Treatment of Chronic Lymphocytic Leukemia With del(17p)/TP53 Mutation: Allogeneic Hematopoietic Stem Cell Transplantation or BCR-Signaling Inhibitors?

Six-year follow-up and subgroup analyses of a phase 2 trial of venetoclax for del(17p) chronic lymphocytic leukemia

ABSTRACT

Chromosome 17p deletion (del[17p]) is associated with poor prognosis in patients with chronic lymphocytic leukemia (CLL). Venetoclax is approved for treatment of previously untreated and relapsed/refractory (R/R) CLL, including patients with del(17p), based on the open-label, multicenter, phase 2 M13-982 trial (NCT01889186). Here, we detail the 6-year follow-up analysis for M13-982. A total of 158 patients with previously untreated (n = 5) or R/R (n = 153) del(17p) CLL received 400 mg venetoclax daily after initial ramp-up until progressive disease. After a median follow-up of 70 months, the best objective response rate (ORR) was 77% (21% complete remission [CR] and 49% partial remission [PR]), with a median duration of response (DOR) of 39.3 months (95% confidence interval [CI], 31.1-50.5). The median progression-free survival (PFS) was 28.2 months (95% CI, 23.4-37.6), and median overall survival (OS) was 62.5 months (95% CI, 51.7-not reached), with 16% of patients remaining on treatment after 6 years. Multivariable analysis did not identify statistically significant correlation between patient subgroups defined by clinical or laboratory variables and ORR or PFS. The most common grade ≥3 adverse events were neutropenia (42%), infections (33%), anemia (16%), and thrombocytopenia (16%). Post hoc comparative analyses of PFS and OS from treatment initiation, from a 24-month landmark, and by minimal residual disease status were performed between patients with del(17p) in the M13-982 and MURANO studies in the interest of understanding these data in another context. These long-term data show the continued benefits of venetoclax in patients with del(17p) CLL. The trial was registered at www.clinicaltrials.gov as #NCT01889186.

Application of Drug Repurposing-Based Precision Medicine Platform for Leukaemia Patient Treatment

Drug resistance in leukaemia is a major problem that needs to be addressed. Precision medicine provides an avenue to reduce drug resistance through a personalised treatment plan. It has helped to better stratify patients based on their molecular profile and therefore improved the sensitivity of patients to a given therapeutic regimen. However, therapeutic options are still limited for patients who have already been subjected to many lines of chemotherapy. The process of designing and developing new drugs requires significant resources, including money and time. Drug repurposing has been explored as an alternative to identify effective drug(s) that could be used to target leukaemia and lessen the burden of drug resistance. The drug repurposing process usually includes preclinical studies with drug screening and clinical trials before approval. Although most of the repurposed drugs that have been identified are generally safe for leukaemia treatment, they seem not to be good candidates for monotherapy but could have value in combination with other drugs, especially for patients who have exhausted therapeutic options. In this review, we highlight precision medicine in leukaemia and the role of drug repurposing. Specifically, we discuss the several screening methods via chemoinformatic, in vitro, and ex vivo that have facilitated and accelerated the drug repurposing process.

Allogeneic hematopoietic cell transplantation after prior targeted therapy for high-risk chronic lymphocytic leukemia

Allogeneic hematopoietic cell transplantation (alloHCT) can cure previously treated high-risk chronic lymphocytic leukemia (CLL) patients if they are suitable for transplant through the graft-versus-leukemia effect. However, since the emergence of targeted therapies, the role of alloHCT for high-risk CLL is less clear. To address this question, we evaluated 108 high-risk CLL patients who underwent alloHCT from 2010 to 2018. Thirty patients from the period of 2013 to 2018 received targeted therapy prior to alloHCT. The median age for the targeted therapy cohort was 60 years (range, 30-71 years), and 20% and 73% had complete and partial remission, respectively: 76% had del(17p), 46.2% had 5 or more cytogenetic abnormalities, and 78.9% were IGHV unmutated. The median number of prior therapies was 4 (range, 1-9). With a median follow-up time of 36 months (range, 10-72 months), the 3-year overall (OS) and progression-free survival (PFS) were 87% and 69%, respectively. The 3-year cumulative incidence of nonrelapse mortality and relapse was 7% and 24%, respectively. For the control cohort of 78 patients who underwent alloHCT from 2010 to 2014 and received only chemoimmunotherapy prior to transplant, the 3-year OS and PFS were 69% and 58%, respectively. Patients treated with targeted therapy prior to alloHCT had a significantly higher number of circulating T and B cells and a lower ratio of CD4 regulatory T cells to CD4 conventional T cells early after transplant. In summary, despite multiple high-risk features, the clinical outcome of CLL patients who receive targeted therapy prior to transplant is excellent and alloHCT should be offered while the disease is under control.

