Functional cure and long-term survival in multiple myeloma: how to challenge the previously impossible

Multiple myeloma (MM) is a heterogeneous disease with survival ranging from months to decades. The goal of ‘cure’ remains elusive for most patients, but has been shown to be possible, with durable remission and a transition to a plateau phase (analogous to monoclonal gammopathy of uncertain significance/smoldering Myeloma (MGUS/SMM)). Two representative cases set the stage to illustrate how this might be possible and what still needs to be determined to achieve functional disease control over a prolonged period. Several developments have emerged, such as improved diagnostics including the definitions and use of SLiM-CRAB criteria and MRD with whole genome- /single-cell-sequencing as well as other correlates to better understand disease biology. These advances enable earlier detection, more accurate risk stratification and improved personalized treatment strategies by facilitating analysis of genetic alterations and clonal heterogeneity. Whole genome sequencing may also identify driver mutations and modes of resistance to targets like immunotherapies (IOs) as well as other targeted therapies. Today, induction with a CD38 antibody (CD38mAb), proteasome inhibitor, immunomodulatory drug, and dexamethasone, potentially followed by ASCT and lenalidomide maintenance, can be considered standard of care for transplant-eligible (TE) newly diagnosed (NDMM) patients. Whether prolonged disease control and functional cure can be achieved in non-transplant eligible (NTE) patients is currently emerging as a distinct possibility: data from phase III trials that incorporate a CD38mAb into the treatment of NTE NDMM patients demonstrate impressive MRD negativity rates that appear sustained over several years. While the long-term durability of CAR-Ts, bi-specific antibodies and other IOs are evaluated, several clinical trials are now investigating their role in frontline treatment for TE and NTE patients. These will address whether CAR-Ts will replace ASCT and whether such IOs will represent a truly curative option. We conclude that whilst cure remains elusive, the concept of operational or functional cure provides a new benchmark to strive for and is an emerging area of active and potentially achievable clinical research for MM

BCMA loss in the epoch of novel immunotherapy for multiple myeloma: from biology to clinical practice

The treatment of multiple myeloma (MM) is evolving rapidly. In the past few years, chimeric antigen receptor modified T cells and bispecific antibodies are bringing new treatment options to patients with relapsed/refractory MM. Currently, B-cell maturation antigen (BCMA) has emerged as the most commonly used target of T-cell-based immunotherapies for relapsed/refractory MM. Clinical data have demonstrated promising efficacy and manageable safety profiles of both chimeric antigen receptor T-cell and bispecific antibody therapies in heavily pretreated relapsed/refractory MM. However, most patients suffer from relapses at later time points, and the mechanism of resistance remains largely unknown. Theoretically, loss of antigen is a potential tumor-intrinsic resistance mechanism against BCMA-targeted immunotherapies. Strategies to overcome this kind of drug resistance are, therefore, needed. In this review, we discuss the loss of BCMA in the new epoch of immunotherapy for MM

11C-Methionine-PET in multiple myeloma: a combined study from two different institutions

$^{11}$C-methionine (MET) has recently emerged as an accurate marker of tumor burden and disease activity in patients with multiple myeloma (MM). This dual-center study aimed at further corroboration of the superiority of MET as positron emission tomography (PET) tracer for staging and re-staging MM, as compared to $^{18}$F-2`-deoxy-2`-fluoro-D-glucose (FDG). 78 patients with a history of solitary plasmacytoma (n=4), smoldering MM (SMM, n=5), and symptomatic MM (n=69) underwent both MET- and FDG-PET/computed tomography (CT) at the University Centers of Würzburg, Germany and Navarra, Spain. Scans were compared on a patient and on a lesion basis. Inter-reader agreement was also evaluated. In 2 patients, tumor biopsies for verification of discordant imaging results were available. MET-PET detected focal lesions (FL) in 59/78 subjects (75.6%), whereas FDG-PET/CT showed lesions in only 47 patients (60.3%; p<0.01), accordingly disease activity would have been missed in 12 patients. Directed biopsies of discordant results confirmed MET-PET/CT results in both cases. MET depicted more FL in 44 patients (56.4%; p<0.01), whereas in two patients (2/78), FDG proved superior. In the remainder (41.0%, 32/78), both tracers yielded comparable results. Inter-reader agreement for MET was higher than for FDG (κ = 0.82 vs κ = 0.72). This study demonstrates higher sensitivity of MET in comparison to standard FDG to detect intra- and extramedullary MM including histologic evidence of FDG-negative, viable disease exclusively detectable by MET-PET/CT. MET holds the potential to replace FDG as functional imaging standard for staging and re-staging of MM

