The Agony of Choice-Where to Place the Wave of BCMA-Targeted Therapies in the Multiple Myeloma Treatment Puzzle in 2022 and Beyond

The UK consensus supporting effective introduction of novel treatments for multiple myeloma in the National Health Service

Introduction

Multiple myeloma (MM) is a relapsing, debilitating blood cancer which remains incurable despite advances in treatments. Patients typically receive multiple lines of treatment, to which they become refractory, thereby limiting treatment options. B-cell maturation antigen (BCMA) bispecific antibodies (BsAbs) represent a novel modality of treatment that has significant efficacy for relapsed or refractory patients.The objective was to develop consensus statements for the effective implementation of BCMA BsAbs for relapsed or refractory MM patients within the National Health Service (NHS).

Methods

The process employed a modified Delphi methodology. In March 2023, a literature review on the topic of novel treatments for MM was performed using the PubMed database.The process employed a modified Delphi methodology. Following a literature review, a steering group of eight expert clinicians identified and agreed on five main topics of focus and 44 statements. These were then developed into an online survey which was distributed to healthcare professionals working in Levels 1, 2 and 3 haematology centres in the United Kingdom. Results were then shared with the expert panel to determine conclusions. The threshold for consensus agreement was set at 75%.

Results

A total of 60 responses were received from all three centre levels. There was representation from all targeted centres. Consensus was achieved in 42 statements (95%) across three broad areas: the patient profile, initiation and step-up dosing, monitoring and ongoing care, the role of multidisciplinary team and service designs for optimal management, consensus was not achieved for two statements. Given the level of agreement and that the stopping criteria were met, it was decided not to undertake further Delphi rounds.

Conclusion

This consensus provides a framework to support the effective introduction of novel treatments for MM in the NHS. The results were used to inform a checklist for use within haematology services when considering the provision of MM care specific to BCMA BsAbs.

Evaluation of Anti-CAR Linker mAbs for CAR T Monitoring after BiTEs/bsAbs and CAR T-Cell Pretreatment

For the monitoring of chimeric antigen receptor (CAR) T-cell therapies, antigen-based CAR detection methods are usually applied. However, for each target-antigen, a separate detection system is required. Furthermore, when monitored CAR T-cells in the blood of patients treated with bispecific antibodies or T-cell engagers (bsAbs/BiTEs) recognize the same antigen, these methods produce false-positive results in clinical diagnostics. Anti-CAR-linker monoclonal antibodies (mAbs) targeting the linker sequence between the variable domains of the antigen binding CAR fragment promise a universal and unbiased CAR detection. To test this, we analyzed clinical specimens of all BCMA- and CD19-targeting CAR T-cell products currently approved for clinical use. We found a highly specific and sensitive CAR detection using anti-CAR-linker mAb in blood cells from patients treated with Ide-cel, Tisa-cel, Axi-cel, Brexu-cel, and Liso-cel. For Ide-cel and Tisa-cel, the sensitivity was significantly lower compared to that for antigen-based CAR detection assays. Strikingly, the specificity of anti-CAR linker mAb was not affected by the simultaneous presence of bispecific blinatumomab or teclistamab for Axi-cel, Brexu-cel, Liso-cel, or Ide-cel, respectively. Cilta-cel (containing a monomeric G4S-CAR linker) could not be detected by anti-CAR linker mAb. In conclusion, anti-CAR-linker mAbs are highly specific and useful for CAR T-cell monitoring but are not universally applicable.

In Vitro Functionality and Endurance of GMP-Compliant Point-of-Care BCMA.CAR-T Cells at Different Timepoints of Cryopreservation