Detection of somatic TP53 mutations and 17p deletions in patients with chronic lymphocytic leukemia: a review of the current methods

Chronic lymphocytic leukemia is the most common hematologic malignancy among adults in Western countries. Several studies show that somatic mutations in the TP53 gene are present in up to 50% of patients with relapsed or refractory chronic lymphocytic leukemia. This study aims to review and compare the methods used to detect somatic TP53 mutations and/or 17p deletions and analyze their importance in the chronic lymphocytic leukemia diagnosis and follow-up. In chronic lymphocytic leukemia patients with refractory or recurrent disease, the probability of clonal expansion of cells with the TP53 mutation and/or 17p deletion is very high. The studies assessed showed several methodologies able to detect these changes. For the 17p deletion, the chromosome G-banding (karyotype) and interphase fluorescence in situ hybridization are the most sensitive. For somatic mutations involving the TP53 gene, moderate or high-coverage read next-generation sequencing and Sanger sequencing are the most recommended ones. The TP53 gene mutations represent a strong adverse prognostic factor for patient survival and treatment resistance in chronic lymphocytic leukemia. Patients carrying low-proportion TP53 mutation (less than 20–25% of all alleles) remain a challenge to these tests. Thus, for any of the methods employed, it is essential that the laboratory conduct its analytical validation, documenting its accuracy, precision and sensitivity/limit of detection.

Venetoclax: evidence to date and clinical potential

The emergence of targeted therapy for patients with hematological diseases has permanently altered the therapeutic landscape. Immunochemotherapy regimes are now more and more being replaced by targeted therapies due to superior efficacy and better safety profiles. However, evolution and selection of subclones with continuous treatment leads to disease relapse and resistance toward these novel drugs. Venetoclax, the highly selective BCL-2 inhibitor (ABT-199), has an acceptable safety profile. To date, it has been approved for the treatment of first-line and relapsed/refractory chronic lymphocytic leukemia (CLL) and acute myeloid leukemia (AML). However, extension of indications can be expected in monotherapy and in combination regimens with promising outcomes in other hematological diseases. In this article, we describe the mechanism of action that stands behind the efficacy of venetoclax and provide a summary of available results from clinical trials.

Association of SLC28A3 Gene Expression and CYP2B6*6 Allele with the Response to Fludarabine Plus Cyclophosphamide in Chronic Lymphocytic Leukemia Patients

Fludarabine plus cyclophosphamide (FC) chemotherapy is the basis of treatment protocols used in management of chronic lymphocytic leukemia (CLL). In some patients, response to therapy may be affected by aberrant function of genes involved in pharmacokinetics and pharmacodynamics of the drugs. The aim of this research was to assess the impact of pharmacogenetic variability, namely expression of SLC28A3 gene and the presence of CYP2B6*6 variant allele, on the FC treatment efficacy. Forty-four CLL patients with functional TP53 gene at the time of FC initiation were enrolled in this study. CYP2B6 genotyping was performed by polymerase chain reaction and direct sequencing. SLC28A3 expression was measured by quantitative reverse-transcriptase polymerase chain reaction. Significantly higher pretreatment levels of SLC28A3 mRNA were detected in patients who failed to respond to FC in comparison to patients who achieved complete and partial response (p = 0.01). SLC28A3 high-expressing cases were almost ten times more likely not to respond to FC than low-expressing cases (OR = 9.8; p = 0.046). However, association of SLC28A3 expression with progression-free survival (PFS) and overall survival (OS) was not observed. CYP2B6*6 allele, detected in 24 patients (54.6%), exerted no association with the attainment of response to FC, as well as with PFS and OS. The results of this study demonstrate that SLC28A3 expression is a significant predictor of FC efficacy in CLL patients with intact TP53. Elevated SLC28A3 mRNA levels are associated with inferior short-term response to FC, suggesting that, if validated on larger cohorts, SLC28A3 expression may become a biomarker useful for pretreatment stratification of patients.

