Risk stratification in multiple myeloma: Are we there yet?

The second revision of international staging system (R2-ISS) shows promise in patients with multiple myeloma treated with a regimen of novel agent-based induction therapy, autologous stem cell transplant and maintenance therapy, but challenges persist. This study by Alzahrani et al. underscores the importance of refining risk assessment tools for tailored treatment strategies. Commentary on: Alzahrani et al. Impact of revised international staging system 2 (R2-ISS) risk stratification on outcomes of patients with multiple myeloma receiving autologous hematopoietic stem cell transplantation. Br J Haematol 2024;204:1944-1952.

Teclistamab in relapsed refractory multiple myeloma: multi-institutional real-world study.

The objective of our study was to report real-world data on the safety and efficacy of standard-of-care teclistamab in patients with relapsed/refractory multiple myeloma (MM). This is a multi-institutional retrospective cohort study and included all consecutive patients that received at least one dose of teclistamab up until August 2023. One hundred and ten patients were included, of whom, 86% had triple-class refractory disease, 76% penta-refractory disease, and 35% had prior exposure to B-cell maturation antigen (BCMA)-targeting therapies. The overall response rate (ORR) in our cohort was 62%, with a ≥ very good partial remission (VGPR) rate of 51%. The ORR in patients with and without prior BCMA-targeted therapies was 54% vs 67%, respectively (p = 0.23). At a median follow-up of 3.5 months (range, 0.39-10.92), the estimated 3 month and 6 month progression free survival (PFS) was 57% (95% CI, 48%, 68%) and 52% (95% CI, 42%, 64%) respectively. The incidence of cytokine release syndrome (CRS) and immune effector cell associated neurotoxicity syndrome (ICANS) was 56% and 11% respectively, with grade ≥3 CRS and ICANS noted in 3.5% and 4.6% of patients respectively. 78 unique infections were diagnosed in 44 patients, with the incidence of all-grade and grade ≥3 infections being 40% vs 26% respectively. Primary prophylaxis with intravenous immunoglobulin (IVIG) was associated with a significantly lower infection risk on multivariate analysis (Hazard ratio [HR] 0.33; 95% CI 0.17, 0.64; p = 0.001).

A Risk Stratification System in Myeloma Patients with Autologous Stem Cell Transplantation.

Autologous stem cell transplantation (ASCT) has been a mainstay in myeloma treatment for over three decades, but patient prognosis post-ASCT varies significantly. In a retrospective study of 5259 patients with multiple myeloma (MM) at the University of Arkansas for Medical Sciences undergoing ASCT with a median 57-month follow-up, we divided the dataset into training (70%) and validation (30%) subsets. Employing univariable and multivariable Cox analyses, we systematically assessed 29 clinical variables, identifying crucial adverse prognostic factors, such as extended duration between MM diagnosis and ASCT, elevated serum ferritin, and reduced transferrin levels. These factors could enhance existing prognostic models. Additionally, we pinpointed significant poor prognosis markers like high serum calcium and low platelet counts, though they are applicable to a smaller patient population. Utilizing seven easily accessible high-risk variables, we devised a four-stage system (ATM4S) with primary stage borders determined through K-adaptive partitioning. This staging system underwent validation in both the training dataset and an independent cohort of 514 ASCT-treated MM patients from the University of Iowa. We also explored cytogenetic risk factors within this staging system, emphasizing its potential clinical utility for refining prognostic assessments and guiding personalized treatment approaches.

Immunotherapy-resistant acute lymphoblastic leukemia cells exhibit reduced CD19 and CD22 expression and BTK pathway dependency.

While therapies targeting CD19 by antibodies, chimeric antigen receptor T cells (CAR-T), and T cell engagers have improved the response rates in B cell malignancies, the emergence of resistant cell populations with low CD19 expression can lead to relapsed disease. We developed an in vitro model of adaptive resistance facilitated by chronic exposure of leukemia cells to a CD19 immunotoxin. Single-cell RNA-Seq (scRNA-Seq) showed an increase in transcriptionally distinct CD19lo populations among resistant cells. Mass cytometry demonstrated that CD22 was also decreased in these CD19lo-resistant cells. An assay for transposase-accessible chromatin with sequencing (ATAC-Seq) showed decreased chromatin accessibility at promoters of both CD19 and CD22 in the resistant cell populations. Combined loss of both CD19 and CD22 antigens was validated in samples from pediatric and young adult patients with B cell acute lymphoblastic leukemia (B-ALL) that relapsed after CD19 CAR-T-targeted therapy. Functionally, resistant cells were characterized by slower growth and lower basal levels of MEK activation. CD19lo resistant cells exhibited preserved B cell receptor signaling and were more sensitive to both Bruton's tyrosine kinase (BTK) and MEK inhibition. These data demonstrate that resistance to CD19 immunotherapies can result in decreased expression of both CD19 and CD22 and can result in dependency on BTK pathways.