Quasi-one-dimensional antiferromagnetism and multiferroicity in CuCrO4_4

The bulk magnetic properties of the new quasi-one-dimensional Heisenberg antiferromagnet, CuCrO$_4$, were characterized by magnetic susceptibility, heat capacity, optical spectroscopy, EPR and dielectric capacitance measurements and density functional evaluations of the intra- and interchain spin exchange interactions. We found type-II multiferroicity below the N\'{e}el temperature of 8.2(5) K, arising from competing antiferromagnetic nearest-neighbor ($J_{\rm nn}$) and next-nearest-neighbor ($J_{\rm nnn}$) intra-chain spin exchange interactions. Experimental and theoretical results indicate that the ratio $J_{\rm nn}/J_{\rm nnn}$ is close to 2, putting CuCrO$_4$ in the vicinity of the Majumdar-Ghosh point.Comment: 9 pages, 8 figures, submitted to PR

Reduced splenic uptake on 68Ga-Pentixafor-PET/CT imaging in multiple myeloma - a potential imaging biomarker for disease prognosis

Beyond being a key factor for tumor growth and metastasis in human cancer, C-X-C motif chemokine receptor 4 (CXCR4) is also highly expressed by a number of immune cells, allowing for non-invasive read-out of inflammatory activity. With two recent studies reporting on prognostic implications of the spleen signal in diffusion-weighted magnetic resonance imaging in patients with plasma cell dyscrasias, the aim of this study was to correlate splenic (68)Ga-Pentixafor uptake in multiple myeloma (MM) with clinical parameters and to evaluate its prognostic impact. METHODS: Eighty-seven MM patients underwent molecular imaging with (68)Ga-Pentixafor-PET/CT. Splenic CXCR4 expression was semi-quantitatively assessed by peak standardized uptake values (SUV(peak)) and corresponding spleen-to-bloodpool ratios (TBR) and correlated with clinical and prognostic features as well as survival parameters. RESULTS: (68)Ga-Pentixafor-PET/CT was visually positive in all MM patients with markedly heterogeneous tracer uptake in the spleen. CXCR4 expression determined by (68)Ga-Pentixafor-PET/CT corresponded with advanced disease and was inversely associated with the number of previous treatment lines as compared to controls or untreated smouldering multiple myeloma patients (SUV(peak)Spleen 4.06 ± 1.43 vs. 6.02 ± 1.16 vs. 7.33 ± 1.40; (P5.79 ((P<) 0.001). Multivariate Cox analysis confirmed SUV(peak)Spleen as an independent predictor of survival (HR 0.75;P= 0.009). CONCLUSION: These data suggest that splenic (68)Ga-Pentixafor uptake might provide prognostic information in pre-treated MM patients similar to what was reported for diffusion-weighted magnetic resonance imaging. Further research to elucidate the underlying biologic implications is warranted

IKZF1/3 and CRL4-CRBN E3 ubiquitin ligase mutations and IMiD resistance in multiple myeloma

The work was supported by the Deutsche Forschungsgemeinschaft (KFO216), the IZKF, the BTHA and the CDW Stiftung (KMK). UM was supported by a grant of the German Excellence Initiative to the Graduate School of Life Sciences, University of Würzburg.S

Supplementary Appendix. All-trans retinoic acid works synergistically with the γ- secretase inhibitor crenigacestat to augment BCMA on multiple myeloma and the efficacy of BCMA-CAR T cells