The search for target antigens for CAR-T cell therapy against multiple myeloma defined the B-cell maturation antigen (BCMA) as an interesting candidate. Several studies with BCMA-directed CAR-T cell therapy showed promising results. Second-generation point-of-care BCMA.CAR-T cells were manufactured to be of a GMP (good manufacturing practice) standard using the CliniMACS Prodigy® device. Cytokine release in BCMA.CAR-T cells after stimulation with BCMA positive versus negative myeloma cell lines, U266/HL60, was assessed via intracellular staining and flow cytometry. The short-term cytotoxic potency of CAR-T cells was evaluated by chromium-51 release, while the long-term potency used co-culture (3 days/round) at effector/target cell ratios of 1:1 and 1:4. To evaluate the activation and exhaustion of CAR-T cells, exhaustion markers were assessed via flow cytometry. Stability was tested through a comparison of these evaluations at different timepoints: d0 as well as d + 14, d + 90 and d + 365 of cryopreservation. As results, (1) Killing efficiency of U266 cells correlated with the dose of CAR-T cells in a classical 4 h chromium-release assay. There was no significant difference after cryopreservation on different timepoints. (2) In terms of endurance of BCMA.CAR-T cell function, BCMA.CAR-T cells kept their ability to kill all tumor cells over six rounds of co-culture. (3) BCMA.CAR-T cells released high amounts of cytokines upon stimulation with tumor cells. There was no significant difference in cytokine release after cryopreservation. According to the results, BCMA.CAR-T cells manufactured under GMP conditions exerted robust and specific killing of target tumor cells with a high release of cytokines. Even after 1 year of cryopreservation, cytotoxic functions were maintained at the same level. This gives clinicians sufficient time to adjust the timepoint of BCMA.CAR-T cell application to the patient's course of the underlying disease.

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.

Targeting the Microenvironment for Treating Multiple Myeloma

Multiple myeloma (MM) is a malignant, incurable disease characterized by the expansion of monoclonal terminally differentiated plasma cells in the bone marrow. MM is consistently preceded by an asymptomatic monoclonal gammopathy of undetermined significance, and in the absence of myeloma defining events followed by a stage termed smoldering multiple myeloma (SMM), which finally progresses to active myeloma if signs of organ damage are present. The reciprocal interaction between tumor cells and the tumor microenvironment plays a crucial role in the development of MM and the establishment of a tumor-promoting stroma facilitates tumor growth and myeloma progression. Since myeloma cells depend on signals from the bone marrow microenvironment (BMME) for their survival, therapeutic interventions targeting the BMME are a novel and successful strategy for myeloma care. Here, we describe the complex interplay between myeloma cells and the cellular components of the BMME that is essential for MM development and progression. Finally, we present BMME modifying treatment options such as anti-CD38 based therapies, immunomodulatory drugs (IMiDs), CAR T-cell therapies, bispecific antibodies, and antibody-drug conjugates which have significantly improved the long-term outcome of myeloma patients, and thus represent novel therapeutic standards.

BCMA-targeted therapies for multiple myeloma: strategies to maximise efficacy and minimize adverse events

INTRODUCTION

Immunotherapies targeting B cell maturation antigen (BCMA) in multiple myeloma are transitioning through trials and entering the clinic, and will likely become a core pillar in myeloma therapeutics. These agents demonstrate unprecedented activity in multiply relapsed patients, but - notwithstanding the short follow-up times - their survival curves do not appear to demonstrate a plateau, and the treatments inevitably bring with them a range of toxicities that might be associated with tolerability issues.

AREAS COVERED

We will briefly lay out the current therapeutic landscape in multiple myeloma, before introducing BCMA and explaining its significance. We will address in turn the three key classes of anti-BCMA immunotherapies: antibody-drug conjugates, bispecific antibodies and chimeric antigen receptor T cells. We describe the mechanisms of action of these classes and review the evidence supporting their efficacy and toxicities. We then bring all three therapies into one discussion that explores how to mitigate toxicities and overcome myeloma's ability to resist these potent treatments.

EXPERT OPINION

Finally, we take the discussion back to the clinic, and consider how we might deploy anti-BCMA therapies most effectively for our patients. We consider the sequencing of treatment, and what further evidence is needed to more fully inform our therapy decisions.

Targeting BCMA to Treat Multiple Myeloma: Updates From the 2021 ASH Annual Meeting

With the gradual improvement of treatment regimens, the survival time of multiple myeloma (MM) patients has been significantly prolonged. Even so, MM is still a nightmare with an inferior prognosis. B-cell maturation antigen (BCMA) is highly expressed on the surface of malignant myeloma cells. For the past few years, significant progress has been made in various BCMA-targeted immunotherapies for treating patients with RRMM, including anti-BCMA mAbs, antibody-drug conjugates, bispecific T-cell engagers, and BCMA-targeted adoptive cell therapy like chimeric antigen receptor (CAR)-T cell. The 63rd annual meeting of the American Society of Hematology updated some information about the application of BCMA in MM. This review summarizes part of the related points presented at this conference.