T cell characteristics impact response and resistance to T cell-redirecting bispecific antibodies in multiple myeloma

PURPOSE

Bispecific antibodies (BsAbs) directed against B-cell maturation antigen (BCMA; teclistamab) or the orphan G protein-coupled receptor GPRC5D (talquetamab) induce deep and durable responses in heavily pretreated MM patients. However, mechanisms underlying primary and acquired resistance remain poorly understood.

EXPERIMENTAL DESIGN

The anti-MM activity of teclistamab and talquetamab was evaluated in bone marrow (BM) samples from MM patients. T-cell phenotype and function were assessed in BM/peripheral blood samples obtained from MM patients who were treated with these BsAbs.

RESULTS

In ex vivo killing assays with 41 BM samples from BsAb-naïve MM patients, teclistamab- and talquetamab-mediated MM lysis were strongly correlated (r=0.73, P<0.0001). Both BsAbs exhibited poor activity in samples with high regulatory T-cell (Treg) numbers and a low T-cell/MM cell-ratio. Furthermore, comprehensive phenotyping of BM samples derived from patients treated with teclistamab or talquetamab, revealed that high frequencies of PD-1+ CD4+ T-cells, CTLA4+ CD4+ T-cells, and CD38+ CD4+ T-cells were associated with primary resistance. Although this lack of response was linked to modest increase in expression of inhibitory receptors, increasing T-cell/MM cell-ratios by adding extra T-cells enhanced sensitivity to BsAbs. Further, treatment with BsAbs resulted in an increased proportion of T-cells expressing exhaustion markers (PD-1, TIGIT, and TIM-3), which was accompanied by reduced T-cell proliferative potential and cytokine secretion, as well as impaired anti-tumor efficacy in ex vivo experiments.

CONCLUSIONS

Primary resistance is characterized by a low T-cell/MM cell-ratio and Treg-driven immunosuppression, while reduced T-cell fitness due to continuous BsAb-mediated T-cell activation may contribute to development of acquired resistance.

Correlation of immune fitness with response to teclistamab in relapsed/refractory multiple myeloma in MajesTEC-1

Teclistamab, an off-the-shelf B-cell maturation antigen (BCMA) × CD3 bispecific antibody that mediates T-cell activation and subsequent lysis of BCMA-expressing myeloma cells, is approved for the treatment of patients with relapsed/refractory multiple myeloma (RRMM). As a T-cell redirection therapy, clinical outcomes with teclistamab may be influenced by patient immune fitness and tumor antigen expression. We correlated tumor characteristics and baseline immune profiles with clinical response and disease burden in patients with RRMM from the pivotal phase 1/2 MajesTEC-1 study, focusing on patients treated with 1.5 mg/kg of teclistamab (N = 165). Peripheral blood samples were collected at screening and bone marrow samples were collected at screening and cycle 3. Better clinical outcomes to teclistamab correlated with higher baseline total T-cell counts in the periphery. In addition, responders (partial response or better) had a lower proportion of immunosuppressive regulatory T cells, T cells expressing co-inhibitory receptors (CD38, PD-1, PD-1/TIM-3), and soluble BCMA, and a T-cell profile suggestive of a more cytolytic potential, compared with nonresponders. Neither frequency of baseline bone marrow BCMA expression nor BCMA receptor density were associated with clinical response to teclistamab. Improved progression-free survival was observed in patients with a lower frequency of T cells expressing exhaustion markers and immunosuppressive regulatory T cells. Overall, response to teclistamab was associated with baseline immune fitness; nonresponders had immune profiles suggestive of immune suppression and T-cell dysfunction. These findings illustrate the importance of the contribution of the immune landscape to T-cell redirection therapy response. This trial was registered at www.ClinicalTrials.gov, NCT03145181/NCT04557098.

