Potent in vitro and in vivo activity of an Fc-engineered anti-CD19 monoclonal antibody against lymphoma and leukemia

Tafasitamab for the treatment of patients with diffuse large B-cell lymphoma

Patients with relapsed or refractory (R/R) diffuse large B-cell lymphoma (DLBCL) require additional treatments, especially those not eligible or not responding to high dose cytotoxic chemotherapy and stem cell transplantation. Over the last few years, several new treatments have been developed and approved for these patients, among them of particular relevance are those targeting CD19. Tafasitamab is a humanized monoclonal antibody targeting CD19, composed of a modified fragment crystallizable (Fc) region engineered with higher affinity for Fc gamma receptors (FcγR) receptors, leading to increased cytotoxicity through natural killer cells and macrophages (antibody-dependent cellular cytotoxicity and antibody-dependent cell-mediated phagocytosis). In this product review, we will discuss its mechanism of action, safety profile and efficacy results from clinical trials that led to its approval in combination with lenalidomide for patients with R/R DLBCL ineligible for high-dose chemotherapy and autologous transplantation.

Outcome of patients with large B-cell lymphoma treated with tafasitamab plus lenalidomide either before or after CAR T-cell therapy

ABSTRACT

Tafasitamab plus lenalidomide (TAFA-LEN) treatment relevance pre- or post-anti-CD19 chimeric antigen receptor (CAR) T-cell therapy is debated. We analyzed patients with large B-cell lymphoma in the DESCAR-T registry treated with axi[1]cel or tisa-cel in ≥3rd line and TAFA-LEN before (n = 15, "TL-pre-CAR-T" set) or directly after (n = 52, "TL-post-CAR-T" set) CAR T-cell therapy. We compared TAFA-LEN v. other treatments using inverse probability weighting in the TL-post-CAR[1]T set. In the TL-post-CAR-T set, the median progression-free survival (mPFS), overall survival (mOS), and duration of response (mDOR) since the first treatment for progression (mPFS2/mOS2/mDOR2) were 3, 4.7, and 8.1 months, respectively. The best overall response rate (bORR) and best complete response rate (bCRR) after TAFA-LEN were 13.5% and 7.7%, respectively. Outcomes were better for patients who relapsed >6 months after CAR T-cell therapy (mPFS2: 5.6 vs 2 months, P = .0138; mOS2: not reached vs 3.8 months, P = .0034). The bORR and bCRR between TAFA-LEN and other treatments were 20.6% vs 24.9% and 11.6% vs 15.6%, respectively. Outcomes were similar between TAFA-LEN and other treatments (mPFS2: 2.9 vs 2.4 months, P = .91; mOS2: 3.3 vs 5.5 months, P = .06). In an exploratory analysis of the TL-pre-CAR-T set, the median TAFA-LEN treatment duration before CAR-T was 3.7 months with no patient becoming CD19 negative. The bORR, bCRR, 6- month PFS, and OS rates after CAR T-cell infusion were 45.5%, 36.4%, 20.1%, and 58.2%, respectively. Neither TAFA-LEN nor comparative salvage treatment improved outcomes for patients relapsing after CAR T-cell therapy.

Therapeutic antibodies in oncology: an immunopharmacological overview

The biotechnological development of monoclonal antibodies and their immunotherapeutic use in oncology have grown exponentially in the last decade, becoming the first-line therapy for some types of cancer. Their mechanism of action is based on the ability to regulate the immune system or by interacting with targets that are either overexpressed in tumor cells, released into the extracellular milieu or involved in processes that favor tumor growth. In addition, the intrinsic characteristics of each subclass of antibodies provide specific effector functions against the tumor by activating antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, and antibody-dependent cellular phagocytosis, among other mechanisms. The rational design and engineering of monoclonal antibodies have improved their pharmacokinetic and pharmacodynamic features, thus optimizing the therapeutic regimens administered to cancer patients and improving their clinical outcomes. The selection of the immunoglobulin G subclass, modifications to its crystallizable region (Fc), and conjugation of radioactive substances or antineoplastic drugs may all improve the antitumor effects of therapeutic antibodies. This review aims to provide insights into the immunological and pharmacological aspects of therapeutic antibodies used in oncology, with a rational approach at molecular modifications that can be introduced into these biological tools, improving their efficacy in the treatment of cancer.

Recent developments in CD19-targeted therapies for follicular lymphoma

INTRODUCTION

CD19 has emerged as an important and novel therapeutic target in follicular lymphoma. CD19-directed therapies, including monoclonal antibodies, bispecific antibodies, and CAR T-cell therapies, offer promising avenues for treating follicular lymphoma and improving outcomes.

AREAS COVERED

We review the role and rationale of targeting CD19 in follicular lymphoma and different interventions of CD19 targeting, such as cell therapy, bispecific antibodies, antibody-drug conjugates, and monoclonal antibodies. We finalize with a discussion on how these therapies may influence the treatment landscape of follicular lymphoma.

EXPERT OPINION

CD19 is an attractive target for therapeutic development in follicular lymphoma. Given its effectiveness, it will continue to move forward as a promising therapy for this disease.

The future of immunotherapy for diffuse large B-cell lymphoma

With the introduction of anti-CD19 chimeric antigen receptor (CAR) T-cell (CAR T) therapies, bispecific CD3/CD20 antibodies and anti-CD19 antibodies, immunotherapy continues to transform the treatment of diffuse large B-cell lymphoma (DLBCL). A number of novel immunotherapeutic strategies are under investigation to build upon current clinical benefit and offer further options to those patients who cannot tolerate conventional intensive therapies due to their age and/or state of health. Alongside immunotherapies that leverage the adaptive immune response, natural killer (NK) cell and myeloid cell-engaging therapies can utilize the innate immune system. Monoclonal antibodies engineered for greater recognition by the patient's immune system can enhance antitumor cytotoxic mechanisms mediated by NK cells and macrophages. In addition, CAR technology is extending into NK cells and macrophages and investigational immune checkpoint inhibitors targeting macrophage/myeloid cell checkpoints via the CD47/SIRPα axis are in development. Regimens that engage both innate and adaptive immune responses may help to overcome resistance to current immunotherapies. Furthermore, combinations of immunotherapy and oncogenic pathway inhibitors to reprogram the immunosuppressive tumor microenvironment of DLBCL may also potentiate antitumor responses. As immunotherapy treatment options continue to expand, both in the first-line setting and further lines of therapy, understanding how to harness these immunotherapies and the potential for combination approaches will be important for the development of future DLBCL treatment approaches.

Immunocytokines with target cell-restricted IL-15 activity for treatment of B cell malignancies

Despite the advances in cancer treatment achieved, for example, by the CD20 antibody rituximab, an urgent medical need remains to optimize the capacity of such antibodies to induce antibody-dependent cellular cytotoxicity (ADCC) that determines therapeutic efficacy. The cytokine IL-15 stimulates proliferation, activation, and cytolytic capacity of NK cells, but broad clinical use is prevented by short half-life, poor accumulation at the tumor site, and severe toxicity due to unspecific immune activation. We here report modified immunocytokines consisting of Fc-optimized CD19 and CD20 antibodies fused to an IL-15 moiety comprising an L45E-E46K double mutation (MIC+ format). The E46K mutation abrogated binding to IL-15Rα, thereby enabling substitution of physiological trans-presentation by target binding and thus conditional IL-15Rβγ stimulation, whereas the L45E mutation optimized IL-15Rβγ agonism and producibility. In vitro analysis of NK activation, anti-leukemia reactivity, and toxicity using autologous and allogeneic B cells confirmed target-dependent function of MIC+ constructs. Compared with Fc-optimized CD19 and CD20 antibodies, MIC+ constructs mediated superior target cell killing and NK cell proliferation. Mouse models using luciferase-expressing human NALM-6 lymphoma cells, patient acute lymphoblastic leukemia (ALL) cells, and murine EL-4 lymphoma cells transduced with human CD19/CD20 as targets and human and murine NK cells as effectors, respectively, confirmed superior and target-dependent anti-leukemic activity. In summary, MIC+ constructs combine the benefits of Fc-optimized antibodies and IL-15 cytokine activity and mediate superior NK cell immunity with potentially reduced side effects. They thus constitute a promising new immunotherapeutic approach shown here for B cell malignancies.

