Beyond BCMA: the next wave of CAR T cell therapy in multiple myeloma

BCMA-targeted therapies in multiple myeloma: advances, challenges and future prospects

Multiple myeloma (MM) is hematological cancer characterized by the aberrant proliferation of plasma cells. The treatment of MM has historically presented challenges, with a limited number of patients achieving sustained remission. Recent advancements in the therapeutic landscape have been marked by the development of B-cell maturation antigen (BCMA)-targeted therapies. BCMA, a plasma cell surface protein, is instrumental in the proliferation and survival of myeloma cells. This review aims to critically assess recent developments in BCMA-targeted therapies. The focus is on evaluating their efficacy and accessibility, as well as discussing potential future directions in this field. Emphasis is placed on chimeric antigen receptor (CAR) T-cell therapy and bispecific antibodies as emerging therapeutic strategies. An extensive review of current clinical trials and studies was conducted, centering on BCMA-targeted therapies. This encompassed an analysis of CAR T-cell therapies, which involve the genetic modification of patient T-cells to target BCMA, and bispecific antibodies that bind to both BCMA on myeloma cells and CD3 on T-cells. Clinical trials have demonstrated the efficacy of BCMA-targeted therapies in MM, with some patients achieving complete remission. However, these therapies are associated with adverse effects such as cytokine release syndrome and neurotoxicity. Research efforts are ongoing to reduce these side effects and enhance overall therapeutic effectiveness. BCMA-targeted therapies signify a notable advancement in MM treatment, offering prospects for prolonged remission and potentially curative outcomes. Despite existing challenges, these therapies represent a significant shift in MM management. The review highlights the necessity of ongoing research to optimize these therapies, improve patient outcomes, and increase treatment accessibility.

Perspectives on Talquetamab and its Utility in the Treatment of Multiple Myeloma: Safety, Efficacy and Place in Therapy

Despite recent advancements, most patients with multiple myeloma eventually develop resistance to available treatments, highlighting the need for new therapeutic strategies. G protein-coupled receptor class C group 5 member D (GPRC5D) has emerged as a viable novel therapeutic target on myeloma cells, leading to the clinical development of talquetamab, the first GPRC5D-directed bispecific T-cell engager (TCE). Talquetamab was granted accelerated approval in August 2023 by the Food and Drug Administration. Besides expected short-term toxicities including cytokine release syndrome, neurotoxicity and cytopenias, talquetamab commonly causes adverse events involving the oral cavity, nails, and skin, which can negatively impact quality of life and in some cases lead to treatment discontinuation. Despite these pitfalls, talquetamab yields responses in most treated patients, which in a subset are durable. There are now several clinical trials investigating talquetamab in different clinical contexts in multiple myeloma, as well as in combination with other anti-myeloma agents. Beyond results from these prospective trials, better biologic understanding of resistance mechanisms to talquetamab and improved strategies to mitigate common toxicities are key questions as talquetamab finds its place in the treatment of multiple myeloma.

The Evolving Landscape in Multiple Myeloma: From Risk Stratification to T Cell-Directed Advanced Therapies

Multiple myeloma is biologically and clinically a complex and heterogeneous disease which develops late in life, with the median age at the time of initial diagnosis being 66 years. In 1975, Durie and Salmon developed the first broadly adopted staging system in multiple myeloma, and in the ensuing decades, the risk stratification tools have improved and now incorporate different parameters to better predict the prognosis and to guide the treatment decisions. The International Staging System (ISS) was initially developed in 2005, revised in 2015 (R-ISS), and again in 2022 (R2-ISS). Tremendous progress has been achieved in multiple myeloma therapy over the past 25 years with the approval of immunomodulatory drugs, proteasome inhibitors, and anti-CD38 monoclonal antibodies, resulting in a major paradigm shift. The dysfunction of the innate and adaptive immune system, especially in the T cell repertoire, represents a hallmark of multiple myeloma evolution over time, supporting the need for additional therapeutic approaches to activate the host's immune system and to overcome the immunosuppressive tumor microenvironment. Novel T cell-directed therapies include chimeric antigen receptor (CAR) T cell therapies and bispecific antibodies that leverage the immune system's T cells to recognize and attack the tumor cells. Second-generation anti-BCMA CAR T cell therapies and bispecific antibodies that bind the tumor antigen BCMA or GPRC5D onto myeloma cells and CD3 on the T cell's surface are currently available for the treatment of relapsed/refractory multiple myeloma. Despite impressive results obtained with currently approved treatments, multiple myeloma remains incurable, and almost all patients eventually relapse. Moreover, patients with extramedullary disease and plasma cell leukemia represent an unmet medical need that require additional strategies to improve the outcome. In this review, we provide an overview of the evolution of risk stratification and the treatment of multiple myeloma.

Measurable Residual Disease Testing in Multiple Myeloma Following T-Cell Redirecting Therapies

Several novel T-cell-based therapies have recently become available for multiple myeloma (MM). These T-cell redirecting therapies (TRTs) include chimeric antigen receptor T-cells (CAR-T) and bispecific antibodies (BiAbs). In both clinical trial and real-world data, these therapies have demonstrated high rates of deep clinical response, and some are now approved for second-line treatment for relapsed MM. The deep and sustained clinical responses these therapies are capable of inducing will require sophisticated response monitoring to provide meaningful information for patient care. Obtaining measurable residual disease (MRD) negativity has been validated as an independent positive prognostic marker for progression-free survival (PFS) and overall survival (OS) in both newly diagnosed and relapsed refractory patients with multiple myeloma. Assessment for MRD negativity was performed in all of the trials for FDA-approved TRT. Here, we summarize pertinent data for MRD assessment following TRT in MM and provide a rationale and structured framework for conducting MRD testing post TRT.