus venetoclax. In total, thirteen pts (41%) have stopped ibrutinib, with a median time on treatment prior to discontinuation of 35 months. Five (16%) of these pts had CRs and discontinued after 36 months. Eight additional pts (25%) had PRs and discontinued ibrutinib without being eligible: three pts discontinued prior to 36 months due to toxicities, and five pts discontinued after 36 months (3 due to side effects, and 2 due to financially driven decision). One patient eligible to discontinue ibrutinib, decided to remain on treatment despite sustained CR. After a median follow up time following ibrutinib discontinuation of 8 months (IQR 3.5-17), only two out of 13 pts have progressed (10 and 17 months after Ibrutinib discontinuation). None of the pts that stopped ibrutinib after achieving a CR have shown signs of disease progression. Of note, the pharmaceutical sponsor provided ibrutinib for the first 36 months, after which pts or their insurer became financially responsible. This particular scenario could bias the discontinuation pattern compared to a real world experience. It also provided us with a perspective about diverse factors affecting the treatment choices of pts. In summary, the obinutuzumab plus ibrutinib combination therapy was well-tolerated, with a much lower IRR rate. Efficacy compares favorably with historical controls with all pts responding to therapy, no deaths associated with treatment or disease progression, and a longer than expected time-to-progression after discontinuation of ibrutinib. The rate of ibrutinib discontinuation was higher than reported in the literature, most likely influenced by the protocol design and financial decisions driven by the switch from sponsor-provided ibrutinib to insurance or self-paid medication. Our observations regarding safety, efficacy and lack of disease progression after ibrutinib discontinuation are encouraging, and warrant confirmation in long-term prospective studies. Clinicaltrials.gov Identifier NCT02315768. Funding: Pharmacyclics LLC. Disclosures Choi: AbbVie: Consultancy, Speakers Bureau. Amaya-Chanaga:AbbVie: Ended employment in the past 24 months, Other: Research performed while employed as an investigator of this study at UCSD.. Kipps:Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Castro:Kite Pharma: Research Funding; Pharmacyclics: Research Funding; Fate Therapeutics: Research Funding.

Evaluation of Somatic Hypermutation Status in Chronic Lymphocytic Leukemia (CLL) in the Era of Next Generation Sequencing.

Somatic hypermutation (SHM) status provides an important prognostic indicator for chronic lymphocytic leukemia (CLL), a very common type of mature B-cell leukemia. Owing to the adverse prognosis associated with an unmutated immunoglobulin heavy chain variable (IGHV) status, SHM testing is performed as a standard of care in CLL. Conventionally, SHM testing has been performed using labor intensive and primarily analog Sanger sequencing method following PCR amplification of the clonal immunoglobulin heavy chain gene rearrangements in CLL cells. In comparison, recent availability of next generation sequencing (NGS) allows more versatile detection and direct identification of clonal immunoglobulin gene rearrangements in neoplastic B-cell populations. The ability to identify specific clonal IGHV signature(s) in both baseline (diagnostic) and post-treatment settings enables unique clinical applications of NGS such as determination of SHM status, minimal residual disease (MRD) monitoring, clonal heterogeneity and B cell receptor IG stereotypy. We provide a review of current practices and recommendations for SHM determination using NGS including examples of difficult cases.

Utilizing Real-World Evidence (RWE) to Improve Care in Chronic Lymphocytic Leukemia: Challenges and Opportunities.

This review discusses important findings from real-world evidence (RWE) studies impacting the field of chronic lymphocytic leukemia (CLL), from prognostication to long-term management and sequencing of novel agents. RWE data, which represents a heterogeneous cohort of patients treated at non-academic centers and off-clinical trial, demonstrate several key differences between findings in randomized controlled trials (RCT) of novel agents in CLL. While toxicity and discontinuation rates are higher, survival outcomes are encouraging in clinical practice, with often equivalent outcomes from reduced-dose or time-limited therapy of drug. Though sequencing of novel agents lacks robust RCT data, RWE data provide important guidance for selection and sequencing of novel agents. RWE has critically informed our practice by providing diverse patient data and real-time analysis for important clinical questions outpacing the rapidly growing field of CLL.