Tafasitamab for patients with relapsed or refractory diffuse large B-cell lymphoma: final 5-year efficacy and safety findings in the phase II L-MIND study

Tafasitamab, an anti-CD19 immunotherapy, is used with lenalidomide for patients with autologous stem cell transplant-ineligible relapsed/refractory diffuse large B-cell lymphoma based on the results of the phase II L-MIND study (NCT02399085). We report the final 5-year analysis of this study. Eighty patients ≥18 years who had received one to three prior systemic therapies, and had Eastern Cooperative Oncology Group performance status 0-2 received up to 12 cycles of co-administered tafasitamab and lenalidomide, followed by tafasitamab monotherapy until disease progression or unacceptable toxicity. The primary endpoint was the best objective response rate. Secondary endpoints included duration of response, progression-free survival, overall survival, and safety. Exploratory analyses evaluated efficacy endpoints by prior lines of therapy. At data cutoff on November 14, 2022, the objective response rate was 57.5%, with a complete response rate of 41.3% (n=33), which was consistent with prior analyses. With a median follow-up of 44.0 months, the median duration of response was not reached. The median progression-free survival was 11.6 months (95% confidence interval [95% CI]: 5.7-45.7) with a median follow-up of 45.6 months. The median overall survival was 33.5 months (95% CI: 18.3-not reached) with a median follow-up of 65.6 months. Patients who had received one prior line of therapy (n=40) showed a higher objective response rate (67.5%; 52.5% complete responses) compared to patients who had received two or more prior lines of therapy (n=40; 47.5%; 30% complete responses), but the median duration of response was not reached in either subgroup. Other exploratory analyses revealed consistent long-term efficacy results across subgroups. Adverse events were consistent with those described in previous reports, were manageable, and their frequency decreased during tafasitamab monotherapy, with no new safety concerns. This final 5-year analysis of L-MIND demonstrates that the immunotherapy combination of tafasitamab and lenalidomide is well tolerated and has long-term clinical benefit with durable responses.

CD19 occupancy with tafasitamab increases therapeutic index of CART19 cell therapy and diminishes severity of CRS

ABSTRACT

In the development of various strategies of anti-CD19 immunotherapy for the treatment of B-cell malignancies, it remains unclear whether CD19 monoclonal antibody therapy impairs subsequent CD19-targeted chimeric antigen receptor T-cell (CART19) therapy. We evaluated the potential interference between the CD19-targeting monoclonal antibody tafasitamab and CART19 treatment in preclinical models. Concomitant treatment with tafasitamab and CART19 showed major CD19 binding competition, which led to CART19 functional impairment. However, when CD19+ cell lines were pretreated with tafasitamab overnight and the unbound antibody was subsequently removed from the culture, CART19 function was not affected. In preclinical in vivo models, tafasitamab pretreatment demonstrated reduced incidence and severity of cytokine release syndrome and exhibited superior antitumor effects and overall survival compared with CART19 alone. This was associated with transient CD19 occupancy with tafasitamab, which in turn resulted in the inhibition of CART19 overactivation, leading to diminished CAR T apoptosis and pyroptosis of tumor cells.

Impact of structural modifications of IgG antibodies on effector functions

Immunoglobulin G (IgG) antibodies are a critical component of the adaptive immune system, binding to and neutralizing pathogens and other foreign substances. Recent advances in molecular antibody biology and structural protein engineering enabled the modification of IgG antibodies to enhance their therapeutic potential. This review summarizes recent progress in both natural and engineered structural modifications of IgG antibodies, including allotypic variation, glycosylation, Fc engineering, and Fc gamma receptor binding optimization. We discuss the functional consequences of these modifications to highlight their potential for therapeutical applications.

A paradox of choice: Sequencing therapy in relapsed/refractory diffuse large B-cell lymphoma

The available treatments for relapsed or refractory (R/R) diffuse large B-cell lymphoma (DLBCL) have experienced a dramatic change since 2017. Incremental advances in basic and translational science over several decades have led to innovations in immune-oncology. These innovations have culminated in eight separate approvals by the US Food and Drug Administration for the treatment of patients with R/R DLBCL over the last 10 years. High-dose therapy and autologous stem cell transplant (HDT-ASCT) remains the standard of care for transplant-eligible patients who relapse after an initial remission. For transplant-ineligible patients or for those who relapse following HDT-ASCT, multiple options exist. Monoclonal antibodies targeting CD19, antibody-drug conjugates, bispecific antibodies, immune effector cell products, and other agents with novel mechanisms of action are now available for patients with R/R DLBCL. There is increasing use of chimeric antigen receptor (CAR) T-cells as second-line therapy for patients with early relapse of DLBCL or those who are refractory to initial chemoimmunotherapy. The clinical benefits of these strategies vary and are influenced by patient and disease characteristics, as well as the type of prior therapy administered. Therefore, there are multiple clinical scenarios that clinicians might encounter when treating R/R DLBCL. An optimal sequence of drugs has not been established, and there is no evidence-based consensus on how to best order these agents. This abundance of choices introduces a paradox: proliferating treatment options are initially a boon to patients and providers, but as choices grow further they no longer liberate. Rather, more choices make the management of R/R DLBCL more challenging due to lack of direct comparisons among agents and a desire to maximize patient outcomes. Here, we provide a review of recently-approved second- and subsequent-line agents, summarize real-world data detailing the use of these medicines, and provide a framework for sequencing therapy in R/R DLBCL.

Treatment of Relapsed or Refractory Diffuse Large B-Cell Lymphoma: New Approved Options

Overall, around 40% of patients with diffuse large B-cell lymphoma (DLBCL) have refractory disease or relapse after the first line of treatment. Until relatively recently, the prognosis of patients with relapsed or refractory DLBCL was very poor and treatment options were very limited. In recent years, several novel therapies have been approved that provide more effective options than conventional chemotherapy and that have manageable toxicity profiles. CAR-T cell therapy has become the new standard treatment for patients with refractory or early relapsed DLBCL, based on the positive results of the phase 3 ZUMA-7 and TRANSFORM clinical trials. This review addresses the role of CAR-T therapy and autologous stem cell transplantation in the treatment of these patients and other approved options for patients who are not candidates for transplant, such as the combinations of polatuzumab vedotin with bendamustine and rituximab, and tafasitamab with lenalidomide.

Preclinical study of CD19 detection methods post tafasitamab treatment

Introduction

Several CD19 targeted antibody-based therapeutics are currently available for patients with diffuse large B-cell lymphoma (DLBCL), including the Fc-modified antibody immunotherapy tafasitamab. This therapeutic landscape warrants the evaluation of potential sequencing approaches. Prior to a subsequent CD19-targeted therapy, CD19 expression on tafasitamab-treated patient biopsy samples may be assessed. However, no standardized methods for its detection are currently available. In this context, selecting a tafasitamab-competing CD19 detection antibody for immunohistochemistry (IHC) or flow cytometry (FC) may lead to misinterpreting epitope masking by tafasitamab as antigen loss or downregulation.

Methods

We analyzed a comprehensive panel of commercially available CD19 detection antibody clones for IHC and FC using competition assays on tafasitamab pre-treated cell lines. To remove bound tafasitamab from the cell surface, an acidic dissociation protocol was used. Antibody affinities for CD19 were measured using Surface Plasmon Resonance (SPR) or Bio-Layer Interferometry (BLI).

Results

While CD19 was successfully detected on tafasitamab pre-treated samples using all 7 tested IHC antibody clones, all 8 tested FC antibody clones were confirmed to compete with tafasitamab. An acidic dissociation was demonstrated essential to circumvent CD19 masking by tafasitamab and avoid false negative FC results.