High-risk chronic lymphocytic leukemia in the era of pathway inhibitors: integrating molecular and cellular therapies

High-risk chronic lymphocytic leukemia (CLL) has been defined by clinical and/or genetic resistance (TP53 abnormalities) to treatment with chemoimmunotherapy (CIT). With the availability of pathway inhibitors (PIs), such as kinase inhibitors and BCL2 antagonists, the outlook of CIT-resistant patients has dramatically improved. Here, we propose a revision of the concept of high-risk CLL, driven by TP53 abnormalities and response to treatment with PI. CLL high-risk-I, CIT-resistant is defined by clinically CIT-resistant disease with TP53 aberrations, but fully responsive to PI. This category is largely the domain of PI-based therapy, and cellular therapy (ie, allogeneic hematopoietic cell transplantation) remains an option only in selected patients with low individual procedure-related risk. In CLL high-risk-II, CIT- and PI-resistant, characterized by increasing exhaustion of pharmacological treatment possibilities, cellular therapies (including chimeric antigen receptor-engineered T cells) should be considered in patients eligible for these procedures. Moreover, molecular and cellular therapies are not mutually exclusive and could be used synergistically to exploit their full potential.

How and when I do allogeneic transplant in CLL

Allogenic stem cell transplantation (allo-SCT) has been considered the treatment of choice for high-risk patients with chronic lymphocytic leukemia (CLL) and the only approach offered with curative intent in this disease. The availability novel agents, including the B-cell receptor inhibitors ibrutinib, acalabrutinib, and idelalisib, as well as venetoclax, which targets the BCL2 pathway, and the success of these agents in treating high-risk disease patients have made it more difficult to assess who should be considered for allo-SCT and when in the treatment course. In this review, I will discuss the different treatment options available for the treatment of high-risk CLL and how allo-SCT fits into the treatment algorithm in the era of novel agents.

Venetoclax for Patients With Chronic Lymphocytic Leukemia With 17p Deletion: Results From the Full Population of a Phase II Pivotal Trial

Purpose Venetoclax is an orally bioavailable B-cell lymphoma 2 inhibitor. US Food and Drug Administration and European Medicines Agency approval for patients with 17p deleted relapsed/refractory chronic lymphocytic leukemia [del(17p) CLL] was based on results from 107 patients. An additional 51 patients were enrolled in a safety expansion cohort. Extended analysis of all enrolled patients, including the effect of minimal residual disease (MRD) negativity on outcome, is now reported. Patients and Methods Overall, 158 patients with relapsed/refractory or previously untreated (n = 5) del(17p) CLL received venetoclax 400 mg per day after an initial dose ramp up. Responses were based on 2008 International Workshop on Chronic Lymphocytic Leukemia criteria, with monthly physical exams and blood counts. Computed tomography scan was mandatory at week 36, after which assessment made was by clinical evaluation. Marrow biopsy was performed when complete remission was suspected. MRD was assessed by flow cytometry. Results Patients had a median of two prior therapies (range, zero to 10 therapies), 71% had TP53 mutation, and 48% had nodes that were ≥ 5 cm. Median time on venetoclax was 23.1 months (range, 0 to 44.2 months) and median time on study was 26.6 months (range, 0 to 44.2 months). For all patients, investigator-assessed objective response rate was 77% (122 of 158 patients; 20% complete remission) and estimated progression-free survival at 24 months was 54% (95% CI, 45% to 62%). For 16 patients who received prior kinase inhibitors, objective response rate was 63% (10 of 16 patients) and 24-month progression-free survival estimate was 50% (95% CI, 25% to 71%). By intent-to-treat analysis, 48 (30%) of 158 patients achieved MRD below the cutoff of 10^-4 in blood. Common grade 3 and 4 adverse events were hematologic and managed with supportive care and/or dose adjustments. Conclusion Venetoclax achieves durable responses and was well tolerated in patients with del(17p) CLL. A high rate of blood MRD < 10^-4 was achieved in this high-risk population.

