Efficacy of checkpoint inhibition after CAR-T failure in aggressive B-cell lymphomas: outcomes from 15 US institutions

Overcoming the challenges of primary resistance and relapse after CAR-T cell therapy

INTRODUCTION

While CAR T-cell therapy has led to remarkable responses in relapsed B-cell hematologic malignancies, only 50% of patients ultimately have a complete, sustained response. Understanding the mechanisms of resistance and relapse after CAR T-cell therapy is crucial to future development and improving outcomes.

AREAS COVERED

We review reasons for both primary resistance and relapse after CAR T-cell therapies. Reasons for primary failure include CAR T-cell manufacturing problems, suboptimal fitness of autologous T-cells themselves, and intrinsic features of the underlying cancer and tumor microenvironment. Relapse after initial response to CAR T-cell therapy may be antigen-positive, due to CAR T-cell exhaustion or limited persistence, or antigen-negative, due to antigen-modulation on the target cells. Finally, we discuss ongoing efforts to overcome resistance to CAR T-cell therapy with enhanced CAR constructs, manufacturing methods, alternate cell types, combinatorial strategies, and optimization of both pre-infusion conditioning regimens and post-infusion consolidative strategies.

EXPERT OPINION

There is a continued need for novel approaches to CAR T-cell therapy for both hematologic and solid malignancies to obtain sustained remissions. Opportunities for improvement include development of new targets, optimally combining existing CAR T-cell therapies, and defining the role for adjunctive immune modulators and stem cell transplant in enhancing long-term survival.

Novel Targets and Advanced Therapies in Diffuse Large B Cell Lymphomas

Since the introduction of rituximab in the late 1990s, significant progress has been made in advancing targeted therapies for B cell lymphomas, improving patients' chance of being cured and clinicians' therapeutic armamentarium. A better understanding of disease biology and pathogenic pathways, coupled with refinements in immunophenotypic and molecular diagnostics, have been instrumental in these achievements. While traditional chemotherapy remains fundamental in most cases, concerns surrounding chemorefractoriness and cumulative toxicities, particularly the depletion of the hemopoietic reserve, underscore the imperative for personalized treatment approaches. Integrating targeted agents, notably monoclonal antibodies, alongside chemotherapy has yielded heightened response rates and prolonged survival. A notable paradigm shift is underway with innovative-targeted therapies replacing cytotoxic drugs, challenging conventional salvage strategies like stem cell transplantation. This review examines the landscape of emerging targets for lymphoma cells and explores innovative therapies for diffuse large B cell lymphoma (DLBCL). From Chimeric Antigen Receptor-T cells to more potent monoclonal antibodies, antibody-drug conjugates, bispecific antibodies, checkpoint inhibitors, and small molecules targeting intracellular pathways, each modality offers promising avenues for therapeutic advancement. This review aims to furnish insights into their potential implications for the future of DLBCL treatment strategies.

Treatment outcomes in patients with large B-cell lymphoma after progression to chimeric antigen receptor T-cell therapy

Over 60% of relapsed/refractory (R/R) large B-cell lymphoma (LBCL) patients who receive chimeric antigen receptor (CAR) T cells will experience disease progression. There is no standard next line of therapy and information in this setting is scarce and heterogeneous. We analyzed 387 R/R LBCL patients who progressed after CAR T cells from July 2018 until March 2022 in Spain and the United Kingdom. Median overall survival (OS) was 5.3 months, with significant differences according to the interval between infusion and progression (<2 months [1.9 months], 2-6 months [5.2 months], and >6 months [not reached]). After progression, 237 (61%) patients received treatment. Focusing on the first subsequent therapy, overall (complete) response rates were 67% (38%) for polatuzumab-bendamustine-rituximab (POLA), 51% (36%) for bispecific antibodies (BsAb), 45% (35%) for radiotherapy (RT), 33% (26%) for immune checkpoint inhibitors (ICIs), 25% (0%) for lenalidomide (LENA), and 25% (14%) for chemotherapy (CT). In terms of survival, 12-month progression-free survival and OS was 36.2% and 51.0% for POLA, 32.0% and 50.1% for BsAb, 30.8% and 37.5% for RT, 29.9% and 27.8% for ICI, 7.3% and 20.8% for LENA, and 6.1% and 18.3% for CT. Thirty-two (14%) patients received an allogeneic hematopoietic cell transplant with median OS not reached after a median follow-up of 15.1 months. In conclusion, patients with R/R LBCL who progress within the first 2 months after CAR T-cell therapy have dismal outcomes. Novel targeted agents, such as polatuzumab and BsAbs, can achieve prolonged survival after CAR T-cell therapy failure.

