BACKGROUND:Pomalidomide-daratumumab-dexamethasone (DPd) has been shown to be effective in lenalidomide-exposed patients with multiple myeloma (MM). We aimed to evaluate this combination in patients with del(17p), for whom there is no specific treatment. PATIENTS AND METHODS:The phase II DEDALO study enrolled patients with relapsed/refractory (RR)MM, del(17p), and ≤ 3 previous therapy lines including lenalidomide. Patients received DPd according to the approved schedule. The primary endpoint was minimal residual disease (MRD) negativity (by next-generation sequencing, 10-5 sensitivity). RESULTS:Fifty patients were enrolled, and 45 were eligible. A del(17p) clone size ≥ 55% was observed in 26/45 patients, while TP53 mutations in 10/31. One patient achieved MRD negativity. With a median follow-up of 18.7 months, the median progression-free survival (PFS) was 7.0 months (4.3-13.9) overall, 6.5 in patients with a del(17p) clone size < 55%, 7.6 in those with a clone size ≥ 55%, 3.2 in those with biallelic TP53 alteration, and 11.8 in those with isolated del(17p). Toxicity was consistent with previous studies. CONCLUSION:This is the first study testing a specific treatment for MM patients with del(17p). We confirmed the severity of this abnormality, particularly in the presence of double TP53 inactivation, and the importance of a thorough biological characterization.

ABSTRACT:Circulating tumor cells (CTC) represent a high-risk biomarker in newly diagnosed multiple myeloma (NDMM); however, their prognostic value among transplant-eligible (TE) patients receiving daratumumab/bortezomib/lenalidomide/dexamethasone (D-VRd) remains unknown. In this study, we analyzed CTC in the phase 3 PERSEUS/EMN017 trial. TE-NDMM patients were randomized (1:1) to D-VRd with daratumumab/lenalidomide maintenance (D-VRd group) or bortezomib/lenalidomide/dexamethasone (VRd) with lenalidomide maintenance (VRd group), both with transplant. A subset of 451 of 709 patients from PERSEUS (D-VRd, 231/355; VRd, 220/354) had screening blood samples collected for CTC analysis by flow cytometry. CTC were detected in 370 patients (82%; median limit of detection, 0.0004%). CTC were prognostic of progression-free survival (PFS), independent of other factors, as a continuous (hazard ratio [HR], 1.36 [95% confidence interval (CI), 1.15-1.60]; P< .001) and categorical variable (≥0.175% CTC-high, optimal threshold). D-VRd improved PFS vs VRd in CTC-low patients (4-year rates: 88% vs 74%; HR, 0.42 [95% CI, 0.25-0.70]; P = .0013). Regardless of study treatment, minimal residual disease (MRD)-negativity rates were lower in CTC-high vs CTC-low patients (10-5: 52.2% vs 66.2%; 10-6: 34.8% vs 52.4%). D-VRd significantly increased MRD-negativity rates vs VRd among CTC-high (10-5: 69.4% vs 33.3%; 10-6: 47.2% vs 21.2%; both P< .05) and CTC-low patients (10-5: 74.4% vs 57.8%; 10-6: 65.6% vs 38.5%; both P< .001), with similar observations for sustained MRD-negativity. CTC levels are an independent prognostic factor in TE-NDMM treated with standard-of-care frontline quadruplet. D-VRd improved and sustained MRD-negativity rates in CTC-high and CTC-low, and improved PFS for CTC-low with a positive trend in CTC-high patients. This trial was registered at www.clinicaltrials.gov as #NCT03710603.

Distribution of B-cell differentiation stages.

Differentially expressed genes in non-clonotypic cells.

List of somatic mutations detected in normal cells.

Oligoclonal expansions in non-clotypic cells.

The treatment of Multiple myeloma (MM) has been revolutionized by the advent of immunotherapies. Monoclonal antibodies targeting specific markers greatly contributed to patients’ outcome improvement. Antibodies can be conjugated with a toxic payload to exert anti-tumor efficacy (antibody–drug conjugates, ADCs). ADCs combine direct cytotoxicity with immune-mediated effects, potentially sustaining antimyeloma activity even with prolonged dosing intervals. B-cell maturation antigen (BCMA) is selectively expressed on plasma cells, including malignant clones and represents a validated target in MM. Belantamab-mafodotin is the first in class anti-BCMA ADC approved in MM. The drug demonstrated single agent activity in heavily pretreated MM patients enrolled in the phase II DREAMM-2 trial. However, the confirmatory phase III DREAMM-3 trial failed to show superiority over standard therapy, leading to a temporary withdrawal of its approval by regulatory agencies. Despite this setback, recent data from the DREAMM-7 and DREAMM-8 trials have renewed interest in Belantamab-mafodotin, showing a benefit over standard of care treatments when evaluated in earlier lines of therapy and in combination with known therapeutic backbones. Recently, other ADCs against BCMA or other targets are being developed. This review aims to explore the current clinical positioning of ADCs within MM therapeutic landscape and their possible future development.