Combined Inhibition of BCR and IGF1R Signaling Leads to Synergistic Apoptosis Induction in Primary CLL Cells in Vitro

Abstract Introduction: Chemoimmunotherapy has been the standard of care for chronic lymphocytic leukemia (CLL). However, novel therapeutic strategies targeting the B cell receptor (BCR) pathway like the BTK inhibitor ibrutinib and the PI3K delta inhibitor idelalisib have demonstrated superior results in clinical trials. Consequently, both substances have become standard in relapsed and refractory patients and have replaced conventional chemoimmunotherapy as treatment of choice in high-risk patients with deletion 17p or TP53 mutation. Despite their high clinical effectiveness, these drugs cannot achieve deep remissions as single agents and require continued treatment. Furthermore, first mechanisms of resistance such as BTK and PLCG mutations have been reported. The persistence of CLL under BCR signaling blockade could be explained by the activation of alternative pathways such as the insulin-like growth factor 1 receptor (IGF1R) pathway. In line, we have previously demonstrated IGF1R overexpression with concomitant IGF1R pathway activation in CLL patients and successful apoptosis induction by IGF1R inhibition in CLL cells. For solid tumors and multiple myeloma, the potential of IGF1R inhibition is currently being evaluated in clinical studies with the IGF1R inhibitor linsitinib. Here, we demonstrate synergistic effects on apoptosis induction by combined inhibition of BCR and IGF1R signaling. Methods and Results: To evaluate a possible benefit from combined inhibition of BCR and IGF1R, we cultured primary CLL cells with previously determined subtoxic concentrations of ibrutinib (4µM), idelalisib (5 µM) and the IGF1R antagonist linsitinib (OSI-906, 4 µM) alone and in combination. Cell viability was analyzed using flow cytometry with Annexin/PI staining 48 hours and 96 hours after treatment. In vitro treatment of CLL patient samples (n=5) with single-agent ibrutinib, idelalisib and linsitinib as well as with the combination of ibrutinib and idelalisib caused a decreased viability of 90 ± 8% after 48 hours compared to the untreated controls. In contrast, the effect of combined inhibitor treatment with linsitinib and either ibrutinib or idelalisib led to a marked but not significant decrease in viability to 76 ± 6 %. In order to assess treatment efficacy in the context of microenvironment interaction, CLL cells (n=6) were co-cultured with the murine stromal cell line M2-10B4, and treatment started after 24 hours. Again, single agent treatment and combined ibrutinib/idelalisib treatment resulted in a comparable reduction of viability to 89 ± 7% for ibrutinib, 77 ± 5% for idelalisib and 77 ± 6% for ibrutinib/idelalisib. Combined BCR and IGF1R pathway inhibition using linsitinib with either ibrutinib or idelalisib led to a significant decrease in cell viability to 53 ± 11% and 45 ± 8%, respectively. This effect was considerably more pronounced than expected from the single-agent treatments. It exerted the combined BTK/PI3K delta inhibition significantly in all of the performed experiments and proved consistent after 96h. Notably, the strong synergistic effect of apoptosis induction through BCR and IGF1R inhibition could also be observed in specimens from two high risk CLL patients harboring deletion 17p. CLL cell viability was reduced to 38 ± 9% for linsitinib/ibrutinib and 30 ± 2% for linsitinib/idelalisib, respectively, compared to 65 ± 3% for the combination of ibrutinib and idelalisib. Conclusion: In conclusion, we demonstrate that IGF1R inhibition constitutes a novel and effective therapeutic target for CLL therapy. We confirm previous data on effective apoptosis induction by IGF1R inhibition in CLL in vitro (Yaktapour N et al., Blood 2013;122:1621-1633) and demonstrate efficacy comparable to ibrutinib and idelalisib treatment. Combinations with the IGF1R inhibitor linsitinib show superior in vitro efficacy compared to single-agent treatment and to combined BTK/PI3K delta blockage. These results indicate synergistic effects of kinase inhibition, possibly due to blockage of (IGF1R) pathway recruitment. Current experiments are dissecting BCR and IGF1R pathway activity and testing IGF1R expression and phosphorylation as predictive biomarker. We therefore conclude that combined BCR/IGF1R inhibition is highly effective presumably leading to deep remissions, and we propose that translation of the in vitro data into clinical trials seems feasible. Disclosures No relevant conflicts of interest to declare.

News in the Supportive Care of Chronic Lymphocytic Leukemia

Patients with chronic lymphocytic leukemia have disrupted cellular and humoral immunity with quantitative and qualitative impairment of the cells of the immune system. Immunity disbalance leads to increased incidence of infections and autoimmune cytopenias. Supportive care for chronic lymphocytic leukemia focuses on prevention and treatment of these complications and consists of antimicrobial prophylaxis, substitution of immunoglobulins, immunosuppressive therapy, growth factors and blood transfusions.

Novel Therapies for Chronic Lymphocytic Leukemia: A Canadian Perspective.