Teclistamab impairs humoral immunity in patients with heavily pretreated myeloma: importance of immunoglobulin supplementation

ABSTRACT

Teclistamab and other B-cell maturation antigen (BCMA)-targeting bispecific antibodies (BsAbs) have substantial activity in patients with heavily pretreated multiple myeloma (MM) but are associated with a high rate of infections. BCMA is also expressed on normal plasma cells and mature B cells, which are essential for the generation of a humoral immune response. The aim of this study was to improve the understanding of the impact of BCMA-targeting BsAbs on humoral immunity. The impact of teclistamab on polyclonal immunoglobulins and B cell counts was evaluated in patients with MM who received once-weekly teclistamab 1.5 mg/kg subcutaneously. Vaccination responses were assessed in a subset of patients. Teclistamabinduced rapid depletion of peripheral blood B cells in patients with MM and eliminated normal plasma cells in ex vivo assays. In addition, teclistamab reduced the levels of polyclonal immunoglobulins (immunoglobulin G [IgG], IgA, IgE, and IgM), without recovery over time while receiving teclistamab therapy. Furthermore, response to vaccines against Streptococcus pneumoniae, Haemophilus influenzae type B, and severe acute respiratory syndrome coronavirus 2 was severely impaired in patients treated with teclistamab compared with vaccination responses observed in patients with newly diagnosed MM or relapsed/refractory MM. Intravenous immunoglobulin (IVIG) use was associated with a significantly lower risk of serious infections among patients treated with teclistamab (cumulative incidence of infections at 6 months: 5.3% with IVIG vs 54.8% with observation only [P < .001]). In conclusion, our data show severe defects in humoral immunity induced by teclistamab, the impact of which can be mitigated by the use of immunoglobulin supplementation. This trial was registered at www.ClinicalTrials.gov as #NCT04557098.

Unbiased cell surface proteomics identifies SEMA4A as an effective immunotherapy target for myeloma

The accessibility of cell surface proteins makes them tractable for targeting by cancer immunotherapy, but identifying suitable targets remains challenging. Here we describe plasma membrane profiling of primary human myeloma cells to identify an unprecedented number of cell surface proteins of a primary cancer. We used a novel approach to prioritize immunotherapy targets and identified a cell surface protein not previously implicated in myeloma, semaphorin-4A (SEMA4A). Using knock-down by short-hairpin RNA and CRISPR/nuclease-dead Cas9 (dCas9), we show that expression of SEMA4A is essential for normal myeloma cell growth in vitro, indicating that myeloma cells cannot downregulate the protein to avoid detection. We further show that SEMA4A would not be identified as a myeloma therapeutic target by standard CRISPR/Cas9 knockout screens because of exon skipping. Finally, we potently and selectively targeted SEMA4A with a novel antibody-drug conjugate in vitro and in vivo.

Plasma cell leukemia: A review of the molecular classification, diagnosis, and evidenced-based treatment

Plasma cell leukemia is a rare and aggressive plasma cell dyscrasia associated with dismal outcomes. It may arise de novo, primary plasma cell leukemia, or evolve from an antecedent diagnosis of multiple myeloma, secondary plasma cell leukemia. Despite highly effective therapeutics, survival for plasma cell leukemia patients remains poor. Molecular knowledge of plasma cell leukemia has recently expanded with use of gene expression profiling and whole exome sequencing, lending new insights into prognosis and therapeutic development. In this review, we describe the molecular knowledge, clinical characteristics, evidenced-based therapeutic approaches and treatment outcomes of plasma cell leukemia.

Abstract 839: Whole genome DNA methylation analysis of multiple myeloma identifies pervasive hypomethylation and biomarkers of survival

Multiple myeloma is a malignancy of terminally differentiated, antibody secreting B cells known as plasma cells. Normal plasma cell differentiation and cell fate are coupled to epigenetic and transcriptional reprogramming, including a proliferation-dependent global loss of DNA methylation. However, relatively little is known about the epigenetic changes that underlie myelomagenesis and how these contribute to disease etiology. To this end, we have analyzed the DNA methylome of 119 myeloma specimens from the CoMMpass study (NCT01454297) by whole genome bisulfite sequencing (WGBS) and more than 90% of these same specimens were also characterized for structural variants (long-insert whole genome sequencing) and gene expression (RNA-seq). Unsupervised hierarchical clustering grouped together specimens with t(4;14) translocations that upregulate the H3K36 dimethyltransferase NSD2 (also known as MMSET and WHSC1), which likely impacts the DNA methylation state through epigenetic cross-talk. These data also revealed a dramatic genome-wide hypomethylation where myeloma samples had a median global CpG methylation level of 41% as compared to 71% and 89% in normal plasma cells and B cells, respectively. Demethylation of the myeloma methylome occurred in large megabase domains encompassing genes that were devoid of gene expression. Conversely, DNA methylation remained mostly unchanged in the bodies of genes that were highly expressed. Although the majority of these hypomethylated domains were common across myelomas, many regions of variable methylation exist and these differences corresponded with proximal gene expression differences. These variably methylated regions were compared to PFS and OS and this identified 6,314 CpG loci where the level of DNA methylation was prognostic of outcome (P≤0.00001). These loci were clustered into discrete regions and in the majority of cases (79%), reduced DNA methylation at these loci corresponded with poor outcome. For example, several loci in the gene bodies of PRKCE, MGMT, FHIT, WWOX were prognostic of poor survival. Interestingly, myeloma t(14;16) translocations disrupt the tumor suppressor WWOX and induce the oncogene MAF. These data suggest that WWOX expression may also be lost by epigenetic mechanisms. Finally, we analyzed the DNA methylome of primary and relapsed samples for 22 patients, including multiple relapsed samples for 2 patients. These data identified genome-wide DNA methylation remodeling with a median of 1.9 million differential methylated CpGs between the newly diagnosed and relapsed specimens. These relapse differentially methylated loci coincided at the same regions in several patients and significantly overlapped loci where the DNA methylation level was prognostic of outcome. Integrative genetic, epigenetic, and transcriptional analyses for 120 myeloma samples will be presented.