Autologous stem cell boost improves persistent immune effector cell associated hematotoxicity following BCMA directed chimeric antigen receptor T (CAR T) cell therapy in multiple myeloma.

Persistent Immune Effector Cell Associated Hematotoxicity (ICAHT) is a significant side effect of BCMA CAR T-Cell therapy in patients with relapsed multiple myeloma (MM). The use of stem cell boosts in ICAHT has been described, however studies have been limited by small patient numbers and short follow up. Herein, we report on our multi-institutional experience of ICAHT, defined by an absolute neutrophil count (ANC) of ≤ 1000, thrombocytopenia with a platelet count ≤ 50,000 or/and anemia as hemoglobin (hgb) ≤9 g/dL, in patients who received BCMA CAR T therapy, and the effects of subsequent stem cell boost on hematopoietic reconstitution and clinical outcome. In this study, ICAHT was observed in 60% (n = 61/101) of patients at D + 21, and risk factors for its development included history of a prior ASCT, higher number of prior lines of therapy, a decreased platelet count prior to lymphodepletion and history of ICANS. 28% of patients with ICAHT received a stem cell boost at a median of 116 days due to profound and prolonged cytopenias often requiring ongoing transfusion support. Stem cell boost significantly improved cytopenias at 3 and 6 months follow up without any adverse effects on PFS and OS, underscoring the safety of this procedure.

A NOTCH3-CXCL12-driven myeloma-tumor niche signaling axis promotes chemoresistance in multiple myeloma.

Multiple myeloma (MM) remains incurable due to disease relapse and drug resistance. Notch signals from the tumor microenvironment (TME) confer chemoresistance, but the cellular and molecular mechanisms are not entirely understood. Using clinical and transcriptomic datasets, we found that NOTCH3 is upregulated in CD138+ cells from newly diagnosed MM (NDMM) patients compared to healthy individuals and increased in progression/relapsed MM (PRMM) patients. Further, NDMM patients with high NOTCH3 expression exhibited worse responses to Bortezomib (BOR)-based therapies. Cells of the TME, including osteocytes, upregulated NOTCH3 in MM cells and protected them from apoptosis induced by BOR. NOTCH3 activation (NOTCH3OE) in MM cells decreased BOR anti-MM efficacy and its ability to improve survival in in vivo myeloma models. Molecular analyses revealed that NDMM and PRMM patients with high NOTCH3 exhibit CXCL12 upregulation. TME cells upregulated CXCL12 and activated the CXCR4 pathway in MM cells in a NOTCH3-dependent manner. Moreover, genetic or pharmacologic inhibition of CXCL12 in NOTCH3OE MM cells restored sensitivity to BOR regimes in vitro and in human bones bearing NOTCH3OE MM tumors cultured ex vivo. Our clinical and preclinical data unravel a novel NOTCH3-CXCL12 pro-survival signaling axis in the TME and suggest that osteocytes transmit chemoresistance signals to MM cells.

Bispecific BCMA/CD24 CAR-T cells control multiple myeloma growth.

Anti-multiple myeloma B cell maturation antigen (BCMA)-specific chimeric antigen receptor (CAR) T-cell therapies represent a promising treatment strategy with high response rates in myeloma. However, durable cures following anti-BCMA CAR-T cell treatment of myeloma are rare. One potential reason is that a small subset of minimal residual myeloma cells seeds relapse. Residual myeloma cells following BCMA-CAR-T-mediated treatment show less-differentiated features and express stem-like genes, including CD24. CD24-positive myeloma cells represent a large fraction of residual myeloma cells after BCMA-CAR-T therapy. In this work, we develop CD24-CAR-T cells and test their ability to eliminate myeloma cells. We find that CD24-CAR-T cells block the CD24-Siglec-10 pathway, thereby enhancing macrophage phagocytic clearance of myeloma cells. Additionally, CD24-CAR-T cells polarize macrophages to a M1-like phenotype. A dual-targeted BCMA-CD24-CAR-T exhibits improved efficacy compared to monospecific BCMA-CAR-T-cell therapy. This work presents an immunotherapeutic approach that targets myeloma cells and promotes tumor cell clearance by macrophages.

