Soluble B‐cell Maturation Antigen in Multiple Myeloma and Correlation With Response to Therapy

Examining the Clinical Heterogeneity of Smoldering Multiple Myeloma

Multiple myeloma (MM) patients with smoldering (S) disease are defined by a lack of CRAB/SLiM criteria but may transform into disease requiring treatment. The International Myeloma Working Group risk stratification model for SMM uses serum M-protein, serum-free light chain ratio, and bone marrow plasma cell percentage. We investigated whether baseline serum B-cell maturation antigen (sBCMA) levels are predictive of disease progression among 65 patients with SMM. A receiver operating characteristic curve was used to establish a definition for high-risk baseline sBCMA. Mantel Byar analysis was used to examine whether high-risk sBCMA was correlated with shorter time to transformation, and a time-dependent cox proportional hazard was used to determine whether it is independent of other risk factors. A z test for proportions was used to compare the percentage of patients that progressed among high-risk versus low-risk sBCMA patients. A baseline sBCMA level ≥137.5mg/ml was found to be the optimal cutoff between high- and low-risk SMM patients. Patients with high-risk sBCMA levels had a shorter time to transformation (P=.000332). sBCMA was also higher at the time of transformation than baseline levels (P=.0116). sBCMA was the only variable found to be significantly predictive of time to transformation and additionally was found to be independent of other risk factors. In this study, we have shown for the first time that sBCMA levels predict transformation of SMM to active disease and that these levels increase at the time of transformation. These results are consistent with other studies showing that active MM patients undergoing therapy with higher baseline sBCMA levels are more likely to progress early and its levels increase at the time of disease progression.

Serum B-cell maturation antigen (sBCMA) levels can serve as a sensitive biomarker in multiple myeloma (MM). In the research setting, sBCMA levels can be accurately detected by enzyme-linked immunosorbent assay (ELISA), but the approach has not been approved for clinical use. Here, we used a novel chemiluminescence method to assess sBCMA levels in 759 serum samples from 17 healthy donors and 443 patients with plasma cell (PC) diseases including AL amyloidosis, POEMS syndrome, and MM. Serum BCMA levels were elevated 16.1-fold in patients with newly diagnosed MM compared to healthy donors and rare PC diseases patients. Specifically, the sBCMA levels in patients with progressive disease were 64.6-fold higher than those who showed partial response or above to treatment. The sBCMA level also correlated negatively with the response depth of MM patients. In newly diagnosed and relapsed MM patients, survival was significantly longer among those subjects whose sBCMA levels are below the median levels compared with those above the median value. We optimized the accuracy of the survival prediction further by integrating sBCMA level into the Second Revised International Staging System (R2-ISS). Our findings provide evidence that the novel chemiluminescence method is sensitive and practical for measuring sBCMA levels in clinical samples and confirm that sBCMA might serve as an independent prognostic biomarker for MM.

B-cell maturation antigen (BCMA) is selectively expressed as a surface protein on plasma cells and is a validated target for multiple myeloma (MM). A soluble form of BCMA (sBCMA) is elevated in the sera of patients with MM. The bispecific antibodies teclistamab (BCMA×CD3) and talquetamab (G protein-coupled receptor family C group 5 member D [GPRC5D]×CD3) are in clinical development as therapies for MM. Using data from patients with relapsed/refractory MM (N=300) who participated in phase 1 studies of teclistamab (NCT03145181) or talquetamab (NCT03399799), baseline serum sBCMA levels were quantitatively analyzed relative to response to treatment, percentage of bone marrow plasma cells (BMPCs), and cytogenetic risk. By cycle 3 day 1 of treatment, sBCMA levels declined from baseline in 50 (88%) of 57 responders and 49 (98%) of 50 responders to teclistamab and talquetamab, respectively. Depth of response correlated with the magnitude of sBCMA reduction. In contrast, sBCMA increased in 33 (80%) of 41 patients and 24 (49%) of 49 patients who did not respond to teclistamab or talquetamab, respectively. Baseline sBCMA levels correlated with the percentage of BMPC; patients with extramedullary plasmacytomas who had low levels of BMPC (≤10%) tended to have high baseline sBCMA levels (≥400 ng/mL), based on limited data. Baseline sBCMA levels and changes in sBCMA levels at cycle 3 day 1 were similar in patients with high- and standard-risk cytogenetics treated with teclistamab or talquetamab. These results support the use of sBCMA as a potential surrogate marker of tumor burden and treatment response in MM.

Changes in Serum B-Cell Maturation Antigen Levels Rapidly Indicate Changes in Clinical Status Among Multiple Myeloma Patients Undergoing New Treatments

B-Cell Maturation Antigen (BCMA) in Systemic Light-Chain Amyloidosis (AL): Association with Disease Activity and Its Modulation with Gamma-Secretase Inhibition

Soluble BCMA As a Surrogate Biomarker for Tumor Burden in Multiple Myeloma: Correlations with Various Biomarkers and Treatment Responses

Changes in Serum B-Cell Maturation Antigen Levels Are a More Rapid Indicator of Therapeutic Response or Disease Progression for Patients with Multiple Myeloma

