CAR-modified marrow infiltrating lymphocytes efficiently target malignant plasma cells with very low antigen density

Nicolas Camviel; Davide Gambarotto; Violaine Andre; Raphael Stadelmann; Christian Sieben; Raphael Gottardo; Suliana Manley; Caroline Arber

doi:10.1016/j.ymthe.2026.02.004

CAR-modified marrow infiltrating lymphocytes efficiently target malignant plasma cells with very low antigen density

Mol Ther. 2026 Feb 6:S1525-0016(26)00090-0. doi: 10.1016/j.ymthe.2026.02.004. Online ahead of print.

Authors

Nicolas Camviel¹, Davide Gambarotto², Violaine Andre¹, Raphael Stadelmann³, Christian Sieben⁴, Raphael Gottardo⁵, Suliana Manley², Caroline Arber⁶

Affiliations

¹ Department of Oncology UNIL-CHUV, University Hospital Lausanne (CHUV) and University of Lausanne (UNIL), 1011 Lausanne, Switzerland; Ludwig Institute for Cancer Research Lausanne, 1011 Lausanne, Switzerland; Swiss Cancer Center Léman, 1011 Lausanne, Switzerland; AGORA Cancer Research Center, 1011 Lausanne, Switzerland.
² Institute of Physics, Ecole Polytechnique Fédérale Lausanne, 1024 Ecublens, Switzerland.
³ Department of Oncology UNIL-CHUV, University Hospital Lausanne (CHUV) and University of Lausanne (UNIL), 1011 Lausanne, Switzerland; Service of Hematology and Central Laboratory of Hematology, Departments of Oncology UNIL-CHUV and Laboratory Medicine and Pathology, 1011 Lausanne, Switzerland.
⁴ Institute of Physics, Ecole Polytechnique Fédérale Lausanne, 1024 Ecublens, Switzerland; Nanoscale Infection Biology Group, Helmholtz Centre for Infection Research, 38124 Braunschweig, Germany.
⁵ University Hospital Lausanne (CHUV), 1011 Lausanne, Switzerland; University of Lausanne (UNIL), 1011 Lausanne, Switzerland.
⁶ Department of Oncology UNIL-CHUV, University Hospital Lausanne (CHUV) and University of Lausanne (UNIL), 1011 Lausanne, Switzerland; Ludwig Institute for Cancer Research Lausanne, 1011 Lausanne, Switzerland; Swiss Cancer Center Léman, 1011 Lausanne, Switzerland; AGORA Cancer Research Center, 1011 Lausanne, Switzerland; Service of Hematology and Central Laboratory of Hematology, Departments of Oncology UNIL-CHUV and Laboratory Medicine and Pathology, 1011 Lausanne, Switzerland; Service of Immuno-Oncology, Department of Oncology UNIL-CHUV, University Hospital Lausanne, 1011 Lausanne, Switzerland. Electronic address: caroline.arber@unil.ch.

PMID: 41655017
DOI: 10.1016/j.ymthe.2026.02.004

Abstract

B cell maturation antigen (BCMA) is the primary target for chimeric antigen receptor (CAR)-T cell therapies and other immunotherapies in multiple myeloma (MM). Frequent relapses and the need for sequential treatments underscore the importance of alternative targets. We previously developed a dual-antigen-specific CAR recognizing both BCMA and transmembrane activator and CAML interactor (TACI). Here, we efficiently expressed this CAR in patient-derived marrow-infiltrating lymphocytes (MILs) to investigate MM cell killing via both endogenous T cell receptor (TCR) specificities and the CAR. While the patients' MIL TCRs did not recognize or kill autologous malignant plasma cells (PCs), the CAR consistently mediated efficient PC killing even at low or undetectable antigen levels by flow cytometry. Quantification of BCMA and TACI molecules on target cells by direct stochastic optical reconstruction microscopy (dSTORM) revealed that both BCMA and TACI were significantly underestimated by flow cytometry. Analysis by dSTORM allowed us to delineate the dual-antigen sensitivity of the CAR, indicating that CAR-MILs were polyfunctional and killed targets at very low antigen densities. Our findings support the further exploration of TACI as target in MM and underline the value of super-resolution microscopy in assessing antigen density thresholds for CAR-T cells.

Keywords: APRIL-CAR; CAR; CAR-T; antigen density; antigen sensitivity; chimeric antigen receptor; marrow infiltrating lymphocytes; multiple myeloma; super-resolution microscopy.