Discussion

The current study highlights the importance of selecting appropriate CD19 detection tools and techniques for correct interpretation of CD19 expression. The findings presented herein can serve as a guideline to investigators and may help navigate treatment strategies in the clinical setting.

Safety and efficacy of tafasitamab with or without lenalidomide added to first-line R-CHOP for DLBCL: the phase 1b First-MIND study

Anti-CD19 immunotherapy tafasitamab is used in combination with lenalidomide in patients with relapsed/refractory diffuse large B-cell lymphoma (DLBCL) who are ineligible for autologous stem cell transplant. Open-label, phase 1b, First-MIND study assessed safety and preliminary efficacy of tafasitamab + R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) ± lenalidomide as first-line therapy in patients with DLBCL. From December 2019 to August 2020, 83 adults with untreated DLBCL (International Prognostic Index 2-5) were screened and 66 were randomly assigned (33 per arm) to R-CHOP-tafasitamab (arm T) or R-CHOP-tafasitamab-lenalidomide (arm T/L) for 6 cycles. Primary end point was safety; secondary end points included end-of-treatment (EoT) overall response rate (ORR) and complete response (CR) rate. All patients had ≥1 treatment-emergent adverse event, mostly grade 1 or 2. Grade ≥3 neutropenia and thrombocytopenia occurred, respectively, in 57.6% and 12.1% (arm T) and 84.8% and 36.4% (arm T/L) of patients. Nonhematologic toxicities occurred at similar rates among arms. R-CHOP mean relative dose intensity was ≥89% in both arms. EoT ORR was 75.8% (CR 72.7%) in arm T and 81.8% (CR 66.7%) in arm T/L; best ORR across visits was 90.0% and 93.9%. Eighteen-month duration of response and of CR rates were 72.7% and 74.5% (arm T) and 78.7% and 86.5% (arm T/L); 24-month progression-free and overall survival rates were 72.7% and 90.3% (arm T) and 76.8% and 93.8% (arm T/L). Manageable safety and promising signals of efficacy were observed in both arms. Potential benefit of adding tafasitamab + lenalidomide to R-CHOP is being investigated in phase 3 frontMIND (NCT04824092). This study is registered at www.clinicaltrials.gov as #NCT04134936.

Patient-Specific Targeting of the T-Cell Receptor Variable Region as a Therapeutic Strategy in Clonal T-Cell Diseases

PURPOSE

Targeted therapeutics are a goal of medicine. Methods for targeting T-cell lymphoma lack specificity for the malignant cell, leading to elimination of healthy cells. The T-cell receptor (TCR) is designed for antigen recognition. T-cell malignancies expand from a single clone that expresses one of 48 TCR variable beta (Vβ) genes, providing a distinct therapeutic target. We hypothesized that a mAb that is exclusive to a specific Vβ would eliminate the malignant clone while having minimal effects on healthy T cells.

EXPERIMENTAL DESIGN

We identified a patient with large granular T-cell leukemia and sequenced his circulating T-cell population, 95% of which expressed Vβ13.3. We developed a panel of anti-Vβ13.3 antibodies to test for binding and elimination of the malignant T-cell clone.

RESULTS

Therapeutic antibody candidates bound the malignant clone with high affinity. Antibodies killed engineered cell lines expressing the patient TCR Vβ13.3 by antibody-dependent cellular cytotoxicity and TCR-mediated activation-induced cell death, and exhibited specific killing of patient malignant T cells in combination with exogenous natural killer cells. EL4 cells expressing the patient's TCR Vβ13.3 were also killed by antibody administration in an in vivo murine model.

CONCLUSIONS

This approach serves as an outline for development of therapeutics that can treat clonal T-cell-based malignancies and potentially other T-cell-mediated diseases. See related commentary by Varma and Diefenbach, p. 4024.

The progress of novel strategies on immune-based therapy in relapsed or refractory diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) can be cured with standard front-line immunochemotherapy, whereas nearly 30-40% of patients experience refractory or relapse. For several decades, the standard treatment strategy for fit relapsed/refractory (R/R) DLBCL patients has been high-dose chemotherapy followed by autologous hematopoietic stem cell transplant (auto-SCT). However, the patients who failed in salvage treatment or those ineligible for subsequent auto-SCT have dismal outcomes. Several immune-based therapies have been developed, including monoclonal antibodies, antibody-drug conjugates, bispecific T-cell engaging antibodies, chimeric antigen receptor T-cells, immune checkpoint inhibitors, and novel small molecules. Meanwhile, allogeneic SCT and radiotherapy are still necessary for disease control for fit patients with certain conditions. In this review, to expand clinical treatment options, we summarize the recent progress of immune-related therapies and prospect the future indirections in patients with R/R DLBCL.

Activity of tafasitamab in combination with rituximab in subtypes of aggressive lymphoma

Background

Despite recent advances in the treatment of aggressive lymphomas, a significant fraction of patients still succumbs to their disease. Thus, novel therapies are urgently needed. As the anti-CD20 antibody rituximab and the CD19-targeting antibody tafasitamab share distinct modes of actions, we investigated if dual-targeting of aggressive lymphoma B-cells by combining rituximab and tafasitamab might increase cytotoxic effects.

Methods

Antibody single and combination efficacy was determined investigating different modes of action including direct cytotoxicity, antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP) in in vitro and in vivo models of aggressive B-cell lymphoma comprising diffuse large B-cell lymphoma (DLBCL) and Burkitt lymphoma (BL).

Results

Three different sensitivity profiles to antibody monotherapy or combination treatment were observed in in vitro models: while 1/11 cell lines was primarily sensitive to tafasitamab and 2/11 to rituximab, the combination resulted in enhanced cell death in 8/11 cell lines in at least one mode of action. Treatment with either antibody or the combination resulted in decreased expression of the oncogenic transcription factor MYC and inhibition of AKT signaling, which mirrored the cell line-specific sensitivities to direct cytotoxicity. At last, the combination resulted in a synergistic survival benefit in a PBMC-humanized Ramos NOD/SCID mouse model.

Conclusion

This study demonstrates that the combination of tafasitamab and rituximab improves efficacy compared to single-agent treatments in models of aggressive B-cell lymphoma in vitro and in vivo.

Targeted Treatment of Adults with Relapsed or Refractory Diffuse Large B-Cell Lymphoma (DLBCL): Tafasitamab in Context

The outcomes of Relapsed/Refractory (R/R) Diffuse Large B-cell lymphoma have been historically poor. The recent development of several novel therapies including CD19 directed agents has improved the prognosis of this disease significantly. Chimeric antigen receptor (CAR) T-cell therapy has drastically changed the treatment of R/R DLBCL, but it is still associated with significant barriers and limited access. Tafasitamab (an anti-CD19 engineered monoclonal antibody), in addition to lenalidomide, has shown significant efficacy with exceptionally durable responses in patients with R/R DLBCL who are ineligible for autologous stem cell transplantation (ASCT). Tafasitamab-lenalidomide and certain other therapies (ie, antibody-drug conjugates and bispecific antibodies) are important treatment options for patients who are ineligible for CAR-T due to co-morbidities or lack of access, and patients with rapid progression of disease who are unable to wait for manufacturing of CAR-T. This review will thus discuss currently approved and recently studied targeted treatment options for patients with R/R DLBCL with an emphasis on CAR-T alternative options, particularly Tafasitamab-lenalidomide.

Combination of High-Resolution Structures for the B Cell Receptor and Co-Receptors Provides an Understanding of Their Interactions with Therapeutic Antibodies

B cells are central to the adaptive immune response, providing long lasting immunity after infection. B cell activation is mediated by a cell surface B cell receptor (BCR) following recognition of an antigen. BCR signaling is modulated by several co-receptors including CD22 and a complex that contains CD19 and CD81. Aberrant signaling through the BCR and co-receptors promotes the pathogenesis of several B cell malignancies and autoimmune diseases. Treatment of these diseases has been revolutionized by the development of monoclonal antibodies that bind to B cell surface antigens, including the BCR and its co-receptors. However, malignant B cells can escape targeting by several mechanisms and until recently, rational design of antibodies has been limited by the lack of high-resolution structures of the BCR and its co-receptors. Herein we review recently determined cryo-electron microscopy (cryo-EM) and crystal structures of the BCR, CD22, CD19 and CD81 molecules. These structures provide further understanding of the mechanisms of current antibody therapies and provide scaffolds for development of engineered antibodies for treatment of B cell malignancies and autoimmune diseases.