Impact of Clonal Heterogeneity in Multiple Myeloma.

Multiple myeloma is characterized by a highly heterogeneous disease distribution within the bone marrow-containing skeletal system. In this review, we introduce the molecular mechanisms underlying clonal heterogeneity and the spatio-temporal evolution of myeloma. We discuss the clinical impact of clonal heterogeneity, which is thought to be one of the biggest obstacles to overcome therapy resistance and to achieve cure.

Three years of maintenance with VRD in multiple myeloma: results of total therapy IIIB with a 15-year follow-up.

ABSTRACT: The total therapy (TT) IIIB phase 2 study incorporated bortezomib into tandem melphalan-based hematopoietic stem cell transplantation with dexamethasone, thalidomide, cisplatin, doxorubicin, cyclophosphamide, and etoposide for induction/consolidation and bortezomib, lenalidomide, and dexamethasone (VRD) for maintenance in patients with newly diagnosed multiple myeloma (MM). This updated analysis presents a 15.4-year median follow-up. Of 177 patients, 21% patients had gene expression profile (GEP)-defined high-risk MM. 15-year progression free survival (PFS) was 27.9%. Median PFS was better in GEP-defined low-risk patients at 7.8 years and in International Staging System stage 1 patients at 8.7 years. Overall, median OS was 9.1 years, and 15-year overall survival (OS) was 35.9%. GEP-defined low-risk patients' median OS was 11.2 years, and that of GEP-defined high-risk patients was 2.8 years. There was no difference in OS between TT IIIB and TT IIIA. This study includes the longest follow-up of patients treated with maintenance VRD reported to date. In patients with GEP-defined low-risk, nearly half and one-third of patients without ongoing treatment showed no signs of progression at 10 and 15 years, respectively. One-third of patients survived more than 15 years, but 3 years of VRD maintenance did not improve outcomes for patients with GEP-defined high-risk MM. The study was registered on www.clinicaltrials.gov as #NCT00572169.

The changing spectrum of infection with BCMA and GPRC5D targeting bispecific antibody (bsAb) therapy in patients with relapsed refractory multiple myeloma.

There is a paucity of granular data on infection risk with B-cell maturation antigen (BMCA) and GPRC5D bispecific antibodies (bsAb) in relapsed/refractory multiple myeloma (RRMM). The aim of our multi-institutional study was to characterize the incidence, etiologies, and risk factors of infections from the start of therapy to the last follow-up or 90 days after study exit. A total of 66 patients received BCMA bsAb monotherapy, 15 GPRC5D bsAb monotherapy, and 15 GPRC5D bsAb combination therapy with daratumumab and/or pomalidomide. While the infection rate per 100 days was 0.57 for BCMA bsAb, it was 0.62 for GPRC5D bsAb combination and 0.13 for GPRC5D bsAb monotherapy; P=0.05. The proportion of infections that were grade ≥3 was higher in the BCMA bsAb group compared to the GPRC5D groups (58% vs. 36%; P=0.04). Grade 5 events were observed in 8% (n=8) of the patients, all treated with BCMA bsAb. The 9 month cumulative incidence of any grade of infection was similar in the BCMA and GPRC5D-combination groups (57% and 62%) and significantly higher than in the GPRC5D-mono group (16%); P=0.012. The cumulative incidence of grade ≥3 infections was highest in the BCMA group reaching 54% at 18 months; P=0.06. Multivariate analysis showed that BCMA bsAb therapy or GPRC5D combination therapy, history of previous infections, baseline lymphopenia, and baseline hypogammaglobulinemia were significantly associated with a higher risk of grade ≥3 infections. Our results indicate that BCMA bsAb and GPRC5D-combination therapies in RRMM are associated with higher cumulative incidence of infection and grade ≥3 infection compared to GPRC5D bsAb mono.