Meta-analysis of response rates to first-line salvage treatment after CAR-T therapy failure in large B-cell lymphoma patients

INTRODUCTION

The prognosis for large B-cell lymphoma (LBCL) patients who did not respond or relapsed after chimeric antigen receptor (CAR)-T therapy remains dismal, with no established consensus on the most effective salvage regimen.

METHODS

We conducted a random-effects meta-analysis of complete response (CR) and overall response rates (ORR) to first-line treatments for CAR-T-relapsed/refractory LBCL. We followed the predefined protocol available at PROSPERO (CRD42023473854).

RESULTS

We identified 41 studies evaluating the following interventions: non-CD19 CAR-T, CD19 CAR-T, bispecific antibodies (BiTEs), lenalidomide- and polatuzumab-based regimens, radiotherapy, immune checkpoint inhibitors (ICI), Bruton's Tyrosine Kinase inhibitors (BTKi). Non-CD19 CAR-T cells yielded the best CR (56%, CI: 40-71%), significantly higher than other interventions except CD19 CAR-T (CR = 30%, CI: 7-58%). BiTEs, radiotherapy, lenalidomide- and polatuzumab-based regimens (CR: 28%, 26%, 19%, 24% respectively) did not differ significantly from each other. ICI and BTKi showed the lowest CR rates (12%, CI: 5-20% and 8%, CI: 0-23%, respectively), and were also significantly inferior to BiTEs. ORR was the highest for non-CD19 CAR-T (ORR = 80%, CI: 66-92%), whereas all other regimens yielded values below 50%.

CONCLUSIONS

Non-CD19 CAR-T cells were associated with higher response rates and should be considered if patients are eligible. Given the heterogeneity of the estimates, the results should be interpreted cautiously.

REGISTRATION

PROSPERO CRD42023473854.

The role of immunotherapy sensitizers and novel immunotherapy modalities in the treatment of cancer

The importance of the immune system in the response against cancer has always been a subject of intense investigation. The advent of immune checkpoint inhibitors has transformed the landscape of oncologic treatments, while expanding the understanding of this disease's pathophysiology. Consequently, many therapies are being investigated, with interventions directed at different steps and pathways of the immune response. Relevantly, immunotherapy sensitizers have arisen as approaches focused on the synergistic effects of immunotherapy combination, or the combination of immunotherapy and other treatment modalities, such as chemotherapy or radiation therapy. Concomitantly, novel immunotherapy modalities are also in development. Approaches focusing from the tumor intrinsic pathways to the tumor microenvironment and ex-vivo interventions, such as CAR-T cell therapies and tumor-infiltrating lymphocytes are important examples. Although many of those interventions were initially envisioned as standalone options, their combination has demonstrated promising results in early-phase in vitro studies and clinical trials. The possibility of coupling different immunotherapy modalities, as well as with other techniques, further strengthen the concept of sensitizers, allowing for deeper and more robust responses in cancer treatment. This review aims to present an overview of the concepts of these sensitizing mechanisms that are the basis for the synergistic effects of immunotherapy combination, or the combination of immunotherapy and a multitude of therapeutic strategies. Novel immunotherapy modalities are also presented, focusing on the potential of combining them with sensitizer interventions. Understanding the complexity underlying these principles may be the key for future breakthroughs and improved patient outcomes.