iwCLL guidelines for diagnosis, indications for treatment, response assessment, and supportive management of CLL

The previous edition of the consensus guidelines of the International Workshop on Chronic Lymphocytic Leukemia (iwCLL), published in 2008, has found broad acceptance by physicians and investigators caring for patients with CLL. Recent advances including the discovery of the genomic landscape of the disease, the development of genetic tests with prognostic relevance, and the detection of minimal residual disease (MRD), coupled with the increased availability of novel targeted agents with impressive efficacy, prompted an international panel to provide updated evidence- and expert opinion-based recommendations. These recommendations include a revised version of the iwCLL response criteria, an update on the use of MRD status for clinical evaluation, and recommendations regarding the assessment and prophylaxis of viral diseases during management of CLL.

Ibrutinib as a bridge to transplant in high-risk chronic lymphocytic leukemia: A case report and review of the literature

The treatment landscape of chronic lymphocytic leukemia (CLL) has been challenged by the advent of novel classes of drugs, such as B-cell receptor (BCR)-inhibitors and BCL-2 antagonists. In selected high-risk patients, the choice to start allogeneic hematopoietic stem cell transplantation (alloHCT) or continue these agents is a matter of debate. Furthermore, published data about the impact on the feasibility of alloHCT and the optimal timing of administration are limited. Here we present a case of relapsed TP53 mutated CLL treated with ibrutinib as a bridge to alloHCT, discussing risks and benefits of different treatment options in a “real life” situation.

A rare case of atypical chronic lymphocytic leukaemia presenting as nephrotic syndrome

Chronic lymphocytic leukaemia (CLL) is characterised by a lymphocytosis of mature-appearing clonal CD5+, CD23+ B lymphocytes. CLL cells arise from the bone marrow and infiltrate lymphoid tissues such as lymph nodes and spleen. Presentation is usually through discovery of lymphocytosis or lymphadenopathy. Unusual presentations, especially paraneoplastic syndromes are rare. Here, we describe a rare case presenting with severe nephrotic syndrome associated with the presence of a monoclonal protein in serum. Workup for suspected plasma cell dyscrasia led instead to the diagnosis of bone marrow infiltration by atypical CLL without lymphocytosis. Renal biopsy showed a glomerulonephritis that turned out to be paraneoplastic as it went into remission after treatment for CLL. Our case shows an unusual presentation of CLL and prompts for increased awareness of lymphoproliferative disorders in the context of seemingly unrelated conditions that may be paraneoplastic in origin.

Advances in Monitoring Cell-Based Therapies with Magnetic Resonance Imaging: Future Perspectives

Cell-based therapies are currently being developed for applications in both regenerative medicine and in oncology. Preclinical, translational, and clinical research on cell-based therapies will benefit tremendously from novel imaging approaches that enable the effective monitoring of the delivery, survival, migration, biodistribution, and integration of transplanted cells. Magnetic resonance imaging (MRI) offers several advantages over other imaging modalities for elucidating the fate of transplanted cells both preclinically and clinically. These advantages include the ability to image transplanted cells longitudinally at high spatial resolution without exposure to ionizing radiation, and the possibility to co-register anatomical structures with molecular processes and functional changes. However, since cellular MRI is still in its infancy, it currently faces a number of challenges, which provide avenues for future research and development. In this review, we describe the basic principle of cell-tracking with MRI; explain the different approaches currently used to monitor cell-based therapies; describe currently available MRI contrast generation mechanisms and strategies for monitoring transplanted cells; discuss some of the challenges in tracking transplanted cells; and suggest future research directions.