A Novel Fc-Engineered Anti-HER2 Bispecific Antibody With Enhanced Antitumor Activity

Human epidermal growth factor receptor 2 (HER2) overexpression has been demonstrated in a variety of cancers. Targeted therapy with anti-HER2 monoclonal antibodies (mAbs) has been approved as a therapeutic modality. Despite the efficacy of mAbs in tumor treatment, many patients do not benefit from this therapeutic platform. Fragment crystallizable (Fc) engineering is a common approach to improve the efficacy of therapeutic mAbs. Five Fc-engineered mAbs have so far been approved by FDA. We have recently developed an anti-HER2 bispecific mAb, BiHT, constructed from variable domains of trastuzumab, and our novel humanized anti-HER2 mAb, hersintuzumab. BiHT displayed promising antitumor activity as potently as the combination of the parental mAbs. Here, we aimed to modify the Fc of BiHT to improve its therapeutic efficacy. The Fc-engineered BiHT (MBiHT) bound to recombinant HER2 and its subdomains with an affinity similar to BiHT. It also recognized native HER2 on different cell lines, inhibited their proliferation, downregulated HER2 expression, and suppressed downstream signaling pathways similar to BiHT. Compared with BiHT, MBiHT displayed enhanced antibody-dependent cellular cytotoxicity activity against various tumor cell lines. It also inhibited the growth of ovarian xenograft tumors in nude mice more potently than BiHT. Our findings suggest that MBiHT could be a potent therapeutic candidate for the treatment of HER2-overexpressing cancer types.

Clinical Treatment Guidelines for Tafasitamab Plus Lenalidomide in Patients with Relapsed or Refractory Diffuse Large B-Cell Lymphoma

Diffuse large B-cell lymphoma (DLBCL) accounts for approximately 24% of new cases of B-cell non-Hodgkin lymphoma in the US each year. Up to 50% of patients relapse or are refractory (R/R) to the standard first-line treatment option, R-CHOP. The anti-CD19 monoclonal antibody tafasitamab, in combination with lenalidomide (LEN), is an NCCN preferred regimen for transplant-ineligible patients with R/R DLBCL and received accelerated approval in the US (July 2020) and conditional marketing authorization in Europe (August 2021) and other countries, based on data from the L-MIND study. The recommended dose of tafasitamab is 12 mg/kg by intravenous infusion, administered in combination with LEN 25 mg for 12 cycles, followed by tafasitamab monotherapy until disease progression or unacceptable toxicity. Tafasitamab + LEN is associated with durable responses in patients with R/R DLBCL. The majority of clinically significant treatment-associated adverse events are attributable to LEN and can be managed with dose modification and supportive therapy. We provide guidelines for the management of patients with R/R DLBCL treated with tafasitamab and LEN in routine clinical practice, including elderly patients and those with renal and hepatic impairment, and advice regarding patient education as part of a comprehensive patient engagement plan. Our recommendations include LEN administration at a reduced dose if required in patients unable to tolerate the recommended dose. No dose modification is required for tafasitamab in special patient populations.

The CD16 and CD32b Fc-gamma receptors regulate antibody-mediated responses in mouse natural killer cells

Natural killer (NK) cells are innate lymphocytes capable of mediating immune responses without prior sensitization. NK cells express Fc-gamma receptors (FcγRs) that engage the Fc region of IgG. Studies investigating the role of FcγRs on mouse NK cells have been limited due to lack specific reagents. In this study, we characterize the expression and biological consequences of activating mouse NK cells through their FcγRs. We demonstrate that most NK cells express the activating CD16 receptor, and a subset of NK cells also expresses the inhibitory CD32b receptor. Critically, these FcγRs are functional on mouse NK cells and can modulate antibody-mediated responses. We also characterized mice with conditional knockout alleles of Fcgr3 (CD16) or Fcgr2b (CD32b) in the NK and innate lymphoid cell (ILC) lineage. NK cells in these mice did not reveal any developmental defects and were responsive to cross-linking activating NK receptors, cytokine stimulation, and killing of YAC-1 targets. Importantly, CD16-deficient NK cells failed to induce antibody-directed cellular cytotoxicity of antibody-coated B-cell lymphomas in in vitro assays. In addition, we demonstrate the important role of CD16 on NK cells using an in vivo model of cancer immunotherapy using anti-CD20 antibody treatment of B-cell lymphomas.

Current state of NK cell-mediated immunotherapy in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) has become one of the most common hematological diseases in western countries, with an annual incidence of 42/100,000. Conventional chemotherapy and targeted therapeutic drugs showed limitations in prognosis or in efficiency in high-risk patients. Immunotherapy represented is one of the most effective therapeutic approaches with the potential of better effect and prognosis. Natural killer (NK) cells are good options for immunotherapy as they can effectively mediate anti-tumor activity of immune system by expressing activating and inhibiting receptors and recognizing specific ligands on various tumor cells. NK cells are critical in the immunotherapy of CLL by enhancing self-mediated antibody-dependent cytotoxicity (ADCC), allogeneic NK cell therapy and chimeric antigen receptor-natural killer (CAR-NK) cell therapy. In this article, we reviewed the features, working mechanisms, and receptors of NK cells, and the available evidence of the advantages and disadvantages of NK cell-based immunotherapies, and put forward future study directions in this field.

Immune-based therapies in diffuse large B-cell lymphoma

INTRODUCTION

Diffuse large B-cell lymphoma (DLBCL) is an aggressive and clinically heterogeneous malignancy originating from B-cells with up to 40% of patients experiencing primary refractory disease or relapse after first-line treatment. However, the past 5 years have seen a flurry of new drug approvals for DLBCL anchored upon new immune therapies, including chimeric antigen receptor (CAR) T-cells and antibody-based therapies.

AREAS COVERED

This article summarizes recent advances in the treatment of DLBCL, including in the first line and relapsed and refractory setting (second-line and beyond). A literature search was conducted for publications relevant to the immunotherapeutic approach to DLBCL from 2000 through March 2023 within PubMed and articles were reviewed. The search terms were immunotherapy, monoclonal antibodies, chimeric antigen receptor modified T-cell (CAR-T), and classification of DLBCL. Relevant clinical trials and pre-clinical studies exploring the strengths and weaknesses of current immune therapies against DLBCL were chosen. We additionally explored how intrinsic differences amongst DLBCL subtype biology and endogenous host immune recruitment contribute to variable therapeutic efficacy.

EXPERT OPINION

Future treatments will minimize chemotherapy exposure and be chosen by underlying tumor biology, paving the way for the promise of chemotherapeutic free regimens and improved outcomes for poor-risk subgroups.

Targeting CD19 for diffuse large B cell lymphoma in the era of CARs: Other modes of transportation

CD19 is nearly ubiquitously expressed on B-lymphocytes and in B-cell malignancies. Although CD19-directed CAR T cells have greatly improved outcomes in B-cell malignancies, there are significant limitations with this therapy. CD19 can also be effectively targeted by other drug classes, such as monoclonal antibodies, antibody-drug conjugates, and bispecific T cell engagers or antibodies. However, the optimal patient selection and sequencing of these novel therapies has not yet been established. In this review, we discuss the utilization of CD19 as a target for the treatment of DLBCL, focusing on tafasitamab, loncastuximab tesirine, and blinatumomab. We provide a comprehensive review of the pivotal clinical trials, discussing the strength and limitations of the data for each agent. We explore the emerging evidence that CD19 expression is retained following exposure to these agents and that patients can be successfully re-challenged with anti-CD19 therapies of a different drug class upon disease relapse post-CAR T cells. Finally, we discuss how these drugs potentially fit into the most current treatment paradigm for DLBCL.