Chronic lymphocytic leukemia (CLL) is the most common adult lymphoproliferative disorder in Western countries. The current standard of care for CLL is chemoimmunotherapy, typically with fludarabine, cyclophosphamide, and rituximab (FCR). However, most patients with CLL are elderly with comorbidities and are unable to tolerate FCR. In order to choose the best treatment for each individual patient, physicians must balance efficacy with toxicity. In addition, most currently available treatments are ineffective in CLL patients with loss of TP53. Two groups of novel therapeutic agents-anti-CD20 monoclonal antibodies and small molecule inhibitors-are attempting to address these issues, and 5 of these agents have progressed to phase 3 trials: obinutuzumab, idelalisib, ibrutinib, venetoclax (ABT-199), and duvelisib (IPI-145). We present the current evidence for these novel agents in the treatment of CLL, along with the perspectives of 4 Canadian oncology experts.

Entering the era of targeted therapy for chronic lymphocytic leukemia: impact on the practicing clinician.

Chemoimmunotherapy has been the standard of care for chronic lymphocytic leukemia (CLL). However, the introduction of B-cell receptor (BCR) kinase inhibitors such as ibrutinib has the potential to eliminate the role of chemotherapy in the treatment of CLL. How to best incorporate old and new therapies for CLL in this landscape is increasingly complex. This article reviews current data available to clinicians and integrates these data to provide a strategy that can be used to approach the treatment of CLL in the era of BCR signaling inhibitors. Current strategies separate patients based on age or functional status as well as genetics [presence or absence of del(17)(p13.1)]. In the era of targeted therapy, this will likely continue based on current available data. Phase III studies support chemoimmunotherapy as the initial standard therapy for patients without del(17)(p13.1). Choice of chemotherapy (fludarabine plus cyclophosphamide, bendamustine, or chlorambucil) and anti-CD20 antibody (rituximab, ofatumumab, or obinutuzumab) varies based on regimen and patient status. For patients with del(17)(p13.1), no standard initial therapy exists, although several options supported by phase II clinical trials (methylprednisolone plus alemtuzumab or ibrutinib) seem better than chemoimmunotherapy. Treatment of relapsed CLL seems to be best supported by ibrutinib-based therapy. Completion of trials with ibrutinib and other new agents in the near future will offer opportunity for chemotherapy-free treatment across all groups of CLL. Therapy for CLL has evolved significantly over the past decade with introduction of targeted therapy for CLL. This has the potential to completely transform how CLL is treated in the future.

Population-based characterization of the genetic landscape of chronic lymphocytic leukemia patients referred for cytogenetic testing in British Columbia, Canada: the role of provincial laboratory standardization

Detection of recurrent chromosome abnormalities by fluorescence in situ hybridization (FISH) is an essential component of care in chronic lymphocytic leukemia (CLL) patients. In the province of British Columbia (BC), Canada, population 4.6 million, CLL patients receive uniform evaluation and therapy with FISH testing performed in three jurisdictions. The aims of this study were to (i) validate CLL-FISH testing among the BC cytogenetic laboratories to ensure standardization of results and (ii) characterize population-level CLL-FISH abnormalities by pooling provincial data. From 2004 to 2011, 585 consecutive patients underwent pretreatment CLL-FISH testing at laboratory A (50.1%), laboratory B (32.3%), or laboratory C (17.6%). For validation purposes, 26 CLL-FISH abnormalities were tested by each laboratory's protocol, with 91% result concordance. Discordant results involved percent abnormalities at or near cutoff values; therefore, a 10% universal cutoff was established when pooling results. Applying the universal cutoff to the provincial cohort, CLL-FISH abnormalities were detected in 74.9%: 54.9% 13q-, 18.8% +12, 8.5% 11q-, and 7.7% 17p-. In this large population-based cohort of patients referred for CLL-FISH testing, frequencies of abnormalities detected by FISH analysis were highly consistent with those reported in single-institution and clinical trial populations. Provinces or districts that work together to care for CLL patients can effectively pool data with appropriate laboratory validation to ensure standardization of results.

Monitoring for cytomegalovirus and Epstein-Barr virus infection in chronic lymphocytic leukemia patients receiving i.v. fludarabine-cyclophosphamide combination and alemtuzumab as consolidation therapy

The combination of fludarabine and cyclophosphamide (FC) has become the standard of care in chronic lymphocytic leukemia (CLL) patients. Due to the well-recognized F-related immunosuppression,[1][1] a higher risk of opportunistic infections could be expected by adding another immunosuppressive agent