Supplement Figure 1: ATRA treatment does not affect the viability of myeloma cell lines. MM.1S, OPM-2 and NCI-H929 cells were treated with ATRA for up to 72 hours. Cell viability was measured by flow cytometry and 7AAD staining (n=6). Bar diagrams show mean values +SD.Supplement Figure 2: ATRA plus crenigacestat treatment enhance BCMA expression on myeloma cell lines. Bar diagram shows BCMA expression on OPM-2 cells (n=3) after treatment with 100 nM ATRA and/or 10 nM GSI crenigacestat for 72 hours. Bar diagram shows mean values +SD. P-values between indicated groups were calculated using unpaired t-test. *p<0.05, **p<0.01.Supplement Figure 3: ATRA treatment leads to increased BCMA transcripts in OPM-2 myeloma cells. BCMA RNA levels in OPM-2 were analyzed by quantitative reverse transcription PCR (qRT-PCR) assay after incubation with increasing doses of ATRA for 48 hours (n=3). Bar diagram shows mean values +SD. P-values between indicated groups were calculated using unpaired t-test. *p<0.05.Supplement Figure 4: ATRA treatment leads to enhanced BCMA expression on primary myeloma cells. Representative flow cytometric analysis of BCMA expression on primary myeloma cells that had been cultured in the absence or presence of ATRA at different concentrations for 72 hours. 7-AAD was used to exclude dead cells from analysis.Supplement Figure 5: ATRA treatment does not impair viability of primary myeloma cells. Viability of primary myeloma cells with or without 72 hours of ATRA treatment was analyzed by flow cytometry and 7-AAD staining (n=5 biological replicates). Bar diagram shows mean values +SD.Supplement Figure 6: sBCMA does not impair BCMA CAR T cell functionality. CD8+ BCMA-CAR T-cells were co-cultured with MM.1S target cells in absence or presence of 150 ng/ml of soluble BCMA. After 4 hours, cytotoxicity was evaluated by bioluminescence- based assay. Diagram shows mean values +/-SD.Supplement Figure 7: ATRA treatment does not increase shedding of sBCMA. sBCMA concentration in the supernatant of OPM-2 and NCI-H929 after incubation with increasing doses of ATRA was analyzed by ELISA. Cell lines were cultured at 1x106/well (n=3 technical replicates). Bar diagrams show mean values +SD, P-values between indicated groups were calculated using 2way ANOVA. n.s. = not significant, *p<0.05, **p<0.01.Supplement Figure 8: BCMA-CAR T-cells confer enhanced cytotoxicity against ATRA plus crenigacestat-treated OPM-2 cells in vitro. OPM-2 cells were incubated with 100 nM ATRA and/or 10 nM GSI for 72 hours or were left untreated. Cytolytic activity of CD8+ BCMA- CAR T-cells was determined in a bioluminescence-based assay after 4h of co-incubation with target cells. Assay was performed in triplicate wells with 5,000 target cells per well. Data are presented as mean values +SD (n=4 biological replicates). P-values between indicated groups were calculated using unpaired t-test. n.s. = not significant, *p<0.05.Supplement Figure 9: Patient-derived BCMA-CAR T-cells confer enhanced cytotoxicity against ATRA-treated MM.1S cells. MM.1S cells were incubated with 50 nM ATRA for 72 hours or were left untreated. Cytolytic activity of MM patient-derived CD8+ BCMA-CAR T-cells was determined in a bioluminescence-based assay after 4h of co-incubation with target cells. Data are presented as mean values +SD of triplicate wells. P-values between indicated groups were calculated using unpaired t-test. *p<0.05, **p<0.01.Peer reviewe

Soluble B-cell maturation antigen in lacrimal fluid as a potential biomarker and mediator of keratopathy in multiple myeloma

Belantamab mafodotin (belantamab) is a first-in-class anti-BCMA antibody-drug conjugate approved for the treatment of triple-class refractory multiple myeloma. It provides a unique therapeutic option for patients ineligible for CAR-T and bispecific antibody therapy, and/or patients progressing on anti-CD38 treatment where CAR-T and bispecifics might be kept in reserve. Wider use of the drug can be challenged by its distinct ocular side effect profile, including corneal microcysts and keratopathy. While dose reduction has been the most effective way to reduce these toxicities, the underlying mechanism of this BCMA off-target effect remains to be characterized. In this study, we provide the first evidence for soluble BCMA (sBCMA) in lacrimal fluid and report on its correlation with tumor burden in myeloma patients. We confirm that corneal cells do not express BCMA, and show that sBCMA-belantamab complexes may rather be internalized by corneal epithelial cells through receptor-ligand independent pinocytosis. Using an hTcEpi corneal cell-line model, we show that the pinocytosis inhibitor EIPA significantly reduces belantamab-specific cell killing. As a proof of concept, we provide detailed patient profiles demonstrating that, after belantamab-induced cell killing, sBCMA is released into circulation, followed by a delayed increase of sBCMA in the tear fluid and subsequent onset of keratopathy. Based on the proposed mechanism, pinocytosis-induced keratopathy can be prevented by lowering the entry of sBCMA into the lacrimal fluid. Future therapeutic concepts may therefore consist of belantamab-free debulking therapy prior to belantamab consolidation and/or concomitant use of gamma-secretase inhibition as currently evaluated for belantamab and nirogacestat in ongoing studies