Preclinical in vitro evaluation of immune suppression induced by GYM329, Fc-engineered sweeping antibody

Fc-engineering is commonly used to improve the therapeutic potency of antibody (Ab) treatments. Because FcγRIIb is the only inhibitory FcγR that contains an immunoreceptor tyrosine-based inhibition motif (ITIM), Fc-engineered Abs with enhanced binding affinity to FcγRIIb might provide immune suppression in clinical contexts. GYM329 is an anti-latent myostatin Fc-engineered Ab with increased affinity to FcγRIIb which is expected to improve muscle strength in patients with muscular disorders. Cross-linking of FcγRIIb by immune complex (IC) results in phosphorylation of ITIM to inhibit immune activation and apoptosis in B cells. We examined whether the IC of Fc-engineered Abs with enhanced binding affinity to FcγRIIb causes phosphorylation of ITIM or B cell apoptosis using GYM329 and its Fc variant Abs in human and cynomolgus-monkey (cyno) immune cells in vitro. IC of GYM329 with enhanced binding affinity to human FcγRIIb (×5) induced neither ITIM phosphorylation nor B cell apoptosis. As for GYM329, FcγRIIb should work as an endocytic receptor of small IC to sweep latent myostatin, so it is preferable that GYM329 induces neither ITIM phosphorylation nor B cell apoptosis to prevent immune suppression. In contrast, IC of myo-HuCy2b, the Ab with enhanced binding affinity to human FcγRIIb (×4), induced ITIM phosphorylation and B cell apoptosis. The result of the present study demonstrated that Fc-engineered Abs with similar binding affinity to FcγRIIb had different effects. Thus, it is important to also investigate FcγR-mediated immune functions other than binding to fully understand the biological effects of Fc-engineered Abs.

In Vitro Diffuse Large B-Cell Lymphoma Cell Line Models as Tools to Investigate Novel Immunotherapeutic Strategies

Despite the high incidence of diffuse large B-cell lymphoma (DLBCL), its management constitutes an ongoing challenge. The most common DLBCL variants include activated B-cell (ABC) and germinal center B-cell-like (GCB) subtypes including DLBCL with MYC and BCL2/BCL6 rearrangements which vary among each other with sensitivity to standard rituximab (RTX)-based chemoimmunotherapy regimens and lead to distinct clinical outcomes. However, as first line therapies lead to resistance/relapse (r/r) in about half of treated patients, there is an unmet clinical need to identify novel therapeutic strategies tailored for these patients. In particular, immunotherapy constitutes an attractive option largely explored in preclinical and clinical studies. Patient-derived cell lines that model primary tumor are indispensable tools that facilitate preclinical research. The current review provides an overview of available DLBCL cell line models and their utility in designing novel immunotherapeutic strategies.

Current Status of Novel Agents for the Treatment of B Cell Malignancies: What's Coming Next?

Resistance to death is one of the hallmarks of human B cell malignancies and often contributes to the lack of a lasting response to today's commonly used treatments. Drug discovery approaches designed to activate the death machinery have generated a large number of inhibitors of anti-apoptotic proteins from the B-cell lymphoma/leukemia 2 family and the B-cell receptor (BCR) signaling pathway. Orally administered small-molecule inhibitors of Bcl-2 protein and BCR partners (e.g., Bruton's tyrosine kinase and phosphatidylinositol-3 kinase) have already been included (as monotherapies or combination therapies) in the standard of care for selected B cell malignancies. Agonistic monoclonal antibodies and their derivatives (antibody-drug conjugates, antibody-radioisotope conjugates, bispecific T cell engagers, and chimeric antigen receptor-modified T cells) targeting tumor-associated antigens (TAAs, such as CD19, CD20, CD22, and CD38) are indicated for treatment (as monotherapies or combination therapies) of patients with B cell tumors. However, given that some patients are either refractory to current therapies or relapse after treatment, novel therapeutic strategies are needed. Here, we review current strategies for managing B cell malignancies, with a focus on the ongoing clinical development of more effective, selective drugs targeting these molecules, as well as other TAAs and signaling proteins. The observed impact of metabolic reprogramming on B cell pathophysiology highlights the promise of targeting metabolic checkpoints in the treatment of these disorders.

Triggering of the immune response to MCF7 cell line using conjugated antibody with bacterial antigens: In-vitro and in-vivo study

The current study intended to trigger the immune response to cancer cells by using antibodies conjugated with bacterial antigens. The protein membrane of the MCF7 cell line was extracted and specific antibodies against cell membrane antigens was produced in rabbits. The specific antibodies were purified using chromatography methods and linked to E. coli antigens or doxorubicin using Diethylenetriamine pentaacetate (DTPA) linker. After confirmation of the conjugation process using SDS-PAGE and ATR-FTIR methods, the MCF7 and HUVEC cells were treated with various concentrations of the prepared conjugated antibodies along with human serum. The toxicity of each treatment against MCF7 and HUVEC cells was evaluated using the MTT assay. Also, polylactic acid scaffolds that contain 10×10⁴ MCF7 cells were surgically placed in the peritoneal cavity of the rats. After treatment of each group, induction of the inflammatory responses was evaluated on stained histological sections of the scaffolds. The lowest cytotoxic doses of the antigen conjugated-antibody, doxorubicin-conjugated-antibody was 4 and 1 μg/mL, respectively. Doxorubicin conjugated antibodies displayed greater toxicity on both MCF7 and HUVEC cells. The in vivo finding revealed that the inflammatory cells were significantly higher in treating animals with antigen conjugated-antibody. The current synthetic agent stimulated the serum toxicity and induced an inflammatory response to MCF7 cell lines. Targeting of the bacterial antigens on tumor sites by immune system elements, could limit the growth of the tumor cells.

Dual Fc optimization to increase the cytotoxic activity of a CD19-targeting antibody

Targeting CD19 represents a promising strategy for the therapy of B-cell malignancies. Although non-engineered CD19 antibodies are poorly effective in mediating complement-dependent cytotoxicity (CDC), antibody-dependent cell-mediated cytotoxicity (ADCC) or antibody-dependent cellular phagocytosis (ADCP), these effector functions can be enhanced by Fc-engineering. Here, we engineered a CD19 antibody with the aim to improve effector cell-mediated killing and CDC activity by exchanging selected amino acid residues in the Fc domain. Based on the clinically approved Fc-optimized antibody tafasitamab, which triggers enhanced ADCC and ADCP due to two amino acid exchanges in the Fc domain (S239D/I332E), we additionally added the E345K amino acid exchange to favor antibody hexamerization on the target cell surface resulting in improved CDC. The dual engineered CD19-DEK antibody bound CD19 and Fcγ receptors with similar characteristics as the parental CD19-DE antibody. Both antibodies were similarly efficient in mediating ADCC and ADCP but only the dual optimized antibody was able to trigger complement deposition on target cells and effective CDC. Our data provide evidence that from a technical perspective selected Fc-enhancing mutations can be combined (S239D/I332E and E345K) allowing the enhancement of ADCC, ADCP and CDC with isolated effector populations. Interestingly, under more physiological conditions when the complement system and FcR-positive effector cells are available as effector source, strong complement deposition negatively impacts FcR engagement. Both effector functions were simultaneously active only at selected antibody concentrations. Dual Fc-optimized antibodies may represent a strategy to further improve CD19-directed cancer immunotherapy. In general, our results can help in guiding optimal antibody engineering strategies to optimize antibodies’ effector functions.

