Targeting CD38 with daratumumab is lethal to Waldenström macroglobulinaemia cells

Targeting CD38 with monoclonal antibodies disrupts key survival pathways in paediatric Burkitt's lymphoma malignant B cells

Objectives

Paediatric Burkitt's lymphoma (pBL) is the most common childhood non-Hodgkin B-cell lymphoma. Despite the encouraging survival rates for most children, treating cases with relapse/resistance to current therapies remains challenging. CD38 is a transmembrane protein highly expressed in pBL. This study investigates the effectiveness of CD38-targeting monoclonal antibodies (mAbs), daratumumab and isatuximab, in impairing crucial cellular processes and survival pathways in pBL malignant cells.

Methods

In silico analyses of patient samples, combined with in vitro experiments using the Ramos cell line, were conducted to assess the impact of daratumumab and isatuximab on cellular proliferation, apoptosis and the phosphoinositide 3-kinase (PI3K) pathway.

Results

Isatuximab was found to be more effective than daratumumab in disrupting B-cell receptor signalling, reducing cellular proliferation and inducing apoptosis. Additionally, isatuximab caused a significant impairment of the PI3K pathway and induced metabolic reprogramming in pBL cells. The study also revealed a correlation between CD38 and MYC expression levels in pBL patient samples, suggesting CD38 involvement in key oncogenic processes.

Conclusion

The study emphasises the therapeutic potential of CD38-targeting mAbs, particularly isatuximab, in pBL.

Novel Approaches to Managing Patients with Relapsed and Refractory Waldenström Macroglobulinemia

PURPOSE OF REVIEW

Waldenström macroglobulinemia is a rare non-Hodgkin lymphoma (NHL) characterized by lymphoplasmacytic bone marrow infiltration associated with an immunoglobulin M (IgM) monoclonal gammopathy. Over the past two decades, a number of important novel therapies have emerged for the treatment of relapsed and refractory (R/R) WM. The purpose of this review is to discuss these novel agents.

RECENT FINDINGS

Chemoimmunotherapy which formed the basis treatment for R/R WM is slowly being replaced by novel targeted agents. These therapies, including Bruton's tyrosine kinase inhibitors, proteasome inhibitors, and B-cell lymphoma 2 inhibitors, have widened the landscape of management. Emerging therapies currently under investigation, such as bispecific T-cell engagers, chimeric antigen T-cell receptor therapy, and novel small molecule inhibitors, have additionally shown the potential to improve response and survival. The treatment of R/R WM has greatly evolved, in large part due to a greater understanding of the biology of WM, and the evaluation of novel targeted agents in the basket trials of NHL, showing early activity in the small WM cohorts. Combination regimens with these established and emerging novel therapies have the potential to further improve disease control and induce higher rates of deep responses. Strategies aimed at altering the disease trajectory would require randomized controlled trials to provide relevant data on optimal integration and sequencing of more effective and tolerable regimens earlier in the disease course.

AT-101 Enhances the Antitumor Activity of Lenalidomide in Patients with Multiple Myeloma

Bcl-2 and Mcl-1 proteins play a role in multiple myeloma (MM) cell survival, for which targeted inhibitors are being developed. AT-101 is an oral drug, which disrupts Bcl-2 and Mcl-1 function, impedes mitochondrial bioenergetic processes and induces apoptosis in MM cells. When combined with lenalidomide and dexamethasone (Rd), AT-101 significantly reduced tumor burden in an in vivo xenograft model of MM. These data provided rationale for a phase I/II study to establish the effective dose of AT-101 in combination with Rd (ARd regimen) in relapsed/refractory MM. A total of 10 patients were enrolled, most with high-risk cytogenetics (80%) and prior stem cell transplant (70%). Three patients were lenalidomide-refractory, 2 were bortezomib-refractory and 3 were daratumumab-refractory. The ARd combination was well tolerated with most common grade 3/4 adverse events being cytopenia's. The overall response rate was 40% and clinical benefit rate was 90%. The median progression free survival was 14.9 months (95% CI 7.1-NE). Patients responsive to ARd showed a decrease in Bcl-2:Bim or Mcl-1:Noxa protein complexes, increased CD8+ T and NK cells and depletion of T and B-regulatory cells. The ARd regimen demonstrated an acceptable safety profile and promising efficacy in patients with relapsed/refractory MM prompting further investigation in additional patients.

Lisaftoclax (APG-2575) Is a Novel BCL-2 Inhibitor with Robust Antitumor Activity in Preclinical Models of Hematologic Malignancy

PURPOSE

Development of B-cell lymphoma 2 (BCL-2)-specific inhibitors poses unique challenges in drug design because of BCL-2 homology domain 3 (BH3) shared homology between BCL-2 family members and the shallow surface of their protein-protein interactions. We report herein discovery and extensive preclinical investigation of lisaftoclax (APG-2575).