Previous retrospective studies have shown that serum B-cell maturation antigen (sBCMA) levels predict outcomes among patients with multiple myeloma (MM) undergoing new treatments. Specifically, baseline levels and changes during treatment of this protein predict both progression free survival (PFS) and overall survival. However, prospective studies are lacking evaluating sBCMA for determining outcomes among MM patients undergoing new treatments. Thus, we evaluated whether its baseline levels and changes during treatment in the amount of this serum marker predict outcomes among 38 relapsed/refractory MM patients treated with ruxolitinib, lenalidomide and methylprednisolone in a phase 1 trial. Patients with baseline sBCMA levels in the lowest three quartiles had longer PFS (median PFS 136 vs. 28days; p<0.0001). This was also shown for patients with baseline levels below the median (median PFS 140 vs. 77days; p=0.0225). PFS was shorter for patients whose sBCMA levels increased ≥25% through their first cycle (median PFS: 50 vs. 134days, p=0.0022), second cycle (median PFS: 50 vs. 141days, p=0.0273), and during the first three cycles of study treatment (median PFS: 50 vs. 220days, p<0.0001). No patient whose sBCMA increased ≥25% during cycle 1 responded whereas the majority (58%) of patients whose level increased <25% responded. This is the first prospective study to determine whether sBCMA levels predict outcomes for MM patients undergoing a non-BCMA directed treatment regimen and demonstrates that baseline levels and its changes during treatment predict PFS and the likelihood of responding to their treatment. These results add to the growing literature suggesting that this serum marker will be useful for determining outcomes for patients undergoing treatment for MM.

Soluble B-Cell Maturation Antigen Levels for Disease Monitoring in Oligo- and Non-Secretory Relapsed Multiple Myeloma

This study aimed to investigate whether soluble B-cell maturation antigen (sBCMA) levels could be predictive biomarker for short-term and long-term therapeutic efficacy and survival outcomes following anti-BCMA CAR-T cell therapy in relapsed/refractory multiple myeloma (R/R MM). We enrolled 29 R/R MM patients who received anti-BCMA CAR-T cell therapy. In short-term observation, proportion of MM cells, expression of B-cell maturation antigen (BCMA) and sBCMA in bone marrow (BM) were evaluated, along with adverse events, correlation between sBCMA levels and short-term efficacy or survival outcomes were evaluated. In long-term observation, expressions of sBCMA were observed up to 24 months after therapy or until disease progression again in patients who achieved an objective response (ORR). Progression-free survival (PFS), overall survival (OS), correlation between sBCMA levels, and long-term outcomes were analyzed. In short-term observation, high expressions of sBCMA in BM were associated with poor efficacy of CAR-T cell therapy, while the proportion of MM cells in BM and BCMA expression in MM cells were not associated with poor efficacy of therapy. After 2 months of infusion, sBCMA levels decreased significantly, especially in patients who obtained ORR. In long-term follow-up, for patients who achieved ORR, the sBCMA levels significantly increased again when their disease progressed once more. Notably, R/R MM patients with extramedullary disease (EMD) demonstrated a higher likelihood of disease progression again. In patients achieved ORR, peaks of CAR-T cells correlated with proportion of MM cells, not with BCMA and sBCMA expression. Additionally, sBCMA levels were independent of cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) severity. We suggest that sBCMA levels in BM might serve as a predictive biomarker for anti-BCMA CAR-T cell therapy efficacy prior to treatment and for disease progression during long-term monitoring. The trail register name is China Clinical Trial Register. URL are https://www.chictr.org.cn/bin/project/edit?pid=28999 and https://www.chictr.org.cn/bin/project/edit?pid=53962. Registration numbers are ChiCTR1800017051 and ChiCTR2000033925.

Comparative Analysis of sSLAMF7, sBCMA, and M-Protein As Prognostic, Predictive, and Pharmacodynamic Biomarkers in Relapsed/Refractory Multiple Myeloma Treated with Pomalidomide and Dexamethasone +/- Elotuzumab

Baseline and Early Changes in Serum B-Cell Maturation Antigen Levels Predict Progression Free Survival and Response Status for Multiple Myeloma Patients in a Phase 1 Trial Evaluating Ruxolitinib, Lenalidomide and Methylprednisolone

Sprouty2 regulates proliferation and survival of multiple myeloma byinhibiting activation of the ERK1/2 pathway invitro and invivo.

Objective: Response to treatment in multiple myeloma (MM) is routinely measured by serum and urine M-protein and free light chain (FLC), as described by the International Myeloma Working Group (IMWG) consensus statement. A non-negligible subgroup of patients however present without measurable biomarkers, others become oligo or non-secretory during recurrent relapses. The aim of our research was to evaluate soluble B-cell maturation antigen (sBCMA) as a monitoring marker measured concurrent with the standard monitoring in MM patients at diagnosis, at relapse and during follow up, in order to establish its potential usefulness in oligo and non-secretory disease. Method: sBCMA levels were measured in 149 patients treated for plasma cell dyscrasia (3 monoclonal gammopathy of unknown significance, 5 smoldering myeloma, 7 plasmacytoma, 8 AL amyloidosis and 126MM) and 16 control subjects using a commercial ELISA kit. In 43 newly diagnosed patients sBCMA levels were measured at multiple timepoints during treatment, and compared to conventional IMWG response and progression free survival (PFS). Results: sBCMA levels among control subjects were significantly lower than among newly diagnosed or relapsed MM patients [20.8 (14.7-38.7) ng/mL vs. 676 (89.5-1,650) and 264 (20.7-1,603) ng/mL, respectively]. Significant correlations were found between sBCMA and the degree of bone marrow plasma cell infiltration. Out of the 37 newly diagnosed patients who have reached partial response or better per IMWG criteria, 33 (89%) have had at least a 50% drop in sBCMA level by therapy week 4. Cohorts made similarly to IMWG response criteria-achieving a 50% or 90% drop in sBCMA levels compared to level at diagnosis-had statistically significant differences in PFS. Conclusion: Our results confirmed that sBCMA levels are prognostic at important decision points in myeloma, and the percentage of BCMA change is predictive for PFS. This highlights the great potential use of sBCMA in oligo- and non-secretory myeloma.