Harnessing natural killer cells for cancer immunotherapy: dispatching the first responders

Natural killer (NK) cells have crucial roles in the innate immunosurveillance of cancer and viral infections. They are 'first responders' that can spontaneously recognize abnormal cells in the body, rapidly eliminate them through focused cytotoxicity mechanisms and potently produce pro-inflammatory cytokines and chemokines that recruit and activate other immune cells to initiate an adaptive response. From the initial discovery of the diverse cell surface receptors on NK cells to the characterization of regulatory events that control their function, our understanding of the basic biology of NK cells has improved dramatically in the past three decades. This advanced knowledge has revealed increased mechanistic complexity, which has opened the doors to the development of a plethora of exciting new therapeutics that can effectively manipulate and target NK cell functional responses, particularly in cancer patients. Here, we summarize the basic mechanisms that regulate NK cell biology, review a wide variety of drugs, cytokines and antibodies currently being developed and used to stimulate NK cell responses, and outline evolving NK cell adoptive transfer approaches to treat cancer.

The Novel Therapeutic Landscape for Relapsed/Refractory Diffuse Large B Cell Lymphoma

Diffuse large B cell lymphoma (DLBCL) is an aggressive malignancy that has been traditionally treated with anthracycline-based chemotherapy, but approximately one-third of patients relapse after first-line therapy or have primary refractoriness. In this focused review, we discuss the 7 novel Food & Drug Administration (FDA)-approved medications for relapsed/refractory (R/R) DLBCL. We describe 5 CD19-targeted therapies, 3 of which are chimeric antigen receptor (CAR)-T cell therapies. We also highlight novel non-cell-based targeted therapies and discuss optimal sequencing considerations based on the goal of treatment, with an emphasis on CAR-T cell therapy as curative intent. We consider the limited tolerability of certain novel agents, prospects for elderly patients, and financial aspects of these approaches. We discuss advantages and limitations of these targeted therapies based on seminal clinical trials. Finally, we summarize ongoing trials involving promising agents making their way into the pharmacologic pipeline. These therapies include allogeneic CAR-T treatments and multi-antigen targeting therapies such as the CD19/CD22 CAR-T and the CD3/CD20 bispecific antibodies mosunetuzumab and odronextamab. We summarize our approach based on the best available evidence as we enter 2022.

Novel treatments in B cell non-Hodgkin's lymphomas

The improved understanding of lymphoma biology and recent advances in the field of cancer immunology have paved the way for the development of many effective small molecule inhibitors and immunotherapies in B cell non-Hodgkin's lymphomas. This article reviews novel treatments that have been approved recently by the US Food and Drug Administration and are now routinely used in clinical practice. It discusses their mechanisms of action, efficacy and safety, current therapeutic roles, and future directions in the treatment paradigm of different types of B cell non-Hodgkin's lymphoma. It also reviews other exciting novel treatments that are not yet approved but have unique mechanisms of action and have shown encouraging early results.

Overcoming CAR-Mediated CD19 Downmodulation and Leukemia Relapse with T Lymphocytes Secreting Anti-CD19 T-cell Engagers

Chimeric antigen receptor (CAR)-modified T cells have revolutionized the treatment of CD19-positive hematologic malignancies. Although anti-CD19 CAR-engineered autologous T cells can induce remission in patients with B-cell acute lymphoblastic leukemia, a large subset relapse, most of them with CD19-positive disease. Therefore, new therapeutic strategies are clearly needed. Here, we report a comprehensive study comparing engineered T cells either expressing a second-generation anti-CD19 CAR (CAR-T19) or secreting a CD19/CD3-targeting bispecific T-cell engager antibody (STAb-T19). We found that STAb-T19 cells are more effective than CAR-T19 cells at inducing cytotoxicity, avoiding leukemia escape in vitro, and preventing relapse in vivo. We observed that leukemia escape in vitro is associated with rapid and drastic CAR-induced internalization of CD19 that is coupled with lysosome-mediated degradation, leading to the emergence of transiently CD19-negative leukemic cells that evade the immune response of engineered CAR-T19 cells. In contrast, engineered STAb-T19 cells induce the formation of canonical immunologic synapses and prevent the CD19 downmodulation observed in anti-CD19 CAR-mediated interactions. Although both strategies show similar efficacy in short-term mouse models, there is a significant difference in a long-term patient-derived xenograft mouse model, where STAb-T19 cells efficiently eradicated leukemia cells, but leukemia relapsed after CAR-T19 therapy. Our findings suggest that the absence of CD19 downmodulation in the STAb-T19 strategy, coupled with the continued antibody secretion, allows an efficient recruitment of the endogenous T-cell pool, resulting in fast and effective elimination of cancer cells that may prevent CD19-positive relapses frequently associated with CAR-T19 therapies.

Tafasitamab mediates killing of B-cell non-Hodgkin's lymphoma in combination with γδ T cell or allogeneic NK cell therapy

Tafasitamab is an Fc-modified monoclonal antibody that binds to CD19, a cell-surface antigen that is broadly expressed on various types of B-cell non-Hodgkin’s lymphoma (NHL). Antibody-dependent cellular cytotoxicity (ADCC), a key mode of action of tafasitamab, is mediated through the binding of tafasitamab’s Fc region to FcγRIIIa receptors on immune effector cells and results in antitumor activity. Despite the proven clinical activity of tafasitamab in combination with lenalidomide in the treatment of diffuse large B-cell lymphoma (DLBCL), a higher number of immune cells in cancer patients may improve the activity of tafasitamab. Here, we characterized two ex vivo-expanded FcγRIIIa receptor—expressing cell types—γδ T and MG4101 natural killer (NK) cells—as effector cells for tafasitamab in vitro, and found that in the presence of these cells tafasitamab was able to induce ADCC against a range of NHL cell lines and patient-derived cells. We also explored the concept of effector cell supplementation during tafasitamab treatment in vivo by coadministering MG4101 NK cells in Raji and Ramos xenograft models of NHL. Combination treatment of tafasitamab and allogeneic MG4101 NK cells in these models demonstrated a survival benefit compared with tafasitamab or MG4101 monotherapy (Raji: 1.7- to 1.9-fold increase in lifespan; Ramos: 2.0- to 4.1-fold increase in lifespan). In conclusion, adoptive cell transfer of ex vivo-expanded allogeneic NK or autologous γδ T cells in combination with tafasitamab treatment may potentially be a promising novel approach to increase the number of immune effector cells and enhance the antitumor effect of tafasitamab.

Targeted Agents in the Treatment of Indolent B-Cell Non-Hodgkin Lymphomas

Targeted therapies continue to change the landscape of lymphoma treatment, resulting in improved therapy options and patient outcomes. Numerous agents are now approved for use in the indolent lymphomas and many others under development demonstrate significant promise. In this article, we review the landscape of targeted agents that apply to the indolent lymphomas, predominantly follicular lymphoma, lymphoplasmacytic lymphoma/Waldenstrom macroglobulinaemia and marginal zone lymphoma. The review covers small molecule inhibitors, immunomodulators and targeted immunotherapies, as well as presenting emerging and promising combination therapies.

SAR442085, a novel anti-CD38 antibody with enhanced antitumor activity against multiple myeloma

Anti-CD38 monoclonal antibodies (mAbs) represent a breakthrough in the treatment of multiple myeloma (MM), yet some patients fail to respond or progress quickly with this therapy, highlighting the need for novel approaches. In this study we compared the preclinical efficacy of SAR442085, a next-generation anti-CD38 mAb with enhanced affinity for activating Fcγ receptors (FcγR), with first-generation anti-CD38 mAb daratumumab and isatuximab. In surface plasmon resonance and cellular binding assays, we found that SAR442085 had higher binding affinity than daratumumab and isatuximab for FcγRIIa (CD32a) and FcγRIIIa (CD16a). SAR442085 also exhibited better in vitro antibody-dependent cellular cytotoxicity (ADCC) against a panel of MM cells expressing variable CD38 receptor densities including MM patients' primary plasma cells. The enhanced ADCC of SAR442085 was confirmed using NK-92 cells bearing low and high affinity FcγRIIIa (CD16a)-158F/V variants. Using MM patients' primary bone marrow cells, we confirmed that SAR442085 had an increased ability to engage FcγRIIIa, resulting in higher natural killer (NK) cell activation and degranulation against primary plasma cells than preexisting Fc wild-type anti-CD38 mAbs. Finally, using huFcgR transgenic mice that express human Fcγ receptors under the control of their human regulatory elements, we demonstrated that SAR442085 had higher NK cell-dependent in vivo antitumor efficacy and better survival than daratumumab and isatuximab against EL4 thymoma or VK*MYC myeloma cells overexpressing human CD38. These results highlight the preclinical efficacy of SAR442085 and support the current evaluation of this next-generation anti-CD38 antibody in phase I clinical development in patients with relapsed/refractory MM.