Citation Format: Benjamin G. Barwick, Doris R. Powell, Daniel Penaherrera, Sheri Skerget, Jonathan J. Keats, Daniel Auclair, Sagar Lonial, Lawrence H. Boise, Paula M. Vertino. Whole genome DNA methylation analysis of multiple myeloma identifies pervasive hypomethylation and biomarkers of survival [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 839.

Identification and characterization of the zebra finch (Taeniopygia guttata) sperm proteome

Spermatozoa exhibit remarkable variability in size, shape, and performance. Our understanding of the molecular basis of this variation, however, is limited, especially in avian taxa. The zebra finch (Taeniopygia guttata) is a model organism in the study of avian sperm biology and sperm competition. Using LC-MS based proteomics, we identify and describe 494 proteins of the zebra finch sperm proteome (ZfSP). Gene ontology and associated bioinformatics analyses revealed a rich repertoire of proteins essential to sperm structure and function, including proteins linked to metabolism and energetics, as well as tubulin binding and microtubule related functions. The ZfSP also contained a number of immunity and defense proteins and proteins linked to sperm motility and sperm-egg interactions. Additionally, while most proteins in the ZfSP appear to be evolutionarily constrained, a small subset of proteins are evolving rapidly. Finally, in a comparison with the sperm proteome of the domestic chicken, we found an enrichment of proteins linked to catalytic activity and cytoskeleton related processes. As the first described passerine sperm proteome, and one of only two characterized avian sperm proteomes, the ZfSP provides a significant step towards a platform for studies of the molecular basis of sperm function and evolution in birds. SIGNIFICANCE: Using highly purified spermatozoa and LC-MS proteomics, we characterise the sperm proteome of the Zebra finch; the main model species for the avian order Passeriformes, the largest and most diverse of the avian clades. As the first described passerine sperm proteome, and one of only two reported avian sperm proteomes, these results will facilitate studies of sperm biology and mechanisms of fertilisation in passerines, as well as comparative studies of sperm evolution and reproduction across birds and other vertebrates.

Abstract 3006: Molecular characterization of baseline and serial multiple myeloma patients from the MMRF CoMMpass study

Multiple myeloma (MM) is a hematological malignancy of plasma cells accounting for ~2% of new cancer cases each year in the United States. Our understanding of MM pathogenesis has improved dramatically with the development of whole genome analysis technologies, however, to date no study has comprehensively analyzed a large cohort of MM patients. The Multiple Myeloma Research Foundation CoMMpass Study (NCT01454297) is a fully accrued observational clinical trial with 1143 newly diagnosed MM patients from sites in the United States, Canada, Spain, and Italy. Clinical parameters are collected at baseline and every three months through the eight-year observation period. Tumor samples are collected and characterized using whole genome, exome, and RNA sequencing at diagnosis and each progression event. This unique prospective study design differentiates CoMMpass from other large cancer genomics studies performed to date.

