Evaluation of Anti-CAR Linker mAbs for CAR T Monitoring after BiTEs/bsAbs and CAR T-Cell Pretreatment
Anja Grahnert,
Sabine Seiffert,
Kerstin Wenk,
Dominik Schmiedel,
Andreas Boldt,
Vladan Vucinic,
Maximilian Merz,
Uwe Platzbecker,
Christian Klemann,
Ulrike Koehl,
Maik Friedrich
Affiliations
Anja Grahnert
Medical Faculty, Institute of Clinical Immunology, Leipzig and University of Leipzig Medical Center, Leipzig University, 04103 Leipzig, Germany
Sabine Seiffert
Medical Faculty, Institute of Clinical Immunology, Leipzig and University of Leipzig Medical Center, Leipzig University, 04103 Leipzig, Germany
Kerstin Wenk
Medical Faculty, Institute of Clinical Immunology, Leipzig and University of Leipzig Medical Center, Leipzig University, 04103 Leipzig, Germany
Dominik Schmiedel
Fraunhofer Institute for Cell Therapy and Immunology, 04103 Leipzig, Germany
Andreas Boldt
Medical Faculty, Institute of Clinical Immunology, Leipzig and University of Leipzig Medical Center, Leipzig University, 04103 Leipzig, Germany
Vladan Vucinic
Department of Hematology and Cell Therapy, Medical Faculty, Leipzig and University of Leipzig Medical Center, Leipzig University, 04103 Leipzig, Germany
Maximilian Merz
Department of Hematology and Cell Therapy, Medical Faculty, Leipzig and University of Leipzig Medical Center, Leipzig University, 04103 Leipzig, Germany
Uwe Platzbecker
Department of Hematology and Cell Therapy, Medical Faculty, Leipzig and University of Leipzig Medical Center, Leipzig University, 04103 Leipzig, Germany
Christian Klemann
Department of Pediatric Immunology, Pediatric Rheumatology and Infectiology, Clinic and Polyclinic for Pediatric and Adolescent Medicine, Leipzig and University of Leipzig Medical Center, Leipzig University, 04103 Leipzig, Germany
Ulrike Koehl
Medical Faculty, Institute of Clinical Immunology, Leipzig and University of Leipzig Medical Center, Leipzig University, 04103 Leipzig, Germany
Maik Friedrich
Medical Faculty, Institute of Clinical Immunology, Leipzig and University of Leipzig Medical Center, Leipzig University, 04103 Leipzig, Germany
For the monitoring of chimeric antigen receptor (CAR) T-cell therapies, antigen-based CAR detection methods are usually applied. However, for each target-antigen, a separate detection system is required. Furthermore, when monitored CAR T-cells in the blood of patients treated with bispecific antibodies or T-cell engagers (bsAbs/BiTEs) recognize the same antigen, these methods produce false-positive results in clinical diagnostics. Anti-CAR-linker monoclonal antibodies (mAbs) targeting the linker sequence between the variable domains of the antigen binding CAR fragment promise a universal and unbiased CAR detection. To test this, we analyzed clinical specimens of all BCMA- and CD19-targeting CAR T-cell products currently approved for clinical use. We found a highly specific and sensitive CAR detection using anti-CAR-linker mAb in blood cells from patients treated with Ide-cel, Tisa-cel, Axi-cel, Brexu-cel, and Liso-cel. For Ide-cel and Tisa-cel, the sensitivity was significantly lower compared to that for antigen-based CAR detection assays. Strikingly, the specificity of anti-CAR linker mAb was not affected by the simultaneous presence of bispecific blinatumomab or teclistamab for Axi-cel, Brexu-cel, Liso-cel, or Ide-cel, respectively. Cilta-cel (containing a monomeric G4S-CAR linker) could not be detected by anti-CAR linker mAb. In conclusion, anti-CAR-linker mAbs are highly specific and useful for CAR T-cell monitoring but are not universally applicable.