EXPERIMENTAL DESIGN

Computational modeling was used to design "lead" compounds. Biochemical binding, mitochondrial BH3 profiling, and cell-based viability or apoptosis assays were used to determine the selectivity and potency of BCL-2 inhibitor lisaftoclax. The antitumor effects of lisaftoclax were also evaluated in several xenograft models.

RESULTS

Lisaftoclax selectively binds BCL-2 (Ki < 0.1 nmol/L), disrupts BCL-2:BIM complexes, and compromises mitochondrial outer membrane potential, culminating in BAX/BAK-dependent, caspase-mediated apoptosis. Lisaftoclax exerted strong antitumor activity in hematologic cancer cell lines and tumor cells from patients with chronic lymphocytic leukemia, multiple myeloma, or Waldenström macroglobulinemia. After lisaftoclax treatment, prodeath proteins BCL-2‒like protein 11 (BIM) and Noxa increased, and BIM translocated from cytosol to mitochondria. Consistent with these apoptotic activities, lisaftoclax entered malignant cells rapidly, reached plateau in 2 hours, and significantly downregulated mitochondrial respiratory function and ATP production. Furthermore, lisaftoclax inhibited tumor growth in xenograft models, correlating with caspase activation, poly (ADP-ribose) polymerase 1 cleavage, and pharmacokinetics of the compound. Lisaftoclax combined with rituximab or bendamustine/rituximab enhanced antitumor activity in vivo.

CONCLUSIONS

These findings demonstrate that lisaftoclax is a novel, orally bioavailable BH3 mimetic BCL-2-selective inhibitor with considerable potential for the treatment of certain hematologic malignancies.

Effect of CD38 on B-cell function and its role in the diagnosis and treatment of B-cell-related diseases

CD38 is a multifunctional receptor and enzyme present on the surface of B lymphocytes, which can induce B lymphocytes proliferation and apoptosis by crosslinking related cytokines to affect the function of B cells, thus affecting immune regulation in humans and promoting tumorigenesis. The level of CD38 expression in B cells has become an important factor in the clinical diagnosis, treatment, and prognosis of malignant tumors and other related diseases. Therefore, studying the relationship between CD38 expression on the surface of B cells and the occurrence of the disease is of great significance for elucidating its association with disease pathogenesis and the clinical targeted therapy. In this paper, we review the effects of CD38 on B-cell activation, proliferation, and differentiation, and elaborate the functional role and mechanism of CD38 expression on B cells. We also summarize the relationship between the level of CD38 expression on the surface of B cells and the diagnosis, treatment, and prognosis of various diseases, as well as the potential use of targeted CD38 treatment for related diseases. This will provide an important theoretical basis for the scientific research and clinical diagnosis and treatment of B-cell-related diseases.

Post-relapse survival in Waldenstrom macroglobulinemia patients experiencing therapy failure following autologous transplantation

Waldenström macroglobulinemia (WM) is a rare B-cell lymphoproliferative malignancy. Autologous hematopoietic cell transplantation (auto-HCT) is considered in a subset of WM patients with relapsed disease. While registry data has shown a benefit for auto-HCT in relapsed WM, there is a paucity of data on outcomes of patients relapsing after auto-HCT. Eligibility criteria included adult patients with relapsed/refractory WM who underwent auto-HCT between 2007 and 2017. The primary endpoint was post-relapse overall survival (PR-OS). Secondary endpoints were to identify factors prognostic of PR-OS. Of the 48 patients with WM who underwent auto-HCT, 22 (46%) experienced relapse following auto-HCT. Median PR-OS of relapsed WM patients after auto-HCT (n = 22) was not reached (NR) (95% confidence interval [CI]: 17.5 months-NR). Among patients who relapsed <1 year versus ≥1 year from auto-HCT, the median PR-OS was 18.4 months (95%CI: 0.8-NR) months and NR (95%CI: 17.5-NR), respectively (p = 0.06). Of note, disease status at the time of transplant, CR/VGPR versus partial remission did not appear to impact PR-OS. The median PR-OS was significantly longer in patients who received ibrutinib in the post-transplant setting compared to those who did not (NR vs. 18.4 months, 95%CI: 9.1-NR, p = 0.02). On univariable analysis, the presence of complex karyotype (RR = 4.87, 95% CI = 1.22-19.53) and a higher number of prior lines of therapy (RR = 1.81, 95% CI = 1.23-2.67) were associated with a significantly higher risk of relapse. This is the only study to date that evaluated outcomes of WM patients who relapsed following auto-HCT and provides a benchmark for future trials evaluating survival following auto-HCT relapse.