Treatment strategies for relapse after CAR T-cell therapy in B cell lymphoma

Clinical trials of anti-CD19 chimeric antigen receptor T (CART19) cell therapy have shown high overall response rates in patients with relapsed/refractory B-cell malignancies. CART19 cell therapy has been approved by the US Food and Drug Administration for patients who relapsed less than 12 months after initial therapy or who are refractory to first-line therapy. However, durable remission of CART19 cell therapy is still lacking, and 30%-60% of patients will eventually relapse after CART19 infusion. In general, the prognosis of patients who relapse after CART19 cell therapy is poor, and various strategies to treat this patient population have been investigated extensively. CART19 failures can be broadly categorized by the emergence of either CD19-positive or CD19-negative lymphoma cells. If CD19 expression is preserved on the lymphoma cells, a second infusion of CART19 cells or reactivation of previously infused CART19 cells with immune checkpoint inhibitors can be considered. When patients develop CD19-negative relapse, targeting different antigens (e.g., CD20 or CD22) with CAR T cells, investigational chemotherapies, or hematopoietic stem cell transplantation are potential treatment options. However, salvage therapies for relapsed large B-cell lymphoma after CART19 cell therapy have not been fully explored and are conducted based on clinicians' case-by-case decisions. In this review, we will focus on salvage therapies reported to date and discuss the management of relapsed/refractory large B-cell lymphomas after CART19 cell therapy.

Chimeric Antigen Receptor T-cell Therapy for Chronic Lymphocytic Leukemia: What is the supporting evidence so far?

While acknowledging that newer therapies have improved survival rates in chronic lymphocytic leukemia (CLL), patients with high-risk disease features are at an increased risk of treatment failure. Allogeneic hematopoietic cell transplantation (allo-HCT) was traditionally offered as front-line consolidation in high-risk CLL; however, with the emergence of targeted therapies like Bruton tyrosine kinase (BTK) and B-cell lymphoma 2 (BCL-2) inhibitors, the role of allo-HCT has been relegated to later stages of the disease. Patients with relapsed/refractory (R/R) CLL who have failed both BTK and BCL-2 inhibitors represent a therapeutic challenge owing to a poor prognosis. Chimeric antigen receptor T-cell (CAR T) therapies targeting CD19 have improved response rates and overall survival in various types of R/R B-cell non-Hodgkin lymphomas. For CLL, no approved CAR T-cell therapies are yet available. Emerging data appear to show a therapeutic benefit of CAR T-cell therapy in patients with R/R CLL, even after failing an allo-HCT.

Synthetic manipulation of the cancer-immunity cycle: CAR-T cell therapy

Synthetic immunity to cancer has been pioneered by the application of chimeric antigen receptor (CAR) engineering into autologous T cells. CAR T cell therapy is highly amenable to molecular engineering to bypass barriers of the cancer immunity cycle, such as endogenous antigen presentation, immune priming, and natural checkpoints that constrain immune responses. Here, we review CAR T cell design and the mechanisms that drive sustained CAR T cell effector activity and anti-tumor function. We discuss engineering approaches aimed at improving anti-tumor function through a variety of mechanistic interventions for both hematologic and solid tumors. The ability to engineer T cells in such a variety of ways, including by modifying their trafficking, antigen recognition, costimulation, and addition of synthetic genes, circuits, knockouts and base edits to finely tune complex functions, is arguably the most powerful way to manipulate the cancer immunity cycle in patients.

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.

Failure of CAR-T cell therapy in relapsed and refractory large cell lymphoma and multiple myeloma: An urgent unmet need

Since its FDA approval, chimeric antigen receptor (CAR)-T cell therapy is changing the landscape of the treatment algorithm for relapsed and refractory large cell lymphoma and multiple myeloma. While initially hailed as a game changer and received widely with great enthusiasm, the reality of treatment failure soon became a major disappointment. This situation left patients and clinicians alike wondering about the next treatment options. CAR-T cell therapy failure for aggressive lymphoma or multiple myeloma creates a very poor prognosis and the treatment options are very limited. New emerging data, however, show promise for the use of approaches that include bispecific antibodies and other strategies to rescue affected patients. In this review, we summarize the current emerging data on the treatment options for patients whose disease has relapsed or remains refractory after CAR-T cell therapy failure, an area of great unmet need.