Progression-Free Survival of Daratumumab Versus Bortezomib Triplet Combination With Lenalidomide and Dexamethasone in Transplant Ineligible Patients With Newly Diagnosed Multiple Myeloma: TAURUS Chart Review Study.

BACKGROUND: Daratumumab, lenalidomide and dexamethasone (DRd) and bortezomib, lenalidomide and dexamethasone (VRd) are preferred regimens for transplant ineligible (TIE) patients with newly diagnosed multiple myeloma (NDMM). Both DRd and VRd demonstrated superior efficacy versus Rd in the MAIA and SWOG S0777 trials, respectively, but there is no head-to-head (H2H) clinical trial comparing their efficacy. Differing populations in the MAIA and S0777 trials make an unadjusted comparison of outcomes challenging and biased. The current TAURUS study is the first real-world H2H study comparing progression-free survival (PFS) among TIE NDMM patients treated with DRd or VRd as first-line (1L) in similar clinical settings. MATERIALS AND METHODS: A multicenter chart review study was conducted at nine sites across the United States. All TIE patients treated with DRd and a randomly selected population of VRd patients were included. TIE NDMM patients aged ≥65 were included if they initiated 1L DRd/VRd between January 2019 and September 2021. PFS was defined as the time from DRd/VRd initiation until disease progression or death. A doubly-robust multivariable Cox regression model combined with inverse probability of treatment weighting (IPTW) methodology was used to compare PFS between cohorts. RESULTS: Weighted cohorts comprised 91 DRd and 87 VRd patients. Thirteen DRd and 24 VRd patients experienced progression/death. Patients treated with DRd had a lower risk of progression/death versus VRd (adjusted hazard ratio: 0.35, 95% confidence interval: [0.17; 0.73]). CONCLUSION: DRd is associated with a significantly lower risk of disease progression or death compared to VRd as 1L treatment for TIE NDMM patients.

BCMA- and CST6-specific CAR T cells lyse multiple myeloma cells and suppress murine osteolytic lesions.

We have previously demonstrated that cystatin E/M (CST6), which is elevated in a subset of patients with multiple myeloma (MM) lacking osteolytic lesions (OLs), suppresses MM bone disease by blocking osteoclast differentiation and function. CST6 is a secreted type 2 cystatin, a cysteine protease inhibitor that regulates lysosomal cysteine proteases and the asparaginyl endopeptidase legumain. Here, we developed B cell maturation antigen (BCMA) CST6 chimeric antigen receptor T cells (CAR-T cells), which lysed MM cells and released CST6 proteins. Our in vitro studies show that these CAR-T cells suppressed the differentiation and formation of tartrate-resistant acid phosphatase-positive (TRAP+) osteoclasts. Using xenografted MM mice, bioluminescence images showed that both BCMA-CAR-T and BCMA-CST6-CAR-T cells inhibited MM growth to a similar extent. Reconstructed micro-computed tomography images revealed that BCMA-CST6-CAR-T cells, but not BCMA-CAR-T cells, prevented MM-induced bone damage and decreased osteoclast numbers. Our results provide a CAR-T strategy that targets tumor cells directly and delivers an inhibitor of bone resorption.

High NEK2 expression in myeloid progenitors suppresses T cell immunity in multiple myeloma.

Multiple myeloma (MM) growth is supported by an immune-tolerant bone marrow microenvironment. Here, we find that loss of Never in mitosis gene A (NIMA)-related kinase 2 (NEK2) in tumor microenvironmental cells is associated with MM growth suppression. The absence of NEK2 leads to both fewer tumor-associated macrophages (TAMs) and inhibitory T cells. NEK2 expression in myeloid progenitor cells promotes the generation of functional TAMs when stimulated with MM conditional medium. Clinically, high NEK2 expression in MM cells is associated with increased CD8+ T effector memory cells, while low NEK2 is associated with an IFN-γ gene signature and activated T cell response. Inhibition of NEK2 upregulates PD-L1 expression in MM cells and myeloid cells. In a mouse model, the combination of NEK2 inhibitor INH154 with PD-L1 blockade effectively eliminates MM cells and prolongs survival. Our results provide strong evidence that NEK2 inhibition may overcome tumor immune escape and support its further clinical development.