Targeting CD38 is lethal to Breg-like chronic lymphocytic leukemia cells and Tregs, but restores CD8+ T-cell responses

Patients with chronic lymphocytic leukemia (CLL) are characterized by monoclonal expansion of CD5+CD23+CD27+CD19+κ/λ+ B lymphocytes and are clinically noted to have profound immune suppression. In these patients, it has been recently shown that a subset of B cells possesses regulatory functions and secretes high levels of interleukin 10 (IL-10). Our investigation identified that CLL cells with a CD19+CD24+CD38hi immunophenotype (B regulatory cell [Breg]-like CLL cells) produce high amounts of IL-10 and transforming growth factor β (TGF-β) and are capable of transforming naive T helper cells into CD4+CD25+FoxP3+ T regulatory cells (Tregs) in an IL-10/TGF-β-dependent manner. A strong correlation between the percentage of CD38+ CLL cells and Tregs was observed. CD38hi Tregs comprised more than 50% of Tregs in peripheral blood mononuclear cells (PBMCs) in patients with CLL. Anti-CD38 targeting agents resulted in lethality of both Breg-like CLL and Treg cells via apoptosis. Ex vivo, use of anti-CD38 monoclonal antibody (mAb) therapy was associated with a reduction in IL-10 and CLL patient-derived Tregs, but an increase in interferon-γ and proliferation of cytotoxic CD8+ T cells with an activated phenotype, which showed an improved ability to lyse patient-autologous CLL cells. Finally, effects of anti-CD38 mAb therapy were validated in a CLL-patient-derived xenograft model in vivo, which showed decreased percentage of Bregs, Tregs, and PD1+CD38hiCD8+ T cells, but increased Th17 and CD8+ T cells (vs vehicle). Altogether, our results demonstrate that targeting CD38 in CLL can modulate the tumor microenvironment; skewing T-cell populations from an immunosuppressive to immune-reactive milieu, thus promoting immune reconstitution for enhanced anti-CLL response.

Flow cytometric evaluation of CD38 expression levels in the newly diagnosed T-cell acute lymphoblastic leukemia and the effect of chemotherapy on its expression in measurable residual disease, refractory disease and relapsed disease: an implication for anti-CD38 immunotherapy

Background

Recently, anti-CD38 monoclonal antibody (Mab) therapy has become a focus of attention as an additional/alternative option for many hematological neoplasms including T-cell acute lymphoblastic leukemia (T-ALL). It has been shown that antitumor efficacy of anti-CD38-Mab depends on the level of CD38 expression on tumor cells. Reports on CD38 expression in T-ALL are scarce, and data on the effect of cytotoxic chemotherapy on CD38 expression are limited to very few samples. Moreover, it lacks entirely in refractory disease and in adult T-ALL. We report the flow cytometric evaluation of CD38 expression in T-ALL blasts at diagnosis and the effect of cytotoxic chemotherapy on its expression in measurable residual disease (MRD), refractory disease (MRD≥5%), and relapsed disease in a large cohort of T-ALL.

Methods

The study included 347 samples (188 diagnostic, 100 MRD, 24 refractory and 35 relapse samples) from 196 (children: 85; adolescents/adults: 111) patients with T-ALL. CD38-positive blasts percentages (CD38-PBPs) and expression-intensity (mean fluorescent intensity, CD38-MFI) were studied using multicolor flow cytometry (MFC). MFC-based MRD was performed at the end-of-induction (EOI-MRD, day 30–35) and end-of-consolidation (EOC-MRD, day 78–85) subsequent follow-up (SFU-MRD) points.

Results

Patients were classified into early thymic precursor subtype of T-ALL (ETPALL, 54/188, 28.7%), and non-ETPALL (134/188, 71.3%). Of 188, EOI-MRD assessment was available in 152, EOC-MRD was available in 96 and SFU-MRD was available in 14 patients. CD38 was found positive in 97.9% (184/188) of diagnostic, 88.7% (110/124) MRD (including 24-refractory) and 82.9% (29/35) relapsed samples. Median (95% CI) of CD38-PBPs/MFI in diagnostic, MRD, refractory, and relapsed T-ALL samples were, respectively, 85.9% (82.10%–89.91%)/4.2 (3.88–4.47), 74.0% (58.87%–83.88%)/4.6 (3.67–6.81), 79.6% (65.25%–96.11%)/4.6 (3.33–8.47) and 85.2% (74.48%–93.01%)/5.6 (4.14–8.99). No significant difference was noted in CD38 expression between pediatric versus adult and patients with ETPALL versus non-ETPALL. No change was observed in CD38-MFI between diagnostic versus MRD and diagnostic versus relapsed paired samples. However, we noticed a mild drop in the CD38-PBPs in MRD samples compared with the diagnostic samples (p=0.016).