CD19-Targeted Immunotherapies for Diffuse Large B-Cell Lymphoma

Surgical resection, chemotherapy and radiotherapy were, for many years, the only available cancer treatments. Recently, the use of immune checkpoint inhibitors and adoptive cell therapies has emerged as promising alternative. These cancer immunotherapies are aimed to support or harness the patient's immune system to recognize and destroy cancer cells. Preclinical and clinical studies, based on the use of T cells and more recently NK cells genetically modified with chimeric antigen receptors retargeting the adoptive cell therapy towards tumor cells, have already shown remarkable results. In this review, we outline the latest highlights and progress in immunotherapies for the treatment of Diffuse Large B-cell Lymphoma (DLBCL) patients, focusing on CD19-targeted immunotherapies. We also discuss current clinical trials and opportunities of using immunotherapies to treat DLBCL patients.

Real-world data in drug development strategies for orphan drugs: tafasitamab in B cell lymphoma, a case study for approval based on a single-arm combination trial

Tafasitamab (TAF) plus lenalidomide (LEN) is a novel treatment option for patients with relapsed/refractory diffuse large B cell lymphoma (rrDLBCL) who are not eligible for autologous stem cell transplantation. The initial US/EU approvals for TAF represent precedents because this is the first time that approval of a novel combination therapy was granted based on a pivotal single-arm trial (SAT). Matching real world-data (RWD) helped to disentangle the contribution of individual agents. In this review, we present the TAF development strategy, the prospective incorporation of RWD within the clinical development plan, the corresponding regulatory hurdles of this strategy, and the prior regulatory actions for other cancer drugs that previously incorporated RWD and propensity score matching in EU and US regulatory submissions. We also outline how RWD could further advance and impact orphan drug development.

Molecular Aspects of Resistance to Immunotherapies-Advances in Understanding and Management of Diffuse Large B-Cell Lymphoma

Despite the unquestionable success achieved by rituximab-based regimens in the management of diffuse large B-cell lymphoma (DLBCL), the high incidence of relapsed/refractory disease still remains a challenge. The widespread clinical use of chemo-immunotherapy demonstrated that it invariably leads to the induction of resistance; however, the molecular mechanisms underlying this phenomenon remain unclear. Rituximab-mediated therapeutic effect primarily relies on complement-dependent cytotoxicity and antibody-dependent cell cytotoxicity, and their outcome is often compromised following the development of resistance. Factors involved include inherent genetic characteristics and rituximab-induced changes in effectors cells, the role of ligand/receptor interactions between target and effector cells, and the tumor microenvironment. This review focuses on summarizing the emerging advances in the understanding of the molecular basis responsible for the resistance induced by various forms of immunotherapy used in DLBCL. We outline available models of resistance and delineate solutions that may improve the efficacy of standard therapeutic protocols, which might be essential for the rational design of novel therapeutic regimens.

Fc-engineered antibodies with immune effector functions completely abolished

Elimination of the binding of immunoglobulin Fc to Fc gamma receptors (FcγR) is highly desirable for the avoidance of unwanted inflammatory responses to therapeutic antibodies and fusion proteins. Many different approaches have been described in the literature but none of them completely eliminates binding to all of the Fcγ receptors. Here we describe a set of novel variants having specific amino acid substitutions in the Fc region at L234 and L235 combined with the substitution G236R. They show no detectable binding to Fcγ receptors or to C1q, are inactive in functional cell-based assays and do not elicit inflammatory cytokine responses. Meanwhile, binding to FcRn, manufacturability, stability and potential for immunogenicity are unaffected. These variants have the potential to improve the safety and efficacy of therapeutic antibodies and Fc fusion proteins.

Relapsed/Refractory Diffuse Large B-Cell Lymphoma: A Look at the Approved and Emerging Therapies

Approximately 40% of patients with diffuse large B cell lymphoma (DLBCL) do not respond or develop relapsed disease after first-line chemoimmunotherapy. A minority of these patients can be cured with autologous hematopoietic stem cell transplantation (AHCT). Although chimeric antigen receptor (CAR) T cells have transformed the treatment paradigm of relapsed/refractory DLBCL, only 30-40% of patients achieve durable remissions. In addition, many patients with relapsed/refractory DLBCL are ineligible to receive treatment with CAR T cells due to comorbidities or logistical limitations. Since 2019, the following four non-CAR T-cell treatments have been approved in relapsed/refractory DLBCL: polatuzumab in combination with bendamustine and rituximab, selinexor, tafasitamab plus lenalidomide, and loncastuximab. In this article, I review the data behind these four approvals and discuss important considerations on their use in clinical practice. I also review emerging therapies that have shown promising early results in relapsed/refractory DLBCL including the bispecific antibodies, antibody-drug conjugates, Bruton tyrosine kinase inhibitors, BCL2 inhibitors, immune checkpoint inhibitors, and epigenetic modifiers.

The European Medicines Agency Review of Tafasitamab in Combination With Lenalidomide for the Treatment of Adult Patients With Relapsed/Refractory Diffuse Large B-cell Lymphoma

Tafasitamab is a humanized monoclonal antibody that binds to the CD19 antigen, which is expressed in tumor cells from patients with diffuse large B-cell lymphoma (DLBCL). On June 24, 2021, a positive opinion for a conditional marketing authorization was issued by the European Medicines Agency (EMA)’s Committee for Medicinal Products for Human Use (CHMP) for tafasitamab, in combination with lenalidomide, for the treatment of adult patients with relapsed or refractory DLBCL who are ineligible for autologous stem cell transplantation. Tafasitamab was evaluated in the phase 2 single-arm, multicenter, open-label L-MIND clinical trial. The primary endpoint of this trial was objective response rate (ORR). The best ORR, achieved at any time during the study, was 56.8% (95% confidence interval: 45.3%–67.8%), and the median duration of response was 34.6 months (95% confidence interval: 26.1–not reached). The most frequently reported adverse events by system organ class were infections and infestations (72.8%; grade ≥3: 29.6%), blood and lymphatic system disorders (65.4%; grade ≥3: 56.8%), gastrointestinal disorders (64.2%; grade ≥3: 2.5%), and general disorders and administration site conditions (58.0%; grade ≥3: 8.6%). The aim of this article is to summarize the scientific review of the application which led to the positive opinion by the CHMP.

A phase 2a, single-arm, open-label study of tafasitamab, a humanized, Fc-modified, anti-CD19 antibody, in patients with relapsed/refractory B-precursor cell acute lymphoblastic leukemia

BACKGROUND

B-precursor cell acute lymphoblastic leukemia (B-ALL) in adults is an aggressive and challenging condition, and patients with relapsed/refractory (R/R) disease after allogeneic stem cell transplantation (SCT), or noncandidates for SCT, have a particularly poor prognosis. The authors investigated the activity of the Fc-modified anti-CD19 antibody tafasitamab in adults with R/R B-ALL (NCT01685021).

METHODS

Adults with R/R B-ALL received single-agent tafasitamab 12 mg/kg weekly for up to four 28-day cycles. Patients with complete remission (with or without neutrophil/platelet recovery; complete remission [CR] or complete remission with incomplete count recovery [CRi]) after cycles 2, 3, or 4 could continue tafasitamab every 2 weeks for up to 3 further months. The primary end point was overall response rate (ORR).