Differentially expressed genes in clonotypic cells.

Frequency of non-clonotypic clones.

Single-cell transcriptomes excluding immunoglobulin genes.

Functional analysis of deregulated genes in non-clonotypic cells.

Characteristics and methods of study cohorts.

Proteasome inhibitors (PIs) are cornerstone therapies for multiple myeloma (MM), yet resistance remains a major barrier to durable responses. To identify druggable vulnerabilities that enhance PI efficacy, we performed a small-molecule chemical screen in the presence of carfilzomib (CFZ). We identified bedaquiline (BDQ), an FDAapproved antimycobacterial agent, as a potent synergistic partner. BDQ and its fumarate salt (BDQ-F) significantly amplified CFZ-induced cytotoxicity in PI-sensitive and PI-resistant MM cells, in AL amyloidosis and other B-cell malignancies, with minimal toxicity toward normal cells. Mechanistic studies confirmed that BDQ specifically targets the ATP5F1C subunit of mitochondrial ATP synthase. BDQ-CFZ combination triggered extensive apoptosis, exacerbating proteotoxic stress and proteasome-associated pathways. BDQ specifically enhanced CFZ's inhibition of the proteasome’s chymotrypsin-like activity. Importantly, BDQ synergized with multiple proteasome and ubiquitin-activating enzyme inhibitors, but not with other standard MM agents, underscoring its selective interaction with the UPS pathway. BDQ-CFZ cotreatment markedly reduced MM cell viability and tumor burden in patient-derived cells and zebrafish xenograft models. These findings support the therapeutic repurposing of BDQ to potentiate PI efficacy and overcome resistance in MM and related B-cell malignancies.

Differential gene expression across B-cell differentiation stages.

List of copy number variants (CNV).

Proteasome inhibitors (PIs) are central to multiple myeloma (MM) therapy; however, resistance remains a major clinical challenge, particularly in relapsed/refractory disease. To identify functional mediators of carfilzomib (CFZ) resistance, we performed complementary gain-of-function CRISPR activation and pharmacological screening approaches. These unbiased strategies converged on the E3 ubiquitin ligase MDM2 as a modulator of PI response. MDM2 transactivation enhanced MM cell survival and accelerated recovery following CFZ exposure, supporting a causal role in proteotoxic stress tolerance. Pharmacologic inhibition of MDM2 with NVP-CGM097 synergized with CFZ across multiple PI-sensitive and PI-resistant MM cell lines, irrespective of TP53 status. Mechanistically, MDM2 inhibition induced p21 upregulation, cell-cycle arrest, and reduced c-MYC expression, accompanied by impaired activation of DNA damage response mediators. Genetic silencing of MDM2 phenocopied these effects and increased CFZ sensitivity. Importantly, the combination retained efficacy in MM-stromal co-culture models and in primary patient samples, including cases harboring del(17p), while sparing normal peripheral blood mononuclear cells. Collectively, these findings identify MDM2 as a functional driver of PI resistance and support combined MDM2 and proteasome inhibition as a rational therapeutic strategy in MM, including TP53-deficient contexts.

Abstract Whether multiple myeloma (MM) and light-chain amyloidosis (AL) stem from terminally differentiated plasma cells (PC) or earlier clonotypic B cells remains under debate. Addressing this issue would improve accurate diagnosis and treatment monitoring. We performed single-cell and exome sequencing on highly purified MM and AL samples to define in which B-cell development stage the driver genetic alterations are present. Clonotypic B-cell receptors (BCR) were detected in ≤0.4% of B-cell precursors and mature B cells from patients with MM and AL. Paired single-cell transcriptomes confirmed the immature phenotype of these clonotypic cells. Driver genetic alterations were primarily detected in tumor PCs but very rarely in immature B-cell stages sequenced during treatment. Additional analysis suggested that clonotypic B cells may sporadically result in false-positive minimal residual disease assessments based on next-generation sequencing of BCR. Our results define clonotypic B cells as preneoplastic precursors of malignant PCs that are unlikely to be involved in disease progression. Significance: The cellular origin of MM and light-chain AL remains unknown. Here, we show that these tumors stem from clonotypic B cells, but driver genetic alterations are mainly contained within phenotypically aberrant PCs. These results shed light on the pathogenesis and inform on how to monitor PC neoplasms. See related commentary by Kim and Ghobrial, p. 503

MRD assessment in 26 patients with AL amyloidosis using NGF and NGS.

Whole exome sequencing (WES) samples.