Conclusion

We report an in-depth analysis of CD38 expression in a large cohort of T-ALL at diagnosis, during chemotherapy, and at relapse. Our data demonstrated that CD38 is robustly expressed in T-ALL blasts with a little effect of cytotoxic chemotherapy making it a potentially effective target for antiCD38-Mab therapy.

The Circular Life of Human CD38: From Basic Science to Clinics and Back

Monoclonal antibodies (mAbs) were initially considered as a possible “magic bullet” for in vivo elimination of tumor cells. mAbs represented the first step: however, as they were murine in nature (the earliest experience on the field), they were considered unfit for human applications. This prompted the development of techniques for cloning the variable regions of conventional murine antibodies, genetically mounted on human IgG. The last step in this years-long process was the design for the preparation of fully human reagents. The choice of the target molecule was also problematic, since cancer-specific targets are quite limited in number. To overcome this obstacle in the planning phases of antibody-mediated therapy, attention was focused on a set of normal molecules, whose quantitative distribution may balance a tissue-dependent generalized expression. The results and clinical success obtained with anti-CD20 mAbs revived interest in this type of strategy. Using multiple myeloma (MM) as a tumor model was challenging first of all because the plasma cells and their neoplastic counterpart eluded the efforts of the Workshop on Differentiation Antigens to find a target molecule exclusively expressed by these cells. For this reason, attention was turned to surface molecules which fulfill the requisites of being reasonably good targets, even if not specifically restricted to tumor cells. In 2009, we proposed CD38 as a MM target in virtue of its expression: it is absent on early hematological progenitors, has variable but generalized limited expression by normal cells, but is extremely high in plasma cells and in myeloma. Further, regulation of its expression appeared to be dependent on a variety of factors, including exposure to all-trans retinoic acid (ATRA), a potent and highly specific inducer of CD38 expression in human promyelocytic leukemia cells that are now approved for in vivo use. This review discusses the history of human CD38, from its initial characterization to its targeting in antibody-mediated therapy of human myeloma.

Novel tumor-targeted liposomes comprised of an MDM2 antagonist plus proteasome inhibitor display anti-tumor activity in a xenograft model of bortezomib-resistant Waldenstrom macroglobulinemia

Targeted drug delivery remains an active area of investigation in hematologic cancers. We have previously reported on a novel nanoparticle formulation (D1X) that can encapsulate drugs within a liposome whose lipid bilayer contains dexamethasone, which serves as a targeting ligand for drug delivery to tumor cells that express glucocorticoid receptors. We tested the activity of D1X-encapsulated bortezomib (D1XB) in combination with D1X-encapsulated nutlin (D1XN) in B-lymphoma/Waldenstrom macroglobulinemia (WM) cells. WM cells treated with D1XB + D1XN experienced cell cycle arrest, ER stress and apoptosis. In mice xenografted with bortezomib-resistant WM cells, D1XB + D1XN treatment resulted in significantly lower tumor burden compared to vehicle or nonliposomal parent drugs. In vivo biodistribution studies showed minimal uptake of D1X-based drugs in normal mice tissues. Our studies demonstrate that highly targeted delivery of both bortezomib and nutlin encapsulated in D1X nanoparticles are cytotoxic to and delay in vivo growth of bortezomib-resistant WM cells.

What is new in the treatment of Waldenstrom macroglobulinemia?

Waldenstrom macroglobulinemia (WM) is a rare type of non-Hodgkin lymphoma. The diagnosis of WM is established by the presence of lymphoplasmacytic lymphoma in the bone marrow or other organs, a monoclonal IgM paraproteinemia and the recurrent MYD88 L265P somatic mutation. Some patients with WM can be asymptomatic, in which case treatment is not indicated. However, most patients with WM will become symptomatic during the course of the disease, due to anemia, hyperviscosity, neuropathy, or other processes, necessitating therapy. Current treatment options for symptomatic WM patients include alkylating agents, proteasome inhibitors and anti-CD20 monoclonal antibodies. The approval of the oral Bruton tyrosine kinase (BTK) inhibitor ibrutinib alone and in combination with rituximab has expanded the treatment options for WM patients. The present Perspective would focus on exciting treatment strategies under development for WM patients, such as proteasome inhibitors (e.g., ixazomib), BTK inhibitors (e.g., acalabrutinib, zanubrutinib, vecabrutinib), BCL2 inhibitors (e.g., venetoclax), and anti-CXCR4 antibodies (e.g., ulocuplumab), among others. It is certainly an exciting time for WM therapy development with novel and promising treatment options in the horizon.