TUMOUR reactive T cells may play a decisive role in determining response to multiple myeloma immunotherapy, according to new research that identifies a transcriptional signature capable of predicting treatment outcomes and tracking immune activity over time. This research was presented at the 2025 Congress of the American Society of Hematology (ASH).
Researchers analysed bone marrow samples from 15 patients with newly diagnosed multiple myeloma using paired single cell RNA sequencing and T cell receptor sequencing. This high-resolution approach enabled detailed profiling of the T cell compartment and identified more than 100 T cell receptors with potential tumour reactivity. Although myeloma reactive clonotypes were rare, accounting for a median of 1.29% of marrow T cells, they demonstrated distinct transcriptional programmes associated with cytotoxic activity and tissue residency while lacking markers linked to terminal exhaustion.
Mapping Tumour Reactive T Cells in Multiple Myeloma
To determine the antigen targets of these tumour reactive T cells, investigators integrated human leukocyte antigen class I immunopeptidomics performed on primary CD138 positive myeloma cells with T cell receptor deorphanisation strategies. Selected T cell receptor sequences were synthesised and expressed in patient derived CD8 positive T cells to confirm antigen recognition.
Several validated receptors recognised non mutated myeloma associated antigens. These findings suggest that immune responses directed against self-antigens may contribute to disease control during early stages of multiple myeloma.
Classifier Identifies Tumour Reactive T Cells
Building on these findings, the team developed a single cell RNA sequencing based classifier known as TfiT, designed to identify the transcriptional signature of tumour reactive T cells in complex datasets. The model successfully distinguished tumour reactive cells from bystander and virus specific T cells and demonstrated strong predictive performance in multiple myeloma samples (area under the curve=0.895). The classifier was prospectively validated across nine patients with newly diagnosed disease.
Importantly, baseline levels of tumour reactive T cells identified by the classifier correlated with clinical outcomes. Among 19 patients receiving standard quadruplet therapy consisting of daratumumab, bortezomib, lenalidomide, and dexamethasone, higher frequencies of these cells were associated with achievement of a complete response (p=0.0213).
Dynamic Immune Marker for Immunotherapy Response
The researchers further assessed whether tumour reactive T cells could track response to immunotherapy in later disease stages. In a cohort of 16 patients with relapsed or refractory multiple myeloma treated with B cell maturation antigen targeting bispecific T cell engagers, the TfiT classifier again identified enrichment of tumour reactive T cells in responders at baseline.
These cells expanded during treatment, indicating active engagement of the immune response. In contrast, patients who did not respond failed to demonstrate such expansion, suggesting impaired T cell priming or mechanisms of immune escape.
Overall, the findings indicate that transcriptionally defined tumour reactive T cells represent a key determinant of response to multiple myeloma immunotherapy. Their frequency and activation state before treatment may serve as a biologically grounded biomarker to guide treatment selection and monitor anti-tumour immune responses across different therapeutic settings.
Reference
Kehl N et al. T cell fitness and tumor specificity predict immunotherapy response in multiple myeloma. Abstract 1029. ASH Congress, 6-9 December 2025.
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