RESULTS

Twenty-two patients were treated (median, 2 prior lines of therapy; range, 1-8). Six patients completed 2 cycles, and 2 of these patients responded for an ORR of 9%; 16 patients (73%) progressed before their first response assessment. Responses lasted 8 and 4 weeks in the 2 patients with CR and minimal residual disease (MRD)-negative CRi, respectively. Tafasitamab produced rapid B-cell/blast depletion in 21 of 22 patients within 1 to 2 weeks of first administration. Tafasitamab was well tolerated, with the most frequent adverse events being infusion-related reactions (59.1%) and fatigue (40.9%). Grade 3 to 4 febrile neutropenia (22.7%) was the most common hematologic adverse event.

CONCLUSIONS

Tafasitamab monotherapy was associated with clinical activity in a subset of patients with R/R B-ALL, including short-lasting CR and MRD-negative CRi. Given its favorable tolerability profile, further development of tafasitamab in chemoimmunotherapy combinations and MRD settings should be explored.

RE-MIND: Comparing Tafasitamab + Lenalidomide (L-MIND) with a Real-world Lenalidomide Monotherapy Cohort in Relapsed or Refractory Diffuse Large B-cell Lymphoma

PURPOSE

Tafasitamab, an Fc-modified, humanized, anti-CD19 monoclonal antibody, in combination with lenalidomide, demonstrated efficacy in transplant-ineligible patients with relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL), in the single-arm, phase II L-MIND study (NCT02399085). RE-MIND, a retrospective observational study, generated a historic control for L-MIND to delineate the contribution of tafasitamab to the efficacy of the combination.

PATIENTS AND METHODS

Data were retrospectively collected from patients with R/R DLBCL treated with lenalidomide monotherapy for comparison with tafasitamab + lenalidomide-treated patients (L-MIND). Key eligibility criteria were aligned with L-MIND. Estimated propensity score-based Nearest Neighbor 1:1 Matching methodology balanced the cohorts for nine prespecified prognostic baseline covariates. The primary endpoint was investigator-assessed best overall response rate (ORR). Secondary endpoints included complete response (CR) rate, progression-free survival (PFS), and overall survival (OS).

RESULTS

Data from 490 patients going through lenalidomide monotherapy were collected; 140 qualified for matching with the L-MIND cohort. The primary analysis included 76 patients from each cohort who received a lenalidomide starting dose of 25 mg/day. Cohort baseline covariates were comparable. A significantly better ORR of 67.1% (95% confidence interval, 55.4-77.5) was observed for the combination therapy versus 34.2% (23.7-46.0) for lenalidomide monotherapy [odds ratio, 3.89 (1.90-8.14); P < 0.0001]. Higher CR rates were achieved with combination therapy compared with lenalidomide monotherapy [39.5% (28.4-51.4) vs. 13.2% (6.5-22.9)]. Survival endpoints favored combination therapy. Lenalidomide monotherapy outcomes were similar to previously published data.

CONCLUSIONS

RE-MIND enabled the estimation of the additional treatment effect achieved by combining tafasitamab with lenalidomide in patients with R/R DLBCL.

Anti-CD19 monoclonal antibodies for the treatment of relapsed or refractory B-cell malignancies: a narrative review with focus on diffuse large B-cell lymphoma

PURPOSE

CD19 is a cell surface protein that is found on both healthy and malignant B cells. Accordingly, it has become an important target for novel treatments for non-Hodgkin lymphomas and B-cell leukaemia. Three anti-CD19 monoclonal antibodies with distinct mechanisms of action have been developed for the treatment of B-cell malignancies.

METHODS

We reviewed the preclinical and clinical data on the development of the newly approved anti-CD19 monoclonal antibodies blinatumomab, tafasitamab and loncastuximab tesirine, and consider their place in the treatment of relapsed or refractory B-cell malignancies.

RESULTS

Blinatumomab is a bispecific T-cell engager that binds to both CD19 on B cells and CD3 on T cells, facilitating antibody-dependent cytotoxicity. Blinatumomab significantly prolongs overall survival in patients with relapsed or refractory B-cell acute lymphoblastic leukaemia, although cytokine release syndrome and severe neurotoxicity may necessitate discontinuation. Tafasitamab, which has modified anti-CD19 Fab and Fc regions, has significantly enhanced affinity for both CD19 and effector cell receptors compared with unmodified anti-CD19. In L-MIND, tafasitamab plus lenalidomide provided an overall response rate (ORR) of 57.5% in patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL) in patients non-transplant eligible. Loncastuximab tesirine is an antibody-drug conjugate that has been studied as monotherapy and in combination with ibrutinib in 3L + relapsed or refractory DLBCL. The ORR was 48.3% in a phase II trial of loncastuximab tesirine. The optimal place of anti-CD19 monoclonal antibodies in therapy has yet to be determined, but the prospect of improved outcomes for at least some patients with treatment-resistant B-cell malignancies appears likely, particularly in those with limited therapeutic options and poor prognosis.

Safety of the Anti-CD19 antibody Tafasitamab in Long Term Responders from A Phase II Trial for Relapsed Lymphoma

BACKGROUND

Information about the long-term tolerability of tafasitamab is still limited.

METHODS

5 of 92 patients treated within a phase IIa study of single-agent tafasitamab in relapsed or refractory B NHL were followed for up to five years or longer for long-term tolerability.

RESULTS

Treatment was very well tolerated in an outpatient setting with no hospitalizations needed and mild and tolerable adverse events that occurred mostly within the first two years of treatment.

CONCLUSIONS

Given the excellent tolerability and efficacy of tafasitamab this agent can be used to induce remission in relapsed or refractory lymphoma either alone or in combination with chemotherapy.

An ultrapotent pan-β-coronavirus lineage B (β-CoV-B) neutralizing antibody locks the receptor-binding domain in closed conformation by targeting its conserved epitope

New threats posed by the emerging circulating variants of SARS-CoV-2 highlight the need to find conserved neutralizing epitopes for therapeutic antibodies and efficient vaccine design. Here, we identified a receptor-binding domain (RBD)-binding antibody, XG014, which potently neutralizes β-coronavirus lineage B (β-CoV-B), including SARS-CoV-2, its circulating variants, SARS-CoV and bat SARSr-CoV WIV1. Interestingly, antibody family members competing with XG014 binding show reduced levels of cross-reactivity and induce antibody-dependent SARS-CoV-2 spike (S) protein-mediated cell-cell fusion, suggesting a unique mode of recognition by XG014. Structural analyses reveal that XG014 recognizes a conserved epitope outside the ACE2 binding site and completely locks RBD in the non-functional "down" conformation, while its family member XG005 directly competes with ACE2 binding and position the RBD "up". Single administration of XG014 is effective in protection against and therapy of SARS-CoV-2 infection in vivo. Our findings suggest the potential to develop XG014 as pan-β-CoV-B therapeutics and the importance of the XG014 conserved antigenic epitope for designing broadly protective vaccines against β-CoV-B and newly emerging SARS-CoV-2 variants of concern.

Tafasitamab combined with idelalisib or venetoclax in patients with CLL previously treated with a BTK inhibitor

Patients with relapsed/refractory chronic lymphocytic leukemia (R/R CLL) whose treatment failed with a Bruton's tyrosine kinase inhibitor have poor outcomes. We investigated tafasitamab plus idelalisib (cohort A) or venetoclax (cohort B) in this patient population in a phase II study (NCT02639910). In total, 24 patients were enrolled (cohort A: n = 11, median time on study, 7.4 months; cohort B: n = 13, median time on study, 15.6 months). The most common treatment-emergent adverse event (TEAE) in cohort A was anemia (63.6%) and in cohort B was infusion-related reaction (53.8%). The most common severe TEAE was neutropenia (cohort A: 45.5%; cohort B: 46.2%). The best overall response rate was 90.9% (cohort A) and 76.9% (cohort B). Undetectable minimal residual disease in peripheral blood was achieved in 2/8 patients (cohort A) and 6/7 patients (cohort B). Overall, these results suggest that anti-CD19 antibody-based combinations may be important in the treatment of patients with CLL.