This represents the first analysis of the CoMMpass interim analysis 12 dataset including 982 of whom are molecularly characterized at baseline. Median follow-up of the cohort exceeds 2 years, and while the median OS has still not been reached, median PFS of the cohort is 36 months. We identified a median of 153 non-immunoglobulin mutations, 29 structural events, and 133 copy number (CN) events per tumor at baseline. In order to identify a set of significantly mutated genes, we applied a consensus-based approach identifying 60 genes mutated in at least 1% of the baseline cohort. Consensus clustering of the CN and gene expression profiles identified 14 and 12 distinct MM subtypes, respectively. Integration of WGS and RNA sequencing data identified 1163 cross-validated fusion transcripts. An integrated analysis of all data sources identified a series of potential gain-of-function and loss-of-function genes, from which a pathway analysis highlighted alterations in the NF-kB, Ras, DNA repair, and cell-cycle pathways.

This dataset includes serial data for 121 patients (171 specimens), 21 of whom had multiple progression events. Mutational analyses revealed that ~ 24% of mutations identified at progression were not identified at the previous timepoint. Although rarely mutated at baseline, RRBP1 was frequently mutated at relapse and may represent a novel driver of disease progression or treatment resistance in MM. In progression samples we observed a greater proportion of patients with NRAS mutations, attributable to four patients who acquire NRAS mutations and five patients with baseline KRAS mutations that shift to NRAS mutations at relapse. All patients who exhibit a KRAS to NRAS shift were bortezomib treated, suggesting this shift may represent a mechanism of resistance. This comprehensive study has identified distinct genetic subgroups with variable clinical outcome and demonstrates the value of prospective collections to identify mechanisms of progression and resistance.

Citation Format: Sheri Skerget, Austin Christofferson, Sara Nasser, Jessica Aldrich, Daniel Penaherrera, Christophe Legendre, Martin Boateng, Lori Cuyugan, Jonathan Adkins, Erica Tassone, The MMRF CoMMpass Network, Jen Yesil, Daniel Auclair, Winnie Liang, Jonathan J. Keats. Molecular characterization of baseline and serial multiple myeloma patients from the MMRF CoMMpass study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3006.

Sperm Proteome Maturation in the Mouse Epididymis

In mammals, transit through the epididymis, which involves the acquisition, loss and modification of proteins, is required to confer motility and fertilization competency to sperm. The overall dynamics of maturation is poorly understood, and a systems level understanding of the complex maturation process will provide valuable new information about changes occurring during epididymal transport. We report the proteomes of sperm collected from the caput, corpus and cauda segments of the mouse epididymis, identifying 1536, 1720 and 1234 proteins respectively. This study identified 765 proteins that are present in sperm obtained from all three segments. We identified 1766 proteins that are potentially added (732) or removed (1034) from sperm during epididymal transit. Phenotypic analyses of the caput, corpus and cauda sperm proteomes identified 60 proteins that have known sperm phenotypes when mutated, or absent from sperm. Our analysis indicates that as much as one-third of proteins with known sperm phenotypes are added to sperm during epididymal transit. GO analyses revealed that cauda sperm are enriched for specific functions including sperm-egg recognition and motility, consistent with the observation that sperm acquire motility and fertilization competency during transit through the epididymis. In addition, GO analyses revealed that the immunity protein profile of sperm changes during sperm maturation. Finally, we identified components of the 26S proteasome, the immunoproteasome, and a proteasome activator in mature sperm.

The Rhesus macaque (Macaca mulatta) sperm proteome

Mass spectrometry based proteomics has facilitated sperm composition studies in several mammalian species but no studies have been undertaken in non-human primate species. Here we report the analysis of the 1247 proteins that comprise the Rhesus macaque (Macaca mulatta) sperm proteome (termed the MacSP). Comparative analysis with previously characterized mouse and human sperm proteomes reveals substantial levels of orthology (47% and 40% respectively) and widespread overlap of functional categories based on Gene Ontology analyses. Approximately 10% of macaque sperm genes (113/1247) are significantly under-expressed in the testis as compared with other tissues, which may reflect proteins specifically acquired during epididymal maturation. Phylogenetic and genomic analyses of three MacSP ADAMs (A-Disintegrin and Metalloprotease proteins), ADAM18-, 20- and 21-like, provides empirical support for sperm genes functioning in non-human primate taxa which have been subsequently lost in the lineages leading to humans. The MacSP contains proteasome proteins of the 20S core subunit, the 19S proteasome activator complex and an alternate proteasome activator PA200, raising the possibility that proteasome activity is present in mature sperm. Robust empirical characterization of the Rhesus sperm proteome should greatly expand the possibility for targeted molecular studies of spermatogenesis and fertilization in a commonly used model species for human infertility.