EDNRA-Expressing Mesenchymal Cells Are Expanded in Myeloma Interstitial Bone Marrow and Associated with Disease Progression.

Multiple myeloma (MM) induces dysfunctional bone marrow (BM) mesenchymal cells and neoangiogenesis. Pericytes and smooth muscle cells (SMCs) could detach from vessels and become cancer-associated fibroblasts. We found that the pericyte and SMC marker endothelin receptor type A (EDNRA) is overexpressed in whole MM bone biopsies; we sought to characterize its expression. EDNRA expression gradually increased with disease progression. High-risk MM patients had higher EDNRA expression than low-risk MM patients and EDNRA expression was highest in focal lesions. High EDNRA expression was associated with high expression of pericyte markers (e.g., RGS5, POSTN, and CD146) and the angiogenic marker FLT1. A single-cell analysis of unexpanded BM mesenchymal cells detected EDNRA expression in a subset of cells that coexpressed mesenchymal cell markers and had higher expression of proliferation genes. Immunohistochemistry revealed that the number of EDNRA+ cells in the interstitial BM increased as MM progressed; EDNRA+ cells were prevalent in areas near the MM focal growth. EDNRA+ cells were detached from CD34+ angiogenic cells and coexpressed RGS5 and periostin. Therefore, they likely originated from pericytes or SMCs. These findings identify a novel microenvironmental biomarker in MM and suggest that the presence of detached EDNRA+ cells indicates disrupted vasculature and increased angiogenesis.

Resolving the spatial architecture of myeloma and its microenvironment at the single-cell level.

In multiple myeloma spatial differences in the subclonal architecture, molecular signatures and composition of the microenvironment remain poorly characterized. To address this shortcoming, we perform multi-region sequencing on paired random bone marrow and focal lesion samples from 17 newly diagnosed patients. Using single-cell RNA- and ATAC-seq we find a median of 6 tumor subclones per patient and unique subclones in focal lesions. Genetically identical subclones display different levels of spatial transcriptional plasticity, including nearly identical profiles and pronounced heterogeneity at different sites, which can include differential expression of immunotherapy targets, such as CD20 and CD38. Macrophages are significantly depleted in the microenvironment of focal lesions. We observe proportional changes in the T-cell repertoire but no site-specific expansion of T-cell clones in intramedullary lesions. In conclusion, our results demonstrate the relevance of considering spatial heterogeneity in multiple myeloma with potential implications for models of cell-cell interactions and disease progression.

Growth and dormancy control of myeloma cells by mesenchymal stem cells.

Bone marrow mesenchymal stem cells (MSCs) may have contrasting impacts on the progression of multiple myeloma (MM). Priming normal MSCs, by culturing them with MM cells, mimics the MSC-induced MM growth. We studied the contrasting effects of conditioned medium (CM) from unprimed or primed MSCs on growth of MM cells from newly diagnosed cases. We elucidated potential molecular pathways using global gene expression profiling and focused on the role of the mTOR2 component, RICTOR, as a novel mediator of dormancy in MM. Primed MSCs CM consistently increased proportions of proliferating cells and supported MM growth in 3-day (n = 20) and 10-day (n = 12) cultures, effects that were partially mediated through the IGF1 axis. In contrast, unprimed MSCs CM inhibited growth of MM cells in cases mainly from stages I/II MM. The genes most overexpressed in MM cells treated with primed MSCs CM were associated with cell cycle, DNA-damage repair, and proliferation; genes most overexpressed in MM cells treated with unprimed MSCs CM were associated with dormancy pathways including RICTOR (mTOR2 pathway), CXCR4, and BCL2. RICTOR protein level was induced by unprimed MSCs CM and was lower in KI67+ proliferating MM cells treated with primed MSCs CM. RICTOR was underexpressed in clinical relapse samples compared with baseline samples of the same patients. Inhibiting RICTOR expression in primary MM cells promoted their growth, and enforced expression of RICTOR in MM cell lines inhibited their growth. Our findings suggest that, after prolonged interactions with MM cells, bone marrow MSCs shift from MM-repressive to MM-permissive. AVAILABILITY OF DATA AND MATERIALS: Our institutional GEP data of MM cells from newly diagnosed patients used to show RICTOR expression have been deposited at Gene Expression Omnibus (GEO: GSE2658, https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE2658).